group of fuel elements for nuclear reactors nuclearia fast neutrons

摘要

Fuel rods are mounted as parallel bundle in a vertical case of parallelepiped section. At its upper end the case has an extension sleeve, the lower part of which is of a greater thickness than the fuel rod case, to form part of the neutron protection of the reactor. The sleeve is connected to the end of the case by a disengageable connector, to enable the sleeve to be removed from the case when the fuel rods are spent. Connector may be simply two transverse pins, or a bayonet system with locking screw, or a system in which teeth project into recesses of the same profile and are locked in place by an exterior collar engaged in a common groove. Assembly used in reactors having prim. and sec. Na cooling systems, the cases forming part of the prim. sodium circuit. The neutron protection sleeve is normally stripped off the case during reprocessing of the spent fuel element, and is lost. The connector enables the sleeve to be removed for reuse.