RELAP5/MOD2 pressurizer modeling

The objective of this paper is to present the RELAP5/MOD2 models for describing repressurization transients and to report the developmental assessment results obtained through simulation of several separate effects experiments. RELAP5/MOD2 is a new version of the RELAP5 thermal-hydraulic computer code and contains improved modeling features, which provide a generic pressurized water reactor transient simulation capability. In particular, the nonequilibrium capability has been generalized to include repressurization transients in which subcooled liquid and superheated vapor may coexist in the pressurizer and/or other locations in the primary coolant system. The assessment shows that RELAP5/MOD2 calculated results are in good agreement with data and the nonequilibrium phenomena for repressurization transients are properly modeled.