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Wakai, Takashi; Ando, Masanori; Okajima, Satoshi; Toyota, Kodai; Ishigami, Katsuo*; Onuma, Terumitsu*; Takahashi, Ryoya*; Asayama, Tai
Nihon Kikai Gakkai Rombunshu (Internet), 92(961), p.26-00004_1 - 26-00004_12, 2026/09
This paper describes current efforts within the Japan Atomic Energy Agency to develop a new materials surveillance technology for sodium-cooled fast reactors that aims at raising the confidence levels in operating reactors' structural integrity to the ones which could otherwise be achieved only by a vast amount of long-term material test data that needs decades to accumulate. The technology would allow for monitoring on-going materials degradation processes in an actual reactor, namely fatigue and creep-fatigue, by inserting a newly developed specimen for this purpose into the reactor and establishing procedures to observe and evaluate the specimen to get desired information such as the extent of degradation and residual life. To establish the test procedure, a passive creep-fatigue test model was developed in the framework of the "Civil Nuclear Energy Research and Development Working Group (CNWG)", a collaboration agreement between the US and Japan, and a demonstration test was performed under cyclic thermal loads using an electric furnace. Temperature conditions had been determined based on finite element analyses. As a result, the test specimen failed by several hundred thermal cycles. Macroscopic inspection of the specimen after the test showed the test had been performed successfully without buckling. Fracture surface observations suggested that the failure caused probably by fatigue or creep-fatigue.
Furuta, Takuya; Hashimoto, Shintaro; Ogawa, Tatsuhiko; Tanimura, Yoshihiko
Nuclear Instruments and Methods in Physics Research A, 1086, p.171320_1 - 171320_8, 2026/06
Times Cited Count：0 Percentile：0.00(Instruments & Instrumentation)A new function to incorporate nuclear data libraries with outgoing particles plus residual nuclei in specific excitation states for neutron-induced reactions has been implemented in a Monte Carlo simulation code, Particle and Heavy Ion Transport code System (PHITS). With this function, accurate predictions of outgoing particle spectra and angular distributions according to the nuclear data libraries become possible, while accounting for production of residual nuclei and de-excitation gammas, conserving total energy and momentum in each event. This feature allows users to perform high-precision simulations of detector responses and radiation damage in materials.
Noseck, U.*; Sch
fer, T.*; Alonso, U.*; Hamamoto, Takafumi*; Havlova, V.*; Hibberd, R.*; Ishidera, Takamitsu; Kitamura, Akira; Klajmon, M.*; Missana, T.*; et al.
Applied Geochemistry, 201, p.106762_1 - 106762_23, 2026/04
Times Cited Count：0 Percentile：0.00(Geochemistry & Geophysics)Thermodynamic benchmark calculations have been performed to better understand the behavior of 
Se(VI), 
Tc(VII), 
U(VI), 
Np(V), 
Am(III), Th(IV) and 
Pu(IV)) in the evolving geochemical conditions of the Long-term In-situ Test (LIT) at the Grimsel Test Site (GTS) and corresponding mock-up experiment. It also aims to identify the status of the geochemical speciation models and databases for these elements. The experiments are simulating the near-field conditions in some radioactive waste repository concept including a bentonite engineered barrier emplaced in crystalline rock and the findings are contributing to the long-term safety assessment of these facilities.
Matsui, Tetsuya; Shimodaira, Masaki; Yamaguchi, Yoshihito; Toyama, Takeshi; Katsuyama, Jinya
JAEA-Research 2025-017, 41 Pages, 2026/03
JAEA-Research-2025-017.pdf:4.52MB
The JAEA Safety Research Center has been conducting fundamental research on advanced inspection and structural integrity assessment technologies since FY2024, including the development of a machine-learning-based ultrasonic flaw detection method using an ultrasonic simulator. To assess the simulator's applicability, phased array ultrasonic testing (PAUT) results produced by the simulator were compared with actual measurement data. Due to limited publicly available datasets, an intergranular crack in the pressurizer spray line piping of Kansai Electric Power Co. Inc.'s Ohi Nuclear Power Station Unit 3 was selected as the reference case. PAUT linear scanning analysis at a 45
incident angle detected the crack's corner and edge echoes. Strong columnar-crystal propagation echoes were also observed within the weld metal, with their intensity showing dependence on the symmetric axis angle. Analysis at a 31 incident angle similarly identified strong columnar-crystal propagation echoes, which connected to the crack's corner echoes and propagated into the weld region. These results align with actual measurements, indicating that the observed weld-metal echoes are likely attributable to columnar-crystal propagation.
