Periodic Reporting for period 3 - LEU-FOREvER (Low Enriched Uranium Fuels fOR REsEarch Reactors)
Periodo di rendicontazione: 2020-10-01 al 2022-09-30
At the core of reactor operation, nuclear fuel is a consumable and thus necessitates a secure supply chain. In the EU, this entails a diversity of supplier with licensed fuel design and the availability of enriched uranium.
Research reactors with an original soviet design present a weakness in their supply chain as they depend on a single manufacturer. In Europe, this is the case for some medium power research reactors. High power research reactors, with more standardized fuel designs, are, on their side, vulnerable to the supply of high enriched uranium necessary to reach their high performance.
Diversification of fuel element supply requires the adaptation of non-historic fuel manufacturers to the specificities of the reactor. The first step of this diversification is thus reverse engineering to tackle all the technical functions of the element for any type of operating conditions. Then, a design has to be set-up which fulfils the identified functions and is adapted to the producing means of the new manufacturer. Finally, the new fuel element should be licensed within one or several country. This last step might involve a qualification irradiation depending on the reactor specific needs.
With respect to enriched uranium supply, global efforts are made to minimize the use of highly enriched uranium in research reactors and thus minimize proliferation threat. In the EU, this conversion from high to low enriched uranium has already begun and is currently ongoing towards the qualification phase. This concerns both medium and high power research reactors. To reach this goal, the adopted path is the development of fuels core which presents a higher fissile uranium content without overcoming the 19.75% non-proliferant enrichment limit. Three ways have been identified to reach this goal: high density dispersed silicide fuels, dispersed uranium-molybdenum fuels and monolithic uranium-molybdenum fuels.
Although not very known by the public at large, research reactors are key large scientific facilities intervening in a diversity of field.
Through the production of radio-isotopes they are a supply product for nuclear medicine, which permits in-depth diagnosis, eg. lesions, bone-related pathologies. With neutron production capabilities, research reactors enable high level research in physics and chemistry as well as technological developments. Finally, research reactors serve to test materials in power reactors operational conditions thus participating to the safety of production of low carbon energy.
Research reactors with an original soviet design present a weakness in their supply chain as they depend on a single manufacturer. In Europe, this is the case for some medium power research reactors. High power research reactors, with more standardized fuel designs, are, on their side, vulnerable to the supply of high enriched uranium necessary to reach their high performance.
Diversification of fuel element supply requires the adaptation of non-historic fuel manufacturers to the specificities of the reactor. The first step of this diversification is thus reverse engineering to tackle all the technical functions of the element for any type of operating conditions. Then, a design has to be set-up which fulfils the identified functions and is adapted to the producing means of the new manufacturer. Finally, the new fuel element should be licensed within one or several country. This last step might involve a qualification irradiation depending on the reactor specific needs.
With respect to enriched uranium supply, global efforts are made to minimize the use of highly enriched uranium in research reactors and thus minimize proliferation threat. In the EU, this conversion from high to low enriched uranium has already begun and is currently ongoing towards the qualification phase. This concerns both medium and high power research reactors. To reach this goal, the adopted path is the development of fuels core which presents a higher fissile uranium content without overcoming the 19.75% non-proliferant enrichment limit. Three ways have been identified to reach this goal: high density dispersed silicide fuels, dispersed uranium-molybdenum fuels and monolithic uranium-molybdenum fuels.
Although not very known by the public at large, research reactors are key large scientific facilities intervening in a diversity of field.
Through the production of radio-isotopes they are a supply product for nuclear medicine, which permits in-depth diagnosis, eg. lesions, bone-related pathologies. With neutron production capabilities, research reactors enable high level research in physics and chemistry as well as technological developments. Finally, research reactors serve to test materials in power reactors operational conditions thus participating to the safety of production of low carbon energy.
Within the LEU-FOREvER project, four different solutions for the conversion of Research Reactors (RR) have been addressed with the aim of effectively augmenting the TRL of each conversion solution. This TRL assessment was an integral part of the project, paving the way for further growth in TRL by identifying the required actions.
The silicide fuel system has been examined in two variations: one for medium power RRs (MPRR), where the challenge was to redesign a fuel element manufactured in EU, and one highly loaded to satisfy the need of High Performance RRs (HPRR).
For the MPRR fuels, a close collaboration between the designer, manufacturer, already converted MPRR, and future MPRR users has successfullyfulfilled the purpose with proof of substitution ability for one type of element. Initially, input data were obtained through close discussions with the already converted reactor, MARIA. Using this input data, an equivalent design for one type of element of the LVR-15 reactor, satisfying EU manufacturability, safety, neutronic and thermo hydraulic performance, was designed and tested with a mock-up. Subsequently, a lead test assembly was manufactured and successfully irradiated in the LVR-15 reactor.
Depending on the core design of HPRR, conversion is achievable with the silicide fuel system through the development of a high loaded fuel core. The higher loading necessary for the operation of HPRRs still needs to be developed. A careful study of its manufacturing routes and an assessment of the expected thermo-mechanical behavior led to the first EU test irradiation of highly loaded U3Si2 fuel plates, known as the Hi PROSIT irradiation.
The interaction compound between the UMo particles and the aluminum matrix is identified as the main limiting factor in operational capacity of the UMo dispersed fuel system. The solution of choice for this issue is PVD deposition of a layer around the UMo particles to prevent physical interaction. Within the project, the industrial scale-up of the PVD equipment has been assessed, paving the way for a future industrialization. Furthermore, computation of the SEMPER-FIDELIS irradiation established the temperature history and the quality of the models describing the material evolution of the fuel plate.
