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Sakai, Akihiro; Kamei, Gento; Sakamoto, Yoshiaki
Nihon Genshiryoku Gakkai-Shi ATOMO
, 65(1), p.25 - 29, 2023/01
Currently, radioactive waste generated from research institutes, etc. is keeping in storage facilities without being disposed of. In order to solve this problem, the Japan Atomic Energy Agency (JAEA) is proceeding with the project for concrete-pit disposal and trench disposal of these waste. This paper introduces the characteristics of the waste and disposal facilities planned by the JAEA, as well as the status of development of the siting criteria for the disposal facility.
Nakamura, Mizuki; Izumo, Sari; Ogawa, Rina; Nakata, Hisakazu; Amazawa, Hiroya; Sakai, Akihiro
JAEA-Technology 2022-025, 73 Pages, 2022/12
JAEA-Technology-2022-025.pdf:1.64MB
Japan Atomic Energy Agency (JAEA) has been establishing as the implementing body of the near surface disposal of low-level radioactive waste (LLW) generated from research facilities and other facilities in order to actualize the near surface disposal. It is necessary to evaluate the effective doses by direct and skyshine 
-rays from disposal facilities and reduce the doses below the target dose (50
Sv/y) at the site boundary for the safety assessment during operation. It was shown at the results of conceptual design that the distance from the trench disposal facilities to site boundary needed to be kept more than 120m in order to satisfy the target dose. However, the design of trench disposal facilities was changed because of increasing amount of waste subject to the trench disposal. Therefore, the dose by skyshine -rays from trench disposal facilities was recalculated by use of two-dimensional discrete ordinates Sn code DOT 3.5. As a result, it was evaluated that the dose by skyshine -rays from each trench facility at the site boundary whose distance was 120m from a trench facility was lower than 50 Sv/y, respectively, and the dose added up the doses from trench facilities was also lower than 50 Sv/y. In addition, it was suggested to reduce the target skyshine dose by thickening the covered soil on the top layer.
Kyono, Atsushi*; Yamamoto, Genichiro*; Yoneda, Yasuhiro; Okada, Satoru*
Isotope News, (783), p.23 - 27, 2022/10
Mineral traps are attracting attention as an underground storage method for carbon dioxide. Carbon dioxide laden groundwater reacts with basalt to form magnesite. The formed magnesium carbonate phase varies in many ways, but we tried to clarify the structure because all of them pass through amorphous magnesium carbonate. Pair distribution function using high-energy X-ray diffraction revealed that amorphous magnesium carbonate has a structure similar to that of hydromagnesite. It can be said that it is a safe sequestration method as a carbon dioxide storage technology.
Sakai, Akihiro
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 29(1), p.48 - 54, 2022/06
no abstracts in English
Nakagawa, Akinori; Oyokawa, Atsushi; Murakami, Masashi; Yoshida, Yukihiko; Sasaki, Toshiki; Okada, Shota; Nakata, Hisakazu; Sugaya, Toshikatsu; Sakai, Akihiro; Sakamoto, Yoshiaki
JAEA-Technology 2021-006, 186 Pages, 2021/06
JAEA-Technology-2021-006.pdf:54.45MB
Radioactive wastes generated from R&D activities have been stored in Japan Atomic Energy Agency. In order to reduce the risk of taking long time to process legacy wastes, countermeasures for acceleration of waste processing and disposal were studied. Work analysis of waste processing showed bottleneck processes, such as evaluation of radioactivity concentration, segregation of hazardous and combustibles materials. Concerning evaluation of radioactivity concentration, a radiological characterization method using a scaling factor and a nondestructive gamma-ray measurement should be developed. The number of radionuclides that are to be selected for the safety assessment of the trench type disposal facility can decrease using artificial barriers. Hazardous materials, will be identified using records and nondestructive inspection. The waste identified as hazardous will be unpacked and segregated. Preliminary calculations of waste acceptance criteria of hazardous material concentrations were conducted based on environmental standards in groundwater. The total volume of the combustibles will be evaluated using nondestructive inspection. The waste that does not comply with the waste acceptance criteria should be mixed with low combustible material waste such as dismantling concrete waste in order to satisfy the waste acceptance criteria on a disposal facility average. It was estimated that segregation throughput of compressed waste should be increased about 5 times more than conventional method by applying the countermeasures. Further study and technology development will be conducted to realize the plan.
