Research plan on geosphere stability for long-term isolation of radioactive waste (Scientific program for fiscal year 2023)

Niwa, Masakazu; Shimada, Koji; Sueoka, Shigeru; Fujita, Natsuko; Yokoyama, Tatsunori; Ogita, Yasuhiro; Fukuda, Shoma; Nakajima, Toru; Kagami, Saya; Ogata, Manabu; et al.

JAEA-Review 2023-017, 27 Pages, 2023/10

JAEA-Review-2023-017.pdf:0.94MB

This report is a plan of research and development (R&D) on geosphere stability for long-term isolation of high-level radioactive waste (HLW) in Japan Atomic Energy Agency (JAEA), in fiscal year 2023. The objectives and contents in fiscal year 2023 are described in detail based on the JAEA 4th Medium- and Long-term Plan (fiscal years 2022-2028). In addition, the background of this research is described from the necessity and the significance for site investigation and safety assessment, and the past progress. 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.

Development of a statistical evaluation method for core hot spot temperature in sodium-cooled fast reactor under natural circulation conditions

Doda, Norihiro; Igawa, Kenichi*; Iwasaki, Takashi*; Murakami, Satoshi*; Tanaka, Masaaki

Nuclear Engineering and Design, 410, p.112377_1 - 112377_15, 2023/08

https://doi.org/10.1016/j.nucengdes.2023.112377

To enhance the safety of sodium-cooled fast reactors, the decay heat in the core must be removed by natural circulation even if the AC power supply to the forced circulation equipment is lost. Under natural circulation conditions, sodium flow is driven by buoyancy, and flow velocity and temperature distribution influence each other. Thus, it is difficult to evaluate the core hot spot temperature by deterministically considering the uncertainties affecting flow and heat. In this study, a statistical evaluation method is developed for the core hot spot temperature by using Monte Carlo sampling methods. The applicability of the core hotspot evaluation method was confirmed in three representative events during natural circulation decay heat removal operations in loop-type sodium-cooled fast reactors.

Investigation of the phonon dispersion associated with superlattice reflections in the BiS-based superconductor LaBiSOF

Tamatsukuri, Hiromu; Hasegawa, Takumi*; Sagayama, Hajime*; Mizumaki, Masaichiro*; Murakami, Yoichi*; Kajitani, Joe*; Higashinaka, Ryuji*; Matsuda, Tatsuma*; Aoki, Yuji*; Tsutsui, Satoshi*

Physical Review B, 107(2), p.024303_1 - 024303_8, 2023/01

https://doi.org/10.1103/PhysRevB.107.024303

Plant system study of France-Japan common concept on Sodium-cooled Fast Reactor

Kato, Atsushi; Yamamoto, Tomohiko; Ando, Masato; Chikazawa, Yoshitaka; Murakami, Hisatomo*; Oyama, Kazuhiro*; Kaneko, Fumiaki*; Higurashi, Koichi*; Chanteclair, F.*; Chenaud, M.-S.*; et al.

EPJ Nuclear Sciences & Technologies (Internet), 8, p.11_1 - 11_10, 2022/06

https://doi.org/10.1051/epjn/2022006

This paper provides an overview of plant system studies to establish a common technical view for Sodium-cooled Fast Reactor concept between France and Japan based on ASTRID600 and the new concept with downsized output called ASTRID150. One of important issues on a reactor structure design is to enhance seismic resistance to be tolerable against strong earthquake such that postulated in Japan. A concept of High Frequency Design is shared, and the design options related to HFD have been examined and design recommendations are established. In addition, this paper include results of studies for a steam generator, a decay heat removal system, a fuel handling system and a containment vessel.

Progress in conceptual design of a pool-type sodium-cooled fast reactor in Japan

Kato, Atsushi; Kubo, Shigenobu; Chikazawa, Yoshitaka; Miyagawa, Takayuki*; Uchita, Masato*; Suzuno, Tetsuji*; Endo, Junji*; Kubo, Koji*; Murakami, Hisatomo*; Uzawa, Masayuki*; et al.

Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Sustainable Clean Energy for the Future (FR22) (Internet), 11 Pages, 2022/04

The authors are carrying out conceptual design studies for a pool-type sodium-cooled fast reactor. There are main challenges such as measures against severe earthquake in Japan, thermal hydraulic in a reactor vessel (RV), a decay heat removal system design. When the JP-pool SFR of 650 MWe is installed in Japan, it shall be designed against the severe seismic conditions. Additionally, a newly three-dimensional seismic isolation system is under development.

