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Journal Articles

A Predicted CRISPR-mediated symbiosis between uncultivated archaea

Esser, S. P.*; Rahlff, J.*; Zhao, W.*; Predl, M.*; Plewka, J.*; Sures, K.*; Wimmer, F.*; Lee, J.*; Adam, P. S.*; McGonigle, J.*; et al.

Nature Microbiology (Internet), 8(9), p.1619 - 1633, 2023/09

 Times Cited Count:1 Percentile:79.8

JAEA Reports

Continuous improvement activities on nuclear facility maintenance in Nuclear Science Research Institute of Japan Atomic Energy Agency in 2021

Task Force on Maintenance Optimization of Nuclear Facilities

JAEA-Technology 2022-006, 80 Pages, 2022/06


The Task force on maintenance optimization of nuclear facilities was organized in the Nuclear Science Research Institute (NSRI) of Japan Atomic Energy Agency (JAEA) since November 2020, in order to adequately respond to "the New nuclear regulatory inspection system since FY 2020" and to continuously improve the facility maintenance activities. In 2021, the task force has studied (1) optimization of the importance classification on maintenance and inspection of nuclear facilities, and (2) improvement in setting and evaluation of the performance indicators on safety, maintenance and quality management activities, considering "the Graded approach" that is one of the basic methodologies in the new nuclear regulatory inspection system. Each nuclear facility (research reactors, nuclear fuel material usage facilities, others) in the NSRI will steadily improve their respective safety, maintenance and quality management activities, referring the review results suggested by the task force.

Journal Articles

Vacuum tube operation tuning for a high intensity beam acceleration in J-PARC RCS

Yamamoto, Masanobu; Okita, Hidefumi; Nomura, Masahiro; Shimada, Taihei; Tamura, Fumihiko; Furusawa, Masashi*; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Sugiyama, Yasuyuki*; et al.

Proceedings of 12th International Particle Accelerator Conference (IPAC 21) (Internet), p.1884 - 1886, 2021/08

Tetrode vacuum tubes in J-PARC RCS are used under a reduced filament voltage condition compared with the rating value to prolong the tube lifetime. For the first time after 60,000 hour of operation in the RCS, one tube has reached the end of its life in 2020. Therefore, the reduced filament voltage works well because the tube has been running beyond an expected lifetime suggested by the tube manufacturer. However, the reduced filament voltage decreased the electron emission from the filament. Although the large amplitude of the anode current is necessary for the high intensity beam acceleration to compensate a wake voltage, a solid-state amplifier to drive a control grid circuit almost reaches the output power limit owing to the poor electron emission from the filament. We changed the filament voltage reduction rate from 15% to 5%. The required power of the solid-state amplifier was fairly reduced, whereas the accelerated beam power remained the same. We describe the measurement results of the vacuum tube parameters in terms of the filament voltage tuning.

Journal Articles

Operation experience of Tetrode vacuum tubes in J-PARC Ring RF system

Yamamoto, Masanobu; Furusawa, Masashi*; Hara, Keigo*; Hasegawa, Katsushi*; Nomura, Masahiro; Omori, Chihiro*; Shimada, Taihei; Sugiyama, Yasuyuki*; Tamura, Fumihiko; Yoshii, Masahito*

JPS Conference Proceedings (Internet), 33, p.011022_1 - 011022_6, 2021/03

A Tetrode vacuum tubes (Thales TH589) are used in the J-PARC ring rf system. The operation has started in 2007, and the total operation time is more than 50,000 hours. There is no tube which reaches the end of life except an initial failure in the 3 GeV synchrotron. TH589 has a thoriated tungsten filament and it is carburized to suppress an evaporation of the thorium. The resistance of the filament decreases through the decarburization process after the filament operation has started. The tube constructor suggests that reduced filament voltage up to 10% compared with the rated value is effective to suppress the decarburization. However, the filament current increases even though the voltage is kept constant due to the resistance reduction, and it is observed that an increment of the power dissipation promotes the decarburization. This means that keeping the filament voltage constant is not enough; keeping the power dissipation constant is necessary to prolong the tube life time, and we employ a procedure to decrease the current regularly.

