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.