Advances on LWRs Plutonium Multi-recycling Solutions - 23362

The paper discusses the R and D program launched in France to assess multi-recycling of plutonium solutions in next generation of LWRs (Light Water reactors) enabling to recycling all types of used fuel including MOX used fuel while maintaining flexibility to implement closed fuel cycle with fast neutron reactors (FNRs) at the end of the century. The French fuel cycle currently implements the mono-recycling of reusable from used fuels based on enriched natural uranium (ENU) stored and reprocessed at Orano's La Hague site. Fuel recycling technologies are industrially implemented in France, where both plutonium and uranium from used uranium fuel are recycled in LWR fleet. Nowadays the nuclear power plants operating with a sizeable portion of MOX fuel have the same performances in terms of energy production and reliability as those using UO₂ fuel cycles. Then, the used MOX fuel assemblies are stored and considered as a stockpile of nuclear materials for future use. Indeed, a significant energy is still available in MOX fuel even after being irradiated in LWRs. Since 2018, the French government has adapted its mid-term energy management policy, introducing a milestone to demonstrate the industrial feasibility of the plutonium multi-recycling in LWRs, with an objective of industrial commissioning deemed feasible in the 2040's, while preserving the capability to introduce a Fast Neutron Reactor fleet in late 21. century. The multiple recycling of plutonium in LWRs requires the development of new fuel technologies (MOX2), considering the overall system reactor/fuel cycle and waste management of such an option. The following issues need to be considered when studying these solutions: - Plutonium management strategies should be consistent in maintaining high standards of safety. The requirements of nuclear safety in relation to the reactor physics properties of the various reactor systems are relevant, which includes guaranteeing sufficient shutdown margins in all reactor operating situations and sub-criticality during core loading, unloading and fuel handling operations. - Plutonium management strategies should maintain flexibility in the fuel cycle, such that future options like fast reactors development are not foreclosed. - Plutonium management strategies should be consistent with maintaining standards of security and safeguards against proliferation. The main difference regarding the multi recycled plutonium fuel, MOX2, compared with current MOX fuel is that the isotopic composition may change significantly (decrease of the fissile isotopes content) along the multi-recycling process. In order to reach discharge burnup similar to the current fuel assemblies' levels, considering the limitation of plutonium content, an additional fissile content (enriched uranium) should be provided. The enriched uranium could be either located in the MOX2 fuel pellet (also known as MIX fuels) and/or in other UO₂ fuel assemblies when considering MOX2/UO₂ mixed cores. The isotopic quality of Pu available for reloading is driven by the assumptions on the fuel cycle strategy including mixing plutonium separated when reprocessing different spent fuel types. Innovative fuel concepts developed to offer advanced cycles improving the use of available Pu resources have been assessed regarding the reactor implementation feasibility and the industrial performances. In addition, the French LWR multi-recycling project aims at developing a competitive complete system that meets the objectives in terms of safety, technical, economic, and environmental performances. This will enable to value this fuel cycle option in comparison to current mono-recycling fuel cycle integrating risk mitigation and offered flexibility towards enhanced circular economy while reducing environmental impact. (authors)