Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 77

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

Effective porosity in groundwater flow analysis for fractured sedimentary rocks; Case studies of the Koetoi and Wakkanai formations in Horonobe, Hokkaido, Japan

Miyakawa, Kazuya; Ishii, Eiichi; Imai, Hisashi*; Hirai, Satoru*; Ono, Hirokazu; Nakata, Kotaro*; Hasegawa, Takuma*

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 31(2), p.82 - 95, 2024/12

no abstracts in English

JAEA Reports

Horonobe Underground Research Laboratory Project Investigation Report for the 2023 Fiscal Year

Nakayama, Masashi

JAEA-Review 2024-042, 111 Pages, 2024/11

JAEA-Review-2024-042.pdf:7.83MB

The Horonobe Underground Research Laboratory (URL) Project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of relevant technologies for geological disposal of high-level radioactive waste through investigating the deep geological environment within the host sedimentary rocks at Horonobe Town in Hokkaido, north Japan. In the fiscal year 2023, we continued R&D on "Study on near-field system performance in geological environment", "Demonstration of repository design options", and "Understanding of buffering behaviour of sedimentary rock to natural perturbations". These are identified as key R&D on challenges to be tackled in the Horonobe underground research plan for the fiscal year 2020 onwards. Specifically, "full-scale engineered barrier system (EBS) performance experiment" and "solute transport experiment with model testing" were carried out as part of "Study on nearfield system performance in geological environment". "Demonstration of engineering feasibility of repository technology" and "evaluation of EBS behaviour over 100$$^{circ}$$C" were addressed for "Demonstration of repository design options". The validation of a method for assessing permeability using the Ductility Index and a method for estimating the state of in-situ ground pressure from hydraulic perturbation tests were investigated as part of the study "Understanding of buffering behaviour of sedimentary rock to natural perturbations". In FY2023, we resumed construction of the subsurface facilities, 3 new tunnels in the 350 m gallery and resumed excavation of the East Access Shaft and the Ventilation Shaft. By the end of FY2023, the 350 m gallery extension (tunnel extension 66 m) had been completed, and the depths of the East Access Shaft and Ventilation Shaft were GL-424 m and GL-393 m respectively.

Journal Articles

Biofilm-mediated interactions between plastics and radiocesium in coastal environments

Battulga, B.; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Otosaka, Shigeyoshi*; Koarashi, Jun

Environmental Science and Pollution Research, 31, p.60080 - 60092, 2024/10

A ubiquitous distribution of plastic debris has been reported in aquatic and terrestrial environments; however, the interactions between plastics and radionuclides and the radioactivity of environmental plastics remain largely unknown. Here, we characterize biofilms developing on the surface of plastic debris to explore the role of plastic-associated biofilms as an interaction medium between plastics and radiocesium ($$^{137}$$Cs) in the environment. Biofilm samples were extracted from plastics (1-50 mm in size) collected from two contrasting coastal areas in Japan. The radioactivity of plastics was estimated based on the $$^{137}$$Cs activity concentration of the biofilms and compared seasonally with surrounding environmental samples (i.e., sediment and sand). $$^{137}$$Cs traces were detected in biofilms with activity concentrations of 21-1300 Bq kg$$^{-1}$$ biofilm (dry weight), corresponding to 0.04-4.5 Bq kg$$^{-1}$$ plastic (dry weight). Our results reveal the interaction between $$^{137}$$Cs and plastics and provide evidence that organic and mineral components in biofilms are essential in $$^{137}$$Cs retention in environmental plastics.

