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JAEA Reports

None

; ; *

JNC-TY7430 2000-001, 57 Pages, 2000/03

JNC-TY7430-2000-001.pdf:2.17MB

no abstracts in English

JAEA Reports

Research on engineering procedure and models on buffer materials

Amemiya, Kiyoshi*; TRAN DUC PHI OAN*; Yamashita, Ryo*

JNC-TJ8400 2000-056, 487 Pages, 2000/02

JNC-TJ8400-2000-056.pdf:16.24MB

JNC presented the 2$$^{nd}$$ progressive reports on HLW disposal system. The documents impressed the importance of developing the engineering procedures and the model evaluating the thermo-hydro-mechanical phenomena in waste disposal system. In this research, the methods filling the gap between buffer and rock or buffer and overpack were examined. Bentonite pellets were tested as the filling materials. In order to assess the full-scale system performance, the Japanese experiences of buffer mass experiments were compared with the Prototype Repository Project of SKB in Sweden. Father more, the thermo-hydro-mechanical (THM) code named TRAMES was validated at the international co-research programs of DECOVALEX II.

JAEA Reports

Research on engineering procedure and models on buffer materials

Amemiya, Kiyoshi*; TRAN DUC PHI OAN*; Yamashita, Ryo*

JNC-TJ8400 2000-055, 49 Pages, 2000/02

JNC-TJ8400-2000-055.pdf:4.15MB

JNC presented the 2$$^{nd}$$ progressive reports on HLW disposal system. The documents impressed the importance of developing the engineering procedures and the model evaluating the thermo-hydro-mechanical phenomena in waste disposal system. In this research, the methods filling the gap between buffer and rock or buffer and overpack were examined. Bentonite pellets were tested as the filling materials. In order to assess the full-scale system performance, the Japanese experiences of buffer mass experiments were compared with the Prototype Repository Project of SKB in Sweden. Father more, the thermo-hydro-mechanical (THM) code named THAMES was validated at the international co-research programs of DECOVALEX II.

JAEA Reports

A Preliminary assessment of gas diffusion and migration

Tanai, Kenji; Sato, Haruo; *; *

JNC-TN8400 99-045, 108 Pages, 1999/11

JNC-TN8400-99-045.pdf:4.48MB

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$$^{-3}$$) ranges from 10$$^{-10}$$ m$$^{2}$$ s$$^{-1}$$ to 10$$^{-11}$$ m$$^{2}$$s$$^{-1}$$. The value of the effective diffusion coefficient measured for a dry density of 1.8 Mg m$$^{-3}$$ is slightly smaller than the value in that for a dry density 1.6 Mg m$$^{-3}$$. And the effective diffusion coefficient at 60$$^{circ}$$C tends to have slightly larger value than that at 25$$^{circ}$$C. Test results from the foreign countries show the diffusion coefficient in the range between 10$$^{-9}$$ m$$^{2}$$s$$^{-1}$$ to 10$$^{-12}$$m$$^{2}$$s$$^{-1}$$. 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 ...

JAEA Reports

Assessment on the mechanical stability of underground excavations

; Taniguchi, Wataru; Koo, Shigeru*; Hasegawa, Hiroshi; ; Kubota, Shigeru*; *

JNC-TN8400 99-037, 281 Pages, 1999/11

JNC-TN8400-99-037.pdf:15.51MB

It is planned to construct the tunnels and emplace waste packages at several hundred meters to 1,000 meters under the ground for the repository of high-level radioactive waste based on a policy to assure the safe life environment. It is required to be mechanically stable for the tunnels to assure the work safety throughout the construction, operation and closure phase. In this report, the mechanical stability of tunnels, that is a factor of design requisites, was evaluated by the analyses to present an outline of the technical reliability of geological disposal. To put it concretely, the tunnel sections were determined to have the required areas and shapes, and the analyses on the mechanical stability at tunnel excavations and earthquake, at tunnel intersections were conducted by the theoretical analysis and finite element method. The results obtained by these investigations are shown below: (1)It will be able to construct the tunnels with present techniques. The mechanical stability of tunnels will be assured if proper supports are given, and adequate tunnel spacing and disposal-pit pitches are set. (2)The mechanical stability will be assured at the tunnels intersections if proper reinforcement measures are taken. The reinforcement will be required for the intersection areas over the distance of 1D (D: diameter of tunnels) on the obtuse angle side, and 4D on the acute angle side, when intersection angle is set at 30 degrees. (3)The investigations were conducted on the assumption that the experienced big earthquake occurred. The results show that the effect of earthquake on the mechanical stability of tunnels is small, and tunnels are stable at the earthquake when the mechanical stability at tunnel excavations is assured.

JAEA Reports

None

; ; Shimizu, Kazuhiko; Miyahara, Kaname; ; Hasegawa, Hiroshi; Iwasa, Kengo

JNC-TN1400 99-008, 656 Pages, 1999/04

JNC-TN1400-99-008.pdf:34.68MB

None

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