Reliability and safety analysis of magnet system for a NET type machine

As part of a general safety study of a NET (Next European Torus)-type machine, the magnet system has been analyzed in order to identify all the malfunctions which may initiate accident sequences in the plant. The analysis addresses both toroidal and poloidal coils (including control coils). The main functions of each magnet subsystem are defined through a functional analysis. Based on this, an FMEA (failure made and effects analysis) has been done to identify the possible failures and related consequences for plant safety. The initiating events which have been identified are toroidal field and poloidal field coil quench, arcing due to coil damage, loss of power to some coils, LOCA (loss-of-coolant accident) in helium pipes, and poloidal field and toroidal field coil break. An event tree has been developed for each one of the initiating events, having mitigating features as headings and plant status classes with related frequencies as outcomes. A preliminary evaluation of the releases related to each accident class has been performed. Remarks and preliminary recommendations on system design are reported