Sugaya, Toshikatsu; Abe, Daichi*; Okada, Shota; Nakata, Hisakazu; Sakai, Akihiro
JAEA-Technology 2021-004, 79 Pages, 2021/05
JAEA-Technology-2021-004.pdf:2.86MBJAEA-Technology-2021-004(errata).pdf:0.38MB
JAEA has aims to carry out near surface disposal of low-level radioactive waste generated from research, medical, and industrial facilities. Therefore, radioactivity concentration corresponding to dose criteria of near surface disposal for 220 nuclides in the waste were calculated for the purpose of discussion for radioactivity limits between trench and concrete vault disposal, and key nuclides related to them. We calculated the radioactivity concentrations with consideration of not only the exposure pathways used at calculation of the radioactivity concentration limits of waste packages for near surface disposal by Nuclear Safety Commission but also ones used at the concentration limits for intermediate depth disposal. We also assumed the capacities of the disposal facilities as 44,000 m
for pit disposal and 150,000 m for trench disposal. The radioactivity concentrations calculated in this report is used as the reference values because the disposal site has not been decided yet. Addition to this, the radioactivity concentrations will be revised according to circumstances of development of disposal facilities and so on. In the future, we will decide the radioactivity and radioactive concentration of a waste package described in the license application documents based on the dose assessment taken into consideration the disposal site conditions.
Izumo, Sari; Hayashi, Hirokazu; Nakata, Hisakazu; Amazawa, Hiroya; Motoyama, Mitsushi*; Sakai, Akihiro
JAEA-Technology 2018-018, 39 Pages, 2019/03
JAEA-Technology-2018-018.pdf:2.8MB
JAEA has planed the near surface disposal of LLW generated from research, industrial, and medical facilities. Maximum radioactivity concentration of each waste and total radioactivity of disposed wastes are needed to be less than the permitted values in the license of disposal facility. Thus, it is important not to evaluate the radioactivity of each waste in unduly conservative ways so as to dispose of the total amount of the waste that is originally planned. Accordingly, the detection limit is required to be as low as the clearance level for the very low level radioactive waste planned to be disposed of trench-type. In this report, the feasibility of the non-destructive assay method is studied by model calculations for gamma emitters. It is confirmed that the detection limit less than the clearance level can be achieved as regards the box type metal container that is difficult to measure. This report summarizes the requirements for the non-destructive measuring equipment.
Nakata, Hisakazu; Takao, Hajime*; Chijimatsu, Masakazu*; Noma, Yasutaka*; Amazawa, Hiroya; Sakai, Akihiro
JAEA-Technology 2018-014, 43 Pages, 2019/03
JAEA-Technology-2018-014.pdf:5.91MB
Japan Atomic Energy Agency plans to install disposal facilities for radioactive waste arising from research institutes. One relevant technical standard by the safety regulation is that the disposal facility shall be performance so as not to be left with harmful voids after backfilling with soil. Additionally no harmful void needs to exist in the waste packed in metal containers. The harmful void is supposed to result in the collapse of the disposal facility after structural materials of the container deteriorate and then become a state that can not retain the structure on its own. That leads to have an adverse impact on the facility such that the shape of cover soil deforms the way in which stagnant water is likely to occure. For which reason, a waste acceptance criteria relating to the quantity of voidage in a waste package needs to be defined quantitatively, which is preliminary less than 20% in a volum ratio based on this study.
Nakata, Hisakazu; Amazawa, Hiroya; Izumo, Sari; Okada, Shota; Sakai, Akihiro
Dekomisshoningu Giho, (58), p.10 - 23, 2018/09
Low level radioactive wastes are generated in the research and development of the nuclear energy, medical and industrial use of radioisotope except NPP in Japan. The disposal of wastes arising from NPP has already been implemented while not the one for wastes from research institutes etc. Japan Atomic Energy Agency therefore has been assigned an implementing organization for the disposal legally in 2008 in order to promote the disposal program as quickly and firmly as possible. Since then, JAEA has conducted their activity relating to the disposal facility design on generic site conditions and developing Waste Acceptance Criteria for LLW from research institutes. This report summarizes the WAC and current challenges.
Waste Technical Standards Working Group
JAEA-Review 2017-017, 112 Pages, 2017/11
JAEA-Review-2017-017.pdf:2.87MB
In Japan Atomic Energy Agency, JAEA, a Waste Technical Standards Working Group has established since FY2015. The Working Group is composed of the members from waste management sections in each site in JAEA and from Radioactive Waste Management and Disposal Project Department. In this Working Group, we discussed quality management on conditioning waste packages, methodologies to evaluate the radioactivity concentration and measures for dismantling waste. This annual report summarizes the results of discussion in FY2016.
Sakai, Akihiro; Kurosawa, Ryohei*; Totsuka, Masayoshi; Nakata, Hisakazu; Amazawa, Hiroya
JAEA-Technology 2016-032, 117 Pages, 2017/02
JAEA-Technology-2016-032.pdf:12.84MB
JAEA has been planning to implement near surface disposal of low level waste generated from research, medical, and industrial facilities. JAEA plans to carry out 3d analysis of groundwater flow in geological model around the disposal site because of development of migration assessment modeling of radioactivity materials in the site. In the safety demonstration test in JAEA, 3d analysis of groundwater flow was carried out on 1999. The analysis was calculated by using the code "3D-SEEP". But it is necessary to improve the conditions of the model in the analysis. Therefore, we improved the geological model which had been developed carried out 3d analysis of groundwater flow by using the current 3D-SEEP for the specified disposal site in the future. From the result, we expect that 3d analysis of groundwater flow in the environment around the specified near surface disposal site will be able to be sufficiently conducted by developing an appropriate model for the disposal site.
