LEGASOV’S INVESTIGATION

PUBLISHED DATE : September period, 1986

CLASSIFICATION : PERMISSION ONLY

MANAGED BY : Chernobyl Disaster Goverment Commission (led by Legasov)

SUBJECT : Working document for Chernobyl Investigation of the disaster

PUBLICATION : NOT FOR PUBLICATION

Based on the investigation conducted by the State Commission on the Chernobyl Accident led by Legasov, revealed several key findings regarding the causes of the disaster. Here are some of the significant conclusions from the report:

Design Flaws

The report identified fundamental design flaws in the RBMK reactor, including unsafe control rod design, a positive void coefficient, and poor containment structure. These design deficiencies contributed to the severity of the accident.

Positive Void Coefficient :

One of the most significant design flaws was the positive void coefficient. In normal operation, this means that as steam bubbles form in the reactor coolant, it reduces the ability to moderate the nuclear reaction effectively. This positive feedback loop led to an increase in power output, creating a highly unstable reactor configuration.

Inadequate Control Rod Design :

The RBMK reactor used graphite-tipped control rods, which initially displaced water coolant when inserted. This temporary increase in reactivity caused a power surge before the control rods could fully absorb neutrons and reduce the power output. This design flaw contributed to the rapid power increase during the Chernobyl accident.

Poor Containment Structure :

The RBMK reactor lacked a robust containment structure. The reactor core was housed in a relatively flimsy building, which offered minimal protection against the release of radioactive materials during a severe accident. This design flaw resulted in the widespread dispersion of radioactive debris following the explosion.

Limited Safety Features :

The RBMK reactor had limited safety features compared to other reactor designs. It lacked certain key safety systems, such as a secondary containment structure and a core-catcher to mitigate the consequences of a catastrophic accident.

Dyatlov , Fomin and Bryukhanov on trial for mishandling the Chernobyl Nuclear Reactor and cause a Nuclear disaster. All of them were sentence to 10 years in prison

Human Error

Human error played a significant role in the disaster. While design flaws existed in the RBMK reactor, the actions and decisions of the operators on the night of the accident exacerbated the situation.

Violation of Safety Procedures :

During a safety test being conducted at Chernobyl, several safety procedures were violated. The operators deviated from the approved test protocol and disabled critical safety systems, including the emergency core cooling system. This deviation from established procedures increased the risk of an accident.

Inadequate Training:

The operators involved in the test at Chernobyl were not adequately trained to handle the complex situations that arose during the test. Their understanding of the reactor’s behavior and response to certain conditions was insufficient.

Failure

Of Communication :

There was a lack of effective communication between the operators, shift supervisors, and higher-level management. Important information about the reactor’s condition and the risks involved was not properly conveyed, leading to a delayed and inadequate response to the unfolding crisis.

Overconfidence and Complacency :

The operators and management at Chernobyl particularly Anatoly Dyatlov, Nikolai Fomin and Viktor Bryukhanov had a sense of overconfidence in the safety of the reactor and a complacent mindset regarding potential risks. This mindset contributed to a disregard for safety protocols and a failure to recognize the gravity of the situation until it was too late.