Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Saruta, Koichi; Tsukimori, Kazuyuki; Shimada, Yukihiro; Nishimura, Akihiko; Kobayashi, Takao*
Nihon Hozen Gakkai Dai-6-Kai Gakujutsu Koenkai Yoshishu, p.219 - 222, 2009/08
A thermal-resistant fiber Bragg grating (FBG) fabricated by femtosecond laser processing was examined to evaluate the performance as a strain sensor, compared with a conventional FBG sensor. Each FBG was affixed on a stainless-steel beam along with a strain gauge to measure the Bragg wavelength shift as a function of strain. We used the intensity of the reflection spectra from the FBGs as a weighting factor to determine the Bragg wavelengths. Although the strain sensitivity for the thermal-resistant FBG was found to be 0.34 pm/
, a measurement accuracy of 
3 was able to be achieved by employing the Bragg wavelength determination algorithm, which was comparable to a measurement accuracy of 2 for the conventional FBG sensor.
Yasuo, Kiyoshi; Seto, Nobuhiko; Watahiki, Seiichi; Iwasaki, Shogo; Inami, Shinichi
Nihon Hozen Gakkai Dai-6-Kai Gakujutsu Koenkai Yoshishu, p.506 - 509, 2009/08
The air purge method is applied to measure a liquid level and its density of a radioactive solution in a tank in the Tokai reprocessing plant. In this method, air purge tubes soaked in nitric acid solution are often blocked by depositing salt of nitrate. Dried air is usually used for the air purge system and this can be one of the reasons for generating salt on the tube point. Therefore, a series of experiment using a humidifier to humidify the air has been performed to prevent the blocking with salt, and the effect has been experimentally confirmed.
Watashi, Katsumi
Nihon Hozen Gakkai Dai-6-Kai Gakujutsu Koenkai Yoshishu, p.337 - 341, 2009/08
Furnace tubes are widely used in heat transfer device in petroleum or chemical industries. This study proposes an alternative calculation method for the evaluation of creep rupture damage factor of furnace tubes. The method is consistency with an evaluation procedure described in American Petroleum Institute document API 581. Three types of creep parameters including Larson-Miller parameter, namely NRIM creep rupture data of furnace tube material, can be applied for evaluation. The method is rather simple compared with original method described in API 581 first edition.
Sakata, Mami; Yagi, Masahiro; Horiguchi, Hironori; Hirane, Nobuhiko
Nihon Hozen Gakkai Dai-6-Kai Gakujutsu Koenkai Yoshishu, p.275 - 278, 2009/08
A crack was found on a weld area of one reflector element in JRR-4 on December 28, 2007. The following examinations were carried out, visual examination, dimensional examination, fractography examination and so on. It was concluded that the main cause of the crack is the neutron-induced swelling of graphite in the reflector element. We tested radiographycally the other reflector elements. As the result, we determined that many of them were not in a suitable state to be used because of swelling of graphite. Based on the relation between the irradiation dose and swelling rate, the design of the new reflector elements has been carried out. We decided to test radiographycally all the new reflector elements as the future maintenance.
Isaka, Koji; Terunuma, Noriaki; Ouchi, Satoshi; Oki, Keiichi; Suwa, Masayuki
Nihon Hozen Gakkai Dai-6-Kai Gakujutsu Koenkai Yoshishu, p.279 - 282, 2009/08
As the modified JRR-3 has been operated for 18 years, it is necessary to be maintained for keeping the safe and stable operation. The review of maintenance activity is constantly performed for the step-by-step update of facilities and the improvement of the maintenance method and so on. Our investigation of the maintenance activity about the instrumentation and control device of modified JRR-3 is presented.
Ishii, Takahiro; Shimizu, Kazuyuki; Sakai, Katsumi; Inami, Shinichi
Nihon Hozen Gakkai Dai-6-Kai Gakujutsu Koenkai Yoshishu, p.289 - 293, 2009/08
The automatic fire alarm system installed in the Tokai Reprocessing Plant consists of more than 5000 detectors in about 40 facilities for the moment. In this system, 51 non-fire cases have occurred for 8 years; 2001 Jan. to 2009 May, and about half of these cases was due to the condensation of water vapor generated on the sensor. Therefore, the prevention of condensation is necessary to reduce such false alarms, and the measure for prevention of condensation has been taken by installing a mount for the detector basement. This mount facilitates that the detector does not contact directly to the surface of ceiling where is likely to change an environment due to changeable temperature and humidity. As a result, false alarms caused by condensation have not been found on the detectors with the mounts. This paper reports the details of the improved fire alarm system, and cause/measures for false alarms.
Nishida, Kyosuke; Hiyama, Hisao; Shibata, Satomi; Iwasaki, Shogo; Inami, Shinichi
Nihon Hozen Gakkai Dai-6-Kai Gakujutsu Koenkai Yoshishu, p.294 - 297, 2009/08
Uninterruptible power supply systems are installed in the Tokai reprocessing plant in preparation for the emergency case that the commercial power supply is stopped by an accidental or intentional interruption in the supply of electricity. The uninterruptible power supply system particularly provides a temporary power source to the important devices for the radiation control of nuclear critical monitoring in the plant. Thus, the system is potentially important and essential for nuclear plants. The paper repots the current activities such as regular inspections, replacement of parts and system update, to maintain the function of uninterruptible power supply systems.
Tagawa, Akihiro; Fujiki, Kazunari
Nihon Hozen Gakkai Dai-6-Kai Gakujutsu Koenkai Yoshishu, p.570 - 574, 2009/08
This study checks the high-temperature durability of the electromagnetic acoustic transducer (EMAT) for pipe wall thinning. We inserted EMAT into the oven and measured the 10 mm thickness specimen by EMAT about two years. Measurement was carried out by two kinds, a pulse echo method and a pulse echo resonance method. And high-temperature durability was checked by both of the measuring methods. Compared with the pulse echo method, the pulse echo resonance method of measurement accuracy was better. The filter processing of removing magnet signal is required high-temperature measurement. EMAT is a simple configuration of a coil and a magnetic combination. Therefore, a sensor does not break easily. Therefore, EMAT is applicable to the pipe wall thinning monitoring of a nuclear power plant.
Ito, Fuyumi; Nishimura, Akihiko
Nihon Hozen Gakkai Dai-6-Kai Gakujutsu Koenkai Yoshishu, p.551 - 553, 2009/08
Fine magnetic particles having UV fluorescence are commonly used in magnetic crack detection technique. Stress corrosion cracking sometimes happens in nuclear power plants. To apply this technique to maintain the heat exchanger tubes, it is desired that these particles has performance to be collected with ease. To collect these fine magnetic particles from millimeter size crack depth, a chemosynthesis technique to produce the micro capsules successfully produced hundreds micron sized capsules containing the fine magnetic particles. The synthesized micro capsules indicated the collective sensitivity for lines of magnetic force.
Nishimura, Akihiko; Oka, Kiyoshi; Yamaguchi, Toshihiko; Akatsu, Tomohiro*; Seki, Takeshi*; Mihalache, O.; Shimada, Yukihiro; Tagawa, Akihiro; Yamashita, Takuya
Nihon Hozen Gakkai Dai-6-Kai Gakujutsu Koenkai Yoshishu, p.250 - 253, 2009/08
In order to maintain FBR heat exchanger tubes, a new probe system was designed. A coupling unit and operational software are key components in the second year. The coupling unit to combine a high energy laser beam and optical fiberscope images was developed. The operational software successfully controlled an eddy current testing device and a laser processing head.