Saito, Tatsuo; Yamazawa, Hiromi*; Mochizuki, Akihito
Journal of Environmental Radioactivity, 255, p.107035_1 - 107035_14, 2022/12
The seasonal variation of dissolved U (DU) in Lake Biwa was reproduced by the following model and parameter research. The introduced models are the water-DU mass balance, and the ion exchange between UO and H on the lakeshore soil. The optimized parameters were the CEC of the lakeshore, TU as the sum of DU and AU (soil adsorbed U), kads and kdes as the first order reaction rate coefficients during rapid soil adsorption and desorption of U, respectively. Tabulated by the chemical equilibria constituting DU and analyzed the contribution of each chemical species, it is shown that the seasonal variation of DU is caused by the seasonal variation of pH. A correction to the ion-exchange equilibrium to shift to first order rate reaction only when the daily AU ratio increased above kads or decreased below kdes, improved the reproducibility of DU measurements and reproduced the delay of the DU peak from the pH peak.
Ieda, Junichi; Okayasu, Satoru; Harii, Kazuya*; Kobata, Masaaki; Yoshii, Kenji; Fukuda, Tatsuo; Ishida, Masahiko*; Saito, Eiji
IEEE Transactions on Magnetics, 58(8), p.1301106_1 - 1301106_6, 2022/08
The combination of spin-driven thermoelectric (STE) devices based on spin Seebeck effect (SSE), and radioactive isotopes as heat sources, has potential as a next-generation method of power generation in applications such as power supplies for space probes. However, there has been very limited knowledge available indicating the irradiation tolerance of spin thermoelectric devices. Through analysis using a heavy ion-beam accelerator and the hard X-ray photoemission spectroscopy (HAXPES) measurements, we show that a prototypical STE device based on YFeO/Pt heterostructures has tolerance to irradiation of high-energy heavy-ion beams. We used 320 MeV gold ion beams modeling cumulative damages due to fission products emitted from the surface of spent nuclear fuels. By varying the dose level, we confirmed that the thermoelectric and magnetic properties of the SSE elements are not affected by the ion-irradiation dose up to ions/cm fluence and that the SSE signal is extinguished around ions/cm, in which the ion tracks almost fully cover the sample surface. In addition, the HAXPES measurements were performed to understand the effects at the interface of YFeO/Pt. The HAXPES measurements suggest that the chemical reaction that diminishes the SSE signals is enhanced with the increase of the irradiation dose. We share the current understandings of the damage analysis in YFeO/Pt for developing better STE devices applicable to harsh environmental usages.
Ogawa, Rina; Abe, Daichi*; Sugaya, Toshikatsu; Sakuma, Kota; Saito, Tatsuo; Sakai, Akihiro
JAEA-Technology 2022-008, 46 Pages, 2022/05
Japan Atomic Energy Agency (JAEA) has planned to dispose of the Uranium-bearing waste, whose radioactivity concentration is low, in trench disposal facility. In Japan, uranium is a material to impact on human health, therefore Environmental quality standards for water pollution for uranium has been established, and the standard value is 0.002mg/L. Safety of trench disposal facilities will be assessed that radionuclides contained in the radioactive waste are transferred to the biosphere by seepage water and groundwater. Therefore, JAEA considers that not only dose evaluation but also environmental pollution evaluation is needed as a safety assessment. In this report, we examined whether the concentration of uranium leaching from the trench facility in the aquifer can meet the Environmental quality standards. In addition, parameter study under various conditions of disposal facility were done. Based on the results, conditions and issues of future basic design of trench disposal facility were discussed. The uranium concentration in the aquifer was calculated by the one-dimensional dose evaluation code "GSA-GCL2" for the disposal of LLW. As the result, the uranium concentration in the aquifer significantly changed depending on the conditions of design of disposal facility and so on. However, if the shape and arrangement of the trench facility to groundwater flow direction, the distribution coefficient of uranium of the waste layer, the specification of the impermeable layer and their combination are appropriately designed we consider that the uranium concentration of aquifer can made to adapt the environmental quality standard.
