| 摘要 |
PURPOSE:To prevent water leakage by furnishing a weak point pin, which supports a thrust bearing on a pump shaft and collapses when a load over a certain value is applied, and installing a sealing device which checks liquid flow through mutual linkage when said weak point pin has collapsed. CONSTITUTION:If water leak has occurred at a heat-exchanger 9 and primary cooler pipings 18, 19 or a motor 4, the pressure in the motor casing 5 becomes lower than the pressure in a reactor vessel 10. At this time, a load due to pressure difference is applied to the pump shaft 6 in addition to its own weight to cause collapse of a weak point pin 21. As a result, the sealing surface 24 of the pump shaft 6 is detained with the sealing surface 22 of a stretch tube 16 to allow checking of high-temp., high-pressure water from flowing in from the reactor vessel 1 side to the pump casing 5 side. While wet motor type pump 3 is at a standstill in normal condition without water leak, impeller 12 and pump shaft 6 are supported by the weak point pin 21 through a lower thrust bearing 11.
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