Chronology of the Chernobyl accident. How it all went wrong and why A. Dyatlov needed 200 MW capacity

On the night of April 26, the personnel of the 4th unit of the Chernobyl Nuclear Power Plant began to conduct coastdown tests, i.e., checks on the possibility of using the turbine inertia energy as an auxiliary energy source during a power outage at the station before switching on the backup diesel generators.

The investigation of the Chernobyl accident is an extremely complex process, complicated by the lack of a number of important documents in the public domain. In assessing the actions of the personnel, we will use the opinions of experts and government commissions, as well as the rulings of the court that took place in 1986. Technical records of the reactor condition, tied to time, are taken from the book by Nikolai Karpan "CHERNOBYL. REVENGE OF THE PEACEFUL ATOM". The author's notes are given in "oblique brackets".

Battle of reports and commissions

The first document for the IAEA, the so-called "Legasov Report" (No. 1 INSAG-1), sees the main cause of the accident in the testing program and personnel errors, but the next report of the USSR State Industrial Supervision Authority (GPAN) Commission of 1991, the head of which previously worked at the Chernobyl Nuclear Power Plant as a chief engineer (from May 1986 to 1987), in a number of episodes, relying on a formal interpretation of regulatory documents, actually refutes many of his correct conclusions, largely removing the blame from the personnel and concentrating on the shortcomings of the reactor design. There is such a concept as a conflict of interest, but in this case it was not taken into account. But the deputy chairman of the commission, V. A. Petrov, refused to sign this document, sending a letter about this:

“…the focus of the report, its logic, the scope of the issues raised do not correspond to my understanding of the topic given by the title…”, “…the actions of the staff were not assessed.”

Even now, you can find many experts on forums who will prove 100% that "the personnel acted according to regulations." In addition to the reactor's shortcomings, the documents on its management, including the regulations, were crude, unfinished, and contradictory. At the trial, a number of Chernobyl NPP employees and A. Dyatlov himself rightly point out that they did not know something.

But in addition to the regulations, NPP operators and managers must have the appropriate level of education or, as they say, a safety culture. In critical situations, they must understand which step can be fatal. And underestimating the personnel's guilt is a philosophical absurdity, essentially denying the chain of events that caused the accident. But the truth lies somewhere in the middle: the reactor had its shortcomings (see "On the Eve of the Chernobyl Accident: That Fatal RBMK Reactor").

This view is also reflected in the final report of INSAG-7 (1993):

"INSAG remains of the opinion that the critical actions of the personnel were largely erroneous. As stated in INSAG-1, the human factor should still be considered the main element among the causes of the accident. The poor quality of the operating procedures and instructions and their contradictory nature placed a heavy burden on the operating personnel, including the Chief Engineer."

Despite the negative assessment of INSAG-1 by the head of the GPAN commission, the last report to the IAEA INSAG-7 (1993) makes the following important verdict:

"This INSAG report does not cancel the INSAG-1 report, nor does it change the conclusions of that report, except as expressly stated herein."

The actions of the personnel, including legally, should be assessed based on the "frozen picture" of that time. A large group of professional experts and lawyers worked at the trial, who gave the actions of the personnel a very specific, including legal, assessment based on the realities of that time, which cannot be disavowed simply like that.

New research

The scientific works accumulated in recent times by many authors, including O. Novoselsky, K. Checherov, B. Gorbachev, A. Tarapon, N. Karpan, N. Kravchuk, reveal many details of the accident, from which it follows that the official version of the end effect (that pressing the reactor shutdown button allegedly, instead of shutting it down, "accelerated" the reactor) cannot be the main cause of the accident. The authors of INSAG-7 also have doubts: "It will probably never be possible to know for sure whether this version of the accident is true.".

The main professional evidence of this fact is presented in the article "The Legend of the Emergency Protection That Blew Up a Nuclear Reactor" (12.12.2016). Author Novoselsky O.Yu. - former head of the department of NIKIET, very well informed about the events of the accident, was a participant in the preparation of the report of the group of A.A. Abagyan. The accumulated research by the 40th anniversary of the accident (2026) requires its logical generalization.

New facts

It cannot be ruled out that if new investigations are conducted into the causes of the Chernobyl accident, classified archives of investigation materials located in the archives of the Russian investigative bodies in Moscow may "surface". INSAG-7 also understands this: "...it cannot be ruled out that this information will change in the future, as well as the perception of its significance."

Motivation and culture of personnel. For some reason, a mysterious department of the Central Committee of the CPSU was interested in conducting this experiment. It was headed by an official who had previously been deputy chief engineer for science at the Chernobyl Nuclear Power Plant. The rundown experiment "fell into the plan" of the administrative system - and this was a risk factor. According to V. Komarov (former deputy director for science at the Smolensk Nuclear Power Plant), the said official told Dyatlov: "Conduct an inspection! Either you retire or you will become the chief engineer of the new Chernobyl Nuclear Power Plant-2." [He] meant the new Chernobyl Nuclear Power Plant with the 5th and 6th blocks, which was then under construction. And this episode even made it into the textbook of V. L. Gurachevsky ("Introduction to Nuclear Power Engineering", Rosatom library).

In turn, the head of the tests, A. Dyatlov, put pressure on the personnel, who disagreed with him more than once, and this was also the reason for the accident. The unit was stopped for a technical stop, and everyone wanted to achieve success at any cost now and immediately, because the next opportunity could only present itself in a year. There were rumors that the personnel were promised large bonuses, and the experiment was needed for someone's dissertation (which is doubtful). Official documents do not cover this part of the tragedy in any way.

According to INSAG-1, the main motive of the personnel's behavior was the desire to complete the tests as quickly as possible or, more precisely, to bring them to an end at any cost. Another factor in the accident was the low nuclear safety culture at the Chernobyl Nuclear Power Plant, the best in the USSR in all respects, but not the best in safety discipline. As follows from the court materials, the personnel often worked in "extreme modes" in pursuit of economic indicators. And then came the moment when, having driven the reactor into an uncontrollable state, they simply did not have time to shut down the reactor in time, which, in fact, A. Dyatlov himself admits.

Features of the study

In addition to the development of the picture of the actions and motivation of the personnel, this note shows the special role of several factors that were not fully reflected in any of the official reports: detailed coverage of the events of the day before - 25.04.1986, conducting vibration tests and identifying the fact of lagging behind; motivation for going to 200 MW and combining the experiments of coasting and vibration tests. The main conclusion of the study is that the process of the accident at the Chernobyl Nuclear Power Plant must be investigated further, using the full range of classified documents available in the archives of the investigative bodies of Moscow. Let's move on to the chronology, but first let's introduce several terms.

The reactor is controlled by inserting or removing the control and protection system (CPS) rods. The CPS rods are designed for automatic power control, rapid reactor shutdown, and regulation of energy release fields.

The ORM (operating reactivity margin), expressed in rods (abbreviated as RR), shows what margin the operator has to increase the power, as well as the maximum positive reactivity that can be introduced into the reactor by the control rods. The ORM is the actual effective number of rods immersed in the zone.

The fate of the reactor was decided by the events of the day before. Preparation for the experiment and its interruption: why everything went wrong right away

Although the events of the previous day are not covered in sufficient detail, it was at this time that many things happened at the unit that later determined the tragic outcome of the events. The experiment was planned for Friday, April 25, 1986, during the day, during Igor Ivanovich Kazachkov's shift, which worked from 8 a.m. to 16 p.m. On this day, the fourth unit of the Chernobyl Nuclear Power Plant was scheduled to be shut down for scheduled maintenance. But everything immediately went differently.

Preparations for the experiment—reducing the reactor power—began during Akimov’s previous shift (Akimov A.F.’s shift from 0:8 a.m. to XNUMX:XNUMX a.m.).

At 1:00 a.m., the command was given for the preparatory stage - reducing the reactor power from the nominal level of 3100 to 700-1000 MW (thermal).

1h 00m - Unit with capacity N(t) = 3100 MW, N(3) = 930 MW.

1h 05m - Start of unloading of the power unit: the operating reactivity margin (ORM) is equal to 31 st. RR.

Simultaneously with the coastdown tests, there was another program - conducting vibration tests of the turbogenerator at idle, which is not listed in the documents (see below for more details). From the memoirs of the block shift supervisor V. I. Borets, it follows that the TG-8 bearing had a serious defect and, in order to eliminate it, representatives of the Kharkov plant were invited with a unique set of imported equipment for measuring vibration at that time in order to balance the turbine and reduce vibration.

Vibration Test Delay: When Even the Little Things Matter

The staff fell behind schedule for vibration testing before the scheduled maintenance; they performed vibration testing of TG-7 and turned it off, but did not perform vibration testing of TG-8.

A. Dyatlov himself speaks about the reasons in court:

"There were two issues: the TC was not ready to conduct vibration tests on the TG-8. The brackets on which the sensors are installed were not welded to the TG-8. The TC manager, Khoronzhuk, and the ZGIS for repairs, Alekseev, were responsible for this. When the TG-8 was ready for testing, the dispatcher forbade us from executing the program with changing the load on the TG, as required by the program..."

GPAN information:

"From 04:13 to 12:36
"sequential measurement of the characteristics of the control systems and vibration characteristics of TG-7,8 at a constant thermal power of the reactor of 1500 MW."
"This operation [vibration measurement] was not envisaged by the working program for testing the TG-8 rundown mode. The vibration measurement of TG-7 and TG-8 with different loads on them was envisaged by another program, which the personnel had already partially completed on April 25, 1986, with alternate redistribution of turbogenerator loads and a constant thermal power of the reactor of 1500-1600 MW."

As we will see below, if the vibration tests had been performed separately from the coastdown, the accident might not have happened. But sometimes even small things have a huge price.

As is known, a decrease in the reactor power is accompanied by its xenon poisoning and a decrease in the operational reactivity margin (ORM, i.e. the effective number of rods immersed in the zone).

Xenon poisoning, or iodine pit, is a condition of a reactor after its shutdown or power reduction, associated with the accumulation of short-lived xenon isotope 135Xe (half-life 9,14 hours), formed after the radioactive decay of the iodine isotope 135I (half-life 6,57 hours), which has a high ability to absorb neutrons, which leads to the inhibition of the fission reaction. When the reactor operates at constant power, xenon constantly decays due to the absorption of neutrons. With a significant decrease in power or shutdown of the reactor, the neutron flux in the reactor decreases and xenon accumulates, which inhibits the fission reaction. In order for the process to stop, it is necessary to maintain the reactor for 1-2 days for the decay of iodine and xenon.

Block unloading: OZR drop below permissible

The reduction in power to 50% of the nominal value resulted in the beginning of the process of xenon poisoning of the reactor.

During the power reduction of the unit at 7:10 a.m., the ORM according to the calculated data reached the value of 13,2 rods, i.e. it became lower than the permissible value of 16 rods. According to the regulations, in this case the reactor had to be shut down, and there would have been no accident!

3 h 47 m - thermal power of the reactor is 1600 MW.
4 hours 14 minutes – TG-7 anti-tank missiles were knocked out.
4 h 20 min — VTG-7 switched off, speed pickup from 5th control panel.
4 h 48 m - N(T) of the reactor is 1600 MW.
5 h 40 m — statistical characteristics of TG-7 were taken.
6 h 58 min — synchronization and connection to the TG-7 network, redistribution of the load between TG-7 and TG-8.
7:10 a.m. — failure of the Skala central control system. The ORM was calculated without taking into account the immersion of 12 AR rods (the reactivity margin on which is never less than 2 RR1 rods) and was shown as equal to 13,2 RR rods. /As Karpan writes, the real value of the ORM at this time was about 18 RR rods, which is questionable./
8:00 a.m. — unit status: reactor power 1520 MW, N(3) = 380/50 MW. OZR — not less than 16 st. RR. /According to court testimony — 13,2 st./

According to the GPAN report (1991), the operation of the reactor facility with an ORM of 15 rods or less in the period from 07:00 to 13:30 on 25.04.86 was a violation of the Regulations, but the personnel did not shut down the reactor due to the revealed unreliability [citing unreliability] of the work of the PRIZMA calculation program. N. Karpan also writes about this.

But in the court and GPAN materials this fact is recognized as reality. From the testimony of Rogozhkin, the station shift supervisor:

"I would like to start with 25.04.86, when the request for a shutdown of Unit 4 with a coastdown was authorized (we worked from 0 to 8:00)... The unit was unloaded, but Akimov and I had doubts that the reactivity margin would not fall below 15 RR rods. By 8:00, this is what happened, it became 13,2 rods. I noted this at the selector operational meeting at 8:00. Frolovsky asked again: "How much, how much?", to which Fomin said: "We will discuss this issue separately...

According to the regulations, we should shut down the reactor. But the unit was about to be shut down, so we reported this to the management and that was it. We decided to do without extremes, since this parameter was not listed as the main one in the instructions and regulations."

There is one interesting point here. According to the calculated characteristics (see the graph), the reactor should have lost about 14-15 st., i.e. reached the level of 31-15=16, but in reality it turned out lower. Rogozhkin states that they had some very good reasons to assume that the ORM would fall below the 15 rods allowed by the regulations. We see that Florovsky was surprised by the figure of 13,2. Consequently, this episode requires further investigation.

Source: N.Karpan, CHERNOBYL REVENGE OF THE PEACEFUL ATOM, chapter 6.

From the court materials, questions to Fomin:

"Rogozhkin's defense attorney: If you had learned from the NSS on the morning of April 25 that the reactivity reserve was less than 15 rods, what would you have done? Fomin: I would have stopped the reactor."

From Fomin's testimony:

"Prosecutor: Fomin, did you give Dyatlov the order to work with a reactivity reserve of less than 15 RR rods? Fomin: I did not give such an order."

It is clear from the testimony that everyone is shifting responsibility to each other. These events very well demonstrate the attitude of the personnel to the regulations, which is confirmed by the testimony of I. I. Kazachkov, who worked as the head of the day shift of the 25th unit on April 1986, 4: "I will say this: we repeatedly had less than the permissible number of rods - and nothing ...", "... none of us imagined that this was fraught with a nuclear accident. We knew that we should not do this, but we did not think ..." Yes, at the Chernobyl Nuclear Power Plant they constantly worked in violation of the regulations - but the situation was saved, most likely, by the fact that this happened at higher capacities than those fateful 200 MW that A. Dyatlov chose.

How did Kyivenergo's call affect the fate of the reactor?

It is generally accepted (see below) that the reactor poisoning began after Kyivenergo called to prohibit power reduction. As can be seen, in fact it began in the morning.

Then a completely unexpected event occurs. The process of reducing the power (unloading the unit) was unexpectedly interrupted at the level of 50% of the reactor's design capacity at the request of the Kyivenergo dispatcher on 25.04.1986 at 14:00, who prohibited reducing the power due to problems at the Tripolskaya GRES (according to another version - the South-Ukrainian NPP), and was continued only at 23:10. At the same time, the SAOR - the emergency reactor cooling system - was switched off and blocked.

