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Hanamuro, Takahiro; Yasue, Kenichi; Kokubu, Yoko; Asamori, Koichi; Ishimaru, Tsuneari; Umeda, Koji
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.25 - 30, 2011/01
Japanese islands are located in a tectonically active zone, where earthquakes and volcanic eruptions frequently occur. Therefore the understanding of the long-term stability of geological environment is important when assessing the long-term behaviour of the geological disposal system of high level radioactive waste (HLW) in Japan. The Japan Atomic Energy Agency (JAEA) is promoting the establishment of investigation and assessment methods of the long-term stability of geological environment necessary for site selection and safety assessment of HLW geological disposal.
Nakayama, Masashi; Sato, Haruo; Sugita, Yutaka; Ito, Seiji*; Minamide, Masashi*; Kitagawa, Yoshito*
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.51 - 56, 2011/01
In Japan, any high level radioactive waste repository is to be constructed at over 300 m depth below surface. Tunnel support is used for safety during the construction and operation, and shotcrete and concrete lining are used as the tunnel support. Concrete is a composite material comprised of aggregate, cement and various additives. Low alkaline cement has been developed for the long term stability of the barrier systems whose performance could be negatively affected by highly alkaline conditions arising due to cement used in a repository. Japan Atomic Energy Agency (JAEA) has developed a low alkaline cement, named as HFSC (Highly fly-ash contained silicafume cement), containing over 60wt% of silica-fume (SF) and fly-ash (FA). HFSC was used experimentally as the shotcrete material in construction of part of the 140 m deep gallery in Horonobe URL. The objective of this experiment was to assess the performance of HFSC shotcrete in terms of mechanics, workability, durability, and so on. HFSC used in this experiment is composed of 40wt% OPC (Ordinary Portland Cement), 20wt% SF, and 40wt% FA. This composition was determined based on mechanical testing of various mixes of the above components. Because of the low OPC content, the strength of HFSC tends to be lower than that of OPC in normal concrete. The total length of tunnel using HFSC shotcrete is about 73 m and about 500 m
of HFSC was used. The workability of HFSC shotcrete was confirmed in this experimental construction.
with DTAB and F-pentanol for decontamination of radioactive wastesKurahashi, Kensuke; Tomioka, Osamu; Meguro, Yoshihiro
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.217 - 220, 2011/01
To develop a metal separation method using supercritical CO (scCO) solvent for the decontamination process of radioactive wastes, the reverse micelle formation in scCO was investigated. Dodecyltrimethylammonium bromide (DTAB) as a surfactant to form the reverse micelles and 2,2,3,3,4,4,5,5-octafluoro-1-pentanol (F-pentanol) as a modifier to increase the solubility of DTAB into scCO were used. The reverse micelles could be formed by using 0.02 mol/dm DTAB and 0.45 mol/dm F-pentanol. A water concentration dissolved in scCO was increased with an increase of pressure, and 0.42 mol/dm water, which was 3 times larger than that in the neat CO, could be dissolved in scCO at 38 MPa. Moreover, 0.1 mol/dm HNO
could dissolve at the same pressure as water. On the other hand, it was found that the solubility of water at outside of reverse micelles increased with F-pentanol. The ratio of water and F-pentanol affected the phase behavior of water in scCO.
Takeda, Seiji; Kimura, Hideo
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.131 - 140, 2011/01
Clearance levels for the solid materials contaminated with uranium were estimated based on deterministic dose calculation approach for metal reuse scenario. The activity concentrations for major radionuclides, U-234, U-235 and U-238, were calculated to be 1.5 Bq/g, 1.4 Bq/g and 1.8 Bq/g, respectively. In order to confirm the validity of the calculated concentrations, the authors estimated the uncertainties on scenario description after metal recycling and on parameter values used in the deterministic calculation. The validity of the calculated activity concentrations by the deterministic approach was confirmed from the results of both the analysis for an additional scenario on the landfill disposal of residue of slag after metal recycling and the Monte Carlo-based analysis for parameter uncertainties.
Kitamura, Akira; Doi, Reisuke; Yoshida, Yasushi*
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010), Vol.2, p.365 - 373, 2011/00
We evaluated and estimated solubility of the 25 elements in the simulated pore waters established in the second progress report (H12) for safety assessment of geological disposal of HLW in Japan using the updated thermodynamic database (JAEA-TDB) and compared with the solubility values using the previous thermodynamic database (JNC-TDB). Furthermore, we tried to establish a technique to determine the solubility limiting solid for all target elements. It was found that most of the evaluated and estimated solubility values were not changed drastically, but the solubility values and dominant aqueous species for some elements were changed using the JAEA-TDB, e.g., due to introducing the formation constant of polynuclear hydrolysis species of zirconium and replacing the formation constant of mixed carbonatohydoxo complexes of thorium. Detail of the comparison and discussion about the evaluated and estimated solubility values between the JAEA- and the JNC- TDBs will be presented.
