| 摘要 |
PROBLEM TO BE SOLVED: To provide a fuel assembly for a boiling water reactor, capable of obtaining a very large shutdown margin and which is appropriate for attaining long operational cycle and high burnup. SOLUTION: A fuel rod group, consisting a square grid array with 9×9 rods or more, provided with a large diameter water rod which occupies a region, corresponding to a plurality of fuel rods in the center position of non-boiling region comprises first fuel rods U which do not include burnable positions with an effective length equal to the fuel effective length of the fuel assembly, second fuel rods G, including burnable positions and, having the length shorter than the fuel effective length of the fuel assembly and third fuel rods V, having the length shorter than the fuel effective length shorter than the fuel assembly. At least, a part of fuel rod array, arranged along outermost rod row or along the large diameter water rod, includes a constitution containing fuel rod partial low L with three fuel rods or more, where the second fuel rods G and the third fuel rods V are put side by side.
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