Fret resistant fuel rod with zirconium oxide layer.

摘要

Zirconium alloy nuclear fuel rods (20) are protected from fretting damage due to debris captured by the fuel assembly (34) and agitated against the fuel rod (20) at and below the bottom supporting grid (32) of the fuel assembly (34). This is accomplished by preliminarily forming a thickened oxide layer (24) in the area to be protected, more particularly by heating the rod (20) in an oxygen-containing atmosphere and thereby forming a thickened zirconium oxide (ZrO2) surface layer (24) between the bottom grid (32) and the end (42) of the fuel rod (20). The thicker portion (24) can be 3 to 9 microns in thickness, extending four to eight inches from the end (42) of the tube, to a point (26) at which the rod (20) is supported by a receptacle in the bottom grid (32). The portion (24) to be protected is heated to a temperature of 750 to 1,600 DEG F (400 to 870 DEG C) for up to one hour, for example by electromagnetic induction heating, furnace heating, electrical resistance heating and/or heating by application of laser radiation. The portion (24) can be enclosed in a vessel (54) during heating, in a gaseous environment with a gaseous pressure and/or oxygen concentration greater than normal atmospheric, or in oxygen with an inert gas. <IMAGE>