Spacer grid using tubular cells
A spacer grid specifically designed for accident tolerant fuel utilizing fuel rods with SiC cladding for implementation in pressurized water reactors. The spacer grid design allows for ease of SiC fuel rod insertion during the fuel assembly fabrication process by providing a smooth contact geometry. The co-planar support allows the fuel rods to be rotated axially more freely at the grid location than a conventional six-point contact geometry used in existing fuel assembly designs. The fuel rod support cells are attached at their corners which are shared between adjacent support cells.
1. A nuclear fuel assembly spacer grid comprising:
a plurality of tubular support cells having four walls and four substantially flat corners, wherein one of the flat corners is positioned between two of the walls, wherein at least a first pair of adjacent flat corners of adjacent support cells form a single integral corner between the adjacent support cells, wherein the single integral corner is a unitary one-piece corner that is shared between the first pair of the adjacent corners of the adjacent support cells, and wherein the unitary one-piece corner is a part of each of the adjacent support cells;
a spring supported from each of the four walls of each of the support cells that extends at least partially into the support cell, with the spring having a contact surface that contacts a fuel rod when the fuel rod is loaded in the support cell; and
a hard material coating on the contact surface that is as hard as or harder than SiC.
2. The nuclear fuel assembly spacer grid of claim 1 , wherein each unitary one-piece corner is not thicker than 0.018 inch.
3. The nuclear fuel assembly spacer grid of claim 1 , wherein the hard material coating is deposited by physical vapor deposition.
4. A nuclear fuel assembly comprising:
the nuclear fuel assembly spacer grid of claim 1 :
a fuel rod comprising a SiC coating and the fuel rod received within one of the support cells.
5. The nuclear fuel assembly spacer grid of claim 1 , wherein each of the four walls is bowed inwardly thereby forming a bend.
6. The nuclear fuel assembly spacer grid of claim 5 , wherein each bend is centered on an axis running along each respective spring.
7. The nuclear fuel assembly spacer grid of claim 1 , wherein each spring is positioned in a center of one of the walls.
8. The nuclear fuel assembly spacer grid of claim 1 , wherein the nuclear fuel assembly spacer grid is not welded.
9. The nuclear fuel assembly spacer grid of claim 1 , wherein the nuclear fuel assembly spacer grid is produced by additive manufacturing.
10. The nuclear fuel assembly spacer grid of claim 1 , wherein each spring is formed from two slits in one of the walls.