Safety classification of the ITER fusion power shutdown system and resulting safety requirements

The paper presents an application of a new safety classification approach, which is founded upon the Lines of Defence (LODs) method for the organisation of the plant safety architecture needed to assure the confinement of radioactive materials and, therefore, to meet the general safety objectives. The International Thermonuclear Experimental Reactor-Fusion Power Shutdown System (ITER-FPSS) was the system selected for the application because of its fusion-specific character. The performed application substantially confirms the level of safety importance classification (SIC) assigned to the FPSS by the ITER team (SIC level 3). A set of safety requirements, concerning aspects of reliability and performance, has been defined for the FPSS. These requirements integrate and specify, for the FPSS, the generic implications currently imposed by the ITER team on the safety systems classified SIC-3. Some FPSS design specifications are also suggested to address the burden of proof requested to justify that its safety requirements can be met by the design and can be maintained over the life-time of ITER.