Post-irradiation examination of silicide fuel (U3Si2-Al) with 4.8 gU/cm3 for RSG-GAS

The GA Siwabessy Multipurpose Reactor (RSG-GAS) has a nominal thermal power of 30 MWth and uses silicide fuel (U₃Si₂-Al) with a 2.96 gU/cm³ uranium density. To extend the reactor operating cycle, the RSG-GAS fuel can be converted to use a higher density fuel such as silicide fuel with a 4.8 gU/cm³ density. Irradiation tests of silicide fuel with 4.8 gU/cm³ density in the RSG-GAS core have been carried out to achieve burnup fractions of 20%, 40%, and 60% burned U-235. As part of a study for the development of new research reactor fuels, the post-irradiation examination (PIE) has been done for mini fuel plates that have been irradiated at the RSG-GAS. Several aspects of the PIE that were considered were physical changes, fuel swelling, and burnup distribution on the fuel plate. An in-depth analysis was conducted to verify the performance of 4.8 gU/cm³ silicide fuel so it can be used in the reactor core. Non-destructive testing in the form of visual inspection showed that the dimensions of the fuel plate did not change and there were no physical anomalies that could affect the performance of the silicide fuel plate for up to 60% burnup fraction. Measurement of the axial burnup distribution on the fuel using destructive tests, either based on the isotopic masses of Cs-137 or U-235 showed a consistency. In general, the physical properties of the silicide fuel plate that has been burned up to 60% burnup fraction are still quite relevant so the RSG-GAS fuel plate with a 4.8 gU/cm³ uranium density can be a candidate to replace the typical 2.56 gU/cm³ silicide fuel in RSG-GAS which currently has an average discharge burnup of 56%.