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JNC TN1400 2000-007, 100 Pages, 2000/07
JNC-TN1400-2000-007.pdf:4.67MB
no abstracts in English
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JNC TY7430 2000-001, 57 Pages, 2000/03
JNC-TY7430-2000-001.pdf:2.17MB
no abstracts in English
Owada, Hitoshi*; Mihara, Morihiro; Iriya, Keishiro*; *
JNC TN8400 99-057, 43 Pages, 2000/03
Cementitious materials are considered as candidate materials for the geological disposal of high-level radioactive waste and TRU waste. As the pH and the Ca content of leachate from the cementitious materials are high, the host rock and the buffer-material would be degraded by the leachate in the long-term. Therefore, transport properties and parameters such as solubilities and distribution coefficients of radionuclides would be changed and affect the performance of the repository. In order to dissolve this "High pH plobrem", the use of a low alkalinity cement is considered for the disposal. In this study, we summarized the necessity of the low alkalinity cement, and developed the approach of the low alkalinization of cement. And, the following were carried out in this study : A leaching test of cement paste, a fluid test of the mortar and a installation test of the concrete to the trial structure. From the leaching test using the cement paste, we confirmed that we were able to obtain the low alkalinity cement (HFSC) by addition of pozzolanic materials such as silica-fume and flyash. From the result of the fluid test of the mortar, we chose the cement for the practicability evaluation. The practicability of low alkalinity concrete was evaluated by installation test to the trial structure.As a result of these examinations, we proved that the pH value of the leachate from the cementitious material was reduced by adding SF and FA to Portland cement. Simultaneously, SF and FA had to be added in order to obtain the good workability. In addition, workability and mechanical strength of the cement which SF and FA were added are almost equivalent to the ordinary Portland cement. The results shows that the HFSC has high practicability.
Sasamoto, Hiroshi; Yui, Mikazu; Randolph C Arthu*
JNC TN8400 99-074, 84 Pages, 1999/12
Hydrochemical investigation of Tertiary sedimentary rocks at JNC's Tono in-situ tests site indicate the groundwaters are: (1)meteoric in origin, (2)chemically reducing at depths greater than a few tens of meters in the sedimentary rock, (3)relatively old [carbon-14 ages of groundwaters collected from the lower part of the sedimentary sequence range from 13,000 to 15,000 years BP (before present)] (4)Ca-Na-HCO
type solutions near the surface, changing to Na-HCO type groundwaters with increasing depth. The chemical evolution of the groundwaters is modeled assuming local equilibrium for selected mineral-fluid reactions, taking into account the rainwater origin of these solutions. Results suggest it is possible to interpret approximately the "real" groundwater chemistry (i.e., pH, Eh, total dissolved concentrations of Si, Na, Ca, K, Al, carbonate and sulfate) if the following assumptions are adopted: (1)CO
concentration in the gas phase contacting pore solutions in the overlying soil zone = 10
bar, (2)minerals in the rock zone that control the solubility of respective elements in the groundwater include; chalcedony (Si), albite (Na), kaolinite (Al), calcite (Ca and carbonate), muscovite (K) and pyrite (Eh and sulfate). It is noted, however, that the available field data may not be sufficient to adequately constrain parameters in the groundwater evolution model. In particular, more detailed information characterizing certain site properties (e.g., the actual mineralogy of "plagioclase", "clay" and "zeolite") are needed to improve the model. Alternative conceptual models of key reactions may also be necessary. For this reason, a model that accounts for ion-exchange reactions among clay minerals, and which is based on the results of laboratory experiments, has also been evaluated in the present study. Further improvements of model considering ion-exchange reactions are needed in future, however.
Ijiri, Yuji; ; *; Watari, Shingo; K.E.Web*; *; *
JNC TN8400 99-092, 91 Pages, 1999/11
JNC has been developed the performance assessment approaches for both fractured rock and porous rock. An equivalent continuum model is incorporated for solving the radionuclide migration in porous rock, while a discrete fracture network model is incorporated for solving the radionuclide migration in fractured rock (see more detail in Sawada et al. [1999]). This report describes the methodology, the data and the results of the performance assessment of porous rock. From the results of radionuclide migration analyses that were based on the hydrogeological properties obtained from the Neogene sedimentaly rock at the Tono mine, it was found that the release rate of selenium-79 and cesium-135 are dominant in porous rock. The sensitivity analyses using one-dimensional porous model revealed that hydraulic conductivity has more influences on the results than porosity does. In addition, it was found that smaller distribution coefficients of sandstone yield higher release rate than mudstone and tuff, and smaller distribution coefficients of saline water conditions yield higher release rate than fresh water conditions. The radionuclide migration in Neogene sedimentaly rock, where flow in rock matrix as well as in fractures are significant, was evaluated by superposing the results of porous model and fracture model. Since fracture model tends to yield more conservative results than porous model, it is obvious that the performance of Neogene sedimentary rock can be conservatively assessed by fracture model alone. The nuclide migration analyses performed in this report were based on the hydrogeological properties obtained at the depth between 20 meters and 200 meters frrom the ground surface. Therefore, it should be noted that the release rate at the depth of a future repository in Neogene sedimentary rock, 500 m, will be smaller than that shown in this report due to peemeability decrease from 200 m to 500 m.
