Nuclear fuel element

A tag capsule is disposed at a plenum portion of a long fuel can charged with nuclear fuel materials for preliminarily sealing tag gases such as krypton and xenon. Solid metals are contained in the tag capsule for fixing the tag gases. The solid metals comprise at least one of Fe, Ni, Al, Ti, stainless steel, alloys of transition metals and rare earth metals, alloys of transition metals and Ti, alloys of transition metals and yttrium, and alloys of transition metals and Zr each in the form of amorphous. The tag gases fixed in the solid metals are atoms or microbubbles. They can be released into fuel pins by elevating temperature after the manufacture of the fuel pins. Since krypton and xenon are not released from the solid metals at normal temperature, the capsule can be assembled in a normal atmosphere. Additionally, it is not necessary to take the corrosion of the fuel can into consideration. (T.M.)