Application and Validation of ASTEC Code in the Analysis of Fission Product Release and Transport Processes Taking Place in the Phébus and the STORM Facilities

This paper presents an overview of the activities carried out in the framework of the SARNET project by the CIEMAT, INR, JRC/IE, GRS, UJV, and VUJE partners involved in the validation of ASTEC on fission product (FP) release and transport experiments simulating severe accident conditions in the reactor circuit and containment.

These activities were mainly devoted to the analysis of the Phébus experiments, FPT0, FPT1, and FPT2, which provided fundamental reference data for the severe accident research. The ELSA, SOPHAEROS, CPA, and IODE modules were used for FP release from the bundle, transport in the circuit, containment thermal hydraulics and aerosol behavior, and iodine behavior in containment, respectively. Studies on aerosol behavior in the STORM experiments and iodine behavior in the ThAI experiments are also summarized.

The paper describes not only the results of validation of some stand-alone or several coupled code modules but also the results of first integral calculations, when all the relevant modules of the ASTEC code were used to model the FP release and transport. In the integral calculations, no boundary conditions are to be defined by the code users for most of the code modules, but only at such interfaces were the boundary conditions applied in the experiment. The integral calculation allows more objective judgment about the combined uncertainties of the calculated results.

Together with overview of the progress in the validation of the main ASTEC modules, this paper also points out what needs to be improved in the modeling of future ASTEC V2 code versions.