NUCLEAR FUEL ELEMENT

摘要

A top end plug design for a nuclear fuel rod or control rod that maximizes the fuel rod length and internal volume for high burn-up, but limits plenum spring melting for eutectic formation margin. The press fit length of the top end plug is increased to increase the distance from the center of heat from the TIG welding process that seals the end plug to the cladding, to the back face of the end plug. A hole in the back of the end plug is enlarged to recover the volume loss from the press fit length increase.

主权项

1. A nuclear fuel assembly element comprising:
a tubular cladding; a lower end cap closing off a lower end of the tubular cladding; an upper end cap closing off an upper end of the tubular cladding, wherein a lower end portion of the upper end cap has a diameter that fits within the upper end of the tubular cladding and extends down into an interior of the tubular cladding a preselected distance and an upper end portion of the upper end cap is welded to the upper end of the tubular cladding; a measure of an active material occupying a portion of the interior of the tubular cladding between the lower end cap and the upper end cap; a spring positioned in the interior of the tubular cladding between the upper end cap and an upper surface of the measure of active material, with one end of the spring against the lower end portion of the upper end cap and another end of the spring biasing the active material towards the lower end cap; and wherein the preselected distance is selected so that heat from a welding process that is employed to weld the upper end portion of the upper end cap to the upper end of the tubular cladding is dissipated at an interface of the one end of the spring and the lower end portion of the upper end cap to an extent that avoids substantial melting at the interface.