| 摘要 |
PURPOSE: To make optimum moderation of reaction possible by removing the 7 fuel rods from the center part of a fuel assembly and disposing 2 water rods therein. CONSTITUTION: The upper and lower side connection plates of a fuel assembly hold fuel rods of a 9×9 array. Here, the 7 fuel rods are removed from the central part, and 2 D-shaped water rods 30, 32 are disposed back to back therein. The upper and lower parts of the water rods 30, 32 are narrow, and conical attaching body 72 and a tube 76 are attached to both the ends 70 to be supported by the upper and lower connection plates. Thus, both the back-to-back water rods utilize almost the occupied space of the 7 removed fuel rod to be housed in a efficient moderation space, and are turn stoppers to each other. Spacers 61-64 holds a lattice spacers at proper height. Water as a moderator is sufficiently supplied to the center part of a fuel bundle and combustion in the fuel rods can be made the most suitable.
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