The burn-up of235U was determined in two uranium oxide samples (0.713 and 89.9%235U in mixture) irradiated simultaneously with a cobalt monitor, from the amounts of95Zr,103Ru,137Cs,140Ba and144Ce obtained by measuring the intensities of the corresponding gamma radiations. The samples were irradiated for 23 days, and
the fission products were measured after cooling for 100 days, nondestructively, by means of a Ge(Li) spectrometer. The integrated
neutron flux was determined by measuring the produced60Co in the cobalt monitor.
The burn-up in both samples was determined by measuring the intensity of eight gamma energies (0.5–1.6 MeV). The determined
values are in good agreement. The standard deviation of the mean value (