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Yamawaki, Masato*; Uesugi, Naoya*; Oka, Toshitaka; Nagasawa, Naotsugu*; Ando, Hirokazu*; O'Rourke, B. E.*; Kobayashi, Yoshinori*
Japanese Journal of Applied Physics, 59(11), p.116504_1 - 116504_5, 2020/11
Positron annihilation lifetime measurements were performed on polyethylene films with thickness of 15
m - 2000m using a Na-22 positron source enclosed in a Kapton film. For thin films, some positrons will pass through the film and annihilate behind it. Using a single film in a commercial anti-coincidence system, by placing an annealed stainless steel (SUS304) cover behind the sample, it is possible to sufficiently measure the long lifetime ortho-positronium (o-Ps) component even in thin films. Additionally, calculated intensities of the o-Ps component determined from the estimated film transmittance agreed well with the measured values. Furthermore, by applying this method to uniaxially stretched UHMWPE, we were able to observe structural changes owing to the stretching consistent with shorter measured o-Ps lifetime and increased o-Ps intensity.
Takeda, Seiji; Sasaki, Toshihisa*; Nagasawa, Hirokazu; Kimura, Hideo
JAEA-Data/Code 2010-019, 61 Pages, 2010/11
JAEA-Data-Code-2010-019.pdf:1.47MB
In deep geological disposal or intermediate depth disposal, human intrusion, i.e. accidental excavation or drilling into the disposal site, may make a direct or indirect effect on the disposal system. Assessment of the human intrusion would need the examination of institutional control to reduce the probability of the intrusion occurring, the estimation of its probability, and the development of method to estimate its associated exposure of persons, as well as some foreign countries. Assuming that drilling action into the disposal site especially leads to the human proximity to the radioactive waste or the damage to the barrier system (drilling scenario), we have developed the evaluation code of radiological effect from the human intrusion into radioactive waste disposal system (HUINT). The evaluation code of human intrusion scenario, HUINT, can calculate the radiation exposure dose for the workers of a series of actions accompanied with drilling and for the workers and public people concerned with the reuse of drilling cores, identified with the actual information on drilling action in Japan. This report provides the descriptions of mathematical models on the drilling scenario, input specification and user information for execution of HUINT (user manual), and the result of verification for calculation with the models in HUINT.
Nagasawa, Hirokazu; Takeda, Seiji; Kimura, Hideo; Sasaki, Toshihisa*
JAEA-Data/Code 2010-018, 85 Pages, 2010/11
JAEA-Data-Code-2010-018.pdf:1.94MB
In deep geological disposal or intermediate depth disposal, human intrusion, i.e. accidental excavation or drilling into the disposal site, may make a direct or indirect effect on the disposal system. Assessment of the human intrusion would need the examination of institutional control to reduce the probability of the intrusion occurring, the estimation of its probability, and the development of method to estimate its associated exposure of persons, as well as some foreign countries. Assuming that drilling action into the disposal site especially leads to the human proximity to the radioactive waste or the damage to the barrier system (drilling scenario), we have collected both the data on borehole drilling implemented in Japan and information on actual situation of drilling activities. We have developed an assembly of the information mentioned above as database, including the model parameters used in the code to assess radiation dose for drilling scenario.
Nagasawa, Hirokazu; Takeda, Seiji; Kimura, Hideo
JAEA-Research 2010-023, 44 Pages, 2010/08
JAEA-Research-2010-023.pdf:3.43MB
In the safety assessment of geological disposal for high level radioactive wastes, it is important to develop the modelling for evaluating mechanical effects of crustal movements on the disposal system in Japan. In this study, the model on crustal movements is represented by accumulating two components of velocity magnitude of the crust to horizontal direction, caused by transient movements associated with fault and/or volcanic activities and ordinary movements with the other continuous factors. In this report, we provide the specification of the model on crustal movement and analyze the horizontal velocity in Tohoku region using the model. The results indicate that the spatial distribution of longitudinal velocities in Tohoku region is similar to that of the ordinary movements.
Takeda, Seiji; Yamaguchi, Tetsuji; Nagasawa, Hirokazu; Watanabe, Masatoshi; Sekioka, Yasushi; Kanzaki, Yutaka; Sasaki, Toshihisa; Ochiai, Toru; Munakata, Masahiro; Tanaka, Tadao; et al.
JAEA-Research 2009-034, 239 Pages, 2009/11
JAEA-Research-2009-034.pdf:33.52MB
In safety assessment for geological disposal of high level radioactive waste, it is of consequence to estimate the uncertainties due to the long-term frame associated with long-lived radionuclides and the expanded geological environment. The uncertainties result from heterogeneity intrinsic to engineered and natural barrier materials, insufficient understanding of phenomena occurring in the disposal system, erroneous method of measurement, and incomplete construction. It is possible to quantify or to reduce the uncertainties according to scientific and technological progress. We applied a deterministic and a Monte Carlo-based probabilistic method simulation techniques to the uncertainty analysis for performance of hypothetical geological disposal system for high level radioactive waste. This study provides the method to evaluate the effects of the uncertainties with respect to scenarios, models and parameters in engineering barrier system on radiological consequence. The results also help us to specify prioritized models and parameters to be further studied for long-term safety assessment.
Nagasawa, Hirokazu; Takeda, Seiji; Kimura, Hideo; Shiozaki, Isao*
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no abstracts in English
Nagasawa, Hirokazu; Takeda, Seiji; Kimura, Hideo; Sasaki, Toshihisa
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Nagasawa, Hirokazu; Kimura, Hideo; Takeda, Seiji
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Nagasawa, Hirokazu; Takeda, Seiji; Kimura, Hideo; Sasaki, Toshihisa
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Nagasawa, Hirokazu; Takeda, Seiji; Kimura, Hideo
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Nagasawa, Hirokazu; Takeda, Seiji; Sakai, Ryutaro; Kimura, Hideo
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Nagasawa, Hirokazu; Takeda, Seiji; Kimura, Hideo; Sakai, Ryutaro; Shiozaki, Isao*; Yamashita, Ryo*; Wakamatsu, Hisanori*; Ishibashi, Kazufusa*
no journal, ,
no abstracts in English
