OperaHPC project

OPEn HPC theRmomechanical tools for the development of eAtf fuels

In a nutshell

Electrification of the energy sector will probably be a key step for its transition to climate-neutrality. In order to achieve it as soon as 2050, it could therefore be necessary to maintain and even extend the production capacity of Generation II and III 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. 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. The research and development associated to these evolutions can take a long time if experimental irradiation program is not enough optimized. This optimization is not always possible with industrial fuel performance codes usually based on a simplified geometrical fuel rod representation called 1.5D. To address this question, 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 have been developed for more than a decade.

These 3D codes still have some limitations concerning the accuracy of the description of the fuel behaviour and their use in an industrial context by a larger community. To go beyond the state of the art and to enable major advances, the OperaHPC project – OPEn HPC theRmomechanical tools for the development of eAtf fuels – will adress the following objectives: 

  1. Advance the predictive capabilities of the simulation by improving significantly the understanding and description of the thermomechanical behaviour under irradiation of UO2 based fuel elements. 
  2. Advance the numerical capabilities of 3D state-of-the-art fuel performance codes and propose a methodology with new physically based models taking advantage of 3D results for industrial applications.  For this, the simulation of the thermomechanical behaviour of fuel rods will be bring several steps forward in terms of microstructure description, high performance computing (HPC) capabilities and reduced order modelling.
  3. Transfer the new results and methodologies to end-users for the licencing of new fuel concepts, including eATF. This will be possible with open source codes as well as training in order to give access to the progress made for the fuel performance codes to a broad community including the next generation of researchers.

Multiscale modelling and characterization of non-linear mechanical behaviour of irradiated fuel

The objectives of WP1 are to get further insight into the creep and rupture behaviour of irradiated UO2 fuel using a basic research approach coupling multiscale modelling and experimental tests and characterizations. This will extend the work done in the H2020 INSPYRE project on fresh fuels.

Development of multiscale mechanical models for fuel elements

WP2 aims at developing improved rheological non-linear mechanical models needed in WP4 for the fuel pellet and the cladding.


Calculation of input data and boundary conditions using state-ofthe-art fuel performance codes

The objective of the work package is to produce high-fidelity input data and associated tools for the simulation of fuel element thermomechanical behaviour using the OFFBEAT code developed in WP4. The results will be used for verification, validation and uncertainties quantification in WP5, as well as for the safety assessment of the eATF concepts in WP7.

Development of 3D HPC simulation tools for the thermo‐mechanical behaviour under irradiation

WP4 is aimed at the development of open-source 3D high-fidelity simulation tools for the thermomechanical behaviour of nuclear fuel rods under irradiation. Two main HPC-oriented tools are developed, the MMM tools for mesoscale applications (i.e., a Representative Volume Element with heterogeneous microstructure) and the OFFBEAT code for engineering-scale applications (i.e., part or all of the fuel rod). In addition, a prototype tool is developed using a novel multiscale meshless methodology that would help addressing some limitations of MMM and OFFBEAT.

Verification and Validation, Uncertainty and Sensitivity Analyses

The objective of WP5 is to achieved (1) Verification, (2) Validation, and (3) Uncertainty and Sensitivity analyses for the MMM and OFFBEAT codes developed in WP4 before their application in WP6 and WP7.

Development of improved models for industrial fuel performancecodes

This work package is aimed at the development of improved models for industrial fuel performance codes thanks to machine learning and model order reduction techniques and reference 3D simulation results computed with the MMM and OFFBEAT codes developed in WP4.


Simulation of fuel element behaviour in operating and accidental transient conditions

The objective of this WP is to provide a detailed assessment of the fuel element behaviour using 3D advanced tools and improved industrial fuel performance codes. Selected scenarios will be based on a representative irradiation history of a fuel element in a VVER or a PWR in a sequence composed of a nominal steady state condition succeeded by a transient (due to flexible operation or accidental).

Education and training, exploitation, dissemination and communication

The WP is devoted to dissemination and communication of the Project activities and results, as well as to organize the education and training of young scientists in the field of the Project.


Project management

The objective of the WP is to ensure timely delivery of the expected results to meet the provisions of the Grant Agreement (GA). It covers progress monitoring, consortium coordination, decision-making, conflict resolution, quality assurance, cost control, management of administrative, financial and legal matters. The WP groups the activities of all the coordination boards supporting the Coordinator in the Consortium management.

News AND Events

The Project kick off meeting will be held on
Nov 23-24° 2022 in Aix en Provence