Study on the evaluation method of radioactivity for dismantling wastes generated from test and research reactors using ORIGEN attached to SCALE6.2.4

Tomioka, Dai; Kochiyama, Mami; Ozone, Kenji; Nakata, Hisakazu; Sakai, Akihiro

JAEA-Technology 2024-023, 38 Pages, 2025/03

JAEA-Technology-2024-023.pdf:1.54MB

Japan Atomic Energy Agency is an implementing organization of near-surface disposal for low-level radioactive wastes generated from research, industrial and medical facilities in Japan. Information on the radioactivity concentration of these radioactive wastes is dispensable for the design and conformity assessment of the waste disposal facilities for the licensing application of the disposal project and its safety review. Radioactive Wastes Disposal Center has been improving the radioactivity evaluation procedure for the dismantling waste generated from the research reactors based on the activation calculation. In order to investigate the applicability of the ORIGEN code (included in SCALE6.2.4), which enables more accurate activation calculations using multigroup neutron spectra, we performed activation calculations with the ORIGEN-code and the ORIGEN-S code (included in SCALE6.0), which has been widely used in the past, for the dismantled wastes from the Rikkyo University Research Reactor, where radioactivity analysis data for the structural materials around the reactor core were compiled. As a result, the calculation time difference between ORIGEN and ORIGEN-S was small and the evaluated radioactivity concentrations of the former were in the range of 0.8-1.0 times those of the latter, which was in good agreement with those of radiochemical analysis in the range of 0.5-3.0 times. The applicability of ORIGEN was confirmed. In addition, activation calculations assuming trace elements in structural materials of nuclear reactor were performed with ORIGEN and ORIGEN-S and the results were compared. The causes of the large differences among 170 nuclides that are important for dose assessment in near-surface disposal were assessed each nuclide.

Transverse asymmetry of individual rays in the La()La reaction

Okuizumi, Mao*; Auton, C. J.*; Endo, Shunsuke; Fujioka, Hiroyuki*; Hirota, Katsuya*; Ino, Takashi*; Ishizaki, Kohei*; Kimura, Atsushi; Kitaguchi, Masaaki*; Koga, Jun*; et al.

Physical Review C, 111(3), p.034611_1 - 034611_6, 2025/03

https://doi.org/10.1103/PhysRevC.111.034611

First measurement of missing energy due to nuclear effects in monoenergetic neutrino charged-current interactions

Marzec, E.*; Dodo, Taku; Haga, Katsuhiro; Harada, Masahide; Hasegawa, Shoichi; Kasugai, Yoshimi; Kinoshita, Hidetaka; Masuda, Shiho; Meigo, Shinichiro; Sakai, Kenji; et al.

Physical Review Letters, 134, p.081801_1 - 081801_9, 2025/00

https://doi.org/10.1103/PhysRevLett.134.081801

Spin dependence in the -wave resonance of +

Okudaira, Takuya*; Nakabe, Rintaro*; Auton, C. J.*; Endo, Shunsuke; Fujioka, Hiroyuki*; Gudkov, V.*; Ide, Ikuo*; Ino, Takashi*; Ishikado, Motoyuki*; Kambara, Wataru*; et al.

Physical Review C, 109(4), p.044606_1 - 044606_9, 2024/04

https://doi.org/10.1103/PhysRevC.109.044606

Dry Pumps in accelerator; Usage at the Japan Proton Accelerator Research Complex (J-PARC)

Kamiya, Junichiro; Oi, Motoki; Kobayashi, Fuminori; Sakai, Kenji; Yamada, Ippei

Vacuum and Surface Science, 67(4), p.186 - 191, 2024/04

https://doi.org/10.1380/vss.67.186

This report describes the usage, specification, troubles and countermeasures of dry pumps in the Japan Proton Accelerator Research Complex (J-PARC). In J-PARC, while dry scroll pumps (DSP) are widely used, many are being replaced with roots pumps due to frequent maintenance and troubles of DSP. Some of the facilities use roots pumps with special specifications, such as radiation-resistant specifications, separate power supply, and with diaphragm type, etc. Although some problems have occurred with both DSPs and roots pumps, they have been addressed by revising maintenance methods and improving parts, contributing to stable operation for users.

Longitudinal spin fluctuations driving field-reinforced superconductivity in UTe

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Opletal, P.; Tokiwa, Yoshifumi; Haga, Yoshinori; Kitagawa, Shunsaku*; Ishida, Kenji*; Aoki, Dai*; Knebel, G.*; et al.

Physical Review Letters, 131(22), p.226503_1 - 226503_7, 2023/12

https://doi.org/10.1103/PhysRevLett.131.226503

Large reduction in the -axis knight shift on UTe with = 2.1 K

Matsumura, Hiroki*; Fujibayashi, Hiroki*; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; et al.

Journal of the Physical Society of Japan, 92(6), p.063701_1 - 063701_5, 2023/05

https://doi.org/10.7566/JPSJ.92.063701

Angular distribution of rays from a neutron-induced -wave resonance of Xe

Okudaira, Takuya*; Tani, Yuika*; Endo, Shunsuke; Doskow, J.*; Fujioka, Hiroyuki*; Hirota, Katsuya*; Kameda, Kento*; Kimura, Atsushi; Kitaguchi, Masaaki*; Luxnat, M.*; et al.

Physical Review C, 107(5), p.054602_1 - 054602_7, 2023/05

https://doi.org/10.1103/PhysRevC.107.054602

no abstracts in English

Change of superconducting character in UTe induced by magnetic field

Kinjo, Katsuki*; Fujibayashi, Hiroki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; Homma, Yoshiya*; et al.

Physical Review B, 107(6), p.L060502_1 - L060502_5, 2023/02

https://doi.org/10.1103/PhysRevB.107.L060502

Analysis on cooling behavior for simulated molten core material impinging to a horizontal plate in a sodium pool

Matsushita, Hatsuki*; Kobayashi, Ren*; Sakai, Takaaki*; Kato, Shinya; Matsuba, Kenichi; Kamiyama, Kenji

Proceedings of 13th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-13) (Internet), 9 Pages, 2022/09

During core disruptive accidents in sodium-cooled fast reactors, the molten core material flows through flow channels, such as the control rod guide tubes, into the core inlet plenum under the core region. The molten core material can be cooled and solidified while impinging on a horizontal plate of the inlet plenum in a sodium coolant. However, the solidification and cooling behaviors of molten core materials impinged on a horizontal structure have not been sufficiently studied thus far. Notably, this is an important phenomenon that needs to be elucidated from the perspective of improving the safety of sodium-cooled fast reactors. Accordingly, a series of experiments on discharging a simulated molten core material (alumina: AlO) into a sodium coolant on a horizontal structure was conducted at the experimental facility of the National Nuclear Center of the Republic of Kazakhstan. In this study, analyses on the sodium experiments using SIMMER-III as the fast reactor safety evaluation code were performed. The analysis methods were validated by comparing the results and experiment data. In addition, the cooling and solidification behaviors during jet impingement were evaluated. The results indicated that the molten core material exhibited fragmentation owing to the impingement on the horizontal plate and was, therefore, scattered toward the periphery. Furthermore, the simulated molten core material was evaluated to be cooled by sodium and subsequently solidified.