JAEA Reports

Introduction of a new framework of safety, maintenance and quality management activities in Japan Atomic Energy Agency under the new nuclear regulatory inspection system since FY 2020

Sono, Hiroki; Sukegawa, Kazuhiro; Nomura, Norio; Okuda, Eiichi; Study Team on Safety and Maintenance; Study Team on Quality Management; Task Force on New Nuclear Regulatory Inspection Systems

JAEA-Technology 2020-013, 460 Pages, 2020/11


Japan Atomic Energy Agency (JAEA) has completed the introduction of a new frame work of safety, maintenance and quality management activities under the new acts on the Regulation of nuclear source material, nuclear fuel material and reactors since April 2020, in consideration of variety, specialty and similarity of nuclear facilities of JAEA (Power reactor in the research and development stage, Reprocessing facility, Fabrication facility, Waste treatment facility, Waste burial facility, Research reactor and Nuclear fuel material usage facility). The JAEA task forces on new nuclear regulatory inspection systems prepared new guidelines on (1) Safety and maintenance, (2) Independent inspection, (3) Welding inspection, (4) Free-access response, (5) Performance indicators and (6) Corrective action program for the JAEA's nuclear facilities. New Quality management systems and new Safety regulations were also prepared as a typical pattern of these facilities. JAEA will steadily improve these guidelines, quality management systems and safety regulations, reviewing the official activities under the new regulatory inspection system together with the Nuclear Regulation Authority and other nuclear operators.

Journal Articles

A Study of surface stripper for the AMS system with a footprint below 2 m $$times$$ 2 m

Matsubara, Akihiro; Fujita, Natsuko; Kimura, Kenji

Proceedings of the 8th East Asia Accelerator Mass Spectrometry Symposium and the 22nd Japan Accelerator Mass Spectrometry symposium (EA-AMS 8 & JAMS-22), p.57 - 59, 2020/00

no abstracts in English

Journal Articles

Introduction to development of advanced safeguards and security NDA technologies by JAEA-ISCN

Seya, Michio; Kureta, Masatoshi; Soyama, Kazuhiko; Nakamura, Hironobu; Harada, Hideo; Hajima, Ryoichi

Proceedings of INMM 55th Annual Meeting (Internet), 10 Pages, 2014/07

JAEA has been implementing development programs of basic technologies of the following advanced NDA (non-destructive assay) of nuclear material (NM) for nuclear safeguards and security. (1) Alternative to $$^{3}$$He neutron detection using ZnS/B$$_{2}$$O$$_{3}$$ ceramic scintillator, (2) NRD (neutron resonance densitometry) using NRTA (neutron resonance transmission analysis) and NRCA (neutron resonance capture analysis), (3) NRF (nuclear resonance fluorescence)-NDA using laser Compton scattered (LCS) $$gamma$$-rays (intense mono-energetic $$gamma$$-rays). The development program (1) is for NDA systems that use ZnS/B$$_{2}$$O$$_{3}$$ ceramic scintillator as alternative neutron detector to $$^{3}$$He for coming shortage of its supply. The program (2) is for a NDA system of isotopic composition measurement (non-destructive mass spectroscopy) in targets such as particle-like melted fuel debris using NRTA and NRCA. The program (3) is for NDA systems using a specific NRF reaction of certain Pu/U isotope caused by mono-energetic LCS $$gamma$$-ray with energy tuned to the specific excited state of the isotope. This paper introduces above three programs.

Journal Articles

Concept and results of new operation scheme with improved control system for radio frequency heating in JT-60U

Moriyama, Shinichi; Shinozaki, Shinichi

Japanese Journal of Applied Physics, Part 1, 44(8), p.6224 - 6229, 2005/08

 Times Cited Count:1 Percentile:4.75(Physics, Applied)

The control system of RF heating system in JT-60U has been improved with a concept of dispersion processing and featuring a real time waveform shaping method. It is proper that the brand-new, dispersion processing system has higher performance and reliability than old single processor system before modification, however it is worthy of mention that improvement on operation roll sharing, using the real time waveform shaping, has enabled more efficient and smooth operation. The typical roll sharing is that a simple rectangular waveform of the RF heating power is set by the experiment operator, and the waveform is re-shaped with the parameter set by the RF operator who knows deeply the condition of the RF system at that time. The simple and flexible composition of the new control system will also enable further improvement of hardware to enhance plasma performance that is inevitable to the devices for fusion experiment.

