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-ray Spectrometry of Environmental Samples Collected in FukushimaSaegusa, 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 -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.
Takahashi, Koji; Kajiwara, Ken; Okazaki, Yukio*; Oda, Yasuhisa; Sakamoto, Keishi; Omori, Toshimichi*; Henderson, M.*
Fusion Engineering and Design, 86(6-8), p.982 - 986, 2011/10
Times Cited Count：7 Percentile：45.61(Nuclear Science & Technology)In order to optimize the physics performance of ITER, the millimeter (mm) wave design of the equatorial electron cyclotron launcher is modified so that one-third of the total mm-wave injection power can be flipped to drive plasma current in the counter direction. The design change to perform the poloidal beam tilting of 5
at top and bottom beam row is conducted so that more efficient central power deposition is achievable. The opening shape in the blanket shield module (BSM) structure is also optimized to minimize the degradation of the mm-wave transmission efficiency. The degradation is only 0.3%. The modularization design of the steering mirror components and the internal shield, the application of a rail structure to perform the alignment of the steering mirror installation and the space allocation behind the BSM structure are implemented to increase the reliability, the manufacturability and the maintenability of the launcher design.
Kariya, Tsuyoshi*; Minami, Ryutaro*; Imai, Tsuyoshi*; Sakamoto, Keishi; Kubo, Shin*; Shimozuma, Takashi*; Takahashi, Hiromi*; Ito, Satoshi*; Muto, Takashi*; Mitsunaka, Yoshika*; et al.
Fusion Science and Technology, 55(2T), p.91 - 94, 2009/02
Times Cited Count：13 Percentile：62.25(Nuclear Science & Technology)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
Okazaki, Keishi*; Uehara, Shinichi*; Shimamoto, Toshihiko*; Funaki, Hironori; Kurikami, Hiroshi; Niizato, Tadafumi; Onishi, Yuzo*
no journal, ,
We have conducted detailed permeability k and porosity n measurements using fresh surface samples and drill cores of the three Neogene sedimentary formations in Horonobe area. Main results are outlined as follows. (1) k and n decrease from upper to lower horizons due to compaction and cementation and with increasing effective pressure Pe. Pressure cycling tests provide basic data for estimating k and n structures of the host rock. (2) Measurements for two specimens cored next to each other under the same Pe exhibit relationship showing an increase in k with increasing n that can be fit with Kozeny-Carman relationship. (3) n plotted against logarithm of Pe shows a clear knee point, similar to compaction curves for soils. This knee point is several times as large as the maximum Pe estimated from stratigraphy and from opal A to CT transition, so that the knee cannot be correlated with the maximum burial depth of the sedimentary rocks.
Saegusa, Jun; Maeda, Satoshi; Okazaki, Tsutomu; Yoda, Tomoyuki; Takeishi, Minoru
no journal, ,
no abstracts in English
Okazaki, Keishi*; Shimamoto, Toshihiko*; Uehara, Shinichi*; Niizato, Tadafumi
no journal, ,
Permeability and porosity are essential physical properties for analyzing of underground fluid flow. We have examined the effect of deformation on permeability and porosity of the Neogene sedimentary rocks (Yuchi, Koetoi, and Wakkanai Formations in the descending order) by laboratory experiments. Wakkanai Formation can be fluid conduit due to deformation, whereas Yuchi and Koetoi Formations do not necessarily become fluid-flow passes even with deformation. The deepest part of Koetoi Formation seems to have the highest seal capacity among the three formations.
Uehara, Shinichi*; Matsumoto, Takuma*; Shimamoto, Toshihiko*; Okazaki, Keishi*; Niizato, Tadafumi
no journal, ,
no abstracts in English
Takahashi, Koji; Kajiwara, Ken; Oda, Yasuhisa; Okazaki, Yukio*; Kobayashi, Noriyuki*; Sakamoto, Keishi
no journal, ,
no abstracts in English
Kasugai, Atsushi; Kajiwara, Ken; Oda, Yasuhisa; Takahashi, Koji; Hayashi, Kazuo; Okazaki, Yukio*; Sakamoto, Keishi
no journal, ,
Next target in the JAEA is development of advanced gyrotron for ITER such as high power repetitive operation, high frequency power modulation and dual frequencies. In repetitive operation, 400 s pulse operation was 10 times with pulse interval of 30 min was demonstrated. In high frequency power modulation, 300Hz-5min full modulation and 5kHz-10s RF modulation were demonstrated. In parallel, higher order mode gyrotron with TE31,11 have been manufactured and high power test was just started. In preliminary result, dual frequencies of 170 GHz with TE31,11 and 137 GHz with TE 25, 9 and high power output more than 1 MW were obtained in the short pulse operation.
Saegusa, Jun; Nagayama, Takehiro; Maeda, Satoshi; Okazaki, Tsutomu; Yoda, Tomoyuki; Takeishi, Minoru
no journal, ,
In the process of -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 -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 
Cs nuclide.