14:00 - SAOR is disconnected from the MPC circuit. Start-up and
connection of diesel generators 2DG-4 and 2DG-5 to the busbars for their own needs.
15h 10m - Reactor power 1500 MW, OZR = 16.8 st. RR, Kg = 1,47;
23:10 - by order of the NSB, the reactor power reduction began.
24:00 - reduction completed, N(T) = 760 MW, N(a) TT-8 = 200 MW, ORZ = 24 st. RR.
As is known, operation at 50% power level is also accompanied by xenon poisoning of the reactor and a decrease in the operational reactivity margin ORM (i.e. the effective number of rods immersed in the zone).

Graph of power dynamics and ORM. Source

If we compare the theoretical depoisoning schedule (see above) at 50% power, we will get a subsidence depth of minus 3–4 (actually minus 5) after 22 hours, which is close to the actual. Dmitriev also writes about the almost complete depoisoning of the reactor. That is, operation at 50% power almost depoisoned, but did not poison the reactor.

But if we take the difference between the beginning of the power reduction process, when (ORM) is equal to 31 rods, and its end (24,0 rods), then as a result of poisoning the reactor lost about 7 rods or about 22% of the initial ORM level.

The main consequence of the “postponement” of the tests: the experiment went to the weakest shift of the 4th block

The postponement of the experiment due to the dispatcher's call had another catastrophic consequence. According to G. Medvedev, a professional nuclear engineer who participated in the construction of the Chernobyl Nuclear Power Plant as the deputy chief engineer of the plant, the shift of Yuri Tregub, which handed over the shift to Alexander Akimov at 24:00 on 25.04.1986, was more experienced and was unlikely to have allowed the accident. The unit's shift supervisor, Alexander Akimov, had never worked as a SIUR (SIUR is a senior reactor control engineer). SIUR Toptunov L.F.: 26 years old, 8 months of experience as a SIUR.

According to the testimony of the chief engineer of the Chernobyl Nuclear Power Plant Fomin, "SIUR Toptunov was not very experienced, did not have the skills to work in transient modes," Akimov "was an inexperienced, young specialist." Some specialists believe that when the tests were postponed, the shift should have been reinforced, but paradoxically, this was not done. Only the experienced physicist Yu. Tregub (the head of the unit shift), who worked on the previous shift, decided to stay and watch the experiment.

But that's not all. There was an order from the director of the Chernobyl Nuclear Power Plant that a representative of the Nuclear Safety Department (NSD) had to be present during such tests. And he, perhaps, would not have allowed such abuse of the nuclear reactor. To the prosecutor's question, "Why wasn't NSD on duty on April 26...?", N. Karpan, deputy chief engineer, answered the following: "... Anatoly Chernyshev (a former experienced SIUR) was supposed to be on duty on April 25... But the shutdown of the unit was postponed to April 26, and Chernyshev, who called into work on the afternoon of April 25, was told that the tests were over and he was free to go."

Reactor poisoning hypothesis at 50% power

This episode requires further investigation, but there is an opinion that after the dispatcher’s call, xenon poisoning developed, which predetermined all subsequent fatal events, including the further “self-shutdown” of the reactor.

As V. Komarov (former deputy director for science at the Smolensk NPP, participant in the accident investigation) believes, commenting on the 50% power delay: “This… absolutely should not have been done!”

But the telex from KyivEnergo was duplicated by a telephone call from the Central Committee of the CPSU... And... the order was carried out...

According to Deputy Minister of Energy G.A. Shasharin:

"The delay of the experiment... significantly reduced the reactivity margin, reducing the number of control rods immersed in the active zone due to additional poisoning of the reactor (iodine pit). All this created conditions for a pre-accident state."

This circumstance was of an external nature, the management could adjust the program. However, all this required additional time, which the group did not have.

Also from Karpan's book there is evidence from Elshin M.A. (NS CTAI), confirming this hypothesis: "During the process of reducing the power, the SIUR did not hold the unit at power and "dropped" it. The device was heavily "poisoned", and the SIUR did not hold it..."

As the author of the textbook, V. L. Gurachevsky, writes (“Introduction to Nuclear Energy”, Rosatom library):

"According to another version, the night shift of A. F. Akimov accepted the reactor while it was running, during a rapid decrease in power from 1 MW in the presence of xenon poisoning. The senior reactor control engineer who came on duty, L. F. Toptunov, did not have time to understand the difficult current situation and simply could not stabilize the power at the required level..."

According to V. Dmitriev (VNIIAES), further “…“self-shutdown of the reactor”, if it did take place, occurred not “due to deep poisoning”, but as a result of other effects in reactivity, forming a positive feedback between power and reactivity.”

According to the State Panorama of Russia:

"The process of unloading the power unit, which began at 01:06 on 25.04.86, until the process of continuing unloading below 720 MW (thermal) at one o'clock in the morning on 26.04.86, did not affect the occurrence of the accident, although during the specified period of time two violations of the technological regulations were committed: operation with the ORM below the permissible level and shutdown of the emergency cooling system."

The above facts indicate that it is necessary to conduct a further investigation of the events of 25.04.1986 in order to identify the reasons that could subsequently have caused the reactor to shut down and determined the prerequisites for the possibility of an accident. Perhaps we do not know something.

Studying the program
Shift of Yu.Yu. Tregub from 16 p.m. to 24 p.m.
22:45 - reactor power 1600 MW, ORZ = 26,0 st. RR.
23:10 — By order of the NSB, the reactor power reduction has begun. /The dispatcher lifts the ban. The personnel begin further reduction of the reactor power to 760 MW thermal according to the test program./
24:00 — reduction completed, N(t) = 760 MW, N(a) TT-8 = 200 MW, ORZ = 24 st. RR.

The second reduction by almost 50% took 50 minutes (the first 8 hours).

April 26, 1986 Shift No. 5, NSB - Akimov A.F.
/On April 26, 1986, at 00:00, shift No. 5, NSB — Akimov A. F., came on duty. The shift workers did not have sufficient experience, and their qualifications were lower than those of the previous shift of Tregub. According to the personnel, they familiarized themselves with the testing program "on the move"/.

The key question of the accident: why did A. Dyatlov need 200 MW capacity?

00 h 00 min — start of shift — N(T) = 760 MW, N(a) TT-8 = 200 MW,
OZR = 24 st. RR.
00:05:4 — 1PK-XNUMX switched to recirculation.
00:05:200 - by order of Dyatlov A.S., the reactor power began to be reduced to the level of its own needs (XNUMX MW thermal).

It would seem: what difference does it make at what power to conduct tests? But there are powers where the reactor operates stably, and a power of 200 MW is only the initial stage of the reactor's operation to raise the power to the operating level. And it turns out that it operated extremely unstably in this state!

N. Karpan and Yu. Tregub indicate that Dyatlov, instead of conducting an experiment at a power of 700 MW (thermal), as indicated in the test program, gives an indication to reduce the power to 200 MW (40 MW electrical).

As a member of the IXBT forum writes (IXBT forum):

"Around midnight the dispatcher gave the go-ahead. It seemed that smoothly and confidently we reached the required 0 MW at 10:700, and carried out the coasting according to our program...
If they had started the run-out at 0:10, when they confidently reached the 700 MW required by the program, everything would have gone fine for them (like in 85, only with oscilloscopes working as they should) and would have been shut down just as fine.
But they are lagging behind in vibration testing of TG-8. For some reason they went below 700 MW, from where at 0:30 they dropped almost to zero. Let's assume that this is a dip above the MKU [minimum controlled power level] - i.e. we need to climb back out of the hole according to paragraph 6.7. TR, although there was already an argument about the "MKU" here..."

Why was the decision made to operate at 200 MW?

1. Perhaps 200 MW was needed to legally carry out (to bypass the requirements of the main Regulation on the operation of this protection) the shutdown of the protection for shutting down the reactor by closing the SRK of both turbines in accordance with the “Regulations for switching keys and pads ...”, which, according to this document, is switched off at a power of less than 100 MW electrical.

As A. Dyatlov himself writes: “According to the Regulations, the specified protection is withdrawn at a capacity of less than 100 MW of electrical power, we had 40 MW. And, therefore, there is no violation…”.

2. Dyatlov allegedly needed to turn off the protection in order to repeat the experiment (in case of failure), although competent experts, including those who advised the author, acknowledged that under these conditions its repetition would have been absolutely impossible.

3. Therefore, the 200 MW mystery may be caused by the hypothesis of the need to reduce the power to conduct vibration tests. But we know nothing about the details of this program, except for Davletbaev's testimony (see below). Fomin allegedly saw it during the investigation. The author of the textbook, including V. L. Gurachevsky, writes about this possibility ("Introduction to Nuclear Power Engineering", Rosatom library):

"00:05 - an event occurred that seriously disrupted the testing process. The reactor's power continued to decline. The reasons why this happened have not yet been established, including due to closed access to certain documents describing the reactor's operation that night.

According to one version, the fact that parallel to the turbogenerator rundown test program, it was planned to measure turbine vibrations at idle speed played a role. To maintain the turbogenerator at idle speed, the power of 720 MW achieved by that time and envisaged by the rundown program was too high. Therefore, it began to be reduced further, to the level of own needs. The testimony of some witnesses says that this was done on the orders of A.S. Dyatlov.

Dyatlov, both in his testimony at the trial and in his book of memoirs, claims that he did not give such a command…”

It is clear that reducing the power further, which would have caused another poisoning of the reactor, was an extremely risky step that could have ended with its shutdown, which is what happened. If this is so, then the combination of vibration tests with the coastdown test, as the court later established (see below), was one of the most important causes of the accident.

O. Novoselsky, who is well informed about the events of the accident, also writes about this:

"To conduct the first tests of TG-8 at idle, it was necessary to reduce the steam capacity, i.e. the reactor power. During this reduction, the operator failed to maintain the power, and the reactor was shut down. Was it possible to increase the power?... By removing almost all the absorber rods from the xenon-poisoned core, it was possible to increase the power to 160 MW, and measure the vibrations of TG-8. By 1.03.00 on April 26, the power was increased to 200 MW... Here, the nuclear reactor was treated like a heating boiler: the power was reduced to almost zero, the vibrations were measured, and now we will increase it to the program value of 700 MW. No one remembered about any xenon poisoning or reactivity reserves..."

The same hypothesis is considered by V. Dmitriev (VNIIAES):

“To maintain the turbo generator at idle speed and measure turbine vibrations, the 720 MW power achieved at 00:05 was too high, and it was apparently reduced further (to the level of in-house needs).”

To conduct the first tests at idle speed of the TG-8, it was necessary to reduce the reactor power.

The reduction of power to 200 MW, in turn, triggered a new process of xenon poisoning. During this reduction, the operator failed to maintain the power, and the reactor was shut down.

Dyatlov at the trial:

“I am accused of giving Akimov the order to reduce the reactor power from 760 MW (as it was at 24:00) to 200 MW, as a result of which poisoning processes began and the reactivity reserve dropped below 15 RR rods.”

From the testimony of Lyutov (ZGIS for Science) at the trial: "Expert... Was the reactivity course calculated to reduce the reactor power from 1600 to 200 MW? Lyutov: It looks like the schedule was not very well thought out. Expert: What is wrong with 200 MW compared to 700 MW? Lyutov: At this power level, the steam effect is more pronounced."

A. Kryat (Head of the Nuclear Physics Laboratory of the Chernobyl Nuclear Power Plant) also speaks about additional poisoning of the reactor, although not directly:

"I made a remark that I would not agree with 300-200 thermal MW. We need 1000-700. The fact is that a power below 700 MW leads to a loss of reactivity reserve. In this mode, the "Prism" program, that is, the system that allows operators to monitor the physical state of the reactor, also works poorly. I objected at the meeting with Dyatlov. I said that the device loses control at a power of 200 MW..."

The shift supervisor of the 4th unit of the Chernobyl Nuclear Power Plant V. I. Borets, who witnessed the fact that at low power the RBMK reactor at the Leningrad Nuclear Power Plant behaved unpredictably and unstable. And the Chernobyl Nuclear Power Plant management knew this.

Consequently, the motivation for the “departure” of 200 MW does not correspond to official documents and requires thorough further investigation.

The first turbine TG-7 was stopped earlier. The second TG-8 was in operation.

The reports of the State Nuclear Academy and subsequent ones, and the participants of the forums who echo them, also say that, supposedly, it was never said anywhere that it was impossible to work at this capacity.

GPAN 1991:

"The decision to conduct TG-8 rundown tests at a reactor power level of ≈200 MW is a deviation from the work program. However, the design, regulatory and operational documents did not prohibit operation of the unit at the specified power level. There was no safe operating limit in the form of a minimum permitted level of thermal power of the reactor before the Chernobyl accident... Moreover, Chapter 11 of the TR (clause 11.4) required personnel to reduce the reactor power to a level determined by the load of the unit's own needs (200-300 MW thermal), after automatic unloading according to the standard AZ-3 mode or remotely in the event of disturbances in the power system (frequency deviations). The reactor operating time at the minimum controlled power level was not limited... The commission believes that the accusations against the operating personnel for operating the unit at a power level of less than 700 MW are unfounded"

Formally yes, but nowhere was it defined that it was operational. As follows quite clearly from the Regulations, the power of 200 MW is only one of the initial stages of increasing the power until the reactor reaches the operational level with a time of not less than 1,5 hours. The operating modes of 200 MW and reduction to 200 MW were not defined. Although formally there is no reference to this in the Regulations, in fact it was clear that 200 MW is intermediate (see Table 5.1).

IXBT Forum:

"The regulations do not require a standstill at a thermal capacity of 200 MW. And a standstill after the rise stage is only required for a further increase in capacity."

The State Penitentiary Service acknowledges violations:

“…the personnel allowed deviations from the test program (see sections 4.7.5, 4.7.6 of this report).”

INSAG-7:

"The most damning thing is that unapproved changes to the test program were immediately and deliberately introduced on site, even though it was known that the installation was not at all in the condition in which it should have been during the tests."

The previous tests in 1985 were conducted with the reactor shut down at 50% of the nominal power, the tests in 1986 were conducted without shutting down the reactor at 200 MW, i.e. 6% of the nominal power, which was not used in practice (!) for operating the reactor.

Why was a capacity of over 700 MW needed? According to Deputy Minister of Energy G. A. Shasharin:

"At this power level [700 - 1000 MW], the feedwater flow rate ensures the thermohydraulic stability of the main circulation circuit when four circulation pumps are operating. During the transition period (power reduction), this ensures a sufficient reactivity reserve (the number of control rods immersed in the reactor core)."

According to Fomin's testimony in court:

"I consider the violations of the program points to be the main cause of the accident. First of all, the reduction of the reactor capacity to 200 MW."
“Prosecutor: Who, in your opinion, is the main culprit of the accident?
Fomin: - Dyatlov, Akimov, who allowed deviations from the program."
“A. Kryat: We published a manual for training senior reactor control engineers (SIUR)… There, in this manual, reactivity issues were widely covered.
Defendant A. Kovalenko: - Why didn’t the nuclear safety department include provisions on the danger of operating a reactor with a small reactivity margin in the regulations, instructions, etc.?
A. Kryat: - This is, apparently, a miscalculation of all science. Today it has already been written that if there are less than 30 rods in the active zone, the reactor goes into a nuclear-hazardous state. But the device has such negative qualities that sooner or later this would have happened"

Dyatlov at the trial:

"I am accused of giving Akimov the order to reduce the reactor power from 760 MW (as it was at 24:00) to 200 MW, as a result of which poisoning processes began and the reactivity reserve dropped below 15 RR rods. I did not give such an order to Akimov. There is no such thing in Akimov's testimony. It is in Tregub's testimony. I believe that we can clarify this issue during the trial."

