Process for the nondestructive determination of the burnup level of nuclear fuels

The fission product 140Ba-La is used to activate the threshold detectors of 115In, 111Cd, 103Rh and/or 167Er into isomer state. From the intensity of the gamma-radiation of the latter elements conclusions can be drawn concerning the 140Ba-La content of the spent fuel, i.e. about the degree of burnup. The resonance threshold detectors do not detect the high-intensity gamma-lines below 1 MeV. Thus, the process is more exact and more simple than those applied before, and it makes possible the determination of both the degree and the distribution of burnup. (L.E.)