- 227 - In the case of facilities other than the reactors operated by EDF, the safety frame of reference to consider for the compliance review is made up of the common provisions (fundamental safety rule, ministerial orders in particular) and measures specific to the facilities (general operating rules, safety report). The following paragraphs thus specify for each facility the safety frame of reference considered for the compliance evaluation. To assess the robustness of the facilities, the licensees have identified for each facility their margins with regard to the design dimensioning, taking hazard levels that go beyond the scenarios considered up until now. Moreover, ASN has asked for the identification of a hard core of reinforced material and organisational provisions whose availability must be guaranteed under extreme conditions in order to prevent or manage a severe accident. As this notion was only introduced during the examination of the CSA reports, ASN will ask the licensees to provide it with additional information. ASN will thus ask all the licensees to define a hard core of reinforced material and organisational provisions for the extreme situations analysed in the CSAs, with the aim of: preventing or mitigating a severe accident; limiting massive releases in an uncontrollable accident scenario; enabling the licensee to fulfil the emergency management duties incumbent upon it. The licensee must submit the requirements applicable to this hard core to ASN for approval. To define these requirements the licensees are asked to adopt significant fixed margins with respect to the current safety frame of reference (for earthquakes for example, fundamental safety rule No.2001-01, the state-ofthe-art paraseismic rules, and the constructive measures of ASN guide 2-01). The systems, structures and components (SSC) that form part of these provisions must be kept functional in the extreme situations studied in the CSAs. More particularly, these SSCs shall be protected against internal and external hazards induced by these extreme situations, such as falling loads, impacts from other components and structures, fire and explosions. For the implementation of these provisions, the licensees are asked to favour the addition of independent and diversified SSCs whenever possible, in order to limit common mode risks. 1.3.2. Identification of the feared situations Experimental reactors Reactors operated by the CEA The JHR and Osiris facilities The feared situations or "degraded states" in CEA terminology considered consist in the meltdown under water or in air of irradiated fuel elements with associated loss of containment. In the case of the JHR, the CEA also considers the situation corresponding to a criticality accident in case of loss of storage geometry. The CEA identifies the following key core cooling equipment items to prevent these feared situations: in the short and medium term: o for the Osiris facility, the reactor emergency shutdown system and the natural convection valves; o for the JHR facility, the reactor emergency shutdown system, the mixing pump installed on train 3 of the primary cooling system and its set of electrical power supply batteries SUS B, the natural convection valves and their set of electrical power supply batteries SUS A ; in the long term: o the pools connected to the reactor and their sealing system.
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