Risk communication activity which used "YUME Chisoukan" in the Horonobe Underground Research Center (FY 2024)

Hoshino, Masato; Sasaki, Yoshifumi; Horikoshi, Hidehiko*; Tani, Kosuke*

JAEA-Review 2025-047, 122 Pages, 2026/03

JAEA-Review-2025-047.pdf:3.75MB

Horonobe Underground Research Center managed by Japan Atomic Energy Agency (JAEA) is the Japan's best environment to understand the project of geological disposal of high-level radioactive waste, because there is an Underground Research Laboratory (URL) in the center besides an exhibition facility which explains the content of research conducted in the URL. In the area of the center, there is also an exhibition facility for the full-scale model of engineered barrier system of geological disposal. JAEA takes advantage of this opportunity to conduct public hearing including questionnaire research regarding the questions, anxieties and comments by the visitors for geological disposal project. This report summarizes the result of statistical analysis of 2,830 visitors from April 2024 to January 2025.

Horonobe Underground Research Laboratory Project Investigation report for the 2024 fiscal year

Nakayama, Masashi; Ishii, Eiichi; Aoyagi, Kazuhei; Hayano, Akira; Murakami, Hiroaki; Ono, Hirokazu; Takeda, Masaki; Fukatsu, Yuta; Mochizuki, Akihito; Ozaki, Yusuke; et al.

JAEA-Review 2025-042, 136 Pages, 2025/12

JAEA-Review-2025-042.pdf:12.95MB

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-cho in Hokkaido, north Japan. In the fiscal year 2024, 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 100C" 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 FY2024, we continued construction of the East Access Shaft and the Ventilation Shaft, and construction of these shafts were completed to a depth of 500 m. After the completion of the East Access Shaft, excavation of the West Access Shaft and 500 m gallery has began. As of the end of FY2024, excavation progress is as follows, the East Access Shaft and the Ventilation Shaft were 500 m depth, the West Access Shaft was 472 m depth, 500 m gallery was 112.9 m, respectively. In the Horonobe International Project (HIP), Management Board and Joint Task Meeting was held at the Horonobe URL in June 2024 to review the progress of construction of galleries and preparations of experiments. Task Meetings to review the implementation plan for in-situ testing and analysis were also held. HIP will be implemented in two phases: Phase 1 (from FY2022 to FY2024) and Phase 2 (from FY2025 to FY2028), the research results of Phase 1 were compiled in FY2024.

Horonobe Underground Research Laboratory Project Investigation Program for the Fiscal Year 2025

Nakayama, Masashi; Ishii, Eiichi; Hayano, Akira; Aoyagi, Kazuhei; Murakami, Hiroaki; Ono, Hirokazu; Takeda, Masaki; Mochizuki, Akihito; Ozaki, Yusuke; Kimura, Shun; et al.

JAEA-Review 2025-027, 80 Pages, 2025/09

JAEA-Review-2025-027.pdf:6.22MB

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 2025, we continue R&D on "Study on near-field system performance in geological environment" and "Demonstration of repository design options". 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. As for "Demonstration of repository design options", the investigation, design, and evaluation techniques are to be systemized at various scales, from the tunnel to the pit, by means of an organized set of evaluation methodologies for confinement performance at these respective scales. Preliminary borehole investigations will be conducted within a 500 m gallery, with the objectives of obtaining rock strength and rock permeability data, as well as surveying the extent of the excavation damaged zone surrounding the test tunnel via tomographic analysis. A planning study for the in-situ construction test will be conducted to investigate the construction of backfill material and watertight plugs. The volume of water inflow associated with the excavation of the 500 m gallery will be observed, and its magnitude will be compared with the range of water inflow predicted in the analysis. The test plan to determine the extent of the excavation damaged zone around the pit, which is planned to be constructed in the 500 m gallery, will be studied to determine the in-situ excavation damaged zone. In addition, the investigation and evaluation methods for the amount of water inflow from fractures and the extent of the excavation damaged zone around the pit will be organized. Concerning the construction and maintenance of the subsurface facilities, excavation of the West Access Shaft and the 500 m gallery will continue. It is anticipated that the construction of the facilities will be completed by the end of the fiscal year 2025. In addition, we continue R&D on the following three tasks in the Horonobe International Project; Task A: Solute transport experiment with model testing, Task B: Systematic integration of repository technology options, and Task C: Full-scale engineered barrier system dismantling experiment.

