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Published: 1984

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Reevaluations of the neutron-induced fission cross sections from 100 keV to 20 MeV and anti nu/sub p/(E) from 0 to 20 MeV for 235U and 239Pu have been completed and entered into the Livermore Evaluated Nuclear Data Library (ENDL). For 235U(n, f) the recent evaluation of W.P. Poenitz of Argonne National Laboratory has been adopted as the 235U(n, f) ENDL standard. For 239Pu(n, f) the 239Pu/235U fission cross section ratio measurement of Carlson and Behrens of LLNL, which has served as the basis for the 239Pu(n, f) ENDL evaluation to the present, is compared with several new ratio measurements for the new evaluation. For anti nu/sub p/(E) ratio values of Soleihac, et al. were renormalized to the currently accepted value of 252Cf anti nu/sub sf/ and used as the basis for the present ENDL evaluation. Experimental anti nu/sub p/(E) values measured by Gwin, et al. in 1978 from 0.5 keV to 10 MeV are reasonably consistent with the values of Soleihac, et al. Results of criticality calculations using the new evaluated cross sections and anti nu/sub p/(E) are compared for various critical mass assemblies. Also, Monte Carlo calculations using these new evaluations are compared with experimental data from the LLNL 14-MeV pulsed sphere measurements.