JAEA Reports

Horonobe Underground Research Laboratory Project; Investigation program for the fiscal year 2024

Nakayama, Masashi

JAEA-Review 2024-033, 64 Pages, 2024/09

JAEA-Review-2024-033.pdf:5.15MB

The Horonobe Underground Research Laboratory Project is being pursued by the Japan Atomic Energy Agency to enhance the reliability of relevant technologies for geological disposal of high-level radioactive waste through investigating the deep geological environment within the host sedimentary rocks at Horonobe Town in Hokkaido, north Japan. In the fiscal year 2024, we continue R&D on "Study on near-field system performance in geological environment", "Demonstration of repository design options", and "Understanding of buffering behaviour of sedimentary rocks to natural perturbations". These are identified as key R&D challenges to be tackled in the Horonobe underground research plan for the fiscal year 2020 onwards. In the "Study on near-field system performance in geological environment", we continue to obtain data from the full-scale engineered barrier system performance experiment, and work on the specifics of the full-scale engineered barrier system dismantling experiment. We summarise the solute transport experiments for the excavation damaged zone and the effects of organic matter, micro-organisms and colloids, and develop the assessment methodology. We summarise the evaluation methodology using the deep Wakkanai Formation as a case study for block-scale solute transport experiments. As for "Demonstration of repository design options", we summarise the results of investigations and experiments on changes in the geological environment after tunnel excavation and closure, and summarise the applicability and technical challenges of the closure technology for boreholes excavated from tunnels. The systematic integration of technologies towards EBS emplacement, including the organisation of investigation and evaluation methods and analysis, will be promoted. Experiments to confirm the performance of the engineered barrier system under critical conditions, such as high temperatures ($$>$$100$$^{circ}$$C), continue the in-situ tests started in 2023.

Journal Articles

Evaluation of the impact of the $$^{137}$$Cs supply from rivers to coastal waters off Fukushima on the $$^{137}$$Cs behavior in seabed sediment

Ikenoue, Tsubasa; Nakanishi, Takahiro; Shimadera, Hikari*; Kawamura, Hideyuki; Kondo, Akira*

E3S Web of Conferences (Internet), 530, p.02005_1 - 02005_10, 2024/05

The accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) caused a radioactive contamination in seabed sediment. The $$^{137}$$Cs supply from rivers could be an important process for the long-term behavior of $$^{137}$$Cs in seabed sediment. In this study, a ten-year simulation of the $$^{137}$$Cs behavior in seabed sediment was conducted using an oceanic dispersion model combined with a prediction model of $$^{137}$$Cs behavior in land and river. In the waters north of FDNPP, the simulation results suggested that the $$^{137}$$Cs supply from rivers had a great impact on the concentrations in coastal sediment due to the initial low concentrations in seabed sediment and the large supply of $$^{137}$$Cs from rivers. In the waters near FDNPP and south of FDNPP, the simulation results suggested that the impact of the $$^{137}$$Cs supply on the temporal variation of $$^{137}$$Cs concentration in coastal sediment was relatively small due to the large initial adsorption from seawater. Overall, these results indicated that $$^{137}$$Cs supply from rivers had an impact on the spatiotemporal distribution of $$^{137}$$Cs concentrations in seabed sediment on a decadal time scale and the impact was especially great in the waters north of FDNPP.

JAEA Reports

Horonobe Underground Research Laboratory Project Investigation Report for the 2022 Fiscal Year

Nakayama, Masashi

JAEA-Review 2023-032, 159 Pages, 2024/02

JAEA-Review-2023-032.pdf:19.37MB

The Horonobe Underground Research Laboratory (URL) Project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of relevant technologies for geological disposal of high-level radioactive waste through investigating the deep geological environment within the host sedimentary rocks at Horonobe Town in Hokkaido, north Japan. In the fiscal year 2022, we continued R&D on "Study on near-field system performance in geological environment", "Demonstration of repository design options", and "Understanding of buffering behaviour of sedimentary rock to natural perturbations". These are identified as key R&D on challenges to be tackled in the Horonobe underground research plan for the fiscal year 2020 onwards. Specifically, "full-scale engineered barrier system (EBS) performance experiment" and "solute transport experiment with model testing" were carried out as part of "Study on near- field system performance in geological environment". "Demonstration of engineering feasibility of repository technology" and "evaluation of EBS behaviour over 100$$^{circ}$$C" were addressed for "Demonstration of repository design options". A study on "Understanding of buffering behaviour of sedimentary rock to natural perturbations" was also implemented in two areas, "evaluation of intrinsic buffering against endogenic and exogenic processes" and "development of techniques for evaluating excavation damaged zone (EDZ) self-sealing behaviour after backfilling". The Horonobe International Project (HIP) was initiated in February 2023 to promote research and development in collaboration with national and international organizations.

