At 1:23:40 a.m. local time on Saturday, April 26, 1986, reactor 4 at the V. I. Lenin Nuclear Power Plant near Pripyat, Ukrainian Soviet Socialist Republic, exploded. A planned low-power safety test, run by night-shift personnel who had been ordered to proceed despite warnings, drove the RBMK-1000 reactor into a state its designers had specifically marked as forbidden. The graphite-tipped control rods, lowered to scram the reactor, briefly added reactivity before shutting it down. The core's thermal output spiked to approximately 30,000 megawatts — ten times rated capacity — in four seconds. Two steam explosions ripped the 1,000-tonne upper biological shield off the reactor and exposed the burning graphite core to the atmosphere. Two workers died at the moment of explosion. Twenty-nine more — firefighters, control-room operators, plant electricians — died from acute radiation syndrome within four months. Forty-eight hours passed before the city of Pripyat (population 49,360) was evacuated. The Soviet government did not publicly acknowledge the accident until April 28, after Swedish nuclear technicians at Forsmark detected the airborne plume 1,200 kilometres to the northwest. The cover-up was, by Mikhail Gorbachev's own subsequent assessment, the moment Soviet glasnost became unavoidable.
State & Intelligence Operations
1986
