Analysis of External Radioactive Releases for an In-Vessel Break in the Power Plant Conceptual Study Using the ECART Code

This work is related to the application of the CESI and EdF ECART code on the analysis of the tritium and dusts external releases for an in-vessel break in the helium cooling loop of the first wall / blanket for the Power Plant Conceptual Study (PPCS). In particular the influence on the releases of a Detritiation System (DS) and of a dust scrubber with constant decontamination factor, not implemented in the original PPCS design, are analysed. Furthermore, some parametrical analysis on the influence, on the external releases, of the mass fraction of dust resuspended inside the VV at the beginning of the sequence have been also performed. These analyses are the follow-up of a previous DIMNP study about the phenomenological behaviour of the PPCS containment (vacuum vessel walls and expansion volume walls), giving the first indications on the amount of the external radioactive releases. The activities have been also carried out in the general framework of the validation phase of the ECART code, initially developed for integrated analysis of severe accidents in LWRs, for its application on incidental sequences related to fusion plants. ECART was originally designed and validated for safety analyses of fission NPPs and is internationally recognized as a relevant nuclear source term code for these fission plants. It permits the simulation of chemical reactions and transport of radioactive gases and aerosols under two-phase flow transients in generic flow systems, using a built-in thermal-hydraulic model.