Posted in Web Chernobyl Disaster: The Meltdown by the Minute – HISTORY April 29, 2019 April 25, 1986, 1 a.m.: Chernobyl’s operators begin reducing power at reactor No. 4 in preparation for a safety test, which they have timed to coincide with a routine shutdown for maintenance … : https://www.history.com/news/chernobyl-disaster-timeline