| 摘要 |
PURPOSE:To improve the combustion efficiency of fuel by increasing the average enrichment or plutonium enrichment of uranium 235 in the upper part of a fuel assembly to the value higher than in the lower part and incorporating a burnable poison into the upper part in the amt. larger than in the lower part. CONSTITUTION:The average enrichment or plutonium enrichment of the uranium 235 in the upper part of the fuel assembly 1 is increased to the value larger than the average enrichment or plutonium enrichment of the uranium 235 in the lower part and the amt. of the burnable poison to be incorporated into the upper part is increased to the value larger than the amt. of the burnable poison to be incorporated into the lower part. The output distribution of the reactor core can, therefore, be peaked in the lower part in the initial period of cycles and peaked in the upper part in the end period of the cycles. The conversion rate of plutonium is increased by the presence of plutonium 240 to enable efficient combustion of the fuel and, therefore, the economic efficiency of the fuel is improved.
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