double - d water rod for fuel bundle 9 9 village

摘要

In a nuclear fuel bundle having a lower tie-plate, an upper tie-plate and a surrounding channel therebetween, an improved water rod is disclosed for preferable use when fuel rods held between the tie-plates are placed in a 9 by 9 array. Typically, seven fuel rods are omitted centrally of the 9 by 9 array with the middle or fifth row having three rods removed and paired rods being removed in the 4th and 6th row with displacement of the removed pair towards opposite corners. Into the volume created by the removal rods, there are placed two "D" sectioned rods, the "D" rods each being round in cross-section except for a truncating chord, this truncating chord defining the straight back of each "D". In the preferred embodiment one of the "D" water rods is provided with spacer tabs for maintaining spacers separating the fuel rod at their correct elevations. This rod is inserted with an alignment that permits the tabs to pass through the spacers. When the rod is fully inserted, it is rotated to a locking alignment so that the tabs capture the spacers. In this locked alignment, the straight back of the "D" is aligned to confront the straight back of the confronting "D" on the remaining water rod. When the remaining "D" rod is inserted with the backs confronted mutual, locking of both "D" sectioned water rod occurs. Provision is made for narrowing of the upper and lower sections of the water rods. The upper and lower sections, with reduced cross-sections are supported by the upper and lower tie plates, respectively. There results a water rod which efficiently utilizes the available space, has low manufacturing costs, and provides for spacer capture enabling ease of assembly and disassembly of the fuel bundle.