The invention relates to nuclear power and can be used in the manufacture of fuel elements for nuclear reactors. Embodiments of a welded joint between a fuel element casing and a plug comprised of high-chromium steel are proposed, providing for increased durability of the sealing of nuclear reactor fuel elements as a result of the formation of a high quality welded joint between the casing and the plug without the need for subsequent heat treatment of the weld seam, which simplifies the manufacturing process. This is achieved through the formation of a ferrite phase in the metal of the seam by adjusting the structure of a joint between the casing and the plug of ferrite-martensite and ferrite steels in various combinations and by keeping the necessary ranges of the size ratios to ensure the formation of the aforesaid phase.