SIMS analysis of an UO2 fuel irradiated at low temperature to 65 MWd/kgHM

The results of a wide-ranging post-irradiation study of a PWR nuclear fuel by secondary ion mass spectrometry are presented. The average cross-section burn-up and the radial burn-up profile were determined from the radial distributions of one or more of the stable isotopes of fission product Nd. The fission gas Kr was analysed in-situ in a nuclear fuel for the first time and an investigation of the total fission gas content of the high burn-up structure using depth profiling was performed. It was confirmed that Kr is together with Xe in the pores of the high burn-up structure, and that almost all the fission gas lost from the fuel matrix is contained in the pores. In addition to Xe and Kr, the volatile fission products Te, Cs, I and Rb were also detected in the pores. The radial distributions of the minor actinides in the fuel are also reported. It was found that 237Np, unlike the isotopes of Pu, Am, and Cm, does not increase in concentration at the fuel rim.