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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
Kobayashi, Fuminori; Kamiya, Junichiro; Takahashi, Hiroki; Suzuki, Yasuo*; Tasaki, Ryuta*
JAEA-Technology 2024-007, 28 Pages, 2024/07
In J-PARC LINAC, the vacuum system is in place to maintain an ultra-high vacuum in the beam transport line (LINAC to 3GeV RCS beam transportation line: L3BT) between the LINAC to the 3GeV synchrotron. The vacuum system is installed in the LINAC and L3BT buildings and consists of vacuum pumps, vacuum gauges, beam line gate valves (BLGVs), and other vacuum. In existing vacuum systems, vacuum equipment is controlled independently for each area, and vacuum equipment can be operated regardless of the status of adjacent areas. This makes it impossible to eliminate erroneous operation due to human error. In addition, when a vacuum deterioration occurs in the beam transport line, the vacuum deterioration ILK signal is transmitted to the BLGV relay unit via the MPS transmission signal, which causes the BLGVs to be forcibly closed. Because the ILK signal transmission range extends to all BLGVs in the L3BT, however, BLGVs in areas unaffected by vacuum deterioration are also forced to close. This could cause problems such as unnecessary open/close operations leading to more frequent maintenance cycles of the BLGVs. In addition, since the BLGV is operated using the MPS signal path, maintenance of the vacuum control system requires work involving the MPS signal path, making it difficult to maintain the vacuum control system alone and making the work complicated. To solve these problems, it is necessary to improve maintainability by separating the signal paths and automatically controlling BLGV separately. Therefore, the vacuum control system was modified and constructed with the aim of realizing a control system that takes into account the safety and efficient maintenance and operation of the L3BT vacuum system. This report summarizes the development and use of the L3BT vacuum system control system.
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
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.
Kamiya, Junichiro; Oi, Motoki; Kobayashi, Fuminori; Sakai, Kenji; Yamada, Ippei
Vacuum and Surface Science, 67(4), p.186 - 191, 2024/04
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.
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
Times Cited Count:21 Percentile:93.59(Physics, Multidisciplinary)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-R
pke 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.
Kondo, Yosuke*; Achouri, N. L.*; Al Falou, H.*; Atar, L.*; Aumann, T.*; Baba, Hidetada*; Boretzky, K.*; Caesar, C.*; Calvet, D.*; Chae, H.*; et al.
Nature, 620(7976), p.965 - 970, 2023/08
Times Cited Count:27 Percentile:94.86(Multidisciplinary Sciences)no abstracts in English
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
Times Cited Count:4 Percentile:69.46(Astronomy & Astrophysics)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.
Periez, R.*; Brovchenko, I.*; Jung, K. T.*; Kim, K. O.*; Liptak, L.*; Little, A.*; Kobayashi, Takuya; Maderich, V.*; Min, B. I.*; Suh, K. S.*
Journal of Environmental Radioactivity, 261, p.107138_1 - 107138_8, 2023/05
Times Cited Count:3 Percentile:34.07(Environmental Sciences)Lagrangian models present several advantages over Eulerian models to simulate the transport of radionuclides in the aquatic environment in emergency situations. A radionuclide release is simulated as a number of particles whose trajectories are calculated along time and thus these models do not require a spatial discretization. In this paper we investigate the dependence of a Lagrangian model output with the grid spacing which is used to calculate concentrations from the final distribution of particles, with the number of particles in the simulation and with the interpolation schemes which are required because of the discrete nature of the water circulation data used to feed the model.
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.
Nakajima, Junya; Hirota, Seiko*; Tsuji, Tomoya; Watanabe, Yuki; Sakoda, Akihiro; Kobayashi, Noriko*
Hoken Butsuri (Internet), 58(1), p.13 - 20, 2023/04
no abstracts in English
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
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.
Kobayashi, Satoru*; Nomura, Eiji*; Chiba, Momoko*; Kawamura, Yukihiko*; Oishi, Kazuki*; Hiroi, Kosuke; Suzuki, Junichi*
Journal of Magnetism and Magnetic Materials, 569, p.170410_1 - 170410_9, 2023/03
Times Cited Count:3 Percentile:32.90(Materials Science, Multidisciplinary)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
Times Cited Count:3 Percentile:53.08(Biology)Kobayashi, Jun; Aizawa, Kosuke; Ezure, Toshiki; Nagasawa, Kazuyoshi*; Kurihara, Akikazu; Tanaka, Masaaki
JAEA-Research 2022-009, 125 Pages, 2023/01
The design studies of an advanced loop-type sodium-cooled fast reactor (Advanced- SFR) have been carried out by the Japan Atomic Energy Agency (JAEA). At the core outlet, temperature fluctuations occur due to mixing of hot sodium from the fuel assembly with cold sodium from the control rod channels and radial blanket assembly. These temperature fluctuations may cause high cycle thermal fatigue around a bottom of Upper Internal Structure (UIS) located above the core. Therefore, we conducted a water experiment using a 1/3 scale 60 degree sector model that simulated the upper plenum of the advanced loop-type sodium-cooled reactor. And we proposed some countermeasures against large temperature fluctuations that occur at the bottom of the UIS. In this report, we have summarized that the effect of the countermeasure structure to mitigate the temperature fluctuation generated at the bottom of UIS is confirmed, and the Reynolds number dependency of the countermeasure structure and the characteristics of the temperature fluctuation on the control rod surface.
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
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.
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.
Aizawa, Kosuke; Tsuji, Mitsuyo; Kobayashi, Jun; Kurihara, Akikazu
Proceedings of 12th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS12) (Internet), 7 Pages, 2022/10
In sodium-cooled fast reactors (SFRs), optimizing the design and operate decay heat removal systems (DHRSs) is important for safety enhancement against severe accidents. Thus, it is required to evaluate the cooling capability of DHRSs including the natural circulation behavior inside the reactor vessel during heat-removal phase that the fuel debris relocated in the reactor vessel is cooled by DHRSs. In this study, the experiments which simultaneously operations of the dipped-type DHX and the penetrated-type DHX were conducted to investigate the effect of operating multiple decay heat removal system on the natural circulation behavior in the reactor vessel. After achieving the stable conditions by operating the dipped-type DHX or the penetrated-type DHX, the other DHX was operated and the transient behavior was clarified by the temperature measurements. The clear temperature rise in the reactor vessel was confirmed by operating the penetrated-type DHX as second DHX operation under the condition of the dipped-type DHX operation at the beginning and the high heater power of fuel debris on the core catcher. Therefore, it was confirmed that the inhibition of the cooling for the decay heat occurred by operating multiple DHXs.
Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.
Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07
This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.
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
Times Cited Count:11 Percentile:67.59(Chemistry, Physical)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.
Suzuki, Hakuto*; Zhao, G.*; Okamoto, Jun*; Sakamoto, Shoya*; Chen, Z.-Y.*; Nonaka, Yosuke*; Shibata, Goro; Zhao, K.*; Chen, B.*; Wu, W.-B.*; et al.
Journal of the Physical Society of Japan, 91(6), p.064710_1 - 064710_5, 2022/06
Times Cited Count:0 Percentile:0.00(Physics, Multidisciplinary)