ICE layer growth on a cryogenic surface in a fusion reactor during a loss of water event

Abstract

The design of fusion devices often includes water as primary coolant of the first wall/blanket system and a potential accident scenario is the steam/water injection from the primary circuit into the magnets' cryogenic chamber (cryostat). An important question to be answered for the above scenario is whether the pressure suppression created by the cryogenic surfaces is sufficient to prevent cryostat damage. The computer codes used for the assessment of ITER safety were validated in the past years against the EVITA (Experimental Vacuum Ingress Test Apparatus) experiment at CEA-Cadarache, which was designed for the simulation of the physical phenomena occurring during a coolant ingress into the cryostat, namely ice formation on a cryogenic structure, heat transfer coefficient between walls and fluid, flashing, two-phase critical flow. The paper presents the results obtained by the CONSEN computer program for seven post-test calculations of the EVITA facility relating to the cryogenic experiments carried out in 2004 and 2005, in which the kinetics of the ice layer formation was analysed. The comparison with the experimental data has been performed and the main agreements and differences are remarked.