Studies of the Fission Integrals of U235 and Pu239 with Cadmium and Boron Filters

s The resonance fissions in U235 and Pu239 have been studied using cadmium and boron filters. Fission chambers were used as detectors and the experiments were performed in beam geometry. The neutron energy distribution in the beams transmitted through the different filters was determine^, .with a fast chopper. From the cadmium filter, measurements the fission resonance integrals were determined. The values obtained were 278 - 9 b for U235 and 3 01 t 10 b for Pu239; 0.5 eV < E < 1 MeV. Complementary Pu239 measurements were made in which the fission events were detected from the fission product activity in irradiated foils. Contrary to what has been reported elsewhere the value of the Pu239 resonance integral, found in this way, agreed well with that obtained from the fission chamber measurement. The experiments with the boron filters yielded results which, for the thin filter, agreed well with those calculated from the cross section data given in the Karlsruhe compilation. The discrepancy was larger for the thick filter but the values did not disagree outside the common limits of error.