LES ACTIVITÉS NUCLÉAIRES : RAYONNEMENTS IONISANTS ET RISQUES POUR LA SANTÉ ET L’ENVIRONNEMENT 4 – New safety challenges and safety objectives to be adapted 1. The period of time during which safety can be maintained without the need for any intervention (for example, the period of time during which, in the event of total loss of all power supplies, safety can be ensured passively until an emergency power source is restored). 2. Studies of passive thermal-hydraulic safety systems. 3. High-temperature reactor. 4. MOX fuel is a nuclear fuel consisting of a mixture of depleted uranium oxide and plutonium. It can currently be used in 24 reactors of 900 MWe. In France, MOX fuel uses only civil plutonium, extracted from irradiated fuel. Whereas the siting of a new power generating reactor is one of the aspects of the project which can to a certain extent be a choice, this is not the case for numerous SMR projects. If the particular target is the industrial heat or district heating production market, then the siting of an SMR is determined by the location of the customer to whom it will be delivering the energy. Furthermore, numerous SMR projects are thus aiming to establish themselves on or near industrial sites, or even within urban areas. Siting near to densely populated areas is being envisaged by the project developers, because these SMRs are likely to be able to achieve safety levels significantly better than those of today’s large power generating reactors. With these SMRs, the low power to be removed in the event of an accident should make it possible to combine passive and active safety systems, leading to increased diversification of the safety provisions, longer grace periods(1) and better protection of the containment barriers. With the PASTIS(2) research project (Passive Systems ThermalHydraulic Investigations for Safety), ASNR is studying the physical phenomena involved in passive safety systems designed to remove residual heat from a light-water reactor during incidents or accidents. The experimental platform was completed in 2025, and trials can begin in 2026. In addition, some of the new technologies proposed have specific characteristics (such as the intrinsic containment performance of the particular fuels of High-Temperature Reactors(3) – HTRs), which also make it possible to envisage a significant reduction in radioactive releases in the event of an accident, even the most severe. Even if these SMRs can in principle achieve safety levels higher than those of high-power electricity generating reactors, ASNR considers that it is necessary to adapt the required safety objectives before envisaging such siting close to population centres. ASNR has therefore launched a study to define the enhanced safety objectives to be set for such installations, taking into account public expectations regarding the safety level of the SMR projects concerned. The results of this study will also feed into the work on harmonising safety objectives being carried out by ASNR alongside its European counterparts within the framework of Western European Nuclear Regulators Association (WENRA). 5 – The need for a vision incorporating the “fuel cycle” The development of these modular reactor projects would appear to be inextricably linked to the availability of the fuel they need in order to operate. This availability refers not only to the existence of industrial production means for the fuels, but also the production capacity (see Table 3). Two SMR project developers have also initiated technical discussions with ASNR on projects to develop fabrication plants for their fuel: ∙Jimmy, concerning a project for a TRISO fuel fabrication plant; ∙Newcleo, concerning a project for a MOX(4) fuel fabrication plant for fast neutron reactors. Apart from the subject of fuel fabrication, ASNR also underlines the need to have the transport systems approved for these fresh and used fuels, and to anticipate the development of technologies for reprocessing and for management of the associated waste. Information on the assessment of SMR fuel fabrication plants is provided in chapter 11 of this report. Technology Current availability of the associated specific fuel Light water reactor • Existing industrial capacity Fast Neutron Reactor, sodium or lead cooled • Industrial production capacity for specific MOX fuels to be developed High-temperature reactor • No industrial production capacity for this particular type of fuel (TRISO)(*) + • Need for uranium enriched to nearly 20% (HALEU)(**) Molten salt reactor • No industrial production capacity for this particular type of fuel (a mixture of uranium and plutonium in chloride salts) • Need for development of capacities for enriching natural chlorine with chlorine-37 to avoid the formation of chlorine-36 TABLE 3 Presentation of technologies and corresponding fuels envisaged for the SMRs * The particle fuel is referred to as “TRISO” for Tri-Structural Isotropic. The kernel consisting of uranium oxide, carbon and oxygen is surrounded by three insulating layers acting as the first containment barrier to retain the fission products. ** HALEU (High-Assay Low-Enriched Uranium) type uranium is enriched to a higher level of the uranium-235 isotope (from 5 to 20%) than the conventional Low Enriched Uranium (LEU) used in the fuel for PWRs. ASNR Report on the state of nuclear safety and radiation protection in France in 2025 315 09 10 11 13 08 12 A / Z 01 05 02 06 03 07 04
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