- 226 - The technical specifications for the European stress tests were defined for power reactors with regard to the severe accidents that could affect them and lead to cliff-edge effects. The specifications that ASN prescribed to the licensees in its decisions of 5 May 2011 apply to all the nuclear facilities. Two types of facility have thus been considered: the nuclear power reactors and experimental reactors on the one hand, and the other facilities on the other hand. The CSA reports include a descriptive section for each facility, specifying: For the nuclear power reactors and experimental reactors: the type of reactor (including the radiological inventory, the nature of the fuel and its enrichment, the nature of the moderator and the coolant, the characteristics and state of the containment vessel) ; the thermal power; the date of the first divergence; the existence and number of new or spent fuel storage areas (or shared storage areas); the specific features of the various installations that are important for safety. For the other nuclear facilities: the type of facility; the activities (nuclear, chemical, biological), including waste or fuel storage, with the maximum authorised inventory; the authorised inventories for radioactive material and chemicals, with their characteristics, particularly type and form; the specific risks (nuclear and chemical risks in particular): criticality, irradiation, risk of explosion, fire, etc. For the other facilities, the licensees have defined the nature of the severe accidents they consider could lead to cliff-edge effects. These severe accidents or feared situations are specified for each facility in the CSAs. Some are not related solely to the nuclear risk, particularly in the case of fuel cycle facilities, for which the severe accidents are closely related to the chemical risk. The following elements have thus been examined in particular: For the nuclear power reactors and experimental reactors: loss of the core cooling function; loss of the cooling function of fuel stored dry or under water; loss of containment integrity, and reactor containment in particular. For the other nuclear facilities: loss of the cooling function; loss of radioactive or hazardous product containment; loss of the means of controlling explosion risks, particularly hydrogen explosion; loss of the means of preventing criticality risks; loss of fire-fighting means. The procedure adopted for the CSAs thus consisted in examining two main points: conformity of the facility with respect to its safety frame of reference, defined according to its design and any past periodic safety assessments; the robustness of the facilities beyond its design-basis hazard levels and evaluation of the corresponding margins; key systems, structures and components (SSC) have thus been identified in order to make a targeted evaluation of robustness to the feared situations.
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