Review and characterization of best candidate isotopes for burnup analysis and monitoring of irradiated fuel

This research is an extension of feasibility study of MOX fuel online burnup analysis. A multitude of fission products identified as candidates have been scrutinized for their suitability of burnup analysis and spent fuel analysis. Best isotopes obtained for analysis by investigating half-life, fission yield, branching ratios, production modes, thermal neutron absorption cross section and fuel matrix diffusivity. 132I and 97Nb are identified as good isotope candidates for on-line burnup analysis. 132I is also a good candidate for plutonium/uranium discrimination due to the large difference in the fission yield of the isotope. For interim storage monitoring the well-established cesium isotopes appears to be the best choices unless the data gaps are addressed. Other alternate for cesium for interim monitoring is 131I, 140La, and 95Nb at the present time. Selection of one over the other choice must be made based on application. For the long-term storage monitoring 94Nb is the only attractive candidate. It has a low diffusion rate of ∼10−11 cm2/s, an almost zero neutron absorption cross section making it burnup history independent and decent gamma yield of 1.44E−09. In addition, the paper also identifies the data gaps for developing a robust burnup analysis tool using gamma spectroscopy.