CRYOSTAT PRESSURIZATION IN ITER DURING AN EX-VESSEL LOSS-OF-COOLANT ACCIDENT SEQUENCE

The paper analyses the pressurization of the ITER cryostat during an e x-vessel loss of coolant accident (LOCA) in the first wall-shielding b lanket (FW-SB) primary cooling loop. Since the cryostat is a strong ba rrier against the release of mobilized hazardous material, its integri ty is essential in meeting the ITER safety objectives, The analyses re fer to ITER TAC 4 design and were performed by means of a Fast running thermal fluid dynamic code that allowed parametric studies, Helium LO CA can be handled by the code, so that the analyses did take into acco unt phenomena such as coil quench and electrical arcing between coil t urns, that may occur in tokamaks with superconducting cables in the ma gnet coils. The main result was that even in the worst conditions the pressure transient in the cryostat does not damage its integrity provi ded that the plasma facing components (PFC) cooling loops in the vacuu m vessel remain undamaged. Hence, if no other energy sources than thos e coming from an ex-vessel LOCA are added to water, helium and heat st ructures in the cryostat, the cryostat maintains its integrity. More a nalyses are needed to evaluate an in-vessel LOCA and the consequent cr yostat pressurization transient. In fact this event would add decay he at and exothermic chemical reaction as energy sources eo be possibly t aken into account in the pressurization transient. These analyses are not within the scope of this work, (C) 1998 Elsevier Science S.A.