Masumoto, Kazuhiko*; Takeuchi, Ryuji
Oyo Chishitsu, 57(4), p.154 - 161, 2016/10
Fractures developing around the tunnel during the excavation result in issues related not only to the mechanical stability of the rock cavern, but also to the groundwater flow paths. In order to estimate the possibility of application of the GPR (Ground Penetration Radar) to estimate the fractures as low paths, the authors conducted the GPR survey along the side wall of 500 m access tunnel of the Mizunami Underground Research Laboratory of JAEA. The results of the profile measurements indicated that water-conductiong fractures were detected as a reflected waves using GPR survay. Furthermore, as the results of fixed-point measurements during the injection of the saline water, it could be indicated to estimate the flow paths of saline water in the fractures, in a non-destructive way, based on spectral analysis in the reflected waveforms of GPR.
Waste Technical Standards Working Group
JAEA-Review 2016-020, 61 Pages, 2016/09
JAEA-Review-2016-020.pdf:1.55MB
Radioactive Waste Management and Disposal Project Department has set up a Working Group for the purpose of sharing information within the Sector of Decommissioning and Radioactive Wastes Management of Japan Atomic Energy Agency, heading towards implementation of disposal of low level radioactive waste generated from research, medical and industrial facilities. Waste package quantities and its radioactivity inventory which are needed for disposal project planning and facility design, as well as methods for corresponding to the technical standards on confirmation related to waste disposal, radioactivity evaluation techniques and quality control methods have been addressed in the Working Group. This annual report summarizes the activities of the Working Group in the FY 2015 regarding quality management system related to the manufacturing of the waste packages, standard manual for radioactivity data acquisition of JAEA and future issues on the basis of the results by 2014.
Okada, Shota; Kurosawa, Ryohei; Sakai, Akihiro; Nakata, Hisakazu; Amazawa, Hiroya
JAEA-Technology 2015-016, 44 Pages, 2015/07
JAEA-Technology-2015-016.pdf:5.8MB
In this report, we calculated radioactivity concentration of radionuclides potentially contained in low level radioactive waste (LLW) generated from research, medical, and industrial facilities corresponding to dose criterion (10 Sv/y) for near surface disposal. 220 kinds of nuclides whose half-life are more than 30 days were selected. Radioactivity concentrations corresponding to dose criterion of 40 nuclides among 220 ones were calculated by using the representative model because the concentrations of 40 nuclides had not been calculated yet. Skyshine dose from each of 19 nuclides, whose radioactivity concentration were invalid values that are larger than the specific radioactivity of nuclides, during operation of disposal facility was calculated. These radioactivity concentrations can be used as criteria of categorization of LLW between trench type and concrete vault type disposal and of preliminary selection of important nuclides of these disposals in the generic conditions.
Tanaka, Tadao; Mukai, Masayuki; Nakayama, Shinichi
Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10
no abstracts in English
Hagiwara, Shigeru*; Sakamoto, Yoshiaki*; Takebe, Shinichi; Nakayama, Shinichi
JAERI-Data/Code 2004-004, 167 Pages, 2004/03
JAERI-Data-Code-2004-004.pdf:10.14MB
no abstracts in English
Hagiwara, Shigeru*; Sakamoto, Yoshiaki*; Takebe, Shinichi; Nakayama, Shinichi
JAERI-Data/Code 2004-003, 159 Pages, 2004/03
JAERI-Data-Code-2004-003.pdf:10.26MB
no abstracts in English
Tanaka, Tadao; Mukai, Masayuki; Maeda, Toshikatsu; Matsumoto, Junko; Ogawa, Hiromichi; Munakata, Masahiro; Kimura, Hideo; Bamba, Tsunetaka; Fujine, Sachio
Genshiryoku eye, 49(2), p.76 - 79, 2003/02
no abstracts in English
Hagiwara, Shigeru*; Sakamoto, Yoshiaki; Ogawa, Hiromichi; Nakayama, Shinichi
JAERI-Review 2002-024, 203 Pages, 2002/11
JAERI-Review-2002-024.pdf:15.79MB
Radioactive wastes arising from radioisotope facilities and nuclear research facilities should be disposed of in the surface of the earth, the shallow underground,the adequate depth and the deep undergruond according to radioactivity concentration, and should be managed during several hundreds years. For the selection of disposal site, it is necessary to survey the beginning of earth scientific phenomena observed in the Japanese Islands at present and to reconnoiter the prospective features. This report reviewed on the genesis and classification of sediments, earth scientific phenomena observed in the Japanese Islands and the feature of each place(10 districts) concerning to the Quaternary period in the newest geological time unit.
Takeda, Seiji; Kanno, Mitsuhiro; Minase, Naofumi; Kimura, Hideo
Journal of Nuclear Science and Technology, 39(8), p.929 - 937, 2002/08
no abstracts in English
