CFD modelling of the CIRCE facility

•Full 3D CFD models of the primary system of the CIRCE facility.•Good match for both nominal and transient conditions with experimental data.•Modelling conjugate heat transfer necessary to reproduce stratification.•Provides valuable information towards CFD modelling of nuclear reactors. CIRCE is a test facility designed and realized by the Italian agency ENEA to support the heavy liquid metal technology for nuclear fission plants. Within the H2020 projects SESAME and MYRTE, various experiments are performed in this facility, using two different heat exchangers (namely ICE and HERO), resembling nominal operation and accident scenarios of a Liquid Metal Fast Reactor (LMFR). Simultaneously, within these projects different thermal-hydraulics models of CIRCE are created to gain experience in the modelling of such a facility and to help future development of LMFRs. At NRG and CRS4, CFD models of CIRCE in the two different configurations are created. The present paper describes the steps taken to create these models. Results obtained with the models are, where possible, compared with experimental results, both for steady-state and transient conditions. For the steady-states, generally good agreement is found. The main features of the stratification forming in the pool are recovered, though they appear quite sensitive to the local heat balance. The transient simulation performed recovers some of the main features of the experiment, however excessive cooling is found. The causes of discrepancies found between numerical and experimental results are currently under investigation.