JAEA Reports

Evaluation of heat exchange performance for intermediate heat exchanger in HTTR

Tochio, Daisuke; Nakagawa, Shigeaki

JAERI-Tech 2005-040, 39 Pages, 2005/07


In High Temperature Engineering Test Reactor (HTTR) of 30 MW, the generated heat at reactor core is finally dissipated at the air-cooler by way of the heat exchangers of the primary pressurized water cooler and the intermediate heat exchanger. Heat exchangers in main cooling system of HTTR should satisfy two conditions, achievement of reactor coolant outlet temperature 850 $$^{circ}$$C/950 $$^{circ}$$C and removal of reactor generated heat 30 MW. That is, heat exchange performance should be ensured as that in heat exchanger designing. In this report, heat exchange performance for Intermediate heat exchanger (IHX) in main cooling system is evaluated with rise-to-power-up test and in-service operation data. Moreover, the applicability of IHX thermal-hydraulic design method is discussed with comparison of evaluated data with designed value.

Journal Articles

Heat exchanger performance in main cooling system on high temperature test operation at High Temperature Gas-Cooled Reactor 'HTTR'

Tochio, Daisuke; Nakagawa, Shigeaki; Furusawa, Takayuki*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 4(2), p.147 - 155, 2005/06

High Temperature Engineering Test Reactor (HTTR) of high temperature gas-cooled reactor at JAERI achieved the reactor outlet coolant temperature of 950$$^{circ}$$C for the first time in the world at Apr. 19, 2004. To remove of generated heat at reactor core and to hold reactor inlet coolant temperature as specified temperature, heat exchangers in HTTR main cooling system should have designed heat exchange performance. In this report, heat exchanger performance is evaluated based on measurement data in high temperature test operation. And it is confirmed the adequacy of heat exchanger designing method by comparison of evaluated value with designed value.

Journal Articles

A Modified version of the analytical potential function for the global ab initio ground-state potential energy surface of the BrH$$_{2}$$ system

Kurosaki, Yuzuru; Takayanagi, Toshiyuki*

Chemical Physics Letters, 406(1-3), p.121 - 125, 2005/04

no abstracts in English

Journal Articles

Operational progress of the 110GHz-4MW ECRF heating system in JT-60U

Fujii, Tsuneyuki; Seki, Masami; Moriyama, Shinichi; Terakado, Masayuki; Shinozaki, Shinichi; Hiranai, Shinichi; Shimono, Mitsugu; Hasegawa, Koichi; Yokokura, Kenji; JT-60 Team

Journal of Physics; Conference Series, 25, p.45 - 50, 2005/00

The JT-60U electron cyclotron range of frequency (ECRF) is utilized to realize high performance plasma. Its output power is 4 MW at 110 GHz. By controlling the anode voltage of the gyrotron used in the JT-60U ECRF heating system, the gyrotoron output can be controlled. Then, the anode voltage controller was developed to modulate the injected power into plasmas. This low cost controller achieved the modulation frequency 12 - 500 Hz at 0.7 MW. This controller also extended the pulse width from 5s to 16 s at 0.5 MW. For these long pulses, temperature rise of the DC break made of Alumina ceramics is estimated. Its maximum temperature becomes $$sim$$ 140 deg. From the analysis of this temperature rise, DC break materials should be changed to low loss materials for the objective pulse width of 30 s. The stabilization of neoclassical tearing mode (NTM) was demonstrated by ECRF heating using the real-time system in which the ECRF beams are injected to the NTM location predicted from ECE measurement every 10 ms.

