Tubular fuel cluster

In a liquid cooled nuclear reactor having a plurality of fuel channels extending in substantially parallel mutually spaced relation, each channel having an inlet for liquid coolant adjacent one end thereof and an outlet for liquid coolant adjacent the other end thereof wherein a said channel and the fuel charge therein comprises an elongated cylindrical pressure tube having a said coolant inlet and a said coolant outlet connected therewith to receive and discharge respectively pressurized coolant liquid, a plurality of fuel bundles in abutting end-to-end relation within the channel, each bundle comprising a plurality of substantially mutually parallel longitudinally extending fuel elements positioned substantially parallel with the longitudinal axis of the channel in symmetrical spaced relation to substantially transversely fill the channel, including a plurality of hollow tubular elements each having an axially extending internal coolant flow path extending through the element interior and an external coolant flow path about the element exterior surface, and a plurality of apertured flow restriction plate means secured to the ends of said fuel bundles each plate means having a flow restricting orifice in axially aligned relation with a respective element internal flow path to limit the flow of coolant therethrough, the plates being thus spaced along the length of said channel in flow controlling relation with said internal coolant flow paths to provide in use a progressive, controlled pressure drop between said channel coolant inlet and said channel coolant outlet to substantially preclude flashing of said liquid coolant from a liquid phase to a gaseous phase on passage through the interior of the hollow elements of said fuel charge.