Hydraulic modeling of saltwater infiltration with various concentrations into unsaturated bentonite-based buffer material

Takubo, Yusaku*; Takayama, Yusuke*; Sugita, Yutaka; Ogoshi, Minori; Ishida, Keisuke*

Environmental Earth Sciences, 85(9), p.229_1 - 229_19, 2026/05

https://doi.org/10.1007/s12665-026-12955-9

None

Koike, Ayaka*; Takubo, Yusaku*; Ishida, Keisuke*; Mihara, Morihiro

NUMO-TR-25-03, p.100 - 104, 2025/10

no abstracts in English

Sophistication of seismic performance evaluation for plant structures utilizing finite element analysis of assembly modelling

Satoda, Akira*; Matsukawa, Keisuke*; Guo, Z. H.*; Choi, B.; Nishida, Akemi

Transactions of the 28th International Conference on Structural Mechanics in Reactor Technology (SMiRT28) (Internet), 10 Pages, 2025/08

In order to contribute to the seismic safety assessment of nuclear power plants and other industrial facilities against large earthquakes, it is an important issue to realistically capture the seismic behavior of plant structures and enable practical response analyses. Among the structural features that significantly influence seismic behavior, joints play a particularly critical role. In the case of steel pipe support structures (hereafter referred to as pipe racks), the joints connecting members (hereafter referred to as joints) have conventionally been modeled by empirical approaches, often idealized as pinned or rigid, leading to conservative evaluations. The final objective of this study is to develop a joint modeling method that reproduces more realistic behavior by utilizing three-dimensional detailed models of joints. To date, using the developed three-dimensional detailed analysis techniques, we have evaluated realistic semi-rigid stiffness of joints in both elastic and elasto-plastic ranges, proposed simplified joint models, and reported the obtained results. Furthermore, three-dimensional detailed analyses of an entire pipe rack including joints have been conducted, demonstrating the possibility of simultaneously capturing both the global seismic response of the pipe rack and the local joint behavior. In this paper, the simplified joint model proposed in previous studies is applied to the pipe rack joints modeled with conventional beam elements used in design practice, and the analysis results are compared with those of the detailed three-dimensional analysis. The findings are organized to clarify the differences and applicability. This enables improvement in the accuracy of practical seismic response analysis methods using beam elements. By applying the obtained results to the modeling of joints in steel structures of plant facilities, more rational seismic safety assessments of nuclear facilities and other plant structures can be expected.

Development of radionuclide release model for safety assessment of TRU waste disposal

Koike, Ayaka*; Ishida, Keisuke*; Hamamoto, Takafumi*; Mihara, Morihiro

NUMO-TR-24-01, p.98 - 101, 2024/05

no abstracts in English

Advanced techniques for evaluating coupled Thermal-Hydraulic-Mechanical-Chemical (THMC) phenomena using in-situ test data

Takubo, Yusaku*; Takayama, Yusuke; Ishida, Keisuke*; Fujisaki, Kiyoshi*

NUMO-TR-24-01, p.109 - 112, 2024/05

no abstracts in English

None

Hamamoto, Takafumi*; Ishida, Keisuke*; Tachi, Yukio

NUMO-TR-22-02, p.62 - 64, 2023/03

https://www.numo.or.jp/technology/technical_report/NUMO-TR-22-02.pdf

no abstracts in English

None

Onoe, Hironori*; Saegusa, Hiromitsu*; Ishida, Keisuke*; Fujisaki, Kiyoshi*; Sawada, Atsushi

NUMO-TR-22-02, p.78 - 80, 2023/03

https://www.numo.or.jp/technology/technical_report/NUMO-TR-22-02.pdf

no abstracts in English

None

Takubo, Yusaku*; Takayama, Yusuke; Ichikawa, Nozomi*; Ishida, Keisuke*; Fujisaki, Kiyoshi*

NUMO-TR-22-02, p.68 - 71, 2023/03

https://www.numo.or.jp/technology/technical_report/NUMO-TR-22-02.pdf

no abstracts in English

None

Hamamoto, Takafumi*; Ishida, Keisuke*; Ishidera, Takamitsu

NUMO-TR-22-02, p.58 - 61, 2023/03

https://www.numo.or.jp/technology/technical_report/NUMO-TR-22-02.pdf

no abstracts in English

Investigation of physical properties of glove for glove-box and estimation of its life-time

Kobayashi, Daisuke; Yamamoto, Masahiko; Nishida, Naoki; Miyoshi, Ryuta; Nemoto, Ryo*; Hayashi, Hiroyuki*; Kato, Keisuke; Nishino, Saki; Kuno, Takehiko; Kitao, Takahiko; et al.

Nihon Hozen Gakkai Dai-18-Kai Gakujutsu Koenkai Yoshishu, p.237 - 240, 2022/07

All gloves attached to glove-box in Tokai Reprocessing Plant have a fixed expiration date and have to be replaced every 4-year. However, degrees of glove deterioration are different depending on its usage environment (frequency, chemicals, radiation, etc.), because of rubber products. Therefore, physical properties such as tensile strength, elongation, hardness of gloves are measured, and the life-time of gloves are estimated. As a result, gloves without any defects in its appearance have enough physical property for acceptance criteria of new glove. The extrapolated physical property of glove is sufficiently larger than the reported values of damaged glove. No deterioration in physical properties of gloves, that are periodically replaced without any defects in its appearance, is observed and the usable life-time of the glove is estimated to be 8 years.