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Journal Articles

Basics of nuclear fuel cycle and environment

Sakamoto, Yoshiaki

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 30(1), p.15 - 18, 2023/06

The entire process of nuclear power generation is called the nuclear fuel cycle, and each process generates various types of radioactive waste. These radioactive wastes are generated from the operation and decommissioning of these facilities, and are treated and disposed of appropriately according to their radioactivity concentrations and properties. This paper describes the basic outline of the nuclear fuel cycle and the fundamentals of the treatment and disposal of radioactive waste (including radioactive waste from the use of radioactive materials in facilities other than the nuclear fuel cycle), called the back end of the nuclear fuel cycle.

Journal Articles

Toward realizing near surface disposal of LLW generated from research facilities, etc.; Status of development for safety of the disposal by JAEA

Sakai, Akihiro; Kamei, Gento; Sakamoto, Yoshiaki

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 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.

Journal Articles

Overall optimization of radioactive waste processing and disposal for problematic waste management

Nakagawa, Akinori; Sasaki, Toshiki; Sakamoto, Yoshiaki

Radioactive Waste Management; Solutions for a Sustainable Future (Supplement) (Internet), 7 Pages, 2023/00

Japan Atomic Energy Agency (JAEA) has stored radioactive wastes generated from R&D activities related to nuclear science and technology. A part of these wastes contains compressed wastes without prior radiological, chemical or physical characterization assessed, as well as mixed wastes containing lead and mercury with little information about its contents. Pre-treatment and radiological characterization efforts for such problematic wastes are very time consuming and costly. In order to optimize the processing and disposal of the problematic wastes, a method to balance the processing work and disposal facility robustness was studied. Work analysis of waste processing showed bottleneck processes, such as radiological characterization and segregation of hazardous materials and combustibles. Establishment of a conservative scaling factor method and non-destructive gamma-ray measurement enable easier radiological characterization. Hazardous materials will be identified using records and nondestructive inspection. The waste identified as hazardous will be unpacked and segregated. Based on preliminary survey of about 1,000 drums, only 10 % of stored drums contain hazardous materials and need segregation. Regarding the separation of combustibles, total volume of the combustibles will be evaluated using nondestructive inspection technique such as high-energy X-ray CT and the waste that does not comply with the waste acceptance criteria should be mixed with waste containing a small amount of combustibles 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.

Journal Articles

Design, construction and monitoring of temporary storage facilities for removed contaminants

Saegusa, Hiromitsu*; Funaki, Hironori; Kurikami, Hiroshi; Sakamoto, Yoshiaki; Tokizawa, Takayuki*

Insights Concerning the Fukushima Daiichi Nuclear Accident, Vol.4; Endeavors by Scientists, p.170 - 187, 2021/10

Removed contaminants including soil, grass and trees are to be stored safely at temporary storage facilities for several years, after which they will be transferred to a planned interim storage facility. The decontamination pilot project was carried out in both the restricted and planned evacuation areas in order to assess decontamination methods and demonstrate measures for radiation protection of workers. Fourteen temporary storage facilities of different technical specifications were designed and constructed under various topographic conditions and land use. In order to support the design, construction and monitoring of temporary storage facilities for removed contaminants during the full-scale decontamination within the prefecture of Fukushima, technical know-how obtained during the decontamination pilot project has been identified and summarized in this paper.

JAEA Reports

Basic policy for rational measures of radioactive waste processing and disposal; Results of studies for acceleration of waste processing

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.

Journal Articles

Current status of low level radioactive wastes generated from research, industrial and medical

Sakamoto, Yoshiaki

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 26(2), p.127 - 132, 2019/12

JAEA has promoted near surface disposal project for low-level radioactive wastes generated from research, industrial and medical facilities after receiving project approval from the government in 2009. This kind of low level radioactive wastes which were arising from the 1940s are still keeping in each storage buildings. For immediate treatment and disposal of the wastes, technical issue and commercialization of the disposal project are studied by JAEA. The outline of current status of the disposal project of JAEA and some approach to push forward rational treatment and disposal system are presented.

Journal Articles

Approach for the treatment and disposal of dismantling waste (Research reactor)

Sakamoto, Yoshiaki

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 24(2), p.141 - 146, 2017/12

Some research reactors are under decommissioning or preparation for application of decommissioning license for regulation authority in our country. The reasonable treatment and disposal of dismantling waste is important for decommissioning of research reactors. Therefore, in this paper, JAEA's approach of the treatment and disposal of dismantling waste was introduced from the point of view of disposal of low level radioactive waste arising from research, industrial and medical facilities.

