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Journal Articles

Validation of ATDMs at early after the lF accident using air dose rate estimated by airborne concentration and surface deposition density

Moriguchi, Yuichi*; Sato, Yosuke*; Morino, Yu*; Goto, Daisuke*; Sekiyama, Tsuyoshi*; Terada, Hiroaki; Takigawa, Masayuki*; Tsuruta, Haruo*; Yamazawa, Hiromi*

KEK Proceedings 2021-2, p.21 - 27, 2021/12

no abstracts in English

Journal Articles

Formation process of swamp sediments of the Karako Lowland in northern Shimabara Peninsula, Western Japan

Nakanishi, Toshimichi*; Okuno, Mitsuru*; Yamasaki, Keiji*; Hong, W.*; Fujita, Natsuko; Nakamura, Toshio*; Horikawa, Yoshiyuki*; Sato, Eiichi*; Kimura, Haruo*; Tsutsumi, Hiroyuki*

Nagoya Daigaku Nendai Sokutei Kenkyu, 5, p.38 - 43, 2021/03

no abstracts in English

Journal Articles

Model intercomparison of atmospheric $$^{137}$$Cs from the Fukushima Daiichi Nuclear Power Plant accident; Simulations based on identical input data

Sato, Yosuke*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Terada, Hiroaki; Nagai, Haruyasu; Kondo, Hiroaki*; Uchida, Junya*; Goto, Daisuke*; Qu$'e$lo, D.*; et al.

Journal of Geophysical Research; Atmospheres, 123(20), p.11748 - 11765, 2018/10

 Times Cited Count:19 Percentile:80.33(Meteorology & Atmospheric Sciences)

A model intercomparison of the atmospheric dispersion of $$^{137}$$Cs emitted following the Fukushima Daiichi Nuclear Power Plant accident was conducted by 12 models to understand the behavior of $$^{137}$$Cs in the atmosphere. The same meteorological data, horizontal grid resolution, and an emission inventory were applied to all the models to focus on the model variability originating from the processes included in each model. The multi-model ensemble captured 40% of the observed $$^{137}$$Cs events, and the figure-of-merit in space for the total deposition of $$^{137}$$Cs exceeded 80. Our analyses indicated that the meteorological data were most critical for reproducing the $$^{137}$$Cs events. The results also revealed that the differences among the models were originated from the deposition and diffusion processes when the meteorological field was simulated well. However, the models with strong diffusion tended to overestimate the $$^{137}$$Cs concentrations.

JAEA Reports

Long-term immersion experiments of low alkaline cementitious materials

Seno, Yasuhiro*; Noguchi, Akira*; Nakayama, Masashi; Sugita, Yutaka; Suto, Shunkichi; Tanai, Kenji; Fujita, Tomo; Sato, Haruo*

JAEA-Technology 2016-011, 20 Pages, 2016/07

JAEA-Technology-2016-011.pdf:7.56MB

Cementitious materials are expected to be used for the construction of an underground repository for the geological disposal of radioactive wastes. Ordinary Portland Cement(OPC) would conventionally be used in the fields of civil engineering and architecture, however, OPC has the potential to generate a highly alkaline plume (pH$$>$$12.5), which will likely degrade the performance of other barriers in the repository such as the bentonite buffer and/or host rock. Low alkaline cementitious materials are therefore being developed that will mitigate the generation of a highly alkaline plume. JAEA has developed a High-volume Fly ash Silica fume Cement (HFSC) as a candidate low alkaline cementitious material. The workability of the HFSC shotcrete was confirmed by conducting In-situ full scale construction tests in the Horonobe underground research laboratory. This report summarizes the results of immersion tests to assess the long-term pH behavior of hardened HFSC cement pastes made with mix designs that are expected to be able to be used in the construction of an underground repository in Japan.

Journal Articles

Mathematical Modeling of Radioactive Contaminants in the Fukushima Environment

Kitamura, Akihiro; Kurikami, Hiroshi; Yamaguchi, Masaaki; Oda, Yoshihiro; Saito, Tatsuo; Kato, Tomoko; Niizato, Tadafumi; Iijima, Kazuki; Sato, Haruo; Yui, Mikazu; et al.

