The Windscale fire: Britain’s largest nuclear accident

On 10 October 1957, a reactor caught fire at the British Windscale site in Cumbria, now Sellafield. The fire broke out in Unit 1 of two reactors built as part of Britain's post-war atomic bomb project. It is the largest nuclear accident in British history, level 5 out of 7 on the international INES scale.

Fire and release

The fire burned for three days and released radioactive fallout that spread across Britain and the rest of Europe. Iodine-131, with a half-life of about eight days, caused particular alarm: once inside the body it accumulates in the thyroid gland and raises the risk of cancer of that organ, especially in children.

The authorities checked milk in the surrounding area and found dangerous iodine-131 contamination. Milk from roughly 500 km² of pasture was destroyed for about a month: diluted a thousandfold and discharged into the Irish Sea. People from the surrounding area were not evacuated.

Harold Macmillan's government played down the scale and censored reports about the fire, fearing a blow to trust in nuclear power and to British-American nuclear relations. The Penney commission's report was published in full only in 1988.

Health and the reactor's fate

Calculations based on the volume of the release gave about 190 cases of cancer, around 100 of them fatal. Later epidemiological studies did not confirm such a rise: a 2024 paper found no link between childhood iodine-131 exposure and thyroid cancer, and a 2010 study found no significant long-term health effects in workers who took part in the cleanup.

The reactor was deemed unrecoverable: part of the fuel was removed, the core was sealed, and final dismantling of the reactor is scheduled for no earlier than 2037.

Image: File:Windscale-reactor.svg CC BY-SA 4.0 · License

Image: Chris Eaton CC BY-SA 2.0 · License

Translation editor: Ловушкин А.