JAEA Reports

Horonobe Underground Research Laboratory Project; Investigation program for the 2023 fiscal year

Nakayama, Masashi

JAEA-Review 2023-019, 70 Pages, 2023/11

JAEA-Review-2023-019.pdf:6.83MB

The Horonobe Underground Research Laboratory (URL) Project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of relevant technologies for geological disposal of high-level radioactive waste through investigating the deep geological environment within the host sedimentary rocks at Horonobe Town in Hokkaido, north Japan. In the fiscal year 2023, we continue R&D on "Study on near-field system performance in geological environment", "Demonstration of repository design options", and "Understanding of buffering behaviour of sedimentary rocks to natural perturbations". These are identified as key R&D challenges to be tackled in the Horonobe underground research plan for the fiscal year 2020 onwards. In the "Study on near-field system performance in geological environment", we conduct the coupled analysis on the full-scale engineered barrier system performance experiment and test the coupled simulation code through comparison with different simulation codes in the international DECOVALEX-2023 collaboration project. Borehole investigations are also carried out for solute transport experiments in the Koetoi Formation. As for "Demonstration of repository design concept", we carry out in situ experiments and data analysis on concrete deterioration under the subsurface conditions. Geophysical surveys are also carried out around an experimental tunnel to be newly excavated at the 350m gallery and characterise the initial conditions of the excavation damaged zone. For the "Understanding of buffering behaviour of sedimentary rocks to natural perturbations", we analyse the results of the hydraulic disturbance tests conducted in previous years and understand the relationship between rock stress / stress state and fault / fracture hydraulic connectivity. Concerning the construction and maintenance of the subsurface facilities, the 350 m gallery is extended and shafts are sank to a depth of 500 m.

JAEA Reports

Development of stable solidification technique of ALPS sediment wastes by apatite ceramics (Contract research); FY2021 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tokyo Institute of Technology*

JAEA-Review 2022-076, 227 Pages, 2023/03

JAEA-Review-2022-076.pdf:9.42MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2021. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2019, this report summarizes the research results of the "Development of stable solidification technique of ALPS sediment wastes by apatite ceramics" conducted from FY2019 to FY2021. Since the final year of this proposal was FY2021, the results for three fiscal years were summarized. The present study aims to establish an apatite solidification process of radioactive sediment wastes, which were generated from the ALPS process manipulating the large amount of contaminated water from 1F. We selected the precipitation method and post stabilization for engineering-scale process. Investigation on composition, structure and elution properties of apatite and related phosphate waste forms fabricated from the simulated ALPS sediment wastes were implemented.

JAEA Reports

Data of groundwater chemistry obtained in the Horonobe Underground Research Laboratory Project (FY2022)

Miyakawa, Kazuya; Nakata, Kotaro*

JAEA-Data/Code 2022-013, 19 Pages, 2023/03

JAEA-Data-Code-2022-013.pdf:1.88MB

In the Horonobe Underground Research Laboratory (URL) project, groundwater chemistry was analyzed to investigate changes due to the excavation of the underground facility and to review geochemical models until the fiscal year 2019. From the fiscal year 2020, to proceed remaining important issues deduced from the conclusion of the investigations during the fiscal year 2015-2019, primary data such as groundwater chemistry need to be successively acquired. Here, the chemical analysis of 54 groundwater samples in 2022 from boreholes drilled in the 140 m, 250 m, 350 m gallery in the Horonobe URL, and water rings settled in three vertical shafts is presented. Analytical results include groundwater chemistry such as pH, electrical conductivity, dissolved components (Na$$^{+}$$, K$$^{+}$$, Ca$$^{2+}$$, Mg$$^{2+}$$, Li$$^{+}$$, NH$$_{4}$$$$^{+}$$, F$$^{-}$$, Cl$$^{-}$$, Br$$^{-}$$, NO$$_{3}$$$$^{-}$$, NO$$^{2}$$$$^{-}$$, PO$$_{4}$$$$^{3-}$$, SO$$_{4}$$$$^{2-}$$, Total-Mn, Total-Fe, Al, B, Sr, Ba, I, alkalinity, dissolved organic carbon, dissolved inorganic carbon, CO$$_{3}$$$$^{2-}$$, HCO$$_{3}$$$$^{-}$$, Fe$$^{2+}$$, sulfide), and $$delta$$$$^{18}$$O, $$delta$$D along with a detailed description of analytical methods.

