| 摘要 |
PROBLEM TO BE SOLVED: To provide a BWR fuel assembly of high burnup of 50 GWd/t or more allowing the increase of local peaking under the 5 wt.% limit of highest enrichment and securing a thermal operation margin. SOLUTION: Fuel rods are divided in standard fuel rods 1 with a fuel effective length equal to the fuel effective length, and partial length fuel rods 2 with short fuel effective length. The fuel rods are further divided in fuel rods U not including burnable poison, and fuel rods G including burnable poison. The fuel rods G including burnable poison are divided in whole length poison inclusion fuel rods Ga including the burnable poison in the whole region excluding the upper and lower ends, and partial length poison inclusion fuel rods Gb including burnable poison only in the lower region L. The fuel rods Gb are provided in the number of the integer approximated to NGb obtained by NGb =(NGa .N2 )/N1 , wherein N1 is the number of the standard fuel rods 1, N2 is the number of partial length fuel rods 2, NGa is the number of the full length poison inclusion fuel rods Ga, and NGb is the number of the partial length poison inclusion fuel rods Gb.
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