Ijiri, Yuji; ;
JNC TN8400 99-091, 69 Pages, 1999/11
It is crucial for the performance assessment of geosphere to evaluate the characteristics of fractures that can be dominant radionuclide migration pathways from a repository to biosphere. This report summarizes the charactelistics of fractures obtained from broad literature surveys and the fields surveys at the Kamaishi mine in northern Japan and at outcrops and galleries throughout the country. The characteristics of fractures described in this report are fracture orientation, fracture shape, fracture frequency, fracture distribution in space, transmissivity of fracture, fracture aperture, fracture fillings, alteration halo along fracture, flow-wetted surface area in fracture, and the correlation among these characteristics. Since granitic rock is considered the archetype fractured media, a large amount of fracture data is available in literature. In addition, granitic rock has been treated as a potential host rock in many overseas programs, and has JNC performed a number of field observations and experiments in granodiorite at the Kamaishi mine. Therefore, the characteristics of fractures in granitic rock are qualitatively and quantitatively clarified to some extent in this report, while the characteristics of fractures in another rock types are not clarified.
; ; Ishiguro, Katsuhiko; Nakajima, Kunihiko*;
JNC TN8400 99-087, 41 Pages, 1999/11
Corrosion of the carbon steel overpack leads to a volume expansion since the specific gravity of corrosion products is smaller than carbon steel. The buffer material is compressed due to the corrosive swelling, reducing its thickness and porosity. On the other hand, Buffer material may be extruded into fractures of the surrounding rock and this may lead to a deterioration of the planned functions of the buffer, including retardation of nuclides migration and colloid filtration. In this study, the sensitivity analyses for the effect of volume expansion and intrusion of the buffer material on nuclide migration in the engineering barrier system are carried out. The sensitivity analyses were performed on the decrease in the thickness of the buffer material in the radial direction caused by the corrosive swelling, and the change in the porosity and dry density of the buffer caused by both compaction due to corrosive swelling and intrusion of buffer material. As results, it was found the maximum release rates of relatively shorter half-life nuclides from the outside of the buffer material decreased for taking into account of a volume expansion due to overpack corrosion. On the other hand, the maximum release rates increased when the intrusion of buffer material was also taking into account. It was, however, the maximum release rates of longer half-life nuclides, such as Cs-137 and Np-237, were insensitive to the change of buffer material thickness, and porosity and dry density of buffer.
Ashida, Takashi; ; Sato, Haruo; ; Kitamura, Akira; Kawamura, Kazuhiro
JNC TN8400 99-083, 63 Pages, 1999/11
Studies on the chemical and migration behaviour of radionuclides were carried out in the Quantitative Assessment Radionuclide Migration Experimental Facility (QUALITY)for assuring the relaiability and for improving the propriety of data concerning nuclide migration used in the Second Progress Report for the geoloical disposal of high-level radioactive waste. Five studies for solubility, sorption and diffusion concerning nuclide migration were carried out. The overview of each study and the result is as follows: (1)Study on Effect of Carbonate on Np Solubility. Solubilities of Np(IV) were measured as functions of pH and carbonate concentration under reducing conditions. The obtained data could be well described by considering two hydroxo-carbonate complexes, and those stability constants were estimated and compared with the literature data. Consequently, the data obtained in this study were similar to the literature data. (2)Study on Effect of Carbonate on Np Sorption on Bentonite. Distribution coefficients (Kd) of Np(IV) on smectite were measured as a function of carbonate concentration. The obtained Kd values were approximately constant over the carbonate concentration (total carbon concentration 0.04-0.15M). The results of desorption tests by 1M KCl and HCl at the end of sorption experiments showed two different desorption behaviour; Np(IV) was well removed by HCl for the experiments in low carbonate concentration and by KCl for those in high carbonate concentration. (3)Distribution Coefficient Measurements for Cs, Pb and Cm on Rocks. Distribution Coefficients for Cs, Pb and Cm on Japanese major rocks (basalt, mudstone, sandstone, granodiorite and tuff) were measured as a function of ionic strength. The obtained Kd values were either the same orders or higher compared with data used to both fresh and saline groundwater systems in the Second Progress Report. This indicates that the Kd data used in the Second Progress Report are either proper or conservative. ...
