The meltdown of the Chernobyl Nuclear Power Plant in Ukraine occurred. The accident was caused by a system test that ultimately led to explosions, releasing radioactive contaminants that spread across Europe and the Soviet Union. Two plant workers died in the explosion, and 28 people died within weeks due to acute radiation syndrome. 350,000 people were immediately evacuated. The contaminated area covered 39,000 square miles, encompassing Belarus, Ukraine, and Russia.
The World Nuclear Association rates this as one of the worst nuclear disasters to date. The WNA claims that the disaster was due to a flawed Soviet reactor design and mistakes made by plant operators. There were no health and safety procedures in place at the time.
In 2011, Chernobyl was declared a tourist attraction. Studies have shown that there is much greater biodiversity in this area due to the absence of humans.