FNCA Radiation Safety and Radioactive Waste Management Newsletter (Internet), (17), p.6 - 7, 2022/03
In the Asian Nuclear Cooperation Forum (FNCA) newsletter, the mechanism for disposal of low-level radioactive waste generated from nuclear research facilities and facilities using RI was briefly explained. The outline of domestic guidelines on the handling of NORM was also explained, which has been the theme of FNCA since last year.
Saito, Tatsuo; Sato, Kazuhiko; Yamazawa, Hiromi*
Journal of Environmental Radioactivity, 237, p.106708_1 - 106708_9, 2021/10
We succeeded at numerical reproduction of dissolved U concentrations from column experiments with PO-treated Hanford 300 Area sediment. The time-series curves of dissolved U concentrations under various Darcy flow rate conditions were reproduced by the numerical model in the present study through optimization of the following parameters:(i) the mass of U in mobile domain (on surface soil connected to the stream) and the rest of the total U left as precipitation in immobile domain (isolated in deep soil);(ii) the mixing ratio between immobile and mobile domains, to fit the final recovering curve of concentration; and (iii) the cation exchange capacity (CEC) and equilibrium constant (k) of the exchange reaction of UO and H on simulated soil surface (), to fit the transient equilibrium concentration, forming the bed of the bathtub curve.
Yasuda, Hiroshi*; Fumoto, Hiromichi*; Saito, Tatsuo
Nihon Genshiryoku Gakkai-Shi ATOMO, 63(8), p.610 - 614, 2021/08
Regarding the handling of uranium bearing waste, which is contaminated with uranium, which is a naturally occurring radionuclide, and its descendant nuclides, in recent years, the Japan Nuclear Regulatory Commission, etc. have been carefully and actively deliberated based on the knowledge of natural science and safety engineering. It was carried out, and as of March 2021, a certain policy has been shown. On the other hand, when disposing of uranium waste, which may cause dose exposure to future generations, the authors consider not only the science and engineering perspectives that have been conducted so far, but also the humanities and social science perspectives. We have been discussing with experts in related fields, thinking that it is necessary. In this report, we will introduce the background that brought about such an idea and the direction of future discussions.
Okayasu, Satoru; Harii, Kazuya*; Kobata, Masaaki; Yoshii, Kenji; Fukuda, Tatsuo; Ishida, Masahiko*; Ieda, Junichi; Saito, Eiji
Journal of Applied Physics, 128(8), p.083902_1 - 083902_7, 2020/08
Saito, Tatsuo; Kobayashi, Shinichi*; Zaitsu, Tomohisa*; Shimo, Michikuni*; Fumoto, Hiromichi*
Hoken Butsuri (Internet), 55(2), p.86 - 91, 2020/06
Safety cases for disposal of uranium bearing waste and NORM with uranium has not yet been fully developed in Japan, because of safety assessment of extraordinary long timespan and uncertainty in unexpected incidents with uncompleted radon impact evaluation measures arising from uranium waste disposal facility in far future. Our task group of radiation protection for wastes with natural radioactive nuclides studied some safety cases with disposal of uranium bearing waste and NORM in terms of nuclides, U-235, U-238 and their progenies, and comprehensively discussed the current state of their disposal in comparison to the ideas of international organizations such as ICRP and IAEA. We developed our ideas for long term uncertainty and radon with the knowledge of experts in each related area of direction, repeating discussions, focusing out the orientation of each directions, and outlined the recommendations with our suggestions of solving important issues in the future to be addressed.
Kobata, Masaaki; Yoshii, Kenji; Fukuda, Tatsuo; Kawasaki, Ikuto; Okane, Tetsuo; Yamagami, Hiroshi; Yaita, Tsuyoshi; Harii, Kazuya; Ieda, Junichi; Okayasu, Satoru; et al.
