#1 The Accident

What happened on 26 April 1986

Much of what happened at Chernobyl in the early hours of 26th April 1986 is clear.

The plant’s senior management had undertaken a required safety test – an experiment, really – on the reactor in Unit 4, and it went disastrously wrong.

There was a least one explosion of hydrogen gas and a huge blast and fire which wrecked the reactor’s highly-radioactive core and blew it and its protective concrete shield onto their sides. The roof of the building (never designed as a shield) was ripped off and, in the intense heat, a funnel of highly radioactive material – metals, gases and building fabric – was shot a mile high into the sky. A plume of radioactivity spread patchily, mostly north-west. An aberrant sub-plume dumped stuff in an area to the south west of the plant.