A Note on the Assay of Special Nuclear Materials in Solution by X-Ray Fluorescence

X-ray fluorescence (XRF) techniques have been used for a number of years in the analytical chemistry laboratory to determine elemental concentrations in solution. The development of highresolution, energy-dispersive technology and the use of radioisotopic exciting sources greatly simplified the associated hardware, adding a degree of flexibility required for chemical process, in-line application. This technology renews the interest in the application of XRF to special nuclear materials (SNM) assay for both process control and materials accounting purposes. The traditional difficulty with XRF techniques— sample self-attenuation—has been addressed by several approaches, none of which are directly applicable to an in-line instrument. For a planar sample and a far-field geometry, the number of detected elemental x rays, N, is related to that element's concentration by