Systematic study on keV-neutron capture cross sections of long-lived fission products

The neutron capture cross sections and capture gamma-ray spectra of stable Sn and Se isotopes were measured in an incident neutron energy region from 15 to 100 keV and around 550 keV as a part of a systematic study on keV-neutron capture cross sections of long-lived fission products. A neutron time-of-flight method was adopted with a ns-pulsed neutron source based on the 7Li(p,n)7Be reaction and with a large anti-Compton NaI(Tl) spectrometer. A pulse-height weighting technique was applied to the observed capture gamma-ray pulse-height spectra to obtain the capture yields. Using the standard capture cross sections of 197Au, the capture cross sections of stable Sn and Se isotopes were derived with the error of about 5%. The capture gamma-ray spectra were obtained by unfolding the observed capture gamma-ray pulse-height spectra. The present results for the capture cross sections are compared with the previous measurements and the evaluations of JENDL-3.3 and ENDF/B-VI.8 and VII.0. (author)