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, Na, I
and HTO in granodiorite; Laboratory-scale results and their extrapolation to the in situ conditionTachi, Yukio; Ebina, Takanori*; Takeda, Chizuko*; Saito, Toshihiko*; Takahashi, Hiroaki*; Ouchi, Yuji*; Martin, A. J.*
Journal of Contaminant Hydrology, 179, p.10 - 24, 2015/08
Times Cited Count：29 Percentile：74.23(Environmental Sciences)Matrix diffusion and sorption are important processes in the assessment of radionuclide transport in crystalline rocks. Diffusion and sorption parameters for Cs, Na, I and HTO were determined by through-diffusion and batch sorption experiments using granodiorite samples from the Grimsel Test Site, Switzerland. The De values were in the order Cs, Na, HTO, I. The capacity factor and Kd values show the same trends. The dual depth profiles for Cs and Na can be interpreted by a near-surface Kd increment. The microscopic analysis indicated that this is caused by high porosity and sorption capacities in disturbed biotite minerals on the sample surface. The Kd values derived from the dual profiles are likely to correspond to Kd dependence on the grain sizes of crushed samples in the batch experiments. The results of the in situ LTD experiments were interpreted reasonably well by using transport parameters derived from laboratory data and extrapolating them to in situ conditions.
Muroi, Masayuki*
JNC TJ8400 2000-042, 142 Pages, 2000/02
JNC-TJ8400-2000-042.pdf:14.6MB
Hyperalkaline pore water of cementitious material used in TRU waste repository would react with bentonite and cause the increased porosity and the loss of the swelling and sorption ability. This work is a modelling study on bentonite-cement pore water. The possible extent of reaction between bentonite and cement pore water was simulated using the PRECIP reaction-transport code. Three cement pore fluid compositions (leachates 1,2 and 3) were reacted with a 1-D, 1m flowpath of bentonite (+ sand) at 25 and 70
C. Key minerals were allowed to dissolve and precipitate using kinetic reaction mechanism. Leachate 1 was the most aggressive fluid (highest pH, Na and K), and leachate 3 (1owest pH, Na and Ca) the least aggressive. Simulation with leachate 1 showed total removal of primary bentonite minerals up to 60 cm from the contact with cement after 
1000 years. The maximum porosity increase observed was in leachate 1(up to 80-90%) over a narrow zone 1-2 cm. Simulations with all fluids showed total filling of pore with CSH minerals in a zone very close to the interface with the cement, whereas zeolites and sheet silicates formed far away. For a given leachate composition, there was little difference in the profiles at the two temperatures studied. It was suggested that bentonite alteration was not sensitive to the kinetic parameters over the conditions studied. The conceptual model chosen for the modelling study assumed that there was an unlimited amount of cement pore fluid available for reaction with bentonite so that the results of the simulations represent a conservative (pessimistic) estimate. There were a number of uncertainties associated with the modelling which relate to assumptions concerning: the kinetic mechanisms for dissolution and growth of minerals at elevated pH; evolving surface areas of minerals with time; thermodynamic data for CSH minerals, zeolites and aqueous species at high pH; the synergy between changing porosity and fluid ...
Miki, Takahito*; Sasamoto, Hiroshi; Chiba, Tamotsu*; Inagaki, Manabu*; Yui, Mikazu
JNC TN8400 2000-007, 32 Pages, 2000/01
JNC-TN8400-2000-007.pdf:0.69MB
This report presents a summary of literature survey about geochemical reactions which are important to evaluate the redox conditions in the near field rock mass and buffer. The results of literature survey are summarized as follows; (1)Minerals including ferrous iron and organic materials in the rock mass are important reductants. Initial stage after closure of repository, oxygen will be consumed by pyrite, because the reaction rate between pyrite and oxygen is relatively fast. (2)It is possible to estimate the redox capacity for reductants by rock (mineral)-water iteraction experiment in a laboratory. And it is expected that the ferrous iron-rich rock and higher porosity rock may have bigger redox capacity. (3)It is possible to estimate the oxygen consumption rate by reductants such as minerals including ferrous iron. The rate law and rate constant for the oxidation reaction of ferrous iron in the solution are also determined. As a conclusion, it seems that we can evaluate kinetically the evolution of geochemical conditions in the near field rock mass and buffer by excavation of drifts, based on data derived from these existing literatures.
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.
; ; 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.
