Development of self-running underwater cleaner for nuclear facilities

A self-running underwater cleaner for removing sediment accumulated on the bottoms of water tanks in nuclear power stations by remote operation was developed. This cleaner is used in the state maintaining the shielding effect of water against radiation as water is filled in equipment pits, and by the remote operation using cables, it runs freely in water and sucks bottom sediment. The sediment is transported through a drain hose to a treating facility in a power station, and treated in a lump. The cleaner is composed of the carriage with electric steering wheels and driving wheels and a high head submerged pump. Front and rear suction mouths are provided, and suck sediment with high speed water flow while scraping with rubber boards. The cleaner can be used in the water depth of 7 m, and as the results of practical test, it was confirmed that the decontaminating effect and maneuverability were very good so that the sediment at the corner was scarcely left behind, and the effects of labor saving and the reduction of exposure of employees were large. The fundamental experiments were carried out on the running mechanism, the coefficient of friction in water, and the construction of suction mouth. The trial manufacture of the under water cleaner, the water tank experiment and the test in the Mamaoka No. 1 plant are reported. (Kako, I.)