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Li, X.; Yamaji, Akifumi*; Sato, Ikken*; Yamashita, Takuya
Annals of Nuclear Energy, 214, p.111217_1 - 111217_13, 2025/05
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Nuclear Science Research Institute
JAEA-Review 2024-058, 179 Pages, 2025/03
JAEA-Review-2024-058.pdf:7.42MB
Nuclear Science Research Institute (NSRI) is composed of Planning and Management Department and six departments, namely Department of Operational Safety Administration, Department of Radiation Protection, Engineering Services Department, Department of Research Reactor and Tandem Accelerator, Department of Criticality and Hot Examination Technology and Department of Decommissioning and Waste Management, and each department manages facilities and develops related technologies to achieve the "Medium- to Long-term Plan" successfully and effectively. And, four research centers which are Advanced Science Research Center, Nuclear Science and Engineering Center, Nuclear Engineering Research Collaboration Center and Materials Sciences Research Center, belong to NSRI. In order to contribute the future research and development and to promote management business, this annual report summarizes information on the activities of NSRI of JFY 2023 as well as the activity on research and development carried out by Collaborative Laboratories for Advanced Decommissioning Science, Nuclear Safety Research Center and activities of Nuclear Human Resource Development Center, using facilities of NSRI.
Tobita, Yoshiharu; Tagami, Hirotaka; Ishida, Shinya; Onoda, Yuichi; Sogabe, Joji; Okano, Yasushi
IAEA-TECDOC-2079, p.72 - 84, 2025/00
Since the fast reactor core is not in the maximum reactivity configuration, a hypothetical core disruptive accident could lead to the prompt criticality due to a change in the core material configuration, and the resulting energy generation has been one of the issues in fast reactor safety, and therefore appropriate measures are needed to mitigate and contain the effect of energy generated in the accident. In order to assess the effectiveness of these mitigative measures, a set of computer codes to analyze the event progressions and energy generation behavior in the ATWS of fast reactors have been developed, maintained, and improved under international collaboration in JAEA. Since the important physical phenomena, which govern the event progression, vary along with the progression of the accident, the whole accident process is divided into several phases in the analysis of accident, and dedicated analysis methods for each phase are provided to analyze the event progression in each phase. The organization and overview of these analysis methods are described in this paper. As a representative example of the validation approaches in applying these analysis methods to the reactor safety assessment in licensing procedure in Japan, the validation studies to confirm the applicability to reactor analysis of the SIMMER code for analyzing core material movement and reactor power, which is important to analyze the energy generation in the accident, are presented in the paper. The validation studies of the SIMMER code confirmed the applicability of SIMMER to the reactor analysis, while the critical phenomena that the effect of their uncertainty in the reactor analysis should be checked were also recognized.
Hata, Koji*; Niunoya, Sumio*; Aoyagi, Kazuhei
International Journal of the JSRM (Internet), 20(1), p.240104_1 - 240104_4, 2024/11
Japan Atomic Energy Agency has been conducting R&D activities to enhance the reliability of high-level radioactive waste deep geological disposal technology. In this project, one of the challenges is the development of methods for long-term monitoring of rock mass behavior. Therefore, in January 2014, the long-term measurements of the hydro-mechanical behavior of the rock mass were launched using the three types of optical sensors in the vicinity of the shaft excavated deeper than 350 m at the Horonobe Underground Research Center. The measurement results show that Acoustic emission occur frequently up to 1.5 m from the wall during excavation. In addition, hydraulic conductivity increased by 2-4 orders of magnitude. Elastoplastic analysis revealed that the hydraulic behavior of the rock mass affected the pore pressure fluctuations and caused micro-fractures. Based on this, a conceptual model is developed to represent the excavation damaged zone, which contributes to the safe geological disposal of radioactive waste.
Iwata, Yoshihiro; Miyabe, Masabumi; Wells, S. R.*; Yamamoto, Yuta*; Hasegawa, Shuichi*
Proceedings of International Topical Workshop on Fukushima-Daiichi Decommissioning Research 2024 (FDR2024) (Internet), 4 Pages, 2024/10
In this study, triple and double resonance ionization schemes of atomic Ca were developed, aiming for the separation of odd isotopes by (i) laser polarization-dependent selection rules, and (ii) large isotope shifts of odd Ca isotopes in the Rydberg levels. Separation of odd isotopes was confirmed under the orthogonal condition. Suppression of non-resonant ionization of 
Ca by the electric field in the ionization region could further improve the optical isotope selectivity of 
Ca.
