In 1986, a reactor exploded at the Chernobyl nuclear power plant (then located in the Soviet Union, now in Ukraine) as a result of a failed test, releasing a radioactive cloud. The Soviet Union was initially very secretive about the disaster, and for the first 33 hours, no one was evacuated. It is unclear how many people ultimately died (likely a number between 250 and 15,000). In 2003, it became known that the sarcophagus placed over the reactor was about to collapse. Between 2012 and 2016, a better sarcophagus was built.