The Chernobyl Nuclear Power Plant in Ukraine was the site of the worst nuclear accident in history that occurred on April 26, 1986. The disaster happened during a safety test in reactor number four and was caused by a combination of human error and faulty design. The explosion and fire released a large amount of radioactive material into the atmosphere, affecting Ukraine, Belarus, and nearby areas. Thousands of people were evacuated from the surrounding area, and strict safety regulations in nuclear power plants were implemented worldwide as a result.