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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - LEU-FOREvER (Low Enriched Uranium Fuels fOR REsEarch Reactors)

Teaser

Summary

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 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.

Work performed

Risk and quality plan of the overall project have been re-evaluated with a finer grid, resulting in an augmented confidence in reaching the project goals.
To test the high density uranium solution, the preliminary steps have all been achieved successfully: a test matrix including most of the needs of the partners has been set-up, preliminary thermo mechanical calculations have been carried out to verify the behaviour of such tests plates, and, a first batch of high density fuel plates have been manufactured using depleted uranium.
For the monolithic UMo fuel plate solution, the EMPIrE irradiation (not a part of LEU FOREvER) has ended on time. The tested mini-plates are now under cooling before being examinated. In-between, CEA has received fresh samples of as-fabricated monolithic UMo fuel and began their examination.
With respect to fuel supplier diversification for European MPRR of soviet design, technical data have been collected from NCBJ , CVR (both LEU-FOREvER partners) and MTAEK (Hungaria) by Technicatome. A synthesis of the collected data has been discussed at a workshop organised in Czech Republic, as well as an associated preliminary design. Following this stage, Technicatome issued preliminary requirements for fuel assembly design and a preliminary design for LVR-15 fuel assembly. With the existence of this documents, Technicatome was able to define the conditions for hydraulic tests to be carried out on the LVR-15 replacement assembly.
In the dissemination and communication work package, a website for the project has been set-up, and the draft organisation for a summer school has been discussed via three video conference. The summer school is foreseen to take place in autumn 2020 before or after the conference NUFUEL.

Final results

WP2
Through the analysis and development of fabrication process for silicide fuels, the manufacture of silicide fuel plate will be done at a more competitive cost on one side, and, on the other, new formats, such as high loaded silicide fuels. This work package will also reinforce the computational capacity for the prediction of the behaviour of silicide fuels. Finally, the processes involve in the fabrication of UMo monolithic fuels will be adjusted and tested at pilot scale.

WP3
The analysis of monolithic uranium molybdenum samples irradiated during the EMPIrE irradiation will bring a valuable insight on its behaviour during irradiation. Particularly, the lower scale comparative analysis before and after irradiation will permit to draw a precise picture of irradiation effects on the material state of uranium molybdenum monolithic fuels. From these observations, generic conclusions on the behaviour of UMo monolithic fuels, and their expected properties under irradiation will be derived. Concurrently, the review of existing models representing the behaviour of uranium-molybdenum dispersed, and their implementation in the thermo-mechanical computation code MAIA, will enhance the prediction capability for the fuel in-core behaviour.

WP4 / WP5
The careful gathering of data on the operation of soviet designed research reactors in Europe led to the design of a replacement fuel element suitable for the LVR 15 reactor. This design will be tested for thermos-hydraulic behaviour and during a qualification irradiation, resulting in an effective fuel supplier diversification for the LVR 15 reactor.
The Hi-PROSIT irradiation will be a key to assess the behaviour of newly manufactured high density silicide fuels plates. The outcome of these irradiation will pave the way for reactors operators having chosen this solution for their conversion.