Timeline of the Fukushima nuclear accidents happened in 2011.

If your asking about the Chernobyl nuclear accident. It was April 26th, 1986. Here is a list of nuclear accidents around the world. http://www.atomicarchive.com/Reports/Japan/Accidents.shtml

28

Between 1945 and 1987, there were 285 nuclear reactor accidents, injuring over 1,550 people and killing 64.

As in a civilian factory, all military accidents or potential accidents (near miss) should be written in the Accident Book, and investigated.