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 100C" 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.

Trial analysis of chemical behavior in high-level radioactive liquid waste tank at accident of evaporation to dryness by boiling of reprocessing plant

Yoshida, Kazuo; Hiyama, Mina*; Tamaki, Hitoshi

JAEA-Research 2024-007, 24 Pages, 2024/08

JAEA-Research-2024-007.pdf:2.1MB

An accident of evaporation to dryness by boiling of high-level radioactive liquid waste (HLLW) is postulated as one of the severe accidents caused by the loss of cooling function at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into the atmosphere. Accurate quantitative estimation of released Ru is one of the important issues for risk assessment of those facilities. It has been observed experimentally that volatility of RuO is suppressed by HNO generated by HNO radiolysis. The analysis of chemical reactions of NO including HNO and HNO in the waste tank is essential to simulate of these phenomena. To resolve this issue, an analytical approach has been attempted to couple dynamically two computer codes SHAWED and SCHERN. The simulation of boiling behavior in the tank is conducted with SHAWED. SCHERN simulates chemical behaviors of HNO, HNO and NO in the tank. A programmatic coupling algorithm and a trial simulation of the accident are presented in this report.

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.

Impact of MOX fuel use in light-water reactors; Long-term radiological consequences of disposal of high-level waste in a geological repository

Minari, Eriko*; Kabasawa, Satsuki; Mihara, Morihiro; Makino, Hitoshi; Asano, Hidekazu*; Nakase, Masahiko*; Takeshita, Kenji*

Journal of Nuclear Science and Technology, 60(7), p.793 - 803, 2023/07

https://doi.org/10.1080/00223131.2022.2146016

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 100C' 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.

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

Nakayama, Masashi

JAEA-Review 2021-009, 54 Pages, 2021/07

JAEA-Review-2021-009.pdf:5.02MB

The Horonobe URL Project is being pursued by the 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 2021 fiscal year (2021/2022), JAEA continue to conduct research on "Demonstration of EBS in geological environment", "Demonstration of disposal concept", and "Validation of buffer capacity of the sedimentary rock to tectonism", which are the important issues shown in the Horonobe underground research plan after 2020 fiscal year. The main studies to be conducted in 2021 fiscal year are as follows. As "Demonstration of EBS in geological environment", we will shift to the test under the condition that the influence of heating is eliminated in the full scale EBS experiment. As "Demonstration of disposal concept", as a demonstration of the closure techniques, it details the conditions under which long-term transitions in the tunnel and surrounding bedrock have a significant impact on safety assessments. And we will continue engineering scale experiment to confirm the workability and performance of plugs and laboratory tests to examine the interaction between backfilling materials and buffer materials. As "Validation of buffer capacity of the sedimentary rock to tectonism", we will analyze the results of the hydraulic disturbance test and continue to study the hydraulic disconnection of faults/fissures in the Wakkanai Formation. As an advancement of technology for investigating and evaluating areas where the flow of groundwater is extremely slow, a boring exploration will be conducted to confirm the three-dimensional distribution of the fossil seawater area.

Prediction of thermodynamic data for radium suitable for thermodynamic database for radioactive waste management using an electrostatic model and correlation with ionic radii among alkaline earth metals

Kitamura, Akira; Yoshida, Yasushi*

Journal of Radioanalytical and Nuclear Chemistry, 327(2), p.839 - 845, 2021/02

https://doi.org/10.1007/s10967-020-07527-5

Thermodynamic data for radium for radioactive waste management have been predicted using an electrostatic model and correlation with the ionic radii of the alkaline earth metals. Estimation of the standard Gibbs free energy of formation and standard molar entropy of aqueous radium species and compounds has been based on such approaches as extrapolation of the thermodynamic properties of strontium and barium, and use of a model of ion pair formation. The predicted thermodynamic data for radium have been compared with previously reported values.