Progress of high-power and long-pulse ECRF system development in JT-60

Kobayashi, Takayuki; Isayama, Akihiko; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Sato, Fumiaki; et al.

Nuclear Fusion, 51(10), p.103037_1 - 103037_10, 2011/10

https://doi.org/10.1088/0029-5515/51/10/103037

A new gyrotron operation technique to increase oscillation efficiency was developed on the JT 60 ECRF system. The electron pitch factor was optimized by controlling anode voltage within 0.1 s after the start of the operation. By applying this technique, the gyrotron output power of 1.5 MW for 4 s was recorded, for the first time. The reduced collector heat load at 1.5 MW operations was reduced by 20% and it will be acceptable for longer pulse operation. A new gyrotron with an improved mode converter was developed in order to demonstrate reduction of the stray radiation which had limited the pulse length. The stray radiation was reduced to 1/3 of that of the original gyrotron. A conditioning operation of the improved gyrotron is proceeding up to 31 s at 1 MW. These progresses significantly contribute to enhancing the high power and long pulse capability of the ECRF system toward JT 60SA.

Long pulse/high power ECRF system development in JT-60U

Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Terakado, Masayuki; Sawahata, Masayuki; Suzuki, Sadaaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Hiranai, Shinichi; et al.

Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10

http://www-naweb.iaea.org/napc/physics/FEC/FEC2008/html/node62.htm#15035

In the gyrotron development in JT-60U ECRF system, output power of 1.5 MW for 1 s has been achieved at 110 GHz. It is the world highest power oscillation 1 s. In addition to the carefully designed cavity and collector in view of thermal stress, an RF shield for the adjustment bellows, and a low-dielectric-loss DC break enabled this achievement. Power modulation technique by anode voltage control was improved to obtain high modulation frequency and 5 kHz has been achieved for NTM stabilizing experiments. Long pulse demonstration of 0.4 MW, 30 s injection to the plasma has been achieved with real time control of anode/cathode-heater. It has been confirmed that the temperature of cooled components were saturated and no evidence of damage were found. An innovative antenna having wide range of beam steering capability with linearly-moving-mirror concept has been designed for long pulse. Beam profile and mechanical strength analyses shows the feasibility of the antenna.

Development of the power modulation technique in JT-60U ECH system

Terakado, Masayuki; Shimono, Mitsugu; Sawahata, Masayuki; Shinozaki, Shinichi; Igarashi, Koichi; Sato, Fumiaki; Wada, Kenji; Seki, Masami; Moriyama, Shinichi

JAEA-Technology 2007-053, 28 Pages, 2007/09

JAEA-Technology-2007-053.pdf:4.3MB

The electron cyclotron heating (ECH) system at 110 GHz are injected to JT-60U plasmas with pulse modulation at dozens to hundreds of Hz in order to measure heat conductivity of the plasma to investigate plasma confinement. The JT-60U ECH system has a unique feature to realize the pulse modulation by controlling the anode voltage of the triode gyrotron without chopping the main acceleration voltage. The typical depth of the modulation is 80 % at the modulation frequency range of 12.2 Hz to 500 Hz. However in the JT-60SA, higher modulation frequency of some kHz will be required to stabilize neoclassical tearing mode (NTM). The modulation techniques have been investigated and the modulation frequency of 3.5 kHz with the modulation depth of 84 % has been achieved. The modulation frequency up to 3 kHz is available in the pulse widths of the practical operation. As a next step, replacement of the parts in the anode voltage divider circuit is planned to achieve higher modulation frequency.

Development and contribution of RF heating and current drive systems to long pulse, high performance experiments in JT-60U

Moriyama, Shinichi; Seki, Masami; Terakado, Masayuki; Shimono, Mitsugu; Ide, Shunsuke; Isayama, Akihiko; Suzuki, Takahiro; Fujii, Tsuneyuki; JT-60 Team

Fusion Engineering and Design, 74(1-4), p.343 - 349, 2005/11

https://doi.org/10.1016/j.fusengdes.2005.06.060

no abstracts in English

Development of Welding Process for Oxide Dispersion Strengthened(ODS) Ferritic Steel

Seki, Masayuki; Ishibashi, Fujio; Kihara, Yoshiyuki; Hirako, Kazuhito*; Tsukada, Tatsuya*

JNC TN8410 2005-009, 131 Pages, 2005/04

JNC-TN8410-2005-009.pdf:41.38MB

The development of the welding technology for the ODS steel was started in JFY1987. The first welding examination used the tungsten inert-gas (TIG) welding method and the YAG pulse laser welding method. However, the existing fusion welding methods significantly degrade strength at the welded section, because large size of blowholes appears at the weld and induce coagulation of oxides to generate coarser particles. To solve this problem, we have developed pressurized resistance welding (PRW) as a solid phase welding method.The appropriate conditions, e.g. electric current, voltage and contact force, were selected. For the PRW welded specimens, the tensile, internal burst and creep rupture tests were conducted and its integrity was confirmed. In addition, an ultrasonic inspection method has been developed to assure non-destructively integrity of the welding between cladding and end-plug.

