The presence of Pu X-ray peaks in the gamma spectrum of Pu-bearing materials [for example, PuO2 and mixed-oxide (MOX) samples] is commonly attributed to alpha and gamma excitation. The aim of this work is the development of a mathematical model, based on the "thick target yield" approach, for both alpha- and gamma-induced fluorescence processes, thus enabling the quantification of the relative importance of these effects and the interpretation of the experimental data.

Experimental data obtained at the Performance Laboratory (European Commission, Joint Research Center, Ispra, Italy) from well-characterized PuO2 and MOX samples under well-defined experimental conditions are compared with the expected values based on the model developed, taking into account special self-attenuation of X rays from induced effects.

Finally, a feasible application of the model is considered concerning the field of nuclear material accountancy and control; the possibility of inferring U and Pu concentrations in MOX from the normalized Pu K-shell X-ray counting rate is considered, and the expected performances are given.