| 摘要 |
PURPOSE:To prevent high pressure high temperature water from its outflow to a motor part, by fitting a floating ring, having a sealing surface, to be mounted to the extending portion of a pump shaft in a reactor pressure vessel and closely attaching said sealing surface to an internal wall surface side of the vessel when a pressure in the motor part decreases. CONSTITUTION:A pump shaft 6 fits with a play in its extending part in a nuclear reactor pressure vessel 1 a floating ring 30. This floating ring 30 is shuttle movably arranged in the vertical part of a stretch tube 16 further in the bottom part of a pump impeller. Said floating ring 30 forms in its internal wall part a rugged labyrinth seal (not shown in the drawing) while in the bottom end part a sealing surface closely attached to an upper end seat surface of the stretch tube 16. In this way, in abnormality with the inside of the reactor pressure vessel 1 in a high pressure condition further with the low pressure in a motor part 4, said ring 30, being pressed to the stretch tube 12 by a pressure difference between the both vessel and motor part, can prevent an outflow of high temperature high pressure water in the vessel 1 to a side of the motor part 4.
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