This event was one of the worst accidents in the history of nuclear power. It was rated level 7, the most severe level, on the International Nuclear Event Scale. The only other accident with a level 7 rating is Fukushima. Because the RBMK reactors used at the plant had no containment building to keep the radiation in, radioactive fallout drifted over parts of the western Soviet Union, Eastern Europe, Scandinavia, the UK, and the eastern United States. Large areas of Ukraine, Belarus, and Russia were badly contaminated. About 60% of the radioactive fallout landed in Belarus. About 360,000 people needed to be moved to other places, where they could live after the accident. In addition, many people suffered from acute radiation poisoning and long term illnesses such as thyroid cancer.