Evaluation of a Mark I Containment System Under Severe Accident Pressurization

Abstract

The Mark I containment system of the Santa Marfa de Garofta nuclear power plant is presently being evaluated for a specified set of severe accident conditions. The goals are to establish a best estimate of the pressure capacity of the containment structure and to identify the most likely failure location. First of all, global analyses of the drywell and suppression chamber shells have been carried out in order to capture the overall response of the structure and to determine upper bounds for their ultimate capacity. The global analyses have supplied appropriate boundary conditions for several detail analyses and functionality checks (typical penetrations, airlocks, expansion bellows, drywell head flange...) that, together with the global resu1ts, are considered to give a good estimate for the capacity of the containment system. The results obtained up to date show that the weakest points of the system are the expansion bellows connecting the vent lines to the suppression chamber shell, with that exception, the rest of the structure supports 2.5 times the design pressure of 0.43 MPa.