Development and application of CFD and subchannel coupling analysis code for lead‐cooled fast reactor

Abstract

It is of necessity and importance for the simulation of the three-dimensional thermal hydraulics problem of the pool type fast reactor. However, because of current computing power limitations and the complexity of the reactor core structure, for conventional reactor applications, it is still not possible to directly simulate the entire reactor flow with sufficient fine meshes for detailed pin geometry. Until now, there is a multiscale coupling method which is suitable to deal with this type of simulation challenge. Through the user-defined function (UDF) of FLUENT, the coupling code FLUENT/KMC-sub for thermal hydraulic (TH) analysis by coupling the dynamic link library (DLL) complied by the transient subchannel code KMC-sub is developed by University of Science and Technology of China (USTC). As a code validation case, the steady-state simulation of a 19-rod assembly has been carried out by using coupling codes of FLUENT/KMC-sub, FLUENT and KMC-sub, and consequently good consistency has been achieved by comparison with experiment results. And coupled code is further tested by comparison with the transient-state 19-pin assembly test results of KMC-sub and FLUENT simulation. This coupling code is then used for TH of M2LFR-1000 (medium-size modular lead-cooled fast reactor) in unprotected loss of flow (ULOF) accident. The transient temperatures of coolant and fuel and multidimensional TH phenomena and safety analysis are presented and discussed in this article.