Application of Relap5/Mod3 to the evaluation of loss of feedwater in test facilities and in nuclear plants

Abstract

The present paper deals with the evaluation of the capabilities of the Relap5/Mod3 code (7J version) in simulating the phenomena occurring following the application of an accident management procedure in the case of a loss of feedwater transient in PWR type nuclear plants; the actuation of high pressure injection system is not foreseen in the primary side. The proposed procedure is based upon the intervention of auxiliary feedwater after the occurrence of dryout in the core region. This is a consequence of primary inventory loss from the pressurizer relief valve. Two experiments performed in Lobi and Spes facilities are the reference data base for the activity. Post-test analyses were performed by using the above code to evaluate the differences with respect to Relap5/Mod2 code results as well. Nuclear plant performance was predicted with reference to the same plant scenario.