Data of radon measurement in underground facilities of Mizunami Underground Research Laboratory

Aoki, Katsunori; Yamanaka, Hiroki*; Watanabe, Kazuhiko*; Sugihara, Kozo

JAEA-Data/Code 2020-018, 45 Pages, 2021/02

JAEA-Data-Code-2020-018.pdf:4.54MB
JAEA-Data-Code-2020-018-appendix(DVD-ROM).zip:6.8MB

Mizunami Underground Research Laboratory (MIU) Project is pursued by Japan Atomic Energy Agency (JAEA) in the crystalline host rock (granite) as a part of geoscientific study of JAEA, and underground facilities of MIU are constructed down to 500m blow the ground surface. As small amount of Uranium is normally contained in granite, high concentration of radon is sometimes detected in the air of the underground facilities constructed in granitic rocks depending on their ventilation conditions. Radon concentrations in underground facilities of MIU have been measured according to the excavation progress of underground facilities or the change of ventilation system. It is recognized that the data obtained by the actual measurement of radon concentration in such underground facilities are rare and valuable. This repot summarizes the measured data from fiscal 2010 to fiscal 2020, together with the information of ventilation conditions and air temperature which affect radon concentrations in underground facilities. The variation of the equilibrium factors of radon is also examined with the actually measured data. As a result, it has been found that radon concentration in the drift is high in summer and low in winter according to the natural ventilation caused by the seasonal temperature difference between in and out of the underground facilities. Furthermore, the temporary increase in the equilibrium factor of radon in the drift at the start of ventilation is supposed to be due to the aerosol increase by the ventilation flow, such as the dust blown up.

Comparison of airborne and ground-based tools used for radiation measurement in the environment

Ochi, Kotaro; Sasaki, Miyuki; Ishida, Mutsushi*; Sanada, Yukihisa

Progress in Nuclear Science and Technology (Internet), 6, p.103 - 107, 2019/01

http://doi.org/10.15669/pnst.6.103

After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, a large amount of radionuclides was spread out all over the world. In our previous study, we developed the aerial radiation monitoring technique using unmanned helicopter for investigating the dose rate derived deposited radionuclides over wide area. In addition, many monitoring techniques were developed for investigating the local distribution of radionuclides using unmanned aerial vehicle, handheld instrument and car within small area. Distinction of these methods depends on desirable position resolution of dose rate. However, the comparison method of the measurement result between different methods is not established. In this study, we attempted to evaluate the some methods of airborne and ground radiation measurement in same extended farm.