Motegi, Kosuke; Shibamoto, Yasuteru; Hibiki, Takashi*; Tsukamoto, Naofumi*; Kaneko, Junichi*
JAEA-Review 2024-039, 45 Pages, 2024/09
JAEA-Review-2024-039.pdf:2.23MB
Several heat transfer correlations have been reported related to single-phase opposing flow; however, these correlations are based on experiments conducted in various channel geometries, working fluids, and thermal flow parameter ranges. Therefore, establishing a guideline for deciding which correlation should be selected based on its range of applicability and extrapolation performance is important. This study reviewed the existing heat transfer correlations for turbulent opposing-flow mixed convection. Furthermore, the authors evaluated the predictive performance of each correlation by comparing them with the experimental data obtained under various experimental conditions. The Jackson and Fewster, Churchill, and Swanson and Catton correlations can accurately predict all the experimental data. The authors confirmed that heat transfer correlations using the hydraulic-equivalent diameter as a characteristic length can be used for predictions regardless of channel-geometry differences. Furthermore, correlations described based on nondimensional dominant parameters can be used for predictions regardless of the differences in working fluids.
Collaborative Laboratories for Advanced Decommissioning Science; Tokyo Institute of Technology*
JAEA-Review 2024-012, 122 Pages, 2024/09
JAEA-Review-2024-012.pdf:6.31MB
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 FY2022. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station (hereafter referred to "1F"), 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 FY2021, this report summarizes the research results of the "Challenge of novel hybrid-waste-solidification of mobile nuclei generated in Fukushima Nuclear Power Station and establishment of rational disposal concept and its safety assessment" conducted in FY2022. The present study aims to establish the rational waste disposal concept of a variety of wastes generated in 1F based on the hybrid-waste-solidification by the Hot Isostatic Press (HIP) method. The ceramics form with target elements, mainly iodine, which is difficult to immobilize, and Minor actinides such as Am, an alphaemitter and heat source, are HIPed with well-studied materials such as SUS and zircaloy, which make the long-term stability evaluation and safety assessment possible.
Yoshida, Kazuo; Hiyama, Mina*; Tamaki, Hitoshi
JAEA-Research 2024-007, 24 Pages, 2024/08
JAEA-Research-2024-007.pdf:2.1MB
An accident of evaporation to dryness by boiling of high-level radioactive liquid waste (HLLW) is postulated as one of the severe accidents caused by the loss of cooling function at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into the atmosphere. Accurate quantitative estimation of released Ru is one of the important issues for risk assessment of those facilities. It has been observed experimentally that volatility of RuO
is suppressed by HNO
generated by HNO
radiolysis. The analysis of chemical reactions of NO
including HNO and HNO in the waste tank is essential to simulate of these phenomena. To resolve this issue, an analytical approach has been attempted to couple dynamically two computer codes SHAWED and SCHERN. The simulation of boiling behavior in the tank is conducted with SHAWED. SCHERN simulates chemical behaviors of HNO, HNO and NO in the tank. A programmatic coupling algorithm and a trial simulation of the accident are presented in this report.
Yamagishi, Isao; Hato, Shinji*; Nishihara, Kenji; Tsubata, Yasuhiro; Sagawa, Yusuke*
JAEA-Data/Code 2024-002, 63 Pages, 2024/07
JAEA-Data-Code-2024-002.pdf:2.91MB
JAEA-Data-Code-2024-002-appendix(CD-ROM).zip:9.42MB
Adsorption columns filled with zeolite are used to treat contaminated water containing radioactive cesium generated by the Fukushima Daiichi Nuclear Power Station accident. As the contaminated water treatment progresses, the radioactive cesium in the adsorption column becomes highly concentrated, and the adsorption column becomes a high radiation source. To evaluate the radiation effects such as decay heat and radiolytic hydrogen production in the adsorption column, the concentration of radioactive cesium in the adsorption column is necessary, but since it is difficult to evaluate the concentration by measurement, it is estimated by simulation. In this research, a zeolite column adsorption dynamics simulation (Zeolite Adsorption Column: ZAC) code was developed to calculate the concentration of radioactive materials such as radioactive cesium in a zeolite filled adsorption column when they are injected into the column. The code was validated through comparison of calculation results with existing codes and experimental results of small column tests. This report presents the details of the model, the handling of the code, and the validity of the results for the developed code.
