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JAEA Reports

The In-situ experiment for performance confirmation of engineered barrier system at Horonobe Underground Research Laboratory; Consideration of concrete-type plug composition

Nakayama, Masashi; Niunoya, Sumio*; Miura, Norihiko*; Takeda, Nobufumi*

JAEA-Research 2017-016, 62 Pages, 2018/01

JAEA-Research-2017-016.pdf:19.99MB

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, Hokkaido. The URL Project consists of 2 major research areas, "Geoscientific Research" and "Research and Development on Geological Disposal Technologies", and proceeds in 3 overlapping phases, over a period of around 20 years. Phase III (Investigations in the underground facilities) investigation was started in 2010 FY. The in-situ experiment for performance confirmation of engineered barrier system (EBS experiment) had started 2013 at GL-350 m gallery, and heating by electric heater in simulated overpack had started in January, 2015. One of objectives of the EBS 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 shows consideration of concrete-type plug composition. The low alkaline cement developed by JAEA, called HFSC, was used for the plug. HFSC has used in construction test at the gallery as shotcrete in Horonobe URL.

JAEA Reports

Study on engineering technologies in the Mizunami Underground Research Laboratory (FY 2015); Development of recovery and mitigation technology on excavation damage (Contract research)

Fukaya, Masaaki*; Takeda, Nobufumi*; Miura, Norihiko*; Ishida, Tomoko*; Hata, Koji*; Uyama, Masao*; Sato, Shin*; Okuma, Fumiko*; Hayagane, Sayaka*; Matsui, Hiroya; et al.

JAEA-Technology 2016-035, 153 Pages, 2017/02

JAEA-Technology-2016-035.pdf:37.6MB

The researches on engineering technology in the Mizunami Underground Research Laboratory (MIU) project in FY2016, detailed investigations of the ( mechanical )behaviors of the plug and the rock mass around the reflood tunnel through ongoing reflood test were performed as part of (5) development of technologies for restoration and/or reduction of the excavation damage. As the result, particularly for the temperature change of the plug, its analytical results agree fairly well agree with the measurement ones. This means cracks induced by temperature stress can be prevented by the cooling countermeasure works reviewed in designing stage. In addition, for the behaviors of the plug and the bedrock boundary after reflooding the reflood tunnel, comparison between the results obtained by coupled hydro-mechanical analysis (stress-fluid coupled analysis ) with the ones by several measurements, concluded that the model established based on the analysis results is generally appropriated.

JAEA Reports

Study on engineering technologies in the Mizunami Underground Research Laboratory (FY 2014); Development of recovery and mitigation technology on excavation damage (Contract research)

Fukaya, Masaaki*; Hata, Koji*; Akiyoshi, Kenji*; Sato, Shin*; Takeda, Nobufumi*; Miura, Norihiko*; Uyama, Masao*; Kaneda, Tsutomu*; Ueda, Tadashi*; Hara, Akira*; et al.

JAEA-Technology 2016-002, 195 Pages, 2016/03

JAEA-Technology-2016-002.pdf:46.3MB
JAEA-Technology-2016-002-appendix(CD-ROM).zip:16.11MB

The researches on examination of the plug applied to the future reflood test was conducted as a part of (5) development of technologies for restoration and/on reduction of the excavation damage relating to the engineering technology in the MIU (2014), specifically focused on (1) plug examination (e.g. functions, structure and material) and the quality control methods and (2) analytical evaluation of rock mass behavior around the plug through the reflood test. As the result, specifications of the plug were determined. These specifications should be able to meet requirements for the safety structure and surrounding rock mass against predicted maximum water pressure, temperature stress and seismic force, and for controlling the groundwater inflow, ensuring the access into the reflood gallery and the penetration performance of measurement cable. Also preliminary knowledge regarding the rock mass behavior around the plug after flooding the reflood gallery by installed plug was obtained.

JAEA Reports

Study on applicability of low alkaline cement in Horonobe Underground Research Laboratory Project, 2 (Contract research)

Nakayama, Masashi; Kobayashi, Yasushi; Matsuda, Takeshi*; Noda, Masaru*; Iriya, Keishiro*; Takeda, Nobufumi*

JAEA-Research 2009-035, 70 Pages, 2009/11

JAEA-Research-2009-035.pdf:11.27MB

In Horonobe Underground Research Center construction of underground facility began in 2005 and construction practicality test with HFSC (Highly Fly-ash contained Silica-fume Cement) is planned in a part of the gallery. Before HFSC will be placed in the gallery it is necessary to validate that HFSC has performance under the actual construction. The research results in 2007 were as follows. As corrosion behavior in HFSC, reinforced concrete specimen with HFSC 226 have been exposed to off-shore condition at in saline water and splashed zone and analyzed corrosion rate and chloride intrusion, and they were summarized. Service life time of HFSC reinforced concrete was assessed more than 50 years until cracking due to corrosion is generated. pH and components of solid and liquid phase which were made in 2002, and stored in water were analyzed. And cement paste of shotcrete which are made in 2006 were also analyzed. In this pH of shotcrete is lower than other in situ concrete since accelerating agent may act as decreasing factor of pH. The results obtained from this ten year's study were summarized on shotcerete, in situ concrete and grouting. Based on the summery, method of quality control, such as testing method, frequency, and standards so on, were investigated.

