Simulation of two-region and four-region models for typical PWR pressurizer and benchmark obtained results using available results

In light water pressurized reactors, pressurizer plays an important role in controlling the coolant pressure during in-surge or out-surge transients. Increase and decrease coolant mass flow rate or specific volume leads to in-surge or out-surge transient, which changes pressurizer tank's pressure. There are different thermodynamic models, which are predicted the pressurizer surge tank's pressure, water and vapor properties in different times. In the present article, two-region and four-region thermodynamic models were used for simulation of typical PWR pressurizer and the calculated results were benchmarked with RELAP5/Mod3 code findings. Finite difference method is applying to differential equations' analytical solving. Water and vapor thermodynamic properties are calculating according to IAPWS-IF97 (International Association for the Properties of Water and Steam) correlations in each time steps. Try and error method is using for pressure estimations. The pressure results are compared and show that accuracy of the presented models are acceptable and deviations from RELAP code results are justifiable.