The lower TRL UMo Monolithic route has been improved for manufacturing and behavior comprehension. A PVD coating machine enables the preparation of usable UMo foils for further fabrication steps. Characterized UMo foils manufactured in EU and irradiated outside of the project in the EMPIRE irradiation have been assessed post-irradiation on micro-sized samples.
An international summer school on research reactors has been organized within the project. The summer school managed to deliver a rich and in-depth view of the world of research reactor to students at a various levels.
The silicide fuel system has been examined in two variations: one for medium power RRs (MPRR), where the challenge was to redesign a fuel element manufactured in EU, and one highly loaded to satisfy the need of High Performance RRs (HPRR).
For the MPRR fuels, a close collaboration between the designer, manufacturer, already converted MPRR, and future MPRR users has successfullyfulfilled the purpose with proof of substitution ability for one type of element. Initially, input data were obtained through close discussions with the already converted reactor, MARIA. Using this input data, an equivalent design for one type of element of the LVR-15 reactor, satisfying EU manufacturability, safety, neutronic and thermo hydraulic performance, was designed and tested with a mock-up. Subsequently, a lead test assembly was manufactured and successfully irradiated in the LVR-15 reactor.
Depending on the core design of HPRR, conversion is achievable with the silicide fuel system through the development of a high loaded fuel core. The higher loading necessary for the operation of HPRRs still needs to be developed. A careful study of its manufacturing routes and an assessment of the expected thermo-mechanical behavior led to the first EU test irradiation of highly loaded U3Si2 fuel plates, known as the Hi PROSIT irradiation.
The interaction compound between the UMo particles and the aluminum matrix is identified as the main limiting factor in operational capacity of the UMo dispersed fuel system. The solution of choice for this issue is PVD deposition of a layer around the UMo particles to prevent physical interaction. Within the project, the industrial scale-up of the PVD equipment has been assessed, paving the way for a future industrialization. Furthermore, computation of the SEMPER-FIDELIS irradiation established the temperature history and the quality of the models describing the material evolution of the fuel plate.
The lower TRL UMo Monolithic route has been improved for manufacturing and behavior comprehension. A PVD coating machine enables the preparation of usable UMo foils for further fabrication steps. Characterized UMo foils manufactured in EU and irradiated outside of the project in the EMPIRE irradiation have been assessed post-irradiation on micro-sized samples.
An international summer school on research reactors has been organized within the project. The summer school managed to deliver a rich and in-depth view of the world of research reactor to students at a various levels.
For substitution elements targeting historical MPRRs, substantial progress toward strategic autonomy has been made. The newly designed element can be manufactured in EU and satisfies all the performance and safety requirements. This effort will need to be extended to cover all variations of the LVR-15 reactor. Inherently, this development secures the production of pharmaceutical radio-isotopes in EU.
The demonstration of high loaded silicide fuels has been achieved through the Hi¬PROSIT irradiation. This successful irradiation has resulted in advancing the technology to TRL 6 by the end of the project. The work carried out has rapidly developed a robust alternative solution suitable for certain HPRRs. High-loaded silicide fuel is also considered a preferred for reactors under construction. Building upon a proven fuel system ensures that conversion can be swiftly achieved, leading to a brighter future for neutron science and pharmaceutical radio-isotope production.
The dispersed UMo fuel system is seen as a high promising solution for HPRR conversion. With this project, the main drawback of this solution is well on its way to being overcome. To confirm this improvement, a test irradiation is necessary.
The suitability of UMo monolithic fuels manufactured in EU has been confirmed through their satisfactory behavior under flux. These observations have effectively led to an increase in the TRL level for UMo monolithic fuels fabricated in EU. This progress toward qualification of the UMo monolithic fuel system secures the mission of certain HPRR in EU, supporting neutron science and the production of pharmaceutical radio-isotopes, as well as enhancing the safety of nuclear power plants.
All the main results produced have been publicly and widely communicated. By educating master’s, PhD, and young professionals, awareness on the importance of research reactors in society has also been enhanced.
The demonstration of high loaded silicide fuels has been achieved through the Hi¬PROSIT irradiation. This successful irradiation has resulted in advancing the technology to TRL 6 by the end of the project. The work carried out has rapidly developed a robust alternative solution suitable for certain HPRRs. High-loaded silicide fuel is also considered a preferred for reactors under construction. Building upon a proven fuel system ensures that conversion can be swiftly achieved, leading to a brighter future for neutron science and pharmaceutical radio-isotope production.
The dispersed UMo fuel system is seen as a high promising solution for HPRR conversion. With this project, the main drawback of this solution is well on its way to being overcome. To confirm this improvement, a test irradiation is necessary.
The suitability of UMo monolithic fuels manufactured in EU has been confirmed through their satisfactory behavior under flux. These observations have effectively led to an increase in the TRL level for UMo monolithic fuels fabricated in EU. This progress toward qualification of the UMo monolithic fuel system secures the mission of certain HPRR in EU, supporting neutron science and the production of pharmaceutical radio-isotopes, as well as enhancing the safety of nuclear power plants.
All the main results produced have been publicly and widely communicated. By educating master’s, PhD, and young professionals, awareness on the importance of research reactors in society has also been enhanced.