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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.
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.
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.
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.
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.
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
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
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
Daimaru, Shuji; Takeuchi, Ryuji; Takeda, Masaki; Ishibashi, Masayuki
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.149 - 158, 2010/10
no abstracts in English
Saito, Hiroshi; Taki, Tomihiro
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.533 - 537, 2010/10
Ningyo-toge Environmental Engineering Center, Japan Atomic Energy Agency (JAEA) has maintained and preserved the Ningyo-toge and Togo Mines under the related laws, including the Mine Safety Law. JAEA has been planning to close these mines to prevent mine-pollution and reduce radiological impact to as low as achievably possible, for lasting protection of individuals and the environment. Among the mine-related facilities that are subject to environmental remediation, the Mill Tilings Pond is given the top priority. So far, basic concept has been discussed in parallel with data acquisition and designing for some of remediation activities.
Yokota, Hideharu; Yamamoto, Yoichi; Maekawa, Keisuke; Hara, Minoru*
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.81 - 86, 2010/10
It is important for assessing the safety of geological disposal of high-level radioactive waste to understand groundwater flow as the driving force of mass transport. In the groundwater-flow simulation, hydraulic boundary conditions are required, including groundwater recharge rates. However, infiltration of water from the surface is difficult to clarify in detail because water near the surface is sensitive to external influence such as climatic variations. In the Horonobe area of northern Hokkaido, the Japan Atomic Energy Agency has been carrying out various hydrological observations to estimate the recharge rate. In the Horonobe area, subsurface temperature and soil moisture content have been observed at HGW-1 site and Hokushin Meteorological Station. These results have revealed the groundwater infiltration and recharge occurring throughout year, the shallow groundwater-infiltration velocity depending on the depth, and the position of Zero Flux Plane. In the future, it is necessary to quantitatively assess the shallow groundwater infiltration and recharge rate, the intermediate runoff, and the evapotranspiration based on the observed data of the weighing lysimeter, the tensiometer, and so on.
Sato, Haruo
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.175 - 184, 2010/10
The self-sealing function of the clearances between buffer material and overpack and tunnel wall or disposal pit wall and between backfill material and tunnel wall is expected for bentonite which will be used as buffer material and part of the backfill material. The sealing properties of Na-bentonite have been studied for distilled water and saline water conditions, for example, it is reported that Na-bentonite seals clearance even under saline water conditions in a range of effective bentonite densities, higher than 1.3 kg/dm, for a bentonite dry density of 1.8 kg/dm and a clearance ratio of 10 % in experiments for Kunigel-V1. Although such information is useful for judging whether clearance is sealed, the filling properties of bentonite strongly depend on groundwater condition, silica sand content, montmorillonite content in the bentonite and the bentonite dry density, even though at the same effective bentonite density. In the present study, the author constructed an analytical model on the clearance filling performance for the design of buffer material and backfill material, based on the swelling properties of Na-montmorillonite which is the clay mineral constitute of Na-bentonite.
Kawamura, Makoto*; Tanikawa, Shinichi; Niizato, Tadafumi; Yasue, Kenichi
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.331 - 338, 2010/10
In order to assess the long-term safety of a geological disposal system for high-level radioactive waste (HLW), it is important to consider the impact of uplift and erosion, which cannot be precluded on a timescale in the order of several hundred thousand years for many locations in Japan. Geomorphic evolution, caused by uplift and erosion and coupled to climatic and sea-level changes, will impact the geological disposal system due to resulting spatial and temporal changes in the disposal environment. Degradation of HLW barrier performance will be particularly significant when the remnant repository structures near, and are eventually exposed at, the ground surface. In previous studies, fluvial erosion was identified as the key concern in most settings in Japan. Here, therefore, we present a methodology for development of a generic conceptual model for performance assessment based on best current understanding of fluvial erosion in Japan. Critical considerations that have to be taken into account when interpreting the geological record of past river-valley evolutions, as preserved in ancient fluvial deposits. Interpretation of the impact of such phenomena at relevant locations in Japan has led to development of a generic conceptual model which contains the features typical at middle reach of rivers. This paper presents the methodology to develop the conceptual model, which identifies the simplifications and uncertainties involved and assesses their consequences in the context of repository performance.
Permana, S.; Suzuki, Mitsutoshi
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.515 - 520, 2010/10
Fast reactor technology becomes more important player to enhance the optimum fuel utilization as well as for minimizing spent fuel waste such as trans-uranium by adopting closed fuel cycle option. The embodied challenges for introducing closed fuel cycle are proliferation resistance (PR) aspect of nuclear fuel as well as utilizing advanced fuel reprocessing and fabrication facilities. High level of PR for future nuclear fuel cycles have to be considered which can be obtained from isotopic material barriers such as uranium isotopic barrier, neptunium, and plutonium and so on.
Nakayama, Shinichi; Watanabe, Yoshio*; Kato, Masami*
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.279 - 285, 2010/10
The Nuclear and Industrial Safety Agency of the Ministry of Economy, Trade and Industry (NISA) has renewed its regulatory role and its need for regulatory support research on radioactive waste management, with recent circumstances of radioactive waste management in Japan being taken into consideration. In response, a technical supporting organization, the Japan Nuclear Energy Safety Organization (JNES), in 2009 released the five-year research plan "Regulatory Support Research Plan on Radioactive Waste Management 2010-2014", in cooperation with the research institutes of the Japan Atomic Energy Agency (JAEA) and the National Institute of Advanced Industrial Science and Technology (AIST). In October 2007, all three parties signed an agreement of cooperative study on geological disposal, which facilitated joint studies and exchanges of staff, data, and results. One of the ongoing joint studies has focused on regional-scale hydrogeological modeling using JAEA's Horonobe Underground Research Laboratory.
Asai, Shiho; Hanzawa, Yukiko; Okumura, Keisuke; Suzuki, Hideya; Toshimitsu, Masaaki; Shinohara, Nobuo; Kaneko, Satoru*; Suzuki, Kensuke*
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.261 - 264, 2010/10
