Source term distribution and mobility – WP3 results of EU project SAMOSAFER

Abstract

The aim of the EU Horizon 2020 founded project SAMOSAFER was to develop and demonstrate new safety barriers and a more controlled behavior in severe accidents of the Molten Salt Reactor (MSR). The aim of work package 3 was to develop and validate models for tracing the nuclides carrying the radiotoxicity and decay heat, i.e. the source term and their chemical form and mobility during nominal and accidental conditions. The source term distribution at the beginning of an accident depends on the foregoing nominal operation mode. Hence, the liquid salt reprocessing and gaseous and insoluble Fission Products (FPs) separation was modeled before the severe accident simulation were accomplished. Because the source term assessment is a complex topic, only selected phenomena were addressed. As a reference system the MSFR concept was adopted from the previous EU project SAMOFAR. The study included benchmarking of the burnup tools, thermal-hydraulics simulations to confirm the removal rates to the off-gas system. Chemical experiments and calculations of the methods used in the reprocessing unit, simulation of severe accident conditions and finally calculation of the source term distribution. The major outcomes are the benchmark for the nuclide inventory tracing tools, application of multi-physics tools on He-bubbling for gaseous and solid FPs removal rates simulations, refinement of the reprocessing scheme, and first simulation of simplified severe accident.