Nuclear Science and Engineering, 179(1), p.104 - 118, 2015/01

 Times Cited Count:8 Percentile:65.81(Nuclear Science & Technology)

The prediction of the distribution and fate of radioactive materials eventually deposited at surface in the Fukushima area is one of the main objectives and expected to be achieved in an efficient manner. In order to make such prediction, a number of mathematical models of radioactive contaminants, with particular attention on cesium, on the land and in rivers, lakes, and estuaries in the Fukushima area are developed. Simulation results are examined with the field investigations simultaneously implemented. The basic studies of the adsorption/absorption mechanism of cesium and soils have been performed to shed light on estimating distribution coefficient between dissolved contaminant and particulate contaminant.

JAEA Reports

Research on engineering technology in the full-scale demonstration of EBS and operation technology for HLW disposal; Research report in 2012 (Joint research)

Nakatsuka, Noboru; Sato, Haruo; Tanai, Kenji; Nakayama, Masashi; Sawada, Sumiyuki*; Asano, Hidekazu*; Saito, Masahiko*; Yoshino, Osamu*; Tsukahara, Shigeki*; Hishioka, Sosuke*; et al.

JAEA-Research 2013-034, 70 Pages, 2014/01

JAEA-Research-2013-034.pdf:9.11MB

Japan Atomic Energy Agency (JAEA) and Radioactive Waste Management Funding and Research Center (RWMC) concluded the letter of cooperation agreement on the research and development of radioactive waste disposal in April, 2005, and have been carrying out the collaboration work based on the agreement. JAEA have been carrying out the Horonobe Underground Research Laboratory (URL) Project which is intended for a sedimentary rock in the Horonobe town, Hokkaido, since 2001. In the project, geoscientific research and research and development on geological disposal technology are being promoted. Meanwhile, the government (the Agency for Natural Resources and Energy, Ministry of Economy, Trade and Industry) has been promoting construction of equipments for the full-scale demonstration of engineered barrier system and operation technology for high-level radioactive waste (HLW) disposal since 2008, to enhance public's understanding to the geological disposal of HLW, e.g. using underground facility. RWMC received an order of the project in fiscal year 2012 (2011/2012) continuing since fiscal year 2008 (2008/2009). Since topics in this project are included in the Horonobe URL Project, JAEA carried out this project as collaboration work continuing in fiscal year 2008. This report summarizes the results of engineering technology carried out in this collaboration work in fiscal year 2012. In fiscal year 2012, part of the equipments for emplacement of buffer material was produced and visualization test for water penetration in buffer material were carried out.

Journal Articles

Status of future environmental prediction system and preliminary simulation results

Kitamura, Akihiro; Machida, Masahiko; Iijima, Kazuki; Sato, Haruo

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 20(2), p.87 - 91, 2013/12

A number of mathematical models of predicting future distribution of radioactive contaminants, with particular attention on cesium, on the land and in rivers, lakes, and estuaries is developed and applied for the environments of Fukushima. For examples, a model comprises of the Universal Soil Loss Equation and the Geographical Information System is developed for predicting future distributions of soil and cesium on land and the one-dimensional river model, TODAM is provided for rivers and lakes. The iRIC/Nays2D model is used for predicting detailed distributions of soil and cesium in rivers in a two dimensional configuration and modified versions of ROMS and other models are examined for the sediment transport in estuary of ocean in a three dimensional configuration. In this article we present an outline of our current activities.

JAEA Reports

Research on engineering technology in the full-scale demonstration of EBS and operation technology for HLW disposal; Research report in 2011 (Joint research)

Nakatsuka, Noboru; Sato, Haruo; Tanai, Kenji; Sugita, Yutaka; Nakayama, Masashi; Sawada, Sumiyuki*; Niinuma, Hiroaki*; Asano, Hidekazu*; Saito, Masahiko*; Yoshino, Osamu*; et al.

JAEA-Research 2013-027, 34 Pages, 2013/11

JAEA-Research-2013-027.pdf:5.84MB

Japan Atomic Energy Agency (JAEA) and Radioactive Waste Management Funding and Research Center (RWMC) concluded the letter of cooperation agreement on the research and development of radioactive waste disposal in April, 2005, and have been carrying out the collaboration work based on the agreement. JAEA have been carrying out the Horonobe Underground Research Laboratory (URL) Project which is intended for a sedimentary rock in the Horonobe town, Hokkaido, since 2001. In the project, geoscientific research and research and development on geological disposal technology are being promoted. Meanwhile, the government (the Agency for Natural Resources and Energy, Ministry of Economy, Trade and Industry) has been promoting construction of equipments for the full-scale demonstration of engineered barrier system and operation technology for high-level radioactive waste (HLW) disposal since 2008, to enhance public's understanding to the geological disposal of HLW, e.g. using underground facility. RWMC received an order of the project in fiscal year 2010 (2010/2011) continuing since fiscal year 2008 (2008/2009). Since topics in this project are included in the Horonobe URL Project, JAEA carried out this project as collaboration work continuing in fiscal year 2008. This report summarizes the results of engineering technology carried out in this collaboration work in fiscal year 2011. In fiscal year 2011, part of the equipments for emplacement of buffer material was produced and visualization test for water penetration in buffer material were carried out.

