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Journal Articles

High-temperature oxidation failure in reactivity-initiated accidents; An Evaluation of failure criteria based on oxygen concentration from the previous NSRR experiments

Luu, V. N.; Taniguchi, Yoshinori; Udagawa, Yutaka; Katsuyama, Jinya

Nuclear Engineering and Design, 442, p.114222_1 - 114222_15, 2025/10

 Times Cited Count:0

Journal Articles

Methods for regulating depth of corrosion fissures in simulated fastener holes of 7050-T7451 aluminum alloy

Aoyama, Takahito; Choudhary, S.*; Pandaleon, A.*; Burns, J. T.*; Kokaly, M.*; Restis, J.*; Ross, J.*; Kelly, R. G.*

Corrosion, 81(6), p.609 - 621, 2025/06

JAEA Reports

Investigation of measurement accuracy of burnup reactivity of accelerator-driven system during normal operation

Katano, Ryota; Abe, Takumi; Cibert, H.*

JAEA-Research 2024-019, 22 Pages, 2025/05

JAEA-Research-2024-019.pdf:1.03MB

An accelerator-driven system (ADS) dedicated to transmutation of minor actinides (MAs) is driven in subcritical states. It is important for establishment of the subcriticality control of ADS to predict the burnup reactivity. To validate the prediction accuracy, the burnup reactivity, especially at the first cycle, must be measured with sufficient accuracy. In this study, we focus on Current-To-Flux (CTF) method. We have simulated the burnup reactivity monitoring during the ADS normal operation with the CTF method by performing fixed-source-burnup calculations using a continuous energy Monte Carlo code SERPENT2 with some tallies that models in-core fission chambers and have estimated its measurement uncertainty. We have clarified that the 10% biases of measure burnup reactivities appear independently of the burnup duration and their detector position dependence is particularly small in the outer region of the system.

Journal Articles

Investigation on multi-dimensional short-term behaviour through benchmark analysis of a large-volume sodium combustion experiment

Sonehara, Masateru; Okano, Yasushi; Uchibori, Akihiro; Oki, Hiroshi*

Journal of Nuclear Science and Technology, 62(5), p.403 - 414, 2025/05

 Times Cited Count:0 Percentile:0.00(Nuclear Science & Technology)

For sodium-cooled fast reactors, understanding sodium combustion behaviour is crucial for managing sodium leakage accidents. In this study, we perform benchmark analyses of the Sandia National Laboratories (SNL) T3 experiment using the multi-dimensional thermal hydraulic code AQUA-SF. Conducted in an enclosed space with a large vessel volume of 100 m$$^3$$ and a sodium mass flow rate of 1 kg/s, the experiment highlighted the multi-dimensional effects of local temperature increase shortly after sodium injection. This study aims to extend the capabilities of AQUA-SF by focusing on the simulation of these multi-dimensional temperature variations, in particular the formation of high temperature regions at the bottom of the vessel. The proposed models include the temporary stopping of sodium droplet ignition and spray combustion of sodium splash on the floor. Furthermore, it has been shown that additional heat source near the floor is essential to enhance the reproduction of the high temperature region at the bottom. Therefore, case studies including sensitivity analyses of spray cone angle and prolonged combustion of droplets on the floor are conducted. This comprehensive approach provides valuable insights into the dynamics of sodium combustion and safety measures in sodium-cooled fast reactors.

Journal Articles

Development of a method for the determination of spontaneous fission nuclides in irradiated fuel and applicability to Pu quantification in fuel debris by dual time neutron measurements

Nagatani, Taketeru; Kosuge, Yoshihiro*; Sagara, Hiroshi*; Nakaguki, Sho; Nomi, Takayoshi; Okumura, Keisuke

Progress in Nuclear Science and Technology (Internet), 7, p.41 - 46, 2025/05

Journal Articles

New filter concept for removal of fine particle generated in high level radioactive solution

Takahatake, Yoko; Watanabe, So; Watanabe, Masayuki; Sano, Yuichi; Takeuchi, Masayuki

