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Miyakawa, Kazuya; Yamamoto, Hajime*
JAEA-Research 2022-003, 40 Pages, 2022/05
JAEA-Research-2022-003.pdf:6.08MB
The excavation of large-scale underground facilities, such as geological disposal of high-level radioactive waste, creates an excavation damaged zone (EDZ) with cracks around the tunnel. In the EDZ, oxygen invades the bedrock through unsaturated cracks and affects environmental conditions for nuclide migration. When a tunnel is excavated in a geological formation containing a high concentration of dissolved CH
, such as the Neogene marine sediments, degassed CH prevents oxygen intrusion. However, it may be promoted through gas-phase diffusion through desaturation. The purpose of this study is to illustrate the method of estimating the spatial distribution of desaturation associated with the construction and operation of underground facilities in a stratum that contains a large amount of dissolved CH. A sequential excavation analysis that reflected the actual process of 10-year excavation of the Horonobe Underground Research Laboratory (URL) was carried out along with gas-water two-phase flow analysis. The analysis results of the amount of groundwater and gas discharged from the URL were about 100 to 300 m
d
and 250 to 350 m d, respectively, as of January 2017. These results showed values close to the observations (100 m d and 300 m d, respectively). The analysis results of the saturation distribution were relatively high around the 250 m gallery and relatively low around the 350 m gallery, confirming that they are consistent with the in-situ observations. Although there were still technical issues of analysis regarding the conditions for groundwater drainage from the tunnel wall and the method of handling grout effects, the numerical calculation was generally appropriate. Although the results of the saturation distribution associated with the excavation were insufficient as the quantitative evaluation, they were almost correct from a qualitative point of view.
Miyakawa, Kazuya; Aoyagi, Kazuhei; Akaki, Toshifumi*; Yamamoto, Hajime*
JAEA-Data/Code 2021-002, 26 Pages, 2021/05
JAEA-Data-Code-2021-002.pdf:2.14MB
JAEA-Data-Code-2021-002-appendix(CD-ROM).zip:40.99MB
Investigations employing numerical simulation have been conducted to study the mechanisms of desaturation and oxygen infusion into sedimentary formations. By mimicking the conditions of the Horonobe underground research laboratory, numerical simulations aided geoscientific investigation of the effects of dissolved gas content and rock permeability on the desaturation (Miyakawa et al., 2019) and mechanisms of oxygen intrusion into the host rock (Miyakawa et al., 2021). These simulations calculated multi-phase flow, including flows of groundwater and exsolved gas, and conducted sensitivity analysis changing the dissolved gas content, rock permeability, and humidity at the gallery wall. Only the most important results from these simulations have been reported previously, because of publishers' space limitations. Hence, in order to provide basic data for understanding the mechanisms of desaturation and oxygen infusion into rock, all data for 27 output parameters (e.g., advective fluxes of heat, gas, and water, diffusive fluxes of water, CH, CO
, O, and N, saturation degree, water pressure, and mass fraction of each component) over a modeling period of 100 years are presented here.
Miyakawa, Kazuya; Aoyagi, Kazuhei; Akaki, Toshifumi*; Yamamoto, Hajime*
Dai-15-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (Internet), p.609 - 614, 2021/01
Desaturation is expected due to excavation of an underground repository, especially in the newly created fractures zone (EDZ). During the construction and operation of facilities, the air in the gallery infuses into the rock around the gallery though the excavation affected area and causes oxidation of host rock and groundwater, which increase nuclide mobilities. In the Horonobe underground research laboratory (HURL), which is excavated in the Neogene sedimentary formations, no pyrite dissolution or precipitation of calcium sulfates was found from the cores drilled in the rock around the gallery. The reason for no oxidation is estimated that the release of dissolved gases from groundwater due to pressure decrease flows against the air infusion. In this research, the mechanism of O intrusion into the rock was investigated by numerical multiphase flow simulation considering advection and diffusion of groundwater and gases. In the simulation, only Darcy's and Henry's laws were considered, that is, chemical reaction related to oxidation was not handled. The effects of dissolved gas and rock permeability on O infusion into the rock were almost identical. Decreasing humidity with relatively low permeability leads to extensive accumulation of O into the EDZ even though with a relatively large amount of dissolved gas. In the HURL, the shotcrete attenuates O concentration and keeps 100% humidity at the boundary of the gallery wall, which inhibits O infusion. Without the shotcrete, humidity at the gallery wall decreases according to seasonal changes and ventilation, which promotes O intrusion into the EDZ but the chemical reaction related to O buffering such as pyrite oxidation consumes O.