JAEA Reports

Research on engineering technology in the full-scale demonstration of EBS and operation technology for HLW disposal; Research report in 2010 (Joint research)

Nakatsuka, Noboru; Hatanaka, Koichiro; Sato, Haruo; Sugita, Yutaka; Nakayama, Masashi; Asano, Hidekazu*; Saito, Masahiko*; Suyama, Yasuhiro*; Hayashi, Hidero*; Honda, Yuko*; et al.

JAEA-Research 2013-026, 57 Pages, 2013/11

JAEA-Research-2013-026.pdf:7.48MB

JAEA and RWMC concluded the letter of cooperation agreement on the research and development of radioactive waste disposal in April, 2005, and have been carrying out the collaboration work described above based on the agreement. JAEA have been carrying out the Horonobe URL Project which is intended for a sedimentary rock in the Horonobe town, Hokkaido, since 2001. In the project, geoscientific research and research and development on geological disposal technology are being promoted. Meanwhile, the government (the Agency for Natural Resources and Energy, Ministry of Economy, Trade and Industry) has been promoting construction of equipments for the full-scale demonstration of engineered barrier system and operation technology for high-level radioactive waste (HLW) disposal since 2008, to enhance public's understanding to the geological disposal of HLW, using underground facility, etc. RWMC received an order of the project in fiscal year 2010 continuing since fiscal year 2008. Since topics in this project are included in the Horonobe URL Project, JAEA carried out this project as collaboration work continuing in FY 2008. This report summarizes the results of engineering technology carried out in this collaboration work in fiscal year 2010. In fiscal year 2010, part of the equipments for emplacement of buffer material was produced and a house for the equipments and apparatus was opened in the adjoining land of Public Information House of JAEA Horonobe.

Journal Articles

Computational modeling of radioactive contaminants in the Fukushima environment

Kitamura, Akihiro; Machida, Masahiko; Sato, Haruo; Nakayama, Shinichi; Yui, Mikazu

Transactions of the American Nuclear Society, 109(1), p.156 - 157, 2013/11

Computational modeling and simulating team of Fukushima Environmental Safety Center, Japan Atomic Energy Agency has been started to develop a number of mathematical models of radioactive contaminants on the land and rivers, lakes, and estuaries in Fukushima, as well as the basic studies of adsorption/absorption mechanism of Cs and soils. These predictions will be utilized for the dose assessment from the environmental contamination and the proposal of countermeasures to dispersion of contaminant. In this presentation we describe the outline of our current activities.

Journal Articles

Investigation and research on depth distribution in soil of radionuclides released by the TEPCO Fukushima Dai-ichi Nuclear Power Plant accident

Sato, Haruo; Niizato, Tadafumi; Amano, Kenji; Tanaka, Shingo; Aoki, Kazuhiro

Materials Research Society Symposium Proceedings, Vol.1518, p.277 - 282, 2013/10

The accident of the TEPCO Fukushima Dai-ichi Nuclear Power Plant occurred by the 2011 off the Pacific coast of Tohoku Earthquake on 11 March, 2011. It is estimated that 1.2-1.5$$times$$10$$^{16}$$ Bq for $$^{137}$$Cs and 1.5-1.6$$times$$10$$^{17}$$ Bq for I-131 were released until the beginning of April and those radionuclides (RN) were deposited on soil surface and forest etc. widely around Fukushima Pref. This work was carried out as one of the investigations for making the distribution maps of radiation dose rate and soil contaminated by RNs which the MEXT promotes. The Geoslicer investigation on the depth distribution of RNs in soil was carried out after 3 months from the accident. The investigation was conducted at 11 locations in Nihonmatsu City, Kawamata Town and Namie Town, and soil samples of depth 50 cm to 1 m were taken. Both of $$^{134}$$Cs and $$^{137}$$Cs were detected in all investigated locations, and $$^{rm 129m}$$Te and $$^{rm 110m}$$Ag were detected only in areas where radiation dose rates are high. At many locations investigated, radiocaesium more than 99% distributed within a depth of 10 cm in soil in the surface layer. On the other hand, RNs tended to distribute to deeper part in soil at locations that are supposed to have been used as farmland than in soil in the surface layer, and radiocaesium more than 99% in soil at locations that are supposed to have been used as farmland also distributed within a depth of around 14 cm. The apparent diffusion coefficients of RNs derived from penetration profiles near the surface layer showed a tendency to be higher in soil at locations that are supposed to have been used as farmland than in soil in the surface layer. The distribution coefficients by a batch method were also obtained for Cs and I, and the relationship between D$$_{rm a}$$ and K$$_{rm d}$$ was discussed.

