A SAFETY ANALYSIS OF THE ITER SUPERCONDUCTING MAGNET SYSTEM IN CASE OF LOSS OF VACUUM IN THE ITER CRYOSTAT

One of the safety analysis for superconducting magnet system in Intern ational Thermonuclear Experimental Reactor (ITER) was carried out. The ITER cryostat will hold many superconducting magnets, such as twenty of toroidal field coils, a central solenoid coil, and seven poloidal c oils. Loss of vacuum of the cryostat was considered as the worst assum ption and the safety analysis of the magnets was examined when the ass umption would be occurred. Accordingly, the loss of vacuum will cause the loss of thermal shield vacuum for the magnets and then a large hea t transfer will be generated in the cryostat The magnet pressure and t emperature will rise, bringing the magnets to quench. Such behavior wa s simulated by using a developed computer-aided calculation code. As a result of the calculation, a catastrophic phenomenon doesn't appear i n the assumption. It is observed that a quasi-stable state, where the magnet temperature is kept to be less than 7 K,is maintained for more than 600 seconds. Thus, the magnet current can be slowly discharged li ke as the ordinal operation without magnet quench even in such worst a ssumption due to a large volume of the cryostat.