<p>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 (K<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\upalpha _{1}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="normal">α</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation>) and from a ²³¹Th 15.62 keV X-ray induced by ²³⁵U <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\upalpha \)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="normal">α</mi> </math></EquationSource> </InlineEquation>-decay. The low energies of these lines suggest that they are mostly emitted from the fuel meat surface, and the poor counting statistics caused by strong self-attenuation 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.</p>