Ishii, Kenji; Fujita, Masaki*; Sasaki, Takanori*; Minola, M.*; Dellea, G.*; Mazzoli, C.*; Kummer, K.*; Ghiringhelli, G.*; Braicovich, L.*; Toyama, Takami*; et al.
Nature Communications (Internet), 5, p.3714_1 - 3714_8, 2014/04
Oda, Chie; Honda, Akira; Takase, Hiroyasu*; Ozone, Kenji*; Sasaki, Ryoichi*; Yamaguchi, Kohei*; Sato, Tsutomu*
Nendo Kagaku, 51(2), p.34 - 49, 2013/02
Proposed TRU repository designs for geological disposal envisage the use of a bentonite buffer to limit the migration of radionuclides by impeding groundwater flow. Under highly alkaline conditions due to cementitious materials could cause a complex series of coupled changes in the porewater chemistry, mineralogy and, ultimately, the mass transport properties of the bentonite buffer. To elucidate the consequences of these coupled changes, reactive-transport model analyses have been conducted for eight bentonite alteration test cases using different combinations of secondary minerals that could form in the bentonite buffer. It was found that after 100,000 years the amount of dissolved bentonite was at a maximum when metastable secondary minerals precipitated. It was also found that the diffusion and hydraulic coefficients after 100,000 years in all test cases were on the same order of magnitude as the initial values.
Nakatani, Takayoshi; Ishitoya, Kimihide; Funabashi, Hideyuki; Sasaki, Ryoichi*; Kurosawa, Mitsuru*
JAEA-Research 2010-050, 104 Pages, 2011/02
In July 2007, the Nuclear Safety Commission of Japan (NSC) formulated "Basic Policy for Safety Regulation Concerning Land Disposal of Low-Level Radioactive Waste (Interim Report)". "Classification of Scenarios into Three Types" and their "Standard Dose Values" were indicated in this report. In this study, some scenarios for safety assessment were developed as "Inadvertent Human Intrusion or Rare Natural Event Scenarios" based on the previous technical documents. The parameters were set up for dose calculation and the exposure doses were calculated. As the result, exposure doses in all cases were less than 10 mSv/y100 mSv/y (standard exposure dose of "Inadvertent Human Intrusion or Rare Natural Event Scenarios").
Sasaki, Satoru; Suto, Toshiyuki; Harada, Akio; Kurihara, Ryoichi; Yamamoto, Kazuyoshi; Tsuchida, Noboru; Shimizu, Isamu; Nomura, Toshibumi
Genshiryoku eye, 57(1), p.66 - 75, 2011/01
no abstracts in English
Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05
Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.
Sugaya, Toshikatsu; Sone, Tomoyuki; Nakatani, Takayoshi; Ishitoya, Kimihide; Funabashi, Hideyuki; Sasaki, Ryoichi*; Shimoda, Satoko*; Kurosawa, Mitsuru*
JAEA-Research 2009-063, 80 Pages, 2010/03
The purpose of this study was to assess exposure dose of "Likely Scenarios" and "Less-likely Scenarios" on sub-surface disposal. They were two of "Classification of three types scenarios" in "Basic Policy for Safety Regulation Concerning Land Disposal of Low-Level Radioactive Waste (Interim Report)" formulated by the Nuclear Safety Commission of Japan. Selection of the assessed scenarios, development of the assessment tool and preliminary exposure dose assessment were conducted. Maximum exposure doses for "Likely Scenarios" and "Less-likely Scenarios" were less than each standard dose value in the Interim Report (Likely Scenarios: 10Sv/y, Less-likely Scenarios: 300Sv/y).
Nakatani, Takayoshi; Ishitoya, Kimihide; Funabashi, Hideyuki; Sasaki, Ryoichi*; Kurosawa, Mitsuru*
JAEA-Research 2009-028, 47 Pages, 2009/10
This study was carried out the evaluation of exposure dose on "Less-likely Scenarios" according to "Basic Policy for Safety Regulation Concerning Land Disposal of Low-Level Radioactive Waste (Interim Report)" (In July 2007, the Nuclear Safety Commission of Japan). When the evaluation modeling was constructed, "Evaluation scenario" and "Fluctuating parameter" were simplified "Physical, chemical change of the disposal system according to the climatic variation and the tectonic movement" that was the event foreseen happening in the future to "Release coefficient from the disposal facilities of the nuclide", "Distribution coefficient of the natural barrier", "Velocity of the underground water", and "Distance of the transfer path". As the result, exposure doses in all cases for "Less-likely scenarios" were less than 300 Sv/y (standard exposure dose of "Less-likely Scenarios").
