| 摘要 |
PROBLEM TO BE SOLVED: To provide a control rod capable of controlling a crack caused in a sheath. SOLUTION: The control rod 1 has four blades 2 extended from a tie rod 4 in four directions. The blades 2 each have a sheath 6 having a U-shaped lateral cross-section and hafnium members 3U, 3L of a flattened ellipsoidal tube. Tabs 18 formed on the sheath 6 are individually welded and joined to the tie rod 4. A plurality of recesses 10 formed in the sheath 6 are individually positioned in contact with the side faces on both sides of the hafnium member 3U. The width G of gaps each formed between the side faces on both sides of the hafnium member 3U and the inner face of the sheath 6 facing the side faces is kept at 0.3 mm falling in the range of 0.2 mm<G≤1.0 mm during operation of a BWR. The recesses 10 are formed in a position between the position of the top end of the hafnium member 3U and the position lowered downward from the top end by a length La (=Ls/10) in the axial direction of the sheath 6. COPYRIGHT: (C)2009,JPO&INPIT
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