Journal Articles

Challenges for management of radioactively contaminated wastes and volume reduction and reuse/recycling of removed soil derived from the activities for environmental remediation after the Fukushima Daiichi Nuclear Power Station accident, 5; Cost evaluation method for the disposal of low level radioactive waste

Nakata, Hisakazu; Sakai, Akihiro; Amazawa, Hiroya; Sakamoto, Yoshiaki

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 59(8), p.447 - 449, 2017/08

Removed soil except those that may be reusable/recyclable would be finally disposed of. A general view is obtained in regards to a disposal concept of low level radioactive wastes generated from research, industrial and medical facilities, for the purpose of contributing to designing final disposal facilities of removed soil. It is analyzed to investigate the issues relating to cost evaluation in order to reasonably carry out that design, referring to a cost evaluation methodology applied to a trench-type disposal facility, which has been planned by JAEA, with impermeable layers.

JAEA Reports

Study on the evaluation method to determine the radioactivity concentration in radioactive waste generated from post-irradiation examination facilities, 2

Tsuji, Tomoyuki; Hoshino, Yuzuru; Sakai, Akihiro; Sakamoto, Yoshiaki; Suzuki, Yasuo*; Machida, Hiroshi*

JAEA-Technology 2017-010, 75 Pages, 2017/06

JAEA-Technology-2017-010.pdf:2.31MB

It is necessary for reasonable disposal to be studied on evaluation methods to determine radioactivity concentrations in the radioactive wastes, which is generated from post-irradiation examination (PIE) facilities, for establishment of reasonable confirmation methods concerning radioactive wastes generated from research, industrial, and medical facilities. It has been chosen the PIE facilities of NUCLEAR DEVELOPMENT CORPORATION as a model for this study. As a result, it has been confirmed that the theoretical methods are applied for the important nuclides (H-3, C-14, Co-60, Ni-63, Sr-90, Tc-99, Cs-137, Eu-154, U-234, U-235, U-238, Pu-238, Pu-239, Pu-240, Pu-241, Am-241 and Cm-244).

Journal Articles

Development of the reasonable confirmation methods concerning radioactive wastes from research facilities

Hayashi, Hirokazu; Okada, Shota; Izumo, Sari; Hoshino, Yuzuru; Tsuji, Tomoyuki; Nakata, Hisakazu; Sakai, Akihiro; Amazawa, Hiroya; Sakamoto, Yoshiaki

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 7 Pages, 2017/04

A near surface disposal for low-level radioactive waste (LLW) generated from commercial nuclear power plants (NPP) is operating in Japan. However, the disposal of LLW from other nuclear facilities and radioisotope utilization facilities has not yet been implemented. Japan Atomic Energy Agency (JAEA) plans to implement the near surface disposal. In order to be disposed of these wastes, it must be confirmed by the regulator that each waste package (radioactive waste solidified with filling materials, such as cement, in a container by a regulated method is termed a waste package) conforms to technical standards that aim for safe disposal. JAEA has studied reasonable confirmation methods to demonstrate the conformity of the waste package to the technical standard as NPP operators have studied it. This report describes the outline of our activities focused on development of the confirmation method applicable to radioactive wastes from research facilities.

JAEA Reports

Technological study about a disposal measures of low-level radioactive waste including uranium and long-half-life radionuclides

Sugaya, Toshikatsu; Nakatani, Takayoshi; Sasaki, Toshihisa*; Nakamura, Yasuo*; Sakai, Akihiro; Sakamoto, Yoshiaki

JAEA-Technology 2016-036, 126 Pages, 2017/02

JAEA-Technology-2016-036.pdf:7.28MB

At the Radioactive Waste Management and Disposal Project Department Sector of Decommissioning and Radioactive Waste Management, we performed the technological study about the disposal measures of the low-level radioactive waste targeted for uranium-bearing waste and intermediate depth disposal-based waste occurring from the process of the nuclear fuel cycle.