Miyakawa, Kazuya; Aoyagi, Kazuhei; Sasamoto, Hiroshi; Akaki, Toshifumi*; Yamamoto, Hajime*
Proceedings of 5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future (YSRM 2019 and REIF 2019) (USB Flash Drive), 6 Pages, 2019/12
The construction and operation of geological repositories require excavation and ventilation of galleries, with significant groundwater drainage. Desaturation of rock around galleries is unavoidable and may affect hydraulic properties and redox conditions. This study used numerical modeling to assess the influence of dissolved gas on the degree of saturation of rock surrounding excavated galleries, focusing on siliceous mudstone rock in the 140 m, 250 m, and 350-m-deep galleries of the Horonobe Underground Research Laboratory, Japan. Based on previous 
electrical survey, the degree of saturation in the 250 m gallery was higher than that in the 140 m and 350 m galleries. In the Horonobe area, deep groundwater contains high concentrations of dissolved methane, and exsolution of this methane from pore water can affect desaturation. Simple numerical modeling, including simulation of multiphase flows, was undertaken for each gallery to confirm the effect of dissolved gas and rock permeability on desaturation. A sensitivity analysis was performed by varying dissolved gas contents and permeability. Results indicate that the dissolved gas content affects both the degree of saturation and its spatial extent, whereas rock permeability affects only the latter. Higher dissolved gas concentrations result in lower degrees of saturation with a greater spatial extent of desaturation, and higher permeability leads to greater extents of desaturation. It is therefore likely that gas content, rather than rock permeability, caused the observed variations in the saturation degree.
Watanabe, Fumitaka; Okuno, Hiroshi
Proceedings of 18th International Symposium on the Packaging and Transport of Radioactive Materials (PATRAM 2016) (DVD-ROM), 9 Pages, 2016/09
This paper shows our calculations on the effects of a radiological release by assuming a severe accident in nuclear material transportation. Following recalculations of safe distance from the point of a severe accident during transportation of a transportation cask TN12 typically used in France containing spent nuclear fuel, and calculations to replicate the "Regulatory Guide: Emergency Preparedness for Nuclear Facilities", a similar calculation was made for a spent fuel transportation cask NFT-14P that was typically utilized in Japan instead of TN12. The safe distance was calculated to be about 30 m. The above calculations were made with the HotSpot codes which adopted the Gauss plume model and had been developed by the USA. Some additional calculations were made with EyesAct, which was developed and used in Japan, adopting also the Gauss plume model, to compare calculation results.
emission reduction goal in 2050Kamiji, Yu; Suzuki, Koichi*; Yan, X.
JAEA-Technology 2016-010, 24 Pages, 2016/07
JAEA-Technology-2016-010.pdf:1.05MB
Japanese government has set the goal of reducing CO emission by 26% in 2030 below the 2013 level, in longer term, by 80% below the 1990 level. To achieve the goals, various measures should be taken. The GTHTR300, a commercial High Temperature Gas-cooled Reactor (HTGR) design being developed by JAEA offers spectrum of heat applications by using its high temperature heat up to 950
C. The potential contribution of CO emission reduction by HTGR is estimated considering domestic and overseas deployment of the GTHTR300. The best estimate for domestic CO reduction is 2.07
10
ton- CO/yr and that from oversea is 2.2510 ton- CO/yr. The sum of these is about 47% of 9.1310 ton- CO/yr which is CO reduction target in 2050, for which deployment of 52 plants in Japan and 113 plants abroad, with each plant containing four 600 MWt reactor units, is required.
