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Murakami, Hiroaki; Nishiyama, Nariaki; Takeuchi, Ryuji; Iwatsuki, Teruki
Oyo Chishitsu, 64(2), p.60 - 69, 2023/06
In order to confirm the quality control items for borehole closure in radioactive waste disposal projects, in-situ borehole sealing tests using bentonite material were conducted. As a result, the closure performance was successfully demonstrated by comparing the data of water injection tests conducted before and after the installation of the closure material. However, the breakthrough was observed after closing, probably due to high differential pressure applied to the seal section. Thus, it is important to ascertain throughout the entire operation that the borehole is adequately closed. The placement and specifications of the closure material should be determined according to the hydrogeological structure in the borehole. The confirmation items to use bentonite for sealing material are identified to be: to consider swelling and density loss in the borehole; to place the planned depth using appropriate emplacement technique; to be placed without damage to seals when use some backfilling materials, considering effect of permeability on adjacent seals.
Saito, Tatsuo
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.
Abe, Takeyasu; Iida, Yoshihisa
Journal of Advanced Concrete Technology, 20(3), p.236 - 253, 2022/03
Times Cited Count:2 Percentile:10.87(Construction & Building Technology)This paper is a state-of-the-art report on the performance assessment of cementitious and related materials as components of engineered barrier systems for radioactive waste management. In this paper, (1) the concept of safety functions is reviewed as the engineering background of discussion, (2) an overview of the postclosure performance assessment for Belgian low- and intermediate-level short-lived radioactive waste disposal is provided, and (3) a modeling methodology for engineered barrier systems is analyzed using the concept of "mandala for durability mechanics". According to these works, authors present technical suggestions for technical stakeholders of Japanese low-level radioactive waste disposal.
Takahashi, Tomoyuki*; Uchida, Shigeo*; Takeda, Seiji; Nakai, Kunihiro*
KURNS-EKR-11, p.97 - 102, 2021/03
This paper outlines the status of IAEA database compilation for migration parameters depending elements in a biosphere such as soil-to-plant transfer factor and bioconcentration factor of marine products, and the status of utilization of the database in dose evaluation of radioactive waste disposal in Japan. Additionally, in the case of applying a new database to the dose evaluation for future radioactive waste disposal in a specific area. We summarized the opinions of specialists and result of general discussion about future strategies to make a new database for their parameters, perspectives to be considered in it, issues, etc.
Ota, Masakazu; Tanaka, Taku*
Journal of Environmental Radioactivity, 201, p.5 - 18, 2019/05
Times Cited Count:4 Percentile:16.20(Environmental Sciences)CH
released from deep underground radioactive waste disposal facilities can be a belowground source of
CO
owing to microbial oxidation of
CH
to
CO
in soils. Environmental
C models assume that the transfer of
CO
from soil to plant occurs via foliar uptake of
CO
. Nevertheless, the importance of
CO
root uptake is not well understood. In the present study, belowground transport and oxidation of
CH
were modeled and incorporated into an existing land surface
CO
model (SOLVEG-II) to assess the importance of root uptake on
CO
transfer to plants. Performance of the model in calculating the belowground dynamics of
CH
was validated by simulating a field experiment of
CH
injection into subsoil. The model was then applied to
C transfer in a hypothetical ecosystem impacted by continuous
CH
input from the water table (bottom of one-meter thick soil). In a shallowly rooted ecosystem with rooting depth of 11 cm, foliar uptake of
CO
was significant, accounting for 80% of the
C accumulation in the leaves. In a deeply rooted ecosystem (rooting depth of 97 cm), where the root penetrated to depths close to the water-table, more than half (63%) the
C accumulated in the leaves was transferred by the root uptake. We found that
CO
root uptake in this ecosystem depended on the distribution of methane oxidation in the soil; all
C accumulated in the leaves was transferred by the root uptake when methane oxidation occurred at considerable depths (e-folding depths of 20 cm, or 80 cm). These results indicate that
CO
root uptake contributes significantly to
CO
transfer to plants if
CH
oxidation occurs at great depths and roots penetrate deeply into the soil.
