Absorbed Dose Rate in Air at the NIFS Site before the Deuterium Plasma Experiment in LHD

The absorbed dose rate in air was measured at the National Institute for Fusion Science (NIFS) site before the deuterium plasma experiment in the Large Helical Device (LHD). A pocket survey meter was used for the measurement of 1cm dose equivalent rates in units of µSv h−1 and these results were converted to absorbed dose rates in air (units: nGy h−1) using a conversion factor. The arithmetic mean of the absorbed dose rates in air based on 257 measurement points at NIFS site was 45 nGy h−1. The result of this study suggests that the building material and/or paving stone enhance the dose rates in air at the NIFS site.