Reevaluation of ENDL of sigma(n,f) and anti nu/sub p/ for /sup 235/U and /sup 239/Pu from 100 keV to 20 MeV

Abstract

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 /sup 235/U and /sup 239/Pu have been completed and entered into the Livermore Evaluated Nuclear Data Library (ENDL). For /sup 235/U(n,f) the recent evaluation of W.P. Poenitz of Argonne National Laboratory has been adopted as the /sup 235/U(n,f) ENDL standard. For /sup 239/Pu(n,f) the /sup 239/Pu//sup 235/U fission cross section ratio measurement of Carlson and Behrens of LLNL, which has served as the basis for the /sup 239/Pu(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 /sup 252/Cf 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 withmore » experimental data from the LLNL 14-MeV pulsed sphere measurements.« less