Periodic Reporting for period 1 - OperaHPC (OPEn HPC theRmomechanical tools for the development of eAtf fuels)
Okres sprawozdawczy: 2022-11-01 do 2024-04-30
Electrification of the energy sector will be a key step for its transition to climate-neutrality. In order to achieve it by 2050, it will be necessary to maintain and even extend the production capacity of current nuclear reactors, while taking into account the evolving electricity mix and increasing requirements regarding the safety assessment of nuclear reactors. On these points, the question of nuclear fuel behaviour is essential because it sets the main constraints to be satisfied for safe operation of nuclear reactors and defines the source term for accidental conditions.
Generation II and III reactor fuels in Europe take advantage of a large experimental feedback with a continuous evolution of fuel element design and materials, which allows maintaining high safety standards while adapting to the evolution of the operating conditions. Fuel performance codes, which enable the simulation of the behaviour of the fuel elements in reactor, are an essential component of the design, licensing and safety assessment of nuclear fuels. The licensing of innovative materials and fuel design requires an extension of the industrial fuel performance codes qualification in order to meet safety authority’s requirement regarding the Verification, Validation and Uncertainties Quantification process.
To address this question, the OperaHPC project will work on advanced simulation tools enabling 3D representation of the fuel rod, including models with fewer empirical parameters and taking advantage of a new generation of software environments. The research activity is decomposed on four axes:
1) A basic research activity devoted to the fuel element mechanical behaviour with a focus on the impact of irradiation on oxides fuel properties. This work will provide missing data, an identification of elementary mechanisms and the development of physics-based models of the non-linear mechanical behaviour of fuel and cladding.
2) The development of open source fuel performance codes with an advanced simulation at the two relevant scales needed to describe the microstructure and the fuel rod. The simulation will provide a 3D geometrical description of the thermo-mechanical behaviour and high performance computing capabilities.
3) The improvement of the current industrial models with learning data bases, composed of 3D reference simulation results, and Machine Learning type techniques. The demonstration of the capacity of 3D simulation and improved modelling for a set of representatives industrial studies for PWR and VVER including flexible operating conditions and enhanced Accident Tolerant Fuel.
4) The education and training and dissemination of the project’s results through open-access publications, workshops and exchanges with industrial end-users and training of a new generation of researchers.
Generation II and III reactor fuels in Europe take advantage of a large experimental feedback with a continuous evolution of fuel element design and materials, which allows maintaining high safety standards while adapting to the evolution of the operating conditions. Fuel performance codes, which enable the simulation of the behaviour of the fuel elements in reactor, are an essential component of the design, licensing and safety assessment of nuclear fuels. The licensing of innovative materials and fuel design requires an extension of the industrial fuel performance codes qualification in order to meet safety authority’s requirement regarding the Verification, Validation and Uncertainties Quantification process.
To address this question, the OperaHPC project will work on advanced simulation tools enabling 3D representation of the fuel rod, including models with fewer empirical parameters and taking advantage of a new generation of software environments. The research activity is decomposed on four axes:
1) A basic research activity devoted to the fuel element mechanical behaviour with a focus on the impact of irradiation on oxides fuel properties. This work will provide missing data, an identification of elementary mechanisms and the development of physics-based models of the non-linear mechanical behaviour of fuel and cladding.
2) The development of open source fuel performance codes with an advanced simulation at the two relevant scales needed to describe the microstructure and the fuel rod. The simulation will provide a 3D geometrical description of the thermo-mechanical behaviour and high performance computing capabilities.
3) The improvement of the current industrial models with learning data bases, composed of 3D reference simulation results, and Machine Learning type techniques. The demonstration of the capacity of 3D simulation and improved modelling for a set of representatives industrial studies for PWR and VVER including flexible operating conditions and enhanced Accident Tolerant Fuel.
4) The education and training and dissemination of the project’s results through open-access publications, workshops and exchanges with industrial end-users and training of a new generation of researchers.
During the first 18 months of the project, foundations of the work were laid and the technical activities yielded first significant results.
The design of a creep test device to be installed in a hot cell of the LECA-STAR laboratory of CEA, which will enable us to obtain essential results on the creep behaviour irradiated UO2 fuel, was completed. The samples that will be tested mechanically were characterized in detail at the grain and dislocation scale Electron Microscopy. In parallel, atomic scale calculations have enabled us to obtain significant results on the mobility of dislocations and their interaction with irradiation defects in UO2 and yielded a law that can be used for simulations at the dislocation scale. The investigation of rupture processes at the atomic scale to determine fracture toughness and unravel the underlying mechanism have already started.
Concerning the mechanical modelling at the fuel element scale, the state of the art of fuel and cladding mechanical laws was analysed and a common methodology was proposed for the development of physics-based mechanical models and their implementation in fuel performance codes.
