Ultimate strength and rupture modes for metal containment system type Mark III under pressure load

In the last few years, in particular, the analysis of the containment of NPP's has been developed including also severe accident conditions, supposing the unavailability of the emergency cooling systems, the core melting and subsequent possible break through the RPV, the ablation of basemat and the heating and pressurization of the containment atmosphere. Owing to the pressure and temperature transients associated with severe accidents scenarios, leaks of radioactive materials could occur from piping penetrations, relief valves, air locks, geometrical discontinuities in general, well before the ultimate pressure is reached and catastrophic rupture expected. In this paper the limit pressure to produce wide plastic flow and the impact of a crack on the integrity of the BWR containment vessel, type MARK III, have been assessed