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Journal Articles

Impact of non-linear elastic behavior on bentonite density evolution at the FEBEX

Takayama, Yusuke

International Journal of Rock Mechanics and Mining Sciences, 136, p.104538_1 - 104538_8, 2020/12

 Times Cited Count:0 Percentile:100(Engineering, Geological)

It is necessary to apply reliable numerical simulation techniques to assess the mechanical behaviour of repositories for the geological disposal of radioactive waste over a long period of time. Having a constitutive model that can describe the mechanical behaviour of bentonite is key to such numerical simulations. In this study, the applicability of linear elastic constitutive model with swelling term is examined focusing on the density heterogeneity by applying to the in situ Full-scale Engineered Barrier Experiment (FEBEX) in Grimsel. It was confirmed that this constitutive model underestimates the density change. Instead, mechanical behaviour was re-simulated by unsaturated elasto-plastic constitutive model using the changes in degree of saturation as input data. Although no feedback effects of mechanical behaviour on hydraulic and thermal behaviour were taken into account, two-dimensional stress and density could be reproduced.

JAEA Reports

Collection of measurement data from in-situ experiment for performance confirmation of engineered barrier system at Horonobe Underground Research Laboratory (until March, 2018)

Nakayama, Masashi; Ono, Hirokazu; Nakayama, Mariko*; Kobayashi, Masato*

JAEA-Data/Code 2019-003, 57 Pages, 2019/03

JAEA-Data-Code-2019-003.pdf:18.12MB
JAEA-Data-Code-2019-003-appendix(CD-ROM).zip:99.74MB

The Horonobe URL Project has being pursued by JAEA to enhance the reliability of relevant disposal technologies through investigations of the deep geological environment within the host sedimentary formation at Horonobe, northern Hokkaido. The URL Project consists of two major research areas, Geoscientific Research and Research and Development on Geological Disposal Technologies, and proceeds in 3 overlapping phases, Phase I: Surface-based investigations, Phase II: Investigations during tunnel excavation and Phase III: Investigations in the URL, over a period of around 20 years. Phase III investigation was started in 2010 FY. The in-situ experiment for performance confirmation of engineered barrier system had been prepared from 2013 to 2014 FY at GL-350 m gallery, and heating by electric heater in simulated overpack had started in January, 2015. One of objectives of the experiment is acquiring data concerned with THMC coupled behavior. These data will be used in order to confirm the performance of engineered barrier system. This report summarizes the measurement data acquired from the experiment from December, 2014 to March, 2018. The summarized data of the EBS experiment will be published periodically.

Journal Articles

Matrix diffusion and sorption of Cs$$^{+}$$, Na$$^{+}$$, I$$^{-}$$ and HTO in granodiorite; Laboratory-scale results and their extrapolation to the in situ condition

Tachi, 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:23 Percentile:19.85(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.

JAEA Reports

Excavation and preparation rock block sample for LABROCK

Uchida, Masahiro;

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

None

*

JNC-TJ7400 2000-015, 203 Pages, 2000/08

JNC-TJ7400-2000-015.pdf:6.07MB

no abstracts in English

JAEA Reports

Investigation on sealing technique in geological disposal

*; Toida, Masaru*; Masumoto, Kazuhiko*

JNC-TJ8400 2000-021, 196 Pages, 2000/02

JNC-TJ8400-2000-021.pdf:8.23MB

For the geological disposal of high level radioactive wastes, after placement of tbe wastes, it is necessary to close off (to be called "sealing" hereafter) the underground potential passages (disposal pits, disposal tunnels, main and connecting tunnels and access tunnels) with an effective combination of engineered barriers such as buffers, backfilling materials, plugs and grout. It is necessary to ensure the long-term durability to isolate disposed wastes in the system. The results of the research works this year are as follows; (1)The objectives are to discuss the design of tunnel sealing experiments at URL site. The results of research were about (a)tracer experiment and numerical analysis (b)evaporation measurement (c)presentation at the coordination meeting (2)The discussion was about the equipment of inclined compaction methods and bearing capacity of rock against pressures for the concrete plugs.

