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Evaluation of Induced Radioactivity Generated during LHD Deuterium Plasma Experiments

Sachiko YOSHIHASHI, Hayato YAMADA, Makoto KOBAYASHI¹⁾, Takeo NISHITANI, Atsushi YAMAZAKI, Mitsutaka ISOBE¹⁾, Kunihiro OGAWA¹⁾ and Akira URITANI

Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan

1)

National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan

(Received 7 January 2022 / Accepted 30 June 2022 / Published 24 August 2022)

Abstract

Neutrons are generated in a fusion plasma and induce various radionuclides via a nuclear reaction with fusion reactor materials. Evaluating the kinds of nuclide and the amount of induced radioactivity is important for decommissioning planning and regular maintenance. In this study, we verified a long-term prediction model of induced radioactivity in the large helical device (LHD) model by comparing induced radioactivity generated during deuterium plasma experiments in LHD with results calculated using a high-energy particle-induced radioactivity code. The metals employed for activation were SUS316L, Co, Mo, and Ni. During the deuterium plasma experiments, these materials were placed on an 8-O port of the LHD, and the induced radioactivity was measured weekly. To computed induced radioactivity using DCHAIN-SP, the neutron energy spectrum was computed using the LHD model with the Monte-Carlo simulation code PHITS. Although the calculated and measured radioactivity of ⁵⁸Co and ⁵⁴Mo agreed well, the calculated values of ⁶⁰Co and ⁹⁹Mo were underestimated. However, low-energy components could be improved by incorporating peripheral devices into the LHD model, resulting in more accurate radioactivity predictions.

Copyright (c) 2022 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

neutron, induced radioactivity, activation, LHD, decommissioning

DOI: 10.1585/pfr.17.2405096

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