Journal Articles

Corrosion behavior of Al-surface-treated steels in liquid Pb-Bi in a pot

Kurata, Yuji; Futakawa, Masatoshi; Saito, Shigeru

Journal of Nuclear Materials, 335(3), p.501 - 507, 2004/12

 Times Cited Count:29 Percentile:85.61(Materials Science, Multidisciplinary)

Corrosion tests were performed in oxygen-saturated liquid Pb-Bi at 450$$^{circ}$$C and 550$$^{circ}$$C in a pot for 3000h for Al-surface-treated steels containing various levels of Cr contents. The Al surface treatments were achieved using a gas diffusion method and a melt dipping method. Al$$_{2}$$O$$_{3}$$, FeAl$$_{2}$$ and AlCr$$_{2}$$ produced by the gas diffusion method exhibited corrosion resistance to liquid Pb-Bi, while the surface layer produced by the melt dipping method suffered a severe corrosion attack. Fe$$_{4}$$Al$$_{13}$$ and Fe$$_{2}$$Al$$_{5}$$ produced by the melt dipping method disappeared during the corrosion test at 550$$^{circ}$$C and only FeAl remained.

Journal Articles

Performance test of HTTR

Nakagawa, Shigeaki; Tachibana, Yukio; Takamatsu, Kuniyoshi; Ueta, Shohei; Hanawa, Satoshi

Nuclear Engineering and Design, 233(1-3), p.291 - 300, 2004/10

 Times Cited Count:7 Percentile:45.36(Nuclear Science & Technology)

The High Temperature Gas-cooled Reactor (HTGR) is particularly attractive due to its capability of producing high temperature helium gas and due to its inherent safety characteristics. The High Temperature Engineering Test Reactor (HTTR), which is the first HTGR in Japan, was successfully constructed at the Oarai Research Establishment of the Japan Atomic Energy Research Institute. The HTTR achieved full power of 30MW at a reactor outlet coolant temperature of about 850$$^{circ}$$C on December 7, 2001 during the "rise-to-power tests". Two kinds of tests were carried out during the "rise-to-power tests". One is commissioning test to get operation permit by the government and another is test to confirm a performance of the reactor, heat exchanger, control system. From the test results of the "rise-to-power tests" up to 30MW, the functionality of the reactor and the cooling system were confirmed, and it was also confirmed that an operation of reactor facility can be performed safely.

Journal Articles

Performance test results of mock-up test facility of HTTR hydrogen production system

Ohashi, Hirofumi; Inaba, Yoshitomo; Nishihara, Tetsuo; Inagaki, Yoshiyuki; Takeda, Tetsuaki; Hayashi, Koji; Katanishi, Shoji; Takada, Shoji; Ogawa, Masuro; Shiozawa, Shusaku

Journal of Nuclear Science and Technology, 41(3), p.385 - 392, 2004/03

 Times Cited Count:17 Percentile:72.81(Nuclear Science & Technology)

Prior to construction of a HTTR hydrogen production system, a mock-up test facility was constructed to investigate transient behavior of the hydrogen production system and to establish system controllability. The Mock-up test facility with a full-scale reaction tube is an approximately 1/30 scale model of the HTTR hydrogen production system and an electric heater is used as a heat source instead of a reactor. Before the mock-up test, a performance test of the test facility was carried out in the same pressure and temperature conditions as those of the HTTR hydrogen production system to investigate its performance such as hydrogen production ability, controllability and so on. It was confirmed that hydrogen was stably produced with a hot helium gas about 120Nm$$^{3}$$/h which satisfy the design value and thermal disturbance of helium gas during the start-up could be mitigated within the design value by using a steam generator.

Journal Articles

Development of automated measurement device for low-level radioactive contamination on building surfaces

Tachibana, Mitsuo; Ito, Hirokuni*; Hatakeyama, Mutsuo*; Yanagihara, Satoshi

Nihon Genshiryoku Gakkai Wabun Rombunshi, 3(1), p.120 - 127, 2004/03

The RAPID-1600 was developed to measure a low-level radioactive contamination on building surfaces automatically. The double layered detectors are structured by two gas flow type detectors with a $$beta$$ rays shielding plate between the two detectors and it is horizontally positioned. The lower counter measures $$beta$$ and $$gamma$$ rays and the upper counter measures $$gamma$$ rays. The $$beta$$ rays counting rates are derived by subtracting $$gamma$$ rays counting rates of the upper counter from $$gamma$$ and $$beta$$ rays counting rates of the lower counter. This mechanism results in sensitive to $$beta$$ rays against to low background radiation conditions. The driving unit can move omnidirectionally by controlling two driving wheels individually, and has a capability to correct its position if an orbital error is detected by the self-position identification system. The RAPID-1600 was successfully applied to the actual measurement in the radioisotope production facilities. The RAPID-1600 is expected to be a useful tool for measurement of radioactivity in decommissioning nuclear facilities.