Journal Articles

A Study on the transport of radiocaesium in the environment of Fukushima

Sato, Haruo

Kankyo Kanri, 49(9), p.15 - 25, 2013/09

The accident at the TEPCO Fukushima Dai-ichi Nuclear Power Plant in March 2011, led to the release of volatile radionuclides which were deposited on the surrounding environment (soils, forests, residential land, etc.) around the Fukushima Pref. Radiocaesium is now the main contributor to radiological dose because I-131, of which half-life is as short as about 8 days, disappeared. While a decontamination activity got into stride since the act on Special Measures Concerning the Handling of Radioactive Pollution, came fully into force on January 1, 2012, any forest bodies sharing about 70 % of the total areas have a chance of decontaminating. Therefore, forests in addition to much contaminated rivers and dams are still the source of radiocaesium, which is possible to gradually move to downstream areas. Evaluation in the change of radiation dose accompanying movement and re-distribution of radiocaesium and evaluation of re-contamination are indispensable when considering the future in judgment of a resident return and the reproduction of the local industries, etc. JAEA has been carrying out a research project entitled the "Long-Term Assessment of Transport of Radioactive Contaminant in the Environment of Fukushima (F-TRACE Project)", which is concerned re-distribution accompanying radiocaesium transport in the environment of Fukushima and the long-term assessment of radiation dose, since November 2012. This report provides an overview and status of the F-TRACE Project.

Journal Articles

Study on long-term leaching behavior of low alkaline cement

Hitomi, Takashi*; Iriya, Keishiro*; Nakayama, Masashi; Sato, Haruo

Proceedings of 3rd International Conference on Sustainable Construction Materials & Technologies (SCMT-3) (Internet), p.e0179_1 - e0179_9, 2013/08

Leaching procedure is studied on Low alkaline cement in which pozzolanic reaction is used for decreasing pH of pore water of cement hydrate to avoid influence on rock and other materials. Leached depth of Low alkaline cement (HFSC) by the immersion examination with Horonobe simulated ground was smaller than depth of ion-exchanged water. Water exchanging is smaller than that of Ordinary Poltland Cement (OPC) with the same water binder ratio, since soluble Portlandite was not produced and dissoluble Calcium Silicate components were mainly produced. Although simulated groundwater in Horonobe URL was used for immersion examination, the low alkaline cement hydrates is more durable for leaching degradation than OPC. For all cements, groundwater showed tendency of accelerate leaching compared to ion exchanged water. This study shows that HFSC has higher durability for leaching degradation to groundwater than OPC.

Journal Articles

Application of the small OSL elements to the ring type dosemeter

Miyauchi, Hideaki; Yoshitomi, Hiroshi; Sato, Yoshitaka; Takahashi, Fumiaki; Tachibana, Haruo; Kobayashi, Ikuo*; Suzuki, Akifumi*

Nihon Hoshasen Anzen Kanri Gakkai-Shi, 12(1), p.41 - 45, 2013/07

In the Japan Atomic Energy Agency (JAEA), exposures to fingertips can be significant in radiological decontamination at the facilities with mixture fields of beta and $$gamma$$ (X) rays. The radiation doses to fingertips have been measured by ring type dosemeters equipped with thermoluminescence dosemeters (TLD) in JAEA. We applied small Optically Stimulated Luminescence (OSL) elements to the ring type dosemeter, which has the advantages in the use for long term and repeating in dose measurements comparing to the TLDs. In this report, we introduce the outline and the dose evaluation method of the new ring type dosimeter which we applied.

