K-11 was a Soviet November-class (Project 627A) nuclear-powered attack submarine that had two reactor accidents during loading of the nuclear reactor core in Severodvinsk on 7 and 12 February 1965. Reasons for the accidents included nonobservance of operating instructions by those participating in the lift of the reactor cover and the mistaken decision to continue refueling after the first accident. There were no fatalities but those accidents (ejection of radioactive steam and inappropriate fire extinguishing methods on 12 February) caused an unsafe release of radiation into the environment and nearby shipyard area. Seven men were treated for exposure to radiation. The reactor compartment holding the two damaged reactors was removed, partially decontaminated and sunk in Abrosimov Bay (eas