Pu
O powder using master sintering curve theoryNakamichi, Shinya; Sunaoshi, Takeo*; Hirooka, Shun; Vauchy, R.; Murakami, Tatsutoshi
Journal of Nuclear Materials, 595, p.155072_1 - 155072_11, 2024/07
Times Cited Count：1 Percentile：68.64(Materials Science, Multidisciplinary)Lan, Z.*; Arikawa, Yasunobu*; Mirfayzi, S. R.*; Morace, A.*; Hayakawa, Takehito*; Sato, Hirotaka*; Kamiyama, Takashi*; Wei, T.*; Tatsumi, Yuta*; Koizumi, Mitsuo; et al.
Nature Communications (Internet), 15, p.5365_1 - 5365_7, 2024/07
Times Cited Count：2 Percentile：76.47(Multidisciplinary Sciences)Irisawa, Eriko; Kato, Chiaki
Journal of Nuclear Materials, 591, p.154914_1 - 154914_10, 2024/04
Times Cited Count：3 Percentile：93.00(Materials Science, Multidisciplinary)The amount of corrosion of austenitic stainless-steel R-SUS304ULC was evaluated considering the changes in solution composition and boiling during actual concentration operations. Austenitic stainless-steel R-SUS304ULC is the structural material of the highly radioactive liquid waste concentrator in Japanese spent fuel reprocessing plant, which treats highly corrosive nitric acid solutions during enrichment operations. The study results show that it is necessary to focus on nitric acid concentrations, oxidizing metal ion concentrations, and decompression boiling as factors that accelerate the corrosion rate of stainless steel because of cathodic reaction activation.
Lei, Y.-J.*; Matsumura, Daiju; 15 of others*
Nature Communications (Internet), 15, p.3325_1 - 3325_12, 2024/04
Times Cited Count：24 Percentile：98.76(Multidisciplinary Sciences)Hata, Koji*; Niunoya, Sumio*; Aoyagi, Kazuhei; Miyara, Nobukatsu*
Journal of Rock Mechanics and Geotechnical Engineering, 16(2), p.365 - 378, 2024/02
Times Cited Count：3 Percentile：82.67(Engineering, Geological)Excavation of underground caverns, such as mountain tunnels and energy-storage caverns, may cause the damages to the surrounding rock as a result of the stress redistribution. In this influenced zone, new cracks and discontinuities are created or propagate in the rock mass. Therefore, it is effective to measure and evaluate the acoustic emission (AE) events generated by the rocks, which is a small elastic vibration, and permeability change. The authors have developed a long-term measurement device that incorporates an optical AE (O-AE) sensor, an optical pore pressure sensor, and an optical temperature sensor in a single multi-optical measurement probe (MOP). Japan Atomic Energy Agency has been conducting R&D activities to enhance the reliability of high-level radioactive waste (HLW) deep geological disposal technology. In a high-level radioactive disposal project, one of the challenges is the development of methods for long-term monitoring of rock mass behavior. Therefore, in January 2014, the long-term measurements of the hydro-mechanical behavior of the rock mass were launched using the developed MOP in the vicinity of 350 m below the surface at the Horonobe Underground Research Center. The measurement results show that AEs occur frequently up to 1.5 m from the wall during excavation. In addition, hydraulic conductivity increased by 2 to 4 orders of magnitude. Elastoplastic analysis revealed that the hydraulic behavior of the rock mass affected the pore pressure fluctuations and caused micro-fractures. Based on this, a conceptual model is developed to represent the excavation damaged zone (EDZ), which contributes to the safe geological disposal of radioactive waste.
Iwata, Yoshihiro; Miyabe, Masabumi; Akaoka, Katsuaki; Wakaida, Ikuo; Hasegawa, Shuichi*
Journal of the Optical Society of America B, 41(1), p.119 - 126, 2024/01
Times Cited Count：1 Percentile：59.97(Optics)Calcium Rydberg levels are of significant interest for efficient and isotope-selective resonance ionization of trace radionuclides such as calcium-41 (Ca). In this study, we report novel measurement data on the energy level shifts of calcium-43 (
Ca) for 4sns 
S
and 4s(n-1)d D (n=40, 45, 50, 55, 60) Rydberg levels due to hyperfine-induced singlet-triplet mixing specific to isotopes with an odd mass number.
states in the electronic structure of the intermediate-valence superconductor CeIr
Fujimori, Shinichi; Kawasaki, Ikuto; Takeda, Yukiharu; Yamagami, Hiroshi; Sasabe, Norimasa*; Sato, Yoshiki*; Shimizu, Yusei*; Nakamura, Ai*; Maruya, A.*; Homma, Yoshiya*; et al.