And more:

"Expert: You interpret the documents (regulations, etc.) in your own way. You considered it possible to stop (after reducing capacity) at 200 MW instead of 700. Why?
Dyatlov: Yes. As the head of the tests, I had the right to change the conditions somewhat, while remaining within the regulatory limits. And 200 MW is the regulatory capacity.
Expert: But it is probably better to control a 700 MW reactor than a XNUMX MW one. What do you think?
Dyatlov: 200 MW is the regulatory capacity. We controlled it using all the standard systems."

Here is a hypothesis put forward by one of the IXBT forum participants:

“[Dyatlov]... concocted the text of the coastdown program in such a way that a relatively legal loophole appeared in the program to go to a power of 200 MW, where the technical regulations formally allowed the AZ-5 machine to be turned off when both turbines were running down (with a number of reservations, but still formally legal).”

That is, if Dyatlov had initially planned to conduct a rundown on an unshutdown reactor (with what motivation?), then he did his best to legally include such a possibility in the testing program. And he even concocted the program formally with someone else's hands (a specialist from Dontekhenergo). And he slipped it to his immediate supervisor for approval. Fomin definitely gave in here by approving this, but there is much that is unclear, what kind of dialogue took place between them, eyewitness accounts differ.

From Fomin's testimony:

"Expert: Why was the program developed by the Dontekhenergo team engineer Metlenko? (Dyatlov smiles.) Fomin: Of course, it would be better if the program was developed by a technologist."

From the testimony of Metlenko (team engineer of Dontekhenergo):

“Assistant Prosecutor: Do you agree that 200 MW of power was needed?

Metlenko: Enough for our own needs. We needed 30-50 MW of electric power, and the technologists required 600-700 MW for the reactor.

Assistant Prosecutor: During the preliminary investigation, you said that you yourself asked for a capacity of 200 MW and that the technologists responded that this could only be done at the last moment, and until then, work at 700-1000 MW. Metlenko is silent."

Metlenko is silent about his request to go to a capacity of 200 MW, which, as some experts point out, was perhaps done to conduct vibration tests.

According to the court's conclusion:

“Contrary to paragraph 2.1 of the testing program, Dyatlov ordered that they be conducted with the reactor operating at a power of 200 MW, instead of the 700-1000 MW required for safe operation.”

Obviously, one of the reasons for the further "collapse" of the reactor is the power reduction. It would have been reasonable not to deviate from the test program and conduct them at a power of 700...1000 MW with the reactor shut down, then the accident would simply not have happened.

THE FIRST (FATAL) TRAGIC MISTAKE – CONDUCTING AN EXPERIMENT AT A POWER OF 200 MW.

Продолжение следует ...

The author would be grateful for any comments, as well as for the exchange of information on the description of the events of the Chernobyl accident.

Links:
Technical aspects of the accident at the 4th power unit of the Chernobyl NPP, O. Yu. Novoselsky, Yu. M. Cherkashov, K. P. Checherov
N.V. Karpan, CHERNOBYL REVENGE OF THE PEACEFUL ATOM, chapter 4
HISTORY OF NUCLEAR ENERGY IN THE SOVIET UNION AND RUSSIA ISSUE 4
CHERNOBYL ACCIDENT: SUPPLEMENT TO INSAG-1: INSAG-7
O. Novoselsky, The legend of the emergency defense that blew up a nuclear reactor, 12 / 12 / 2016
Chernobyl: KOMAROV'S TESTIMONY
Information on the Chernobyl Accident and Its Consequences, Prepared for the IAEA, Report No. 1 (INSAG-1)
How the Chernobyl explosion was prepared. (Memoirs of V. I. Borets.)
Technical aspects of the accident at the 4th power unit of the Chernobyl NPP, O. Yu. Novoselsky, Yu. M. Cherkashov, K.P. Checherov
On the causes and circumstances of the accident at Unit 4 of the Chernobyl Nuclear Power Plant on April 26, 1986, Report of the USSR State Industrial Supervision Commission,
Chernobyl: KOMAROV'S TESTIMONY
N.V. Karpan, CHERNOBYL REVENGE OF THE PEACEFUL ATOM
Grigory Medvedev. Chernobyl notebook, M Izvestia 1989
Ryzhikov L.Kh. So why did the reactor of the IV block of the Chernobyl NPP explode?
Shasharin G. Chernobyl tragedy // Novy mir, No. 9, 1991, p. 164.
Gurachevsky V. L. Introduction to Nuclear Power Engineering
Victor Dmitriev, Chernobyl disaster. Its causes are known
How the Chernobyl explosion was prepared
TECHNOLOGICAL REGULATIONS for the operation of power units 3 and 4 of the Chernobyl NPP with RBMK-1000 1E-S-11 reactors

Comments

[Monster_Fat]

There are several films on YouTube about the investigation of the Chernobyl disaster, and they provide facts and evidence that are not mentioned (removed) in the official investigation results. There are even quite logical versions explaining nothing other than sabotage (related to the Kura station). Watch it, it's very informative.

[Free]

Yes, there was no sabotage, that reactor did not comply with a number of then-current guidelines and had design flaws that caused that disaster. The Chernobyl accident, in general, repeated the 1975 Leningrad NPP accident (an attempt to raise the power of a poisoned reactor with a small ORM). But in 1975, the steam release system from the reactor space coped, everything ended with a burnout of several channels, unlike in 1986, when steam from depressurized channels got into the graphite masonry, lifted the top cover under pressure, tearing off all the other channels, dehydrating them - then an explosion.

[belost79]

Why did the protection system work at the Leningrad NPP, but not at the Chernobyl NPP in a similar situation? It is thanks to a similar incident without serious consequences in Sosnovy Bor that the version of sabotage exists.

[Alexander Odintsov]

That's right. The protection system at the Leningrad NPP worked perfectly because no one turned it off. In 1986, the most important thing was that the protection for stopping both turbine generators was turned off, which led to the accident. According to Yu. A. Potemkin, former deputy head of the GVP (Main Military Prosecutor's Office) of the USSR: "... they turned off both turbines with the reactor running. This is already madness, to put it bluntly. This led to the explosion."

[Free]

The protections worked normally in 1975 and 1986. But at the Leningrad Nuclear Power Plant, the steam release system, designed to rupture 2-3 channels, managed to release pressure from the reactor space, but at the Chernobyl Nuclear Power Plant, when, according to estimates, 5-6 channels were depressurized, it did not.
Regarding the shutdown of turbines, or rather the supply of steam to them, what are the issues with this? Otherwise, how do you order the unit to be stopped?

[Alexander Odintsov]

During the previous experiments, the protection was not switched off and the reactor was shut down, there was no accident. The chief engineer of the Chernobyl Nuclear Power Plant, Nikolai Fomin, who was responsible for safety at the Chernobyl Nuclear Power Plant and who became the main initiator of the notorious "experiment", openly admits that the shutdown of this protection was one of the main causes of the accident:
“Prosecutor - How, in your opinion, what could have prevented the accident?
Fomin - If there had been no withdrawal of AZ-5 from the closure of the SRC, the block would have remained intact ... In 1982, 84 and 85, when the program was being implemented, the AZ-5 signal to the reactor came from the closure of the SRC on the turbine. And in 1986, changes were made in this part. Now it is clear to me that the program should have been coordinated with specialists. There was no need to leave the device on power if all the TGs are standing.

[Free]

I read the technology for testing 84g, there was no connection there between the closing of the SRK and the automatic operation of the AZ-5. Those protections that were displayed could be switched off at that power and feedwater consumption according to that regulation. The most important ones - when the maximum power and the rate of its increase were not switched off and it was impossible to switch them off from the control panel. In general, that shift, understanding that the reactor was difficult to control and capricious, was still confident in the reliability of its emergency automation.
And I agree that the run-down program should have been assigned to specialists, specifically NIKIET and Hydroproject, and carried out under their control. Otherwise, they pushed it onto operation and withdrew.

[Alexander Odintsov]

I read the technology for testing in 84, and there was no connection between the closing of the SRK and the automatic activation of the AZ-5.

Once again, in earlier tests, the reactor was simply shut down and that was enough.

[Doctor]

Fomin - If there had been no withdrawal of AZ-5 from the closure of the SRC, the block would have remained intact ... In 1982, 84 and 85, when the program was being implemented, the AZ-5 signal to the reactor came from the closure of the SRC on the turbine. And in 1986, changes were made in this part. Now it is clear to me that the program should have been coordinated with specialists. There was no need to leave the device on power if all the TGs are standing.

At WHAT capacity? 200 MW thermal? That's nothing, 6,25% of nominal. When they closed the valves, the reactor was SMOLDERING, not burning.

[Alexander Odintsov]

The reactor was at low power, but it was at this power that it was most unstable, plus the protection was turned off. Perhaps the unit personnel did not fully appreciate the risks of closing the SRK on the remaining turbine, although the more experienced of them should have understood everything. Perhaps from their experience it followed that when the reactor was operating at 200 MW, the pressure increase would be slow. Steam could be discharged into the condensers through the device for bleeding excess steam (when the pressure increases) BRU-K.
The main steam drain in a working reactor is through the turbine. In case of turbine shutdown, the drain is blocked, but steam generation by the reactor continues, which leads to pressure growth. Protection for both TGs was created to prevent a pressure surge in the primary circuit associated with the shutdown of the turbines, when they stop consuming steam.
As a result, the blocking of protection to block both turbogenerators under specific conditions of the accident development (see below, a sharp decrease in the feedwater level, slowdown in operation and failure of the main circulation pump) was one of the factors in the development of the accident.

[Eule]

Quote: Alexander Odintsov

Here the nuclear reactor was treated like a heating boiler:

Here is the key phrase!
The so-called rundown experiment is essentially turning off the water supply to the reactor to see how quickly it explodes.
In the book "My Atomic Age", I don't remember the author, I think Zhuravlev, a nuclear scientist with a huge experience, wrote directly that Kurchatov ordered to hang a poster in the control room "The reactor cannot be left without water - it will explode!"
It is also fundamental that for thermal power plants where gas or fuel oil is burned, if there is no water supply, the temperature of the heat exchanger and the boiler itself cannot exceed the combustion temperature of the fuel, i.e. less than the melting point of iron. But the reactor, left without water, will heat up until its active zone evaporates, which the party callers simply did not know.
That is, the very essence of the experiment contradicted the physics of the reactor’s operation and control.
Eh, it would be better if Aeroflot was transferred to the subordinate directorate of suburban transportation of the Ministry of Railways! What? Both sell tickets and carry passengers.

[Doctor]

Why did the protection system work at the Leningrad NPP, but not at the Chernobyl NPP in a similar situation? It is thanks to a similar incident without serious consequences in Sosnovy Bor that the version of sabotage exists.

Because the staff there VIOLATED THE REGULATIONS and was being really stupid.

First, they confused which TG to turn off and turned off the working one instead of the one that needed repair!

And when the reactor went down, they pulled out almost all the control rods, trying to start it up. It started to squeal, and they shut it down again, this time urgently with the AZ button. And here, just like in Chernobyl, instead of a decrease, there was a SURGE in power.

But because, unlike the Chernobyl Nuclear Power Plant, the fuel there was fresher (they weren’t going to shut down the Leningrad Nuclear Power Plant reactor, they were shutting down the turbine), it didn’t explode all at once, but only partially melted.

But the moon was shining. The whole Serebryany Bor was glowing.

[Pokrovskij1959]

At full AZ-1 or 5 ALL RBMKs had a power surge. SIURs and SIURts paid attention to this effect and wrote comments. But no one above paid serious attention, they wrote it off as a defect of the power measurement system. This effect was not properly investigated.

[Alexander Odintsov]

The question is not simple, many points are completely unclear. The accidents of 1975 and 1986, despite all the similarities, had different causes and different consequences. Another researcher of the Chernobyl accident, Ukrainian nuclear physicist Nikolai Kravchuk, refers to the fact that after reading his work, a certain academician said: "Nikolai Vasilyevich, I got the impression that this was a brilliantly planned crime!" And then he asserts: "But isn't it? I believe that the main "architects" of the Chernobyl disaster were those who wanted the collapse of the Union! The reactor explosion was planned in advance and carried out under the leadership of Gorbachev's Central Committee of the CPSU, and the blame was carefully placed on the plant personnel."

[Free]

There is no point in looking for a conspiracy where everything is perfectly explained by the technical design of the reactor, its flaws, inadequate regulations and the errors of the operating personnel that follow from this. There have been enough accidents at channel reactors, especially industrial ones for producing isotopes. But it is one thing to "goat" the fuel channels on the A-1, "Annushka", and another thing to burn it out on the 3000-megawatt monster RBMK.

[Alexey Lantukh]

There is no point in looking for a conspiracy where everything is perfectly explained by the technical design of the reactor, its flaws, inadequate regulations and the errors of the operating personnel that follow from this.

Moreover, the experimenters first approached the Kursk Nuclear Power Plant with the aim of conducting the experiment there, but the chief engineer there, a professional nuclear physicist with vast experience, categorically refused to conduct the experiment, citing the high risk of an accident. By the way, a monument to him was erected in Kurchatov at the request of the residents.

[Free]

Actually, these were tests of the standard safety system of the RBMK units, envisaged by the project. The station was obliged to implement the coasting mode at the 2nd stage units. Yes, they tried to refuse, but Hydroproject insisted that the decisions must be implemented. By the way, the tests themselves were conducted before that. The first time, it was necessary to modify the generator excitation system, the second time it was not possible to take the necessary parameters, they decided to conduct them a third time. By the way, the tests themselves were successful. In general, they were not the direct cause of the accident, the same accident at the Leningrad NPP in 1975 occurred without coasting tests, but followed a similar scenario.

[Alexander Odintsov]

The idea of ​​coasting was extremely dubious. There was no analogue anywhere in the world. The coasting mode of the TG even managed to be included in the publication of a textbook for electrical engineering universities on the course "Electrical Part of Power Plants" / Edited by S. V. Usov., 1977.
The most critical analysis of this idea was given by V. Dmitriev (VNIIAES): "The time during which the RDES was switched on... does not exceed 1 min. And during this time, the RCP pumps water by inertia, due to the mechanical energy stored in a massive flywheel installed for this case on the shaft of each RCP." According to technical specifications, the run-out time of the RCP rotor to a complete stop is 2-5 min.
The flywheel energy of the main circulating pump is sufficient for their uninterrupted operation until the RDES is turned on, but it is technically difficult to provide them with power due to the turbine runout:

"...the generator is included in the station's electrical system by a number of electrical connections that ensure uninterrupted power supply for its own needs and automatic protection of both the generator itself and the external networks for which it operates in normal mode. This requires appropriate switching in the electrical circuit when organizing the run-down, which actually negates the self-protection effect."

