Analysis work on flush-out of plutonium and uranium for decommissioning of main plant in Tokai Reprocessing Plant

Sato, Hinata; Mori, Amami; Kuno, Sorato; Horigome, Kazushi; Goto, Yuichi; Yamamoto, Masahiko; Taguchi, Shigeo

JAEA-Technology 2024-011, 56 Pages, 2024/10

JAEA-Technology-2024-011.pdf:2.5MB

Flush-out, which recovers remaining nuclear materials in the process and transfer it to a highly radioactive liquid waste storage tank, has been performed at main plant of Tokai Reprocessing Plant. The flush-out has been composed from three steps: first step is to remove of spent fuel sheared powder, second step is to collect plutonium solution stored in the process, and third step is to convert uranium solution into uranium trioxide powder. The first step of flush-out activity has been completed in 2022. Second and third steps of flush-out have been completed from March 2023 to February 2024. Process control analysis has been performed for operation of the facility, and material accountancy analysis has been performed to control the accountancy of nuclear materials. In addition, related analytical work such as pretreatment for transporting inspection samples for safeguards analysis laboratories in IAEA has been also performed. This report describes results of analytical work performed in collections of plutonium and uranium solutions in second and third steps of the flush-out, including calibration of analytical equipment, waste generation, and education and training of analytical operator.

Gyrotron development for high-power, long-pulse electron cyclotron heating and current drive at two frequencies in JT-60SA and its extension toward operation at three frequencies

Kobayashi, Takayuki; Moriyama, Shinichi; Yokokura, Kenji; Sawahata, Masayuki; Terakado, Masayuki; Hiranai, Shinichi; Wada, Kenji; Sato, Yoshikatsu; Hinata, Jun; Hoshino, Katsumichi; et al.

Nuclear Fusion, 55(6), p.063008_1 - 063008_8, 2015/06

https://doi.org/10.1088/0029-5515/55/6/063008

A gyrotron enabling high-power, long-pulse oscillations at both 110 GHz and 138 GHz has been developed for electron cyclotron heating (ECH) and current drive (CD) in JT-60SA. Oscillations of 1 MW for 100 s have been demonstrated at both frequencies, for the first time as a gyrotron operating at two frequencies. The optimization of the anode voltage, or the electron pitch factor, using a triode gun was a key to obtain high power and high efficiency at two frequencies. It was also confirmed that the internal losses in the gyrotron were sufficiently low for expected long pulse operation at the higher power level of 1.5 MW. Another important result is that an oscillation at 82 GHz, which enables to use fundamental harmonic waves in JT-60SA while the other two frequencies are used as second harmonics waves, was demonstrated up to 0.4 MW for 2 s. These results of the gyrotron development significantly contribute to enhancing operation regime of the ECH/CD system in JT-60SA.

Development of instrument to measure transmission power density distribution using dielectric disk in millimeter waveguide

Yokokura, Kenji; Moriyama, Shinichi; Kobayashi, Takayuki; Hiranai, Shinichi; Sawahata, Masayuki; Terakado, Masayuki; Hinata, Jun; Wada, Kenji; Sato, Yoshikatsu; Hoshino, Katsumichi; et al.

JAEA-Technology 2014-002, 64 Pages, 2014/03

JAEA-Technology-2014-002.pdf:6.83MB

A new instrument has been developed to measure spatial distribution of power density and total power of the millimeter wave, by measuring temperature rise of dielectric material inserted in the waveguide. For a measurement, a dielectric disk with thermally insulated support is inserted into the few millimeters gap in the waveguide. The disk is heated by the millimeter wave pulse for 0.10.2 s, and immediately after the pulse, it is pulled up and its temperature distribution is measured by an infrared camera to estimate the spatial power density distribution of the millimeter wave. In the other hand, total transmission power is estimated by the disk temperature reached equilibrium. In the measurement test, deformation of the power density distribution was successfully detected when the mirror angle was intentionally changed in the matching optics unit (MOU) at the waveguide input from the gyrotron. The test result shows that the instrument is effective for both adjustment of MOU without opening the vacuum boundary and to detect any abnormal transmission during operation of the ECH system. The test also shows high reliability of the instrument which stands with 1 MW high power transmission without any arcing or pressure rise in vacuum region. The instrument will be contributed to keep good condition of high power long pulse ECH system by detecting abnormal transmission in the waveguide in operation without open vacuum boundary.

Dual frequency ECRF system development for JT-60SA

Kobayashi, Takayuki; Isayama, Akihiko; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Wada, Kenji; Sato, Yoshikatsu; Hinata, Jun; Yokokura, Kenji; et al.

Fusion Science and Technology, 63(1T), p.160 - 163, 2013/05

https://doi.org/10.13182/FST13-A16895

A dual frequency electron cyclotron range of frequency system has been developed for JT-60SA, by which a second frequency (135 140 GHz) is generated in addition to the first frequency of 110 GHz. A development of a dual frequency gyrotron is a key to realize the dual frequency system. The second frequency was chosen to be 138 GHz from the above frequency range from the viewpoint of gyrotron design. In order to realize high-power ( 1 MW) and long-pulse operation for both frequencies, we designed main components of the gyrotron (the diamond window, cavity resonator and quasi-optical mode converter). We found the optimum parameter set from the parameters of these components, which has discrete characteristics. It was confirmed that the output power higher than 1 MW is obtained for both frequencies as a result of numerical design. Based on the above design, a dual frequency gyrotron was newly fabricated. In the conditioning operation, an output power was obtained as we expected.

