Thermal And Resonance Absorption Cross Sections Of The U233 U235 Pu239 Fission Products

A new activation technique has been developed for the measurement of the ratio of the capture cross section of uranium-238 and the fission cross section of uranium-235 in zero-energy fast reactors. This work was initiated because of the long-standing discrepancy between calculated values in this ratio and radiochemically measured values. The new technique is a direct counting method which does not involve chemical separation in any way. Measurements have been made in four ZPR-3 fast reactor assemblies, two with hard spectra and two with soft spectra. In all four cases the measured ratio was slightly higher, on the average, than the calculated value. This is in strong contrast with the past radiochemical measurements in ZPR-3 assemblies, which gave vales 16% less than calculation.