Thermal Hydraulic Investigation of the CIRCE-THETIS Facility by the use of STH and CFD Codes

The aim of this work is to investigate possible thermal stratification phenomena inside the CIRCE-THETIS facility by mean of both STH and CFD codes. Codes capabilities were firstly evaluated by simulating the previous CIRCE-HERO configuration with both RELAP5-3D and ANSYS Fluent codes and comparing the numerical results with the available experimental data. This benchmark also worked as a validation process allowing to understand the capabilities of the RELAP5-3D STH code in dealing with large 3D domains. The results by RELAP5-3D and ANSYS Fluent showed a good agreement with experimental data and thus pre-Tests simulations were performed adopting the selected codes for the CIRCE-THETIS facility, too. Results provided by the two codes are discussed deeply both highlighting weaknesses and capabilities of the adopted modelling techniques