Masuda, Kenta; Oda, Chie; Nakanishi, Hiroshi*; Sasaki, Ryoichi*; Takase, Toshio*; Akagi, Yosuke*; Fujita, Hideki*; Negishi, Kumi*; Honda, Akira
JAEA-Research 2008-104, 194 Pages, 2009/03
Saline groundwater contains high concentrations of chloride ions, which possibly elevate the pH of cement pore water by reacting with hydrogarnet and producing Friedel's salt. Calcium aluminate hydrates and portlandite, which can be found in hydrated ordinary Portland cement (OPC), were immersed in a sodium chloride solution, which had concentrations similar to those found in seawater.
Ishitoya, Kimihide; Nakatani, Takayoshi; Funabashi, Hideyuki; Sasaki, Ryoichi*; Takase, Toshio*; Kurosawa, Mitsuru*
JAEA-Research 2008-092, 64 Pages, 2008/12
In this study, some scenarios for safety assessments were developed. According to each developed scenario, the parameters were set up for dose calculation. Calculated results were analyzed and summarized from the viewpoints of effects of radionuclide migration parameters such as release coefficient, distribution coefficient, ground water velocity and migration distance. Dose more than 10 Sv/y was calculated in some cases. Increase of ground water velocity or decrease of distribution coefficient caused by sea water inflow into migration path influenced slightly on the dose excess. In case of rapid change of the parameters, severe influences on the dose excess were observed. But, it wasn't thought that this rapid change would happen actually. On the other hand, in case of linear assumption of parameter change from 10,000 y to 100,000 y, dose less than 10 Sv/y was calculated.
Sakanaka, Shogo*; Ago, Tomonori*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; Harada, Kentaro*; Hiramatsu, Shigenori*; Honda, Toru*; et al.
Proceedings of 11th European Particle Accelerator Conference (EPAC '08) (CD-ROM), p.205 - 207, 2008/06
Future synchrotron light sources based on the energy-recovery linacs (ERLs) are expected to be capable of producing super-brilliant and/or ultra-short pulses of synchrotron radiation. Our Japanese collaboration team is making efforts for realizing an ERL-based hard X-ray source. We report recent progress in our R&D efforts.
Kamei, Gento; Honda, Akira; Mihara, Morihiro; Oda, Chie; Murakami, Hiroshi; Masuda, Kenta; Yamaguchi, Kohei; Nakanishi, Hiroshi*; Sasaki, Ryoichi*; Ichige, Satoru*; et al.
JAEA-Research 2007-067, 130 Pages, 2007/09
After the publication of the 2nd progress report of geological disposal of TRU waste in Japan, policy and general scheme of future study for the waste disposal in Japan was published by ANRE and JAEA. This annual report summarized aim and progress of individual problem, which was assigned into JAEA in the published policy and general scheme. The problems are as follows; characteristics of TRU waste and its geologic disposal, treatment and waste production, quality control and inspection methodology for waste, mechanical analysis of near-field, data acquisition and preparation on radionuclides migration, cementitious material transition, bentonite and rock alteration in alkaline solution, nitrate effect, performance assessment of the disposal system and decomposition of nitrate as an alternative technology.
Mihara, Morihiro; Sasaki, Ryoichi
JNC TN8400 2005-027, 49 Pages, 2005/09
In Japan, some of low-level radioactive wastes (LLW) containing nuclides with long half-lives, such as transuranium (TRU) nuclides, fission products (e.g. iodine- 129) and activation products (e.g. carbon-14), will be generated by the operation and decommissioning of domestic and overseas reprocessing plants for spent nuclear fuel and a domestic MOX fuel fabrication plant. Such wastes are termed "TRU waste". The high activity wastes of them are panned to dispose under deep under-ground in future. The Federation of Electric Power Companies(FEPC) and the Japan Nuclear Cycle Development Institute (JNC) have been caring out the performance assessment (PA) for TRU waste disposal system. In this report, radio-nuclides migration datasets (RAMDA) of cement, bentonite and rocks for the PA are described. RAMDA contains the following dataset: (1)Radio-nuclides solubility (2)Effective diffusion coefficient of radio-nuclide (3)Sorption of radio-nuclide. For the establishment of RAMDA, the long-term evolution of the engineered barriers, such as cement mortar and compacted bentonite, was considered.
