On 25th April 1986, Reactor Four at Chernobyl Nuclear Power Station was shutdown for routine maintenance. While it was shutdown a test was to be run to measure the effectiveness of the emergency equipment and core cooling pumps until power was restored.

The reactor shutdown proceeded until it was generating approximately half power, at this point further shutdown was refused. The emergency core cooling system was switched off and the reactor maintained its power levels. As the day was coming to an end it was agreed that the power should be reduced further.

As part of the test the reactor was to be stabilised at 1,000MW, but as a result of errors it crashed down to 30MW, creating serious problems. The operators tried to counter the power loss by freeing the control rods manually and in the early morning of 26th April the reactor re-stabilised.

However, within half an hour, a more serious situation developed. A drop in steam pressure occurred. This meant the operators had to remove nearly all the rods. The reactor was now very unstable with adjustments repeatedly having to be made every few seconds,

Finally, it became too much and a build up of steam in the cooling channels meant the operators could not control the resulting power surge. The sudden increase in temperature caused a steam explosion which destroyed the reactor core. A second explosion two minutes later compounded the disaster.

The prevailing winds blew much of the radiation over Belarus, and today only 1% of the land remains uncontaminated. Hundreds of villages and towns have ceased to exist, 25% of all farmland and forest is lost, and the entire country has been proclaimed a zone of international ecological disaster.