ELECTRON-CAPTURE-DELAYED FISSION PROPERTIES OF AM-232

Delayed fission from the electron-capture decay of Am232 was studied. The Np237(,9n)232Am reaction with multiple Np237 targets was used to produce Am232. The fission properties and half-life of Am232 were measured using a rotating-wheel system. The half-life of Am232 was found to be 1.31 0.04 min from measurements of the fission activity. A highly asymmetric mass-yield distribution was observed for the fission activity, and the average total kinetic energy of the fission fragments was found to be 174 5 MeV. Radiochemical separations confirmed the elemental assignment of the fissioning species to americium or fission following shortly after the decay of americium. The cross section for Am232 produced by this reaction and decaying by electron capture was determined to be 1.3 0.2 b by measuring the intensities of the daughter plutonium K x rays in radiochemically separated americium samples. The delayed-fission probability was found to be (6.91.0)×10-4 from the measured ratio of fissions to plutonium K x rays. The observed fissions were unambiguously assigned to electron-capture-delayed fission of americium by measuring the time correlation between the plutonium K x rays resulting from americium K capture and the subsequent fission. © 1990 The American Physical Society.