Journal Articles

Disposal project for LLW and VLLW generated from research facilities in Japan; A Feasibility study for the near surface disposal of VLLW that includes uranium

Sakai, Akihiro; Hasegawa, Makoto; Sakamoto, Yoshiaki; Nakatani, Takayoshi

Proceedings of International Conference on the Safety of Radioactive Waste Management (Internet), p.98_1 - 98_4, 2016/11

The radioactivity of uranium-bearing waste contaminated by refined uranium increases with the production of its progeny on a long-term timescale. Therefore, the long-term safety concept of the near surface disposal of uranium-bearing waste is very important. The Japan Atomic Energy Agency (JAEA) examines disposal safety by controlling the average uranium radioactivity concentration in each section of disposal facility and performing safety assessment for very conservative assumptions.

Journal Articles

Summaries of the disposal business of low level radioactive waste arising from research, industrial and medical facilities

Sakamoto, Yoshiaki

Genkan Senta Topikkusu, (115), p.2 - 12, 2015/09

JAEA is going to push forward undergrounding disposal business of low level radioactive waste arising from the research facilities etc. in our country. The conceptual design of the trench facilities and the concrete pit facilities was carried out for total approximately 600,000 of drums as 200L drum of LLW in operation period of 50 years. In this lecture, outline of the disposal business and research activities about durability of a geomembrane lines for trench disposal facility and waste confirmation technology will be presented.

Journal Articles

Radiocaesium activity concentrations in parmelioid lichens within a 60 km radius of the Fukushima Dai-ichi Nuclear Power Plant

Dohi, Terumi; Omura, Yoshihito*; Kashiwadani, Hiroyuki*; Fujiwara, Kenso; Sakamoto, Yoshiaki; Iijima, Kazuki

Journal of Environmental Radioactivity, 146, p.125 - 133, 2015/08

 Times Cited Count:19 Percentile:53.13(Environmental Sciences)

Radiocaesium activity concentrations ($$^{134}$$Cs, $$^{137}$$Cs) were measured in parmelioid lichens collected within the Fukushima Prefecture approximately 2 y after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. A total of 44 samples consisting of nine species were collected at 16 points within a 60 km radius of the FDNPP. The activity concentration of $$^{134}$$Cs ranged from 4.6 to 1000 kBq kg$$^{-1}$$ and for $$^{137}$$Cs ranged from 7.6 to 1740 kBq kg$$^{-1}$$. A significant positive correlation was found between the $$^{137}$$Cs activity concentration in lichens and the $$^{137}$$Cs deposition density on soil, based on the calculated Spearman's rank correlation coefficients as $$r$$ = 0.90 ($$P$$ $$<$$ 0.01). The two dominant species, Flavoparmelia caperata and Parmotrema clavuliferum, showed strong positive correlations, for which the r values were calculated as 0.92 ($$P$$ $$<$$ 0.01) and 0.90 ($$P$$ $$<$$ 0.01) respectively. Therefore, they are suggested as biomonitoring species for levels of radiocaesium fallout within the Fukushima Prefecture.

JAEA Reports

Study on the evaluation method to determine the radioactivity concentration waste generated from post-irradiation examination facilities

Hoshino, Yuzuru; Sakamoto, Yoshiaki; Muroi, Masayuki*; Mukai, Satoru*

JAEA-Technology 2015-015, 96 Pages, 2015/07

JAEA-Technology-2015-015.pdf:20.34MB

In order to dispose of the radioactive waste which generates from post-irradiation examination (PIE) facilities, the common evaluation method of radioactivity in wastes from PIE should be established by the actual data such as radioactivity values and the theoretical calculation. In this study, the radioactivity concentrations of 17 nuclides (H-3, C-14, Co-60, Ni-63, Sr-90, Tc-99, Cs-137, Eu-154, U-234, U-235, U-238, Pu-238, Pu-239, Pu-240, Pu-241, Am-241, Cm-244) in combustible wastes stored in NUCLEAR DEVELOPMENT CORPORATION were measured from 3 samples and the radioactivity was calculated by ORIGEN-2 based on initial contents and operation record of the spent fuel. From the comparison of the obtained data by the radiological measurement with the calculated values, the subject to be solved for establishment of the radioactivity evaluation method for PIE was extracted.

