Plasma and Fusion Research

Volume 14, 1305130 (2019)

Letters

Measurement of Absorbed Dose Rate in Air at NIFS Site after the First Deuterium Plasma Experiment in LHD
Yoshitaka SHIROMA, Shigekazu HIRAO1), Naofumi AKATA2), Masahide FURUKAWA, Hitoshi MIYAKE3), Hiroshi HAYASHI3), Takuya SAZE3) and Masahiro TANAKA3)
University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan
1)
Fukushima University, Kanayagawa, Fukushima 960-1296, Japan
2)
Hirosaki University, Hirosaki, Aomori 036-8564, Japan
3)
National Institute for Fusion Science, Toki, Gifu 509-5292, Japan
(Received 8 May 2019 / Accepted 5 June 2019 / Published 11 July 2019)

Abstract

The latest measurement of the absorbed dose rate in air was performed at the National Institute for Fusion Science (NIFS) site during the period for the first deuterium plasma experiment conducted in Large Helical Device (LHD). The arithmetic mean of the absorbed dose rates in air for 222 measurement points at the NIFS site was 43 nGy h−1. Very little change was observed in the distribution maps of the absorbed dose rates in air before and after the deuterium experiment in the LHD. In addition, the absorbed dose rates in air around the buildings were distributed at similar high levels before and after the deuterium experiment. A radionuclide analysis of soil and broken stone was conducted using a high-purity Ge semiconductor detector. The absorbed dose rates in air at the NIFS site were mainly defined by the radiation from the ground and the building material around the measurement points. The effect of the deuterium experiment was so small that it was undetectable in this study.

Keywords

absorbed dose rate in air, environmental radiation, background measurement, deuterium plasma experiment, NIFS site

DOI: 10.1585/pfr.14.1305130

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