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JAEA Reports

Excavation and preparation rock block sample for LABROCK

Uchida, Masahiro; Yoshino, Naoto

JNC TN8410 2001-015, 35 Pages, 2001/05

JNC-TN8410-2001-015.pdf:1.73MB

This technical report summarizes excavation and preparation of the natural rock block sample used in LABROCK. This report was originally compiled by PNC in March, 1993.

JAEA Reports

Evaluation of Coupled Thermo-Hydro-Mechanical Phenomena in the Near Field for Geological Disposal of High-Level Radioactive waste

Chijimatsu, Masakazu*; Fujita, Tomoo; Sugita, Yutaka; Taniguchi, Wataru

JNC TN8400 2000-008, 339 Pages, 2000/01

JNC-TN8400-2000-008.pdf:30.96MB

Geological disposal of high-level radioactive waste (HLW) in Japan is based on a multibarrier system composed of engineered and natural barriers. The engineered barriers are composed of vitrified waste confined within a canister, overpack and buffer material. Highly compacted bentonite clay is considered one of the most promising candidate buffer material mainly because of its low hydraulic conductivity and high adsorption capacity of radionuclides. In a repository for HLW, complex thermal, hydraulic and mechanical (T-H-M) phenomena will take place, involving the interactive processes between radioactive decay heat from the vitrified waste, infiltration of ground water and stress generation due to the earth pressure, the thermal loading and the swelling pressure of the buffer material. In order to evaluate the performance of the buffer material, the coupled T-H-M behaviors within the compacted bentonite have to be modelled. Before establishing a fully coupled T-H-M model, the mechanism of each single Phenomenon or partially coupled phenomena should be identified. Furthermore, in order to evaluate the coupled T-H-M phenomena, the analysis model was developed physically and numerically and the adequacy and the applicability was tested though the engineered scale laboratory test and in-situ test. In this report, the investigative results for the development of coupled T-H-M model were described. This report consists of eight chapters. In Chapter l, the necessity of coupled T-H-M model in the geological disposal project of the high-level radioactive waste was described. In Chapter 2, the laboratory test results of the rock sample and the buffer material for the coupled T-H-M analysis were shown. The rock samples were obtained from the in-situ experimental site at Kamaishi mine. As the buffer material, bentonite clay (Kunigel V1 and Kunigel OT-9607) and bentonite-sand mixture were used. In Chapter 3, in-situ tests to obtain the rock property were shown. As ...

JAEA Reports

Data collection by literature survey on rock physical properties in Japan (II)

Sato, Toshinori; Taniguchi, Wataru; Fujita, Tomoo; Hasegawa, Hiroshi

JNC TN7400 99-011, 36 Pages, 1999/12

JNC-TN7400-99-011.pdf:1.55MB

In order to understand the general thermal and mechanical properties of rock masses and initial stress of rock at depth, data were compiled from the published literature in Japan and collected from investigations carried out at Kamaishi mine and Tono mine. Statistical examinations derived the ranges, means and medians of the mechanical properties for the different rock types. It was confirmed that the correlations between the mechanical properties were in agreement with correlations determined previously in other similar surveys. The unconfined compressive strength of Neogene sedimentary rocks showed a tendency to increase with increasing depth ( 500 m). An examination of the measured initial stress data collected through literature surveys showed that the vertical stress can be approximated by the extent of gravitational loading at a particular point. There is an approximately linear relationship between the average stress in a horizontal plane and the depth. The lateral pressure coefficient tends to have a high value and large range at shallow depths, but tends towards 1 with increasing depth.

JAEA Reports

Porosity and Density of Fractured Zone at the Kamaishi Mine

Sato, Haruo

JNC TN8400 99-061, 9 Pages, 1999/10

JNC-TN8400-99-061.pdf:1.43MB

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, 8.60.43% 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 Mgm $^{-3}$ , 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.

JAEA Reports

Coupled Thermo-Hydro-Mechanical Experiment at Kamaishi Mine Technical Note 15-99-02, Experimental results

Chijimatsu, Masakazu*; Sugita, Yutaka; Fujita, Tomoo; Amemiya, Kiyoshi*

JNC TN8400 99-034, 177 Pages, 1999/07

JNC-TN8400-99-034.pdf:19.38MB

It is an important part of the near field perfformance assessment of nuclear waste disposal to evaluate coupled thermo-hydro-mechanical (T-H-M) phenomena, e.g., thermal effects on groundwater flow through rock matrix and water seepage into the buffer material, the generation of swelling pressure of the buffer material, and thermal stresses potentially affecting porosity and fracture apertures of the rock. An in-situ T-H-M experiment named 'Engineered Barrier Experiment' has been conducted at the Kamaishi Mine, of which host rock is granodiorite, in order to establish conceptual models of the coupled T-H-M processes and to build confidence in mathematical models and computer codes. In 1995, fourteen boreholes were excavated in order to install the various sensors. After the hydraulic tests, mechanical tests were carried out to obtain the rock properties. After that, a test pit, 1.7m in diameter and 5.0m in depth, was excavated. During the excavation, the change of pore pressure, displacement and temperature of rock mass were measured. In 1996, the buffer material and heater were set up in the test pit, and then coupled thermo-hydro-mechanical test was started. The duration of heating phase was 250 days and that of cooling phase was 180 days. The heater surface was controlled to be 100 $^{circ}$ C during heating phase. Measurment, was carried out by a number pf sensors installed in both buffer and rock mass during the test. The field experiment leads to a better understanding of the behavior of the coupled thermo-hydro-mechanical phenomena in the near field.