Shibata, Masahiro; Mihara, Morihiro; Sasaki, Ryoichi; Honda, Akira
JNC TN8400 2005-025, 17 Pages, 2005/09
In the performance assessment for the geological disposal of the TRU waste, effect of organic material (i.e. organic wastes, cement additives, and natural organism) should be considered. The waste solvent (including TBP and its deterioration products) is contained in the asphalt waste generated from the reprocessing facility of JNC. These solvent and deterioration products have the possibility of forming the complexes with actinide elements if a chemical condition is satisfactory. It influences solubility and the sorption behavior of the radionuclide when the complexes are soluble in aqueous solution. In that case, there is a possibility to influence the behavior of the radionuclide migration. In this report, to evaluate the influence of TBP and its deterioration products (DBP and MBP) on the solubility and the sorption behavior of the actinide, (1) literature survey for the experimental research, (2) survey for the thermodynamics data concerning the interaction with the radionuclide and calculation for solubility and speciation in the expected environments, were conducted. As a result, it was thought that the influences of TBP and its degradation products on the solubility and speciation of radionuclides were small (Times of several in solubility at most).
Sasaki, Ryoichi; Oda, Chie; Honda, Akira
JNC TN8400 2005-024, 42 Pages, 2005/09
Radioactive waste which includes TRU nuclide (TRU waste) possesses wide radionuclide concentration distribution. Some kinds of TRU wastes (hulls-endpieces, asphalt solidification package, spent ioine adsorber etc.) should be disposed in the geological repository because of relatively high radioactivity. Most waste package will be filled with cementitious material. It is considered that waste packages will be isolated to the concrete pit constructed in a drift and filled space with cementitious material filler. I-129 and C-14 cannot be expected solubility limits and storong adsorption to the cementitious material, therefore, the bentonite-sand mixture which possesses very low permeability will be employed as a component of multi-barrier system which installs. The function of engineered barrier system(EBS) which consists of waste package, cementitious filler and buffer material are required to be maintained for a long term. Hence, it is important to analyze the EBS alteration based on available knowledge coming from both experiments and natural analogue. EBS alteration analyses were inplemented with the simplified diffusion transport system which consisted of cement region and bentonite buffer using PHREEQC code (the ver.2.10). In the analysis, variation of secondary mineral assemblage is considered. It is known that the dissolution rate of montmorillonite decreaes as its saturation index increase, so instantaneous dissolution equilibrium and the empirical equation for the dependency of dissolution kinetics on S.I. which was proposed by Cama et al. (2000) were assurned. In most cases, calculation results showed that the funcion of EBS will be maintained over ten southand years. In some cases (instantaneous equilibrium case, modified logK case, SRHP case), significant montmorillonite dissolution was shown. But, such results are inconsistent with the natural analogue knowledge which shows natural bentonite exists for 2 million years under seawater similar ...
Oda, Chie; Sasaki, Ryoichi; Honda, Akira; Savage, D.*; Arthur, R. C,*
JNC TN8400 2005-020, 39 Pages, 2005/09
The multiple scenarios of bentonite alteration were ideveloped based on the possible mineralogical changes derived from knowledge of both experiments and observation of natural systems. It was focused that the mineral reaction involving hyperalkaline fluid thermodynamically depends on the variable chemical condition in bentonite buffer and that kinetics is important as well as thermodynamic stability in controlling their occurrence, i.e., the kinetic controls operate to remain metastable minerals over the long term. The mineralogical consequences of the interaction between clays and alkaline fluid are summarized as follows. / -Clay and gel illite / -Clay and gel metastable zeolite stable zeolite and feldspar / -Clay and gel stable zeolite and feldspar The typical minerals for each category (illite group, metastable zeolite group and stable zeolite and feldspar group) were selected. The scenarios give the range of potential secondary minerals occurring in chemical schemes of the bentonite alteration by cement pore fluids, and thus reasonable assumptions on the simulation of the chemical and mineralogical evolutions of geological disposal system for TRU waste.
