Multi-phase flow topology and interfacial area model for SIMMER-III and SIMMER-IV

Tobita, Yoshiharu*; Kondo, Satoru; Morita, Koji*

The multi-component, multi-phase flow topology and interfacial area model has been developed for the SIMMER-III and SIMMER-IV computer codes, which have been extensively used in liquid-metal fast reactor core-disruptive accident analyses. To systematically simulate complex flow topology, flow regime maps are modeled, for both the pool flow and channel flow regimes, with smooth transition between flow regimes. The interfacial area convection model was formulated to enhance the applicability and flexibility of the codes, by tracing the transport and history of interfaces, and thereby better representing transient physical phenomena. The changes of interfacial areas resulting from such as breakup, coalescence, and production of droplets or bubbles were treated as source terms in the interfacial area convection equation. In a multi-component system of SIMMER-III and SIMMER-IV, all the possible contacts between components are taken into account, and the fluid-to-fluid and fluid-to-structure binary contact areas are prepared for the calculations of heat and mass transfer processes and momentum-exchange functions. The multi-phase flow topology and interfacial area model developed in this study was the first of a kind as a fast reactor safety analysis code. The model has been extensively tested through the code assessment (verification and validation) program, which has demonstrated that many of the problems associated with simplistic modeling in the previous codes were resolved.