End plug for nuclear fuel rod

An end plug has a large-diameter portion having an outer diameter substantially identical with the outer diameter of a cladding tube substantially at the axial center. A cylindrical fitting portion having an outer diameter substantially identical with the inner diameter of the cladding tube is formed integrally to one side of the large-diameter portion. A columnar protrusion is protruded outwardly at the other side of the large-diameter portion. A conical tapered portion having an inner diameter substantially identical with the inner diameter of a cladding tube and tapered toward the top end is formed on the base end of the fitting portion on the outer circumferential surface on the side of the large-diameter portion. A groove having a diameter smaller than the outer diameter of the fitting portion is formed on the top end of the conically tapered portion. The end plug is inserted under pressure and fitted to an opening end of a cladding tube. The meeting surfaces of the end plug and the opening end are welded. Since the tapered surface of the conically tapered portion functions as a backing (backing effect), the quality of welding can be stabilized without causing remarkable depression. (I.N.)