Annual report for research on geosphere stability for long-term isolation of radioactive waste in fiscal year 2022

Niwa, Masakazu; Shimada, Koji; Sueoka, Shigeru; Ishihara, Takanori; Ogawa, Hiroki; Hakoiwa, Hiroaki; Watanabe, Tsuyoshi; Nishiyama, Nariaki; Yokoyama, Tatsunori; Ogata, Manabu; et al.

JAEA-Research 2023-005, 78 Pages, 2023/10

JAEA-Research-2023-005.pdf:6.51MB

This annual report documents the progress of research and development (R&D) in the 1st fiscal year of the Japan Atomic Energy Agency 4th Medium- and Long-term Plan (fiscal years 2022-2028) to provide the scientific base for assessing geosphere stability for long-term isolation of high-level radioactive waste. The plan framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques. The current status of R&D activities with previous scientific and technological progress is summarized.

Improving the safety of the high temperature gas-cooled reactor "HTTR" based on Japan's new regulatory requirements

Hamamoto, Shimpei; Shimizu, Atsushi; Inoi, Hiroyuki; Tochio, Daisuke; Homma, Fumitaka; Sawahata, Hiroaki; Sekita, Kenji; Watanabe, Shuji; Furusawa, Takayuki; Iigaki, Kazuhiko; et al.

Nuclear Engineering and Design, 388, p.111642_1 - 111642_11, 2022/03

https://doi.org/10.1016/j.nucengdes.2021.111642

Following the Fukushima Daiichi Nuclear Power Plant accident in 2011, the Japan Atomic Energy Agency adapted High-Temperature engineering Test Reactor (HTTR) to meet the new regulatory requirements that began in December 2013. The safety and seismic classifications of the existing structures, systems, and components were discussed to reflect insights regarding High Temperature Gas-cooled Reactors (HTGRs) that were acquired through various HTTR safety tests. Structures, systems, and components that are subject to protection have been defined, and countermeasures to manage internal and external hazards that affect safety functions have been strengthened. Additionally, measures are in place to control accidents that may cause large amounts of radioactive material to be released, as a beyond design based accident. The Nuclear Regulatory Commission rigorously and appropriately reviewed this approach for compliance with the new regulatory requirements. After nine amendments, the application to modify the HTTR's installation license that was submitted in November 2014 was approved in June 2020. This response shows that facilities can reasonably be designed to meet the enhanced regulatory requirements, if they reflect the characteristics of HTGRs. We believe that we have established a reference for future development of HTGR.

Hydrochemical investigation at the Mizunami Underground Research Laboratory; Compilation of groundwater chemistry data in the Mizunami Group and the Toki Granite (fiscal year 2019)

Fukuda, Kenji; Watanabe, Yusuke; Murakami, Hiroaki; Amano, Yuki; Aosai, Daisuke*; Hara, Naohiro*

JAEA-Data/Code 2020-012, 80 Pages, 2020/10

JAEA-Data-Code-2020-012.pdf:3.55MB

Japan Atomic Energy Agency has been investigating groundwater chemistry to understand the influence of excavation and maintenance of underground facilities as part of the Mizunami Underground Research Laboratory (MIU) Project in Mizunami, Gifu, Japan. In this report, we compiled data of groundwater chemistry and microbiology obtained at the MIU in the fiscal year 2019. In terms of ensuring traceability of data, basic information (e.g. sampling location, sampling time, sampling method and analytical method) and methodology for quality control are described.

Intercomparison of numerical atmospheric dispersion prediction models for emergency response to emissions of radionuclides with limited source information in the Fukushima Dai-ichi Nuclear Power Plant accident

Iwasaki, Toshiki*; Sekiyama, Tsuyoshi*; Nakajima, Teruyuki*; Watanabe, Akira*; Suzuki, Yasushi*; Kondo, Hiroaki*; Morino, Yu*; Terada, Hiroaki; Nagai, Haruyasu; Takigawa, Masayuki*; et al.

Atmospheric Environment, 214, p.116830_1 - 116830_11, 2019/10

https://doi.org/10.1016/j.atmosenv.2019.116830

The utilization of numerical atmospheric dispersion prediction (NDP) models for accidental discharge of radioactive substances was recommended by a working group of the Meteorological Society of Japan. This paper is to validate the recommendation through NDP model intercomparison in the accidental release from the Fukushima Dai-ichi Nuclear Power Plant in 2011. Emission intensity is assumed to be constant during the whole forecast period for the worst-case scenario unless time sequence of emission is available. We expect to utilize forecasts of surface air contaminations for preventions of inhalations of radioactive substances, and column-integrated amounts for mitigation of radiation exposure associated with wet deposition. Although NDP forecasts have ensemble spread, they commonly figure out relative risk in space and time. They are of great benefit to disseminating effective warnings to public without failure. The multi-model ensemble technique may be effective to improve the reliability.