Journal Articles

Durability evalation of steel reinforced low alkaline concrete using pozzolanic reaction based on exposure test in off-shore

Takeda, Nobufumi*; Kuwae, Hitomi*; Nakayama, Masashi; Kobayashi, Yasushi

Konkurito Kogaku Nenji Rombunshu (DVD-ROM), 31(1), p.895 - 900, 2009/07

High level radioactive waste repository will be constructed using a variety of concrete such as shotcrete, lining for rock support. It is anticipated that highly alkaline plume released from the cement hydrates could influence the long-term performance of barrier system as a result of degradation of the buffer material and rock. In order to reduce hyper alkaline, JAEA is now undertaking development of low alkaline cement (HFSC: Highly Fly ash contained Silicafume Cement). In this report, to evaluate corrosion behavior of reinforcement in HFSC, we have conducted exposure test using reinforced concrete specimens in off-shore condition for 6 years, investigated corrosion rate and permeation chloride ion in concrete. As the result, it is evaluated that the period until crack occurred is more than 30 years in case of using HFSC concrete.

Journal Articles

Prediction of crack due to corrosion of reinforcing bar in low alkali concrete

Takeda, Nobufumi*; Iriya, Keishiro*; Hitomi, Takashi*; Konishi, Kazuhiro*; Kurihara, Yuji*

Obayashigumi Gijutsu Kenkyushoho (CD-ROM), (72), 8 Pages, 2008/00

To evaluate applicability as the steel reinforced concrete of the concrete with the low alkalinity cement which contains pozzolan that has been examined to apply for high level radioactive waste disposals, concrete of 30% water-cement ratio was performed 6-year marine exposure examination, aging of their compressive strength, the intrusion width of the chloride ion and the corrosion of reinforcing bar were investigated. And based on these results, progress of corrosion of reinforcing bar and the outbreak time of reinforcing corrosion crack were predicted. As a result, the following result became clear. (1) There is no fall of the compressive strength of test pieces in 6-year marine exposure examination. (2) There is little penetration of the chloride ion in comparison with the concrete consists of ordinary Portland cement. (3) The corrosion of reinforcing bar starts for the early stage with a little quantity of chloride ion intrusion, the progress until six years is extremely small. (4) the corrosion speed of the reinforcing bar of concrete with low alkali cement in underground water including sea water were estimated as 0.30$$sim$$0.55 mg/(cm$$^{2}$$ year). In case of using this concrete to structure with 100 mm cover thickness and 22 mm reinforcing bar diameter, the outbreak time of reinforcing corrosion crack were predicted as 50$$sim$$100 years after construction.

JAEA Reports

Applicability of Low Alkalinity Cement for Construction and Alteration of Bentonite in the Cement (II) (Summary)

Iriya, Keishiro*; Fujii, Kensuke*; Tajima, Takatoshi*; Takeda, Nobufumi*; Kubo, Hiroshi*

JNC TJ8400 2003-063, 49 Pages, 2003/02

JNC-TJ8400-2003-063.pdf:2.06MB

In this study, applicability of low alkalinity cement and alteration of bentonite in the cement ere investigated.

JAEA Reports

Applicability of Low Alkalinity Cement for Construction and Alteration of Bentonite in the Cement (II)

Iriya, Keishiro*; Fujii, Kensuke*; Tajima, Takatoshi*; Takeda, Nobufumi*; Kubo, Hiroshi*

JNC TJ8400 2003-062, 110 Pages, 2003/02

JNC-TJ8400-2003-062.pdf:5.12MB

In this study, applicability of low alkalinity cement and alteration of bentonite in the cement ere investigated.

JAEA Reports

Study on construction method of concrete in the underground research laboratory (III)

Iriya, Keishiro*; Mikami, Tetsuji*; Takeda, Nobufumi*; Akiyoshi, Kenji*

JNC TJ5400 2003-002, 104 Pages, 2003/02

JNC-TJ5400-2003-002.pdf:107.42MB

The Horonobe underground research laboratory project doesn't carry on only safety assessment study but also demonstration of construction technique upon nuclear waste repositories. Low alkalinity cement is one of candidates for engineered barrier in order to prevent alteration of bentonite and rock by hyper alkaline solution. JNC has developed low alkalinity cement (HFSC) which contains a lot of fly ash, and has studied the physical and chemical properties by laboratory test.Effect on variety of quality of fly ash and monitoring corrosion of rebars in off-shore condition has been studied. In-situ test for actual use of HFSC in constructing the facility was planned. The results are summarized as below. Effects of variety of fly ash upon lower pH are relatively small by testing two type of fly ash and several fly ash content. Variety of fly ash effects properties of fresh concrete but its effect is not significant. And it little effects on mechanical behavior. However, it doesn't effect on properties of shotcrete. Although rebars corrode in HFSC in spite of no intrusion of chloride, increment of corrosion is not significant in half a year until a year. Applicability for structural members is demonstrated by loading test of tunnel concrete segments of HSFC. Pre-mixed HFSC can be supplied by mixing fly ash and silica fume in Sapporo and carry to Horonobe by cement truck.

Oral presentation

Investigations for reinforcing steel corrosion embedded in low alkaline concrete by exposure test

Kobayashi, Yasushi; Nakayama, Masashi; Takeda, Nobufumi*; Matsuda, Takeshi*

no journal, , 

no abstracts in English

Oral presentation

The In-situ experiment for verification of performance of engineered barrier system in Horonobe Underground Research Laboratory, 9; Application of low alkaline cement for concrete plug

Nakayama, Masashi; Miura, Norihiko*; Ishida, Tomoko*; Takeda, Nobufumi*; Niunoya, Sumio*; Jo, Mayumi*

no journal, , 

no abstracts in English

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