Oda, Chie; Ikeda, Takao*; Shibata, Masahiro
JNC TN8400 99-073, 112 Pages, 1999/11
In the safety assessment for geological disposal of high-level radioactive wastes (HLW), distribution coefficients (Kd) and diffusion coefficients of radionuclides are used to estimate the migration of radionuclides in a near-field of repository. 
Sn is one of the important nuclides for the safety assessment in Japan and its behavior under reopsitory conditions has not been understood. This report provides the experimental informations for the sorption of Sn on bentonite, tuff and granodiorite, and the diffusion of Sn in a compacted bentonite. The Kd values of Sn on bentonite, tuff and granodiorite were determined by the batch-type sorption experiments as l0
10
[ml/g], 10
10
[ml/g] and 10 10[ml/g], respectively. The sequential extraction experiments for adsorbed Sn on bentonite were also performed to investigate its desorption behavior. These experimental results indicated that the mechanisms of sorprion onto bentonite were dominated by the sorption reactions on smectite and pyrite and consisted of reversible and irreversible sorption on solid and stable fixation in solid. On the other hands, the apparent diffusion coefficients (Da) in compacted bentonite were measured by the diffusion experiments as 10
[m
/sec] and l0
[m/sec] for dry densities of 0.4[g/cm] and 1.0[g/cm], respectively. Moreover, the Kd values in compacted bentonite were calculated according to the relationship with the measured Da values, and the solubilities in the porewaters of compacted bentonite were calculated by use of the calculated Kd and the obtained diffusion plofiles. It is found that the derived solubilities almost agreed with the solubiliies of amorphis SnO reported by Amaya et al. (1997), however, the derived Kd values were lower than that measured from the batch-type sorption experiments.
Yui, Mikazu; ; Shibata, Masahiro
JNC TN8400 99-070, 106 Pages, 1999/11
This report is a summary of status, frozen datasets, and future tasks of the JNC thermodynamic database (JNC-TDB) for assessing performance of high-level radioactive waste in geological environments. The JNC-TDB development was carried out after the first progress report on geological disposal research in Japan (H3). In the development, thermodynamic data (equilibrium constants at 25 
C, I=0) for important radioactive elements were selected/determined based on original experimental data using different models (e.g., SIT, Pitzer). As a result, the reliability and traceability of the data for most of the important elements were improved over those of the PNC-TDB used in H-3 report. For detailed information of data analysis and selections for each element, see the JNC technical reports listed in this document.
*; Nakazawa, Toshiyuki*; Ueta, Shinzo*; Shibata, Masahiro
JNC TN8400 99-069, 41 Pages, 1999/11
As a part of the evaluation for the sorption phenomena of nuclides in compacted bentonite, apparent diffusivities for uranium, neptunium and technetium that are redox-sensitive elements, were measured under reducing conditions. Bentonite used was a sodium bentonite, Kunigel V1. Apparent diffusivities were measured by using in-diffusion method (concentration profile method), under the conditions with varying dry densities of compacted bentonite and sorts of the solution used for water saturation of bentonite in diffusion experiments. As a result of the measurements, following ranges of values for apparent diffusivities were acquired. ...
Aoyagi, Takayoshi*; Mihara, Morihiro; Tanaka, M.*; Okutsu, Kazuo*
JNC TN8400 99-058, 55 Pages, 1999/11
For the emplaced waste in TRU waste disposal facility, it may have the void for waste bodies it. And, generating void which accompanies those component elution in concrete pit and filler in which the cement material becomes the candidate material is assumed. It is considered that the security of the diffusion control in the bentonite is not done when these voids collapsed, and when it generated the volume change inside the buffer material (bentonite). The imperfect blockage of the void by not obtaining, the sufficient swelling pameability swelling bentonite is a cause on this. Then, volume change of the bentonite inside is analyzed in this study under the conservative estimation. And the following are tested: Self-sealing, maximum swelling rate, density distribution change of the batonite. Evaluation of the engineered barrier system for volume change from the result was carried out. Prior to the evaluation, generating void was calculated based on the conservative estimation. The density of the buffer material as it assumed the blocking by buffer material uniformly awelling using this calculated data, was obtained. By the permeability got from existing research result which shows the relationship between density and permeability of the bentonite, it was confirmed to become diffusion control in the buffer material inside, in existing engineered barrier specification. Next, it was tested, when the conservative void of the superscription was assumed, in order to confirm whether it does the security, as permeability necessaly for maintaining diffusion control, puts it for the swelling of actual bentonite. As the result, it was possible to confirm sufficient swelling performance in order to do the security of the diffusion control in Na-bentonite. However, the swelling performance greatly lowered by comparing Na-bentonite in Ca-bentonite with under 1/6. The increase of the permeability not do the security of the diffusion control, when it was based on void quantity ...
