LAUSR

Abstract Critical flow has significant impact on the reactor safety. Critical flow models are considered as an important module in all system thermal–hydraulic (STH) codes, with several optional models. But each model has its own scope of application. Consequently, the STH simulation results largely dependent on the model choice, i.e. on the user effect. A full-range critical flow model may be used to deal with this issue. The aim of this work was to develop a full-range 6-equation critical flow model with higher accuracy and plug it into ATHLET. The model was validated in Henry tests. The results show that the new model could predict mostly within the error band ±20%, better than other models of ATHLET. To verify the ability of ATHLET with the new model, it was applied to several Marviken full scale critical flow tests in transient, showing better (or at least comparable) results than before.