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Dechenaux, B.*; Brovchenko, M.*; Araki, Shohei; Gunji, Satoshi; Suyama, Kenya
Annals of Nuclear Energy, 223, p.111555_1 - 111555_11, 2025/12
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)
-contamination visualization (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development ProjectCollaborative Laboratories for Advanced Decommissioning Science; Hokkaido University*
JAEA-Review 2025-021, 63 Pages, 2025/10
JAEA-Review-2025-021.pdf:5.71MB
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 of elemental technologies of hand-foot-cloth monitors for -contamination visualization" conducted in FY2023. The present study aims to develop hand-foot-monitors for -contamination visualization and cloth monitors for /
-contamination visualization consisting of a portable phoswich detector. ZnS(Ag) thick films by AD method and rare earth complexes have been studied for development of -ray scintillator materials. The scintillator properties of the newly prepared ZnS(Ag) thick films were improved from those prepared in 2022. A rare earth complex shows strong emission intensity under -ray irradiation, which was 12.5 times higher than that of a commercially available plastic scintillator (Saint-Gobain, BC400). By optimizing the manufacturing process conditions (molding die, sintering conditions, cutting process, annealing conditions, grinding/polishing processes) for La-GPS polycrystalline thin plates, the preparing process for 50 mm square La-GPS was established. The prepared La-GPS provided excellent performance for -ray scintillators. The cloth monitors for /-contamination visualization were also improved for the reflection of the actual situation. Furthermore, the basic performance of the prototype cloth monitors was evaluated, and alpha-ray energy and position distribution information were obtained. In an evaluation test of the phoswich detector, a precise discrimination between - and -rays was achieved.
Vauchy, R.; Horii, Yuta; Hirooka, Shun; Akashi, Masatoshi; Sunaoshi, Takeo*; Nakamichi, Shinya; Saito, Kosuke
Journal of Nuclear Materials, 616, p.156115_1 - 156115_16, 2025/10
Collaborative Laboratories for Advanced Decommissioning Science; Osaka University*
JAEA-Review 2025-019, 95 Pages, 2025/09
JAEA-Review-2025-019.pdf:9.49MB
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 (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 "Improvement of aerosol time-of-flight mass spectrometer for on-line measurement of tiny particles containing alpha emitters" conducted from FY2021 to FY2023. The present study aims to improve Aerosol Time-Of-Flight Mass Spectrometer (ATOFMS) in order to monitor tiny particles containing alpha emitters such as U and Pu which were generated in removing debris from the reactors of 1F. We newly fabricated the improved ATOFMS quipped with a reflectron and carried out measurements for modeled tiny particles containing U. In obtained TOF spectra, ion peaks were observed for Zr
, 
U, and their oxides as well as Zr
and U. Mass resolution of the ion peak of U+ was 1,700, which demonstrates that the improved ATOFMS has sufficient mass resolution to distinguish 
Pu from U. In the development of the apparatus for preparing enriched and enlarged particles, we fabricated the apparatus consisting of PILS, a volume reduction tube, a supersonic atomizer, and an online dryer, and optimized apparatus conditions. In the optimized conditions, enlarged particles with size between 0.4 
m and 0.8 m which are detectable with ATOFMS were dominantly produced. By analyzing the enlarged particles, these were produced by taking component elements of the apparatuses used in the enlarged process. The efficiency was evaluated to be 4.5 times. From these developments, the detection concentration limits of the apparatus were evaluated to be 7.0
10
, 4.210
, and 1.310
Bq/cm
for U, 
U, and Pu, respectively. These values are below the air concentration limit.
Naganuma, Masayuki; Ikusawa, Yoshihisa; Shuji, Yoshiyuki; Suzuki, Kiichi; Yamada, Yoshikazu; Kamiya, Masayoshi
JAEA-Research 2025-006, 165 Pages, 2025/09
JAEA-Research-2025-006.pdf:5.93MB
As a study for advancing LWR MOX fuel, the fuel concept that can contribute to effective plutonium utilization (e.g. reduction of the number of plu-thermal plants required) and reduction of spent fuel subassemblies (interim storage subassemblies) by using existing reactors was investigated. Specifically, since an increase of Pu loading is effective for the above purposes, MOX fuel candidate concepts with the potential to increase Pu loading in the range of the current MOX fuel guidelines (Pu content: 
13 wt%, burnup: 45 GWd/t, MOX fuel loading: 1/3) for PWRs were identified and compared in terms of "core and fuel design", "front-end", and "back-end", and the promising fuel concept was selected. Consequently, it was found that placing fuel elements with burnable poisons in the periphery (mainly in the corners) and adjusting the power peaking in the subassembly can increase the Pu content of the fuel elements in the periphery compared to the existing MOX fuel, which is effective in increasing the total Pu loading. Based on this measures, several fuel candidate concepts were devised, then each fuel specification that maintain criticality and power peaking equivalent to the existing MOX fuel were evaluated. As a result of the comparison of the characteristics of each candidate, the fuel concept in which UO
-Gd fuel is loaded near the corners was conclusively selected as the most promising concept, because it can increase Pu loading by approximately 15% compared to the existing MOX fuel core and has a lower development burden. Moreover, schematic evaluations were conducted for this fuel concept using the Nuclear Material Balance Analysis Code, confirming the quantitative prospect on how much the above increase in Pu loading would actually affect the number of required plu-thermal plants and the material balance of nuclear fuel cycle.
