Assessment of two wall film condensation models of RELAP5/MOD3.2 in the presence of noncondensable gas in a vertical tube

The objective of the present work is to assess the analysis capability of two wall film condensation models, the default and the alternative models, of RELAP5/MOD3.2 on condensation experiments in the presence of noncondensable gas in a vertical tube of PCCS of CP-1300. In the calculation of a base case the default model of RELAP5/MOD3.2 under predicts the heat transfer coefficients, and its alternative model over-predicts them throughout the condensing tube. Also, both models over-predict the void fractions. The nodalization study shows that the variation of the node number does not change both modeling results of RELAP5/MOD3.2. Sensitivity study for varying input parameters shows that the inlet steam-air mixture flow rate, the inlet air mass fraction, and the inlet saturated steam temperature give significant changes of their heat transfer coefficients. Run statistics show that the grind time of the default model is always higher than that of the alternative model by about 23 percent. (author)