title: Microdosimetric investigation of the spectra from YAYOI by use of the Monte Carlo code PHITS.
abstract: The purpose of this study was to obtain the neutron energy spectrum on the surface of the moderator of the Tokyo University reactor YAYOI and to investigate the origins of peaks observed in the neutron energy spectrum by use of the Monte Carlo Code PHITS for evaluating biological studies. The moderator system was modeled with the use of details from an article that reported a calculation result and a measurement result for a neutron spectrum on the surface of the moderator of the reactor. Our calculation results with PHITS were compared to those obtained with the discrete ordinate code ANISN described in the article. In addition, the changes in the neutron spectrum at the boundaries of materials in the moderator system were examined with PHITS. Also, microdosimetric energy distributions of secondary charged particles from neutron recoil or reaction were calculated by use of PHITS and compared with a microdosimetric experiment. Our calculations of the neutron energy spectrum with PHITS showed good agreement with the results of ANISN in terms of the energy and structure of the peaks. However, the microdosimetric dose distribution spectrum with PHITS showed a remarkable discrepancy with the experimental one. The experimental spectrum could not be explained by PHITS when we used neutron beams of two mono-energies.
authors.affiliation: Department of Health Sciences, Graduate School of Medical Sciences, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka City, 812-8582, Japan. mnr.nakao@gmail.com
authors.forename: Minoru
authors.initials: M
authors.lastname: Nakao
authors.forename: Hiromi
authors.initials: H
authors.lastname: Baba
authors.forename: Ayumu
authors.initials: A
authors.lastname: Oishi
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Onizuka
mesh_terms: D000535:Aluminum; D009010:Monte Carlo Method; D009502:Neutrons; D011874:Radiometry / Q000379:methods*; D013057:Spectrum Analysis
chemical_list: D000535:Aluminum
references.citation: J Radiat Res. 2008 Sep;49(5):503-8
references.pmid: 18580044