Tanai, Kenji; Sato, Haruo; *; *
JNC TN8400 99-045, 108 Pages, 1999/11
In the anaerobic environment in the deep underground water, carbon-steel overpack corrodes and generates molecular hydrogen. It is conceivable that this hydrogen either dissolves into the porewater of the buffer and migrates through the buffer. If the rate of aqueous diffusion of hydlogen is too low compared to the rate of hydrogen generation, the concentration of hydrogen at the overpack surface will increase until a solubility limit is attained and a free hydrogen gas phase forms. It is possible that the pressure in this accumulating gas phase will increase, affecting the stability of the buffer or the surrounding rock mass. There is also a concern of possible effects on nuclide migration, as it is also conceivable that the flow of gas could push out radionuclide-bearing porewater in the buffer when it floes through the buffer. As such, experimental and analytical study must be carried out on such phenomenon to evaluate such potential phenomena. (1)Diffusion experiment of dissolved hydrogen. According to the test result concerning the effective diffusion coefficient of the dissolved hydrogen in buffer material, the effective diffusion coefficient of reference buffer material (70wt% bentonite + 30wt% sand mixture, dry density 1.6Mg m
) ranges from 10
m s to 10
ms. The value of the effective diffusion coefficient measured for a dry density of 1.8 Mg m is slightly smaller than the value in that for a dry density 1.6 Mg m. And the effective diffusion coefficient at 60C tends to have slightly larger value than that at 25C. Test results from the foreign countries show the diffusion coefficient in the range between 10
ms to 10
ms. Basically, these test results reported here are in the same range as these other results. (2)Gas permeability. Studies of the gas permeabinty of buffer material have been carried out by Pusch et al., Volckaert ...
Tanai, Kenji; Iwasa, Kengo; Hasegawa, Hiroshi; Goke, Mitsuo*; Horita, Masakuni*; Noda, Masaru*
JNC TN8400 99-044, 140 Pages, 1999/11
This report consists of three items: (1)Study of the repository configuration, (2)Study of the surface facilities configuration for construction, operation and buckfilling, (3)Planning schedule, In the repository configuration, the basic factors influencing the design of the repository configuration are presented, and the results of studies of various possible repository configurations are presented for both hard and soft rock systems. Here, the minimum conditions regarding geological environment required to guide design are assumed, because it is difficult to determine the repository configuration without considering specific conditions of a disposal site. In the surface facility configuration, it is illustrated based on the results of construction, operation, buckfilling studies for underground disposal facility and EIS report of CANADA. In the schedule, the overall schedule corresponding to the repository layout is outlined in link with the milestone of disposal schedule set forth in the government's basic policy. The assumptions and the basic conditions are summarized to examine the General Schedule from start of construction to closure of a repository. This summaly is based on the technologies to be used for construction, operation and closure of a repository. The basic national policies form the framework for this review of the general schedule.
Takachi, Kazuhiko; Taniguchi, Wataru
JNC TN8400 99-042, 68 Pages, 1999/11
The buffer material is expected to maintain its low water permeability, self-sealing properties, radionuclides adsorption and retardation properties, thermal conductivity, chemical buffering properties, overpack supporting properties, stress buffering properties, etc. over a long period of time. Natural clay is mentioned as a material that can relatively satisfy above. Among the kinds of natural clay, bentonite when compacted is superior because (1)it has exceptionally low water permeability and properties to control the movement of water in buffer, (2)it fills void spaces in the buffer and fractures in the host rock as it swells upon water uptake, (3)it has the ability to exchange cations and to adsorb cationic radioelements. In order to confirm these functions for the purpose of safety assessment, it is necessary to evaluate buffer properties through laboratory tests and engineering-scale tests, and to make assessments based on the ranges in the data obtained. This report describes the procedures, test conditions, results and examinations on the buffer material of dynamic triaxial tests, measurement of elastic wave velocity and liquefaction tests that aim at getting hold of dynamic mechanical properties. MWe can get hold of dependency on the shearing strain of the shearing modulus and hysteresis damping constant, the application for the mechanical model etc. by dynamic triaxial tests, the acceptability of maximum shearing modulus obtained from dynamic triaxial tests etc. by measurement of elastic wave velocity and dynamic strength caused by cyclic stress etc. by liquefaction tests.