According to V. Legasov, this experiment should have been conducted not at the station, but "...on a special stand built by the turbine designer." And it was necessary to follow the path of "reducing the time of commissioning and reaching the required parameters of backup diesel generators", it would have been possible to "replace the diesel generators of the Chernobyl station with those that would make everything normal and ... the entire procedure of these tests and checks would have become simply unnecessary." In fact, after the accident, this is what they did (!) - they began to use generators with a shorter start-up time.
And finally, the entire experimental design was quite obviously in contradiction (!) with the actions of the electrical automation (the automatic protection system of the power system (PS) of the unit), which simply blocked the electrical equipment of the unit when the turbogenerator speed dropped below the permissible level! This consideration was voiced by the most knowledgeable researcher of the accident, Konstantin Checherov, which was also established in the NIKIET study. So maybe the problem in the early tests was not only in the excitation system?

[Eule]

Quote: Freeal

but Hydroproject insisted that the decisions must be implemented.

They'd be better off studying the hydrodynamics of toilets, honestly. For hydroelectric power plants, experiments with run-out, i.e., stopping the water supply, do not threaten anything at all.

[Doctor]

Moreover, the experimenters first approached the Kursk Nuclear Power Plant with the aim of conducting the experiment there, but the chief engineer there, a professional nuclear physicist with vast experience, categorically refused to conduct the experiment, citing the high risk of an accident. By the way, a monument to him was erected in Kurchatov at the request of the residents.

The bike. I talked to the Kursk nuclear scientists. Tom Nikolaev refused because according to his calculations the inertia power was not enough, so there was no point in making a fuss.

The idea that it was “dangerous” was an afterthought by the director of the Kursk Nuclear Power Plant, Voskresensky.

This experiment has already been carried out 4 times, if not more.

[Alexey Lantukh]

The idea that it was “dangerous” was an afterthought by the director of the Kursk Nuclear Power Plant, Voskresensky.

Yes, there are a lot of rumors and tales and even conspiracy theories. You don't know what to believe. I won't go into technical details because I don't have that knowledge. It's interesting that one of our dosimetrists ran into dosimetrists from the Smolensk NPP who were on a business trip to the Chernobyl NPP. They told me that the experimenters had apparently come to them at Smolensk and were refused. And this was told when I was also at the Chernobyl NPP, i.e. in 1987. And I read about Nikolaev quite recently, when I was reading about the Kursk NPP and the city of Kurchatov.

[Pokrovskij1959]

This experiment was intended to improve the safety of the reactor in transient conditions.

[Alexander Odintsov]

There is no need to search. You just need to analyze everything honestly.

One of the witnesses to the accident, who worked at the Chernobyl Nuclear Power Plant on April 26, Yuri Andreyev, president of the Chernobyl Union of Ukraine, who supervised the change of operators of the second block shield of the Chernobyl Nuclear Power Plant, in an interview with the BBC concludes that the testing program itself led to the accident:
"The reason for the entire accident is in the testing program. Many years after the accident, somewhere around 2000, I superimposed the testing program on the obvious version of the accident causes and saw that if the testing program is followed literally, from the first to the last point, then it is impossible to avoid the accident..."

[Free]

And what could have happened during the tests according to the program, with a planned reduction in power and shutdown without an iodine pit, taking into account that the rundown began simultaneously with the shutdown of the reactor?

[Alexander Odintsov]

As before, nothing :)) There would have been no accident

[Eule]

Quote: Freeal

what could have happened during the tests according to the program

Water supply stops, the active zone overheats and BAM!

[Chief Officer Lom]

Quote: Freeal

no, there was no sabotage, that reactor did not comply with a number of the then governing documents and had design flaws

There may not have been any sabotage, but the reactor's normal operation was completely safe, and those who want to hide the fact that "Here, the nuclear reactor was treated like a heating boiler" cite design flaws. The personnel, who could barely remember the order in which to press the buttons, turned off the safety systems and conducted two experiments simultaneously, not coordinated with each other, in abnormal modes, and is the design to blame? The stupid and greedy officials are to blame, who, before the disaster, achieved the transfer of the NPP from the Ministry of Atomic Energy to the Ministry of Energy, which quickly placed its personnel in prestigious positions (hello, KievEnergo), having them undergo short-term courses in NPP management. Naturally, they did not want to publicly admit this stupid act and return the nuclear power plant back to the nuclear scientists, but they could not leave with their families to Miami at that time, so after the disaster a separate Ministry of Atomic Energy was created (July 2, 21).

[Free]

The 1975 accident occurred in a routine mode, developing from a standard state; immediately before the 1986 accident, not a single parameter on the control panel signaled the start of an emergency process! Regarding the withdrawal of protections, I wrote in this thread. Regarding the transfer of the NPP from the jurisdiction of Minatom (maybe Sredmash?) to the Ministry of Energy... read about the number of accidents at Sredmash enterprises, they have everything in full swing there, including the accident at the Leningrad NPP in 1975 (a rehearsal for Chernobyl), the accident at Mayak, numerous accidents at industrial channel reactors - the ancestors of RBMK, etc.

[Chief Officer Lom]

Not everyone knows what was hidden behind the name of the Ministry of Medium Machine Building, MinAtom is clearer. There are no industrial enterprises where accidents are completely excluded, but the fact that the Chernobyl accident was caused by the blatant arrogance of personnel who easily violated instructions and at the same time had practically no knowledge of the processes in the reactor is beyond doubt. As well as the fact that with the transfer from Sredmash to the Ministry of Energy, the personnel of the nuclear power plant began to be replaced by people who had the minimum necessary knowledge, which was sufficient only for everyday work.

[Free]

There is no point in blaming people so indiscriminately. A thorough check of the Chernobyl NPP personnel after the accident showed that they were quite competent for the positions they held. People who knew Dyatlov rated his professionalism very highly, although they noted his difficult character. Of course, blaming everything on that shift was the easiest solution, which is what they did. At the same time, they began modernizing all Chernobyl-type reactors in a timely manner to prevent similar events in the future, and they did it in less than a year. That is, the designers knew the real reasons very well, and it was not like "the operator pressed the wrong button." By the way, according to the instructions that existed at that time, it was forbidden to design and operate reactors whose safety was ensured not by automation, but only by following instructions and rules.

[Chief Officer Lom]

Quote: Freeal

Dyatlov's professionalism was highly rated by people who knew him.

You are plucking out those assessments that confirm your version. Other specialists assessed Dyatlov as a person incompetent in the issues that he had to resolve in his new workplace. Which, by the way, is confirmed by his answers to questions given in the article, from which it follows that he did not understand what processes were taking place in the reactor and did not know what options for their deviations from the norm were possible, tried to evade responsibility, denying the commands given to him and hiding behind instructions, the provisions of which he himself violated. Naturally, the instructions did not contain exhaustive instructions on what to do in situations caused by multiple violations of the instructions for routine work with the reactor.

[Alexander Odintsov]

During the accident, everyone behaved like heroes, no doubt about it. But the indictment at the 1986 trial also stated that there had been accidents at the Chernobyl nuclear power plant before, but they were often not analyzed or even registered. It was noted that the management of the nuclear power plant did not provide the necessary professional training for the personnel servicing the reactors, and did not properly control their discipline at work. As Academician V. Legasov writes: “…the mistakes made by the operators… are, in themselves, monstrous: the behavior of the plant management is difficult to explain; the punishment of the culprits… is correct; because the actions did not meet regulatory requirements and showed a discrepancy with the job requirements of those people who acted in this situation… this is the fault of the officials.”
According to one of the fathers of nuclear energy in the USSR, academician A. Aleksandrov: "Twelve times (!) the experimental regulations violate our operating instructions for the nuclear power plant. You wouldn't dream of such a thing. The nuclear power plant worked for eleven hours with the SAOR [author's note: emergency reactor cooling system] turned off!"

[Pokrovskij1959]

I wonder what kind of NPP operating instructions this is? There was no such instruction from the Alexandrov Institute. The Regulations allowed the SAOR to be switched off for a certain time and under certain conditions.

[Alexander Odintsov]

You are wrong, there are no questions about the SAOR. According to the GPAN report (1991), the shutdown of the SAOR was a violation of the Regulations, but did not affect the occurrence and development of the accident, since no signals for the automatic activation of the SAOR were recorded.

[PavelT]

Is this true? They wrote it right there in the report: "the shutdown of the SAOR was a violation of the Regulations, but did not affect the occurrence and development of the accident"???
I especially like the motivation and excuse: "since no signals for automatic activation of the SAOR were recorded." - i.e. if we continue to run the reactor at 200-700 MW back and forth and further for days with the SAOR turned off, then if there are still no signals for automatic switching on, then everything is fine???
Are they serious?

[Free]

Disabling the SAOR was not a violation. Moreover, since the SAOR was triggered at MPa, and at the MPa signal the run-down should have started, this system had to be disabled. The SAOR is an extreme measure of cooling the zone in case of a rupture of the KMPC pipelines, and there is a high probability that these tons of cold water will damage the channels.

[PavelT]

Following this strange logic "SAOR is an extreme measure for cooling the zone in case of a rupture of the KMPC pipelines" it turns out that it is better not to include the SAOR automation at all, and maybe not even to do it when building a nuclear power plant. Just install a toggle switch/button on the remote control Launch of the SAOR - the operators on shift are smart, they will figure out for themselves when to press this button!

[Free]

What's wrong with the automation? Especially since the rupture of the KMPC is such a case that the only thing left is to prevent the active zone from melting, there's no time to worry about whether the channels will warp from the cold water or not.

[PavelT]

Judging by your comments above "Disabling the SAOR was not a violation / this system had to be disabled"It's precisely this automation that you don't like!
I perceive the situation the other way around: if the NPP has officially installed automatic control systems for the reactor’s emergency response system, then this automatic control system must be kept on for the maximum amount of time, and not rely on the reaction, knowledge, and adequacy of the shift operators.
Because the bending/damage of the reactor channels from the water from the SAOR is in any case BETTER than a reactor explosion, a blown-off lid, a breach of containment and radioactive contamination.

[Free]

The shutdown of the SAOR did not affect the development and course of the emergency situation. This is also from the IAEA report. Since the rundown was part of the localization of the MPA, it was necessary to turn off our own for testing.

[Alexander Odintsov]

Watch this film FOURTH BLOCK, Investigators' Version, http://veteran-sled.ru/page/fourth-block-films.html

[WIS]

Quote: Alexander Odintsov

Watch this movie THE FOURTH BLOCK

Thank you, but can't we do without YouTube?

[carpenter]

Quote: Monster_Fat

There are several films on YouTube about the investigation into the Chernobyl disaster

A lot has been written and filmed, but we won’t know the whole truth for another 50 years.

[stels_07]

The system failed, starting with Dyatlov, who shouldn't have been there, because that's not what he was doing in the Far East, the design organizations didn't prepare the rules for the experiment properly, the regional council asked to move the atomic experiment, and even during the liquidation, it wasn't possible to get accurate data right away. And only the exploits of the liquidators copied the problem.

[solar]

The system crashed, starting...

...from the system itself. Dyatlov was under great psychological pressure to conduct the tests for the holiday - there was such a systematic practice of "Danish" achievements, timed to coincide with certain dates. If Dyatlov could have simply written down in the report that such and such experiments could not be conducted for such and such reasons (and there were plenty of them), he would have done so. But refusing to conduct an experiment timed to coincide with the "date" threatened him with problems and put great psychological pressure on him.

[Free]

By the way, those involved have no questions about Dyatlov's competence, as well as about the rest of the operational personnel of that shift. Although yes, the general safety culture was not at its best, but this is the case throughout the industry. Especially in comparison with the present time.

[Alexander Odintsov]

Grigory Medvedev interviewed A. Dyatlov in 1973 and was against hiring him to work in the reactor shop, but he was saved by the incomprehensible patronage of the director of the Chernobyl Nuclear Power Plant, V. Bryukhanov: “According to the questionnaire, he worked as the head of the physics laboratory at one of the enterprises in the Far East, where ... he was involved in small ship nuclear installations ... He never worked at a nuclear power plant. He does not know the thermal schemes of the station or uranium-graphite reactors ... It was not easy to listen to him, his character was difficult.
I reported to Bryukhanov that Dyatlov could not be accepted to the post of head of the reactor department. It will be difficult for him to manage operators not only by virtue of character traits (he obviously did not possess the art of communication), but also from the experience of previous work: a pure physicist, he does not know atomic technology.
Bryukhanov ... said he would think about it. A day later, an order was issued to appoint Dyatlov as deputy head of the reactor shop ... The forecast regarding Dyatlov was confirmed: clumsy, slow-witted, difficult and conflicted with people ...
After my departure, Bryukhanov began to move Dyatlov, he became the head of the reactor shop, and then the deputy chief engineer for the operation of the second stage of the nuclear power plant.

[Free]

Grigory Medvedev, the author of "The Chernobyl Notebook"? I beg your pardon, but this book is a disgusting collection of incompetence, distortions and lies. For many, it created a distorted view of the problem at the time.

[Alexander Odintsov]

Interesting, something new. There are inaccuracies. But the book is too well-known.

"The Chernobyl Notebook" by G. U. Medvedev is a competent and fearlessly truthful story about the tragedy that happened more than three years ago, which continues to worry millions of people... The author shows the behavior and role of numerous participants in the drama, living, real
people with their shortcomings and virtues, doubts, weaknesses, delusions and heroism next to an atomic monster getting out of control. One cannot read about this without the deepest emotion... Everything that concerns the Chernobyl disaster, its causes and consequences, must become public knowledge. The full, undisguised truth is needed. Academician A. SAKHAROV.

[Free]

Those involved in the accident, such as those who worked at RBMK, have a different opinion about his book.

[Alexander Odintsov]

"The Chernobyl Notebook" is one of the most well-known and at the same time popular works about the Chernobyl accident. The book has been translated into several languages, its author is a nuclear specialist, worked for many years at different stations, including as a shift supervisor at the Chernobyl Nuclear Power Plant in the 70s. That is, there are no questions about his competence. "The Chernobyl Notebook" describes the accident not only from the inside, on behalf of specific people, it is first and foremost the path BEFORE Chernobyl. A combination of factors and prerequisites that led our country to April 26. The Soviet Union, as a direct participant in the tragedy, played an important role in this.

[Free]

Medvedev did not work as part of the plant's operational staff and it is clear that he neither read the regulations nor knows the power units themselves. It seems that he was involved in the supply of materials and equipment to the plant under construction.

[Pokrovskij1959]

It is obvious that this book was written by an amateur.

[Alexander Odintsov]

You are wrong. This is an excellent analysis. Grigory Medvedev is a nuclear engineer and writer. He participated in the construction of the Chernobyl Nuclear Power Plant as the deputy chief engineer of the station.
"The Chernobyl Notebook" is one of the most famous books about the Chernobyl disaster, reprinted many times and translated into many languages. It is a first-hand account based on documents and numerous eyewitness accounts interviewed by the author, who was sent to Chernobyl immediately after the accident.
The reader will learn about the causes of the accident, its development, including a minute-by-minute analysis of the events that took place, as well as the heroism of the people who eliminated its consequences. The book won awards from the Los Angeles Times and the New York Times, and was also used in the creation of documentaries and feature films.
"A must-read book by a Soviet physicist... Plus, Grigory Medvedev was on the scene. A great blend of historical narrative and scientific approach." Craig Mazin, screenwriter of the HBO miniseries Chernobyl.

