Total and double differential scattering cross-section measurements of isotropic graphite

Kimura, Atsushi; Endo, Shunsuke; Nakamura, Shoji

EPJ Web of Conferences, 294, p.01002_1 - 01002_7, 2024/04

https://doi.org/10.1051/epjconf/202429401002

Overview of development program for engineering scale extraction chromatography MA(III) recovery system

Watanabe, So; Takahatake, Yoko; Hasegawa, Kenta; Goto, Ichiro*; Miyazaki, Yasunori; Watanabe, Masayuki; Sano, Yuichi; Takeuchi, Masayuki

Mechanical Engineering Journal (Internet), 11(2), p.23-00461_1 - 23-00461_10, 2024/04

https://doi.org/10.1299/mej.23-00461

Investigations on distribution of radioactive substances owing to the Fukushima Daiichi Nuclear Power Station Accident in the fiscal year 2022 (Contract research)

Group for Fukushima Mapping Project

JAEA-Technology 2023-024, 176 Pages, 2024/03

JAEA-Technology-2023-024.pdf:22.16MB

This report presents results of the investigations on the distribution-mapping project of radioactive substances owing to TEPCO Fukushima Daiichi Nuclear Power Station (FDNPS) conducted in FY2022. Car-borne surveys, a measurement using survey meters, a walk survey and an unmanned helicopter survey were carried out to obtain air dose rate data to create their distribution maps, and temporal changes of the air dose rates were analyzed. Surveys on depth profile of radiocesium and in-situ measurements as for radiocesium deposition were performed. Based on these measurement results, effective half-lives of the temporal changes in the air dose rates and the deposition were evaluated. Score maps to classify the importance of the measurement points were created, and the factors causing changes in the score when monitoring data from multiple years were used were discussed. The range of fluctuation of past tritium concentration data in seawater was determined, and the causes of the fluctuation were discussed. Monitoring data in coastal area performed in 2022 owing to the comprehensive radiation monitoring plan was summarized, and temporal changes in cesium-137 were analyzed. Using the Bayesian hierarchical modeling approach, we obtained maps that integrated air dose rate distribution data acquired through surveys such as car-borne and walk surveys with respect to the region within 80 km from the FDNPS and Fukushima Prefecture. The measurement results for FY2022 were published on the "Database for Radioactive Substance Monitoring Data", and measurement data were stored as CSV format. Radiation monitoring and analysis of environmental samples owing to the comprehensive radiation monitoring plan were carried out.

Standard guideline for the seismic response analysis method using three-dimensional finite element model of reactor buildings (Contract research) (Translated document)

Choi, B.; Nishida, Akemi; Kawata, Manabu; Shiomi, Tadahiko; Li, Y.

JAEA-Research 2024-001, 206 Pages, 2024/03

JAEA-Research-2024-001.pdf:9.12MB

In the assessment of seismic safety and the design of building structures in nuclear facilities, lumped mass models have been used as standard methods. Recent advances in computer capabilities allow the use of three-dimensional finite element (3D FE) models to account for the 3D behavior of buildings, material nonlinearity, and the nonlinear soil-structure interaction effect. While 3D analysis method has many advantages, it is necessary to ensure its reliability as a new approach. The International Atomic Energy Agency performed an international benchmark study using the 3D FE analysis model for reactor building of Unit 7 at TEPCO's Kashiwazaki-Kariwa Nuclear Power Station based on recordings from the Niigataken Chuetsu-oki Earthquake in 2007. Multiple organizations from different countries participated in this study and the variation in their analytical results was significant, indicating an urgent need to improve the reliability of the analytical results by standardization of the analytical methods using 3D FE models. Additionally, it has been pointed out that it is necessary to understand the 3D behavior in the seismic fragility assessment of buildings and equipment, using realistic seismic response analysis method based on 3D FE models. In view of these considerations, a guideline for the seismic response analysis method using a 3D FE model was developed by incorporating the latest knowledge and findings in this area. The purpose of the guideline is to improve the reliability of the seismic response analysis method using 3D FE model of reactor buildings. The guideline consists of a main body, commentaries, and appendixes. The standard procedures, recommendations, key points to note, and technological bases for conducting seismic response analysis on reactor buildings using 3D FE models are provided in the guideline. In addition, the guideline will be revised reflecting the latest knowledge.