Oda, Chie; Sasaki, Ryoichi; Takase, Hiroyasu*; Savage, D.*; Honda, Akira
Proceedings of International Workshop on Waste Management in Sapporo, p.163 - 165, 2005/08
The uncertainty in our understanding of the precise mineral paragenetic sequences of the interaction of bentonite with hyperalkaline fluids in the long-term still remains. In order to reflect this uncertainty, multiple scenarios of bentonite alteration were investigated based on the possible mineralogical changes derived from knowledge of both experiments and observation of natural systems.
Honda, Akira; Toshiyasu, Suguro,; Sasaki, Ryoichi
JNC TN8400 2004-029, 43 Pages, 2005/03
Radioactive Iodine in the spent nuclear fuel is trapped by Iodine-adsorber in the off-gas process of reprocessing plant. The radioactive iodine includes very long half-lived nuclide (I-129;Half life=1.57x10y).The I-129 cannot be expected to decay due to containment by the barrier system because of its long half life. The Iodine have soluble and poorly sorbing nature in the geological disposal condition, because the element can take the chemical form of Iin the reducing condition such as the condition of deep underground. Therefore Iodine can migrate in barrier system easily and strongly contribute to the peak of dose in the performance assessment of TRU waste disposal. An effective measure for reducing the dose peak is the controlled release of Iodine from the waste package in the low flux. The solidification by the copper matrix was proposed as one of the previous controlled release technology by JNC. The release rate of I-129 from the waste package solidified by the copper matrix was estimated. The corrosion rate of copper matrix was estimated as the sum of those both in the oxdizing and reducing conditions. The rates and periods of I-129 release were estimated under the assumption of congruent release of I-129 with corrosion of the copper matrix. The total release rate and period in the FRHP groundwater case were 3.11X10Bq yand 1.64x10y(Initiated at 10y and finalized at 1.64x10y) respectively. The total release rate and period in the SRHP groundwater case were 9.03x10Bq yand 5.66x10y(Initiated at 10y and finalized at 5.76x10y).
Kurosawa, Susumi; Sasaki, Ryoichi; Ueta, Shinzo*; Yoshikawa, Hideki
JNC TN8400 2004-012, 68 Pages, 2004/07
In order to evaluate the impact of microorganism by COLFRAC, which simulates colloid-facilitated contaminant migration, the microorganism - radionuclide sorption data and microbial films data in deep geological environment were surveyed. After the survey, the data conversion to be able to calculate the effect of them on performance assessment in COLFRAC has been undertaken. As the results of calculation by COLFRAC, the transport behavior of radionuclide may be enhanced, when radionuclide will be taken in the microorganism. Furthermore, the results indicated that the transport rate of radionuclide depends on microbial concentration.
Oda, Chie; Honda, Akira; Sasaki, Ryoichi; Savage, D.*
Extended Abstractof International Workshop on Bentonite-Cement Interaction in Repository Environments, 7 Pages, 2004/04
The possible multiple scenarios of chemical-mineralogical evolution in Bentonite buffer were considered on the basis of the information of both experimental results and observations of natural systems. The range of variable chemical conditions according to each scenario was examined in terms of the potential for locally-attained chemical equilibrium and kinetics. These analyses have been intended to provide reasonable assumptions on simulations using chemistry-transport-hydrology coupling models that aims at estimating the possible evolution of hydraulic condition of bentonite in a TRU waste repository.
Tsujimoto, Keiichi*; Shinohara, Yoshinori*; Saito, Shigeyuki*; Ueta, Shinzo*; Ohashi, Toyo*; Sasaki, Ryoichi*; Shingo, Tomiyama*
JNC TJ8400 2003-040, 78 Pages, 2003/02
The safety performance assessment was carried out in imaginary geological environment in the conventional research and development of geological disposal, but the importance of safety assessment based on the repository design and considering the concrete geological environment will increase in the future. The research considering the link of the major three fields of geological disposal, investigation of geological environment, repository design and safety performance assessment, is the contemporary worldwide research theme. Hence it is important to organize information flow that contains the series if information process from the data production to analysis in the three fields, and to systemize the knowledge base that unifies the information flow hierarchically.The information flow for geological environment model generation process is examined and modified base on the product of the research of "Study on the development of geological environment model" that of the research in 2002. The work flow diagram for geological structure and hydrology are modified, and those for geochemical and rock property are examined from the search. Furthermore, database design was examined to build geochemical environment database (knowledgebase) based on the result of the systemization of the environment model generation technology. The geochemical environment database was designed and the prototype system is build to contribute database design.