Hydrochemical investigation at the Mizunami Underground Research Laboratory; Compilation of groundwater chemistry data in the Mizunami group and the Toki granite (fiscal year 2017)

Fukuda, Kenji; Watanabe, Yusuke; Murakami, Hiroaki; Amano, Yuki; Hayashida, Kazuki*; Aosai, Daisuke*; Kumamoto, Yoshiharu*; Iwatsuki, Teruki

JAEA-Data/Code 2018-021, 76 Pages, 2019/03

JAEA-Data-Code-2018-021.pdf:3.78MB

Japan Atomic Energy Agency has been investigating groundwater chemistry to understand the influence of excavation and maintenance of underground facilities as part of the Mizunami Underground Research Laboratory (MIU) Project in Mizunami, Gifu, Japan. In this report, we compiled data of groundwater chemistry and microbiology obtained at the MIU in the fiscal year 2017. In terms of ensuring traceability of data, basic information (e.g. sampling location, sampling time, sampling method and analytical method) and methodology for quality control are described.

Onsite chelate resin solid-phase extraction of rare earth elements in natural water samples; Its implication for studying past redox changes by inorganic geochemistry

Watanabe, Takahiro; Kokubu, Yoko; Murakami, Hiroaki; Iwatsuki, Teruki

Limnology, 19(1), p.21 - 30, 2018/01

https://doi.org/10.1007/s10201-017-0513-3

Rare earth element (REE) patterns in natural water and geological samples provides information on changes in past environmental conditions, such as redox changes and material cycles; however, quantitative analysis of REEs in these samples is complicated because of relative low content and mass interference from barium oxide in the inductively coupled plasma mass spectrometry (ICP-MS) analyses. In this study, we adopted onsite solid-phase extraction and preconcentration methods for REEs using an iminobisacetic acid-ethylenediaminetriacetic acid chelate resin for the analyses. Standard reference materials, natural ground water, and spring water samples were used for the evaluation of these methods. The REE patterns in the natural water samples were in good agreement with those obtained using previous methods. Therefore, it was deduced that onsite solid-phase extraction using chelate resin is a rapid and simple preparation technique for REE analyses.

The Applicability of SiC-SiC fuel cladding to conventional PWR power plant

Furumoto, Kenichiro*; Watanabe, Seiichi*; Yamamoto, Teruhisa*; Teshima, Hideyuki*; Yamashita, Shinichiro; Saito, Hiroaki; Shirasu, Noriko

Proceedings of 2017 Water Reactor Fuel Performance Meeting (WRFPM 2017) (USB Flash Drive), 10 Pages, 2017/09

http://www.wrfpm2017.org/upload/draft_file/F-225-PD2.pdf

Since 2015, Mitsubishi Nuclear Fuel (MNF) has joined in a Japanese R&D project of ATF founded by the Ministry of Economy, Trade and Industry (METI) as a subcontractor to Japan Atomic Energy Agency (JAEA) which is the prime contractor to METI. In this program, MNF plans to evaluate an influence of Silicon Carbide (SiC) composite cladding upon fuel rod behavior in current pressurized water reactors (PWR). This paper reports the evaluation result of the applicability of fuel rod with SiC composite cladding for a conventional PWR. For the applicability evaluations of SiC composite to conventional PWR, both of analytical evaluations and out-of-pile tests for SiC composite were conducted. Analytical evaluations were performed by Mitsubishi's own fuel rod design code and the fuel rod behavior evaluation code developed by JAEA. These codes were modified to evaluate the behavior of the fuel rod with SiC composite cladding. As out-of-pile tests, thermal diffusivity measurement and autoclave corrosion test for SiC composite samples were performed. Test apparatus were developed for evaluation of performance of SiC composite under the condition simulated design basis accident (DBA).

Observed and analyzed data for clay veins in granite

Ueki, Tadamasa; Tanabe, Hiroaki*; Niwa, Masakazu; Ishimaru, Tsuneari; Shimada, Koji

JAEA-Data/Code 2016-010, 292 Pages, 2016/09

JAEA-Data-Code-2016-010.pdf:76.12MB

Occurrence of recent activity of faults is often evaluated based on displacements of subsurface sediments covering the faults. However, this evaluation is not applicable for faults that occur where subsurface sediments are not found. In this study, mesoscopic description in a field, microscopic observation using thin sections, chemical composition mapping for polished slabs, X-ray diffraction analysis, particle size distribution analysis, and detailed analysis for quartz fragments (scanning electron microscopy and measurement of electron spin resonance signals) were carried out for clay veins in order to contribute a development of evaluation of fault activity. This Data/Code reports the results of these observation and analyses.

Dipole tracer migration and diffusion tests in fractured sedimentary rock at Horonobe URL

Tanaka, Shingo*; Yokota, Hideharu; Ono, Hirokazu; Nakayama, Masashi; Fujita, Tomoo; Takiya, Hiroaki*; Watanabe, Naoko*; Kozaki, Tamotsu*

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 6 Pages, 2015/05

Mizunami Underground Research Laboratory Project; Compilation of results of geological investigation at the -500m stage

Kawamoto, Koji; Murakami, Hiroaki; Ishibashi, Masayuki; Sasao, Eiji; Watanabe, Kazuhiko; Mikake, Shinichiro; Ikeda, Koki

JAEA-Data/Code 2014-014, 27 Pages, 2014/08

JAEA-Data-Code-2014-014.pdf:24.28MB
JAEA-Data-Code-2014-014-appendix(CD-ROM).zip:92.23MB

This document presents the data of geological investigations at the -500m stage of the MIU from the 2011 fiscal year to the 2013 fiscal year. At the -500m stage of the MIU, although the Cretaceous Toki granite is distributed, pegmatite, aplite and lampropyre dike are distributed partially.