The air purge method is applied to measure a liquid level and its density of a radioactive solution in a tank in the okai reprocessing pla nt. In this method, air purge tubes soaked in nitric acid solution are often blocked bypositing salt of nitrate. Dried air is usually use d for the air purge system and this can be one of the reasons for enerating salt on the tube point. Therefore, a series of experiment usin g a humidifier to humidify the air has been erformed to prevent the blocking with salt, and the...
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Preventive countermeasure of air purge tube blocking using a humidifierin the Tokai Reprocessing Plant

At the Tokai reprocessing plant, release of the low radioactive waste liquid to the ocean is carried out using sea release facilities. It was found that there was a leak point on the sea release facilities. Therefore, surveillance and confirmation 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 oc curred after the pipe was mechanically damaged and a successive metallurg...
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Liquid leakage from the sea release pipe of the Tokai reprocessing plant -Summary of ocean-releasing facilities and the leak phenomenon -

At the Tokai Reprocessing Plant (TRP), spent fuels are dissolved in nitric acid and the dissolved liquid is fed to the extractors (mixer settlers). In the mixer settlers, both uranium and pluton ium are extracted by the solvent that contains tri-butyl phosphate. It is important to control the interface between organic and aqueous phase in the settlers And the interface is controlled by the flow control valve. This valve has maintainability problems because it takes a fair amount of time to maintenance. In ...
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Improvement of the flow control valve in an extractor in Tokai reprocessing plant

The nitric acid solution dissolving nuclear fuel material is transferred with the three way valve called VCV (VCV: vide-casse- vide in Fr.) using vacuum in the Tokai Reprocessing Plant. The initial VCV was not reliable because it had broken with in 1 or 2years. The cause of failure was damage of the plastic diaphragms in the moving parts. Then, the new VCV valve with stainless- steel bellows was developed. There is no failure in moving parts in 20years, therefore reliability is significantly improved....
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Development of new three way valve using vacuum for liquid transfer

Negative atmospheric pressure is an isolation technique used in nuclear facilities including vessels and hot-cells to prevent release of radioactive materials. In the related system, differential pressure switches are very important function for process monitoring such as liquid level and negative pressure in a reprocessing process. Although air-tight switches have been using to avoid radioactive contamination, such type of switch have not meet requirements for precise operation under deep negative pre...
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Development of a differential pressure switch for precise operation under negative pressure

Recently, the particularity of the working environment in the field of space and oceanic research lead to evelop the remote handling technology and the remote maintenance technology. Additionally, in the field f nuclear technology, such as hot laboratory, it is very important to develop the remote maintenance echnology. Espec ially, in the case of the hot laboratory to handle the irradiated fuel assembly containing he plutonium, the large scale cell equipped with shielding ability and sealing performance i...
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Applying the remote maintenance technology to the Large scale hot laboratory