JAEA Reports

Study on applicability of low alkaline cement in Horonobe Underground Research Laboratory Project; In-situ experiment at 250m gallery

Nakayama, Masashi; Sawada, Sumiyuki; Sato, Haruo; Sugita, Yutaka

JAEA-Research 2012-023, 65 Pages, 2012/08

JAEA-Research-2012-023.pdf:13.17MB

In Japan, any high-level radioactive waste repository is to be constructed at over 300m depth below surface. Tunnel support is used for safety during the construction and operation, and shotcrete and concrete lining are used as the tunnel support. Concrete is a composite material comprised of aggregate, cement and various additives. Low alkaline cement has been developed for the long term stability of the barrier systems whose performance could be negatively affected by highly alkaline conditions arising due to cement used in a repository. Japan Atomic Energy Agency (JAEA) has developed a low alkaline cement, named as HFSC (Highly fly-ash contained silicafume cement), containing over 60wt% of silica-fume (SF) and coal ash (FA). JAEA is presently constructing an underground research laboratory (URL) at Horonobe for research and development in the geosciences and repository engineering technology. HFSC was used experimentally as the shotcrete material in construction of part of the 140m deep gallery in Horonobe URL in 2010. The objective of this experiment was to assess the performance of HFSC shotcrete in terms of mechanics, workability, durability, and so on. HFSC used in this experiment is composed of 40wt% OPC (Ordinary Portland Cement), 20wt% SF, and 40wt% FA. This composition was determined based on mechanical testing of various mixes of the above components. Because of the low OPC content, the strength of HFSC tends to be lower than that of OPC in normal concrete. The total length of tunnel constructed using HFSC shotcrete is about 53m. The workability of HFSC shotcrete was confirmed by this experimental construction. In this report, we present detailed results of the ${it in-situ}$ construction test.

Journal Articles

Status of the Horonobe Underground Research Laboratory Project, Hokkaido, Japan, and future plan

Sato, Haruo; Sugita, Yutaka; Nakayama, Masashi

Proceedings of 19th International Conference on Nuclear Engineering (ICONE-19) (CD-ROM), 10 Pages, 2011/10

The Horonobe Underground Research Laboratory (URL) project has been being pursued for a sedimentary rock and saline groundwater in the Horonobe town, Hokkaido, Japan, as an off-site URL, since 2001. This project, extended over a period of about 20 years as a whole, has been being advanced divided into 3 phases (surface-based investigation phase (Phase I), construction phase (Phase II) and operation phase (Phase III)). Phase I was completed in March, 2006 and Phase II started in November, 2005. The URL consists of the Ventilation shaft, the East and the West access shaft and horizontal drifts of 140m, 250m, 350m and 500m in depth. Up to date, the Ventilation shaft and the East access shaft were excavated up to 250m in depth and the 140m depth gallery was completed. So far, experiments and investigations for the geological environment and engineering technology such as measurements for EDZ/EdZ, cross-hole hydraulic tests, initial rock stress measurements, construction test of shotcrete by low alkaline cement, etc. were carried out in the 140m depth gallery. Monitoring of groundwater chemistry, in-situ experiments for redox buffer capacity, etc. are presently on-going. Phase III started from the latter half of FY2010. Various in-situ investigations and experiments such as performance test of EBS, corrosion test of overpack material, backfilling test of a tunnel, etc. are planned in the underground facilities.

JAEA Reports

Horonobe Underground Research Laboratory Project; Research and development plan (H22-H26)

Iwatsuki, Teruki; Sato, Haruo; Nohara, Tsuyoshi; Tanai, Kenji; Sugita, Yutaka; Amano, Kenji; Yabuuchi, Satoshi; Oyama, Takuya; Amano, Yuki; Yokota, Hideharu; et al.

JAEA-Research 2011-009, 73 Pages, 2011/06

JAEA-Research-2011-009.pdf:4.41MB

The research and development plan in Horonobe Underground Research Laboratory are summarized according to the 2nd Midterm Plan till 2014 fiscal year of JAEA. In this midterm, galleries and the infrastructures for the research and development up to the depth of 350 m are constructed by Private Financial Initiative (PFI). Additionally Phase 3: Operation phase at the galleries begins in parallel to Phase 2: Construction phase. In these phases various research and development including collaboration with other institutes are conducted at the galleries. Generallic applicable techniques on the subject of the investigation of geological environment, facility construction in deep underground and the reliability of geological deposal are developed during the phase. The feasibility and reliance of various technologies concerning geological disposal is demonstrated by widely opening the outcome to the public in the society.

