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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.
Takayama, Yusuke
International Journal of Rock Mechanics and Mining Sciences, 136, p.104538_1 - 104538_8, 2020/12
Times Cited Count：3 Percentile：24.61(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.
Takai, Shizuka; Kimura, Hideo*; Uchikoshi, Emiko*; Munakata, Masahiro; Takeda, Seiji
JAEA-Data/Code 2020-007, 174 Pages, 2020/09
JAEA-Data-Code-2020-007.pdf:4.23MB
The MIG2DF computer code is a computer program that simulates groundwater flow and radionuclide transport in porous media for the safety assessment of radioactive waste disposal. The original version of MIG2DF was released in 1992. The original code employs a two-dimensional (vertical or horizontal cross-section, or an axisymmetric configuration) finite-element method to approximate the governing equations for density-dependent saturated-unsaturated groundwater flow and radionuclide transport. Meanwhile, for geological disposal of radioactive wastes, landscape evolution such as uplift and erosion needs to be assessed as a long-term geological and climate events, considering site conditions. In coastal areas, the impact to groundwater flow by change of salinity distribution to sea level change also needs to be considered. To deal with these events in the assessment, we have revised the original version of MIG2DF and developed the external program which enables MIG2DF to consider unsteady landscape evolution. In these developments, this report describes an upgrade of MIG2DF (Version 2) and presents the configuration, equations, methods, and verification. This reports also give the explanation external programs of MIG2DF: PASS-TRAC (the particle tracking code), PASS-PRE (the code for dataset preparation), and PASS-POST (the post-processing visualization system).
Kubota, Kenji*; Aoyagi, Kazuhei; Sugita, Yutaka
Proceedings of 2019 Rock Dynamics Summit in Okinawa (USB Flash Drive), p.729 - 733, 2019/05
During the excavation of shafts and galleries in the deep subsurface for disposing of high-level radioactive waste, an excavation disturbed zone (EdZ) or excavation damaged zone (EDZ) is developed around the shafts and galleries. Such zones could influence the transfer behavior of radioactive nuclides, and it is therefore important to understand the behavior of the EdZ or EDZ. We performed in situ experiments before, during, and after gallery excavation in galleries of 140 and 250 m in depth in an area of soft sedimentary rock in Japan. The results demonstrate that the extent of fractures induced by the gallery excavation related with EDZ was confined to about 0.45 m from the gallery wall in the 140 m gallery and to about 1 m from the gallery wall in the 250 m gallery. The extent of the unsaturated zone related with EdZ was about 1 m in the 140 m gallery, but an unsaturated zone did not appear in the 250 m gallery.
Sakai, Akihiro; Kurosawa, Ryohei*; Totsuka, Masayoshi; Nakata, Hisakazu; Amazawa, Hiroya
JAEA-Technology 2016-032, 117 Pages, 2017/02
JAEA-Technology-2016-032.pdf:12.84MB
JAEA has been planning to implement near surface disposal of low level waste generated from research, medical, and industrial facilities. JAEA plans to carry out 3d analysis of groundwater flow in geological model around the disposal site because of development of migration assessment modeling of radioactivity materials in the site. In the safety demonstration test in JAEA, 3d analysis of groundwater flow was carried out on 1999. The analysis was calculated by using the code "3D-SEEP". But it is necessary to improve the conditions of the model in the analysis. Therefore, we improved the geological model which had been developed carried out 3d analysis of groundwater flow by using the current 3D-SEEP for the specified disposal site in the future. From the result, we expect that 3d analysis of groundwater flow in the environment around the specified near surface disposal site will be able to be sufficiently conducted by developing an appropriate model for the disposal site.
