MEASUREMENT AND ANALYSIS OF NEUTRON SPECTRA IN STRUCTURAL MATERIALS USING AN ELECTRON-LINACResearch Reactor Institute, Kyoto University Kumatori-cho, Sennan-gun, Osaka-fu 590-04, Japan T. Mori and M. Nakagawa Japan Atomic Energy Research Institute Tokai-mura, Naka-gun, Ibaraki-ken 319-11, Japan With a view to reassessing the currently available evaluated neutron cross sections for main structural materials of reactors and silicon, electron linac time-of-flight experiments were conducted to measure the energy spectra of neutrons in sample piles of the respective elements, in the energy region covering 100 - 103 keV. The measured neutron spectra were compared with the theoretical ones obtained by one-dimensional transport calculation using the cross section data from either JENDL-2 or ENDF/B-IV. The resulting findings are as follows: (1) Both files call for revising the resonance parameters for Fe and Ni in the energy region below 100 keV. (2) For Fe, ENDF/B-IV requires supplementation of additional data on inelastic scattering in the region below 840 keV. (3) For Cr, both files need reevaluation of the total cross section, notably in the energy region of 4 - 8 keV where it is characterized by a series of large resonances. (4) For Mn, JENDL-2 requires supplementation the resonance parameters in the region above 100 keV. (5) For Si, the measured spectrum is higher than calculated one in the energy region of 200 - 500 keV. KEYWORDS: activation method, comparative evaluations, fast neutrons, group constants, integral check, neutron cross sections, neutron spectra, Sn method, time-of-flight method |