Chernobyl disaster: Difference between revisions

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The accident occurred during a safety test meant to measure the ability of the steam turbine to power the emergency feedwater pumps of an [[RBMK|RBMK-type nuclear reactor]] in the event of a simultaneous loss of external power and major coolant leak. During a planned decrease of reactor power in preparation for the test, the operators accidentally dropped power output to near-zero, due partially to [[xenon poisoning]]. While recovering from the power drop and stabilizing the reactor, the operators removed a number of control rods which exceeded limits set by the operating procedures. Upon test completion, the operators triggered a reactor shutdown. Due to a design flaw, this action resulted in localized increases in reactivity within the reactor (i.e., "[[Scram|positive scram]]"). This resulted in rupture of fuel channels, leading to a rapid decrease in pressure which caused the coolant to flash to steam. This decreased neutron absorption, leading to an increase in reactor activity, which further increased coolant temperatures (a positive feedback loop). This process resulted in steam explosions and [[Corium (nuclear reactor)|melting of the reactor core]].<ref name="insag7" />