Nakajima, Ryota; Sakai, Tatsuya; Tani, Riku; Handa, Yuichi; Sunaoshi, Mizuho*; Inoue, Hidetaka*; Yamada, Satoshi; Shimizu, Osamu
JAEA-Technology 2025-012, 39 Pages, 2026/01
JAEA-Technology-2025-012.pdf:2.31MB
JAERI's Reprocessing Test Facility (JRTF) has transition to decommissioning since 1996 and inside the facility dismantled equipment and instrument. In the dismantling and removal work of glove boxes and other equipment, starting in October 2022, we prepared a "Manual for Separation of Dismantled Materials of JRTF" and carried out sorting and separation of the generated dismantled waste with the aim of producing waste package that meets the technical standards required for disposal to a landfill facility. This report describes the results and findings of sorting and separating the dismantled waste generated during the dismantling and removal work of glove boxes and other equipment in accordance with the "Manual for Separation of Dismantled Materials of JRTF".
Asahina, Daisuke*; Takamura, Hiroaki*; Tsukamoto, Koji*; Honda, Fumito*; ITO, Takashi*; IWATA, Naoki*; Aydan, 
mer*; Sato, Toshinori
Dai-51-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu(Internet), p.43 - 47, 2025/12
Fault zones commonly contain distinctive structures such as fault cores and damage zones, where physical properties vary locally. These zones are important for evaluating underground safety and groundwater flow in waste disposal, yet quantitative measurements near faults remain limited. We applied Schmidt hammer and needle penetration tests to assess the mechanical properties of the rocks near the Tanakura Fault, in a simple, non-destructive manner. The results showed a clear spatial variation in measured values with distance from the fault gouge boundary, suggesting that combining methods with different scales and sensitivities can provide a more comprehensive evaluation of rock mass properties near faults.
Sakaba, Nariaki; Ohashi, Hirofumi; Sato, Hiroyuki
Nihon Genshiryoku Gakkai-Shi ATOMO
, 67(10), p.593 - 597, 2025/10
no abstracts in English
Tagawa, Akihiro
Nihon Genshiryoku Gakkai-Shi ATOMO, 67(9), p.510 - 513, 2025/09
no abstracts in English
Sakamoto, Masahiro; Okumura, Keisuke; Kanno, Ikuo; Matsumura, Taichi; Terashima, Kenichi; Riyana, E. S.; Kaneko, Junichi*; Mizokami, Masato*; Mizokami, Shinya*
Journal of Nuclear Science and Technology, 62(8), p.756 - 765, 2025/08
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Hasegawa, Toshinari; Nagasumi, Satoru; Ishitsuka, Etsuo; Egashira, Keiichiro*; Furuya, Aoi*; Ando, Ryota*; Sakaguchi, Akira*; Sakurai, Yosuke; Nakano, Yumi*; Iigaki, Kazuhiko
JAEA-Technology 2025-004, 20 Pages, 2025/07
JAEA-Technology-2025-004.pdf:1.67MB
Four people from three universities participated in the 2024 summer holiday practical training with the theme of "Technical development on HTTR". The participants practiced the analysis of the HTTR core, the analysis of 
Cs deposition behavior in the primary cooling system, and the feasibility study of nuclear rockets using HTGR. In the questionnaire after this training, there were comments from participants that it was beneficial as a work experience and that it was meaningful because of many opportunities to communicate with staff. These impressions suggest that this training was generally evaluated as good.
Toyota, Kodai; Onizawa, Takashi; Wakai, Eiichi*
Research & Development in Material Science (Internet), 21(5), p.2632 - 2637, 2025/06
Fuyushima, Takumi; Sayato, Natsuki; Otsuka, Kaoru; Endo, Yasuichi; Tobita, Masahiro*; Takemoto, Noriyuki
JAEA-Testing 2024-008, 38 Pages, 2025/03
JAEA-Testing-2024-008.pdf:2.37MB
In Japan Materials Testing Reactor (JMTR), irradiation tests had been conducted by loading specimens into capsules for irradiating fuels and materials. The thermal design calculation of capsules is significant to irradiate various types of specimens at the target temperature. The decommissioning plan of JMTR was approved in March 2021, and the Department of Waste Management and Decommissioning Technology Development is currently working on irradiation plans by foreign testing reactors as an alternative for JMTR. A one-dimensional thermal calculation code "GENGTC", which was developed at the Oak Ridge National Laboratory in U.S., is used for capsule design and irradiation tests. GENGTC has been repeatedly improved as improvements of computer performance, but there were some defects in calculation function. Therefore, we investigated the cause of the problem and changed the program from the currently used FORTRAN77 language program to a Visual Basic language program that uses the macro calculation function of Excel. In addition, the program was improved to make it easier to use the calculation code.
Yomogida, Takumi; Takahashi, Yoshio*
Chikyu Kagaku, 59(1), p.1 - 10, 2025/03
X-ray absorption fine structure XAFS spectroscopy techniques, which are applicable to almost all elements, provide information on elemental valence and local structure with high elemental selectivity and high sensitivity. It has become an indispensable method in space geochemistry and environmental chemistry. This review presents examples of the application of fluorescence XAFS methods to elements that are difficult to detect by conventional methods, and examples where new chemical species information has been obtained by increasing the energy resolution of the X-ray fluorescence (XRF) detection system to obtain XAFS.
