Reformation of protective oxide layers on artificially abraded surfaces of FeCrAl alloy during 4000 h exposure in flowing lead-bismuth eutectic

Kondo, Masatoshi*; Kitamura, Yoshiki*; Kawarai, Atsushi*; Saito, Shigeru; Obayashi, Hironari

Corrosion Science, 262, p.113646_1 - 113646_14, 2026/04

https://doi.org/10.1016/j.corsci.2026.113646

The corrosion resistance of FeCrAl alloy APMT (Fe-21Cr-5Al-3Mo) in flowing lead-bismuth eutectic (LBE) was investigated by corrosion tests performed at 723 K using a non-isothermal forced convection loop. The oxygen concentration in flowing LBE was controlled at 110 wt%. No severe corrosion or erosion was detected on the specimens exposed to flowing LBE for 2000 h and 4000 h. Multiple oxide layers consisting of Fe-rich, Cr-rich and Al-rich sub-layers were formed in situ on the surface of APMT during the corrosion tests, which effectively suppressed corrosion and erosion. The oxide layers were intentionally removed by gentle abrasion prior to re-immersion and the specimens were then re-immersed in flowing LBE for an additional 2000 h. The oxide layers were spontaneously re-formed in situ on the abraded surface. This behavior indicates a self-healing capability. The results of micro-scratch tests indicated that the in-situ formed multiple oxide layers exhibited high adhesion strength in the shear direction after the 2000 h corrosion test.

Report on research and development of neutron beam utilization at JRR-3 for internal use in FY2023 and FY2024

Materials Sciences Research Center

JAEA-Review 2025-058, 175 Pages, 2026/03

JAEA-Review-2025-058.pdf:8.17MB

Fifteen neutron beam experimental instruments managed by JAEA are installed in JRR-3 (Japan Research Reactor No.3) and are available for internal use including upgrading of instruments and for external users to produce various research results. This report summarizes the progress of internal application research and technical development such as upgrading of neutron beam instruments in the fiscal years 2023 and 2024 after the restart of operation.

Development of a bioassay method for internal radiation dose assessment FY 2021 (Joint research)

Nagaoka, Mika; Maehara, Yushi; Ono, Masako*; Nihei, Hidekazu*; Hirao, Moe; Fujita, Hiroki

JAEA-Research 2026-001, 115 Pages, 2026/03

JAEA-Research-2026-001.pdf:6.32MB

In fiscal year 2021, Japan Atomic Energy Agency conducted a joint research with Tokyo Electric Power Company Holdings, Inc. to develop a bioassay method. This report presents the results of studies on a systematic analysis method for -ray and pure -ray nuclides in urine samples. Specifically, experiments with tracer-containing samples were conducted to verify the nuclide separation performance of the systematic analysis method utilizing multiple solid-phase extraction resins and the sample preparation method for radioactivity measurement. Furthermore, calculation methods for uncertainty and detection limit of radioactivity in -ray nuclide analysis were summarized.

Conceptual design of pilot ADS

Nishihara, Kenji; Fukushima, Masahiro; Abe, Takumi; Katano, Ryota; Yee-Rendon, B.; Iwamoto, Hiroki; Sugawara, Takanori; Obayashi, Hironari; Saito, Shigeru

JAEA-Research 2025-013, 125 Pages, 2026/03

JAEA-Research-2025-013.pdf:4.68MB

A conceptual design for a pilot Accelerator Driven subcritical System (ADS) was developed as a precursor to a commercial ADS aimed at partitioning and transmutation of minor actinides. The output of the pilot ADS was set at 200 MW. Based on safety assessment results, the design incorporates deep subcriticality and safety rods. Core design, accelerator design, target design, and in-vessel equipment design were performed, clarifying the specific concept.

Effect of coaxial HPGe detector structure on -ray beam measurements

Omer, M.; Shizuma, Toshiyuki*; Koizumi, Mitsuo; Taira, Yoshitaka*; Zen, H.*; Ogaki, Hideaki*; Hajima, Ryoichi*

Radiation Physics and Chemistry, 240, p.113467_1 - 113467_8, 2026/03

https://doi.org/10.1016/j.radphyschem.2025.113467

Experimental study of AESOP code for aerosol removal behavior from a rising gas bubble in water pool and parametric study for application to sodium pool system

Miyahara, Shinya*; Koie, Ryusuke*; Uno, Masayoshi*; Kawaguchi, Munemichi*; Sato, Rika; Seino, Hiroshi

Nuclear Engineering and Design, 446(Part A), p.114523_1 - 114523_14, 2026/01

https://doi.org/10.1016/j.nucengdes.2025.114523

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.