Recent results from the development of the electron cyclotron heating system for JT-60SA toward high-power long-pulse operations

Isayama, Akihiko; Kobayashi, Takayuki; Yokokura, Kenji; Shimono, Mitsugu; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Wada, Kenji; Hinata, Jun; et al.

Plasma and Fusion Research (Internet), 7(Sp.1), p.2405029_1 - 2405029_5, 2012/05

http://www.jspf.or.jp/PFR/PFR_articles/pfr2012S1/pfr2012_07-2405029.html

no abstracts in English

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.

Progress in launcher developments for electron cyclotron heating and current drive in JT-60SA

Kobayashi, Takayuki; Moriyama, Shinichi; Isayama, Akihiko; Hiranai, Shinichi; Sawahata, Masayuki; Terakado, Masayuki; Wada, Kenji; Sato, Yoshikatsu; Hinata, Jun; Yokokura, Kenji; et al.

no journal, , 

In JT-60SA, electron cyclotron heating and current drive (the maximum injection power of 7 MW with the longest pulse length of 100 s) is planned for various experimental objectives, such as electron heating, stabilization of instabilities and start-up assist. An two directional (toroidal and poloidal) beam steering capability is required for the launcher, which injects millimeter waves into plasmas. Moreover, active cooling of antenna mirrors is required for long pulse injection of 100 s. In order to satisfy the above requirements with high reliability, the launcher is being developed based on a linear-motion antenna concept. Recently, design of the steering mechanism using two bellows was improved to increase reliability. In the revised design, it is easy to replace one of the bellows, which is moved with large mechanical load. We also carried out an initial thermal analysis on the large curved mirror, and we obtained important knowledge on the making cooling channels in the mirror. In addition to the above results, we evaluated the transmission loss at the first mirror by including an higher order mode (LP11) of 10%. The estimated loss is smaller than 1% and acceptable.

Design and development of electron cyclotron heating and current drive system for JT-60SA

Kobayashi, Takayuki; Isayama, Akihiko; Hoshino, Katsumichi; Yokokura, Kenji; Shimono, Mitsugu; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Wada, Kenji; et al.

no journal, , 

Design and development of high-power long-pulse electron cyclotron heating and current drive system for JT-60SA have been progressed. High power transmission test using newly developed components with a waveguide inner diameter of 60.3 mm was carried out. A conditioning operation was progressed to 5 s with an output power of 0.5 MW, so far, within a few weeks without significant trouble. The other progress was made to develop the dual frequency system with an additional frequency of 137.6 GHz in order to enhance operation regime. Output power higher than 1 MW with oscillation efficiency much higher than 30% was obtained for the design of a dual frequency gyrotron for both 110 GHz and 137.6 GHz.

Development and preparation for JT-60SA ECH system

Moriyama, Shinichi; Kobayashi, Takayuki; Sawahata, Masayuki; Terakado, Masayuki; Hiranai, Shinichi; Wada, Kenji; Sato, Yoshikatsu; Hinata, Jun; Yokokura, Kenji; Hoshino, Katsumichi; et al.

no journal, , 

Long pulse operation of the dual frequency gyrotron was started for JT-60SA ECH system. Pulse length of 2 s at 0.4 MW output, and 1 s at 0.7 MW were obtained at both 110 GHz and 138 GHz, so far. Typical oscillation efficiency is about 30%. Diffraction loss was acceptable for long pulse 1 MW output. The first high power test of the "power and beam profile monitor" featuring a fast movable SiN disk in the waveguide slit was successfully demonstrated.

Development on the heat load reduction technology for the gyrotron collector in the JT-60SA ECH system

Terakado, Masayuki; Sawahata, Masayuki; Hiranai, Shinichi; Kobayashi, Takayuki; Hinata, Jun; Wada, Kenji; Sato, Yoshikatsu; Yokokura, Kenji; Hoshino, Katsumichi; Moriyama, Shinichi; et al.

no journal, , 

In the JT-60SA tokamak under construction for nuclear fusion experiments, the electron cyclotron heating (ECH) is expected. The oscillation output of gyrotron in the ECH system in JT-60 was 1 MW for 5 s, but for the new system in JT-60SA, 1 MW for 100 s is the development target. In addition, development toward 1.5 MW output is going on in parallel. In these developments, it is important to reduce a heat load by the electron beam toward the collector of the gyrotron. Because time constant of the temperature rise of the collector is around 10 s, heat load may become a serious problem for a longer pulse than 5 s. Higher power output will also increase the heat load. Localization of the heat load toward the collector is essentially prevented by changing a magnetic field by sweeping coils installed outside the collector. This time, the temperature distribution on the collector was examined by changing the sweep-wave-pattern for the sweeping coil to obtain more uniform heat load.