Electronic Structure (Internet), 5(4), p.045009_1 - 045009_7, 2023/11
Yamada, Raiki; Takahashi, Toshiro*; Ogita, Yasuhiro
Journal of Mineralogical and Petrological Sciences (Internet), 118(1), p.221219a_1 - 221219a_26, 2023/11
Times Cited Count：2 Percentile：39.89(Mineralogy)Oligocene to Miocene volcanic rocks from the Toyama basin of the SW Japan arc, that were formed during back-arc spreading in the Japan Sea, were examined to reveal their petrogeneses and temporal change of arc volcanism during the Japan Sea opening. We reported whole-rock major and trace element and Sr-Nd isotopic compositions of andesites and rhyolites (23-16 Ma) and quantitatively discussed their petrogenesis, based on comparison with the results of model calculations, in this paper. Main concluding remarks are as follows: (1) Rhyolite magmas were generated by crustal assimilation of basaltic to andesitic magmas. (2) Andesites consist of high-Mg andesite, high-Sr, and tholeiitic andesite, generated by interaction among slab fluid, slab melt, and crustal material. (3) Upwelling of the asthenospheric mantle into the mantle wedge caused melting of the subducting Pacific plate, and andesitic magmatism induced rhyolitic magmatism.
Tada, Kenichi; Endo, Tomohiro*
Journal of Nuclear Science and Technology, 60(11), p.1397 - 1405, 2023/11
Times Cited Count：1 Percentile：30.19(Nuclear Science & Technology)The probability table method is a well-known method for addressing self-shielding effects in the unresolved resonance region. A long computational time is required to generate the probability table. The effective way to reduce the generation time of the probability table is the reduction of the number of ladders. The purpose of this study is the estimation of the optimal number of ladders using the statistical uncertainty in the probability table. To this end, the statistical uncertainty quantification method of the probability table was developed and the convergence behavior of the statistical uncertainty was investigated. The product of the probability table and the average cross section was considered the target of the statistical uncertainty. The convergence rate was affected by the average level spacing and reduced neutron width. The generation time of the probability table was less than half when the input parameter was changed from the number of ladders to the tolerance value.
Hirooka, Shun; Horii, Yuta; Sunaoshi, Takeo*; Uno, Hiroki*; Yamada, Tadahisa*; Vauchy, R.; Hayashizaki, Kohei; Nakamichi, Shinya; Murakami, Tatsutoshi; Kato, Masato
Journal of Nuclear Science and Technology, 60(11), p.1313 - 1323, 2023/11
Times Cited Count：5 Percentile：84.10(Nuclear Science & Technology)Additive MOX pellets are fabricated by a conventional dry powder metallurgy method. NdO and SmO are chosen as the additive materials to simulate the corresponding soluble fission products dispersed in MOX. Shrinkage curves of the MOX pellets are obtained by dilatometry, which reveal that the sintering temperature is shifted toward a value higher than that of the respective regular MOX. The additives, however, promote grain growth and densification, which can be explained by the effect of oxidized uranium cations covering to a pentavalent state. Ceramography reveals large agglomerates after sintering, and Electron Probe Micro-Analysis confirms that inhomogeneous elemental distribution, whereas XRD reveals a single face-centered cubic phase. Finally, by grinding and re-sintering the specimens, the cation distribution homogeneity is significantly improved, which can simulate spent nuclear fuels with soluble fission products.
Morii, Shiori; Yomogida, Takumi; Asai, Shiho*; Ouchi, Kazuki; Oka, Toshitaka; Kitatsuji, Yoshihiro
Bunseki Kagaku, 72(10.11), p.441 - 448, 2023/10
Rapid analytical method for the determination of Zr-93 in radioactive wastes has been developed. Laser ablation (LA)-ICP-MS was applied to the analysis of Zr isotopes in simulated high-level radioactive waste (HLW). Sample preparation time was dramatically reduced by using a DGA resin as the adsorbent for Zr. Direct quantification of Zr isotopes in this resin sample was carried out by LA-ICP-MS. Laser settings were optimized to obtain a reliable isotope ratio of the sample by LA-ICP-MS. Quantification of Zr isotopes in the simulated HLW solution by isotope dilution mass spectrometry (IDMS) was examined. The amount of Zr-90 in the sample obtained by IDMS corresponded to a value calculated from the given concentration of Zr in the sample within uncertainty. Thus, this method can be applied for the quantification of Zr-93 in radioactive wastes.
