Plasma and Fusion Research

Volume 15, 2405043 (2020)

Regular Articles

Design of Neutron Spectrum-Shaping Assembly Around the Pneumatic Tube-End in the LHD Torus Hall for the Medical Research Application
Makoto I. KOBAYASHI1,2), Kunihiro OGAWA1,2), Mitsutaka ISOBE1,2), Takeo NISHITANI1), Teruki NISHIMURA1), Keisuke MUKAI3), Sachiko YOSHIHASHI4) and Masaki OSAKABE1,2)
1)
National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
2)
The Graduate University for Advanced Studies, SOKENDAI, Toki 509-5292, Japan
3)
Institute of Advanced Energy, Kyoto University, Uji 611-0011, Japan
4)
Nagoya University, Nagoya 464-8603, Japan
(Received 26 November 2019 / Accepted 14 May 2020 / Published 24 June 2020)

Abstract

The designs of neutron spectrum-shaping assembly (NSSA) composed with various shielding materials with natural isotopic abundance were evaluated to construct the neutron field dominated with thermal neutron or epi-thermal neutron for the application of neutron filed in the torus hall of LHD toward the BNCT research. According to the neutron transport calculation by MCNP6, the fast neutron moderation efficiency was higher in polyethylene (PE) compared to lithium fluoride (LiF) and magnesium fluoride (MF), although LiF showed relatively large epi-thermal and thermal neutron absorption. This comparison showed that the thermal neutron field can be effectively achieved with using PE. For constructing the NSSA which can provide the neutron field dominated with epi-thermal neutron, several NSSA designs were evaluated with respect to fast neutron flux, epi-thermal neutron flux, and gamma-ray dose. The combination of MF, lead (Pb) and cadmium (Cd) can provide the good epi-thermal neutron field with the mitigations of fast neutron flux and gamma-ray dose, which is also suitable for BNCT research in the torus hall of LHD.

Keywords

neutron, BNCT, MCNP6, LHD

DOI: 10.1585/pfr.15.2405043

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