Nishihara, Kenji
ImPACT Fujita Puroguramu Kokai Seika Hokokukai "Kaku Henkan Niyoru Koreberu Hoshasei Haikibutsu No Ohaba Na Teigen, Shigenka" Seika Hokokusho, Shiryoshu, p.28 - 31, 2019/03
In this project, long-lived fission products (LLFP) contained in conventional high-level radioactive wastes are separated and their life is reduced, and elements that can be used as resources are separated. By shortening the life of LLFP, it has been shown that it may be possible to dispose in intermediate depth of several tens of meters, meeting safety requirements, instead of geological disposal. In addition, for reassuring recycling of usable elements, possible exposure pathways were evaluated to estimate the safe concentration level of radioactivity.
Nishihara, Kenji
ImPACT Fujita Puroguramu Kokai Seika Hokokukai "Kaku Henkan Niyoru Koreberu Hoshasei Haikibutsu No Ohaba Na Teigen, Shigenka" Seika Hokokusho, Shiryoshu, p.130 - 133, 2019/03
High level radioactive waste contains elements with various characteristics. It is possible to reduce the load on the disposal site by separating them according to those characteristics and appropriately dealing with them. In this project, we are working to shorten the life span of long-lived fission products (LLFP). When this technology is realized, high-level radioactive wastes will become new radioactive wastes with low radioactivity. As a result of investigation of disposal concept of new radioactive waste, it turned out that intermediate-depth disposal currently considered for low level radioactive waste may be suitable. Intermediate-depth disposal is a method of small-scale disposal in shallow locations as compared to geological disposal for conventional high-level radioactive waste. We conducted a safety assessment when this disposal is applied to new radioactive wastes, and found that it is possible to safely dispose of for the four LLFPs addressed by this project.
Amamoto, Ippei
Journal of the Society of Inorganic Materials, Japan, 24(391), p.393 - 401, 2017/11
Glass is a non-crystalline solid, as such, it is relatively easy to change its composition to control its characteristics. The borosilicate glass, which is produced by the addition of boron oxide into sodium-lime glass, possesses excellent heat-resistant properties and mechanical strength. It has a wide variety of uses. The borosilicate glass is applied as the vitrified medium for radioactive wastes to immobilize and stabilize them for long term. The glass form which is loaded with high-level radioactive waste is called the vitrified waste. This paper classified the radioactive waste and describes treatment and production methods of vitrified waste, its characteristics, disposal method and also introduces alternative vitrified medium.
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).
Kitamura, Akira; Kirishima, Akira*
Journal of Nuclear Science and Technology, 52(3), p.448 - 450, 2015/03
Times Cited Count:3 Percentile:95.87(Nuclear Science & Technology)The Journal of Nuclear Science and Technology covers a variety of subjects in the field of nuclear waste management, which includes radioactive waste treatment, radioactive waste disposal and environment, decommissioning and dismantling. This summary introduces activities presented in recent years.
Tanaka, Tadao; Sakamoto, Yoshifumi; Yamaguchi, Tetsuji; Takazawa, Mayumi; Akai, Masanobu; Negishi, Kumi; Iida, Yoshihisa; Nakayama, Shinichi
JAERI-Conf 2005-007, p.105 - 110, 2005/08
Highly alkaline environments induced by cementitious materials in radioactive waste repositories are likely to dissolve and to alter montmorillonite, the main constituent of bentonite buffer materials. For the prediction of the long-term variations in permeability of compacted sand-bentonite mixtures, long-term alteration of bentonite should be quantified based on information accumulated by using the compacted or powdered bentonite materials, with batch experiments or column experiments. In this study, we summarize distinctive information obtained from various experimental systems, and propose functional and effective integration of experimental approaches to prediction of bentonite alteration.
