| 摘要 |
PROBLEM TO BE SOLVED: To enable long period continuous operation and attain high burnup by loading uranium fuel rods with lower isotope uranium-235 existence ratio than natural uranium at a control rod side corner. SOLUTION: This fuel assembly is of 9×9 fuel assembly arranged by two thick diameter water rods 14 in the region for 7 fuel rods. The enrichment distribution in the axial direction is constituted of different 6 kinds of fuel rods. Fuel rods 1, 2, 3 has natural uranium (with enrichment of 0.711wt.%) in the elevation regions of 0/24 to 1/24 and 22/24 to 24/24. In the other regions, the rod 1 has uranium with enrichment of 1.6wt.%, the rod 2 has uranium with enrichment of 1.3 and 1.5wt.% and rod 3 uranium enrichment of 1.3wt.%, respectively. Fuel rod 4 has natural uranium in the whole length, fuel rods 5 has depleted uranium of 0.2wt.% in the whole length and fuel rod 6 is of a short natural uranium fuel rod P. By this, even in an initial loading core aiming at high burnup, maximum linear power density is suppressed and long term continuous operation is made possible.
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