Under the auspices of the International Energy Agency (IEA) the conceptual design of an accelerator-based (D-Li) neutron irradiation facility to test and qualify fusion reactor materials has been completed at the end of 1996 by an international design team. A review of the conceptual design oriented to reduce technical risks and to complete the database for an engineering design has been recommended by IEA and is presently in progress. In the frame of this Conceptual Design Evaluation (CDE) phase (1997-98), an activity aimed at deeping the safety analysis of the Li-target system has been carried out. An integrated safety analysis methodology has been developed in order to identify and quantify the specific events that could occur during the operation and could cause environmental hazards. This methodology includes: 1) Safety analysis of lithium target system and its support systems: this analysis has been performed to identify the relevant target related hazards and the major initiating events of accident sequences; 2) Dependent failure analysis, which has been finalised to investigate all failures that could increase the unavailabilities of a function; 3) Accident sequence analysis, which has been fulfilled to identify and quantify the accident sequences that could occur during normal plant operation. With relation to the probabilistic evaluation of the accident sequences concerning the target facility and the support/interfacing systems the methodology and the calculation tool adopted are respectively the fault tree and event tree technique, widely utilized in PRA (Probabilistic Risk Assessment) studies, and the RISK SPECTRUM code, a PC software package for system risk and reliability analysis. The results obtained from the probabilistic evaluation indicate that the frequencies/probabilities of occurrence of the most dangerous accident sequences, i.e. involving the backwall rupture, are very low.
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