[Doctor]

Grigory Medvedev in 1973 conducted an interview with A. Dyatlov and was against his employment in the reactor shop, but he was saved by the incomprehensible patronage of the Chernobyl director V. Bryukhanov: “According to the questionnaire, it appeared that he worked as the head of a physical laboratory at one of the enterprises of the Far East, where ... he was engaged in small ship nuclear installations ... He never worked at a nuclear power plant. He does not know the thermal diagrams of the station and uranium-graphite reactors ... It was not easy to listen to him, his character was felt heavy.
I reported to Bryukhanov that Dyatlov could not be accepted to the post of head of the reactor department. It will be difficult for him to manage operators not only by virtue of character traits (he obviously did not possess the art of communication), but also from the experience of previous work: a pure physicist, he does not know atomic technology.
Bryukhanov ... said he would think about it. A day later, an order was issued to appoint Dyatlov as deputy head of the reactor shop ... The forecast regarding Dyatlov was confirmed: clumsy, slow-witted, difficult and conflicted with people ...
After my departure, Bryukhanov began to move Dyatlov, he became the head of the reactor shop, and then the deputy chief engineer for the operation of the second stage of the nuclear power plant.

And did Medvedev check Bryukhanov himself? A guy who, before Chernobyl, only worked at a power plant.

And did Medvedev check himself?
He didn’t work at a nuclear power plant either, and the research VK-50 doesn’t count.

[Aviator_]

meant the new Chernobyl nuclear power plant with units 5 and 6, which was then under construction.

What other construction of the 5th unit at this time? In 1986, the 5th unit of the Chernobyl Nuclear Power Plant was already operating, our current head of the security service was then called up from the reserves and sent to deactivate the 5th unit. Then, until the order from the West, the 5th unit worked to provide for the Sarcophagus. This crazy rumor spoils the impression of a good article.

[Alexander Odintsov]

And you haven't seen There's a whole construction site left there Chernobyl reactors No. 5 and 6 are unfinished reactors, part of the third-generation Chernobyl nuclear power plant. They were designed as RBMK-1000 with a capacity of about 1000 megawatts each. Construction began on July 1, 1981, and was partially completed by the time of the Chernobyl disaster on April 26, 1986.

[Aviator_]

And you haven't seen There's a whole construction site left there Chernobyl reactors No. 5

I didn't see it. Our head of security not only saw it, but also deactivated it with the soldiers. Perhaps there was no official commissioning of the 5th block, but the fact that it then provided electricity to the sarcophagus for 10 years is indisputable.

[Macsen_wledig]

Quote: Aviator_

Our head of security not only saw it, but also deactivated it with the soldiers.

It is quite possible that it was deactivated: the third stage of the Chernobyl Nuclear Power Plant was at a high level of readiness and could well have been completed (though much later than planned).

Quote: Aviator_

Perhaps there was no official commissioning of the 5th block, but the fact that it provided electricity to the sarcophagus for 10 years is indisputable.

Ask yourself a simple question: do you really think that in the era of universal information technology no one would ever mention that one of the 3rd stage units was launched and worked for quite a long time.
Don't you think that the 100 MW (a conventional ceiling figure), necessary to maintain the operation of the sarcophagus, would be easier to "pinch off" from the operating 1,2, 3 and XNUMX power units.
Or ask yourself a simple question: what is so “terrible” under the sarcophagus that could require the launch of an entire RBMK-1000...

[Aviator_]

Ask yourself a simple question: do you really think that in the era of universal information technology no one would ever mention that one of the 3rd stage units was launched and worked for quite a long time.

There was information about this, as well as the fact that the European Union demanded that it be stopped.

Or ask yourself a simple question: what is so “scary” under the sarcophagus?

I am not a nuclear scientist, I know this section only at the level of a general physics course at a technical university. Are you a professional nuclear scientist?

[Macsen_wledig]

Quote: Aviator_

There was information about this, as well as the fact that the European Union demanded that it be stopped.

Can you provide links to sources?

Quote: Aviator_

Are you a professional nuclear scientist?

No.
But due to the nature of my work, for some time I had to maintain objects in a mode of, let’s say, minimal life support.
Therefore, I doubt that 1000 MW of electrical power was needed for the "life" of the sarcophagus...

[Aviator_]

Can you provide links to sources?

Have you been taking down all the messages on radio and TV for decades?

[Macsen_wledig]

Quote: Aviator_

Can you provide links to sources?

Have you been taking down all the messages on radio and TV for decades?

OK...
Got it, accepted it: another "tale from the crypt".

[Alexey Lantukh]

Perhaps you mean the 3rd power unit, which was shut down, and then in 1987-88 it was deactivated and repaired for mechanisms common with the 4th. Then it was launched and worked for another 12 years.

[Aviator_]

It was Unit 5 that was deactivated. In 1986. I remember that at the request of our "European friends" it was shut down later, 10 years later. There was no need to repair anything there, all that was needed was to collect everything in a bucket of water with a wet rag. That's the kind of deactivation we had.

[Alexey Lantukh]

Why am I talking about the third? I was in the partisans for six months from 1987, though in the headquarters. Our construction battalion, raised from the Moscow Military District reserves, was engaged in repairs on the buildings of the 3rd power unit. Specifically, repair and construction work on the territory of the 3rd power unit. That is, something like this: dosimetrists measure, cleaning takes place, they measure again, sometimes they even had to knock down the plaster and re-plaster, rate-setters closed orders, calculated wages taking into account the zones, but paid only upon dismissal to avoid drunkenness. It took a long time to revive this unit.

[Aviator_]

Well, the third one was also put in order, as much as it was possible. But my friend (he is an electronics engineer, he started, like me, in the 20th department, I was even his deputy in the Komsomol for some time), so he worked at the 5th block with conscripts. And it was about the 5th block that there was a message, that at first it provided energy to the sarcophagus, and then it was turned off.

[Alexander Odintsov]

Look here https://dzen.ru/a/XmAuifUHoRgl4rOg?ysclid=mbm9hz69gs330083774 The construction was far from the main station as I remember

[Macsen_wledig]

Quote: Alexander Odintsov

The construction was far from the main station, as I remember.

Here is the third line.

[Pokrovskij1959]

Block 5 never worked!

[ANB]

I am following the entire series of articles about Chernobyl. And my conclusions, which I made back in 1989 after talking to the LNPP specialists, do not change (actually, these are their conclusions).
Although RBMK is not considered the safest, the Chernobyl Nuclear Power Plant employees did everything they could to blow up the unit.
They would have blown up an ordinary thermal power station with this approach.
IMHO - I consider references to the fact that something is not prohibited in the regulations to be excuses. For example, nowhere in the traffic rules and the car operating instructions is it written that you cannot accelerate to 90 km/h and drive the car into a concrete wall. But drivers do not do this. But the Chernobyl NPP personnel did.
Well, and additional intervention from the local leadership of the Communist Party of Ukraine is clearly evident.

[Free]

In 1975, at the Leningrad Nuclear Power Plant, the operators from Sredmash were half a step short of an accident on the scale of Chernobyl. They were saved by the fact that the zone contained, on average, fresher fuel with less burnup, and that they lowered the control rods not all at once, but in groups, which reduced the so-called "end effect", localizing it in some channels. Nevertheless, a severe radiation accident occurred, the result of which was the irradiation of personnel and liquidators, contamination of the unit and the adjacent territory. Incidentally, it happened according to a similar scenario to the 1986 accident.

[Chief Officer Lom]

Quote: Freeal

In 1975, at the Leningrad Nuclear Power Plant, operators from Sredmash

The date of transfer of the NPP to the Ministry of Energy is September 29, 1966. About the identity of the accident at the Leningrad NPP and the accident at the Chernobyl NPP - where did the firewood come from? Not from the fund for writing the "true" history of Ukraine? All the circumstances of nuclear accidents in the USSR are presumptive, a detailed public investigation of Chernobyl is an exception for an obvious reason.

[Free]

In 1966, a decision was made to start designing the station, there was no talk of transferring it anywhere, all power units were built by Sredmash, the ministry also recruited personnel from its own enterprises. Regarding the identity of the accidents - read about them, there is enough information on the Internet, the emergency process arose and developed according to similar scenarios (which is not surprising, the prophets of the same type of reactors are similar). Regarding the "true history of Ukraine" - here, alas, I did not understand what this is about.

[Chief Officer Lom]

Quote: Freeal

In 1966, a decision was made to begin designing the station.

The date of transfer of the NPP to the Ministry of Energy is September 29, 1966. If it is not clear, this refers to the transfer of all NPPs in the country. Sredmash was still left as the designer of the country's NPPs, which also led to complications in operation due to increased bureaucratic red tape, disagreements between ministries, and simply different education (what seemed obvious to some and did not require separate instructions could be completely unrecognized by others)

[Pokrovskij1959]

The Leningrad Nuclear Power Plant and the Ingushetia Nuclear Power Plant were under the jurisdiction of Sredmash until 1987, when they were transferred to the jurisdiction of Minatom, a new ministry.

[Doctor]

In 1975, at the Leningrad Nuclear Power Plant, the operators from Sredmash were half a step short of an accident on the scale of Chernobyl. They were saved by the fact that the zone contained, on average, fresher fuel with less burnup, and that they lowered the control rods not all at once, but in groups, which reduced the so-called "end effect", localizing it in some channels. Nevertheless, a severe radiation accident occurred, the result of which was the irradiation of personnel and liquidators, contamination of the unit and the adjacent territory. Incidentally, it happened according to a similar scenario to the 1986 accident.

I gave you pluses everywhere. You're on point!
The previous article by NIKIET people was a political officer's article, like the staff is just stupid, they promised to quickly write a sequel, but after the comments they took more than a month to prepare.
Now there is more technology, but everything is still grey.
Let's look at it below...

[Doctor]

I am following the entire series of articles about Chernobyl. And my conclusions, which I made back in 1989 after talking to the LNPP specialists, do not change (actually, these are their conclusions).
Although RBMK is not considered the safest, the Chernobyl Nuclear Power Plant employees did everything they could to blow up the unit.
They would have blown up an ordinary thermal power station with this approach.
IMHO - I consider references to the fact that something is not prohibited in the regulations to be excuses. For example, nowhere in the traffic rules and the car operating instructions is it written that you cannot accelerate to 90 km/h and drive the car into a concrete wall. But drivers do not do this. But the Chernobyl NPP personnel did.
Well, and additional intervention from the local leadership of the Communist Party of Ukraine is clearly evident.

You're tracking poorly. No one has accelerated to 90 km into a wall, they just drove a car, pressed the clutch, put it in neutral and counted how long the car would move by inertia.

And then they pressed the brake, expecting (like all normal people) that the car would stop.
And instead she went nuts, damn it!

You know, "not the safest car."

[gridasov]

This is not only a chronicle of events, but also a chronicle of subjective assessments of the processes that led to the catastrophe. But the question is different: have effective methods of assessing events been created in understanding their information processes in accordance with reality? And judging by the latest events, nothing has changed.

[Doctor]

This is not only a chronicle of events, but also a chronicle of subjective assessments of the processes that led to the catastrophe. But the question is different: have effective methods of assessing events been created in understanding their information processes in accordance with reality? And judging by the latest events, nothing has changed.

This is just an article from the reactor developers. Of course, they are making excuses for themselves, like everything was ok with the reactor, the staff is stupid.

However, it is not the number of changes made to the RBMK after the accident that indicates that they assessed the events correctly.

[october]

However, it is not the number of changes made to the RBMK after the accident that indicates that they assessed the events correctly.

This is a normal life cycle of any complex product.
I'm on the developers' side.

[Doctor]

This is a normal life cycle of any complex product.
I'm on the developers' side.

Well, it's normal)). Soyuz-11 was descending slowly and the ventilation valve opened a little earlier. Nothing to worry about, a normal life cycle of any complex product, it was later improved.

[Nikolai]

The country was being taken out of its comfort zone. The war in Afghanistan. Prohibition. An accident at the stations. They got their way. Yakovlev himself admitted - his hands were covered in blood up to the elbows.

[VENOM]

Why does the author link to ixbt.com? The site is good, but its subject matter is electronics, software and all that. It doesn't seem to have any direct relation to the nuclear industry. I read a bit of this discussion from five years ago, but how can you link to an anonymous commentator from a non-core site? I could have written something there just the same.

[Doctor]

Why does the author link to ixbt.com? The site is good, but its subject matter is electronics, software and all that. It doesn't seem to have any direct relation to the nuclear industry. I read a bit of this discussion from five years ago, but how can you link to an anonymous commentator from a non-core site? I could have written something there just the same.

The author is really throwing shade at the fence.

classified archives of investigation materials located in the archives of the investigative bodies of the Russian Federation in Moscow

a mysterious department of the Central Committee of the CPSU, which was headed by an official who had previously been deputy chief engineer for science at the Chernobyl Nuclear Power Plant

There were rumors that the staff were promised large bonuses, and the experiment was needed for someone's dissertation (which is doubtful).

Just a little further and we'll get to the aliens)).

[Alexander Odintsov]

You are wrong. Go there, there is a long-standing professional party there for at least 15 years.

[Uma palata]

And who specifically developed this experimental program for this reactor? Who approved it and who gave the order to act exactly according to the program?

[Doctor]

And who specifically developed this experimental program for this reactor? Who approved it and who gave the order to act exactly according to the program?

The initiator is the General Designer of the NPP. He wrote a special letter (Letter from NIKIET outgoing No. 040-9253 dated 24.11.76), justifying this by the requirement to guarantee continuous circulation of the coolant and guaranteed cooling of the active zone to remove residual heat, which, as it seemed to the chief designer, could be accomplished by stopping the steam supply to the turbine, using its inertia.

That is, in essence, he wanted to introduce another protection, in case of a power outage. Someone would fire a cruise missile at a nuclear power plant, and the lights would go out there...

Then scientists got involved, developed a methodology, etc.

The responsibility for implementation was placed on the power engineers, Soyuzatomenergo in particular, and they have already obliged the stations.
At the Chernobyl Nuclear Power Plant, the experiment was first conducted in 1982, only at the 3rd unit, then in 1984 and in 1985.
In the future, based on the results of the experiments, it was planned to implement it systematically at the stations of the 2nd stage.

The executors and approvers are the employees of the Chernobyl Nuclear Power Plant.
Here is the 1985 program, approved by Chief Engineer Fomin.

[Pokrovskij1959]

Where is the rest of the program text?

[Doctor]

The first document for the IAEA, the so-called "Legasov Report" (No. 1 INSAG-1), sees the main cause of the accident in the testing program and personnel errors, but the next report of the USSR State Industrial Supervision Authority (GPAN) in 1991, the head of which had previously worked at the Chernobyl Nuclear Power Plant as chief engineer (from May 1986 to 1987), in a number of episodes, relying on a formal interpretation of regulatory documents, actually refutes many of his correct conclusions, largely removing blame from the personnel and concentrating on the shortcomings of the reactor design. There is such a concept as a conflict of interest, but in this case it was not taken into account.

Conflict of interest...
After all, two people can play this game)). If in the first case the commission consisted of reactor developers, then in the second case it consisted of operators.
All is fair.