Progress in Nuclear Science and Technology (Internet), 7, p.195 - 198, 2025/05

Extraction chromatgraphy technology for trivalent minor actinide (MA(III) ; Am(III) and Cm(III)) recovery from the solution generated by an extraction process in reprocessing of spent nuclear fuel has been developed. A fine particle is generated in the solution. The fine particle must be removed before MA recovery operation, because that leads clogging of the extraction chlomatography column. In order to prevent clogging the column, filtration system utilizing porous silica beads packed column has been designed. In this study, a fine particle trapping system was developed and particle removal performance of the system was experimentally evaluated using alumina particles as simulated fine particle. Column experiments revealed that the fine particle with the particle size from 0.12 to 15 $$mu$$m is cause of clogging of the filtration column. Since simulated fine particles were trapped on filtration experiments, a filtration system using the porous silica beads column is practical,

Journal Articles

Enhanced strength and ductility in an additively manufactured Al10SiMg alloy at cryogenic temperatures

Naeem, M.*; Rehman, A. U.*; Romero Resendiz, L.*; Salamci, E.*; Aydin, H.*; Ansari, P.*; Harjo, S.; Gong, W.; Wang, X.-L.*; 3 of others*

Communications Materials (Internet), 6, p.65_1 - 65_13, 2025/04

JAEA Reports

Elemental composition analysis of main structural materials of JMTR

Nagata, Hiroshi; Kochiyama, Mami; Chinone, Marina; Sugaya, Naoto; Nishimura, Arashi; Ishikawa, Joji; Sakai, Akihiro; Ide, Hiroshi

JAEA-Data/Code 2024-016, 44 Pages, 2025/03

JAEA-Data-Code-2024-016.pdf:3.54MB

The elemental composition of the structural materials of nuclear reactor facilities is used as one of the important parameters in activation calculations that are evaluated when formulating decommissioning plans. Regarding the elemental composition of aluminum alloys and other materials used as structural materials for test and research reactors, sufficient data is not available regarding elements other than the major elements. For this reason, samples were collected from aluminum alloy, beryllium, hafnium, and other materials that have been used as the main structural materials of JMTR (Japan Materials Testing Reactor), and their elemental compositions were analyzed. This report summarizes the elemental composition data of 78 elements obtained in FY2023.

Journal Articles

Built-in physics models and proton-induced nuclear data validation using MCNP, PHITS, and FLUKA; Impact on the shielding design for proton accelerator facilities

$c{C}$elik, Y.*; Stankovskiy, A.*; Iwamoto, Hiroki; Iwamoto, Yosuke; Van den Eynde, G.*

Annals of Nuclear Energy, 212, p.111048_1 - 111048_12, 2025/03

 Times Cited Count:1 Percentile:51.66(Nuclear Science & Technology)

Journal Articles

Strain analysis of thermoelectric materials using high-resolution synchrotron X-ray diffraction data

Nakasawa, Hayato*; Shobu, Takahisa; Tominaga, Aki; Fujii, Masashi*; Matsumoto, Hironari*; Matsuda, Michiko*; Shimada, Takeshi*; Trivedi, V.*; Tachibana, Makoto*; Tsujii, Naohito*; et al.

Funtai Oyobi Fummatsu Yakin, 72(Suppl.), p.S997 - S1001, 2025/03

Journal Articles

Measurements of neutron capture cross-section for nuclides of interest in decommissioning (II); $$^{58}$$Fe(n,$$gamma$$)$$^{59}$$Fe

Nakamura, Shoji; Shibahara, Yuji*; Endo, Shunsuke; Rovira Leveroni, G.; Kimura, Atsushi

Journal of Nuclear Science and Technology, 62(3), p.300 - 307, 2025/03

 Times Cited Count:0 Percentile:0.00(Nuclear Science & Technology)

Journal Articles

CFD analysis of thermal radiation effects on large containment CIGMA vessel with Weighted Sum of Gray Gases (WSGG) model

Hamdani, A.; Soma, Shu; Abe, Satoshi; Shibamoto, Yasuteru

Progress in Nuclear Science and Technology (Internet), 7, p.53 - 59, 2025/03

Journal Articles

Directional vector-based quick evaluation method for protective plate effects in X-ray fluoroscopy (DQPEX)

Hizukuri, Kyoko*; Fujibuchi, Toshio*; Han, D.*; Arakawa, Hiroyuki*; Furuta, Takuya

