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 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 Horonobe International Project (HIP) was initiated in February 2023 to promote research and development in collaboration with national and international organizations.

Development of hydrogen oxidation reaction catalysts to overcome CO poisoning and elucidation of reaction mechanism

Inagawa, Kohei*; Matsumura, Daiju; Taniguchi, Masashi*; Uegaki, Shinya*; Nakayama, Tomohito*; Urano, Junnosuke*; Aotani, Takuro*; Tanaka, Hirohisa*

Journal of Physical Chemistry C, 127(24), p.11542 - 11549, 2023/06

https://doi.org/10.1021/acs.jpcc.3c02237

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.

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

Nakayama, Masashi; Saiga, Atsushi

JAEA-Review 2020-022, 34 Pages, 2020/11

JAEA-Review-2020-022.pdf:3.99MB

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. The investigations 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). According to the research plan described in the 3rd Mid- and Long- term Plan of JAEA, "Demonstration of EBS in geological environment", "Demonstration of disposal concept", and "Validation of buffer capacity of the sedimentary rock to tectonism" are important issues of the Horonobe URL Project, and schedule of future research and backfill plans of the URL will be decided by the end of 2019 Fiscal Year. JAEA summarizes the research and development activities of the important issues carried out during the 3rd Mid- and Long-term Plan, and set out three important issues after 2020 fiscal year. After consultation with Hokkaido and Horonobe town, JAEA formulated the Horonobe underground research plan after 2020 fiscal year within the 3rd and 4th Mid- and Long-term Plan. This report summarizes the investigation program for the 2020 fiscal year (2020/2021).

Devil's staircase transition of the electronic structures in CeSb

Kuroda, Kenta*; Arai, Yosuke*; Rezaei, N.*; Kunisada, So*; Sakuragi, Shunsuke*; Alaei, M.*; Kinoshita, Yuto*; Bareille, C.*; Noguchi, Ryo*; Nakayama, Mitsuhiro*; et al.

Nature Communications (Internet), 11, p.2888_1 - 2888_9, 2020/06

https://doi.org/10.1038/s41467-020-16707-6

Preliminary study on radiation effects of monitoring equipment

Nakayama, Masashi; Tanai, Kenji

JAEA-Review 2019-032, 32 Pages, 2020/02

JAEA-Review-2019-032.pdf:1.84MB

There are various types of monitoring in the geological disposal of high-level radioactive waste, such as monitoring for confirmation of construction quality and the status of engineered barrier, and monitoring to help manage construction, operation and closure activities, etc. Among these monitoring methods, monitoring related to the confirmation of the state of engineered barrier has been studied in international joint research on monitoring concepts and specific methods. Since monitoring equipment is affected by temperature, humidity, pressure, radiation, water quality, etc., it is important to consider geological environmental conditions and radiation effects. This report compares the radiation resistance of the materials used in the monitoring equipment with the absorbed dose in the buffer material obtained by analysis, and qualitatively examines the effects of radiation on the monitoring equipment. As a result of the examination, it was estimated that the dose did not affect the monitoring equipment. However, it is necessary to verify the possibility of reliable data acquisition by irradiation tests for monitoring devices with built-in electronic components.

Collection of measurement data from in-situ experiment for performance confirmation of engineered barrier system at Horonobe Underground Research Laboratory (until March, 2018)

Nakayama, Masashi; Ono, Hirokazu; Nakayama, Mariko*; Kobayashi, Masato*

JAEA-Data/Code 2019-003, 57 Pages, 2019/03

JAEA-Data-Code-2019-003.pdf:18.12MB
JAEA-Data-Code-2019-003-appendix(CD-ROM).zip:99.74MB

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, northern Hokkaido. The URL Project consists of two major research areas, Geoscientific Research and Research and Development on Geological Disposal Technologies, and proceeds in 3 overlapping phases, Phase I: Surface-based investigations, Phase II: Investigations during tunnel excavation and Phase III: Investigations in the URL, over a period of around 20 years. Phase III investigation was started in 2010 FY. The in-situ experiment for performance confirmation of engineered barrier system had been prepared from 2013 to 2014 FY at GL-350 m gallery, and heating by electric heater in simulated overpack had started in January, 2015. One of objectives of the 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 summarizes the measurement data acquired from the experiment from December, 2014 to March, 2018. The summarized data of the EBS experiment will be published periodically.

Evolution of the excavation damaged zone around a modelled disposal pit; Case study at the Horonobe Underground Research Laboratory, Japan

Aoyagi, Kazuhei; Miyara, Nobukatsu; Ishii, Eiichi; Nakayama, Masashi; Kimura, Shun

Proceedings of 13th SEGJ International Symposium (USB Flash Drive), 5 Pages, 2018/11

The construction of underground facilities induces fractures in the rock mass around the underground voids due to the resultant stress redistribution. This has particular implications for high-level radioactive waste (HLW) disposal projects, where fracture development creates an excavation damaged zone (EDZ) that increases the hydraulic conductivity of the surrounding rock mass and can provide a pathway for the migration of radionuclides from the storage facilities. It is therefore important to understand the long-term evolution of the EDZ and perform a comprehensive HLW disposal risk assessment. An in situ engineered barrier system experiment was conducted in the 350 m gallery at the Horonobe Underground Research Laboratory, Japan, to observe the near-field coupled thermo-hydro-mechanical-chemical (THMC) process in situ and validate coupled THMC models. Here we investigate the evolution of the EDZ around the gallery and model a test pit that was excavated below the floor of the gallery using a series of seismic tomography surveys. There was a significant decrease in the seismic velocity field around the test pit due to its excavation, which became slightly more pronounced over time after the excavation. These seismic results, coupled with hydraulic tests and pore pressure measurements around the pit, indicate that fracture development and the decrease in saturation around the test pit resulted in a decrease in the seismic velocity field after the excavation of the test pit. Furthermore, the increase in saturation around the test pit is a key reason for the increase in the seismic velocity field after the heater test.

The In-situ experiment for overpack corrosion at Horonobe Underground Research Laboratory; Production and setting simulated overpack, buffer material blocks and heater

Nakayama, Masashi

JAEA-Technology 2018-006, 43 Pages, 2018/08

JAEA-Technology-2018-006.pdf:5.32MB
JAEA-Technology-2018-006-appendix(CD-ROM).zip:29.19MB

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 proceeds in 3 overlapping phases, "Phase I: Surface-based investigations", "Phase II: Investigations during tunnel excavation" and "Phase III: Investigations in the underground facilities", over a period of around 20 years. The OP corrosion test was prepared from 2013 FY at Niche No.3, and heating by electric heater in simulated overpack started in November, 2014. The objective of the test is acquiring data concerned with corrosion of carbon steel OP. These data will be used in order to confirm the performance of engineered barrier system. In the OP corrosion test, the diameter of simulated OP and buffer material are 100 mm and 300 mm, respectively. Concrete support using low alkaline cement was used in order to investigate the effect of cementitious materials to OP corrosion behavior. We will measure corrosion potential of carbon steel, natural potential, pH in buffer material for several years. In this report, we describe how to make simulated OP and buffer material blocks, and set sensors, and so on.