SAFETY ANALYSIS RESULTS FOR CRYOSTAT INGRESS ACCIDENTS IN ITER

Accidents involving the ingress of air, helium, or water into the cryo stat of the International Thermonuclear Experimental Reactor (ITER) to kamak design have been analyzed with a modified version of the MELCOR code for the ITER Non-site Specific Safety Report (NSSR-1). The air in gress accident is the result of a postulated breach of the cryostat bo undary into an adjoining room. MELCOR results for this accident demons trate that the condensed air mass and increased heat loads are not a m agnet safety concern, but that the partial vacuum in the adjoining roo m must be accommodated in the building design. The water ingress accid ent is the result of a postulated magnet are that results in melting o f a Primary Heat Transport System (PHTS) coolant pipe, discharging PHT S water and PHTS water activated corrosion products and HTO into the c ryostat. MELCOR results for this accident demonstrate that the condens ed water mass and increased heat loads are not a magnet safety concern , that the cryostat pressure remains below design limits, and that the corrosion product and HTO releases are well within the ITER release l imits.