Manufacturing of ODS Test Pieces for MARICO-2 and CMIR-6; Results of Test Pieces Manufacturing

Seki, Masayuki; Ishibashi, Fujio; Kihara, Yoshiyuki; Tsukada, Tatsuya*; Hirako, Kazuhiko*

JNC TN8430 2004-002, 49 Pages, 2005/03

JNC-TN8430-2004-002.pdf:72.34MB

The irradiation test by MARICO-2 and CMIR-6 is planned aiming to the irradiation characteristic of ODS cladding tube. The test pieces of MARICO-2 and CMIR-6 were manufactured by using Martensitic ODS cladding tube and Ferritic ODS cladding tube. The specification of the test pieces was same as two steel type. The test pieces of Martensitic ODS were manufactured from February 19, 2004 to March 11, 2004.(MARICO-2:38test pieces (in clueded 11pieces reserve and QA sample) and CMIR-6:6 test pieces). The test pieces of Ferritic ODS was manufactured from August 17, 2004 and September 22, 2004.(MARICO-2:32test pieces(in clueded 11pieces reserve and QA sample) and CMIR-6:6 test pieces). The problem did not occur for manufacturing the test pieces. Martensitic ODS test pieces was provided for JNC OEC System Division Nuclear fuel group at the May 2004 and Ferritic ODS test pieces was provided for JNC OEC System Division Nuclear fuel group at the October 2004.

Irradiation limit test of ODS ferritic steels fuel pins in BOR-60,1

Kaito, Takeji; Ukai, Shigeharu; Seki, Masayuki; Mayorshin, A. A.*; O.V.SHISHALOV*

JNC TY9400 2003-032, 243 Pages, 2004/03

JNC-TY9400-2003-032.pdf:8.3MB

In order to confirm and demonstrate the ODS fuel pin integrity, the irradiation test has being carried out in the frame of Japan-Russian FBR cyclecooperation. The irradiation test in BOR-60 has started since June, 2003. The target burnup of this irradiation test is up to 150GWd/t.

Pressurized Resistance Welding Technology Development in 9Cr-ODS Martensitic Steels

Seki, Masayuki; Kono, Shusaku; Kihara, Yoshiyuki; Kaito, Takeji; Ukai, Shigeharu; Hirako, Kazuhiko*

Journal of Nuclear Materials, 329-333, p.1534 - 1538, 2004/00

https://doi.org/10.1016/j.jnucmat.2004.04.172

Welding technology for fuel cladding and end-plugs made of ODS steel has been developed to apply for the fast reactor fuel pin fabrication at Tokai-works of JNC. A pressurized resistance welding (PRW) method is utilized as solid phase welding. The method is based on electrical resistance heating of the components while maintaining a continuous force sufficient to forge weld without melting of the components. The contact force between cladding and end-plug is given by pneumatic-hydraulic system. The welding parameters, e.g. electric current, voltage and contact force, are controlled by a programmable system. The appropriate conditions are selected to be a 700 Kgf contact load with 16 kA current for 20 ms after holding for pre-heating by 6 kA current. For relieving the residual stress, the post-welded heat-treatment is performed in the condition of tempering at 1053 K for 10 min. A metallugically bonded welds has been formed by the PRW method, keeping the original dispersed distributio

Measures against the damage of the antenna mouth of JT-60U LHRF system

Ishii, Kazuhiro*; Seki, Masami; Shimono, Mitsugu; Terakado, Masayuki; Igarashi, Koichi*; Takahashi, Masami*

JAERI-Tech 2003-079, 22 Pages, 2003/10

JAERI-Tech-2003-079.pdf:3.01MB

In JT-60U, the study of current drive by radio-frequency (RF) waves in lower hybrid range of frequency (LHRF) has been done as one of research and development works aiming at steady state operation of tokamaks. The main subject of hardware and technology development in this study is to develop a high power LHRF antenna, the main component of the system. The LHRF antenna is set closely to plasma to efficiently inject RF power into it. The LHRF antenna normally receives heat loads from the plasma, and it is required to inject high RF power. Then, it has become a problem that the antenna mouth was melted by excessive heat loads from plasma or it was melted and deformed by RF discharges. As a counter measurement against this, the LHRF antenna has been conditioned to improve its stand-off voltage capability. Furthermore, by monitoring the temperature of the LHRF antenna, adjusting its position, developing a injection method of power modulation even for current drive, and setting an arc sensor which picks up the RF discharge, the damage of the antenna mouth has been suppressed.

Development of Quality Assurance System for Resistance Welding by Ultrasonic Examination -Fabrication of STB for Resistance Welding and Ultrasonic Examination-

Kono, Shusaku; Seki, Masayuki; Fujio, Ishibashi,; Hirako, Kazuhiko*; Tsukada, Tatsuya*

JNC TN8430 2003-010, 28 Pages, 2003/07

JNC-TN8430-2003-010.pdf:2.18MB

The defect occurred at the resistance welding zone is very minute and therefore cannot be identified by X-ray inspection. Then, the ultrasonic examination method, in which the resolution of the defect is higher than that of the X-ray inspection method, has been developed. The ultrasonic wave sounds straight easier in the material than X rays, excels in defecting the micro defect. However, the pulse amplitude of ultrasonic wave is influenced by the shape and direction of the defect. Then, the ultrasonic inspection equipement, in which the ultrasonic probe and the sample rotation axis are controlled to drive with the pulse motor and the defect data (position and size)are analized by image processing ultrasonic signal, was developed to measure the shape and the position of defect accurately. However, an ultrasonic examination method is the comparative inspection method. Therefore, the standard test block or the reference block is indispensable to guarantee the defectability and the ultrasonic echo sensibility of the inspection device. The standard test block is provided in JIS etc, it is needed to defect the peculiar defect occurred at the resistance welding zone. Then, the method of processing a standard test block is examined, the standard test block was made experimentally by electric discharge processing and diffusion junction method. The ultrasonic echo sensitivity and the threshold for image processing were proofread by using the standard test block, the ultrasonic inspection and metallographic inspection were executed. Comparing the ultrasonic inspection results with the metallographic inspection results, the detectability of defect depth and the measurement accuracy were proved to be 3m and with errors less than 10m respectively. From these results, the effectireness of proofreading the ultrasonic inspection condition by the standard test block was confirmed. Moreover, it was confirmed that there was a peculiar relationship between the depth ...