| 摘要 |
PROBLEM TO BE SOLVED: To drive a control rod without requiring an electric motor, and to reduce the number of part items for a control rod driving mechanism, so as to reduce a construction cost for a nuclear power plant. SOLUTION: A driving piston 30, a rotary piece 31 and a seal piston 32 are attached to a lower part of a hollow piston 18 inserted into a housing 5 for the control rod driving mechanism. A labyrinth seal 32 is provided in an outer circumferential face of the seal piston 32 to be oppose to an inner face of a guide tube 7. A lower end opening part of the housing 5 for the control rod driving mechanism is closed by a flange 29. Scram hydraulic pressure is applied from an introduction port 21 provided in a lower end part of the housing 5 for the control rod driving mechanism, to push up the seal piston 32, and the control rod coupled to a tip part of the hollow piston 18 is inserted thereby into a reactor core.
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