And what does "formal interpretation of regulatory documents" mean?
The author suggests approaching the Regulations informally and creatively?

[PavelT]

This very conflict of interest was shown IN ADVANCE (before the Chernobyl disaster) in the little-known Soviet film of 1979 "Commission of Investigation" (directed by Vladimir Bortko)
https://kino.rambler.ru/movies/50634956-kakoy-film-predskazal-katastrofu-v-chernobyle-za-sem-let-do-tragedii/
It was about the Kola Nuclear Power Plant, the film had a good cast - Oleg Efremov, Vladimir Retsepter, Irina Miroshnichenko, Lyubov Virolainen, Mikhail Boyarsky.

I watched this film. The situation is exactly the same: the NPP personnel blame everything on the builders and designers, and they blame them...
But, in a Soviet-style optimistic way, suddenly uniting, they find their common mistakes, edit the ACS program and with pathos fix all the problems, improve the efficiency and reliability of the station, and receive gratitude...

[Doctor]

According to the Operating Reactivity Margin. Standard - not less than 15 rods.
The author writes a bold headline.

Block unloading: OZR drop below permissible

And then he immediately gives a printout that he doesn’t believe (doubtful) ).

7:10 a.m. — failure in the operation of the Skala central control system. The ORM was calculated without taking into account the immersion of 12 AR rods (the reactivity margin on which is never less than 2 RR1 st.) and is shown as equal to 13,2 RR rods. /As Karpan writes, the real value of the ORM at this time was about 18 Art. RR, which is doubtful./


And he believes the chatter of Rogozhkin, who was intimidated in court:

8:00 a.m. — unit status: reactor power 1520 MW, N(3) = 380/50 MW. OZR — not less than 16 st. RR. /According to court testimony — 13,2 st./

There was enough ORM there, at the time of the experiment - 26 rods. It's not about ORM.

[Alexander Odintsov]

Dear colleague, this fact has been recognized by the court and even by the State Penitentiary Service. What else do you need?

[Pokrovskij1959]

In transient modes, RBMK could have a reactivity reserve of less than 6 rods. This is a design defect of RBMK reactors and the reactor had a positive void coefficient of reactivity, which was not allowed by the PNS.

[Doctor]

About the "inexperienced replacement".
The Steinberg Commission also checked qualifications.
Conclusion: an ordinary shift, no better, but no worse than others.

But that's not even the point. The point is that:

According to G. Medvedev, a professional nuclear scientist who participated in the construction of the Chernobyl Nuclear Power Plant as deputy chief engineer of the station, the shift of Yuri Tregub, who handed over the shift to Alexander Akimov at 24:00 on 25.04.1986, was more experienced and was unlikely to have allowed the accident to occur.

So, Medvedev is wrong. Tregub REMAINED on the block and was there during the experiment. And Dyatlov himself was there.
But it did not help.

[Alexander Odintsov]

Everyone knows that the shift was inexperienced. The unit shift supervisor Alexander Akimov had never worked as a SIUR (SIUR - senior reactor control engineer). SIUR Toptunov L.F.: 26 years old, SIUR experience - 8 months. According to the testimony of the Chief Engineer of the Chernobyl NPP Fomin, "SIUR Toptunov was not very experienced, did not have the skills to work in transient modes", Akimov "was an inexperienced, young specialist".

[Doctor]

Everyone knows that the shift was inexperienced. The unit shift supervisor Alexander Akimov had never worked as a SIUR (SIUR - senior reactor control engineer). SIUR Toptunov L.F.: 26 years old, SIUR experience - 8 months. According to the testimony of the Chief Engineer of the Chernobyl NPP Fomin, "SIUR Toptunov was not very experienced, did not have the skills to work in transient modes", Akimov "was an inexperienced, young specialist".

"Everyone knew" - this is OBS)).
According to Fomin, this is how it is:
Fomin - Dyatlov is an experienced specialist, with 9 years of experience working at the Chernobyl Nuclear Power Plant, and knows his business well. I knew Akimov as a competent, attentive specialist.. I observed his work when I was still ZGIS. SIUR Toptunov was not very experienced, did not have the skills to work in transitional modes.

I repeat, Tregub WAS on the block. And Dyatlov was there. And they weren't drinking beer there, they were controlling the process. And they didn't see any alarming moments until the very end.

[Pokrovskij1959]

Steinberg was a mediocre specialist.

[Doctor]

About the "mystery" of 200 MW capacity.
Damn, at least look at the commission documents, Dyatlov's book and the computer records before repeating this conspiracy nonsense from IXBT)).

Dyatlov had no intention of violating the Experimental Program, he left the BShU, and when he returned, he saw that due to a faulty regulator the power had dropped to 40.

They started to raise it to the planned 700, but since it took almost half an hour, they decided to limit it to 200 MW.

And here Dyatlov agreed, thereby violating the experimental program. If they had not raised it at all, had given up on the experiment and simply shut down the reactor, there would have been no explosion.

But then they would have been given a dressing down, and the Regulations did not prohibit it...

[Free]

By the way, I think I saw in Fatahov's article that the unit was stopped for preventive maintenance, including for the long-overdue modernization of the safety systems. However, there were enough similar reactors in the country with the same physics and design problems - it is not a fact that this would not have happened at another station.

[october]

and again

They started to raise it to the planned 700, but since it took almost half an hour, they decided to limit it to 200 MW.

But then they would have been given a dressing down, and the Regulations did not prohibit it...

And for 200 MW they raised 186 rods - really, why bother with trifles, what kind of transient processes? Step on the gas full speed...

[Alexander Odintsov]

You write everything correctly. They wanted to end the experiment at any cost. And it turned out to be very high.

[Doctor]

And for 200 MW they raised 186 rods - really, why bother with trifles, what kind of transient processes? Step on the gas full speed...

Do you think the Schumachers were there?

Yuri Tregub was on the block, and not just was, but actively participated in the work and helped the shift, Toptunov in particular, who really had little experience.

Tregub Yu. Yu. - When switching from automatic to manual control, Toptunov dropped the power, I heard that too. But he took the right measures to raise the power. Akimov helped him. SIUR was more involved with the rods. And the control panel is large and very inconvenient to use.
When extracting rods in such a situation, special attention and caution are required. It is necessary to extract absorbers by approximately the same amount. I advised Toptunov which rods were best to choose. He did as he knew.
I also noticed Dyatlov behind my back. And when we raised the reactor power to 200 MW, I returned to the SIUT control panel. When I looked at the distribution field for the last time before the accident, the SIUR had pulled out about half of the rods close to the limit switches, and the rest were about two meters away. The last ORM value I saw was about 19 rods in the core.

[october]

If there are only 202 rods, then 202-19=183 rods were extended. While for 200 MW, about 13 extended rods are enough.
Do you think this is not Schumacher?

[Doctor]

If there are only 202 rods, then 202-19=183 rods were extended. While for 200 MW, about 13 extended rods are enough.
Do you think this is not Schumacher?

What does it mean "for 200 VMT 13 extended rods are enough"?

[october]

This is an estimate of how many rods need to be raised for the reactor to produce the required power. I remember I did it last time:
(200MW/3200MW)*202 rods = 13 rods had to be lifted.
A simple proportion under the assumption of a linear relationship, which is what designers should ideally strive for

[Free]

The ORM is a dimensionless value that depends on the number of rods in the zone, feedwater consumption, power, neutron flux density, for convenience it was calculated in rods and was calculated once an hour using the Prizma program on the Skala computer, and was printed out along with hundreds of other parameters. The shift personnel could not track this parameter in real time. And there was no particular sense in printing it out during transient modes, when it changed quickly. The ORM, as far as I remember, appears in the Regulations (that regulation) a couple of times or more in the context of the reactor economy, and not as a nuclear-hazardous parameter.

[october]

In the quote this value is very dimensional.

The last ORM value I saw was about 19 rods in the core.

Okay, so here's a question for you. So how many rods did they put out to get 200 MW of power?

[Free]

Study the material, OZR is a dimensionless quantity. I don't know how many were extracted. But were there any restrictions on the number of rods in the zone? There were restrictions on OZR, which is a calculated quantity and which they didn't know. There was no indication of this parameter on the control panel.

[october]

Study the material part, OZR is a dimensionless quantity.

Tell this to Yuri Tregub, whose words I quoted to you.

I don't know how many were extracted. Was there a limit on the number of rods in the zone?

So that's the whole point. The reactor's output power is regulated by the number of rods (physical ones) removed.
To obtain the reactor output power of 200 MW, it is enough to extract 13 rods (the estimate is higher). But the number of rods extracted, judging by what was said, was over 180 rods.
Do you see anything unusual here?

[Free]

Read Dollezhal, perhaps. He is the chief designer of the RBMK. He wrote how reactivity is measured in general and its operational reserve in particular. Well, and it depends not only on the control system in the zone.
If in those conditions all the rods except 13 were introduced into the zone, you would not have received any 200 MW, the reactor would have stopped. In addition, read the Regulations, there are no instructions on how many rods for what power to leave in the zone, it works a little differently, especially in transient modes.

[october]

Read Dollezhal, perhaps. He is the chief designer of the RBMK. He wrote how reactivity is measured in general and its operational reserve in particular. Well, and it depends not only on the control system in the zone.

I am interested in the final result, which is measured in the output watts that the reactor is currently producing. All rods are inserted - the reactor is at a standstill, all rods are removed - the reactor is at maximum power. We are talking only about statics.
Any complex device is first considered in a simpler mode, in this case in statics. Transient modes are calculated at the next stage, so we are not talking about any reactivity yet. First, let's deal with statics, then the rest.

If, under those conditions, all the rods except 13 were introduced into the zone, you would not have received any 200 MW, the reactor would have stopped.

13 rods - this is in statics. Taking into account the reactor conditions, let's say, it will give 200 MW with 20 rods removed. I made only the simplest quantitative assessment when I got 13 rods. But this is far from 180 rods.

In addition, read the Regulations, there are no instructions on how many rods for what power to leave in the zone, it works a little differently, especially in transient modes.

Why are you hiding behind the regulations when we are talking about the physics of the process in statics? What do the prohibitions in the regulations have to do with it, we need 200 MW - we are calculating how many rods need to be brought out.
Or do you always remove all 200-odd rods from the reactor in all cases of life from 3.2 MW to 180 GW? That is, it always operates (statically) in one thermal mode - at maximum?

[Doctor]

Read Dollezhal, perhaps. He is the chief designer of the RBMK. He wrote how reactivity is measured in general and its operational reserve in particular. Well, and it depends not only on the control system in the zone.

I am interested in the final result, which is measured in the output watts that the reactor is currently producing. All rods are inserted - the reactor is at a standstill, all rods are removed - the reactor is at maximum power. We are talking only about statics.
Any complex device is first considered in a simpler mode, in this case in statics. Transient modes are calculated at the next stage, so we are not talking about any reactivity yet. First, let's deal with statics, then the rest.
If, under those conditions, all the rods except 13 were introduced into the zone, you would not have received any 200 MW, the reactor would have stopped.

13 rods - this is in statics. Taking into account the reactor conditions, let's say, it will give 200 MW with 20 rods removed. I made only the simplest quantitative assessment when I got 13 rods. But this is far from 180 rods.
In addition, read the Regulations, there are no instructions on how many rods for what power to leave in the zone, it works a little differently, especially in transient modes.

Why are you hiding behind the regulations when we are talking about the physics of the process in statics? What do the prohibitions in the regulations have to do with it, we need 200 MW - we are calculating how many rods need to be brought out.
Or do you always remove all 200-odd rods from the reactor in all cases of life from 3.2 MW to 180 GW? That is, it always operates (statically) in one thermal mode - at maximum?

At that time, the RBMK-1000 had 211 control and protection system channels.
When Toptunov pressed the AZ, 187 rods went down. So (possibly ), in fact, in the active zone at the time of the accident there were:
211 - 187 = 24 rods.

[october]

When Toptunov pressed the AZ, 187 rods went down. This means (possibly winked ), that in fact, at the time of the accident, the following were in the active zone:
211 - 187 = 24 rods.

That's exactly what I'm talking about.
To provide a capacity of 200 MW, about 13 rods (let's say 20) are enough. More than 180 rods were brought out.
That is, despite the declared 200 MW, the reactor operated at a capacity of about 3 GW.
And even with the protections disabled.
It looks very strange to me.

[Doctor]

That's exactly what I'm talking about.
To provide a capacity of 200 MW, about 13 rods (let's say 20) are enough. More than 180 rods were brought out.
That is, despite the declared 200 MW, the reactor operated at a capacity of about 3 GW.
And even with the protections disabled.
It looks very strange to me.

The reactor is always DIFFERENT.

At that time, there were only 1888 technological channels, of which 1661 had fuel assemblies, 211 had control rods, and 16 had control sensors.
These 1661 with fuel - they are constantly changing in activity, the fuel burns out.

When the reactor is FRESH, just loaded, it reaches its nominal value with almost all the control rods lowered down, which, naturally, are lowered there first to the stop and then raised a little at a time.
That is, the shift works in a range, for example, like this - 181 rods are completely at the bottom, and 30 are working, they play with them, raising/lowering the power.

As the fuel burns out, the fuel assemblies are changed without stopping the reactor.

When a reactor is put into repair (as in Chernobyl), they work on almost exhausted cassettes, and here, in order for the reaction to proceed, only 30-40 control rods can be in the zone at all times, otherwise the reactor will “go out”.

Due to the large active zone of the RBMK, all these processes can occur locally in different parts of it, both in height and in coordinates, and the work of the personnel consists of maintaining the neutron field uniformly throughout the entire zone, trying to achieve complete burnout of the assemblies and using the reaction to obtain heat as EFFECTIVELY as possible.

That is why the RBMK reactor had a minimum ORM of only 15 rods, and experienced operators used even less, trying to make maximum use of the thermal energy of neutrons, since what went into the absorbers went nowhere. Although they also get a little warm of course.

And now the minimum ORM there is under 50 rods, that is, it has to be reloaded more often, more uranium is used up and the overall efficiency of current reactors has dropped by about 20 percent.

But security has increased. But this is not certain..

[october]

That is why the RBMK had a minimum ORM of only 15 rods.

You answered my question, thank you

[october]

But then another question arises. Have there been any independent assessments of the quality of the remaining nuclear fuel that will confirm that 186 pulled rods for this fuel correspond to 200 MW, and not 2 GW?

[Doctor]

But then another question arises. Have there been any independent assessments of the quality of the remaining nuclear fuel that will confirm that 186 pulled rods for this fuel correspond to 200 MW, and not 2 GW?

It was only possible to calculate accurately after unloading the fuel.
But it is clear that the reactor was worn out, was undergoing scheduled maintenance, and the experiment was timed to coincide with the shutdown of this reactor, at least 3/4 of the fuel assemblies were there from the initial load. It can also be indirectly confirmed by the isotopic composition of the scattered fuel, plutonium in particular.

Well, and the main thing is that if they had pulled out more rods than necessary, it would have passed the 200 MW mark, flown further, and then...
On the contrary, it was a dying fire, and even doused with water (xenon poisoning), it had to be stoked even up to 200.