-ray emission from the progeny radionuclidesTanaka, Tadao; Shimada, Taro; Ito, Takeshi*; Sukegawa, Takenori
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.551 - 557, 2010/10
-ray from the progeny radionuclides of U-238, such as Th-234, Pa-234m and Ra-226, has been utilized for the evaluation of uranium concentration. In the present study, we proposed an evaluation method for U-238 concentration of background level in environment and for probate of vast land areas, in which the -ray radiations from Th-234, Pa-234m, Ra-226 is measured with the portable Ge detector. The U-238 concentration estimated by the in-situ metrology with portable Ge detector was in the order of 0.01 Bq/g in radioactive concentration, and was in comparable level with the concentrations decided by the ICP-MS established as high sensitive uranium analytical method. The method may be available for the U-238 concentration determination in vast land areas for the site release after decommissioning nuclear fuel handling facilities.
Sasao, Eiji
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.57 - 64, 2010/10
Long-term stability of the geological environment is one of the important keys for geological disposal of high-level radioactive waste in the Japanese Islands due to their location in a tectonically active island-arc. Uranium occurrences in Japan have been subjected to many geological processes inherent to the island-arc setting. Mode of occurrence of the uranium mineralization can be instructive as these could provide useful information on the long-term stability of the geological environment. Uranium mineralization is mainly in Tertiary sedimentary rocks and granitic rocks and less commonly in Cretaceous and Paleo/Mesozoic sedimentary sequences or metamorphic rocks. A variety of rocks host the Japanese uranium mineralization suggesting that geological environments suitable for geological isolation are widely distributed in the Japanese Islands, despite their location in a geologically active area. This effort will support building confidence in deep geological disposal.
Ota, Kunio; Amano, Kenji; Niizato, Tadafumi; Alexander, W. R.*; Yamanaka, Yoshiaki*
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.123 - 132, 2010/10
The assurance of the long-term stability of the geological environment is 
for deep geological disposal. In Japan, since uplift/subsidence and climatic and sea-level changes would result in a significant change to hydraulic and hydrochemical conditions at coastal sites, it is of importance to establish comprehensive techniques for characterising the overall evolution of coastal sites over geological time. To this end, palaeohydrogeological study is ongoing in the coastal area around Horonobe in northern Hokkaido. A "Geosynthesis Data Flow Diagram" defining a methodology for characterising the palaeohydrogeological evolution of the site has been formulated and, based on the geosynthesis methodology, a basic strategy has been established for stepwise investigations from initial survey of existing information to the final borehole programme at any coastal site. This technique has now been tested and optimised with the progress of the investigations.
Zaima, Naoki; Morimoto, Yasuyuki; Sugitsue, Noritake; Kado, Kazumi
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.311 - 320, 2010/10
Kanayama, Fumihiko
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.415 - 422, 2010/10
With the development of researches and investigations for atomic energy in Japan, various nuclear institutes have been built since 1960s. Today, large numbers of nuclear institutes became old and should be dismantled near future. Necessities for dismantling technology for atomic institutes became large. To dismantle atomic institutes, many cost and time are required. By choosing appropriate method, the cost and time for dismantling can be decreased. To choose appropriate method, it is important to collect the dismantling data of each kind of method, and understand advantages and disadvantages of each dismantling method accurately. To plan the nuclear facility which can be dismantled easily, and to promote setting up and dismantling efficiently, it is important to understand advantages and disadvantages of each dismantling method accurately, too. In JAEA, JPDR was dismantled to get experience of dismantling method of nuclear reactor. But, JAEA did not have experience of fuel cycle facility. Dismantling cost of fuel cycle facilities are more than that of nuclear facilities due to the contamination by TRU nuclide in fuel cycle facilities, In this report, to find appropriate method for dismantling fuel cycle facility, we dismantled liquid waste storage tank and wall-penetrating pipings in JRTF, which was one of the reprocessing facilities in JAEA. Number of man-days and occupational dose required were estimated to reveal advantages and disadvantages of two dismantling methods in each component. Moreover, appropriate conditions to select these dismantling methods are introduced.
