| 摘要 |
PURPOSE:To improve the average uranium enrichment level and set the extraction average burnup to 45GWd/t or above without causing problems on gadolinium fuel rods when the maximum uranium enrichment level is limited to 5.0wt.% in the fuel assembly for a boiling water reactor. CONSTITUTION:The average uranium enrichment level of fuel rods 20-23 is set to 4.25wt.% above 4wt.%, the ratio of Gd rods 23 against all fuel rods is set to 23% in the range of 20-30%, and its enrichment level of 4.45wt.% is set between the pellet maximum uranium enrichment level and the pellet minimum uranium enrichment level. The ratio of the fuel rods 20 having the maximum uranium enrichment level of 5.0wt.% among the fuel rods except for the Gd rods 23 is set to 75-82%. The average uranium enrichment level of the enriched fuel section except for blanket regions at the upper and lower end sections is 4.75wt.%, and its ratio against the pellet maximum uranium enrichment level emax/emean is 1.05 below 1.16.
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