[Pokrovskij1959]

There was no context in the Regulations at all on this matter and no explanations on this matter anywhere. But some employees knew what this parameter was for. And so you described the OZR accurately.

[Pokrovskij1959]

At industrial channel reactors, it was common practice to pull the reactor to power, for example, after an emergency. At NPPs, they did not shy away from this either. This was, of course, a gross violation of the PBYa. Many did not understand why the Regulations included a clause on the reactivity margin. The answer was simple, so that it was possible to control the reactor. But that was not all, with a zero reactivity margin, the reactor went into an unstable mode and became dangerous. The General Designer did not understand this either, otherwise there would have been protection for this parameter. But there was only an information system that issued this information once an hour or, in new projects, also upon request. And the personnel did not particularly pay attention to this parameter; they estimated it by eye at the control room.

[october]

see the answer above to another comrade

[Alexander Odintsov]

What does IXBT have to do with it, the author of the textbook, including V. L. Gurachevsky, writes about this (Introduction to Nuclear Energy, Rosatom library) and not only:
"00:05 - an event occurred that seriously disrupted the testing process. The reactor's power continued to decrease. The reasons why this happened have not yet been established, including due to closed access to individual documents describing the reactor's operation that night.
According to one version, the fact that parallel to the turbogenerator rundown test program, it was planned to measure turbine vibrations at idle speed played a role. To maintain the turbogenerator at idle speed, the 720 MW capacity achieved by that time and envisaged by the rundown program was too high. Therefore, they began to reduce it further, to the level of their own needs. The testimony of some witnesses says that this was done on the orders of A.S. Dyatlov.
Dyatlov, both in his testimony at the trial and in his book of memoirs, claims that he did not give such a command…”

[Doctor]

What does IXBT have to do with it, the author of the textbook, including V. L. Gurachevsky, writes about this (Introduction to Nuclear Energy, Rosatom library) and not only:
"00:05 - an event occurred that seriously disrupted the testing process. The reactor's power continued to decrease. The reasons why this happened have not yet been established, including due to closed access to individual documents describing the reactor's operation that night.
According to one version, the fact that parallel to the turbogenerator rundown test program, it was planned to measure turbine vibrations at idle speed played a role. To maintain the turbogenerator at idle speed, the 720 MW capacity achieved by that time and envisaged by the rundown program was too high. Therefore, they began to reduce it further, to the level of their own needs. The testimony of some witnesses says that this was done on the orders of A.S. Dyatlov.
Dyatlov, both in his testimony at the trial and in his book of memoirs, claims that he did not give such a command…”

Gurachevsky is generally a physics teacher at BSU, vice-rector for management and associate professor of ecology.
Everything he writes is his own fabrication from a broken telephone.
The key word in your quote is "according to one version."

They measured turbine vibration not in parallel, but sequentially, first vibration, then rundown. And this did not play any role in reducing the reactor power.

On Dyatlov's orders - only Tregub claimed this. It "seemed" so to him.

Tregub Yu.
"At about 5-15 minutes past the hour, I heard a conversation between Akimov and Dyatlov. The gist of it was that Dyatlov wanted the reactor to operate at 200 MW. Akimov, he was holding the program in his hands, citing arguments, apparently objecting. This is judging by his facial expression, his facial expressions. This is makes me think, that the power reduction was carried out on Dyatlov's orders. Although I didn't hear any direct orders from him."

Dyatlov himself states the following:

"I am accused of giving Akimov the order to reduce the reactor power from 760 MW (as it was at 24:00) to 200 MW, as a result of which poisoning processes began and the reactivity reserve dropped below 15 RR rods. I did not give such an order to Akimov. There is nothing like that in Akimov's testimony. This is in Tregub's testimony. I believe that we can clarify this issue during the trial.
I do not blame Toptunov for the power failure of up to 30 MW. Any operator has failures when switching to another regulator. One has more, another has less. In addition, the regulator he switched to was faulty. After this failure, Akimov himself proposed to increase only to 200 MW, although the program had 700 MW. The tests were ending, knowing the reactivity reserve for 24 hours 00 minutes, I decided to increase only to 200 MW."

[Alexander Odintsov]

I wouldn't trust Dyatlov. It was clear at the trial based on his testimony. Whatever you say, the reactor went up in flames under his leadership and it's perfectly clear to any physicist what the decisions he and his team were leading to. Tregub is a very authoritative specialist and at the trial he showed what was interesting against Dyatlov. I think it's not without reason.

N. Karpan and Yu. Tregub indicate that Dyatlov, instead of conducting an experiment at a power of 700 MW (thermal), as indicated in the test program, gives an indication to reduce the power to 200 MW (40 MW electrical).

I spoke with the experts who were in the group preparing the report. They all confirm this as well. Fomin also talks about this.

Expert - But when discussing the power level, Dyatlov demanded 200 MW, and the specialist physicist Kryat persistently demanded 700 MW. Did you know about this?
Fomin - Yes.

[Doctor]

I wouldn't trust Dyatlov. It was clear at the trial based on his testimony. Whatever you say, the reactor went up in flames under his leadership and it's perfectly clear to any physicist what the decisions he and his team were leading to. Tregub is a very authoritative specialist and at the trial he showed what was interesting against Dyatlov. I think it's not without reason.
N. Karpan and Yu. Tregub indicate that Dyatlov, instead of conducting an experiment at a power of 700 MW (thermal), as indicated in the test program, gives an indication to reduce the power to 200 MW (40 MW electrical).
I spoke with the experts who were in the group preparing the report. They all confirm this as well. Fomin also talks about this.
Expert - But when discussing the power level, Dyatlov demanded 200 MW, and the specialist physicist Kryat persistently demanded 700 MW. Did you know about this?
Fomin - Yes.

Possibly. But, IMHO, it is not essential. The reactor MUST NOT EXPLODE at either 700 MW or 200. Especially during emergency braking.

Have you read the Politburo meeting of July 3, 1986?

[i]"Gorbachev. The commission figured it out, Why was an unfinished reactor transferred to industry? The US has abandoned this type of reactor. Is that right, Comrade Legasov?

Legasov: In the USA such reactors were not developed or used in power engineering.

Gorbachev. The reactor was transferred to industry, but theoretical research was not continued <…> Why, after all, were theoretical research not continued? Could it not turn out that the voluntarism of individuals is drawing the country into an adventure? <…> Who made the proposal to locate nuclear power plants near cities?? Whose recommendations were these? <...> By the way, the Americans, after the accident that took place in 1979, did not begin construction of new nuclear power plants.

Shcherbina B.E. It was believed that the safety issue had been resolved. This is stated in the publication of the Kurchatov Institute, in the preparation of which Legasov also participated <...>

Gorbachev: How many accidents were there?

Bryukhanov (Director of the Chernobyl Nuclear Power Plant). There are approximately 1-2 accidents per year. <...> We didn’t know that in 1975 something similar happened at the Leningrad Nuclear Power Plant.

Gorbachev: There were 104 accidents, who is responsible?

Meshkov (First Deputy Minister of Medium Machine Building of the USSR). This station is not ours, but the Ministry of Energy's.

Gorbachev: What can you say about the RBMK reactor?

Meshkov. The reactor has been tested. Only there is no dome. If you strictly follow the regulations, it is safe.

Gorbachev. Then why did you sign a document that says its production should be stopped?? <...> You surprise me. Everyone says that this reactor is not finished, its operation can cause danger, and here you are defending the honor of the uniform.

Meshkov. I defend the honor of nuclear energy <...>

Gorbachev. You continue to assert what you have been asserting for 30 years, and this is an echo of the fact that the Sredmash sphere was not under scientific, state and party control. And during the work of the Government Commission, Comrade Meshkov, I received information that you behaved frivolously, tried to gloss over obvious facts.

Gorbachev. Sidorenko V.A. (Deputy Chairman of the USSR State Atomic Energy Supervision Authority) writes that RBMK will not meet modern international requirements even after reconstruction <...>

Shasharin G.A. (Deputy Minister of Energy and Electrification of the USSR): The physics of the reactor determined the scale of the accident. People did not know that the reactor could accelerate in such a situation. There is no certainty that its modification will make it completely safe. One can find a dozen situations in which the same thing will happen as in Chernobyl. This is especially true for the first units of the Leningrad, Kursk and Chernobyl NPPs. The Ignalina NPP cannot be operated at its current capacity. They do not have an emergency cooling system. They should be shut down first of all <...> It is impossible to build more than RBMK, I am sure of that. As for their improvement, the costs will not be justified. The philosophy of extending the service life of NPPs is far from always justified.

Gorbachev: What should the Kurchatov Institute of Physics do?

Alexandrov. I believe that this property (acceleration) of the reactor can be destroyedWe have ideas about possible solutions to this problem. This could be done in one or two years.

Gorbachev: Does this apply to currently operating reactors?

Aleksandrov: I believe that this property (acceleration) of the reactor can be destroyed. We have ideas about options for solving this problem. This could be done in one or two years.

Gorbachev: Does this apply to currently operating reactors?

Aleksandrov: The currently operating reactors can be made safe. I'll bet my head, old as it is, that they can be put in order. I ask that you relieve me of my duties as president of the Academy of Sciences and give me the opportunity to correct my mistake related to the shortcomings of this reactor.

Gorbachev: Is it possible to bring these reactors up to international requirements?

Aleksandrov. <...> All countries with developed nuclear energy do not operate on the same type of reactors that we use.

"<...>Mayorets (Minister, Member of the Government Commission): As for the RBMK reactor, this question can be answered unequivocally. No one in the world has taken the path of creating a reactor of this type <...> I assert that the RBMK, even after modification, will not comply with all of our current rules <...>

Ryzhkov We were heading towards an accident. If the accident had not happened now, it could have happened at any time given the current situation. After all, they tried to blow up this station twice, but they did it only in the third year. As it has now become known, there has not been a single year at the nuclear power plant without an emergency <...> The design flaws of the RBMK reactor were also known, but the corresponding conclusions were not made by either the ministries or the USSR Academy of Sciences.
<...> The task force believes that the stations with a large construction backlog with RBMK reactors should be completed, and that the construction of stations with this reactor should be stopped..."

Do you now understand why the Germans abandoned nuclear power plants?

[Alexander Odintsov]

Of course I read it. And I even wrote an article about the reactor's shortcomings.

The reactor MUST NOT EXPLODE at 700 MW, nor at 200. Especially during emergency braking.

In the next part I will describe how it happened step by step. Everything is very simple. Briefly see O. Novoselsky:

It is also known that the AZ5 button was pressed twice (it was pressed once by the operator at 1.23.39, the second AZM-AZRS signal was generated by the automation at 1.23.41), although it had to be held down continuously for the rods to move without stopping (in the pre-accident design). This fact, according to O. Novoselsky (NIKIET), casts doubt on the effectiveness of the "displacement" effect itself: "the AZ-5 button is pressed. But the power increase is rapid, and the speed of the emergency protection rods is only 0,4 m/s. The operator decides to speed up the introduction of the absorber rods: he releases the AZ-5 button and turns to the KOM key, de-energizing the clutches of the CPS rod drives. As soon as the operator released the AZ-5 button, the absorber rods stopped. The button was held for approximately one second… during which time the rods managed to move only 0,3 m in accordance with the acceleration characteristics.”

And more:

In the excerpt below, O. Novoselsky defines the degrees of importance of various accident factors:
"...after the violation of the turbogenerator (TG) rundown test program... conditions were created for an irreversible power runaway and explosion of the core. First: with almost complete absence of standard absorbers in the core, the process of decay and "burnout" of xenon took place, poisoning is a process with positive feedback, i.e. self-accelerating. Second: the RCPs connected to the rundown TG8 must be disconnected by their own protection of the electric motors for voltage and / or frequency of the supply current. Disruption of the supply of the remaining RCPs is inevitable due to insufficient pressure at the suction - a completely expected phenomenon. Then steaming of the core, power runaway due to a large steam effect. Third: cavitation steam from the SAM or even from the DRK does not condense in the water flow with low subcooling and enters the TC input. Again, a large void effect provides a powerful surge in energy release in the lower part of the core. Multiple TC ruptures follow and the accident continues. Each of the three factors is capable of independently bringing the situation to acceleration on prompt neutrons, the differences are only in the time interval from the beginning of the process to the explosion. In our case, all three factors participated in the accident... It should be understood that all the important events that destroyed the reactor fit into 6-7 seconds... the beginning of the acceleration is due to the cavitation steam that appeared on the SAM. In this case, the volumetric steam content of this flow could exceed 20%. "

[Doctor]

In the next part I will describe how it happened step by step. Everything is very simple. Briefly see O. Novoselsky:
It is also known that the AZ5 button was pressed twice (it was pressed once by the operator at 1.23.39, the second AZM-AZRS signal was generated by the automation at 1.23.41), although for the non-stop movement of the rods (in the pre-accident design) it had to be held down constantly.

I don't believe that Toptunov let her go. I've seen so many emergency situations and been there myself, he probably pressed her to the limit, until his fingers turned blue.

[Free]

Short-term pressingAZ-5, as far as I remember, was used when it was necessary to introduce negative reactivity into the reactor, this was normal practice. He could easily press and release if there were no emergency signals on the general. How did he know that the SUS in certain positions when introduced into the zone introduce positive (!) reactivity? And the signal memorization circuit was introduced after the accident.

[Alexander Odintsov]

It was written there in plain language. That the rods did not go far. Everything is simple, when they pressed the button in the reactor, the pre-accident process was already underway. The channels were already warped, the rods could not introduce any reactivity. Acceleration due to the steam effect and explosion. Everything is very simple.

[Doctor]

This fact, according to O. Novoselsky (NIKIET), casts doubt on the effectiveness of the “displacement” effect itself: “the AZ-5 button is pressed.

Well, then why did the LNPP melt down? And why did they make changes to the design?
This topic is theoretically substantiated and practically proven.

[Alexander Odintsov]

They included it because the effect theoretically took place. And there were many other shortcomings. RBMK is a very bad reactor. Its construction was a mistake by Minsredmash and Kurchatnik.

[Jager]

I just can't understand how it was possible to conduct an EXPERIMENT on a reactor, having disabled the most important protections and systems? Having disabled the SOAR, the MCP protections, etc. Has anyone thought about the consequences if suddenly something will go wrong?
Yes, the reactor had its own peculiarities and shortcomings. But the authors of the program and the operators did everything to put it into a mode not envisaged by the regulations and to verify it in practice. They were convinced...
It is obvious that the personnel did not have the necessary qualifications for such experiments. And it is not their fault. The task of the operators is precisely to maintain the reactor in safe modes.
By shutting down the reactor when the power dropped, the disaster could have been avoided...

[Doctor]

I just can't understand how it was possible to conduct an EXPERIMENT on a reactor, having disabled the most important protections and systems? Having disabled the SOAR, the MCP protections, etc. Has anyone thought about the consequences if something goes wrong?
Yes, the reactor had its own peculiarities and shortcomings. But the authors of the program and the operators did everything to put it into a mode not envisaged by the regulations and to verify it in practice. They were convinced...
It is obvious that the personnel did not have the necessary qualifications for such experiments. And it is not their fault. The task of the operators is precisely to maintain the reactor in safe modes.
By shutting down the reactor when the power dropped, the disaster could have been avoided...

