HIGH TENSILE STRENGTH ZIRCONIUM ALLOY CONTAINING BISMUTH AND NIOBIUM

摘要

PROBLEM TO BE SOLVED: To obtain an alloy suitable for the cladding of a nuclear fuel element by allowing it to have a specified compsn. contg. Bi, Nb, and the balance Zr. SOLUTION: The compsn. of an alloy is composed of, by weight, 3 to 6% Bi, 0.5 to 3% Nb, and the balance Zr. This alloy is used as the inside layer of a clad pipe of two layers or the inside layer of a clad pipe of = three layers having high strength, improved creep behavior and reduced parasitic neutron absorption. As a concrete example, a nuclear fuel rod for a pressurized water reactor is composed so as to have metallic pipe fuel rod cladding 110 composed of an external layer ill formed from an alloy contg. Mo, Bi, and the balance Zr and an internal layer 114 metallurgically bonded to the inner wall 113 of the external layer 111. The alloy contains =0.1% silicon for additional strength and grain refining. Moreover, for the control of the grain size, 0.008 to 0.02% carbon may be incorporated therein.