An Analytical model to decompose mass transfer and chemical process contributions to molecular iodine release from aqueous phase under severe accident conditions

Zablackaite, G.; Shiotsu, Hiroyuki; Kido, Kentaro; Sugiyama, Tomoyuki

Nuclear Engineering and Technology, 56(2), p.536 - 545, 2024/02

https://doi.org/10.1016/j.net.2023.10.030

Preliminary study of the criticality monitoring method based on the simulation for the activity ratio of short half-life noble-gas fission products from fuel debris

Riyana, E. S.; Okumura, Keisuke; Sakamoto, Masahiro; Matsumura, Taichi; Terashima, Kenichi; Kanno, Ikuo

Journal of Nuclear Science and Technology, 8 Pages, 2024/00

https://doi.org/10.1080/00223131.2023.2300773

Chiral Dirac fermion in a collinear antiferromagnet

Zhang, A.*; Deng, K.*; Sheng, J.*; Liu, P.*; Kumar, S.*; Shimada, Kenya*; Jiang, Z.*; Liu, Z.*; Shen, D.*; Li, J.*; et al.

Chinese Physics Letters, 40(12), p.126101_1 - 126101_8, 2023/12

https://doi.org/10.1088/0256-307X/40/12/126101

Effect of fuel particle size on consequences of criticality accidents in water-moderated solid fuel particle dispersion system

Fukuda, Kodai; Yamane, Yuichi

Journal of Nuclear Science and Technology, 60(12), p.1514 - 1525, 2023/12

https://doi.org/10.1080/00223131.2023.2224327

This study aims to clarify the effect of fuel particle radius on the criticality transient behavior and the total number of fissions in water-moderated solid fuel dispersion systems. Neutronics/thermal hydraulics-coupled kinetics analysis was performed in a hypothetical fuel debris system, where small fuel particles aggregate in water and become supercritical. Results showed that the number of fissions is 10 times larger when the fuel particle radius is reduced by one order of magnitude under conditions where heat transfer, i.e. from fuel to water, is emphasized. Moreover, there is a possibility that lower reactivity could give a larger number of fissions when the fuel particle size is very small. In addition, the number of fissions may be overestimated or underestimated to an unexpected extent unless appropriate fuel particle size is set on the analysis.

Magnetic and fermi surface properties of semimetals EuAs and Eu(AsP)

Onuki, Yoshichika*; Karube, Kosuke*; Aoki, Dai*; Nakamura, Ai*; Homma, Yoshiya*; Matsuda, Tatsuma*; Haga, Yoshinori; Takeuchi, Tetsuya*

Journal of the Physical Society of Japan, 92(11), p.114703_1 - 114703_12, 2023/11

https://doi.org/10.7566/JPSJ.92.114703

Upgrade of seismic design procedure for piping systems based on elastic-plastic response analysis

Nakamura, Izumi*; Otani, Akihito*; Okuda, Yukihiko; Watakabe, Tomoyoshi; Takito, Kiyotaka; Okuda, Takahiro; Shimazu, Ryuya*; Sakai, Michiya*; Shibutani, Tadahiro*; Shiratori, Masaki*

Dai-10-Kai Kozobutsu No Anzensei, Shinraisei Ni Kansuru Kokunai Shimpojiumu (JCOSSAR2023) Koen Rombunshu (Internet), p.143 - 149, 2023/10

https://doi.org/10.60316/jcossar.10.0_143

In 2019, the JSME Code Case for seismic design of nuclear power plant piping systems was published. The Code Case provides the strain-based fatigue criteria and detailed inelastic response analysis procedure as an alternative design rule to the current seismic design, which is based on the stress evaluation by elastic response analysis. In 2022, it was approved to revise the Code Case with improving the cycle counting method for fatigue evaluation to the Rain flow method. In addition, the discussion to incorporate the elastic-plastic behavior of support structures is now in progress for the next revision of the Code Case. This paper discusses the contents and background of the 2022 revision, the progress of the next revision, and future tasks.