BURNUP MEASUREMENT METHOD OF IRRADIATED FUEL ASSEMBLY

PURPOSE:To precisely find proportion constant when the burnup of an irradiated fuel assembly is obtained by the use of a gamma radiation spectrum analysis method. CONSTITUTION:A neutron radiation rate radiated from a specified position of a standard irradiated fuel assembly 1 in which initial concentration has been known and irradiation history and a cooling period have been known or the cooling period of at least 1.5 years, normally 2 years or more has passed is measured 2. And the neutron radiation rate is found from long half life nuclide except for the neutron radiation rate based on Ca-242 of the standard irradiation fuel assembly and the burnup 3 is determined from the neutron radiation rate. On the other hand, a gamma radiation spectrum 4 radiated from a specified position of the standard irradiation fuel assembly 1 is measured to determine the proportion factor 6 with the burnup of gamma radiation strength on the basis of Cs-137.