JAEA Reports

Hydrochemical Investigation and Status of Geochemical Modeling of Groundwater Evolution at the Kamaishi In-situ Tests Site, Japan

Sasamoto, Hiroshi; Yui, Mikazu; Arthur, R. C,*

JNC TN8400 99-033, 153 Pages, 1999/07

JNC-TN8400-99-033.pdf:58.41MB

The results of hydrochemical investigations of groundwaters in the Kurihashi granodiorite at JNC's Kamaishi in-situ tests site indicate that these solutions are: (1)meteoric in origin, (2)chemically reducing (at depths greater than a few hundreds meters), (3)relatively young [residence times in the Kurihashi granodiorite generally less than about 40 years, but groundwaters older than several thousand years BP (before present) are also indicated by preliminary carbon-14 dating of samples obtained from the KH-1 borehole], (4)Ca-HCO $_{3}$ type solutions near the surface, changing to Na-HCO $_{3}$ type groundwaters with increasing depth. The evolution of groundwater compositions in the Kurihashi granodiorite 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, AI, carbonate and sulfate) in the Kurihashi granodiorite if the following assumptions are adopted: (1)CO $_{2}$ concentration in the gas phase contacting pore solutions in the overlying soil zone = 10 $^{-2}$ 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), microcline (K) and pyrite (Eh and sulfate). Discussions with international experts suggest a systematic approach utilizing reaction-path models of irreversible water-rock interactions in open systems may be needed to more realistically model groundwater evolution at the Kamaishi test site. Detailed information characterizing certain site properties (e.g., fracture mineralogy) may be required to adequately constrain such models, however.

JAEA Reports

Coupled thermo-hydro-mechanical experiment at Kamaishi mine technical note 14-99-01; Verification of the buffer material emplacement technique

Sugita, Yutaka; Chijimatsu, Masakazu*; Fujita, Tomoo; Tranduc, P.*

JNC TN8430 99-009, 45 Pages, 1999/06

JNC-TN8430-99-009.pdf:2.58MB

It is an important part of the near field performance assessment of nuclear waste disposal to evaluate coupled thermo-hydro-mechanical (T-H-M) phenomena, e.g., thermal effects on groundwater flow through rock matrix and water seepage into the buffer material, the generation of swelling pressure of the buffer material, and thermal stresses potentially affecting porosity and fracture apertures of the rock. An in-situ T-H-M experiment named "Engineered Barrier Experiment" was conducted at the Kamaishi Mine, in which the host rock is granodiorite, in order to establish conceptual models of the coupled T-H-M processes and to build confidence in mathematical models and computer codes. This report summarizes the results of the in-situ direct compaction technique to evaluate the appropriate conditions for this technique. The in-situ direct compaction technique is one of the major candidate emplacement techniques for the buffer material. This experiment consisted of the mock-up tests and the in-situ test. The mock-up tests showed the appropriate conditions for the in-situ direct compaction technique. For the in-situ experiment, the manufactured OT-9607 achieved dry density averaged 1.65 g/cm $^{3}$ , which matched the demand for the thermo-hydro-mechanical experiment.

JAEA Reports

Coupled Thermo-Hydro-Mechanical Experiment at Kamaishi Mine Technical Note 16-99-03, Analyses of Task 2C, DECOVALEXII

Chijimatsu, Masakazu*; Fujita, Tomoo; Kobayashi, Akira*; Onishi, Yuzo*

JNC TN8400 99-031, 61 Pages, 1999/06

JNC-TN8400-99-031.pdf:3.36MB

It is an important part of the near field performance assessment of nuclear waste disposal to evaluate couples thermo-hydro-mechanical (T-H-M) phenomena, e.g., thermal effects on groundwater flow through rock matrix and water seepage into the buffer material, the generation of swelling pressure of the buffer material, and thermal stresses potentially affecting porosity and fracture apertures of the rock. An in-situ T-H-M experiment naned 'Engineered Barrier Experiment' has been oonducted at the Kamaishi Mine, of which host rock is granodiorite, in order to establish conceptual models of the coupled T-H-M processes and to build confidence in mathematical models and computer codes. The coupled T-H-M experiment is one of tasks in DECOVALEX (DEvelopment of COupled models and their VALidation against EXperiments) project which is an international co-operative project and it is defined as Task 2. The Task 2 for the DECOVALEX project are divided into three subtasks (A-C) in accordance with the programme and availability of data, called subtasks. This note describes the results of subtask C. Subtask C is a coupled thermo-hydro-mechanical analysis in the near field.

JAEA Reports

None

Shimo, Michito*; Yamamoto, Hajime*; Takahara, Hiroyuki*; Doe, T.*

PNC TJ1205 98-001, 255 Pages, 1998/03

PNC-TJ1205-98-001.pdf:8.45MB

None

JAEA Reports

Diffusion Behaviour of Nuclides Considering Pathways in Fractured Crystalline Rocks

Sato, Haruo; ; ; *; *; Yui, Mikazu

PNC TN8410 97-127, 57 Pages, 1997/08

PNC-TN8410-97-127.pdf:1.51MB

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 25 $^{circ}$ C and batch sorption experiments for Cs, Sr, Se, $^{238}$ U and $^{239}$ 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 $_{2}$ 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 $_{3}$ $^{2-}$ ) are in the order of fracture fillings altered rock intact rock in proportion to these porosities. Effective diffusion ...