車を利用した北海道における環境γ線測定 [in Japanese] A Car-Borne Survey of Environmental Gamma Rays in Hokkaido, Japan [in Japanese]
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An extensive car-borne survey was made for the evaluation of dose rates due to environmental gamma rays in Hokkaido during the period from May 1994 to January 1996. The dose-rate levels in Hokkaido were estimated from survey results measured with a portable pure germanium spectrometer installed in a car. The car speed was kept between 30 and 60km h<sup>-1</sup> (car-borne measurements). In addition to the car-borne measurements, another mode of measurement (spot measurements) was also made at 100 specific places selected in advance. The measurement times were set at 900s real time both for car-borne measurements and spot measurements. The survey routes covered almost all districts along the main roads in Hokkaido. From the car-borne measurements, absorbed dose rates in air due to gamma rays were found to be distributed from 14.9 to 116.5nGy h<sup>-1</sup>. The arithmetic mean dose rate and the standard deviation were calculated to be 42.1±16.2nGy h<sup>-1</sup>. The variation of total absorbed dose rate was found to be originated mainly by the variation of contribution from the Th-232 series nuclides.
- Jpn. J. Health Phys.
Jpn. J. Health Phys. 32(3), 295-304, 1997-09-30
Japan Health Physics Society