Verification of energy release in fission from power plant calorimetrics and isotopic composition of spent fuel

The reactor of a nuclear power station was treated as a flow calorimeter to evaluate the energy released in fission from a given loading of UO₂. The changes in the inventories of U and Pu isotopes were obtained from reprocessing of the spent fuel and the corresponding total number of fissions was determined. The resulting energy released per average fission in a fuel irradiated to 11·5GWD/MTU was found to be 203·2 ± 6·0 MeV from batch isotopic method, 204·6 ± 6·3 MeV from batch composite method and 204·8 ± 7·2 MeV from ¹⁴⁸Nd-analyses. For burnups both higher and lower than this value, the results indicate the presence of a burnup dependence somewhat greater than that expected on the basis of Pu buildup alone. The accuracy of the plant data was found to be limited by the ability to measure the steam generator feed water flow rates.