Journal Articles

Global ${it ab initio}$ potential energy surfaces for the lowest three doublet states (1$$^{2}$$A', 2$$^{2}$$A', and 1$$^{2}$$A") of the BrH$$_{2}$$ system

Kurosaki, Yuzuru; Takayanagi, Toshiyuki

Journal of Chemical Physics, 119(15), p.7838 - 7856, 2003/10

 Times Cited Count:26 Percentile:64.01(Chemistry, Physical)

Adiabatic potential energy surfaces of the lowest three doublet states (1$$^{2}$$A', 2$$^{2}$$A', and 1$$^{2}$$A") for the BrH$$_{2}$$ system have been calculated globally using the MRCI+Q method with the aug-cc-pVTZ basis set. Spin-orbit effects were considered on the basis of Breit-Pauli Hamiltonian. The calculated adiabatic energies were fitted to the analytical functional form of many-body expansion. The barrier heights of the abstraction and exchange reactions on the ground-state PES were calculated to be 1.28 and 11.71 kcal mol$$^{-1}$$, respectively, at the MRCI+Q/aug-cc-pVTZ level of theory. The fits for the three PESs were successful within the accuracy of 0.1 kcal mol$$^{-1}$$. Thermal rate constants for the abstraction and exchange reactions and their isotopic variants were calculated with the fitted 1$$^{2}$$A' PES using the ICVT/LAG method. The calculated rate constants for the abstarction reactions agree fairly well with experiment but those for the exchange reactions were much smaller than experiment, which suggests that the reliable experimental data are still insufficient.

Journal Articles

Current status of the JAERI superconducting RF linac-based free-electron laser

Minehara, Eisuke; Hajima, Ryoichi; Sawamura, Masaru; Nagai, Ryoji; Kikuzawa, Nobuhiro; Nishimori, Nobuyuki

Proceedings of 28th Linear Accelerator Meeting in Japan, p.31 - 32, 2003/08

Current status of the JAERI superconducting RF linac driven free-electron laser has been reported to describe some details of the FEL device and application researches. In the presentation, several progresses and achievements itimized below have been reproted briefly. Firstly a semi-perpetual, non-stop and continous operation of the JAERI cryogenic and refrigeration system is only available in the world for the JAERI superconducting linac-based FEL. Secondly a conceptual design and each vital component of the ERL(energy recovery linac) light souce has recently been developed and progressed quickly as the next-generation light source. Thirdly,large-scaled industrial applications have been briefly reported here.

JAEA Reports

Transmission system in JT-60U electron cyclotron heating system

Yokokura, Kenji; Hiranai, Shinichi; Shibayama, Minoru*; Ikeda, Yoshitaka; Moriyama, Shinichi; Shinozaki, Shinichi; Sato, Fumiaki*; Kasugai, Atsushi

JAERI-Tech 2003-047, 58 Pages, 2003/06


This report represents a MW-class RF transmission system at 110 GHz in JT-60U electron cyclotron heating system. Its basic design, performances, features, construction experiences, and improvements fed-back from the operation experiences are described. The transmission system has successfully demonstrated high power long pulse operation, e.g., 1MW for 4s with 20 $$sim$$ 25% of low transmission loss which agrees with the designed value.

JAEA Reports

Performance test results of mock-up model test facility with a full-scale reaction tube for HTTR hydrogen production system (Contract research)

Inagaki, Yoshiyuki; Hayashi, Koji; Kato, Michio; Fujisaki, Katsuo; Aita, Hideki; Takeda, Tetsuaki; Nishihara, Tetsuo; Inaba, Yoshitomo; Ohashi, Hirofumi; Katanishi, Shoji; et al.

JAERI-Tech 2003-034, 129 Pages, 2003/05


no abstracts in English

64 (Records 1-20 displayed on this page)