Radiological Physics and Technology, 18(1), p.196 - 208, 2025/03

One of the radiation protection measures for medical personnel engaged in X-ray fluoroscopy is the use of radiation-protective plates and a simulation tool to evaluate effect of the plates is desired. Monte Carlo simulation has an advantage of being able to accurately calculate the interaction between radiations and various objects present in the X-ray room. However, Monte Carlo simulation has a disadvantage of being computationally time-consuming. Therefore, we developed a new simplified method to calculate the dose distribution in a short time with the presence of protective plates using pre-computed directional vectors (SCV). Using the Monte Carlo code PHITS, we simulated the ambient dose equivalent distribution the X-ray fluoroscopy room without the presence of protective plates. Assuming the dose at each voxel was all contributed from radiations in the direction indicated by the directional vector, the shielding effect of the protective plates for the dose at the voxel was determined whether the line toward backtrace of the directional vector has a intersect with the protective plate or not. With SCV, the computational time for the whole dose distribution with the presence of a protective plate was reduced approximately 1/6000 of the full PHITS simulation keeping the good accuracy to evaluate the effect of the plate.

JAEA Reports

Evaluation report for sludge measurement by nondestructive assay (Plutonium Scrap Multiplicity Counter)(Joint research)

Tanigawa, Masafumi; Seya, Kazuhito*; Asakawa, Naoya*; Hayashi, Hiroyuki*; Horigome, Kazushi; Mukai, Yasunobu; Kitao, Takahiko; Nakamura, Hironobu; Henzlova, D.*; Swinhoe, M. T.*; et al.

JAEA-Technology 2024-014, 63 Pages, 2025/02

JAEA-Technology-2024-014.pdf:3.02MB

The liquid waste treatment process generated sludge items at the plutonium conversion development facility. They are highly heterogeneous and contain large amounts of impurities (Na, Fe, Ni etc.). Therefore, the sludge items have very large sampling uncertainty and so the total measurement uncertainty is very large (approximately 24%). The plutonium scrap multiplicity counter (PSMC) measurement technique for sludge items was developed by joint research between the Japan Atomic Energy Agency (JAEA) and Los Alamos National Laboratory (LANL). The technical validity for sludge items using the PSMC was evaluated using various types of sample measurements and Monte Carlo N-Particle transport code calculations. The PSMC measurement parameters were found to be valid for use with sludge items and the validity of multiplicity analysis was confirmed and demonstrated through comparisons with standard MOX powder and a standard sludge. As a result, the PSMC measurement values were shown to be consistent and reasonable and the large amount of impurity (Fe, Ni etc.) did not impact the results. Therefore, the measurement uncertainty of the improved nuclear material accountancy (NMA) procedure by combined PSMC and high-resolution gamma spectrometry was shown to be 6.5%. In addition, an acceptance test was conducted using PSMC/HRGS and IAEA benchmark equipment. Measured Pu mass by both equipment agrees within the measurement uncertainty of each method, and so the validity for Pu mass measurement by PSMC/HRGS was confirmed. The above results confirm the applicability of PSMC/HRGS as an additional NMA method for sludge and a newly designed NDA procedure based on this study is applied to sludge for NMA in PCDF.

Journal Articles

Two-group drift-flux model for upward cap-bubbly two-phase flows in large square channels

Sun, Haomin; Hibiki, Takashi*

International Journal of Heat and Mass Transfer, 237, p.126445_1 - 126445_14, 2025/02

 Times Cited Count:2 Percentile:36.85(Thermodynamics)

Journal Articles

Development of gas entrainment evaluation model based on distribution of pressure along vortex center line; Application to a gas entrainment experiment with traveling vortices in an open water channel flow?

Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki; Imai, Yasutomo*; Fujisaki, Tatsuya*; Sakai, Takaaki*

Nuclear Engineering and Design, 432, p.113785_1 - 113785_16, 2025/02

 Times Cited Count:1 Percentile:0.00(Nuclear Science & Technology)

Establishing an evaluation method for the gas entrainment (GE) of argon cover gas due to surface vortices is required in terms of safety design of sodium-cooled fast reactors. To modify the evaluation model in an in-house evaluation tool for GE, StreamViewer, a modified evaluation model on the pressure distribution along the vortex center line (PVL model) was proposed to identify the vortex center lines by connecting continuous vortex center points from the suction port to the surface and evaluate gas core length based on the balance between the hydrostatic pressure and the pressure decrease distribution along the vortex center line. PVL model was applied the three-dimensional numerical analysis results for the experiments where a plate induced unsteady traveling vortices in the open channel flow. Consequently, the GE evaluation using StreamViewer with PVL model could reproduce the relation between the inlet flow velocity and the gas core length in the unsteady vortex flow experiments.

