| 摘要 |
PROBLEM TO BE SOLVED: To restrain uniform white corrosion to allow safe use for a long period, by regulating average crystal grain sizes of a zirconium alloy and the thicknesses of an outer surface layer, in the outer surface layer in the vicinity of an welded part between a cladding pipe body and an end cock and in a thermally affected part. SOLUTION: An upper end cock 3 and a lower end cock 4 are welded respectively to end of a cladding pipe body 1 comprising a zirconium alloy and for filling nuclear fuel pellets 2 to be sealed, and a nuclear fuel cladding pipe is formed thereby. Average crystal grain sizes of the zirconium alloy in a welded part between the cladding pipe body 1 and the end cocks 3, 4 and an outer surface layer in the vicinity of a thermally affected part are made 3μm or less to improve corrosion resistance against oxidation corrosion. Thicknesses are made 3-50μm in the welded part and the outer surface layer in the vicinity of the thermally affected part, in which the average crystal grain sizes of the zirconium alloy are restrained. Resistance against the oxidation corrosion is not continued when the thicknesses are thinner than 3μm, and creep elongation of the cladding pipe body 1 having about 0.9 mm of thin wall thickness is affected when the thickness exceeds 50μm.
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