JPS Conference Proceedings (Internet), 30, p.011192_1 - 011192_6, 2020/03
High energy X-ray photoelectron spectroscopy (HAXPES) measurements were carried out for the Spin Seebeck system Pt/YFeO(YIG). This system was found to show anomalous Hall effect, possible due to the formation of intermetallic compounds between Fe and Pt. To reveal this possibility, we have measured the Fe 1s photoelectron peaks by using HAXPES. It was found that the Fe ions consist of Fe in YIG and metallic Fe. The formation of the metallic state is consistent with the proposed origin of the anomalous Hall effect. Other spectra such as Pt 4f will be presented at the conference.
Chino, Masamichi; Terada, Hiroaki; Nagai, Haruyasu; Katata, Genki; Mikami, Satoshi; Torii, Tatsuo; Saito, Kimiaki; Nishizawa, Yukiyasu
Scientific Reports (Internet), 6, p.31376_1 - 31376_14, 2016/08
Malins, A.; Kurikami, Hiroshi; Nakama, Shigeo; Saito, Tatsuo; Okumura, Masahiko; Machida, Masahiko; Kitamura, Akihiro
Journal of Environmental Radioactivity, 151(Part 1), p.38 - 49, 2016/01
The air dose rate in an environment contaminated with Cs and Cs depends on the amount, depth profile and horizontal distribution of these contaminants within the ground. This paper introduces and verifies a tool that models these variables and calculates ambient dose equivalent rates at 1 m above the ground. Good correlation is found between predicted dose rates and dose rates measured with survey meters in Fukushima Prefecture in areas contaminated with radiocesium from the Fukushima Dai-ichi Nuclear Power Plant accident. Better predictions are obtained by modeling the horizontal distribution of radioactive cesium across an area if multiple soil samples are available, as opposed to assuming a spatially homogeneous contamination distribution. Reductions seen in air dose rates above flat, undisturbed fields in Fukushima Prefecture are consistent with decrement by radioactive decay and downward migration of cesium into soil. Analysis of remediation strategies for farmland soils confirmed that topsoil removal and interchanging a topsoil layer with a subsoil layer result in similar reductions in the air dose rate.
Kitamura, Akihiro; Kurikami, Hiroshi; Yamaguchi, Masaaki; Oda, Yoshihiro; Saito, Tatsuo; Kato, Tomoko; Niizato, Tadafumi; Iijima, Kazuki; Sato, Haruo; Yui, Mikazu; et al.
Nuclear Science and Engineering, 179(1), p.104 - 118, 2015/01
The prediction of the distribution and fate of radioactive materials eventually deposited at surface in the Fukushima area is one of the main objectives and expected to be achieved in an efficient manner. In order to make such prediction, a number of mathematical models of radioactive contaminants, with particular attention on cesium, on the land and in rivers, lakes, and estuaries in the Fukushima area are developed. Simulation results are examined with the field investigations simultaneously implemented. The basic studies of the adsorption/absorption mechanism of cesium and soils have been performed to shed light on estimating distribution coefficient between dissolved contaminant and particulate contaminant.
Saito, Tatsuo; Sakai, Akihiro; Sato, Kazuhiko; Yagi, Naoto; Hata, Haruhi; Fumoto, Hiromichi*; Kawagoshi, Hiroshi; Hasegawa, Makoto
JAEA-Review 2014-021, 30 Pages, 2014/07
Japan Atomic Energy Agency surveyed the reference cases for the disposal of uranium bearing waste in low activity concentration as the contents of their own category 2 waste disposal facility for the Research and Development Activities. We reviewed the concepts mentioned in IAEA and ICRP documents, reference cases of uranium bearing waste disposal in selected countries (USA, Canada, UK, France and Sweden), and the disposal styles of long-lived radioactive waste were summarized, and the action items for application to the disposal system of our country was arranged. The disposal facilities in selected countries can be classified into 2 types with the length of performance assessment period for intruder scenario. They are long term assessment type and short term assessment type. It seems that the disposal system construction in category 2 waste disposal is the most realistic since there are many precedence examples of each country. Correspondence of 2 types of these disposal facilities is useful as a reference case.