High Performance Computing simulation tools for the fuel element behaviour in the reactor at the engineering scale (OFFBEAT/SCIANTIX codes) and at the microstructure scale (MMM code) are being improved. The developments include improvements of the model for the fission gas behaviour, large strain mechanical formulation, cladding oxide layer, RIA transients and crystal plasticity. The best practice and quality assurance protocols to use in the project has been formalized in a deliverable and open source repositories are available. A large number of tests were already performed using the OFFBEAT code and a webinar was organized for the users of the project.
An important work started to determine the input data for the advanced fuel performance code simulations using core or assembly scale studies and current versions of fuel performance codes. In preparation of the verification and the validation of the OFFBEAT and the MMM codes, case studied were selected and their characteristics were synthesised.
The activity devoted to the improvement of industrial fuel performance codes started with a detailed analysis of the industrial models to improve and of the methodology to improve them. This methodology includes the building of learning databases using 3D reference simulation results and machine learning techniques. The latter were investigated in detail to prepare a bibliographic revue. The preparation of the learning databases has started with the definition of the geometry and the loading parameter range to consider for the targeted applications. Finally, the definition of input data for the fuel element safety studies are well under way with new core scale simulation results for VVER and the selection of international benchmark data for PWR.
The design of a creep test device to be installed in a hot cell of the LECA-STAR laboratory of CEA, which will enable us to obtain essential results on the creep behaviour irradiated UO2 fuel, was completed. The samples that will be tested mechanically were characterized in detail at the grain and dislocation scale Electron Microscopy. In parallel, atomic scale calculations have enabled us to obtain significant results on the mobility of dislocations and their interaction with irradiation defects in UO2 and yielded a law that can be used for simulations at the dislocation scale. The investigation of rupture processes at the atomic scale to determine fracture toughness and unravel the underlying mechanism have already started.
Concerning the mechanical modelling at the fuel element scale, the state of the art of fuel and cladding mechanical laws was analysed and a common methodology was proposed for the development of physics-based mechanical models and their implementation in fuel performance codes.
High Performance Computing simulation tools for the fuel element behaviour in the reactor at the engineering scale (OFFBEAT/SCIANTIX codes) and at the microstructure scale (MMM code) are being improved. The developments include improvements of the model for the fission gas behaviour, large strain mechanical formulation, cladding oxide layer, RIA transients and crystal plasticity. The best practice and quality assurance protocols to use in the project has been formalized in a deliverable and open source repositories are available. A large number of tests were already performed using the OFFBEAT code and a webinar was organized for the users of the project.
An important work started to determine the input data for the advanced fuel performance code simulations using core or assembly scale studies and current versions of fuel performance codes. In preparation of the verification and the validation of the OFFBEAT and the MMM codes, case studied were selected and their characteristics were synthesised.
The activity devoted to the improvement of industrial fuel performance codes started with a detailed analysis of the industrial models to improve and of the methodology to improve them. This methodology includes the building of learning databases using 3D reference simulation results and machine learning techniques. The latter were investigated in detail to prepare a bibliographic revue. The preparation of the learning databases has started with the definition of the geometry and the loading parameter range to consider for the targeted applications. Finally, the definition of input data for the fuel element safety studies are well under way with new core scale simulation results for VVER and the selection of international benchmark data for PWR.
The activities conducted in the first 18 months and the first results obtained constitute solid foundations for the progress beyond the state of the art expected on the different research axes of the project.
The experimental data coupled with a physically based approach will enable a separate effect validation required from the safety authority for the fuel performance codes. Then, the development of physics-based models under progress will provide a complete set of widely shared mechanical laws for the pellet and the cladding.
A major achievement will be to make available to a large community validated open source computational tools enabling HPC simulation with unprecedented accuracy thanks to a 3D description and physics based models.
The computation of learning databases from 3D reference simulation results and the use of Machine Learning techniques will bring an important step to go beyond the current industrial modelling limitations.
The project will also demonstrate the capacity of 3D simulation to model a set of representative industrial conditions for PWR and VVER including flexible operating conditions and eATF. The impact of this applicative part will be reinforced by the End User Group of the project.
Finally, the significant number of PhD students involved in OperaHPC, as well as the summer schools, the exchange scheme and the open science approach will bring a significant contribution to the training of the next generation of researchers on fuels and fuel performance codes.
The experimental data coupled with a physically based approach will enable a separate effect validation required from the safety authority for the fuel performance codes. Then, the development of physics-based models under progress will provide a complete set of widely shared mechanical laws for the pellet and the cladding.
A major achievement will be to make available to a large community validated open source computational tools enabling HPC simulation with unprecedented accuracy thanks to a 3D description and physics based models.
The computation of learning databases from 3D reference simulation results and the use of Machine Learning techniques will bring an important step to go beyond the current industrial modelling limitations.
The project will also demonstrate the capacity of 3D simulation to model a set of representative industrial conditions for PWR and VVER including flexible operating conditions and eATF. The impact of this applicative part will be reinforced by the End User Group of the project.
Finally, the significant number of PhD students involved in OperaHPC, as well as the summer schools, the exchange scheme and the open science approach will bring a significant contribution to the training of the next generation of researchers on fuels and fuel performance codes.