ADJUSTMENT OF EVALUATED FISSION CROSS SECTIONS BY INTEGRAL DATA
Department of Energy Conversion Engineering, Kyusyu University
Kasuga, Fukuoka 816, Japan
D.L. Smith and J.W. Meadows
Applied Physics Division, Argonne National Laboratory
Argonne, IL 60439, U.S.A.
Fission cross Sections for 232Th, 233U, 234U, 235U, 236U, 238U, 237Np and 239Pu, evaluated from differential experiments and compiled in JENDL-3T, have been adjusted by using integral fission cross-section ratios measured for 232Th/235U, 237Np/235U, 238U/235U, 237Np/238U, 232Th/237Np, 236U/235U, 239Pu/235U, 233U/235U, 234U/235U, 234U/238U and 236U/238U in the continuum neutron spectrum produced by bombardment of a thick Be-metal target with 7 MeV deuterons. It has been demonstrated that the fission cross-section curves can be adjusted in the energy range between 1 and 10 MeV. The ratios of the calculated to experimental values for the integral fission cross-section ratios have been revised within ± 1.005 except for 232Th whose result is 1.02. The original values are between 0.995 and 1.067 in JENDL-3T. The adjustment method developed in the present work is valuable to evaluate accurate and consistent cross-sections in the MeV neutron energy region. Differential and integral data are complementary in a cross-section evaluation. The former are useful to determine shapes of the cross-section curves and the latter serve to adjust their absolute values.
KEYWORDS: Adjustment, Evaluation, Integral data, Averaged cross-section, Fission cross-section, Heavy nuclides, Simultaneous evaluation