PURPOSE: To prevent leakage by increasing the hardness on the outer surface at the lower part of outer shell, i.e., a cladding pipe, for a fuel rod as compared with other parts using an ion beam thereby suppressing the fretting abrasion of fuel rod due to foreign matters in cooling water.

CONSTITUTION: Hardness is increased by 10-40% on the outer surface of a cladding pipe 6 for a fuel rod l within a range L of about 200mm from the lower end part, preferably about 100mm above and below the intermediate part of a designated grid 2a at a lowermost part, as compared with other parts. An ion plating method wherein reforming is performed independently, an ion implanting method, or an ion beam mixing method combining ion deposition and ion irradiation is employed as the method for hardening the outer surface of the fuel rod coating pipe 6 using an ion beam. When the ion plating method is employed, for example, particles to be deposited are partially ionized and accelerated forcibly through an electrostatic field and then radiate the surface of a substrate thus forming a film thereon. This constitution enhances abrasion resistance.