This report describes a version of the code ALICE/LIVERMORE 82 which has been modified to output neutron yield information of the type one would measure in an experiment gated by measuring a fission fragment. The modified code does the same precompound/compound decay calculations as the code ALICE/LIVERMORE 82, but has additional buffers and algorithms for the neutron yield calculation. We calculate the pre-fission neutron spectra and multiplicities, and post-fission neutron spectra and multiplicities, predicted for measurements which are gated on fission events. In this report we describe the additional output, referring the reader to the more complete report on the original code for further details. asmmm a m-mvm is IHUMTQI

The neutron-induced fission cross section of Am has been measured over the energy region from 10 eV to -20 MeV in a series of experiments utilizing a linac-produced "white" neutron source and a monoenergetic source of 14.1 MeV neutrons. The cross section was measured relative to that of U in the thermal (0.001 to -3 eV) and high energy (1 keV to -20 MeV) regions and normalized to the ENDF/B-V 2 5U(n, f) evaluated cross section. In the resonance energy region (0.5 eV to 10 keV) the neutron flux was measured using thin lithium glass scintillators and the relative cross section thus obtained was normalized to the thermal energy measurement. This procedure allowed a consistency check between the thermal and high energy data. The cross section data have a statistical accuracy of -0.5% at thermal energies and in the 1-MeV energy region, and a systematic uncertainty of -5%. We confirmed that Am has the largest thermal fission cross section known with a 2200 m/sec value of 6328 b. Results of a Breit-Wigner sum-of-single-levels analysis of 48 fission resonances up to 20 eV are presented and the connection of these resonance properties to the large thermal cross section is discussed. Our measurements are compared with previously reported results.

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