Accident Risk Associated with Fueled Decommissioned Nuclear Powered Submarines

Abstract

Many nuclear powered submarines have been removed from active duty during the past decade. Common practice when retiring such submarines from active duty is to remove the fuel from the reactor vessel, thereby rendering the submarine relatively harmless, from a radiation risk perspective, to workers, the public and the environment. In Russia, the defueling process is progressing slowly and a large number of inactive submarines are moored, at various sites, with the nuclear propulsion plant still intact, as they await for the reactor to be defueled. This interim stage creates a potential risk to the environment as well as to workers and nearby communities. The assessment of this potential risk was the focus of a recent NATO study on Cross-Border Environmental Problems. This paper addresses the likelihood and magnitude of a radiation release associated with core overheating events. The results of the assessment indicate that the likelihood of a core-overheating event is fairly remote and the radiological consequences, if one did occur, would be contained within the submarine. Furthermore, the analysis has demonstrated that this risk does not exist for first generation submarines, and exists only during the first and possibly the second year of mooring for second-generation submarines. After about one year from reactor shutdown, for first generation submarines, and about three years for second-generation submarines, the decay power is low enough that it can be removed by passive means, even if the reactor vessel is completely drained. Accordingly, it can be concluded that the probability of a significant release, associated with the storage of submarines without prior defueling, is negligibly small.