Watanabe, Taku*; Maejima, Yui*; Ueda, Yuki; Motokawa, Ryuhei; Takabatake, Ai*; Takeda, Shinichi*; Fudoji, Hiroshi*; Kishikawa, Keiki*; Koori, Michinari*
Langmuir, 41(34), p.22762 - 22773, 2025/09
Times Cited Count：0The assembled structures of melanin particles, i.e., colloidal particles coated with a melanin-like polydopamine (PDA) layer, create vivid structural colors. While the thickness of the PDA layer influences the particle arrangement and optical properties, the underlying mechanism has remained controversial. We demonstrate that the water swelling characteristics of PDA are crucial factors governing the dispersion and aggregation of these particles in solution. Detailed comparisons between dry and wet conditions revealed that the PDA layer readily absorbs water molecules, which leads to significant swelling in the thicker layers. The swelling of the PDA layers determined whether the particles remained dispersed or partially aggregated in the water, ultimately controlling the particle arrangement in the dry state once the water evaporated. These findings provide insights into the self-assembly of colloidal particles and offer a strategy for tuning the periodic particle order. This feature is pivotal for various applications in optical and sensing technologies.
Shikaze, Yoshiaki; Saito, Kimiaki; Tanimura, Naoki*; Yoshimura, Kazuya; Liu, X.; Machida, Masahiko
Radiation Protection Dosimetry, 201(15), p.1025 - 1042, 2025/09
Times Cited Count：0The two-component model, comprising a fast-decay and a slow-decay component, has been widely used to approximate the decreasing trends of air dose rates in contaminated areas surrounding major nuclear accident sites. However, its adequacy is yet to be thoroughly validated. This study analyzed extensive car-borne survey data collected from 2011 to 2016 after the Fukushima Daiichi Nuclear Power Plant accident using the least absolute shrinkage and selection operator regression with a high-degree-of-freedom model. This analysis aimed to evaluate the adequacy of the two-component model and investigate the profiles of ecological half-lives. Next, future predictions of air dose rate distributions were made using a prediction model formula that incorporated the average ecological half-life profiles calculated for each land-use and initial air dose rate category. Prediction accuracy was verified through comparison with integrated map data, which merge air dose rate datasets obtained using different monitoring methods and represent the most currently reliable source. In this paper, we present the results of the analysis of the above environmental half-life profiles and the evaluation of the predictive model calculations, and discuss the reasons that led to these results.
Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*
JAEA-Review 2025-004, 186 Pages, 2025/07
JAEA-Review-2025-004.pdf:11.9MB
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 FY2021, this report summarizes the research results of the "Development of a hybrid method for evaluating the long-term structural soundness of nuclear reactor buildings using response monitoring and damage imaging technologies" conducted from FY2021 to FY2023. The present study aims to develop an evaluation method necessary to obtain a perspective on the longterm structural soundness of accident-damaged reactor buildings, where accessibility to work sites is extremely limited due to high radiation dose rate and high contamination. In FY2023, the final year of the three-year project, experimental and analytical research activities were performed to develop, (1) Method for evaluating the building by monitoring the response to earthquakes and other disturbances, (2) Damage detection technology for concrete structures using electromagnetic waves, (3) Evaluation method for concrete materials and structures based on damage detection information, (4) Comprehensive soundness evaluation method and a long-term maintenance plan, (5) Promotion of the research. Expected results and final goals are achieved based on the outcomes including achievements up to FY2022.
Nagasumi, Satoru; Hasegawa, Toshinari; Nakagawa, Shigeaki; Kubo, Shinji; Iigaki, Kazuhiko; Shinohara, Masanori; Saikusa, Akio; Nojiri, Naoki; Saito, Kenji; Furusawa, Takayuki; et al.
