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Sato, Hisashi*; Takayama, Yusuke; Suzuki, Hideaki*; Sato, Daisuke*
JAEA-Data/Code 2023-010, 47 Pages, 2023/09
JAEA-Data-Code-2023-010.pdf:1.45MB
When a high-level radioactive waste repository is constructed in a coastal area, it is necessary to fully evaluate the impact of seawater-based groundwater on engineered barriers, including buffer materials. In this report, one-dimensional saltwater infiltration tests were conducted to obtain data to understand the impact of seawater-based groundwater on the migration phenomena of water and solutes in the buffer material during the transient period. As a result, it was confirmed that the infiltration rate increased as the NaCl concentration in the infiltration solution increased. And it was confirmed that the water content ratio distribution changed as the NaCl concentration in the infiltration solution increased. As a result of analysis of the chloride ion concentration of the post-test specimens confirmed that chloride ion enrichment was occurred with infiltration. As a result of verifying the mechanism by which chloride ion enrichment occurs, it was confirmed that the phenomenon of chloride ion enrichment due to infiltration depends on the initial water content ratio.
Taniguchi, Naoki; Kawakami, Susumu; *
JNC TN8400 2001-025, 27 Pages, 2002/03
JNC-TN8400-2001-025.pdf:1.16MB
It is essential to understand the corrosion type of carbon steel under the repository conditions for the lifetime assessment of carbon steel overpack used for geological isolation of high-level radioactive waste. According to the previous study, carbon steel is hard to passivate in buffer material assuming a chemical condition range of groundwater in Japan. However, concrete support will be constructed around the overpack in the case of repository in the soft rock system and groundwater having a higher pH may infiltrate to buffer material. There is a possibility that the corrosion type of carbon steel will be influenced by the rise of the pH in groundwater. In this study, anodic polarization experiments were performed to understand the passivation condition of carbon steel in buffer material saturated with water contacted with concrete. An ordinary concrete and a low-alkalinity concrete were used in the experiment. The results of the experiments showed that the carbon steel can passivate under the condition that water having pH 
13 infiltrate to the buffer material assuming present property of buffer material. If the low-alkalinity concrete is selected as the support material, passivation can not occur on carbon steel overpack. The effect of the factors of buffer material such as dry density and mixing ratio of sand on the passivation of carbon steel was also studied. The results of the study showed that the present property of buffer material is enough to prevent passivation of carbon steel.
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
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.
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 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.
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 ...
Shibata, Masahiro; Yamagata, Junji*; Suzuki, Hideaki*
PNC TN8410 92-169, 64 Pages, 1992/08
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