Risk analysis for ITER divertor system

The authors describe a safety study performed on some design solutions for the divertor of ITER (International Thermonuclear Experimental Reactor). The event tree technique is used to delineate the accident scenarios and to outline reference (or critical) accident sequences. Common features of the solutions considered are double null magnetic configuration, with upper and lower divertor plates, water as primary coolant, separate and independent cooling loops for the divertor and the first wall, carbon-based protective tiles for the physics phase, and tungsten tiles for the technology phase. Fault trees are used to evaluate the occurrence rate of the initiating events and the unavailability of the different event tree headings (i.e., the protective systems, both passive and active). Deterministic safety studies have been considered, where applicable, to describe the phenomenology of the accident sequences and then to estimate the environmental radioactive releases. Consequences are evaluated in terms of doses to the maximum exposed individual of the public for instantaneous releases