Fuel Burnup Determination Based on the Measurement of a Short-Lived Fission Product

A method is developed to estimate spent-fuel burnup using gamma-ray spectrometry of the short-lived fission product 140La. The 140La activity was established by reirradiating the spent fuel in a reactor core. Based on the measured 140La activity, burnup values can be deduced by iterative calculations. In this method, the fuel irradiation history is not needed. To verify its validity, burnup values deduced from 140La activities were compared with those deduced from the conventional long-lived I37Cs activities and 134Cs/137Cs activity ratios; good agreement was obtained. This method is applicable to reactors loaded with highly enriched, thin plate-type fuels.