Study on performance evaluation of self-actuated shutdown system for sodium-cooled fast reactor; Flow field measurement around a curie point electromagnet

Yamasaki, Ryota; Aizawa, Kosuke; Kobayashi, Jun; Kurihara, Akikazu

Proceedings of 13th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS13) (Internet), 7 Pages, 2024/11

Enhancement of modelling approaches for the assessment of radionuclide transfer in the marine environment

Periez, R.*; Bezhenar, R.*; Maderych, V.*; Brovchenko, I.*; Liptak, L.*; Kobayashi, Takuya; Min, B.-I.*; Suh, K. S.*; Little, A.*; Iosjpe, M.*; et al.

IAEA-TECDOC-2060, 55 Pages, 2024/07

https://doi.org/10.61092/iaea.pjuc-aha9

This publication describes the work undertaken by Working Group 7, Assessment of Fate and Transport of Radionuclides Released in the Marine Environment of the IAEA's Modelling and Data for Radiological Impact Assessments (MODARIA II) programme (2016-2019). In MODARIA II, the degree of complexity of the models used was increased in order to effectively consider additional processes, specifically uptake by biota, and the spatiotemporal scales of the simulations were also expanded.

Validation of the Be ground-state molecular structure using Be()He triple differential reaction cross-section measurements

Li, P. J.*; Beaumel, D.*; Lee, J.*; Assi, M.*; Chen, S.*; Franchoo, S.*; Gibelin, J.*; Hammache, F.*; Harada, T.*; Kanada-En'yo, Yoshiko*; et al.

Physical Review Letters, 131(21), p.212501_1 - 212501_7, 2023/11

https://doi.org/10.1103/PhysRevLett.131.212501

The cluster structure of the neutron-rich isotope Be has been probed via the () reaction. The triple differential cross-section was extracted and compared to distorted-wave impulse approximation reaction calculations performed in a microscopic framework using the Tohsaki-Horiuchi-Schuck-Rpke wave function and the wave function deduced from Antisymmetrized Molecular Dynamics calculations. The remarkable agreement between calculated and measured cross-sections in both shape and magnitude validates the description of the Be ground-state as a rather compact nuclear molecule.

Intruder configurations in Ne at the transition into the island of inversion; Detailed structure study of Ne

Wang, H.*; Yasuda, Masahiro*; Kondo, Yosuke*; Nakamura, Takashi*; Tostevin, J. A.*; Ogata, Kazuyuki*; Otsuka, Takaharu*; Poves, A.*; Shimizu, Noritaka*; Yoshida, Kazuki; et al.

Physics Letters B, 843, p.138038_1 - 138038_9, 2023/08

https://doi.org/10.1016/j.physletb.2023.138038

Detailed -ray spectroscopy of the exotic neon isotope Ne has been performed using the one-neutron removal reaction from Ne. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N = 20 and N = 28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.

Study on performance evaluation of self-actuated shutdown system for sodium-cooled fast reactor; Investigation on flow field around curie point electromagnet

Aizawa, Kosuke; Hiyama, Tomoyuki; Kobayashi, Jun; Kurihara, Akikazu

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 6 Pages, 2023/05

Self-actuated shutdown system (SASS) is a passive reactor-shutdown system that utilizes a Curie-point electromagnet (CPEM), which features the characteristic of loss in magnetism when the magnet temperature reaches the Curie point. A control rod with SASS is inserted into the core by gravity without recourse to any active shutdown system. To allow the SASS to effectively function, efficiently guiding high-temperature fluid from the fuel assembly to CPEM is important. Therefore, CPEM features a complicated shape such as having 45 fins, and a flow collector is installed upstream of CPEM to direct the flow from the fuel subassembly outlet to CPEM. In this report, the water experiment was performed on the full-scale model that simulates from the outlets of the fuel assemblies to the SASS flow collector, and flow phenomena around the temperature sensing part was analyzed from the data obtained by PIV measurement.

Decommissioning of uranium handling facility for development of nuclear fuel manufacturing equipment

Kageyama, Tomio; Denuma, Akio; Koizumi, Jin*; Odakura, Manabu*; Haginoya, Masahiro*; Isaka, Shinichi*; Kadowaki, Hiroyuki*; Kobayashi, Shingo*; Morimoto, Taisei*; Kato, Yoshiaki*; et al.