Journal Articles

Study on the effect of radiation-resistant resin on water radiolysis

Ito, Tatsuya; Nagaishi, Ryuji; Kuwano, Ryo*; Godo, Masao*; Yoshida, Yoichi*

Radiation Physics and Chemistry, 226, p.112198_1 - 112198_5, 2025/01

 Times Cited Count:0 Percentile:0.00(Chemistry, Physical)

In recent years, the use of radiation-resistant resins of polyimide and polyether ether ketone becomes increasing as vessels for irradiation and unsealed radioisotope experiments. However, in our radiolysis experiments, the possibility of interaction between radiolysis products of water and the resin was found, suggesting concerns that the resin may affect reactions in water in radiation fields. To clarify the interaction, dichromate (Cr$$_{2}$$O$$_{7}$$$$^{2-}$$) reduction and hydrogen peroxide (H$$_{2}$$O$$_{2}$$) formation in $$gamma$$-radiolysis of water were compared with and without the resin. The Cr$$_{2}$$O$$_{7}$$$$^{2-}$$ reduction amount in aqueous solution with the resin became larger than that without the resin at the same dose, indicating the promotion of Cr$$_{2}$$O$$_{7}$$$$^{2-}$$ reduction by the resin. On the other hand, the H$$_{2}$$O$$_{2}$$ formation in pure water with and without an electron scavenger were almost independent of the presence of resin. These suggested the interaction between hydroxyl radical and the resin in contact with water in radiation fields.

Journal Articles

Evolution of radionuclide transport and retardation processes in uplifting granitic rocks, Part 2; Modelling coupled processes in uplift scenarios

Metcalfe, R.*; Benbow, S. J.*; Kawama, Daisuke*; Tachi, Yukio

Science of the Total Environment, 958, p.177690_1 - 177690_17, 2025/01

Uplifting fractured granitic rocks occur in substantial areas of countries such as Japan. A repository site would be selected in such an area only if it is possible to make a safety case, accounting for the changing conditions during uplift. The safety case must include robust arguments that chemical processes in the rocks around the repository will contribute sufficiently to minimise radiological doses to biosphere receptors. To provide confidence in the safety arguments, numerical models need to be sufficiently realistic, but also parameterised conservatively (pessimistically). However, model development is challenging because uplift involves many complex couplings between groundwater flow, chemical reactions between water and rock, and changing rock properties. The couplings would affect radionuclide mobilisation and retardation, by influencing diffusive radionuclide fluxes between groundwater flowing in fractures and effectively immobile porewater in the rock matrix and radionuclide partitioning between water and solid phases, via: (i) mineral precipitation/dissolution; (ii) mineral alteration; and (iii) sorption/desorption. It is difficult to represent all this complexity in numerical models while showing that they are parameterised conservatively. Here we present a modelling approach, illustrated by simulation cases for some exemplar radioelements, to identify realistically conservative process conceptualisations and model parameterisations.

Journal Articles

Integrity evaluation of boundary function of main components in nuclear plants during severe accidents

Tsukimori, Kazuyuki; Yada, Hiroki

Journal of Pressure Vessel Technology, 147, p.031901_1 - 031901_9, 2025/00

 Times Cited Count:0 Percentile:0.00(Engineering, Mechanical)

After the accident at the Fukushima Daiichi Nuclear Power Plant, very strict safety measures were implemented for nuclear power plants in Japan. It thus becomes a crucial issue if the safety of a plant is maintained or not at beyond design basis events. In this study, head plates and bellows were examined as components that compose the parts of the boundary of vessels that contain the primary coolant of a prototype fast breeder reactor. The behaviors of buckling, post-buckling deformation, and penetration failure, that is, loss of boundary function of these components with increasing pressure were investigated. The series of this research program started in FY2013 and the research proceeded step by step. The new result in this paper is the application of the proposed criteria to head plates and bellows, and a conservative estimation of penetration failure of these components is obtained.

Journal Articles

Possible criticality scenario and its mechanism of the Windscale Works criticality accident in 1970 analyzed by computational fluid dynamics and Monte Carlo neutron transport

Fukuda, Kodai

Annals of Nuclear Energy, 208(1), p.110748_1 - 110748_10, 2024/12

 Times Cited Count:1 Percentile:51.66(Nuclear Science & Technology)

2533 (Records 1-20 displayed on this page)