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Journal Articles

Establishment of a Laboratory for $$gamma$$-ray Spectrometry of Environmental Samples Collected in Fukushima

Saegusa, Jun; Yoda, Tomoyuki; Maeda, Satoshi; Okazaki, Tsutomu; Otani, Shuichi; Yamaguchi, Toshio; Kurita, Yoshiyuki; Hasumi, Atsushi; Yonezawa, Chushiro*; Takeishi, Minoru

Proceedings of 14th International Congress of the International Radiation Protection Association (IRPA-14), Vol.3 (Internet), p.1078 - 1085, 2017/11

After the nuclear accident at the Fukushima Daiichi Nuclear Power Plant in March 2011, the Japan Atomic Energy Agency has newly set up a laboratory for radioactivity analysis in Fukushima. At the laboratory, radioactivity concentrations of environmental samples such as soil, water, dust filter, plant, etc., approximately 1,000 samples in a month, are measured with high-resolution $$gamma$$-ray spectrometry systems. The systems employ n-type HPGe detectors from Ortec. Since September 2012, characterization and upgrade of the systems have been performed aimed at enhancing reliability of analysis and convenience of customers. Resolving both systematic and technical issues, the laboratory has been accredited the ISO/IEC 17025 standard as a testing laboratory for radioactivity analysis.

Journal Articles

Analysis of ambient-dose-rate trends in Fukushima; Ecological half-life, effect of snow covering

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.

Oral presentation

Investigation of inspection method of centralized air sampling device for radiation protection

Yoshida, Keisuke; Yamada, Katsunori; Yoda, Tomoyuki; Tsunoda, Junichi; Muto, Yasushi; Kobayashi, Makoto; Kikuchi, Masamitsu

no journal, , 

no abstracts in English

Oral presentation

Coincidence summing correction factors based on P/T method and reference source method for volume samples

Saegusa, Jun; Nagayama, Takehiro; Maeda, Satoshi; Okazaki, Tsutomu; Yoda, Tomoyuki; Takeishi, Minoru

no journal, , 

In the process of $$gamma$$-ray spectrometry analyses for radioactivity measurements, the coincidence summing effect needs to be considered. In this study, the concidence summing correction factors for 605 and 796 keV $$gamma$$-rays from various standard volume sources were evaluated based on the peak-to-total (P/T) ratio method. The results were compared with the values directly obtained from the measurements of these sources containing certified amount of $$^{134}$$Cs nuclide.

Oral presentation

Reduction of environmental background count rates for Ge detectors at JAEA Fukushima Environmental Safety Center

Nagayama, Takehiro; Maeda, Satoshi; Okazaki, Tsutomu; Yoda, Tomoyuki; Saegusa, Jun

no journal, , 

no abstracts in English

Oral presentation

Validation of coincidence-summing correction based on the peak-to-total ratio

Saegusa, Jun; Maeda, Satoshi; Okazaki, Tsutomu; Yoda, Tomoyuki; Takeishi, Minoru

no journal, , 

no abstracts in English

Oral presentation

Systematization of correction factors of Ge detector efficiencies for volume samples with different filling conditions

Yoda, Tomoyuki; Maeda, Satoshi; Funaki, Hironori; Saegusa, Jun; Takeishi, Minoru

no journal, , 

In the measurement of the sample with different filling conditions, it is necessary to revise a detection efficiency. It systematize a correction factors of Ge detector efficiencies by Monte Carlo calculation and the measurement.

Oral presentation

Analysis and discussion on ambient-dose-rate trends in Fukushima; Ecological half-life, effect of snow covering

Saegusa, Jun; Yoda, Tomoyuki; Murakami, Mitsuhiro; Takeishi, Minoru

no journal, , 

no abstracts in English

Oral presentation

Survey of radiocesium accumulation in the building of Sasakino Analytical Laboratory, JAEA

Kurita, Yoshiyuki; Okazaki, Tsutomu; Maeda, Satoshi; Yoda, Tomoyuki; Saegusa, Jun

no journal, , 

no abstracts in English

Oral presentation

Findings obtained from daily check of mechanically cooled HPGe detectors

Maeda, Satoshi; Yoda, Tomoyuki; Okazaki, Tsutomu; Saegusa, Jun

no journal, , 

no abstracts in English

Oral presentation

Survey of radiocesium accumulation in the building of Sasakino Analytical Laboratory, JAEA

Kurita, Yoshiyuki; Okazaki, Tsutomu; Maeda, Satoshi; Yoda, Tomoyuki; Saegusa, Jun

no journal, , 

no abstracts in English

Oral presentation

Outline of Sasakino Analytical Laboratory, Fukushima Environmental Safety Center of JAEA

Saegusa, Jun; Yanagisawa, Kayo; Yamaguchi, Toshio; Manabe, Sachi; Yoda, Tomoyuki; Maeda, Satoshi; Utsumi, Azusa; Shibamichi, Masaru; Ejiri, Akira; Kurita, Yoshiyuki; et al.

no journal, , 

no abstracts in English

Oral presentation

Relationship between cooling temperature and energy shift of a mechanically-cooled Ge detector

Maeda, Satoshi; Yoda, Tomoyuki; Okazaki, Tsutomu; Otani, Shuichi; Saegusa, Jun

no journal, , 

no abstracts in English

Oral presentation

Advancement of $$gamma$$-spectrometry with Ge semiconductor detectors for the analysis of environmental soil samples

Saegusa, Jun; Maeda, Satoshi; Kurita, Yoshiyuki; Yoda, Tomoyuki; Takeishi, Minoru

no journal, , 

no abstracts in English

Oral presentation

Rapid measurement of air dose rate surrounding roads in Fukushima evacuation zone by vehicle-borne survey with different height mounted detectors

Takeyasu, Masanori; Takeishi, Minoru; Yoda, Tomoyuki; Saegusa, Jun; Koizumi, Jin*; Tanabe, Tsutomu

no journal, , 

The measurement of air dose rate surrounding roads is important for developing plans for reducing radiation exposure with road traffic. The measurements were performed by vehicle-borne or man-borne surveys until now. However, air dose rate resulting from radioactivity on roads in mainly measured for former survey, and much man-power for long time measurement was necessary for the latter. In this study, we focused on the field of view for measurement being different with a difference of the detector setting height above the ground, and carried out the vehicle-borne survey along roads in evacuation zone in Fukushima prefecture with two detectors mounted at different heights. By this measurement, air dose rate surrounding the roads is discriminated. From the results, the radioactivity contamination trend was clarified, and are valuable for developing decontamination plan around the road.

Oral presentation

Environmental monitoring techniques after Fukushima Accident

Uezu, Yasuhiro; Ejiri, Akira; Yoda, Tomoyuki

no journal, , 

The Great East Japan Earthquake occurred on 11th March 2011. The Tsunami attacked the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Co. As a result, electric power was lost, furthermore electronic power generators were broken. After failing to restore power, there was an explosion and a large amount of radionuclides were released to the atmosphere. Japan Atomic Energy Agency (JAEA) monitored air dose rates, radionuclides in the air and environmental samples. At that time, there were many problems in the environmental radiation monitoring. The dose was beyond the range of the air dose monitor in monitoring car. The Ge detector's iron and lead shields were contaminated by the air. No standard source as "the phantom" could be obtained for children under 4. The JAEA solved these problems by developing new monitoring techniques. In this presentation, these improvements are shown and proposed as a new generation environmental radiation monitoring technique.

16 (Records 1-16 displayed on this page)
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