JAEA Reports

Horonobe Underground Research Laboratory Project; Investigation program for the 2022 fiscal year

Nakayama, Masashi

JAEA-Review 2022-026, 66 Pages, 2022/11

JAEA-Review-2022-026.pdf:12.31MB

The Horonobe Underground Research Laboratory (URL) Project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of relevant disposal technologies for geological disposal of High-level Radioactive Waste through investigations of the deep geological environment within the host sedimentary rock at Horonobe Town in Hokkaido, north Japan. In fiscal year 2022, we continue to conduct research on "Study on near-field system performance in geological environment", "Demonstration of repository design options", and "Understanding of buffering behaviour of sedimentary rocks to natural perturbations", which are the important issues shown in the Horonobe underground research plan from fiscal year 2020. The main studies to be conducted in fiscal year 2022 are as follows. As "Study on near-field system performance in geological environment", we will continue to the test under the simulated condition in which the heat generation by the high-level radioactive waste has subsides in the full-scale engineered barrier system (EBS) performance experiment. We will also conduct solute transport experiment with model testing that take into account the effects of organic matter, microbes, and colloids, and initiate borehole investigation to evaluate solute transport experiments on fractures distribute in Koetoi formation. As "Demonstration of repository design concept", we will continue experiment and analysis of concrete deterioration in the underground environment as a demonstration of remote technique for emplacement and retrievable. As a demonstration of the closure techniques, laboratory tests will be continued to investigate the mechanism of bentonite runoff behaviour, which could be a factor in changing the performance of backfill material, and to expand data on swelling and deformation behaviour. In addition, in-situ borehole closure tests will be conducted to evaluate the applicability of the closure method. As "Understanding of buffering behaviour of

JAEA Reports

Horonobe Underground Research Laboratory Project; Investigation report for the 2021 fiscal year

Nakayama, Masashi

JAEA-Review 2022-025, 164 Pages, 2022/11

JAEA-Review-2022-025.pdf:12.25MB

The Horonobe Underground Research Laboratory (URL) Project is being pursued by the Japan Atomic Energy Agency (JAEA). The main aim of this project is to enhance the reliability of relevant disposal technologies for geological disposal of high-level radioactive waste through a comprehensive research and development (R&D) program in the deep geological environment within the host sedimentary rock at Horonobe in Hokkaido, north Japan. In fiscal year 2021, we continued R&D on three important issues specified in the "Horonobe Underground Research Plan from Fiscal Year 2020", which involve "Study on near-field system performance in geological environment", "Demonstration of repository design options", and "Understanding of buffering behaviour of sedimentary rock to natural perturbations". Specifically, "full-scale engineered barrier system (EBS) performance experiment" and "solute transport experiment with model testing" were carried out as part of "Study on near-field system performance in geological environment". "Demonstration of engineering feasibility of repository technology" and "evaluation of EBS behaviour over 100$$^{circ}$$C' were addressed for "Demonstration of repository design options". A study on "Understanding of buffering behaviour of sedimentary rock to natural perturbations" was also implemented in two areas, "evaluation of intrinsic buffering against endogenic and exogenic processes" and "development of techniques for evaluating excavation damaged zone (EDZ) self-sealing behaviour after backfilling". The results of the R&D, along with those obtained in other departments of JAEA, will reinforce the technical basis for both repository implementation and safety regulation. For the sake of this, we will steadily proceed with this project in collaboration with relevant organizations and universities both domestically and internationally and also widely publish the plans and results of the R&D to ensure their transparency and technical reliability.