Takachi, Kazuhiko; Suzuki, Hideaki*
JNC TN8400 99-041, 76 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 unconfined compression tests, one-dimensional consolidation tests, consolidated-undrained triaxial compression tests and consolidated-undrained triaxial creep tests that aim at getting hold of static mechanical properties. We can get hold of the relationship between the dry density and tensile stress etc. by Brazillian tests, between the dry density and unconfined compressive strength etc. by unconfined compression tests, between the consolidation stress and void ratio etc. by one-dimensional consolidation tests, the stress pass of each effective confining pressure etc. by consolidated-undrained triaxial compression tests and the axial strain rate with time of each axial stress etc. by consolidated-undrained triaxial creep tests.
Sato, Haruo
JNC TN8400 99-065, 379 Pages, 1999/10
A database for diffusivity for a data setting of effective diffusion coefficients in rock matrices in the second progress report, was developed. In this database, 3 kinds of diffusion coefficients: effective diffusion coefficient (De), apparent diffusion coefficient (Da) and free water diffusion coefficient (Do) were treated. The database, based on literatures published between 1980 and 1998, was developed considering the following points. (1)Since Japanese geological environment is focused in the second progress report, data for diffusion are collected focused on Japanese major rocks. (2)Although 22 elements are considered to be important in performance assessment for geological disposal, all elements and aquatic tracers are treated in this database development considering general purpose. (3)Since limestone, which belongs to sedimentary rock, can become one of the natural resources and is inappropriate as a host rock, it is omitted in this database development. Rock was categorized into 4 kinds of rocks; acid crystalline rock, alkaline crystalline rock, scdimentaly rock (argillaceous/tuffaceous rock) and sedimentary rock (psammitic rock/sandy stone) from the viewpoint of geology and mass transport. In addition, rocks around neutrality among crystalline rock were categorized into the alkaline crystalline rock in this database. The database is composed of sub-databases for 4 kinds of rocks. Furthermore, the sub-databases for 4 kinds of the rocks are composed of databases to individual elements, in which totally, 24 items such as species, rock name, diffusion coefficients (De, Da, Do), obtained conditions (method, porewater, pH, Eh, temperature, atmosphere, etc.), etc. are input. As a result of literature survey, for De values for acid crystalline rock, totally, 207 data for 18 elements and one tracer (hydrocarbon) have been reported and all data were for granitic rocks such as granite, granodiorite and biotitic granite. For alkaline crystallinc rock, ...
Sato, Haruo
JNC TN8400 99-061, 9 Pages, 1999/10
The porosities and dry densities for rock samples sampled from a fractured zone (fracture type C: composed of intact ganodiorite, altered ganodiorite and fracture fillings) at the Kamaishi mine were obtained by a water saturation (intrusion) method as input parameters for nuclide migration analysis in performance assessment of the geological disposal of high-level radioactive waste. Consequently, the average porosity, 8.6
0.43% was higher than those of fracture fillings, altered garnodiorite and intact ganodiorite composing fracture type B with a single fracture taken from the Kamaishi mine so far. While, the average dry density, 2.430.0089 Mg
m
, was lower than those of rocks composing the fracture type B. Based on this, it is predicted that radionuclides are the easiest to migrate in the fracture zone.
Sato, Haruo
PNC TN8410 97-202, 205 Pages, 1998/01
This thesis summarizes the results investigated in order to establish a basic theory on the predictive method of diffusion coefficients of nuclides in compacted sodium bentonite which is a candidate buffer material and in representative rocks for the geological disposal of radioactive waste by measuring the pore structural factors of the compacted bentonite and rocks such as porosity and tortuosity, measuring diffusion coefficients of nuclides in the bentonite and rocks, acquiring basic data on diffusion and developing diffusion models which can quantitatively predict nuclide migration in long-term. This consists of 7 chapters. Chapter 1 is the introduction, in which conventional studies on nuclide migration in buffer materials and rocks for the geological disposal of radioactive waste carried out to date are reviewed, and those problems are summarized as well as the objectives of this study are described. Besides, the difinition of geological disposal is explained. In Chapter 2, it is described on non-steady state diffusion of HTO, Sr-90, Tc-99, I-129, Cs-137, Np-237, Am-241 and Pu in purified sodium bentonite, Kunipia-F, in which the rate of constituent Na-smectite was raised approximately 100wt%. In-diffusion experiments were carried out in a range of bentonite densities of 200 2000 kgm under ambient aerobic conditions at room temperature (20 23C), and apparent diffusion coefficients (Da) were obtained. The apparent diffusion coefficients decreased with increasing dry density of bentonite. It was quantitatively indicated from diffusion experiments using HTO that these Da values include the effect of geometric retardation such as the tortuosity factor of compacted bentonite. It was experimentally clarified that Da is not affected by diffusion time based on diffusion experiments for different experimental periods using Sr and Cs. Moreover, it was also experimentally clarified that Da is not affected by tracer ...
