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Nemoto, Takahiro; Fujiwara, Yusuke; Arakawa, Ryoki; Choyama, Yuya; Nagasumi, Satoru; Hasegawa, Toshinari; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; et al.
JAEA-Technology 2024-003, 17 Pages, 2024/06
JAEA-Technology-2024-003.pdf:1.91MB
In order to investigate the cause of the increase in differential pressure in the primary helium circulator filter that occurred during the RS-14 cycle, a clogged filter was investigated. As a result of the investigation, deposits caused by silicone oil were confirmed on the surface of the filter element. These results revealed that the cause of filter clogging was silicone oil mixed into the primary system due to performance deterioration of the charcoal filter in the gas circulator of primary helium purification system. As a measure to prevent the recurrence of this event, in addition to the conventional management based on operating hours for replacing of charcoal filter in the gas circulator of primary helium purification system, we have established a new replacement plan for every three years.
Hasegawa, Toshinari; Nagasumi, Satoru; Nemoto, Takahiro; Nakajima, Kunihiro; Yokoyama, Keisuke; Fujiwara, Yusuke; Arakawa, Ryoki; Iigaki, Kazuhiko; Inoi, Hiroyuki; Kawamoto, Taiki
Proceedings of 2024 International Congress on Advanced in Nuclear Power Plants (ICAPP 2024) (Internet), 10 Pages, 2024/06
The filter element of the primary gas circulators (PGC) in High Temperature engineering Test Reactor (HTTR) and its deposits were investigated by Scanning Electron Microscope (SEM) observation and Energy Dispersive X-ray spectroscopy (EDX) analysis to find the cause of the increase of the filter differential pressure during the operation in 2021. SEM observation showed that the clumpy deposits and fibrous deposits smaller than the filtration pore size and the rod-shaped deposits larger than the pore size were present on the filter element. EDX analysis showed that the clumpy deposits and fibrous deposits could include silicone oil in the primary helium purification system (PHPS) gas circulators and that the rod-shaped deposits were thermal insulators inside of the co-axial double pipes in the primary cooling system. It is considered that silicone oil leaked from the PHPS gas circulators due to deterioration in the absorption performance of the activated charcoal filter. Next, it could be vaporized and reach PGC's filter element after passing through the reactor core. Since those deposits including silicone oil were present over the entire surface of the filter element, the filter differential pressure could be increased due to a reduction in the pore size and a rise in its flow resistance. The thermal insulator was unrelated to filter clogging because it was present mainly in the lower part of the filter element. Therefore, silicone oil could increase the filter differential pressure, and the graphite powder, which is the cause of the previous issue was unrelated.
Nemoto, Takahiro; Arakawa, Ryoki; Kawakami, Satoru; Nagasumi, Satoru; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; Furusawa, Takayuki; Inoi, Hiroyuki; et al.
JAEA-Technology 2023-005, 33 Pages, 2023/05
JAEA-Technology-2023-005.pdf:5.25MB
During shut down of the HTTR (High Temperature engineering Test Reactor) RS-14 cycle, an increasing trend of filter differential pressure for the helium gas circulator was observed. In order to investigate this phenomenon, the blower of the primary helium purification system was disassembled and inspected. As a result, it is clear that the silicon oil mist entered into the primary coolant due to the deterioration of the charcoal filter performance. The replacement and further investigation of the filter are planning to prevent the reoccurrence of the same phenomenon in the future.
Arakawa, Ryoki; Nosaki, Nobuhisa
JAEA-Technology 2019-018, 157 Pages, 2020/03
JAEA-Technology-2019-018.pdf:12.97MB
The Naraha Center for Remote Control Technology Development has various test facilities for the decommissioning work after the accident of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, and is now promoting external use. In the test facilities, the robot test pool for the underwater robot can be used in different temperature conditions from room temperature to 60
C, maximum setting temperature. In order to clarify the temperature behavior in heating condition, a heating test from room temperature to 60C was performed. The data was obtained this way. From the data, a heat transfer model for evaluating the temperature behavior was investigated, and the temperature evaluation method for the robot test pool was developed. By using the developed evaluation method, the influence of various factors such as flow rate and humidity on the temperature behavior was investigated for the condition of temperature heating, holding (test condition) and cooling. From the investigation, the temperature behavior of the robot test pool was analytically clarified, and a reasonable operation method was proposed. This report summarizes the results of analytical study at the temperature heating, holding and cooling condition.
Nishimura, Akihiko; Yoshida, Minoru*; Yamada, Tomonori; Arakawa, Ryoki
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 3 Pages, 2019/05
JAEA support the development of remote sensing robotic system in the Naraha Remote Technology Development Center. A water tank is used as a mockup facility of nuclear reactor vessel. A compact seismic vibrometer based on an optical fiber interferometer is applied. A specially designed robotic system is also tested for installing the sensor unit. The experiment is prepared to clarify the transfer function of the water tank, using vibration noise of ground motion.
Arakawa, Ryoki; Nosaki, Nobuhisa
JAEA-Technology 2018-013, 51 Pages, 2019/02
JAEA-Technology-2018-013.pdf:7.75MB
The Naraha Center for Remote Control Technology Development has various test facilities for the decommissioning work after the accident of the Fukushima Daiichi Nuclear Power Station, TEPCO Holdings, and is now promoting external use. In the test facilities, the robot test pool for the underwater robot can be used in different temperature conditions from room temperature to 60C, maximum setting temperature. In order to clarify the temperature behavior in heating condition, a heating test from room temperature to 60C was performed, and obtained the data. From the obtained temperature data, a heat transfer model for evaluating the temperature behavior was investigated, and the temperature evaluation method for the robot test pool was developed. This report summarizes the developed heat transfer model, and also summarizes the temperature evaluation method during heating and cooling conditions. Moreover, user's manual for the temperature evaluation code was also created.
Arakawa, Ryoki; Nosaki, Nobuhisa; Hirata, Yuji*
JAEA-Technology 2018-009, 28 Pages, 2019/01
JAEA-Technology-2018-009.pdf:2.94MB
The Naraha Center for Remote Control Technology Development consists of a mock-up test building and a research management building, and various test facilities are installed in them for the decommissioning work after the accident of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings. In the test facilities, the robot test pool for the underwater robot can be tested under temperature conditions raised from room temperature to 60C. Then, for the purpose of grasping the temperature distribution inside of the pool and the temperature rising behavior in temperature raising condition, a temperature heating test with room temperature to 60C. (maximum setting temperature) was performed, and as well as an analytical study was performed. This report summarizes the obtained both experimental and analytical studies.
Arakawa, Ryoki
Kenchiku Bosai, (481), p.1 - 4, 2018/02
This report introduces process and the facilities that Naraha remote technology development center was established.
Arakawa, Ryoki
Enerugi Rebyu, 37(10), p.17 - 18, 2017/10
The Naraha Remote Technology Development Center was established in Naraha-town, Fukushima in 2013. This report introduces facilities, research and development, use of facilities.