| 摘要 |
PROBLEM TO BE SOLVED: To improve tolerance against vibration caused by flow of a coolant in a system of a control rod guide pipe and a control rod driving mechanism housing. SOLUTION: A plurality of primary cooling water circulation pumps 12 are provided between a reactor pressure vessel 5 and a core shroud 7 along the circumferential direction of the reactor pressure vessel. A discharge flow from the circulation pumps 12 is sent to a fuel part through the interval between a plurality of shroud support legs 6 supporting the core shroud 7. The vertical load of the fuel is supported by the control rod guide pipe 1. The control rod guide pipe 1 is supported by the control rod driving mechanism housing 2 on the lower end position. A control rod guide pipe support point S of the housing 2 is set on the position lower than the upper end of the shroud support legs, and the external shape of a horizontal section of a control rod guide pipe lower part 1b from the support point S to the upside has the same or approximately the same size as a horizontal section external shape of the housing 2. COPYRIGHT: (C)2005,JPO&NCIPI
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