Nuclear Fuel rod

Purpose: To provide in a capsule a core having a coefficient of expansion larger than that of the capsule, and to break the capsule, and to break the capsule at a preacknowledged temperature, thereby accurately discharging a tag gas into a cladding tube. Constitution: The inner part of the lower end of a capsule made of quartz glass is processed into a conical shape having a tapered surface of 10 degrees, and a core made of a steel of SUS 316 is inserted therein. This core is caused to tightly adhere to the end part of the capsule by a stopper spring, and the tag gas is sealed through the end part at the opposite side and welded to form the capsule. When the capsule is inserted into the cladding tube and heated, the capsule breaks due to the difference in the coefficients of thermal expansion, and the tag gas is discharged in the cladding tube. (Sekiya, K.)