Akai, Masanobu; Ito, Nobuyuki*; Yamaguchi, Tetsuji; Tanaka, Tadao; Iida, Yoshihisa; Nakayama, Shinichi; Inagaki, Shingo*
JAERI-Tech 2004-058, 47 Pages, 2004/09
Geochemistry Research Equipment for TRU Waste Elements has been installed in Back-end Cycle Key Elements Research Facility (BECKY) of Nuclear Fuel Cycle Safety Engineering Research Facility (NUCEF). This equipment is designed to study geochemical behavior of TRU elements and other radionuclides contained in TRU waste (TRU waste elements) and to acquire data for safety assessments of radioactive wastes disposal. The equipment consists of anaerobic glove box systems, aerobic glove box systems equipped with built-in barrier performance testing apparatus, and analytical instruments. This report describes principles, structure, performance and safety designs of each component of the equipment, and results of research performed in the equipment.
Bamba, Tsunetaka
Genshiryoku Bakkuendo Kenkyu, 8(2), p.205 - 206, 2002/03
no abstracts in English
; Mihara, Morihiro;
JNC TN8430 2001-007, 56 Pages, 2002/01
In the geological disposal concept of radioactive wastes, a kind of clay with sorption ability and low permeability, called bentonite, is envisaged as an engineered barrier system in the geological repository. Also, the cemetitious material is envisaged as the backfill material in the vaults and the structure material of the vaults. The groundwater in contact with the cementitious material will promote hyperalkaline conditions in the repository environment and these conditions will affect the performance of the bentonite. Therefore, it is necessary to investigate the interaction between the cementitious material and the bentonite for the evaluation of long term stability of the disposal system. In this study, for the identification and the investigation of the secondary minerals, the batch immersion experiments of the powder bentonite were carried out using synthetic cement leachates (pH=7, 12.5, 14) at 200C. As the results, it was confirmed that Na as exchangeable cations in the bentonite can exchange relatively easily with Ca in the solution from the experiment results. And the ratio of cation exchange was estimated to be about 25% based on the amount of exchangeable cations Ca
between layers. Furthermore, it was concretely shown that the generation of analcime might be affected by the Na concentration from results of the solution analyses and a stability analysis of analcime using the chemical equilibrium model, in addition to the pH in the solution.
Sakai, Akihiro; Yoshimori, Michiro; Okoshi, Minoru; Yamamoto, Tadatoshi; Abe, Masayoshi
JAERI-Tech 2001-018, 88 Pages, 2001/03
no abstracts in English
Sakai, Akihiro
KURRI-KR-56, p.58 - 79, 2001/03
no abstracts in English
Maeda, Toshikatsu; Sakamoto, Yoshiaki; Nakayama, Shinichi; Yamaguchi, Tetsuji; Ogawa, Hiromichi
JAERI-Review 2001-001, 25 Pages, 2001/02
no abstracts in English
Sakai, Akihiro; Yoshimori, Michiro; Abe, Masayoshi
JAERI-Tech 2000-012, p.107 - 0, 2000/03
no abstracts in English
Tanaka, Satoru*
JNC TJ8400 2000-003, 62 Pages, 2000/02
For the safety assessment of radioactive waste disposal, it is important to elucidate the effect of colloids on radionuclide migration, which are released with dissolution of cementitious materials composing engineered barricr. In the previous work, we identified and characterized the colloidal particles in the solutions contacting cement hydrates, OPC and low-alkaline cement paste, and observed the release of the colloid particle. In the present work, we performed same experiments as the last year to confirm the reproducibility of the colloid release. We studied the leaching behavior of the colloid when OPC and low-alkaline cement past contact water flow. Furthermore, the effect of an alumina particle was studied, which is used as a barrier material for colloid migration. The following conclusions were derived: (1)In the solution contacting cement paste, the small amount of particles, which are considered as CaCO or silicate colloids were observed. Thus, the reproducibility of the last work was confirmed. (2)The leaching of colloid in the solution was confirmed by water flow through the cement paste. The concentration of particle was as low as 10
10
mL
. (3)Al
0
powder, with the diameter of 200
150
m, was found to be effective to some extent as a barrier for a colloid migration from low-alkaline cement paste.
Takeda, Seiji
JAERI-Research 99-047, 71 Pages, 1999/08
no abstracts in English