Iida, Yoshimasa
Donen Giho, (104), p.135 - 140, 1997/12
Uranium ore in the Athabasca region, Canada, is highly variable in density. This is due to large variations in the grade of high-density uranium and associated metalliferous minerals, and also to changes in porosity. As it is not practical to take accurate measurements of dry bulk density values of a large number of samples. As a result of investigation on actual ore samples, it has been found practical to estimate the dry bulk density of ore from measured wet bulk density and grain density calculated from chemical data.
; ;
PNC TN9410 98-014, 46 Pages, 1997/11
Thermal conductivity of uranium-plutonium mixed oxide fuel for fast reactor at beginning-of-life was correlated based on the recent results in order to apply to the fuel design and the fuel performance analysis. A number of experimental results of unirradiated fuel speimens were corrected from open literatures and PNC internal reports and examined for the database. Thermal conductivity of acutual fuel with porosity (
), that of fully dense fuel ( 100%TD) and porosity correction factor (F) had theoretically the following correlation : = F 100%TD. The following correlation was developed for fully dense fuel by the results of high density fuel pellets which the effect of porosity was relatively small. The data base ranged from 17 to 30% for plutonium content in heavy metal atoms, from 1.90 to 2.00 for oxygen to metal ratio, from 90 to 98% of theoretical density and from 400 to 2090 degree C for temperature. 
= (1/(-0.03237+0.8606
+2.483
10
T))+75.2710
T
where 100%TD: Thermal Conductivity (W/mK) T: Temperature (K) O/Z: Oxygen-to-metal ratio (-) In this work two porosity correction factors were needed for high density fuel and low density fuel (around the current Monju specification). For high density fuel (as-fabricated fuel density : 
90%TD) F
= 1-2.95P(P:Porosity volume Fraction (-)) For low density fuel (as-fabricated fuel density: around 85%TD) F
= 1-1.4P (P: Porosity volume Fraction (-)) The universal porosity correction factor was not determined in this work. In the next step, theoretical and analytical considerations should be taken into account.
Sato, Haruo; ; ; *; *; Yui, Mikazu
PNC TN8410 97-127, 57 Pages, 1997/08
Retardation of key nuclides is one of the most important mechanisms to be examined specifically and modelled for the performance assessment of geological disposal of radioactive waste. We have been studing diffusion of nuclides into the pore spaces of the rock matrix, sorption of nuclides on the rock pore surfaces and pore properties to quantify the degree of nuclide retardation in fractured crystalline rock. The work has concentrated on predominant water conducting fracture system in the host granodiorite in the Kamaishi In Situ Test Site, which consists of fracture fillings and altered granodiorite. Through-diffusion experiements to obtain effective and apparent diffusion coefficients (Da and De, respectively) for Na, Cs, HTO, Cl and Se as a function of ionic charge at 22 25C and batch sorption experiments for Cs, Sr, Se, 
U and 
Pu were conducted on fracture fillings, altered and intact granodiorite. The experiments only for Se, a redox sensitive element, were done in an N2-atmospheric glove box (O
1 ppm) to keep the chemical species. In situ groundwater (pH8.79.5) sampled from the same place as rock samples was used for the experiments. Porosity and density of cach rock sample were determined by both water saturation method and mercury porosimetry, and pore-size distribution and specific surface area of pores were measured by mercury porosimetry. The porosity is in the order; fracture fillings (5.6%) altered rock (3.2%) intact rock (2.3%). The pore-size distribution of the intact and altered granodiorite is ranging from 10 nm to 0.2 mm, and the fracture fillings have that of 50 nm to 0.2 mm, but a lot of pores were found around 100 nm and 0.2 mm in the fracture fillings. The effective diffusion coefficients for all species (Na, Cs, HTO, Cl, Se0
) are in the order of fracture fillings altered rock intact rock in proportion to these porosities. Effective diffusion ...
