uncertainty investigation of cs-134/cs-137 activity ratio method in determination of the spent nuclear fuel burnup

For storage of a spent fuel during the life of the facility, testing or evaluation may be required to determine the integrity of the spent fuel. in addition, various tests of the spent fuel are carried out at nuclear facilities for many purposes. therefore, it is necessary to theoretically and experimentally evaluate the fuel burnups as one of the most important issues for nuclear spent fuel storage. the present study discusses the 134cs/137cs activity ratio method in determination of the spent nuclear fuel burnup, which is very important in view of the spent fuel storage as well as its dose rate calculation. for this aim, origen and mcnpx codes were used to calculate the radioisotopes’ concentrations during the nuclear fuel burnup and different cooling times of tehran research reactor (trr) fuel assembly. the obtained results showed the burnup estimation might be maximum 2 times different from its real value by using this method if the fuel burnup history has not been regarded and the cooling time is unknown. for the specific cooling times, the discrepancy may be 36% if the fuel burnup history has not been modelled. the discrepancies between the estimated burnup and the real value may be less if the trr fuel assembly burnups are less than 55%.