Amamoto, Ippei; Mitamura, Naoki*; Tsuzuki, Tatsuya*; Takasaki, Yasushi*; Shibayama, Atsushi*; Yano, Tetsuji*; Nakada, Masami; Okamoto, Yoshihiro
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.503 - 508, 2010/10
The main objective of this development is to recycle the purified eutectic medium of the pyroreprocessing, delaying its disposal for as long as possible. We have introduced the simple filtration method to remove the rare earth element (REE) particles which were formed due to the conversion of REE chlorides to phosphates. Here, the iron phosphate glass is used as a filtration medium for the removal of FP particles. However, some soluble FP such as compounds of alkali-metals, alkaline-earth metals, etc. still remain in the eutectic medium. This time around, on an experimental basis, the iron phosphate glass has been used as a sorbent instead, to remove the soluble FP. We have obtained some positive results and have intention to incorporate it into the spent electrolyte recycle process as a part of the FP separation and immobilization system.
Kamei, Gento; Alexander, W. R.*; Clark, I. D.*; Degnan, P.*; Elie, M.*; Khoury, H.*; Milodowski, A. E.*; Pitty, A. F.*; Salameh, E.*; Smellie, J. A. T.*
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.141 - 147, 2010/10
Sanada, Hiroyuki; Nakamura, Takahiro; Sugita, Yutaka
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.31 - 39, 2010/10
As part of the research and development program on the HLW geological disposal, JAEA has been implementing the Horonobe Underground Research Laboratory (URL) project investigating sedimentary rock formations distributed in Horonobe area, Hokkaido, Japan. The authors have been implementing the research and development program at Horonobe to clarify the in situ stress conditions in siliceous mudstones at the URL. The objective of this work is to establish a strategy for an in situ stress measurement program for geological disposal and to develop an understanding of the in situ stress conditions in the deep underground formed by the sedimentary rocks. The application of several stress measurement methods to the Horonobe siliceous mudstones carried out during the surface-based investigations and the investigations during construction of the underground facilities, as well as information on the initial stress state around the Horonobe URL are described in this paper.
Iyatomi, Yosuke; Hoshina, Hiroyuki; Seko, Noriaki; Kasai, Noboru; Ueki, Yuji; Tamada, Masao
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.485 - 490, 2010/10
Yamamoto, Yuhei; Aosai, Daisuke; Mizuno, Takashi
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.203 - 212, 2010/10
Aosai, Daisuke; Yamamoto, Yuhei; Mizuno, Takashi
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.213 - 220, 2010/10
Size distribution of elements in groundwater is one of the most important information for understanding behavior of elements in deep underground environment. Size distribution is controlled mainly by groundwater physico-chemical parameters. Because the alteration of their physico-chemical states in groundwater cause changes of size distribution, systematic methodologies of ultrafiltration maintaining in-situ pressurized and anaerobic conditions is required. In this study, instrument for ultrafiltration maintaining in-situ pressurized/anaerobic conditions was developed and size distribution analysis was also conducted. The instrument developed in this study for consisted of passivated SUS materials is designed as to keep inner groundwater sample under a pressurized/anaerobic condition. Ultrafiltration was conducted at a borehole drilled from sub-stage at a depth of 200 m at the Mizunami Underground Research Laboratory site. The results obtained here indicate that ultrafiltration method is available for collection of filtered groundwater and passivation is an essential treatment before ultrafiltration.
Kunimaru, Takanori; Ota, Kunio; Amano, Kenji; Alexander, W. R.*
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.159 - 168, 2010/10
Saegusa, Hiromitsu; Takeuchi, Shinji; Maekawa, Keisuke; Osawa, Hideaki; Semba, Takeshi
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.133 - 140, 2010/10
Mizuno, Takashi; Milodowski, A. E.*; Iwatsuki, Teruki
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.193 - 201, 2010/10
Matsuoka, Toshiyuki; Amano, Kenji; Osawa, Hideaki; Semba, Takeshi
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.169 - 173, 2010/10
It is important for site characterization project to manage decision-making process during site characterization project with transparency and traceability, and to accumulate and hand technical know-how on to the next generation. Evaluation of the impact of uncertainties in the geological environment model is important to identify and prioritize key issues for further investigations. The aim of the study is to support for the planning of initial surface-based site characterization based on the technical know-how accumulating from Mizunami Underground Research Laboratory Project and Horonobe Underground Research Laboratory project. In this study, the task-flow of the geological modeling, which is one of the geological environment models, and the related technical know-how using literature data have been summarized.