JAEA-Research 2025-005, 23 Pages, 2025/07
JAEA-Research-2025-005.pdf:2.68MB
A safety demonstration test under abnormal operating conditions using the HTTR (High Temperature Engineering Test Reactor) was conducted to demonstrate safety features of the HTGRs (High Temperature Gas-cooled Reactors). Under a simulation of a control rod shutdown failure, all primary helium gas circulators were intentionally stopped during a steady-state operation at 100% reactor thermal power (30 MW), temporal changes of the reactor power and temperatures around the reactor pressure vessel (RPV) were obtained after the complete loss of forced heat removal from the reactor core. After the event (primary coolant flow stopped), the reactor power quickly decreased due to the negative reactivity feedback associated with the core temperature rise, and then the reactor power spontaneously shifted to a stable state of low power (about 1.2%) even after a recriticality. Heat dissipation from RPV surface to a surrounding vessel cooling system (water-cooled panels) ensured the amount of heat removal required to maintain the reactor temperature constant in the low power state. In this way, the transition from the event occurrence to the stable and safety state, i.e., inherent safety features of HTGRs, were demonstrated in the case of core forced cooling loss without active shutdown operations.
Hirooka, Shun; Vauchy, R.; Horii, Yuta; Sunaoshi, Takeo*; Saito, Kosuke; Ozawa, Takayuki
Proceedings of Workshop on Fuel Performance Assessment and Behaviour for Liquid Metal Cooled Fast Reactors (Internet), 8 Pages, 2025/07
no abstracts in English
Hamdani, A.; Soma, Shu; Abe, Satoshi; Shibamoto, Yasuteru
Progress in Nuclear Energy, 185, p.105771_1 - 105771_13, 2025/07
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Kinase, Masami
Radioisotopes, 74(2), p.233 - 238, 2025/07
no abstracts in English
Collaborative Laboratories for Advanced Decommissioning Science; The University of Tokyo*
JAEA-Review 2025-001, 94 Pages, 2025/06
JAEA-Review-2025-001.pdf:6.21MB
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 FY2019, this report summarizes the research results of the "Human resource development related to remote control technology for monitoring inside RPV pedestal during retrieval of fuel debris" conducted from FY2019 to FY2023. The present study aims to construct a monitoring platform for understanding the status inside a reactor during fuel debris removal, and measurement and visualization by sensors moving on the platform. In addition, to develop research personnel through research education by participating in such research projects, classroom lectures, and facility tours is also a goal of this project. In FY2023, along with the verification of each system, a three-dimensional reconstruction model was generated using images acquired from a moving camera on the monitoring platform in a simulated environment, and an integrated experiment was conducted to demonstrate that it is possible to present images from the optimal viewpoint for the visualization target, with the cooperation of each research theme.
Yoshida, Kazuo; Hiyama, Mina*; Tamaki, Hitoshi
JAEA-Research 2025-003, 24 Pages, 2025/06
JAEA-Research-2025-003.pdf:2.06MB
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 (RuO
) 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. RuO is expected to be absorbed chemically into water dissolving nitrous acid. Condensation of mixed vapor plays an important role for Ru transporting behavior in the facility building. The thermal-hydraulic behavior in the facility building is simulated with MELCOR code. The latent heat, which is a governing factor for vapor condensing behavior, has almost same value for nitric acid and water at the temperature range under 120 centigrade. Considering this thermal characteristic, it is assumed that the amount of nitric acid is substituted with mole-equivalent water in MELCOR simulation. Compensating modeling induced deviation by this assumption have been assembled with control function features of MELCOR. The comparison results have been described conducted between original simulation and modified simulation with compensating model in this report. It has been revealed that the total amount of pool water in the facility was as same as both simulations.
Yanagisawa, Hiroshi; Motome, Yuiko
JAEA-Research 2025-001, 99 Pages, 2025/06
JAEA-Research-2025-001.pdf:1.98MB
The detailed computational models for nuclear criticality analyses on the first startup cores of NSRR (Nuclear Safety Research Reactor), which is categorized as a TRIGA-ACPR (Annular Core Pulse Reactor), were created for the purposes of deeper understandings of safety inspection data on the neutron absorber rod worths of reactivity and improvement of determination technique of the reactivity worths. The uncertainties in effective neutron multiplication factor (k
) propagated from errors in the geometry, material, and operation data for the present models were evaluated in detail by using the MVP version 3 code with the latest Japanese nuclear data library, JENDL-5, and the previous versions of JENDL libraries. As a result, the overall uncertainties in k for the present models were evaluated to be in the range of 0.0027 to 0.0029 
k. It is expected that the present models will be utilized as the benchmark on k for TRIGA-ACPR. Moreover, it is confirmed that the overall uncertainties were sufficiently smaller than the values of absorber rod worths determined in NSRR. Thus, it is also considered that the present models are applicable to further analyses on the absorber rod worths in NSRR.