*; *; *; *
PNC TJ9601 96-003, 38 Pages, 1996/03
In this study, for the purpose of development of a nondestructive detection technique of creep-fatigue damage in Type 316FR stainless steel for fast reactors, application study of electrochemical methods and the Induced Current Potential Drop(ICFPD) was done. Applicability of electrochemical methods to evaluation of grain boundary precipitates which, provide preferred site for cavities was investigated. Anodic polarization curves were measured both in 1N KOH solution and in 1N HSO
+KSCN solution. An anodic current peak that, corresponds to preferential dissolution of the grain boundary precipitates was observed in the measurements using in the KOH solutlon. It was suggested that evolution of the grain boundary precipitates which should be associated with creep-fatigue damage can be evaluated by the electrochemical method using KOH solution. The results of reactivation ratio of the material in 1N HSO+KSCN solution, which is recognized as the sensitive indicator of Cr-depletion, suggested a correlation between the reactivation ratio and creep-fatigue damage. Clear differences between the as-received material and the creep-fatigue damaged sample were found in ICFPD results. Although more detailed investigation is required to make a conclusion, it was expected that potential drop can reflect creep-fatigue damage in the microstructure, e.g. precipitates cavities, surface cracks. Based on the preliminaly result, the ICFPD technique may be expected to provide a quantitative monitoring capability of creep-fatigue damage.
*; Kumata, Masahiro; ; *
Doboku Gakkai Dai-50-Kai Nenji Gakujutsu Koenkai Koen Gaiyoshu, 0, p.64 - 65, 1995/00
no abstracts in English
*; *; *
PNC TJ9614 94-001, 59 Pages, 1994/03
Crossflow of a two-phase mixture between vertical subchannels is subdivided into three components in the literature; turbulent mixing, void drift and diversion crossflow. Of these, turbulent mixing alone occurs in an equiliblium flow, in which flow rates of both phases in each subchannel do not change in the axial direction. In a general non-equilibrium flow, however, all three components occur simultaneously. In this report, effect of pressure differential between subchannels on flow redistribution process along the channel axis has been studied experimentally. In the experiment, a multiple channel, consisting of two identical circular subchannels of 16 mm I.D., were used as a test channel. And, air and water were introduced unevenly into the two subchannels at the inlet to get several non-equilibrium flows with and without the pressure differential between subchannels. For each flow, we have obtained the axial distributions data of pressure differential between the subchannels, the air and water flow rates, the void fractions, and the tracer concentrations for both phases when gas and liquid tracers were injected into one of the two subchannels. From these experimental data, we have estimated lateral velocities of the air and water corresponding to each crossflow component, and analyzed the effect of the pressure differential on the lateral velocities.
M.E.Kab*; Hayafune, Hiroki
PNC TN9410 92-018, 58 Pages, 1992/01
This report describes the result of the analysis of unprotected Loss of Flow (LOF) ansient experiment conducted at the PLANt Dynamics Test Loop (PLANDTL) experimentalfility by Super System Code (SSC) and SubAssembly Boiling EvolutioN Analysis (SABENA)ode. This report also describes the effect of the modification we made in SSC with t recent void fraction and two-phase friction multiplier models during the analysis othe experiment. After the analysis, it was found that the two-fluid two-phase flow mel of SABENA 1-D is better than the homogeneous model of SSC in predictiong the therhydraulic behavior within the simulated fuel bundle test section of thePLANDTL facily in case of high quality sodium boiling experiment. Moreover, it wasalso revealed tt the two-fluid one dimensional model is not accurate enough in predicting the onsetf boiling and axial evolution of boiling region inside the heatedchannel.
Taisei Corporation*; Shimizu Corporation*; Obayashi Corporation*; Kajima Corporation*
PNC TJ1449 91-005, 256 Pages, 1991/01
None
Otani, Nobuo*
PNC TN9410 90-083, 70 Pages, 1990/07
Core physics was studied on the High Temperature Fast Reactor (HTFR) whose prime objective is to produce hydrogen. Core of HTFR consits of nitride or oxide fuel, and thermal power of a commercial HTFR is assumed to be 300 to 400 MWt. The analysis in this report aims at the core design having negative or small positive void reactivity from view point to attain safety if the reactors, The method of decreasing sodium void reactivity coefficient was to increase neutron leakage through the large surface area of the core by adopting its shape of a pan cake (core height/core diameter=1/2 to 1/3). Result of the analysis revealed that, total void coefficients is negative for all cases analyzed with U fuel. However almost all the cases analyzed had positive void reactivity coefficients for MOX fuel. Burn-up calculation was peformed for U fuel core. Calculational results showed that the excess reactivity of about 5% was necessary to compensate reactivity decrease due to the burn-up during a year. The above calculations were performed using the CITATION code.
