| 摘要 |
PROBLEM TO BE SOLVED: To establish a method for identifying a fuel channel box with different specifications and to avoid the erroneous fitting of the fuel channel box in terms of structure by changing the dimensions and shape of the fuel channel box at a region where upper and lower tie plates and the fuel channel box are engaged each other. SOLUTION: When the outer width of an upper tie plate 14 of a normal fuel assembly 11 and the inner width of a fuel channel box 16 are set to A, and the outer width of an upper tie plate 24 of a fuel assembly 21 with a fuel channel box 26 containing a inflammable toxic substance and the inner width of the fuel channel box 26 are set to C, the fuel channel box containing the inflammable toxic substance cannot be inserted into the normal fuel assembly 11 due to A>C. Similarly in lower tie plates 13 and 23, when the outer width of the lower tie plate and the inner width of the fuel channel box are set to B and D, respectively, no fuel channel box without any inflammable toxic substance can be inserted into the fuel assembly 21 with the fuel channel box containing the inflammable toxic substance due to B<D.
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