b'MiniFuel has been demonstrated through fabrication, irradiation and now PIE to be a valuable tool for screening novel fuel concepts and performing separate effects irradiation testing.detect failure and large deformationsamples were UN kernels with of the fuel geometry. The evaluationseveral different chemistry vari-of fuel by PIE has become moreants and UN coated particles (UN advanced with more techniquesTRISO). Initial visual examinations applied to irradiated fuel to betterrevealed no noticeable irradiation understand the phenomenologicalinduced changes in the kernels or mechanisms behind fuel failure.particles. The fission gas release for However, performing complexthis fuel is generally in line with materials science on a large number ofathermal recoil release as expected. integra fuel tests is often impractical.The microstructural examination Separate effects test, like MiniFuel,of these kernels revealed good allow PIE to focus on a few variablesperformance for these irradiation and more quickly evaluate fuel perfor- conditions. Burnup in the fuel was mance. This approach to testing allowsevaluated by a variety of methods. for the developing or improving fuelGamma spectrometry was used to performance models used in fuelevaluate burnup in all the kernels performance codes like BISON. and particles, and mass spectrom-Accomplishments: etry was used to evaluate burnup The irradiation performance of thefor the UN kernels. Very few first MiniFuel irradiation test andirradiation-induced changes can be samples was evaluated throughobserved in the microstructure. An detailed PIE. The first irradiatedexample of the microstructure of 4 of the kernels from first MiniFuel 52 2020|AFC ACCOMPLISHMENTS'