The Windscale fire in 1957. The fire released radioactive fallout which spread across the UK and the rest of Europe.The radioactive isotope iodine-131, which may lead to cancer of the thyroid, was of particular concern at the time. It has since come to light that small but significant amounts of the highly dangerous radioactive isotope polonium-210 were also released. Windscale has since been renamed Sellafield. There have been many hundreds of accidents around the world since, many of which you will not see in the news until many years later, if at all, so secretive is the nuclear industry.