Quantitative WDS analysis to determine plutonium homogeneity in CANDU mixed-oxide fuel

As Part of AECL's mixed-oxide (MOX) fuel development program, a quantitative X-ray wavelength dispersive spectrometric (WDS) analysis was conducted to determine plutonium homogeneity in as-fabricated MOX fuel, using a shielded analytical scanning electron microscope. This paper describes the technique and some results of the analysis. The as-fabricated fuel exhibited a duplex microstructure: a matrix with randomly distributed plutonium-rich particles. The particle size ranged from 10 to 30 μm. To conduct the WDS analysis, PuO2 and UO2 standards were used; plutonium Mβ and uranium Mα lines were monitored. Point analysis with a 2-μm interval was conducted diametrically across the particles to obtain uranium and plutonium distribution profiles. The profiles all exhibited a similar shape; a compositional transition band was observed around each particle, indicating the occurrence of plutonium and uranium interdiffusion. Uncertainty and consistency of the determinations were examined, and the results are satisfactory. (author)