Komatsu, Teruhisa; Adachi, Takeo
Journal of Applied Meteorology, 42(9), p.1330 - 1334, 2003/09
no abstracts in English
*; Saegusa, Hiromitsu
JNC TY7400 2000-004, 62 Pages, 2000/05
JNC-TY7400-2000-004.pdf:1.45MB
None
*; *; *; *
JNC TJ8400 2000-005, 71 Pages, 2000/05
In this research, simulations with some parameters which characterize ground water flow and the reliability evaluation for the expansion of the calculation method of groundwater flow were carried out by using the radionuclide transport computations in nearfield heterogeneous porous media. Concretely contents are follows: (1)With the series of calculation method for three-dimensional saturated/unsaturated groundwater flow and one-dimensional radionuclide transport, the computational analyses with the parameters used in JNC report in 2000 was carried out and the influence of the different input flux was evaluated. (2)The examination of the application for the different ways of inverse laplace transformation which is used in one-dimensional radionuclide transport analysis code "MATRICS" was carried out. (3)The examination of the application of multi-element "MATRICS" (m-MATRICS) for radionuclide transport computations in nearfield heterogeneous porous media was carried out. (4)The series of calculation methods from three-dimensional saturated/unsaturated ground water flow simulation code to one-dimensional radionuclide transport simulation code was integrated.
Kudo, Akira*; Fujikawa, Yoko*
JNC TJ8400 2000-010, 67 Pages, 2000/02
JNC-TJ8400-2000-010.pdf:2.17MB
The first and second environmental releases of man-made 
Pu came from nuclear explosions at Alamagordo and Nagasaki in 1945. The release at Nagasaki was more serious than at Alamagordo, because it happened in an area with a high population density. Unfissioned Pu and various fission products have been interacting here with various environmental materials (soils, sediments, and plants) under wet and temperature conditions for more than 45 years. To assess the environmental mobility of Pu, the distributions of radionuclides from this release were investigated at Nishiyama where heavy black rain containing unfissioned plutonium and fission products fell 30 minutes after the nuclear explosion. The vertical distributions of 
Cs and Pu were determined in unsaturated soil cores up to 450cm deep. Most radionuclides were found in the soil column 30cm from the ground surface. However, Pu were detected in the groundwater as well below a depth of 200cm. No Cs was found below 40cm from the ground surface or in groundwater. These observations reveal that about 3% of the total Pu have been migrating in the soil at a faster rate than the remaining Pu. Sharp peak of Cs and Pu, indicating heavy deposition from the Nagasaki local fallout of 1945, were found in sediment cores collected from the Nishiyama reservoir. Pu peaks were unexpectedly discovered in pre-1945 sediment core sections. NO Cs was found. By contrast to the distribution in sediment cores, Cs in tree rings had spread by diffusion from the bark to the center of the tree without holding a fallout deposition record. Most of the Pu was distributed in the tree rings following a similar deposition record to that found in sediment cores. Furthermore, a very small amount of Pu (about 1%) was found unexpectedly in pre-1945 tree rings. The only reasonable ...
Ikeda, Takao*; Yoshida, Hideji*
JNC TJ7400 2000-006, 159 Pages, 2000/02
JNC-TJ7400-2000-006.pdf:4.81MB
no abstracts in English
Nishida, Kaoru*; Maemura, Tsuneyuki*
JNC TJ7400 2000-004, 102 Pages, 2000/02
JNC-TJ7400-2000-004.pdf:5.64MB
no abstracts in English
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 ...
Rn in unsaturated soilKoarashi, Jun; Amano, Hikaru; Iida, T.*; Yamazawa, Hiromi; Nagai, Haruyasu
Proceedings of 10th International Congress of the International Radiation Protection Association (IRPA-10) (CD-ROM), 9 Pages, 2000/00
no abstracts in English
Imai, Hisashi*; Nishida, Kaoru*; *; Amemiya, Kiyoshi*; Lin, Weiren*
PNC TJ1449 98-004, 231 Pages, 1998/02
None
*; Toida, Masaru*; Shiogama, Yukihiro*; *; Yasui, Shingo*; Fukazawa, E.*; Tanaka, M.*
PNC TJ1100 98-004, 88 Pages, 1998/02
None
*; Toida, Masaru*; Shiogama, Yukihiro*; *; Yasui, Shingo*; Fukazawa, E.*; Tanaka, M.*
PNC TJ1100 98-003, 204 Pages, 1998/02
None
Imai, Hisashi*; Amemiya, Kiyoshi*; Nishida, Kaoru*; Lin, Weiren*; *
PNC TJ1449 97-002, 261 Pages, 1997/03
no abstracts in English
Imai, Hisashi*; Amemiya, Kiyoshi*; Nishida, Kaoru*; Lin, Weiren*; *; Senna, Shigeki*
PNC TJ1449 96-005, 76 Pages, 1996/03
None