Sugino, Hiroyuki; *
JNC TN8400 99-040, 75 Pages, 1999/11
The buffer material that will be buried as a component of the engineered barriers system swells when saturation by groundwater. As a result of this swelling, buffer material may penetrate into the peripheral rock zone surrounding the buffer through open fractures. If sustained for extremely in long-period of time, The buffer material extrusion could lead to reduction of buffer density, which may in turn degrade the assumed performance assessment properties (e.g., permeability, diffusion coefficient) JNC has been conducted the study of bentonite extrusion into fractures of rock mass as a part of high level waste research. In 1997, JNC has reported the test results concerning buffer material extrusion and buffer material erosion. These tests have been done using test facilities in Geological Isolation Basic Research Facility. After 1997, JNC also conducted analytical study of buffer material extrusion. This report describes the analysis results of this study which are reflected to the H12 report. In this analysis, The diffusion coefficient was derived as a function of the swelling pressure and the viscosity resistance of the buffer materials. Thus, the reduction in density of buffer materials after emplacement in saturated rock was assessed. The assessment was made assuming parallel-plate radial fractures initially filled by water only. Because fractures in natural rock masses inevitably have mineral inclusions inside of them and fractures orientation leads to fractures intersecting other fractures, this analysis gives significantly conservative conditions with respect to long-term extrusion of buffer and possible decrease in buffer density.
Sugita, Yutaka; Fujita, Tomoo; Tanai, Kenji; Hasegawa, Hiroshi; Furuichi, Mitsuaki*; Okutsu, Kazuo*; Miura, K.*
JNC TN8400 99-039, 58 Pages, 1999/11
Regarding disposal techniques of high-level radioactive waste (HLW), the HLW is vitrified and then stored for cooling for a period of 30 to 50 years. After cooling, the HLW is isolated in the deep underground. The concept of geological disposal is based on the requirement to enclose the HLW in the deep underground for the long-term durability of the human's environmental safety. Backfilling of a repository is a unique activity on the geological disposal. If underground tunnels excavated to construct the repository are left, they may have significant influences on the barrier performance of an entire repository, such as: the mechanical stability of a tunnel may be damaged by rock stresses and a tunnel may provide a fast pathway for ground water flow. Therefore, the underground facilities are expected to be backfilled with a backfilling material after emplacement of the HLW and a buffer material. The material for the backfilling of the underground facilities is backfilling material. In this report, bentonite-aggregate mixture is considered, as one of the candidate materials for the backfilling material. Aggregate imitates the muck that is generated during construction phase of the underground facilities. The combination of backfilling, plugging and grouting is considered in some underground situations. Plug is composed of concrete material or clay-based one. Grouting material is concrete material or clay-based one, too. In this report, the concept of the backfilling, mechanical and hydrological characteristics of the bentonite-aggregate mixture, the function, work methods and a schedule of the backfilling materials, plugging and grouting are considered, and items of quality control for the bentonite-aggregate mixture, concrete material and grouting are listed.
Tomari, Haruo*; *; Shimogori, Kazutoshi*; Wada, Ryutaro*; ; Taniguchi, Naoki
JNC TN8400 99-076, 100 Pages, 1999/10
Effects of bentonite clay, applied potential, pH, of solution and cathodic polarization time on hydrogen absorption into titanium, which is one of the candidate materials of overpack for high-level radioactive waste container, have been investigated in artificial underground water. Considering the result at various test time and assuming the hydrogen absorption is ruled by the paraboric law, the amount of hydrogen after 1000 years exposure calculated to about 17ppm, which will be absorbed at the applied potential of -0.51 vs. SHE corresponds to equilibrium potential of hydrogen. It seems the assumption of the parabolic law and the test period are proper, because the linear relations were obtained between the amount of absorbed hydrogen and the logarithm of the averaged cathodic current and between the slopes of the lines and a square root of the test time. Titanium seems to have a life over 1000 years in deep underground repository according to assumption that about 500ppm absorbed hydrogen is critical for hydrogen embrittlement of titanium.