Water tubes arranged in cross-like pattern in a fuel assembly

This patent describes a nuclear fuel assembly having upper and lower tie plates, elongated fuel rods extending between the tie plates and disposed in side-by-side relationship so as to form an array of spaced fuel rods and a tubular channel surrounding the fuel rods so as to direct flow of coolant-moderator fluid along the fuel rods of the assembly. The improvement described here comprises: elongated water tubes disposed between the upper and lower tie plates and arranged in a cross-like pattern spaced among the fuel rods so as to divide the array of fuel rods into subarrays thereof; the water tubes defining spaced-apart individual coolant-moderator fluid flow paths lengthwise through the assembly and being spaced apart from and structurally unconnected to one another along their lengths between the upper and lower tie plates. This allows unobstructed coolant-moderator fluid cross flow between the subarrays of fuel rods at all levels along the lengths of the water tubes; each of the water tubes being one of three different types with at least one water tube being from each of the three different types, such different types being a standard water rod, a tie rod, and a spacer capture rod. The water tubes of the tie rod type interconnect the upper and lower tie plates