Journal Articles

${it Neocalanus cristatus}$ (Copepoda) from a deep sediment-trap; Abundance and implications for ecological and biogeochemical studies

Ikenoue, Takahito*; Otosaka, Shigeyoshi*; Honda, Makio*; Kitamura, Minoru*; Mino, Yoshihisa*; Narita, Hisashi*; Kobayashi, Takuya

Frontiers in Marine Science (Internet), 9, p.884320_1 - 884320_11, 2022/05

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

We studied seasonal variations of the mesozooplankton swimmer community collected by a sediment trap moored at 873 m in the Kuroshio & Oyashio Transition region off the east coast of Japan from 5 August 2011 to 23 June 2013. The total flux of mesozooplankton swimmers varied between 0 and 11.1 individuals m-2 d-1, with a mean of 3.1 individuals m-2 d-1 during the sampling period. Among the Copepoda, Neocalanus cristatus was the most dominant taxon. The species composition of the swimmers closely reflected the mid-depth mesozooplankton of the Oyashio region. The fluxes of Neocalanus species reflected ontogenetic vertical migration, but may have been overestimates of active fluxes if they included dormant individuals that accidentally entered the sediment trap.

JAEA Reports

Design details of bottom shape for the 3rd glass melter in TVF

Asahi, Yoshimitsu; Shimamura, Keisuke*; Kobayashi, Hidekazu; Kodaka, Akira

JAEA-Technology 2021-026, 50 Pages, 2022/03

JAEA-Technology-2021-026.pdf:6.29MB

In Tokai Reprocessing Plant, the highly active liquid waste derived from a spent fuel reprocessing is vitrified with a Liquid-Fed Ceramic Melter (LFCM) embedded in Tokai Vitrification Facility (TVF). For an LFCM, the viscosity of melted glass is increased by the deposition of oxidation products of platinum group elements (PGE) and the PGE-containing glass tends to settle to the melter's bottom basin even after draining glass out. Removal of the PGE-containing glass is needed to avoid the Joule heating current from being affected by the glass, it requires time-consuming work to remove. For the early accomplishment of vitrifying the waste, Japan Atomic Energy Agency is planning to replace the current melter with the new one in which the amount of PGE sediments would be reduced. In the past design activities for the next melter, several kinds of shapes in regard to the furnace bottom and the strainer were drawn. Among these designs, the one in which the discharge ratio of PGE-containing glass would be as much as or greater than the current melter and which be able to perform similar operational sequences done in the current melter is selected here. Firstly, an operational sequence to produce one canister of vitrified waste is simulated for three melter designs with a furnace bottom shape, using 3D thermal-hydraulic calculations. The computed temperature distribution and its changes are compared among the candidate structures. After discussions about the technical and structural feasibilities of each design, a cone shape with a 45$$^{circ}$$ slope was selected as the bottom shape of the next melter. Secondly, five strainer designs that fit the bottom shape above mentioned are drawn. For each design, the fluid drag and the discharge ratio of relatively high viscosity fluid resting near the bottom are estimated, using steady or unsteady CFD simulation. By draining silicone oil from acrylic furnace models, it was confirmed experimentally that there are no vortices

JAEA Reports

Development of stable solidification technique of ALPS sediment wastes by apatite ceramics (Contract research); FY2020 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tokyo Institute of Technology*

JAEA-Review 2021-077, 217 Pages, 2022/03

JAEA-Review-2021-077.pdf:12.34MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2020. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2019, this report summarizes the research results of the "Development of stable solidification technique of ALPS sediment wastes by apatite ceramics" conducted in FY2020. The present study aims to establish an apatite solidification process of radioactive sediment wastes, which were generated from the ALPS process manipulating the large amount of contaminated water from Fukushima Daiichi Nuclear Power Station. In FY2020, the synthetic scheme and elemental composition were updated to precipitation method to accept the actual ALPS sediment wastes in engineering scale. The synthesis of apatite or phosphate wastes and their molding conditions were surveyed, and the relations among elemental compositions, structures and chemical properties were clarified.