Compilation of previous studies on secondary effects induced by earthquake and fault activity (Contract research)

Goto, Akira; Murakami, Masaki*; Sakai, Ryutaro*; Terusawa, Shuji*; Sueoka, Shigeru

JAEA-Review 2020-003, 60 Pages, 2020/03

JAEA-Review-2020-003.pdf:4.43MB

One of the natural phenomena that may affect the geological disposal system are earthquake and fault activity. Fault displacement due to the earthquake and fault activity will be considered the direct effects. In addition to it, it is necessary to consider the secondary effects include secondary faults formed by the seismic fault activity as well as spring water and mud volcanoes that are generated by fluid movement attributed to the fault activity. This paper introduces previous studies performed focused on the hydraulic effects (spring water and mud volcanoes) and mechanical effects (secondary faults) in order to understand the effects of these secondary phenomena on the geological disposal system. We were able to collect 142 literatures from Japan and overseas by searching for related keywords in Japanese and English. As a result, we compiled case studies of each secondary impact. From the viewpoint of geological disposal, we extracted the following issues for future research and development. As for the sump water induced by earthquakes and faulting, accumulation of information related to its mechanism, affected area, and activity history is required. As for the mud volcanoes, reviewing of the mechanism of anomalous pore water pressure that causing the formation, also development of estimation technique are required. And for the secondary faults, accumulation of the detailed spatial distribution and reviewing of formation mechanism are required.

Study on the evaluation method to determine the radioactivity concentration in radioactive waste generated from the dismantling of research reactors

Murakami, Masashi; Hoshino, Yuzuru; Nakatani, Takayoshi; Sugaya, Toshikatsu; Fukumura, Nobuo*; Sanda, Toshio*; Sakai, Akihiro

JAEA-Technology 2019-003, 50 Pages, 2019/06

JAEA-Technology-2019-003.pdf:4.42MB

Toward the establishment of a common approach to determine the radioactivity concentrations in dismantling wastes arising from research reactors, radionuclide concentrations in the reactor structure materials of aluminum, carbon steel, shield concrete, and graphite of TRIGA Mark II reactor at Rikkyo University, Japan, were evaluated with both radiochemical analysis and theoretical calculation. The measured nuclides by the radiochemical analysis were H, Co, and Ni in aluminum, H, Co, Ni, and Eu in carbon steel, H, Co, and Eu in shield concrete, and H, C, Co, Ni, and Eu in graphite. Neutron-flux distributions and neutron-induced activities were computed with DORT and ORIGEN-ARP codes, respectively. Using the results of material composition analysis, radioactivity concentrations were conservatively predicted with good accuracy except for graphite material.

Burial environment of bronze artifacts and behavior of bronze metal components at Yanagisawa archaeological site in Nagano Prefecture

Mitsui, Seiichiro; Murakami, Ryu*; Ueda, Norio*; Hirabayashi, Akira*; Hirota, Kazuho*

Bunkazai Kagaku, (77), p.1 - 14, 2018/10

Well-preserved bronze artifacts comprising five bells and eight halberds from the Yayoi Period were excavated at the Yanagisawa archaeological site in Nakano City, Nagano Prefecture in 2007. Comprehensive analysis of soil and groundwater samples at the site was carried out and geochemical calculations were made to better understand the local conditions that led to the artifacts being so well preserved. Analysis of the soil surface adjacent to the bronze artifacts identified cuprite (CuO) as the main corrosion product. Migration behavior of the bronze metal components, copper, tin, and lead, both inside and outside of the burial pit, was also investigated. Copper and lead had migrated 2 m from the burial pit, whereas tin was confined to the immediate vicinity of the bronze artifacts. The difference in migration behavior of these elements can be explained in terms of the chemical stability of the solid phases. The main factor contributing to the well-preserved state of the bronze artifacts was the tin content, which is thought to have formed a protective layer of cassiterite (SnO) on the outer surface of the bronze artifacts.

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.

Determination of dissolved natural thorium and uranium in Horonobe and Mizunami Underground Research Laboratory groundwater and its thermodynamic analysis

Sasaki, Takayuki*; Kokami, Takayuki*; Kobayashi, Taishi*; Kirishima, Akira*; Murakami, Hiroaki; Amano, Yuki; Mizuno, Takashi; Iwatsuki, Teruki; Sasamoto, Hiroshi; Miyakawa, Kazuya

Journal of Nuclear Science and Technology, 54(3), p.373 - 381, 2017/03

http://www.tandfonline.com/doi/abs/10.1080/00223131.2016.1273801

Trace amounts of natural thorium and uranium in deep groundwater were investigated at two underground research laboratories situated at Horonobe and Mizunami, Japan. The groundwater was sampled from underground boreholes, and the colloid contribution was checked by in situ two size-fractionated ultrafiltration systems. A decrease in the concentration after in situ filtration suggested the presence of natural colloids and suspended matter that were carriers of a portion of the elements. The result of the Th and U concentrations in groundwater after 10 kDa filtration was analyzed thermodynamically using existing hydrogeological and geochemical data such as the mineral components in the groundwater at a given pH, ionic strength, concentration of co-existing ions, redox potential, and solid phase assumed. A crystalline solid phase made the solubility very low compared with that of the amorphous phase, and the solubility agreed well with the concentrations measured.