| 摘要 |
PROBLEM TO BE SOLVED: To make it possible both to make a void coefficient become negative while keeping a conversion ratio nearly 1 and to reduce fuel costs through the increase in reactivity by setting the clearance between fuel rods on the outermost periphery in a fuel assembly and a channel box at a specific value or more. SOLUTION: A core is constituted so that the average value of the clearances W1 and W2 between the outermost periphery of a fuel assembly and a channel box 10 can be 2 mm or more. Then, four uranium (U) fuel rods 4 are placed at each corner section in the outermost periphery 10a of the fuel assembly-- sixteen U fuel rods 4 are placed in total--, and forty-four U fuel rods 3 in total are located on the outermost periphery and the second outermost row. Moreover, four plutonium (Pu) fuel rods 2 in total are placed inside the U fuel rods 4 in each corner section and 183 Pu fuel rods 1 are located inside the Pu fuel rods 2 and the U fuel rods 3 and 4. These fuel rods 1, 2, 3 and 4 are laid out in the form of a closely packed triangle lattice in 17 rows in total in the channel box 10 shaped like a quadrangular prism.
|