JAEA Reports

Horonobe Underground Research Laboratory Project; Investigation report for the 2020 fiscal year

Nakayama, Masashi

JAEA-Review 2021-053, 133 Pages, 2022/02

JAEA-Review-2021-053.pdf:14.45MB

The Horonobe Underground Research Laboratory (URL) Project is being pursued by the Japan Atomic Energy Agency (JAEA). The main aim of this project is to enhance the reliability of relevant disposal technologies for geological disposal of high-level radioactive waste through a comprehensive research and development (R&D) program in the deep geological environment within the host sedimentary rock at Horonobe in Hokkaido, north Japan. In fiscal year 2020, JAEA continued R&D on three important issues specified in the "Horonobe Underground Research Plan from Fiscal Year 2020", which involve "Study on nearfield system performance in geological environment", "Demonstration of repository design options", and "Understanding of buffering behavior of sedimentary rock to natural perturbations". Specifically, 'full scale engineered barrier system (EBS) experiment' and 'solute transport experiment' were carried out as part of "Study on near-field system performance in geological environment". 'Development and testing of EBS emplacement / retrieval and tunnel closure technologies' and 'evaluation of EBS behavior over 100$$^{circ}$$C' were addressed for "Demonstration of repository design options". A study on "Understanding of buffering behavior of sedimentary rock to natural perturbations" was also implemented in two areas, 'evaluation of hydromechanical responses of faults to water pressure changes' and 'development of techniques for evaluating self-sealing behavior of an excavation damaged zone after backfilling'. The results of the R&D, along with those obtained in other departments of JAEA, will reinforce the technical basis for both repository implementation and safety regulation. For the sake of this, JAEA will steadily proceed with this project in collaboration with relevant organizations and universities both domestically and internationally and also widely publish the plans and results of the R&D to ensure their transparency and technical reliability.

Journal Articles

Numerical reproduction of dissolved U concentrations in a PO$$_{4}$$-treated column study of Hanford 300 area sediment using a simple ion exchange and immobile domain model

Saito, Tatsuo; Sato, Kazuhiko; Yamazawa, Hiromi*

Journal of Environmental Radioactivity, 237, p.106708_1 - 106708_9, 2021/10

 Times Cited Count:2 Percentile:7.62(Environmental Sciences)

We succeeded at numerical reproduction of dissolved U concentrations from column experiments with PO$$_{4}$$-treated Hanford 300 Area sediment. The time-series curves of dissolved U concentrations under various Darcy flow rate conditions were reproduced by the numerical model in the present study through optimization of the following parameters:(i) the mass of U in mobile domain (on surface soil connected to the stream) and the rest of the total U left as precipitation in immobile domain (isolated in deep soil);(ii) the mixing ratio between immobile and mobile domains, to fit the final recovering curve of concentration; and (iii) the cation exchange capacity (CEC$$_{Zp}$$) and equilibrium constant (k$$_{Zp}$$) of the exchange reaction of UO$$_{2}$$$$^{2+}$$ and H$$^{+}$$ on simulated soil surface ($$Zp$$), to fit the transient equilibrium concentration, forming the bed of the bathtub curve.

JAEA Reports

Development of stable solidification technique of ALPS sediment wastes by apatite ceramics (Contract research); FY2019 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tokyo Institute of Technology*

JAEA-Review 2020-060, 116 Pages, 2021/02

JAEA-Review-2020-060.pdf:16.98MB

JAEA/CLADS had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project in FY2019. Among the adopted proposals in FY2019, this report summarizes the research results of the "Development of Stable Solidification Technique of ALPS Sediment Wastes by Apatite Ceramics" conducted in FY2019.

