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Saegusa, Jun; Yanagisawa, Kayo; Hasumi, Atsushi; Shimizu, Takenori; Uchida, Yoshiaki*
Radiation Physics and Chemistry, 137, p.210 - 215, 2017/08
Times Cited Count：1 Percentile：10.62(Chemistry, Physical)Following the Fukushima Daiichi Nuclear Power Plant (NPP) accident, large-scale radiation monitoring and environmental clean-up activities have been conducted throughout the Fukushima region. Outside air temperatures there reach 40
C in summer and -20C in winter, which are beyond the quoted range of many radiation survey instruments. For the purpose, temperature performances of four types of portable Japanese survey instruments which are widely used in Fukushima were experimentally investigated with a temperature-controlled chamber.
Saegusa, Jun; Yoda, Tomoyuki; Murakami, Mitsuhiro; Takeishi, Minoru
Kankyo Hoshano Josen Gakkai-Shi, 5(2), p.79 - 93, 2017/06
After the Fukushima Daiichi Nuclear Power Plant (NPP) accident in March 2011, environmental radiation monitoring works have been continuously conducted throughout the Fukushima prefecture of Japan. Five-year transitions of ambient dose rates at 15 locations 20-60 km away from the NPPs were precisely analyzed to investigate their chronological change. Measured dose rates were successfully fitted into a function consisting of a factor reflecting the physical decay of radiocesium and the other component such as the weathering effect. The ecological half-lives derived from the function ranged from 3 to 27 years (average 10 years). The radiation shielding effect by snow covering was also studied with the obtained functions. Due to the effect, dose rates were lowered by 15-50% by 20-cm-deep snow covering, and the ambient doses integrated over the five years were found to decrease by up to 7% compared to those without the snow covering that can be predicted from the fit function.
Tsuda, Shuichi; Saito, Kimiaki
"Fukushima No Fukko Ni Mukete No Hoshasen Ni Kansuru Korekara No Kadai" Shimpojiumu Hokokusho, p.30 - 33, 2015/00
Dose rate monitoring in air in the environment has been performed since the Fukushima Dai-ichi Nuclear Power Plant accident happened. The reliability of detectors such as survey-meters is ensured under a controlled set of standard conditions in a radiation calibration field. However, the calibration is performed only in a uniform irradiation condition in general, but in reality, the incident direction of the photons is random in the environment. Since detector responses are dependent on incident direction, except for spherical detectors, it is necessary to evaluate the reliability of the measured dose. In this study, using the PHITS code, dose rates in air of a common NaI(Tl) scintillation survey-meter and CsI(Tl) detectors used in the KURAMA system are calculated in a semi-infinite radiation field. In the presentation, the dependence of the dose rates on the incident direction of photons will be shown.
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JAERI-M 8141, 38 Pages, 1979/03
no abstracts in English
Tsuda, Shuichi; Saito, Kimiaki
no journal, ,
Air dose rate monitoring in the environment has been performed since the Fukushima Dai-ichi Nuclear Power Plant accident happened. In the measurement, NaI(Tl) and CsI(Tl) scintillation surveymeters/detectors are used, which are usually used in nuclear power plants and calibrated in a uniform irradiation condition in a radiation calibration field. In general, however, the detector responses are dependent on incident direction and in reality, the incident direction of the photons is not uniform in the environment. In this study, to evaluate the dependence of dose on the photon incident direction, the spectrum - dose conversion operator (G(E) function) for air kerma in a semi-infinite radiation field were obtained using the PHITS code for commonly used NaI(Tl) and CsI(Tl) scintillation detectors. The results indicate that the dose based on the G(E) in AP geometry, which is a common calibration geometry, is approximately 40% higher than that for the environmental monitoring. In the presentation, the results based on measured data will be reported.