JAEA-Technology 2022-033, 130 Pages, 2023/03

JAEA-Technology-2022-033.pdf:9.87MB

Uranium handling facility for development of nuclear fuel manufacturing equipment (Mockup room) was constructed in 1972. The Mockup room has a weak seismic resistance and is deteriorating with age. Also, the original purpose with this facility have been achieved and there are no new development plans using this facility. Therefore, interior equipment installed in this facility had been dismantled and removed since March 2019. After that, the Mockup room was inspected for contamination, and then controlled area in the Mockup room was cancelled on March 29th 2022. A total of 6,549 workers (not including security witnesses) were required for this work. The amount of non-radioactive waste generated by this work was 31,300 kg. The amount of radioactive waste generated by this work was 3,734 kg of combustible waste (103 drums), 4,393 kg of flame resistance waste (61 drums), 37,790 kg of non-combustible waste (124 drums, 19 containers). This report describes about the dismantling and removing the interior equipment in the Mockup room, the amount of waste generated by this work, and procedure for cancellation the controlled area in the facility.

Implication of E3 ligase RAD18 in UV-induced mutagenesis in human induced pluripotent stem cells and neuronal progenitor cells

Shimada, Mikio*; Tokumiya, Takumi*; Miyake, Tomoko*; Tsukada, Kaima*; Kanzaki, Norie; Yanagihara, Hiromi*; Kobayashi, Junya*; Matsumoto, Yoshihisa*

Journal of Radiation Research (Internet), 64(2), p.345 - 351, 2023/03

https://doi.org/10.1093/jrr/rrac099

Countermeasures against noise of inverter-controlled multi-stage root pumps in J-PARC LINAC beam dump

Kobayashi, Fuminori; Kamiya, Junichiro; Moriya, Katsuhiro; Miyao, Tomoaki*; Kotoku, Hirofumi*; Takano, Kazuhiro*

Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.726 - 730, 2023/01

https://www.pasj.jp/web_publish/pasj2022/proceedings/PDF/THP0/THP007.pdf

The L3BT beamline at J-PARC LINAC has beam dumps connected via vacuum partition windows to separate the ultra-high vacuum beamline from the low vacuum beam dumps. Roots pumps are used to evacuate each beam dump. The roots pump controllers have been installed away from the pump in the accelerator tunnel to avoid radiation damages. The special controllers, which have no inverter circuit inside, have been used to reduce the electrical noise on the beam loss monitors nearby. However, in this case, several problems have occurred such as the instability of the pumping performance. To solve such problems, the roots pump controller with the inverter circuit must be used after reducing the electrical noise. In this report, some countermeasures to reduce the electrical noise from the inverters were investigated. The noise reduction circuit was successfully optimized to the level where the beam loss monitors work unaffected.

Investigation on natural circulation behavior for decay heat removal in reactor vessel of sodium-cooled fast reactor under severe accident condition, 1; Effect of decay-heat conditions on natural circulation behavior under dipped-type DHX operation conditions

Tsuji, Mitsuyo; Aizawa, Kosuke; Kobayashi, Jun; Kurihara, Akikazu

Proceedings of 12th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS12) (Internet), 6 Pages, 2022/10

In sodium-cooled fast reactors (SFRs), decay heat removal after a core disruptive accident (CDA) is an important issue for the safety enhancement. Therefore, water experiments using a 1/10 scale experimental apparatus (PHEASANT) that simulates the reactor vessel of an SFR are conducted to investigate the natural circulation phenomena in the reactor vessel. In this study, experiments under the operation of the dipped-type DHX were conducted to investigate the effect of the heat generation ratio between the fuel debris on the core catcher in lower plenum and the reactor core remnant on the natural circulation behavior in the reactor vessel. The temperature distribution and the velocity distribution were measured under two heat generation conditions. Thus, the effect of the heat generation ratio between the fuel debris in the lower plenum and the reactor core remnant on the natural circulation behavior was quantitatively grasped under the dipped-type DHX operating conditions.

Hydrogen absorption and diffusion behaviors in cube-shaped palladium nanoparticles revealed by ambient-pressure X-ray photoelectron spectroscopy

Tang, J.*; Seo, O.*; Rivera Rocabado, D. S.*; Koitaya, Takanori*; Yamamoto, Susumu*; Namba, Yusuke*; Song, C.*; Kim, J.*; Yoshigoe, Akitaka; Koyama, Michihisa*; et al.

Applied Surface Science, 587, p.152797_1 - 152797_8, 2022/06

https://doi.org/10.1016/j.apsusc.2022.152797

The hydrogen absorption and diffusion mechanisms on cube-shaped Pd nanoparticles (NPs) which are important hydrogen-storage materials were studied using X-ray photoelectron spectroscopy and DFT calculations. In the surface region, hydrogen absorption showed almost similar behavior regardless of the NPs size. It was found that the octahedral sites are more favorable than the tetrahedral sites for hydrogen occupation. We also clarified that the hydrogen atoms absorbing on the smaller-sized Pd NPs diffuse to the subsurface more actively because of the weakened Pd-H bond by the surface disordering, which plays an important role in hydrogen adsorption at a low H pressure.