JAEA Reports

Horonobe Underground Research Laboratory Project; Investigation report for the 2019 fiscal year

Nakayama, Masashi; Saiga, Atsushi

JAEA-Review 2020-042, 116 Pages, 2021/01

JAEA-Review-2020-042.pdf:10.33MB

The Horonobe Underground Research Laboratory Project will be conducted in three phases, namely "Phase 1: Surface-based investigations", "Phase 2: Construction Phase" (investigations during construction of the underground facilities) and "Phase 3: Operation phase" (research in the underground facilities). This report summarizes the results of the investigations for the 2019 fiscal year (2019/2020). The investigations, which are composed of "Geoscientific research" and "R and D on geological disposal technology", were carried out according to "Horonobe Underground Research Laboratory Project Investigation Program for the 2019 fiscal year". The results of these investigations, along with the results which were obtained in other departments of Japan Atomic Energy Agency (JAEA), are properly offered to the implementations and the safety regulations. For the sake of this, JAEA has proceeded with the project in collaboration with experts from domestic and overseas research organizations.

Journal Articles

Impact of soil erosion potential uncertainties on numerical simulations of the environmental fate of radiocesium in the Abukuma River basin

Ikenoue, Tsubasa; Shimadera, Hikari*; Kondo, Akira*

Journal of Environmental Radioactivity, 225, p.106452_1 - 106452_12, 2020/12

 Times Cited Count:5 Percentile:18.37(Environmental Sciences)

This study focused on the uncertainty of the factors of the Universal Soil Loss Equation (USLE) and evaluated its impacts on the environmental fate of $$^{137}$$Cs simulated by a radiocesium transport model in the Abukuma River basin. The USLE has five physically meaningful factors: the rainfall and runoff factor (R), soil erodibility factor (K), topographic factor (LS), cover and management factor (C), and support practice factor (P). The simulation results showed total suspended sediment and $$^{137}$$Cs outflows were the most sensitive to C and P among the all factors. Therefore, land cover and soil erosion prevention act have the great impact on outflow of suspended sediment and $$^{137}$$Cs. Focusing on land use, the outflow rates of $$^{137}$$Cs from the forest areas, croplands, and undisturbed paddy fields were large. This study indicates that land use, especially forest areas, croplands, and undisturbed paddy fields, has a significant impact on the environmental fate of $$^{137}$$Cs.

JAEA Reports

Long term monitoring and evaluation of the excavation damaged zone induced around the wall of the shaft applying optical fiber sensor (Cooperative research)

Hata, Koji*; Niunoya, Sumio*; Uyama, Masao*; Nakaoka, Kenichi*; Fukaya, Masaaki*; Aoyagi, Kazuhei; Sakurai, Akitaka; Tanai, Kenji

JAEA-Research 2020-010, 142 Pages, 2020/11

JAEA-Research-2020-010.pdf:13.74MB
JAEA-Research-2020-010-appendix(DVD-ROM).zip:149.9MB

In the geological disposal study of high-level radioactive waste, it is suggested that the excavation damaged zone (EDZ) which is created around a tunnel by the excavation will be possible to be one of the critical path of radionuclides. Especially, the progress of cracks in and around the EDZ with time affects the safety assessment of geological disposal and it is important to understand the hydraulic change due to the progress of cracks in and around EDZ. In this collaborative research, monitoring tools made by Obayashi Corporation were installed at a total of 9 locations in the three boreholes near the depth of 370 m of East Shaft at the Horonobe Underground Research Laboratory constructed in the Neogene sedimentary rock. The monitoring tool consists of one set of "optical AE sensor" for measuring of the mechanical rock mass behavior and "optical pore water pressure sensor and optical temperature sensor" for measuring of groundwater behavior. This tool was made for the purpose of selecting and analyzing of AE signal waveforms due to rock fracture during and after excavation of the target deep shaft. As a result of analyzing various measurement data including AE signal waveforms, it is able to understand the information on short-term or long-term progress of cracks in and around EDZ during and after excavation in the deep shaft. In the future, it will be possible to carry out a study that contributes to the long-term stability evaluation of EDZ in sedimentary rocks in the deep part of the Horonobe Underground Research Laboratory by evaluation based on these analytical data.

77 (Records 1-20 displayed on this page)