The Korea Atomic Energy Research Institute's successful irradiation tests and positive inspection of high-density uranium silicide fuel signal potential for high-enriched uranium to low-enriched uranium conversion of high-performance research reactors, aiming to bolster international nuclear non-proliferation efforts upon commercialisation.

Irradiation of test fuel at the BR2 reactor in Belgium (Image: KAERI)

A plate-type uranium silicide fuel, with a high uranium density designed for research reactors, has successfully completed irradiation tests and visual inspections, the Korea Atomic Energy Research Institute (KAERI) said. The uranium density of the test fuel is 5.3 grams per cubic centimetre, which is about 10% higher than that of the current fuel in use. The visual inspection yielded positive observations.

Although most material testing reactor (MTR) fuel assemblies utilise fuel plates with a uranium density of 4.8 gU per cubic centimetre, the development of higher uranium-density fuels has become crucial for high-performance research reactors. This development supports the conversion from high-enriched uranium (HEU) fuel to low-enriched uranium (LEU) fuel in the USA and Europe. In this context, KAERI initiated research and development on these high uranium-density silicide fuels in 2020, focusing on fuel plates with densities up to 5.3 gU per cubic centimetre.

For the fuel intended for high-performance research reactors, KAERI developed uranium silicide (U3Si2) spherical-particle powder using the atomisation method and has utilised it for the development of various research reactor fuels. KAERI is involved in the high-density atomised LEU U3Si2 MTR fuel qualification campaign - known as the 'KAERI High-Density Atomised Silicide Fuel Qualification Irradiation Project (KIMQI) Fuel Qualification Project of High-Density Atomised Silicide Fuel" - in collaboration with Belgium's Nuclear Research Centre (SCK-CEN).

The qualification campaign, which began in 2021, consists of two phases: the KIMQI-FUTURE test, which ran from 2021 to 2023 to confirm basic performance, and the KIMQI-GTA (Generic Test Assembly) to evaluate performance under high heat flux and high burnup conditions. The KIMQI-GTA irradiation was recently completed, achieving a peak heat flux of 470 W per square centimetre and a peak local burnup that reached 74% of the initial fissile content. The visual inspection results indicated that no abnormal conditions were experienced during the irradiation test, which is a positive indicator for the potential use of the developed high-density fuel in high-performance research reactors. The final qualification report, including Post-Irradiation Examination (PIE) test results, is expected to be available by the end of 2025.

Once this technology is commercialised, it will enable the replacement of HEU with LEU in high-performance research reactors, significantly contributing to the international nuclear non-proliferation effort.

In December 2022, KAERI signed a memorandum of understanding (MoU) with Poland's National Centre for Nuclear Research to supply nuclear fuel for Poland's research reactor MARIA using high-density low-enriched uranium U3Si2 plate-shaped nuclear fuel manufacturing technology. The MoU sees the South Korean institute looking to supply test fuels to MARIA for the qualification of nuclear fuel supply.