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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.
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.
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.
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
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
Kimura, Hideo
Genshiryoku Bakkuendo Kenkyu, 8(2), p.103 - 114, 2002/03
no abstracts in English
Sakamoto, Yoshiaki; Ishii, Tomoaki*; Inagawa, Satoshi*; Gunji, Yasuyoshi*; Takebe, Shinichi; Ogawa, Hiromichi; Sasaki, Tomozo*
Genshiryoku Bakkuendo Kenkyu, 8(1), p.65 - 76, 2001/09
In order to study adsorption behavior of U series radionuclides(Pb, Ra, Th, Ac, Pa and U) in aerated zone environment (loam-rein water system) and aquifer environment(sand-groundwater system) for safety assessment of U bearing waste), pH dependence of distribution coefficients of each element have been obtained. The pH dependence of distribution coefficients of U, Ac, Th, Ra and Pb was analyzed by model calculation of adsorption behavior based on chemical forms of each elements and soil surface characteristics, which are a cation exchange capacity and surface charge. From model calculation of adsorption behavior, the distribution coefficients' values and adsorption behavior of Pb, Ra, Th, Ac and U could be showed by a combination of cation exchange and surface-complexation adsorption model.
Ishii, Tomoaki*; Inagawa, Satoshi*; Gunji, Yasuyoshi*; Sakamoto, Yoshiaki; Takebe, Shinichi; Ogawa, Hiromichi; Sasaki, Tomozo*
Genshiryoku Bakkuendo Kenkyu, 8(1), p.55 - 64, 2001/09
Distribution coefficients of Uranium series nuclide(Pb,Ra,Ac,Th,Pa and U) were obtained under aerated zone environment and aquifer environment, for the safety evaluation of shallow underground disposal of uranium bearing waste. The distribution coefficients of them on 4 kinds of soil such as the loam in the rain water as for aerated zone environment and on 3 kinds of soil and rock such as the sand in groundwater as for aquifer environment have been measured by batch method. The distribution coefficients in aerated zone environment were one or two orders in magnitude higher than that in aquifer environment, except Ac. And, there was approximately the linear correlation on the relationship between cation exchange capacity and specific surface area, which are representative physical property of the soil, and distribution coefficient of lead, radium and protactinium.
Sakai, Akihiro; Yoshimori, Michiro; Okoshi, Minoru; Yamamoto, Tadatoshi; Abe, Masayoshi
JAERI-Tech 2001-018, 88 Pages, 2001/03
JAERI-Tech-2001-018.pdf:5.66MB
no abstracts in English
Kimura, Hideo
KURRI-KR-56, p.95 - 108, 2001/03
no abstracts in English
Abe, Masayoshi
Dekomisshoningu Giho, (18), p.2 - 16, 1998/08
no abstracts in English
Fujiki, Kazuo; Nakamura, Hisashi
Proc. of the 1993 Int. Conf. on Nuclear Waste Management and Environmental Remediation,Vol. 3, p.321 - 327, 1993/00
no abstracts in English
Kamiyama, Hideo
KURRI-TR-349, p.16 - 22, 1991/00
no abstracts in English
Kagaku To Kogyo, 42(7), p.1240 - 1241, 1989/00
no abstracts in English
Yamamoto, Tadatoshi; ; Ogawa, Hiromichi;
Nihon Genshiryoku Gakkai-Shi, 30(10), p.942 - 949, 1988/10
Times Cited Count：5 Percentile：52.45(Nuclear Science & Technology)no abstracts in English
Izumo, Sari; Hayashi, Hirokazu; Nakata, Hisakazu; Kameo, Yutaka; Amazawa, Hiroya; Sakai, Akihiro
no journal, ,
no abstracts in English
