On April 26, 1986, a nuclear reactor rupture occurred at the Chernobyl nuclear power plant in Ukraine, then under Soviet rule. This caused an explosion at the nuclear power plant. A large amount of radioactive material leaked out, covering Ukraine, Russia, Belarus, and more places in Europe and beyond. It was the most serious nuclear power accident in history; the repercussions reached far and wide, and the number of victims may never be quantified.

The main cause of the accident was improper safety design in the nuclear power plant's reactor, and negligence in human operation. This sparked concern around the world regarding the safety of nuclear energy in the Soviet Union. It also called into question the stability of the Communist Party of the Soviet Union. Mikhail Sergeyevich Gorbachev, then General Secretary of the Communist Party of the Soviet Union, has said: "The Chernobyl nuclear accident may be what truly caused of the collapse of the Soviet Union five years later; it was even more important than the reforms that I started."

References: [關鍵評論網("The News Lens")(Chinese)] (https://www.thenewslens.com/article/117050/fullpage); [環境資訊中心("Taiwan Environmental Information Association")(Chinese)] (https://e-info.org.tw/node/54403); [BBC (Ukrainian)] (https://www-bbc-com.translate.goog/ukrainian/ukraine_in_russian/2016/04/160430_ru_s_foreign_press?_x_tr_sl=ru&_x_tr_tl=zh-TW&_x_tr_hl=zh-TW&_x_tr_pto=sc)