Determination of Fission Products in Irradiated Fuel by X-Ray Fluorescence

X-ray fluorescence is a well established analytical tool for measuring elemental composition of fairly large (~ 5cm²) "cold" samples. A version of t h i s technique has been developedfor analysis of radial distribution of fission products Xe, Cs and Ba in irradiated UO₂ fuel samples. About 0.1 mm thin slices of fuel pellets (full cross sections) are irradiated by 50 keV X-rays. The intensity of the Xe (Cs, Ba) Ko fluorescenceradiation generated is measured by means of a Ge detector fitted with a collimator. The slit is 0.5 mm wide in the scanning direction and 2 mm long. The measured Xe Ko x-ray intensities are converted to absolute concentrations by comparing to the intensity from a Xe gas standard. In the case of Cs and Ba solid standards may be used. The X-ray fluorescence analysis is compared to other techniques used to obtain radial fission product profiles, it is shown how a combination of X-ray fluorescenceand electron probe micro analysis is able to reveal the amount of Xe in the grain boundary porosities.