Welcome to Chernobyl
The Chernobyl Accident
25 to 26 April 1986The accident in reactor no. 4 at the Chernobyl nuclear power station happened in April 1986. The operating crew planned to examine whether the turbines could produce sufficient energy to keep the coolant pumps running in the event of a loss of power. The safety systems were deliberately switched off for testing and the reactor had to be powered down.y. What happened was that planned powerdowns did not go correctly and the reactor power level fell to less than 1 per cent instead of a gradual fall.. There was a sudden and unexpected power surge and the reactor's emergency shutdown failed. Within seconds, the power level and temperature rose to dangerous levels and the reactor was effectively out of control resulting in the 1000 ton reactor expliding releasing radioactive fission products released during the core meltdown were sucked up into the atmosphere.
What caused the accident?
Eyewitness reports, measurements carried out after the accident, and experimental reconstructions were undertaken. The causes of the accident where both human error and imperfect technology. On Friday 25 April 1986, a test was run was interrupted for nine hours. Several flaws in the technical design of the reactor type are thought to have been decisive factors cetering around the control rods which control the reactor's temperature. The braking system that would effectively stop the rods being lowered and hence the reactors temperatures failed and instead of reversing the lowering temperature actually increased it dramatically destroying the reactor.
A similar Chernobyl -like Accident, but with much less severe consequences, had already occurred in Lithuania in 1983. This experience and the lessons learnt was fatefully not passed on to the operating crew in Chernobyl.