Chernobyl Anatoly Dyatlov’s real interview (English)

YouTube Video Transcript: Chernobyl - Summary

Key Concepts:

• RBMK-1000 reactor design flaws
• Experiment on turbine generator run-down
• AZ-5 (emergency protection) system
• Positive void coefficient
• Operational errors vs. design flaws
• Post-accident investigation and blame assignment

1. Events Leading to the Experiment (April 25, 1986):

• Anatoly Stepanovich Dyatlov, former deputy chief engineer for operation at the Chernobyl Nuclear Power Plant, recounts the events of April 25, 1986, when the fourth reactor was scheduled for shutdown for maintenance.
• Power reduction began on April 25th. The grid dispatcher initially prohibited further power reduction mid-day.
• Dyatlov went home to rest, instructing the operational staff to inform him when further power reduction was permitted.
• Around 10 PM, he was notified that power reduction was allowed and arrived at the control room around 11 PM, when the reactor power was at 50%.
• He spoke with the outgoing shift supervisor, Yuri Tregubov, and the incoming shift supervisor, Alexander Akimov, confirming their understanding of the tasks.
• The tasks included reducing power, unloading the turbine, measuring its vibrations (turbine #8 had high vibration), and conducting an experiment on the turbine generator run-down and powering auxiliary mechanisms during run-down.
• The experiment was initially planned before the reactor startup but was postponed. Previous tests in 1984 and 1985 yielded unsatisfactory results regarding voltage drop speed, requiring modifications to the generator excitation system.
• Experiments were conducted on the third and fourth reactors after the modifications, but only in idle mode. The April 26th experiment aimed to simulate real-world conditions more closely.

2. The Experiment and the Accident:

• Dyatlov argues that the experiment itself was not the cause of the accident, but rather the reactor's unsatisfactory characteristics, which were not fully understood at the time.
• He describes the accident as a "catastrophe" that could have occurred during any operation, not specifically tied to the experiment.
• The program for the experiment was well-structured and had been discussed multiple times. Despite post-accident scrutiny, no significant flaws were found.
• Dyatlov refutes claims that the program lacked safety measures, stating that it clearly outlined all necessary precautions, including power supply switching.
• Around 12:30 AM, Dyatlov returned to the control room and noticed the reactor power was at 50-70 MW.
• Akimov explained that the power had dropped to 30 MW during the switch of the automatic power regulator. Dyatlov considered this a normal occurrence and authorized further power increase.
• Dyatlov denies any violation of regulations in raising the reactor power after the "power dip," stating it was in accordance with the operational documents of 1986.
• After stabilizing the power at 200 MW, vibration measurements were taken successfully.
• Dyatlov conducted a final briefing with the team involved in the experiment.
• At 1:23:04 AM, the turbine generator run-down experiment began.
• Dyatlov overheard a conversation between reactor operator Leonid Toptunov and Akimov. Akimov instructed Toptunov to "shut down the rods" (activate the AZ-5).
• Dyatlov notes that Akimov did not immediately order the reactor shutdown, but he didn't consider it significant at the time.
• Toptunov activated the emergency protection (AZ-5) system at 1:23:47 AM.
• Dyatlov emphasizes that the AZ-5 system is used in various situations to shut down the reactor.
• Dyatlov states that the reactor went into a power excursion precisely because of the emergency protection system, which was supposed to shut it down.
• He describes the explosion as a powerful impact that shook the entire building.

3. Immediate Aftermath and Response:

• Dyatlov initially thought the explosion was related to the deaerators located above the control room.
• He ordered everyone to the backup control panel but then rescinded the order when the situation stabilized momentarily.
• He observed that the pressure in the primary circuit was zero, and the coolant flow was also zero, indicating a catastrophic loss of cooling to the fuel channels.
• He realized that the fuel elements were not being cooled and would soon melt down.
• Dyatlov emphasizes that the accident occurred in a routine situation, with no prior warning or risky actions.
• The control system did not register any emergency or warning signals before the AZ-5 button was pressed.
• He found the reactor control team in a state of shock and confusion.
• He observed that the control rods were in an intermediate position, and the reactivity meter showed a positive value, indicating increasing power.
• He ordered Kudryavtsev and Proskuryakov to manually lower the control rods but realized it was futile.
• Dyatlov observed no panic among the 13-15 people in the control room.
• He ordered the activation of smoke removal fans and went to the turbine hall.
• The turbine hall was severely damaged, with collapsed roofing, damaged pipes, and fires.
• He encountered Anatoly Kurguz, a central hall operator, severely burned by steam, and Semonenko, the gas circuit operator, who reported the destruction of the ventilation system.
• He went outside and observed the destruction of the reactor building.
• He instructed the fire brigade on the location of the fire water supply.
• He instructed the shift supervisor of the third reactor, Bagdasarov, to shut down the third reactor.
• He instructed Belichenko and Akimov to de-energize all mechanisms, displace hydrogen from the generators, and drain oil from the turbines to prevent further fires.
• He learned that Valery Khodemchuk, the operator of the main circulation pumps, was killed in the explosion.
• He learned that Shashenok had been severely burned and was taken to the medical center, where he later died.
• He ordered Bagdasarov to shut down reactor 3.
• He met with Perevozchenko and learned that Khodemchuk was missing.
• Dyatlov experienced a complete loss of strength and saw no immediate tasks to perform.
• He received a call from Director Bryukhanov, who instructed him to go to the civil defense headquarters with reactor diagrams.
• He reported to the director that there had been a power surge, likely due to a malfunction of the emergency protection system.
• He was then taken to the hospital.

