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, 61(2), p.269 - 276, 2024/02

https://doi.org/10.1080/00223131.2023.2300773

Relationship between internal stress distribution and microstructure in a suspension-sprayed thermal barrier coating with a columnar structure

Yamazaki, Yasuhiro*; Shinomiya, Keisuke*; Okumura, Tadaharu*; Suzuki, Kenji*; Shobu, Takahisa; Nakamura, Yuiga*

Quantum Beam Science (Internet), 7(2), p.14_1 - 14_12, 2023/05

https://doi.org/10.3390/qubs7020014

Proposal on how to proceed with Verification and Validation of radiation shielding analyses

Okumura, Keisuke; Sakamoto, Yukio*; Tsukiyama, Toshihisa*

Shahei Kaiseki No V&V Gaidorain Sakutei Ni Mukete, p.4 - 8, 2023/03

https://www.aesj.net/uploads/com_vvshieldingcalc20230428_sup.pdf

no abstracts in English

Issues and proposals for activation calculation of reactor decommissioning using recent evaluated nuclear data library

Okumura, Keisuke

Kaku Deta Nyusu (Internet), (133), p.63 - 67, 2022/10

http://www.aesj.or.jp/~ndd/ndnews/No133.html

no abstracts in English

Study on identification of materials in fuel debris and waste by neutron induced gamma ray spectroscopy

Nauchi, Yasushi*; Nomi, Takayoshi; Suzuki, Risa; Kosuge, Yoshihiro*; Shiba, Tomooki; Takada, Akira*; Kaburagi, Masaaki; Okumura, Keisuke

Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 4 Pages, 2022/10

Depletion calculation of subcritical system with consideration of spontaneous fission reaction

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

Journal of Nuclear Science and Technology, 59(4), p.424 - 430, 2022/04

https://doi.org/10.1080/00223131.2021.1974970

Evaluation of radionuclide inventory

Okumura, Keisuke

Fission Product Behavior under Severe Accident, p.70 - 72, 2021/05

https://www.aesj.net/publish-2101

no abstracts in English

Feasibility study on tritium recoil barrier for neutron reflectors of research and test reactors

Kenzhina, I.*; Ishitsuka, Etsuo; Ho, H. Q.; Sakamoto, Naoki*; Okumura, Keisuke; Takemoto, Noriyuki; Chikhray, Y.*

Fusion Engineering and Design, 164, p.112181_1 - 112181_5, 2021/03

https://doi.org/10.1016/j.fusengdes.2020.112181

Tritium release into the primary coolant during operation of the JMTR (Japan Materials Testing Reactor) and the JRR-3M (Japan Research Reactor-3M) had been studied. It is found that the recoil release by Li(n,)H reaction, which comes from a chain reaction of beryllium neutron reflectors, is dominant. To prevent tritium recoil release, the surface area of beryllium neutron reflectors needs to be minimum in the core design and/or be shielded with other material. In this paper, as the feasibility study of the tritium recoil barrier for the beryllium neutron reflectors, various materials such as Al, Ti, V, Ni, and Zr were evaluated from the viewpoint of the thickness of barriers, activities after long-term operations, and effects on the reactivities. From the results of evaluations, Al would be a suitable candidate as the tritium recoil barrier for the beryllium neutron reflectors.

Evaluation of tritium release into primary coolant for research and testing reactors

Kenzhina, I.*; Ishitsuka, Etsuo; Okumura, Keisuke; Ho, H. Q.; Takemoto, Noriyuki; Chikhray, Y.*

Journal of Nuclear Science and Technology, 58(1), p.1 - 8, 2021/01

https://doi.org/10.1080/00223131.2020.1791760

The sources and mechanisms for the tritium release into the primary coolant in the JMTR and the JRR-3M containing beryllium reflectors are evaluated. It is found that the recoil release from chain reaction of Be is dominant and its calculation results agree well with trends derived from the measured variation of tritium concentration in the primary coolant. It also indicates that the simple calculation method used in this study for the tritium recoil release from the beryllium reflectors can be utilized for an estimation of the tritium release into the primary coolant for a research and testing reactors containing beryllium reflectors.

Development of inventory calculation modules using ORIGEN-S for decommissioning

Matsuda, Norihiro; Konno, Chikara; Ikehara, Tadashi; Okumura, Keisuke; Suyama, Kenya*

JAEA-Data/Code 2020-003, 33 Pages, 2020/03

JAEA-Data-Code-2020-003.pdf:1.85MB

Data handling modules for the radioactivity calculation code, ORIGEN-S, are developed for the reliable evaluations of radioactivity inventory. By using these modules, an activation cross-section data library for the ORIGEN-S code is updated easily and effectively based on a facility-specific neutron spectrum and multi-group neutron activation cross-section library for decommissioning of nuclear facilities, MAXS2015. In order to guarantee the reliability of the radioactivity calculations, functions of data verification in a visual way and numerical comparison between before and after the data processing are also prepared.