Modeling of the interfacial shear in the 3D momentum equations of TRAC-BF1

In the vessel component, TRAC-BF1 solves the three-dimensional (3D) two-fluid model conservation equations. However, the way the interfacial shear is treated when the 3D phasic momentum equations are finite-differenced appears to be incorrect. In this work, we shall outline the way the 3D phasic momentum equations are finite-differenced and the interfacial shear term is treated, the way we modified it and brought it into the right form and finally, we shall demonstrate by analyzing a TLTA LB-LOCA test and two hypothetical LB-LOCAs in a BWR/4 the way that the code predictions are affected by this modification.