Sato, Kazuhiko; Sakai, Akihiro; Hata, Haruhi; Fumoto, Hiromichi*; Kawagoshi, Hiroshi; Saito, Tatsuo; Hasegawa, Makoto
JAEA-Review 2014-006, 78 Pages, 2014/03
In this paper, we report the result of survey for basic principle of safety assessment for long-lived low-level (LL-LL) waste disposal and experience of the industrial waste disposal sites for uranium bearing waste in France, UK and Sweden, following the report of survey for U.S.A. and Canada published in December 2013.
Hasegawa, Makoto; Saito, Tatsuo; Zaitsu, Tomohisa; Sato, Kazuhiko; Sakai, Akihiro; Fumoto, Hiromichi*
JAEA-Review 2013-043, 42 Pages, 2013/12
Uranium bearing waste in Japan is not included in Category-2 radioactive waste disposal in NSCRG: F-RW-I.02 (published in August 2010, NSC Japan). Therefore, disposal of uranium bearing waste should be considered in institutionalization. In charge of the consideration, it is thought effective to refer to the proven tactics of the uranium waste disposal in overseas and the information on a safe regulatory system. Since the view of regulations and enterprises in this field are progressing day by day, renewal of the existing information of disposal of the uranium waste in each country is required. Furthermore, amendment of the U.S. federal rule aiming at safety disposal of depleted uranium is in progress. It is important to collect and arrange the latest information on the two above-mentioned points. Therefore, it visited the disposal responsible organization and regulatory agency of the disposal site of the uranium waste in the U.S. and Canada, and held institution investigations and interviews paying attention to the following four items: (1) "amendment of the U.S. 10CFR61", (2) "Safety evaluation of uranium bearing waste", (3) "Disposal site design", (4) "Stakeholder involvement".
Takebe, Shinichi; Sasaki, Toshihisa; Saito, Tatsuo; Yamaguchi, Naoko
JAEA-Technology 2013-033, 87 Pages, 2013/11
Materials, etc. in a non-controlled area is, if the criteria (10 microsieverts per year) listed below that in "A guideline regarding treatment of materials in nuclear facilities considering the influence of fallout released from the accident of TEPCO's Fukushima Dai-ichi Nuclear Power Station" (March 30, 2012), that in accordance with relevant laws and regulations, such as "Waste Disposal and Cleaning Act" (Act No. 137 of 1970), effective use as a resource or be properly disposed of is required. In this paper, in order to effectively use as resources or properly disposed of the materials, etc. in a non-controlled area, radioactivity concentration of materials, etc. in you see " For clearance level specified in Radiation Hazards Prevention Law" and "Radionuclide Concentrations for Materials not Requiring Treatment as Radioactive Wastes Generated from Dismantling etc. of Reactor Facilities and Nuclear Fuel Use Facilities (in Japanese), NSC Japan, 2005." corresponds to the dose of the above criteria the presented results have been estimated as an example.
Kokubu, Yoko; Nishizawa, Akimitsu*; Suzuki, Mototaka*; Owaki, Yoshio*; Nishio, Tomohiro*; Matsubara, Akihiro; Saito, Tatsuo; Ishimaru, Tsuneari; Umeda, Koji; Hanaki, Tatsumi
Nuclear Instruments and Methods in Physics Research B, 294, p.43 - 45, 2013/01
The Tono Geoscience center of JAEA installed the JAEA-AMS-TONO system at 1997. Since 1998, the system has routinely used for C-AMS. Recently, about 800 samples/y have been measured mainly for studies of neotectonics and hydrogeology in relation to research of geosphere stability for long-term Isolation of high-level radioactive waste. Under the common-use facility program, the system has also been used by researchers of universities and other institutes. In addition, Be-AMS has been developed for geochronological study. A gas ionisation detector was exchanged. As the detector has a gas absorber cell which has larger volume than the previous one, it is possible to remove B efficiently. Test measurement by using several standard samples supplied from University of California, Berkeley was performed. Ratios of Be/Be were comparable to the certified values, indicating that our system has sufficient ability to be useful to Be-AMS.
Kusano, Tomohiro; Nohara, Tsuyoshi; Umeda, Koji; Ishimaru, Tsuneari; Hanamuro, Takahiro; Saito, Tatsuo; Yasue, Kenichi; Niwa, Masakazu; Shimada, Koji; Yamada, Kunimi; et al.
