EXPERIMENT AND ANALYSIS OF NEUTRON SPECTRA IN A CONCRETE ASSEMBLY BOMBARDED BY 14MEV NEUTRONSInstitute of Technology, Shimizu Corporation 4-17, 3-chome, Etchujima, Koto-ku, Tokyo, Japan 135 Yujiro Ikeda and Tomoo Nakamura Japan Atomic Energy Research Institute Tokai-mura, Ibaraki-ken, Japan 319-11 Neutron spectrum in concrete bombarded by 14 MeV neutrons was measured using a miniature NE213 spectrometer and multi-foil activation method. A good agreement between those two experimental methods was obtained within experimental errors. The measured spectrum was compared with calculated ones using two-dimensional transport code DOT3.5 with 125 group structure cross section libraries based on ENDF/B-IV, JENDL-2, and JENDL-3T (the testing version of JENDL-3). In the D-T neutron peak region, measured and calculated neutron spectra agreed well with each other for those libraries. However, disagreements of about -10% to +50% and -30% to +40% were obtained in the MeV region and still lower neutron energy range, respectively. As a result, it was concluded that those discrepancies were caused by the overestimation of secondary neutrons emitted by inelastic scattering from O, Si, and/or Ca which were the main components of concrete. KEYWORDS: D-T neutron, spectrum, concrete, ENDF/B-IV, JENDL-3PR1, JENDL-3T |