PNNL

Abstract

Advance high density monolithic alloy HALEU fuels have been scanned with a silicon drift detector scanning system to measure low-energy characteristic X-rays emitted by uranium daughters, as well as zirconium present as a foil diffusion barrier. Four peaks were measured across the surfaces of three plates, and are consistent with other thorium and protactinium peaks present in depleted uranium samples that are induced by the decay of 235U and 238U. Of the four peaks detected, three are dominated by the decay of 235U, and one peak at 15.70 keV covers two characteristic X-rays from the zirconium diffusion barrier (Ka1) and from a 231Th 15.62 keV X-ray induced by 235U a-decay. The low energies of these lines suggest that they are mostly emitted from the fuel meat surface, and the poor counting statistics cause by strong attenuation in air make these data a poor candidate for 235U/238U ratio analysis. We suggest, then, that these X-rays could be used for passive measurement of variations in the cladding thickness of these fuels to complement manual thickness measurement methods.