Journal Articles

Outline of Investigation for radiocaesium concentrations in lichens after Fukushima Dai-ichi Nuclear Power Plant accident

Dohi, Terumi; Omura, Yoshihito*; Kashiwadani, Hiroyuki*; Fujiwara, Kenso; Sakamoto, Yoshiaki; Iijima, Kazuki

Raiken, 18(1), p.11 - 13, 2014/12

no abstracts in English

JAEA Reports

Evaluation of infiltration water through the upper cover soil in trench type disposal facility for low level radioactive wastes generated from research, industrial and medical facilities

Kurosawa, Ryohei; Sakai, Akihiro; Nakata, Hisakazu; Amazawa, Hiroya; Sakamoto, Yoshiaki

JAEA-Technology 2014-013, 89 Pages, 2014/06

JAEA-Technology-2014-013.pdf:23.93MB

In the safety assessment for the trench disposal facilities, outflow of radioactive material to the environment is assumed to be due to the percolating rain water into the waste layer, because the waste layer is established above the groundwater level. Therefore, in dose assessment of trench type disposal facilities, it is important to evaluate how the structure of the upper cover soil layers affects the suppressed amount of water infiltration to the waste layer due to rainfall.

JAEA Reports

Sensitivity analysis related to site environmental conditions of near surface disposal of radioactive wastes generated from research, industrial and medical facilities

Sakai, Akihiro; Kurosawa, Ryohei; Hara, Hironori*; Nakata, Hisakazu; Amazawa, Hiroya; Arikawa, Masanobu*; Sakamoto, Yoshiaki

JAEA-Technology 2013-039, 228 Pages, 2014/02

JAEA-Technology-2013-039.pdf:24.05MB

The sensitivity analysis of doses in terms of the environmental conditions was performed by statistical method in order to make the technical basis for the siting criteria of near surface disposal facility for low level radioactive waste generated from research, industrial and medical facilities. Doses calculated at all assumed pathways in more than 97.5% of calculation cases were able to be reduced below the target dose after control period (0.01 mSv/y) by means of equipping the disposal facility with additional engineered barriers. As a result, we concluded it was possible to safely and rationally design disposal facilities in most of the environmental parameters related to safety assessment. Another sensitivity analysis was done in order to discuss the area of disposal site. Dose at the site boundary were able to be reduce below the target dose during operation (0.05 mSv/y) whenever the distances from these facilities to the site boundary were more than 120 m, respectively.

JAEA Reports

Durability test of geomembrane liners presumed to avail near surface disposal facilities for Low-level waste generated from research, Industrial and Medical facilities

Nakata, Hisakazu; Amazawa, Hiroya; Sakai, Akihiro; Kurosawa, Ryohei; Kanno, Naohiro*; Kashima, Takahiro*; Sakamoto, Yoshiaki

JAEA-Technology 2013-036, 47 Pages, 2014/02

JAEA-Technology-2013-036.pdf:5.27MB

The Low-level Radioactive Waste Disposal Project Center will construct near surface disposal facilities. The disposal facilities consist of concrete pit type for low-level radioactive wastes and trench type for very low level radioactive wastes. As for the trench type disposal facility, two kinds of facility designs are on projects -one for normal trench type disposal facilities and the other for trench type disposal facilities with geomembrane liners that could prevent from causing environmental effects of non radioactive toxic materials. This study examined mechanical strength and permeability properties to assess the durability on the basis of an indoor accelerated exposure experiment targeting the liner materials presumed to avail the conceptual design so far. Its results will be used for the basic and detailed design henceforth by confirming the empirical degradation characteristic with the progress of the exposure time.

Journal Articles

Design, construction and monitoring of temporary storage facilities for removed contaminants

Saegusa, Hiromitsu; Funaki, Hironori; Kurikami, Hiroshi; Sakamoto, Yoshiaki; Tokizawa, Takayuki

Nihon Genshiryoku Gakkai Wabun Rombunshi, 12(1), p.1 - 12, 2013/03

Since the Fukushima Daiichi Nuclear Power Plant accident caused by the Tohoku Region Pacific Coast Earthquake, decontamination work has been conducted. Decontamination wastes including removed soil, grass and trees are to be stored safely at temporary storage facilities for up to three years, after which they will be transferred to a planned interim storage facility. The decontamination pilot project was carried out in both the restricted and planned evacuation areas in order to assess decontamination methods and demonstrate measures for radiation protection of workers. Temporary storage facilities of different technical specifications were designed and constructed under various topographic conditions and land-use. In order to support designing, constructing and monitoring of temporary storage facilities for decontamination wastes during the full-scale decontamination, technical know-how obtained during the decontamination pilot project has been identified and summarized in this paper.

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