Benchmark calculation for spills of cryogenic He into the ITER VV used as basis for an experimental campaign by means of EVITA facility

Code validation activities have been promoted inside the EFDA (European Fusion Development Agreement) to test the capability of codes in simulating accident phenomena in fusion facilities and, specifically, in the ITER (International Thermonuclear Experimental Reactor) plant. This work concerns a benchmark between three different computer codes (CONSEN, MAGS and MELCOR) and one analytical model (ITER model) in simulating cryogenic helium leaking into a vacuum vessel (VV) which contains hot structures. The scope is the evaluation of the transient pressure inside the VV. The results will be used to design a vent duct (equivalent diameter, length and roughness) which allows helium pressure relief towards controlled volumes. A maximum pressure of 2.0e5 Pa inside the vacuum vessel is allowed during the accident transient. The reference geometry is a simplified scheme preserving the main features of the full scale ITER design. Based on the results of the simulations, a matrix of experiments will be proposed to validate the calculated results and to design the vent duct for the ITER VV. The experiments are planned to be performed in the EVITA facility, located in CEA Cadarache (France).