JAEA Reports

Development of ring type dosemeter using OSL elements

Miyauchi, Hideaki; Yoshitomi, Hiroshi; Sato, Yoshitaka; Tachibana, Haruo; Takahashi, Fumiaki

JAEA-Technology 2010-050, 17 Pages, 2011/03

JAEA-Technology-2010-050.pdf:1.53MB

Regulations on nuclear power state requirements for measurements of personal dose equivalent at the depth of 70 micrometers for exposures, where the maximum dose can be appeared at body parts except the torso. The hands doses have been measured with Thermal Luminescence Dosemeters in the Nuclear Science Research Institute (NSRI) in the Japan Atomic Energy Agency. In this study, we developed a new ring type dosemeter using the optically stimulated luminescence elements. We have inspected the characteristic by irradiation examinations and a Monte Carlo simulation and established dose evaluation method.

JAEA Reports

Research on engineering technology in the full-scale demonstration of EBS and operation technology for HLW disposal; Research report in 2009 (Joint research)

Nakatsuka, Noboru; Hatanaka, Koichiro; Sato, Haruo; Sugita, Yutaka; Nakayama, Masashi; Miyahara, Shigenori; Asano, Hidekazu*; Saito, Masahiko*; Suyama, Yasuhiro*; Hayashi, Hidero*; et al.

JAEA-Research 2010-060, 50 Pages, 2011/02

JAEA-Research-2010-060.pdf:6.7MB

Japan Atomic Energy Agency (JAEA) and Radioactive Waste Management Funding and Research Center (RWMC) concluded the letter of cooperation agreement on the research and development of radioactive waste disposal in April, 2005, and have been carrying out the collaboration work described above based on the agreement. JAEA have been carrying out the Horonobe Underground Research Laboratory (URL) Project which is intended for sedimentary rock in the Horonobe town, Hokkaido, since 2001. In the project, geoscientific research and research and development on geological disposal technology are being promoted. Meanwhile, the government (the Agency for Natural Resources and Energy, Ministry of Economy, Trade and Industry) has been promoting construction of equipments for the full-scale demonstration of engineered barrier system and operation technology for high-level radioactive waste (HLW) disposal since 2008, to enhance publics understanding to the geological disposal of HLW, using underground facility, etc. RWMC received an order of the project in fiscal year 2009 (2009/2010) continuing in fiscal year 2008 (2008/2009). Since topics in this project are included in the Horonobe URL Project, JAEA carried out this project as collaboration work continuing in fiscal year 2008. This report summarizes the results of engineering technology carried out in this collaboration work in fiscal year 2009. In fiscal year 2009, a part of the equipments for equipment of buffer material and visualization test apparatus for water penetration in buffer material were produced and house for the equipments and apparatus was constructed.

JAEA Reports

Study on applicability of low alkaline cement in Horonobe Underground Research Laboratory Project; In-situ experiment at 140 m gallery

Nakayama, Masashi; Sato, Haruo; Sugita, Yutaka; Noguchi, Akira

JAEA-Research 2010-055, 25 Pages, 2011/02

JAEA-Research-2010-055.pdf:2.08MB

In Japan, any high level radioactive waste repository is to be constructed at over 300 m depth below surface. Tunnel support is used for safety during the construction and operation, and shotcrete and concrete lining are used as the tunnel support. Concrete is a composite material comprised of aggregate, cement and various additives. Low alkaline cement has been developed for the long term stability of the barrier systems whose performance could be negatively affected by highly alkaline conditions arising due to cement used in a repository. JAEA has developed a low alkaline cement, named as HFSC, containing over 60wt% of SF and FA. JAEA are presently constructing an URL at Horonobe for research and development in the geosciences and repository engineering technology. HFSC was used experimentally as the shotcrete material in construction of part of the 140 m deep gallery in Horonobe URL. The objective of this experiment was to assess the performance of HFSC shotcrete in terms of mechanics, workability, durability, and so on. HFSC used in this experiment is composed of 40wt% OPC, 20wt% SF, and 40wt% FA. This composition was determined based on mechanical testing of various mixes of the above components. Because of the low OPC content, the strength of HFSC tends to be lower than that of OPC in normal concrete. The total length of tunnel using HFSC shotcrete is about 73 m and about 500 m$$^{3}$$ of HFSC was used. This experimental construction confirmed the workability of HFSC shotcrete. Although several in-situ experiments using low alkaline cement as shotcrete have been performed at a small scale, this application of HFSC at the Horonobe URL is the first full scale application of low alkaline cement in the construction of a URL in the world. In this report, we present detailed results of the in-situ construction test.

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