JAEA-Research 2009-022, 47 Pages, 2009/09
The Japanese islands are located in the tectonically active Circum-Pacific Mobile Belt. As a result, Japan has a high frequency of earthquakes and eruptions. Special consideration is given to the long-term stability of the geological environment, taking into account volcanism, faulting, uplift, denudation, climatic change and sea-level change in Japan. Development of research/prediction technologies for geotectonic events has been carried out to evaluate the long-term stability of the geological environment in Japan. In fiscal year 2007, we carried out the following researches, to confirm existence of the phenomena that have influences on geological disposal system (e.g., active faulting, volcanism), and to develop the investigation techniques to reconstruct the history of these phenomena. For studies of faulting and seismic activity, we developed the investigation techniques to research distribution of crush zone, process of faulting, activity, and so on. For volcanological and geothermal studies, we developed a technique for detecting crustal magma and/or geothermal fluid in deep underground. For studies of uplift/denudation and climatic/sea-level changes, we extracted investigation techniques for landform developments and uplift rate with river terraces.
Nakatsuka, Noboru; Nohara, Tsuyoshi; Umeda, Koji; Ishimaru, Tsuneari; Hanamuro, Takahiro; Saito, Tatsuo; Yasue, Kenichi; Niwa, Masakazu
JAEA-Review 2008-039, 19 Pages, 2008/09
The Japanese islands are located in the tectonically active Circum-Pacific Mobile Belt. As a result, Japan has a high frequency of earthquakes and eruptions. Special consideration is given to the long-term stability of the geological environment, taking into account volcanism, faulting, uplift, denudation, climatic change and sea-level change in Japan. Development of research/prediction technologies for geotectonic events has been carried out to evaluate the long-term stability of the geological environment in Japan. During fiscal year 2008, research/prediction about the following items will be carried out. Concerning earthquake and fault movement, we continue to develop research techniques for evolutional history and activity of fault, and carry out case studies for development of effective assessment model in the fault zones will be carried out. For volcanological and geothermal studies, we are planning to provide an integrated approach for detecting crustal magma and/or geothermal fluid in deep underground using geophysical and geochemical data, and models assessing the likelihood of future volcanism and its influence on geological environment. Concerning uplift, denudation, climatic change and sea-level change, we plan to arrange research techniques for reconstruction of paleo-topography and paleo-climate, and to establish a simulation model for landform development. Concerning a general evaluation study about the long-term stability of the geological environment, information maintenance about a change of geological environment with hydrothermal activity, and development of simulation techniques for groundwater flow related by crustal movement, climatic change will be carried out. In addition, maintenance of development of analytical methods to perform the data acquisition that is necessary for these studies will be carried out.
Nohara, Tsuyoshi; Umeda, Koji; Sasao, Eiji; Hanamuro, Takahiro; Saito, Tatsuo; Yasue, Kenichi; Niwa, Masakazu; Mashima, Hidehisa*; Shimada, Koji; Yamada, Kunimi; et al.
JAEA-Research 2008-062, 61 Pages, 2008/07
The Japanese islands are located in the tectonically active Circum-Pacific Mobile Belt. As a result, Japan has a high frequency of earthquakes and eruptions. Special consideration is given to the long-term stability of the geological environment in Japan. Development of research/prediction technologies for geotectonic events has been carried out to evaluate the long-term stability of the geological environment in Japan. During fiscal year 2006, we carried out the following researches, to confirm existence of the phenomena that have influences on geological disposal system, and to develop the research techniques to reconstruct the history of these phenomena. For studies of active faulting and seismic activity, we reviewed the existing techniques to research past activities and distribution of active faults (migration, extension, development process of a deformation zone). For volcanological and geothermal studies, we extracted a technique for detecting crustal magma and/or geothermal fluid in deep underground using geophysical and geochemical data, and models assessing the likelihood of future volcanism and its influence on geological environment. For studies of uplift/denudation and climatic/sea-level change, we constructed conceptual models such as landform development model.