The Chernobyl nuclear accident occurred on April 26, 1986, at the Chernobyl Nuclear Power Plant in Ukraine. A reactor explosion released large amounts of radioactive particles into the atmosphere, affecting surrounding areas and spreading across Europe. The disaster was caused by a flawed reactor design and operator errors during a safety test. It resulted in immediate deaths and long-term health issues for many people, including increased cancer rates. The area around the plant remains largely uninhabitable, leading to the establishment of the Chernobyl Exclusion Zone.