Integral measurement of fission-product reactivity worths in some fast reactor spectra

The reactivity worth per atom for a number of fission-product isotopes relative to that of 235U was measured in three various fast-reactor spectra. The following isotopes were studied: 95Mo, 97Mo, 99Tc, 101Ru, 102Ru, 104Ru, 103Rh, 133Cs, 147Pm and 149Sm. A fission product mock-up sample was also included in the measurements. The reactivity worths were measured by the pile-oscillator technique. The fundamental mode amplitude of the perturbation signal was obtained through Fourier analysis. The experimental results are compared with calculated values obtained from perturbation calculations using published cross-sections for the sample materials. From a comparison between the measured and the calculated reactivity worths it is concluded that only the 95Mo, 104Ru and 149Sm worths are well predicted in all three systems. For the other samples, the calculated values are generally too high. (author)