Soviet icebreaker Lenin Winter 1966-1967 meltdown

In the Soviet Union's Winter 1966-1967there was a loss of coolant on the Soviet icebreaker Lenin, the USSR’s first nuclear-powered surface ship, suffered a major accident (possibly a meltdown — exactly what happened remains a matter of controversy in the West) in one of its three reactors. To find the leak the crew broke through the concrete and steel radiation shield with sledgehammers, causing irreparable damage. It was rumored that around 30 of the crew were killed. The ship was abandoned for a year to allow radiation levels to drop before the three reactors were removed, to be dumped into the Tsivolko Fjord on the Kara Sea, along with 60% of the fuel elements packed in a separate container. The reactors were replaced with two new ones, and the ship reentered service in 1970, serving until 1989.

It dose not have an offical INES rating, but was probably a 3 or 4.


 * ''Sources: https://en.wikipedia.org/wiki/List_of_civilian_nuclear_accidents and https://www.wikiwand.com/en/List_of_civilian_radiation_accidents