The EASI-SMR project intends to address the safety issues related to the LW-SMR in order to provide advances that should support implementation of such technologies as soon as possible. The EASI SMR project activities are aimed at ensuring that these reactors will be designed, constructed, commissioned and operated in the safest possible way and in accordance with existing regulations. The consortium was carefully chosen so that the research entities can provide the necessary research teams and support facilities across the European Continent and beyond. EASI-SMR will address the safety issues associated with major LW-SMR innovations: • Passive systems • Soluble Boron-free cores • Co-generation and hybridation • Additive manufacturing to improve compactness of Nuclear Steam Supply System • Multi-units operation The work aims to provide insights for European LW-SMR projects, in particular: • NUWARD SMR, a French design of a reactor generating 170 MW of electricity production. • LDR-50, a Finnish design of a district heating reactor of 50 MW EASI-SMR is closely linked with NUGENIA TA6 and the European SMR pre-Partnership’s WS5.

Increasing further the safety of light water nuclear reactors in the new operating conditions induced by their integration in a more varied energy mix brings many new challenges for fuel development. This calls for effective and validated tools enabling one to capture the complexity of the behaviour of fuel elements under various operation conditions from nominal to design basis accident ones.. The objective of the OperaHPC proposal is to develop open tools using High Performance Computing (HPC) enabling a full 3D high-fidelity thermo-mechanical simulation of the fuel element including the material microstructure. This will contribute to the design of so-called fuel element digital twins. This development includes an ambitious basic research program devoted to the investigation of non-linear mechanical behaviour of irradiated fuel using multiscale experiments and simulations from the atomic scale up to the material law. This will yield the detailed description of the in-pile behaviour of the fuel element and the materials data necessary for the simulation. The tools developed will be assessed against state-of-the-art 1D/3D fuel performance codes for verification, definition of boundary conditions and coupling with neutronic, thermochemical and thermohydraulic codes. Validation and uncertainty analyses will also be performed through the comparison of the results of the 3D simulations with the experimental data available from irradiation programs. The knowledge from these advanced simulations will be transferred to industrial fuel performance codes thanks to the application of new methods based on reduced order and meta models, including Artificial Intelligence. The HPC tools will finally be applied to the detailed evaluation of innovative fuel element concepts, including (enhanced) accident tolerant fuels, under transient conditions in several light water reactor designs.

In the current state of maturity of severe accident codes in terms of phenomena addressed and extensive validation conducted, the time has come to foster BEPU,Best Estimate Plus Uncertainties, application in the severe accident (SA) domain, and accident management (AM). The advantages with respect to deterministic analysis are known: avoid adopting conservative assumptions in the model and allow identifying safety margins, quantify likelihood of reaching specific values and, through the distribution variance provide insights into dominating uncertain parameters.The overall objective of the Management and Uncertainties of Severe Accident (MUSA) project is to assess the capability of SA codes when modelling reactor and SFP (Spent Fuel Pool) accident scenarios of Gen II and III. To do so UQ (Uncertainty Quantification) methods are to be used, with emphasis on the effect of already-set and innovative accident management measures on accident unfolding, particularly those related to ST (Source Term) mitigation. Therefore, ST related Figures Of Merit (FOM) are to be used in the UQ application. The MUSA project proposes an innovative research agenda in order to move forward the predictive capability of SA analysis codes by combining them with the best available/improved UQ tools and embedding accident management as an intrinsic aspect of SA analyses.MUSA develops through key activities which also describe the main outcomes foreseen from the project: identification and quantification of uncertainty sources in SA analyses; review and adaptation of UQ methods; and testing such methods against reactor and SFP accident analyses, including AM. Given the focus of FOM on source term, the project will identify variables governing ST uncertainties that would be worth investigating further. All the ingredients necessary to conduct the project are already available: analytical tools, experimental data, postulated reactor and SFP scenarios and, technical and scientific competences.

The Reduction of Radiological Consequences of design basis and extension Accidents (R2CA) project targets the development of harmonized methodologies and innovative management approach and safety devices for the evaluation and for the reduction of the consequences of DBA and DEC-A accidents in operating and foreseen nuclear power plants in Europe. For both purposes development of methodologies will be conducted with the goal of reassessing the safety margins using less conservative approaches and considering the new risks that rose from the original design or design extension phases. This will reinforce the confidence on these safety margins for conditions up to the extended design domain, will allow the identification of new accident management measures and devices and will support the optimization of the potential associated emergency population protection measures. Improvement of evaluations tools will be supported by the reassessment of the existing experimental and analytical databases. The efficiency of the approach will be demonstrated by comparing at start and then at the end of the project the results of the evaluation of a series of reactor cases selected by a senior expert group among two main categories: loss of coolant accidents and steam generator tube rupture accidents. Detailed analyzes of these reactor cases simulations will suggest the development of harmonized evaluation methodologies. The project will include also innovative actions to estimate the pros and cons of potential new accident management measures and devices, to explore the potential switch of prognosis evaluation tools to the diagnosis of on-going fuel cladding failure and to explore the potentiality for these accidental situations of advanced technological fuels.