Global interest is growing in tri-isotropic coated particle (TRISO) fuels, used by high temperature gas-cooled reactors (HTGR). Such reactors have inherent safety features, are highly efficient and can produce the low carbon heat needed to decarbonize industrial processes like steel manufacturing. However, there remain a number of knowledge gaps in the existing research into such fuels, and the IAEA is launching a new coordinated research project (CRP) to improve understanding of TRISO fuel performance and its key properties.
For many years, the IAEA has supported countries in efforts to enhance the reliability of nuclear reactor fuels. The Agency has previously developed two benchmarks dedicated to the validation of predictive methods for fuel and fission products’ behaviour through CRPs:
- CRP-2 (IAEA, 1997), later updated to cover fuel fabrication, quality assurance, irradiation performance, safety testing and spent fuel.
- CRP-6 (2012) on HTGR reactor fuel technology, which developed a set of benchmarking activities to compare fuel performance codes under normal operation and operational transients.
During the benchmark exercises simulating real irradiation or heating experiments of HTGR reactor fuel technology, a large code-to-code discrepancy in the release of fission products was recognized. Knowledge gaps were identified in material properties relevant to fuel performance modelling. There was a lack of material properties (e.g., buffer, uranium oxycarbide (UCO) kernel) for proper modelling of relevant failure mechanisms. Experimental data for reactivity-initiated accidents (RIA) on irradiated fuel were also found to be missing, as was an accurate list of dominant fission products for the source term.
With many countries actively involved in deploying HTGR reactors and several states developing their own TRISO fuel performance analysis codes, the new CRP aims to increase confidence in the use of fuel performance codes that support coated particle fuelled reactors.
Overall CRP objectives
- Improving the knowledge and filling the gaps of key TRISO fuel properties for codes development (e.g., diffusivity, creep, thermal conductivity, mechanical properties, SiC strength) with new data (e.g., obtained from new experiments and/or generated by multiscale modelling) to provide input to these codes,
- The implementation of all the important TRISO particle failure modes into fuel performance codes that will be used for the validation against TRISO fuel experiments,
- Gathering the operating and transient envelopes for TRISO-fuelled reactors relevant to participating Member States for potential new measurements of fuel properties and new calculations,
- Evaluating existing RIA tests and evaluating gaps with accident conditions in TRISO-fuelled reactors relevant to participating Member States for potential new measurements of fuel properties and new calculations,
- The development of the list of fission products (FPs) that are of importance to the selective criteria to model their transport and release for licensing purposes, and to develop the methodology used to define the importance of each FP,
- The development of a database of existing experimental data and new dataset collection to validate codes,
- Performing code benchmark exercises, including uncertainty propagation.
Specific research objectives:
To strengthen international collaboration by bringing together experts to better utilize national R&D efforts:
- To promote the sharing of irradiation and accident data from HTR TRISO experiments and associated post-irradiation examination data.
- To optimise the use of available experimental data.
- To identify methodologies for measurement / obtaining of material properties relevant to fuel performance modelling.
To perform simulations of acquired datasets, using existing fuel performance codes:
- To compare, analyse and share simulation results among participants, including recommendations on fuel performance codes enhancement.
- To consider the development of novel modelling approaches that better describe TRISO fuel behaviour and performance.
How to join this CRP
Please submit your Proposal for Research Contract or Agreement by email, no later than 30 May 2024 to the IAEA’s Research Contracts Administration Section, using CRP ID ‘T12034’ and using the appropriate template on the Coordinated Research Activities web portal. A kick-off meeting for the project will be announced once the proposals have been assessed.
For further information related to this CRP, potential applicants should use the contact form on the T12034 CRP page. The IAEA encourages institutes to involve, to the extent possible, women researchers and young researchers in their proposals.