Saigusa, Shin*
RIST News, (32), p.2 - 11, 2001/10
The Japan Atomic Energy Research Institute (JAERI) had carried out the specially funded project of constructing a database "DRESA (Database for Radiation Exposure and Safety Assessment)" with an electronic text on safety assessment of low dose ionizing radiation. The contents and the database system were arranged and designed to provide the fundamental information/data for scientific and reasonable understanding of radiation health effects, radiation risk assessment and radiation protection. Present report explained the data title and its contents, data file formats and system structure of the database. Potentialities and difficulties in constructing WWW database were also discussed.
Osabe, Takeshi*; Usuda, Shigekazu
Kaku Busshitsu Kanri Senta Nyusu, 29(10), p.5 - 9, 2000/10
no abstracts in English
Sasaki, Toshihiko*; Minakawa, Nobuaki; Morii, Yukio; Niimura, Nobuo; Hirose, Yukio*
Nihon Zairyo Gakkai Dai-36-Kai X Sen Zairyo Kyodo Ni Kansuru Shimpojiumu Koen Rombunshu, p.259 - 262, 2000/09
no abstracts in English
Takago, S.*; Sasaki, Toshihiko*; Minakawa, Nobuaki; Morii, Yukio; Hirose, Yukio*
Proceedings of 6th International Conference on Residual Stressess (ICRS-6), Vol.1, p.41 - 48, 2000/07
no abstracts in English
Tsuchiya, Yoshinori; Kikuchi, Kenji; Minakawa, Nobuaki; Morii, Yukio; Kato, Takashi; Nakajima, Hideo; Tsuji, Hiroshi
Nihon Zairyo Gakkai Dai-49-Ki Gakujutsu Koenkai Rombunshu, p.325 - 326, 2000/05
no abstracts in English
Nishimura, Hideo
Kaku Busshitsu Kanri Senta Nyusu, 28(8), p.5 - 7, 1999/08
no abstracts in English
Inoue, Kazuko*; Horikawa, Takeshi*; *; *; Minakawa, Nobuaki; Tsuchiya, Yoshinori*; Morii, Yukio; *
Japanese Journal of Applied Physics, Part 1, 37(10), p.5680 - 5686, 1998/10
Times Cited Count：2 Percentile：13.52(Physics, Applied)no abstracts in English
*; Kunugi, Tomoaki*; *; *
Keisan Kogaku Koenkai Rombunshu, 3(1), p.235 - 238, 1998/05
no abstracts in English
*
CIPUS Annual Report, 4 Pages, 1998/00
no abstracts in English
Maruyama, Yoichiro; Kato, Masaaki; Arisawa, Takashi
Opt. Eng., 35(4), p.1084 - 1087, 1996/04
Times Cited Count：11 Percentile：55.85(Optics)no abstracts in English
Hidaka, Akihide; Soda, Kunihisa; Sugimoto, Jun; Yamano, N.; Maruyama, Yu
KfK-5108; NEA/CSNI/R(92)10, p.211 - 225, 1992/00
no abstracts in English
Fink, J. K.*; Corradini, M.*; Hidaka, Akihide; Honta
n, E.*; Mignanelli, M. A.*; Schr
dl, E.*; Strizhov, V.*
KfK-5108; NEA/CSNI/R(92)10, p.533 - 546, 1992/00
no abstracts in English
Watanabe, Norio
IAEA-SR-169, 46 Pages, 1990/05
no abstracts in English
J.Lovett*; ; J.Shipley*; D.Sellinschegg*
J.Inst.Nucl.Mater.Manage., 12, p.31 - 34, 1983/00
no abstracts in English