Prediction analysis of the development of the excavation damaged zone around the gallery excavated at 500 m depth at Horonobe Underground Research Laboratory

Aoyagi, Kazuhei; Tamura, Tomonori; Ozaki, Yusuke; Ishii, Eiichi; Motoshima, Takayuki*; Sugawara, Kentaro*

Dai-51-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu(Internet), p.119 - 124, 2025/12

In a high-level radioactive waste disposal, it is important to understand the extent of the Excavation Damaged Zone (EDZ) because it can be one of the factors to determine whether disposal galleries or pits can be excavated or not in the design or construction phases. In this study, we performed a hydro-mechanical coupling analysis to simulate the three-dimensional excavation of the twin galleries which were excavated at a depth of 500 m in the Horonobe Underground Research Laboratory. The analysis revealed that the EDZ was developed 1.5-2.0 m from the gallery wall. The stress acting on the shotcrete was within the ultimate limit state. Based on these results, we estimated that the stability of the twin galleries will be maintained, despite the relatively large extent of the EDZ.

Development and evaluation of a real-time 3D positioning embedded system combining wireless UWB and camera image analysis (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tokai National Higher Education and Research System*

JAEA-Review 2025-023, 63 Pages, 2025/11

JAEA-Review-2025-023.pdf:5.74MB

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 FY2023. 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 FY2022, this report summarizes the research results of the "Development and evaluation of a real-time 3D positioning embedded system combining wireless UWB and camera image analysis" conducted in FY2023. The present study aims to realize an embedded system that combines two of the latest popular technologies, "wireless UWB (Ultra Width Band)" and "multi-camera object recognition" with the goal of simple real-time 3D positioning with less than 10 cm accuracy by a human or robot for measuring air doses in nuclear reactor buildings. In this research, Gifu Univ. and National Institute of Technology, Fukushima College have developed an embedded system with camera shooting function, camera analysis function, and wireless communication function, in order to realize real-time 3D positioning based on the analysis of camera images by using these multiple devices. The Univ. of Tokyo and LocationMind Inc. will apply UWB real-time positioning technology to the inside of nuclear reactor buildings and attempt to develop technology to improve stability. Nagoya Univ. will be in charge of verifying wireless UWB stability from the hardware side by using electromagnetic wave absorbing materials. The radiation resistance evaluation will be conducted in cooperation with the JAEA and National Institute of Technology, Fukushima College.

Re-evaluation of nuclear criticality characteristics for infinite and finite heterogeneous lattice systems composed of uranium-zirconium hydride fuel rods used in the TRIGA annular core pulse reactor NSRR

Yanagisawa, Hiroshi; Motome, Yuiko

JAEA-Research 2025-010, 197 Pages, 2025/11

JAEA-Research-2025-010.pdf:3.5MB

For understandings of nuclear criticality risks of TRIGA fuel rods and review of safety measures for handling them, nuclear criticality characteristics for infinite and finite heterogeneous lattice systems composed of the NSRR fuel rods were re-evaluated with the use of a detailed computational model for the fuel rod. The MVP version 3 code was used with the JENDL libraries including the latest version, JENDL-5, for the re-evaluation. As the criticality characteristics, variations of neutron multiplication factors of the infinite and water-reflected finite systems were examined in detail with parameters of the lattice pitch and density of moderator water. From the results of the re-evaluated criticality characteristics, the minimum critical number of fuel rods for the water-reflected hexagonal shaped lattice system was obtained to be 46.8 0.2 using the JENDL-5 library. Moreover, the attainability of criticality without the water as moderator and reflector was examined because the zirconium hydride moderator and graphite reflector are equipped with the TRIGA fuel rod. It was found that the criticality is possible to be attained by 115.7 0.6 of the number of fuel rods, which is the smaller number of fuel rods than loaded in the NSRR standard core, even though no water exists.