The Resonance Fission Integrals of U235, Pu239, and Pu241

Abstract
The resonance fission integrals of U235, Pu239, and Pu241 have been measured relative to the gold resonance capture integral by the cadmium ratio method. The cadmium ratios were measured in a reactor at a position where the epicadmium flux spectrum was closely 1/E except for a peak above 25 kev. A small spectrum correction was made for this flux peak to infer the fission integral over a pure 1/E spectrum using a calculated epicadmium flux spectrum. The resonance integrals obtained were, with a 0.5-ev cutoff energy, 274 ± 11b, 327 ± 22b, and 557 ± 33b for U235, Pu239, and Pu241, respectively.