Analyses of Diagnostic Failure Effect and Fail-Safe Ignited Operation in a Tokamak Fusion Reactor

The consequence of the failure effect of burn control diagnostic systems, such as neutron diagnostics, bolometers, electron cyclotron emission power loss diagnostics, interferometer, and lost alpha detector, on ignited operation has been analyzed, and the fail-safe operation in a tokamak fusion reactor including the International Thermonuclear Experimental Reactor (ITER) has been considered. Because the failure of the neutron diagnostic system for fusion power measurement leads to a fusion power surge for the simple control algorithm, the fail-safe control algorithm has been introduced to avoid this problem. As failure of the power loss measurement such as the bolometer system terminates the ignition, then it is less problematic. The effect of the interferometer fringe counting error on the ignited operation is not simple, as just mentioned, and a lost alpha detector can be removed from the feedback system using the preset value.