Andrey, experiments on the implementation of new methods have different STAGES.

For example, I will give an example from my field.
New MEDICINE.

1. Search for pharmacologically active substances. Scientists determine the target in the body to which the action of the future drug will be directed, and look for a molecule with suitable properties.
2. Preclinical studies. The discovered substance is studied to determine how effectively and safely it affects the desired target. Studies are conducted on laboratory models (in vitro) and on animals (in vivo).
3. Production development. They optimize the composition of the drug, packaging, and scale up production.

Further - Clinical trials

Phase I. The drug is tested on healthy volunteers, safety and dosage are determined.
Phase II: The drug is used in a target group—a small number of patients with the disease that the new chemical compound is targeting.
Phase III. Studies are conducted on a large group of patients (several thousand) to confirm effectiveness and identify rare side effects.
Phase IV. Conducted after receiving a registration certificate, studies the tolerability and effectiveness of the drug in the long term.

Doesn't it bother you that any new medicine will be tried ON PEOPLE FOR THE FIRST TIME?

The Chernobyl experiment HAS PASSED the stages of theoretical research, testing on experimental reactors and the time has come to IMPLEMENT IT IN PRODUCTION PRACTICE.
Disabling some of the protections is a MANDATORY part of the experiment, because they will most likely be disabled when the reactor is hit with a "Dagger".

Moreover, the 3rd and 4th power units of the Chernobyl Nuclear Power Plant ALREADY had to be designed with pre-installed changes in the design of the turbines so that they could support the power generation until the diesel engines were turned on.

They didn’t meet the deadline, as usual, and decided to start with reactor No. 5.

But it didn't work out...

[Jager]

If the RBMK is hit by a Kinzhal, the diesels can only work for the dead. Because in essence, the reactor is not only single-loop, but also without a protective shell. And the shell is not provided due to the cyclopean size of the RBMK in relation to the compact VVER, which traces its history back to submarines.
I don’t need any explanations about the experiments; I work as an engineer at a research institute and have a perfect understanding of all the stages.
The technology must be tested, that's a fact. But why did they blow up only the Chernobyl Nuclear Power Plant?

[Alexander Odintsov]

Yes, the reactor had its own peculiarities and shortcomings. But the authors of the program and the operators did everything to put it into a mode not envisaged by the regulations and to verify it in practice. They were convinced...

You are looking at the root!!!

[Doctor]

Yes, the reactor had its own peculiarities and shortcomings. But the authors of the program and the operators did everything to put it into a mode not envisaged by the regulations and to verify it in practice. They were convinced...
You are looking at the root!!!

Alexander, at first glance it really seems as if the operators specifically wanted to blow up the reactor.

However, if you really want to look into the root and understand WHY their actions were like that, then you need to understand WHY THE EXPERIMENT WAS LIKE THIS. And most importantly, where the Chief Designer got the idea from)).

But for this you need THIS:

classified archives of investigative materials,

Well, or ask at NIKIET...

[Free]

Features? The reactor had critical flaws in physics and design, which resulted in positive feedback and control systems capable of introducing positive reactivity when they were introduced into the zone. And also the bad regulations from the developer. And the fact that they contradicted OPB-82 and PBYa-74, it could not have been designed in such a form, much less operated. I don’t think that if Aleksandrov and Dollezhal had been on the control room that shift, anything would have gone differently. Even if it had been a no-brainer, it could have happened another time and/or at another station. And rundown tests are not mandatory, at the Leningrad NPP they managed to handle the burnout of channels without them. And operators should not become researchers, but work within the framework that the designers had clearly outlined before them. Although, I repeat, the safety culture in the industry, by today’s standards, was weak.

[Pokrovskij1959]

In Germany, the reactor is controlled by technicians, not engineers. They know the bare minimum about the reactor. The design of the RBMK reactor was not worked out thoroughly. This reactor was simply scaled up from an industrial reactor, then scaled up to a capacity of 1500 MW, and they were even going to make a line of 2000 and 2600 MW. Only the turbine capacity was limited. The control system was quite primitive, the computer was weak.

[Alexander Odintsov]

The reactor had critical flaws in physics and design, which resulted in positive feedback and control systems capable of introducing positive reactivity when they were introduced into the zone. And also an unsuitable regulation from the developer

. All this is true. I eventually wrote about it in the article. But the accident was a product of the experimental design against the background of pressure on the personnel and the lack of risk culture among the personnel. This is not my definition - these are official conclusions - this is also written about in the article at the beginning. You yourself confirmed this.

[ln_ln]

Here is from the comments to one of the previous articles on VO (I am reproducing it because I did not come across it in this discussion):

last name, first name, patronymic of the Chernobyl accident: Georgy Alekseevich Kopchinsky.

Georgy Alekseevich Kopchinsky is a Ukrainian, born in 1939 in Talnoye, Cherkasy Oblast. In 1962 he graduated from the Moscow Power Engineering Institute, defending his diploma in the "NPP" department. He worked at the Institute of Physics, then at the Institute for Nuclear Research of the Academy of Sciences of the Ukrainian SSR. Candidate of Technical Sciences. Since 1973 he worked in the Ministry of Energy of Ukraine, as deputy chief engineer of the Chernobyl NPP, and then as director of the Smolensk NPP. Since 1983 he worked as an instructor, head of the nuclear energy sector of the Central Committee of the CPSU... It was G. Kopchinsky, combining a responsible leadership position of the Central Committee with excruciating studies on writing a doctoral dissertation, who gave a direct order over the phone, directly to the station's control panel, to bring the reactor of the 4th power unit of the Chernobyl NPP to maximum power; citing the need for statistical data... He was experimenting, so to speak... In response to reasonable objections from those in charge, he began to threaten at the control panel with reprimands, removal from office, and parting with party cards.

Then the “arrows,” as usual, were transferred to the plant personnel - Chernobyl NPP director V.P. Bryukhanov “grabbed” a sentence of 15 years, and those who were on the stand died immediately or died from ARS a little later... (Bryukhanov did not serve the entire sentence; in the 90s he was pardoned by Boris Yeltsin) . M. Gorbachev, taking the Central Committee “out of attack,” even tried, it seemed, to pull up the designers “for distribution.” But there was a “bummer” with the designers - the head of the team of designers of the RBMK-2000 reactor was personally listed as the President of the USSR Academy of Sciences, Academician A.P. Aleksandrov. It was also not easy to “melt” the head of Soviet science.

What about Kopchinsky? And in the 90s, Kopchinsky headed the nuclear energy industry of “independent Ukraine” - which did not benefit it, this energy industry.

[Jurkovs]

But those guilty of the accident have already served their sentences and been released. Apparently, the investigation was not conducted well, and considering the numerous subsequent deaths of the "liquidators" of the accident, which were not taken into account by the court, I consider it necessary to re-conduct both the investigation and the court proceedings.

[to sing]

Having read the comments of respected readers, I come to the conclusion that not everyone fully understands what a nuclear reactor is, and especially an RBMK reactor, how it is controlled, what processes occur in the active zone, etc. Therefore, as a current employee of the reactor shop of one of the NPPs with RBMK and a recent VIUR (lead reactor control engineer), I decided to explain some points related to the design and control of RBMK, so that respected readers could better understand what is written in the article.
First, let's find out the difference between a thermal power plant (TPP) and a nuclear power plant.
In a thermal power plant, fuel combustion (and, accordingly, heat generation) occurs with a constant supply of fuel (gas, fuel oil, coal dust, etc.) to a conventional boiler (furnace). When the fuel supply is stopped, combustion and heat generation stop, and that's it. There is, of course, a probability of an accident, but its consequences are a blown-up boiler at most, that is, only the release of energy stored in the coolant and in the fuel located directly in the boiler or in the supply pipelines takes place.
In the RBMK-1000 nuclear reactor (a high-power channel reactor with a thermal capacity of 3200 MW, electrical capacity of 1000 MW) of the Chernobyl type (stages 2 of the Leningrad, Chernobyl, Kursk, stage 1 of the Smolensk NPP), fuel in the form of fuel assemblies (FA) is located in 1661 process channels (PC), as of 1986 there were 211 channels of the control and protection system (CPS), 12 channels with DKE (energy release monitoring sensors by height) and 4 channels for fission chambers (for reactivity monitoring during the PPR). The average capacity of one fuel assembly is approximately 2 MW, the average fuel burnup at the 4th unit of the Chernobyl NPP on 24.04.86 was 1349 MW-day/fuel assembly (https://www.accidont.ru/memo/Karpan_02.html). That is, roughly speaking, with an average capacity of 2 MW, each fuel assembly was in the reactor for about two years. Imagine that at any given time, the reactor contains enough fuel to generate 3200 MW of energy for 2 years.
This is the main danger of nuclear power - a colossal amount of energy in the reactor, which can be released at any time under certain conditions. And one of the main tasks of the NPP personnel, along with the generation of electricity, is to prevent such conditions under which this energy is released at one time. In general, they are sitting on a giant powder keg measuring 12 meters in diameter and 7 meters in height (only a million times more powerful) and don't give a damn. And for this type of reactor, all the energy is prevented from being released by the control rods (aka RR rods) located in the active zone (AZ), which absorb excess neutrons. The total number of control rods in the AZ is approximately the operating reactivity margin (ORM).
Now about how the reactor is started. When the reactor is in the shut-down state, all the control rods are in the core at the lower limit switches, i.e. completely immersed (absorb all neutrons). To start the reactor, it is necessary to bring it to a critical state, i.e. a state in which a self-sustaining chain reaction of uranium and plutonium fission is possible. That is, the number of neutrons generated in the reactor is not less than the number of absorbed neutrons. If the number of generated neutrons is equal to the number of absorbed ones, then the reactivity is zero and the reactor power does not increase or decrease. If the number of generated neutrons exceeds the number of absorbed ones, then the reactivity is positive and the reactor power increases, if the reactivity is negative, the power decreases. It is important that the thermal power of the reactor is zero, and the reactor can already be in a critical state, i.e. an increase in power is possible. In order for the power to increase, it is necessary to introduce positive reactivity.
It is worth mentioning here that the reactor power is not proportional to the number of removed rods. Everything is a bit more complicated and simpler at the same time. So, to bring the reactor to a critical state, it is necessary to remove from 100 to 130 control rods, depending on the core composition, fuel burnup, etc. This is a rough estimate, but in any case, not less than 100 RR rods. Then, to increase the reactor power, it is enough to completely or partially remove one control rod (i.e. introduce any positive reactivity) and the reactor power will begin to increase. The power will increase indefinitely until the introduced positive reactivity is compensated by introducing the control rod back into the core or by the action of other (negative) reactivity effects inherent in this type of reactor. Then the reactor power will be fixed at a new level.
Next, xenon and samarium begin to accumulate in the RBMK-1000 reactor as the power increases. They absorb neutrons just like the control rods. And the greater the thermal power of the reactor, the greater the equilibrium concentration of xenon and samarium in the core, the more neutrons they absorb. When the reactor is operating at nominal power, the absorption capacity of xenon and samarium is several dozen control rods. And therefore, to increase the reactor power from the moment the reactor is brought into critical condition, it is necessary to remove several dozen more control rods to compensate for the negative reactivity effects for xenon and samarium. There are many more reactivity effects, both positive and negative, but there is no need to mention them here, since they do not play a decisive role in the ORM at constant power. So it turns out that out of 211 control rods in the core, when the reactor was operating at a nominal power of 3200 MW, there were about 30 left, this is the ORM for the RBMK-1000 of 1986. Now the ORM for the RBMK-1000 is 43-48 control rods plus several dozen additional absorbers (AD).
A little more about reactor control. Nuclear physics is such that for safe reactor control the maximum value of the introduced positive reactivity is limited by the βeff index, above which the reactor starts to accelerate on prompt neutrons and the power starts to grow exponentially by 1000 times per second, and no one can stop it. Therefore, it is very important to know the effects (coefficients) of reactor reactivity, which manifest themselves in a very short time. For the RBMK-1000 model of 1986, the main ones were the steam effect (~5βeff) and the end effect of displacers ((~1,5β÷2βeff). There was also the effect of dehydration of the control rod channels (~2÷3βeff), but it did not play a special role in the accident. That is, it is clear that there are not many options to blow up that reactor, but a decent number.
There is also such a concept as the coefficients of uneven distribution of energy release by the height (Kz) and by the radius (Kr) of the reactor, which tell us in which part of the reactor the energy release is higher or lower. In this case, we are interested in Kz, since before the accident at the 4th unit of the Chernobyl NPP, the maximum energy release shifted to the upper and lower parts of the core as a result of uneven poisoning with xenon. The highest probability of the start of reactor acceleration on prompt neutrons was in the upper and lower parts of the core.
Now we come to the understanding that before the accident at the 4th unit of the Chernobyl NPP on 26.04.86 as a result of xenon poisoning, the ORM was, according to various estimates, from 2 to 8 RR (CS) rods, i.e. all the colossal energy of the reactor from escaping was kept only by a certain amount of xenon and samarium in the core, which the reactor operator cannot control [the amount] in any way. If the xenon concentration begins to decrease rapidly as a result of the introduction of positive reactivity and, accordingly, the growth of the neutron flux, then the operator may not have time to compensate for this by introducing the CS rods into the core. In this case, we will take into account that all the RR rods were in the upper part of the core, and some USP rods may have been partially introduced from below, but this is not a fact. The speed of introducing rods into the core was then approximately 0,5 m/s. I.e. The rods took at least 14 seconds to reach the bottom of the reactor.
I will make one more digression. In 1985, there was a similar case at the Smolensk NPP, when they tried several times to bring the reactor poisoned by xenon into a critical state, but each time the reactor was shut down by the emergency protection due to power or acceleration speed. During the last attempt, the ORM was no more than 5!! control rods (I don't remember exactly), the protection worked again, the reactor was shut down and did not explode. That is, the end effect of the displacers did not work here.
As a result of all of the above, it can be assumed that reactor 4 of the Chernobyl Nuclear Power Plant exploded on 26.04.86 due to a combination of factors, such as:
- unevenness of Kz (maximum energy release in the lower and upper parts of the reactor);
- small OZR, there was nothing to absorb the ever-increasing neutron flux;
- introduction of positive reactivity into the lower part of the reactor core as a result of the end effect of the displacers;
- introduction of positive reactivity into the lower part of the reactor core as a result of a decrease in the total flow rate through the reactor during the experiment and a shift in the coolant boiling point to the bottom of the reactor or a complete cessation of flow rate as a result of the failure of the main circulation pump (steam reactivity effect)

[virA]

An article for statisticians (specialists).
Author, could you please explain the main points?
Run out, run out.
Run-out of what? Generator? And what does the reactor have to do with it?

[Peter Yakovlev]

I have carefully read all the comments from respected nuclear energy experts... But I will give my two cents: The Chernobyl accident occurred only because of the staff's STUPIDITY .Which was NOT present at any other NPP with RBMK reactors. Not at Kursk NPP, not at Smolensk NPP, not at Leningrad NPP, and not even at Ignalina NPP (before its closure)...Nonsense, which later manifested itself in all its glory after the proclamation of Independence and the consequences of two Maidans...