JAEA Reports

Investigation on sealing technique in geological disposal

Toida, Masaru*; Masumoto, Kazuhiko*; *; Okutsu, Kazuo*; *

JNC-TJ8400 2000-020, 68 Pages, 2000/02

JNC-TJ8400-2000-020.pdf:5.87MB

For the geological disposal of high level radioactive wastes, after placement of the wastes, it is necessary to close off (to be called "sealing" hereafter) the underground potential passages (disposal pits, disposal tunnels, main and connecting tunnels and access tunnels) with an effective combination of engineered barriers such as buffers, backfiling materials, plugs and grout. It is necessary to ensure the long-term durability to isolate disposed wastes in the system. The results of the research works this year are as follows ; (1)The objectives are to discuss the design of tunnel sealing experiments at URL site. The results of research were about (a)tracer experiment and numerical analysis (b)evaporation measurement (c)presentation at the coordination meeting. (2)The discussion was about the equipment of inclined compaction methods and bearing capacity of rock against pressures for the concrete plugs.

JAEA Reports

None

Toida, Masaru*; Shiogama, Yukihiro*; Atsumi, Hiroyuki; Masumoto, Kazuhiko*; *; Abe, Yasunori*; *

JNC-TJ7440 2000-006, 137 Pages, 2000/02

JNC-TJ7440-2000-006.pdf:3.55MB

no abstracts in English

JAEA Reports

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

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

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

JNC-TN8400-2000-008.pdf:15.57MB

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 hydraunc 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. nle 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

Status of geochemical modeling of groundwater evolution at the Tono in-situ tests site,Japan In-situ Tests

Sasamoto, Hiroshi; Yui, Mikazu; Randolph C Arthu*

JNC-TN8400 99-074, 84 Pages, 1999/12

JNC-TN8400-99-074.pdf:6.79MB

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$$_{3}$$ type solutions near the surface, changing to Na-HCO$$_{3}$$ 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$$_{2}$$ concentration in the gas phase contacting pore solutions in the overlying soil zone = 10$$^{-1}$$ 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.

JAEA Reports

None

*

JNC-TJ6400 2000-007, 48 Pages, 1999/03

JNC-TJ6400-2000-007.pdf:1.23MB

None

JAEA Reports

None

Kato, Toshihiro*; ; ; ; Ishibashi, Yuzo; Takeda, Seiichiro

PNC-TN8410 98-070, 31 Pages, 1998/02

PNC-TN8410-98-070.pdf:0.96MB

None

JAEA Reports

None

Imai, Hisashi*; Nishida, Kaoru*; *; Amemiya, Kiyoshi*; Lin, Weiren*

PNC-TJ1449 98-004, 231 Pages, 1998/02

PNC-TJ1449-98-004.pdf:16.85MB

None

JAEA Reports

None

*; Toida, Masaru*; Shiogama, Yukihiro*; *; *; Fukazawa, E.*; Tanaka, M.*

PNC-TJ1100 98-004, 88 Pages, 1998/02

PNC-TJ1100-98-004.pdf:2.23MB

None

JAEA Reports

None

*; Toida, Masaru*; Shiogama, Yukihiro*; *; *; Fukazawa, E.*; Tanaka, M.*

PNC-TJ1100 98-003, 204 Pages, 1998/02

PNC-TJ1100-98-003.pdf:5.88MB

None

JAEA Reports

None

; *

PNC-TN8420 97-013, 24 Pages, 1997/10

PNC-TN8420-97-013.pdf:1.24MB

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 $$sim$$ 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 (pH8.7$$sim$$9.5) 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 ...

JAEA Reports

None

PNC-TN1000 97-003, 55 Pages, 1997/03

PNC-TN1000-97-003.pdf:2.0MB

no abstracts in English

JAEA Reports

None

PNC-TJ6622 97-001, 38 Pages, 1997/03

PNC-TJ6622-97-001.pdf:1.33MB

None

JAEA Reports

None

Imai, Hisashi*; Amemiya, Kiyoshi*; Nishida, Kaoru*; Lin, Weiren*; *

PNC-TJ1449 97-002, 261 Pages, 1997/03

PNC-TJ1449-97-002.pdf:48.99MB

no abstracts in English

67 (Records 1-20 displayed on this page)