Shimada, Asako; Hemmi, Ko; Ohira, Saki; Iida, Yoshihisa
Analytical Sciences, 9 Pages, 2025/06
Times Cited Count：0 Percentile：0.00(Chemistry, Analytical)Sugita, Yutaka; Ono, Hirokazu; Beese, S.*; Pan, P.*; Kim, M.*; Lee, C.*; Jove-Colon, C.*; Lopez, C. M.*; Liang, S.-Y.*
Geomechanics for Energy and the Environment, 42, p.100668_1 - 100668_21, 2025/06
Times Cited Count：1 Percentile：77.92(Energy & Fuels)The international cooperative project DECOVALEX 2023 focused on the Horonobe EBS experiment in the Task D, which was undertaken to study, using numerical analyses, the thermo-hydro-mechanical (or thermo-hydro) interactions in bentonite based engineered barriers. One full-scale in-situ experiment and four laboratory experiments, largely complementary, were selected for modelling. The Horonobe EBS experiment is a temperature-controlled non-isothermal experiment combined with artificial groundwater injection. The Horonobe EBS experiment consists of the heating and cooling phases. Six research teams performed the THM or TH (depended on research team approach) numerical analyses using a variety of computer codes, formulations and constitutive laws.
Birkholzer, J. T.*; Graupner, B. J.*; Harrington, J.*; Jayne, R.*; Kolditz, O.*; Kuhlman, K. L.*; LaForce, T.*; Leone, R. C.*; Mariner, P. E.*; McDermott, C.*; et al.
Geomechanics for Energy and the Environment, 42, p.100685_1 - 100685_17, 2025/06
Times Cited Count：1 Percentile：0.00(Energy & Fuels)Ohashi, Tomonori*; Sakamaki, Tatsuya*; Funakoshi, Kenichi*; Steinle-Neumann, G.*; Hattori, Takanori; Yuan, L.*; Suzuki, Akio*
Journal of Mineralogical and Petrological Sciences (Internet), 120(1), p.240926a_1 - 240926a_13, 2025/06
Times Cited Count：0 Percentile：0.00(Mineralogy)We explore the structures of dry and hydrated (H
O and DO) Na
Si
O
melt at 0-6 GPa and 1000-1300 K and glasses recovered from high pressure and temperatures by in-situ neutron and X-ray diffraction. The structures of the melts at 0-10 GPa and 3000 K are also investigated by ab-initio molecular dynamics simulation. In-situ neutron experiments revealed that the D-O distance increases with compression due to the formation of -O-D-O- bridging species, which is reproduced by the molecular dynamics simulations. The pressure-induced -O-D-O- formation reflects a more rigid incorporation of hydrogen, which acts as a mechanism for the experimentally observed higher solubility of water in silicate melts. Together with shrinking modifier domains, this process dominates the compression behavior of hydrous NaSiO melt, whereas the compression of dry NaSiO at 0-10 GPa and 3000 K is governed largely by bending of the Si-O-Si angle. The molecular dynamics simulations on hydrous NaSiO melts further suggest that the sodium ions are scavenged from its network-modifying role via 2(![$$^{[4]}$$](/search/images/ERPHWWZULV4SI.gif)
Si-O
+ Na
) 
Si-(O-![$$^{[5]}$$](/search/images/ERPHWWZVLV4SI.gif)
Si-O)
+ 2Na and Si-O + Na + Si-OH Si-(O-H-O-Si) + Na with increasing pressure.
Takei, Hayanori
Journal of Nuclear Science and Technology, 45 Pages, 2025/06
Times Cited Count：0The Japan Atomic Energy Agency is working on the research and development of an accelerator-driven nuclear transmutation system (ADS) for transmuting minor actinides. This system combines a subcritical nuclear reactor with a high-power superconducting proton linear accelerator (JADS-linac). One of the factors limiting the advancement of the JADS-linac is beam trips, which often induce thermal cycle fatigue, thereby damaging the components in the subcritical core. The average beam current of the JADS-linac is 32 times higher than that of the linear accelerator (linac) of the Japan Proton Accelerator Research Complex (J-PARC). Therefore, according to the development stage, comparing the beam trip frequency of the JADS-linac with the allowable beam trip frequency (ABTF) is necessary. Herein the beam trip frequency of the JADS-linac was estimated through a Monte Carlo program using the reliability functions based on the operational data of the J-PARC linac. The Monte Carlo program afforded the distribution of the beam trip duration, which cannot be obtained using traditional analytical methods. Results show that the frequency of the beam trips with a duration exceeding 5 min must be reduced to 27% of the current J-PARC linac level to be below the ABTF.