Fujita, Tatsuya
Journal of Nuclear Science and Technology, 62(5), p.470 - 479, 2025/01
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)This study confirmed the efficiency of a combined approach of the control variates (CV) and the Latin hypercube sampling (LHS), which enhanced the random-sampling-based uncertainty quantification due to cross-section (XS) covariance data, by considering the effect of statistical variation and also performed the sensitivity analyses on the influence due to the selection of alternative parameter to apply CV. The convergence performance for the uncertainty of infinite multiplication factor (k-infinity) during the random sampling was compared between several efficient sampling techniques such as the antithetic sampling (AS), LHS, CV, and the combined approaches of them in the PWR-UO
fuel assembly geometry. The k-infinity uncertainty was evaluated by statistically processing several times Serpent2 calculations using perturbed ACE-formatted XS files based on ENDF/B-VIII.0. CV+LHS was more efficient than AS, LHS, and CV+AS. In addition, sensitivity analyses were performed to select alternative parameters used in CV. The 3
3 mini fuel lattice calculation can improve the efficiency of CV+LHS. The reason was qualitatively considered that this calculation can capture the influence of XS covariance data for Gd isotopes. Consequently, the applicability of CV+LHS for the improvement of convergence performance to evaluate the k-infinity uncertainty during the random sampling was confirmed.
Sm synchrotron-radiation-based M
ssbauer spectroscopy of Sm-based heavy fermion compoundsTsutsui, Satoshi; Higashinaka, Ryuji*; Mizumaki, Masaichiro*; Kobayashi, Yoshio*; Nakamura, Jin*; Ito, Takashi; Yoda, Yoshitaka*; Matsuda, Tatsuma*; Aoki, Yuji*; Sato, Hideyuki*
Interactions (Internet), 245(1), p.9_1 - 9_10, 2024/12
Wakui, Takashi; Saito, Shigeru; Futakawa, Masatoshi
Jikken Rikigaku, 24(4), p.212 - 218, 2024/12
Irradiation damage is one of the main factors determining the lifetime of the mercury target vessel for spallation neutron source in J-PARC. To understand material degradation of the used vessels, it is planned to conduct an evaluation using inverse analyses with indentation tests on the structural materials of the used vessels and numerical experiments. This evaluation technique was applied to two kinds of ion-irradiated materials with different displacement damage doses, in which the irradiation condition was simulated. It could be confirmed that the ultimate strength increased, and the total elongation decreased with increasing irradiation. These trends are like the material degradation behaviors which have been reported by using small specimen's tensile tests.
Hirota, Noriaki; Nakano, Hiroko; Takeda, Ryoma; Ide, Hiroshi; Tsuchiya, Kunihiko; Kobayashi, Yoshinao*
Material Science and Technology of Japan, 61(6), p.248 - 252, 2024/12
A comparative analysis of the 0.2 % yield stress in SUS304L stainless steel revealed that lower strain rates and higher temperatures significantly reduce yield stress. Grain refinement from 68.6 
m to 0.59 m minimally impacted the rate of yield stress reduction at slower strain rates. However, finer grains showed a decrease in yield stress at reactor operating temperature compared to room temperature. In slow strain rate tests under conditions promoting intragranular stress corrosion cracking (SCC), SUS304L with grain sizes of 28.4 m or smaller exhibited similar fracture strains comparable to those at reactor operating temperatures, whereas coarse-grained SUS304L showed reduced fracture strain. Microstructural analysis showed that in smaller grains, over 87 % of the fracture surface was ductile. In particular, SUS304L with 0.59 m grains exhibited a higher presence of {111} / 3 boundaries, which decreased with grain growth. These results indicate that grain refinement will suppress intragranular SCC by slowing corrosion progression through increased {111} / 3 boundaries.
Wakui, Takashi; Saito, Shigeru; Futakawa, Masatoshi
Materials, 17(23), p.5925_1 - 5925_14, 2024/12
Times Cited Count：0 Percentile：0.00(Chemistry, Physical)The ductile properties of irradiated materials are one of the important indicators related to their structural integrity. Indentation tests are used for evaluating the ductile properties easily and rapidly. Constants in the material constitutive equation were identified via inverse analysis using the Kalman filter, such that the numerical experimental results reproduced the indentation test results. Numerical tensile experiments were conducted using stress-strain curves with the identified constants to obtain nominal stress-strain curves. Furthermore, two methods were proposed for evaluating the total elongation. Evaluated minimum total elongation was 10 %. The evaluation results of ion-irradiated materials were similar to the tensile test results of irradiated materials.
neutron diffractionNaeem, M.*; Ma, Y.*; Knowles, A. J.*; Gong, W.; Harjo, S.; Wang, X.-L.*; Romero Resendiz, L.*; 6 of others*
Materials Science & Engineering A, 916, p.147374_1 - 147374_8, 2024/11
Times Cited Count：5 Percentile：44.40(Nanoscience & Nanotechnology)Li, F.; Narukawa, Takafumi; Udagawa, Yutaka
Journal of Nuclear Science and Technology, 61(8), p.1036 - 1047, 2024/08
Times Cited Count：1 Percentile：11.68(Nuclear Science & Technology)