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Journal Articles

Preventive countermeasure of air purge tube blocking using a humidifier in the Tokai Reprocessing Plant

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.

Journal Articles

Development of new three way valve using vacuum for liquid transfer

Yasuo, Kiyoshi; Seto, Nobuhiko; Watahiki, Seiichi; Fukuari, Yoshihiro

Nihon Hozen Gakkai Dai-5-Kai Gakujutsu Koenkai Yoshishu, p.385 - 387, 2008/07

The nitric acid solution including nuclear fuel material is transferred by the three way valve called VCV (VCV: vide-casse-vide in Fr.) using vacuum in the Tokai Reprocessing Plant. The reliability of initial three way valve was not obtained because failure occurred by use for one or two years. The cause of failure was damage of the plastic diaphragms in the moving parts. Then, the new three way valve with stainless-steel bellows was developed. there is no failure in moving parts, reliability improved significantly.

Oral presentation

Liquid leakage from the sea release pipe of the Tokai reprocessing plant; Cause investigation of the leakage, 2; Progress from mechanical damage to the leak

Domura, Kazuyuki; Morimoto, Kenji; Seto, Nobuhiko; Iwasaki, Shogo; Fukuari, Yoshihiro; Inami, Shinichi

no journal, , 

A leak occurred from the sea release pipe buried in the bottom of the sea of the Tokai reprocessing plant. The plumbing of the leak point was cut to investigate the cause of the leak and was collected ashore. Then the investigations such as surface observation and other analyses were performed. As a result of this investigation, the plumbing was scratched at the time of construction from the outside. In the service of approximately 17 years, a damaged part changed with age, and it was estimated that it led to a crack. It was estimated for the leak of the plumbing that hydrogen produced with electrolytic protection caused hydrogen embrittlement cracking and hydrogen induced cracking. This paper reports the details of the investigations.

Oral presentation

Liquid leakage from the sea release pipe of the Tokai reprocessing plant; Summary of ocean-releasing facilities and the leak phenomenon (Confirmation based on the possibility)

Noguchi, Koji; Yasuo, Kiyoshi; Seto, Nobuhiko; Iwasaki, Shogo; Inami, Shinichi

no journal, , 

At the Tokai reprocessing plant, release of the low radioactive fluid to the ocean is carried out using sea release facilities. It was confirmed that there was a leak point on the sea release facilities. Therefore, check and investigation were performed and the leak point was identified. The leak part was cut and the part was then collected to investigate the cause of the leak. As a result, it was estimated that the leak occurred after the pipe was mechanically damaged and a successive change occurred on the part. For this leak point, a series of works for the cause investigation was carried out in detail, the repair work was performed, and preventive measures were taken against recurrences. This paper describes the summary of the sea release facilities, the situation of the outbreak of the leak, and the process that confirmed the leak point.

Oral presentation

Development of a differential pressure switch to be operated correctly, under negative pressure at the Tokai Reprocessing Plant

Yasuo, Kiyoshi; Morimoto, Kenji; Seto, Nobuhiko; Watahiki, Seiichi

no journal, , 

JP, 2009-105389   Patent publication (In Japanese)

Cells and vessels as well as buildings have maintained as a negative pressure to keep nuclear materials inside. Differential pressure switches, detecting change of liquid level and pressure at reprocessing plant, have been required airtightness for the nuclear materials containment under negative pressure. Problem of using the conventional airtight switch is, however, that could not meet the acceptable range with deep negative pressure. We have designed and made a prototype airtight switch applying a new type of pressure detection component. The prototype switch has been reliable on the actual usage, which has been evaluated by an operation, a vibration and an endurance test. We are improving its quality for adapting to the reprocessing process.

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