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
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.
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.
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.
Nakata, Hisakazu; Sakai, Akihiro; Amazawa, Hiroya; Sakamoto, Yoshiaki
Nihon Genshiryoku Gakkai-Shi ATOMO, 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.
Tsuji, Tomoyuki; Hoshino, Yuzuru; Sakai, Akihiro; Sakamoto, Yoshiaki; Suzuki, Yasuo*; Machida, Hiroshi*
JAEA-Technology 2017-010, 75 Pages, 2017/06
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).
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.
Sugaya, Toshikatsu; Nakatani, Takayoshi; Sasaki, Toshihisa*; Nakamura, Yasuo*; Sakai, Akihiro; Sakamoto, Yoshiaki
JAEA-Technology 2016-036, 126 Pages, 2017/02
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.
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.
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.
Dohi, Terumi; Omura, Yoshihito*; Kashiwadani, Hiroyuki*; Fujiwara, Kenso; Sakamoto, Yoshiaki; Iijima, Kazuki
Journal of Environmental Radioactivity, 146, p.125 - 133, 2015/08
Radiocaesium activity concentrations (Cs, 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 Cs ranged from 4.6 to 1000 kBq kg and for Cs ranged from 7.6 to 1740 kBq kg. A significant positive correlation was found between the Cs activity concentration in lichens and the Cs deposition density on soil, based on the calculated Spearman's rank correlation coefficients as = 0.90 ( 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 ( 0.01) and 0.90 ( 0.01) respectively. Therefore, they are suggested as biomonitoring species for levels of radiocaesium fallout within the Fukushima Prefecture.
Hoshino, Yuzuru; Sakamoto, Yoshiaki; Muroi, Masayuki*; Mukai, Satoru*
JAEA-Technology 2015-015, 96 Pages, 2015/07
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.
Dohi, Terumi; Omura, Yoshihito*; Kashiwadani, Hiroyuki*; Fujiwara, Kenso; Sakamoto, Yoshiaki; Iijima, Kazuki
Raiken, 18(1), p.11 - 13, 2014/12
no abstracts in English
Kurosawa, Ryohei; Sakai, Akihiro; Nakata, Hisakazu; Amazawa, Hiroya; Sakamoto, Yoshiaki
JAEA-Technology 2014-013, 89 Pages, 2014/06
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.
Sakai, Akihiro; Kurosawa, Ryohei; Hara, Hironori*; Nakata, Hisakazu; Amazawa, Hiroya; Arikawa, Masanobu*; Sakamoto, Yoshiaki
JAEA-Technology 2013-039, 228 Pages, 2014/02
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.
Nakata, Hisakazu; Amazawa, Hiroya; Sakai, Akihiro; Kurosawa, Ryohei; Kanno, Naohiro*; Kashima, Takahiro*; Sakamoto, Yoshiaki
JAEA-Technology 2013-036, 47 Pages, 2014/02
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.
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.
Amazawa, Hiroya; Sakai, Akihiro; Nakata, Hisakazu; Hara, Hironori; Kurosawa, Ryohei; Yamamoto, Masayuki*; Kawata, Yosuke*; Sakamoto, Yoshiaki
JAEA-Technology 2012-031, 338 Pages, 2012/10
JAEA is responsible for siting a proper location to establish new disposal facilities with siting criterion and procedure, in consideration of transparency and impartial for the siting process, based on Plan Concerning the Disposal Business Execution. As a part of the study to draw up siting criterion and procedure, Sensitivity analysis of the disposal facilities from the viewpoint of dose evaluation and cost estimation under various siting condition will be carried out. Therefore, Conceptual design of disposal facilities as a reference case is necessary. The basic condition of the design conforms to the property, quantity, radioactivity of waste packages, technical standards and likely siting condition. This report summarizes the results of the reasonable design of our disposal facilities and the layout of the place of activity where the disposal facilities and associated facilities to be installed.
Hara, Hironori; Amazawa, Hiroya; Sakai, Akihiro; Nakata, Hisakazu; Sakamoto, Yoshiaki
JAEA-Technology 2012-014, 49 Pages, 2012/06
Low level radioactive waste which is included high concentrated nitrate are planned to be disposed into concrete pit facility. From the point of view of environmental effect by easily soluble nitrate ion into groundwater, the safety assessment will be needed for the concrete pit type disposal facilities. In this study, the nitrate ion concentration in groundwater, lake and stream nearby the concrete pit type disposal facilities was simulated by advective-diffusion analysis. From the results of analysis, the limitation of amount of nitrate in the waste package was estimated from the environmental standard determined by Basic Environment Law.
Nakata, Hisakazu; Amazawa, Hiroya; Sakai, Akihiro; Yamamoto, Masayuki*; Sakamoto, Yoshiaki
JAEA-Technology 2011-036, 195 Pages, 2012/03
The waste package, which Japan Atomic Energy Agency plans to dispose, must be satisfied the technical standard specified by Law for the Regulations of Nuclear Source Material, Nuclear Fuel Material and Reactors. One of the technical standards is that it must have enough strength to withstand the load when the waste package is disposed finally by a burial method. Japan Atomic Energy Agency is required to prove the compliance of the waste package with the technical standard. Accordingly we conducted the actual load test of waste containers and imitated waste package in order to evaluate the anti-load strength of them by collecting strain and displacement data. The test was carried out by the compression apparatus which can imitate the supposed loading condition in a concrete pit type disposal facility. Based on the loading test result, we evaluate that 200 liter drum (M-class) has a minimum strength of 18 kN and 1 m cubic container has a maximum strength of 400 kN.
Nakata, Hisakazu; Amazawa, Hiroya; Sakai, Akihiro; Arikawa, Masanobu; Sakamoto, Yoshiaki
JAEA-Technology 2011-023, 54 Pages, 2011/08
JAEA will settle on near surface disposal facilities with and without engineered barriers for radioactive wastes. Both of them are so called concrete pit type and trench type, respectively. Technical standards of constructing a disposal facility based on Law for the Regulations of Nuclear Source Material, Nuclear Fuel Material and Reactors have been regulated partly by referring to that of Waste Management and Public Cleansing Law. This means that the concrete pit type and the trench type facility resemble an isolated type and a non leachate controlled type final disposal site, respectively. On the other, we plan to design a disposal facility with a liner system corresponding to a leachate controlled type final disposal site. By current nuclear related regulations, There are no technical standards of constructing the disposal facility with the liner system. So we investigate the function of the liner system in order to design a proper liner system for the trench type disposal facility.