Chernobyl

Reactor four was being run through a safety test at low power when it went prompt critical at twenty-three minutes past one in the morning. The lid of the reactor - a thousand tonnes of it - was lifted off and the graphite core caught fire.

The first firefighters arrived within minutes. They were not told what they were standing on. They put water on a graphite fire in fuel-laden smoke and several of them picked up pieces of graphite with their hands. Most of those men were dead within weeks.

Three engineers - Ananenko, Bezpalov and Baranov - waded into the flooded basement beneath a molten core to open valves and drain it, so that the melt would not reach the water and throw steam and fuel across Europe.

Six hundred thousand liquidators were brought in to clean the roof and build the sarcophagus, many of them conscripts given a shovel and ninety seconds on the roof each.

Thirty-one deaths were officially recorded in the first months. The toll has been rising for forty years and no honest figure can be given. This roll is not closed.