4. Post-Accident Events and Trial:

• After receiving medical treatment, Dyatlov discussed the events with colleagues.
• He was transferred to a hospital in Moscow on April 27th and remained there for six months.
• He was arrested on December 4, 1986, after being questioned as a witness.
• Dyatlov states that the blame was always going to be placed on the personnel, as the Soviet Union did not acknowledge accidents caused by faulty equipment.
• He reviewed documents during his imprisonment and realized that the reactor's negative characteristics had been known to the designers for a decade, since the 1975 accident at the Leningrad Nuclear Power Plant.
• By December 1986, he had a clear understanding of the cause of the explosion.
• The trial of the "Chernobyl criminals" took place in July 1987.
• Dyatlov claims that the outcome of the trial was predetermined after the technical council, chaired by Alexandrov, placed all blame on the operational personnel, which was confirmed by the government commission and the Politburo.
• The judge rejected 24 of Dyatlov's questions to the judicial technical expert commission, which were aimed at determining whether the RBMK-1000 reactor in 1986 complied with design standards.

5. Notable Quotes:

• "Экспериментов никакого отношения к аварии не имеет. Это его связали с аварией только недобросовестные расследователи этой аварии." - "The experiment has nothing to do with the accident. It was only linked to the accident by unscrupulous investigators of this accident."
• "А так всё это произошло из-за совершенно неудовлетворительных характеристик реактора, которые тогда еще не были ясны." - "But all this happened because of the completely unsatisfactory characteristics of the reactor, which were not yet clear at that time."
• "На самом деле никаких нарушений, которые могли бы привести не только к взрыву, а даже к остановке реактора в 6 апреля и 25 на оперативный персонал не делал, не допустил, и ни о каком взрыве реактора не может быть и речи, если бы реактор был выполнен согласно правил проектирования." - "In fact, the operational personnel did not commit any violations that could have led not only to an explosion, but even to the shutdown of the reactor on April 6 and 25, and there can be no question of any reactor explosion if the reactor had been designed according to the rules."
• "Вообще говоря, можем мыслить, что аварийная защита не справилась с быстро текущем каким-то процесс, но чтобы собак во время защита взрывала, я такого и по мысль даже помыслить невозможно, их страшного в страшном сне не может это приснится." - "Generally speaking, we can imagine that the emergency protection could not cope with some rapidly flowing process, but that the protection would explode during the process, I cannot even imagine it, it cannot be dreamed of in a terrible dream."
• "В советском союзе не происходило аварий из-за плохого оборудования. В советском союзе были аварии только по вине обслуживающего персонала, диспетчер там оператор мастер, а из-за плохого оборудования не было таких случаев." - "In the Soviet Union, accidents did not occur due to bad equipment. In the Soviet Union, there were accidents only due to the fault of the maintenance personnel, the dispatcher, the operator, the master, but there were no such cases due to bad equipment."

6. Technical Terms:

• RBMK-1000: Reactor Bolshoy Moshchnosti Kanalny (High-Power Channel-type Reactor) - A Soviet-designed nuclear power reactor.
• AZ-5 (Аварийная Защита 5): Emergency Protection System 5 - The reactor's emergency shutdown system.
• Positive Void Coefficient: A characteristic of the RBMK reactor where the formation of steam voids in the coolant increases reactivity, potentially leading to a power surge.
• Reactivity: A measure of the departure of a nuclear reactor from criticality. Positive reactivity leads to an increase in power.
• Turbogenerator Run-down (Выбег турбогенератора): The process of allowing a turbine generator to slow down after being disconnected from the power grid. The experiment aimed to use the turbine's inertia to power auxiliary systems.

7. Logical Connections:

The transcript follows a chronological order, starting with the preparations for the experiment, detailing the events leading up to the explosion, describing the immediate aftermath and the actions taken by Dyatlov and his team, and concluding with the post-accident investigation and trial. Dyatlov consistently argues that the accident was not caused by operational errors but by the inherent flaws in the RBMK-1000 reactor design, particularly the positive void coefficient and the flawed AZ-5 system. He connects the known issues with the reactor design to the events of the accident, suggesting that the AZ-5 system, instead of shutting down the reactor, caused a power surge that led to the explosion.

8. Data and Statistics:

• Reactor power at 50% around 11 PM.
• Power dipped to 30 MW during the switch of the automatic power regulator.
• Power stabilized at 200 MW before the experiment.
• Experiment started at 1:23:04 AM.
• AZ-5 button pressed at 1:23:47 AM.
• Explosion occurred at 1:23:46 AM (discrepancy in timing is noted).
• Control rods were lowered to 2.5-3 meters.

9. Conclusion:

Dyatlov's account presents a strong argument that the Chernobyl disaster was primarily caused by the inherent design flaws of the RBMK-1000 reactor, particularly the positive void coefficient and the flawed AZ-5 system. He contends that the operational personnel, including himself, did not violate any regulations and acted reasonably in the face of an unforeseen and catastrophic event. He criticizes the post-accident investigation and trial as a politically motivated effort to blame the personnel rather than acknowledge the systemic problems with the reactor design. His testimony provides a valuable perspective on the events of Chernobyl, highlighting the importance of understanding the technical complexities of nuclear power and the potential consequences of design flaws.