| 摘要 |
PURPOSE: To effectively use TRU(transuranic element) and reduce the external release of a radiation by arranging a plurality of TRU loaded fuel rods in an area up to the first or second peripheral row of incore instrumentation guide thimbles at the center of a fuel assembly, so as to equally divide the periphery of the thimbles. CONSTITUTION: An MOX fuel assembly has many MOX fuel rods 1 not containing TRU, with control rod guide thimbles 2 and incore instrumentation guide thimbles 3 partly mixed, and a plurality of support grids 4 for focusing a square matrix of 17×17, and fixing the upper and lower ends of the thimbles 2 to upper and lower nozzles. The peripheral first row of the thimbles 2 and two TRU loaded fuel rods 5 are arranged, so as to divide the periphery of the thimbles 2 into two equal sections. The MOX fuel assembly in this case contains 40wt% of Pu and 60wt.% of TRU. Thus, a total TRU amount per fuel assembly is approximately 1/120 of the case of a fuel assembly where all fuel rods are TRU loaded.
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