Patent Number: 052710548
Section: description

DETAILED DESCRIPTION OF THE INVENTION The numeral 10 generally designates a fuel assembly grid corner region which incorporates the principals of the invention. Evident are fragments of two perimeter strip pieces, 12 and 14 joined by a perimeter strip seam weld 16 which are formed to overlap at the extremities of flat plane side sections thereof, 18 and 18', respectively. Another flat plane section 20 of the strip 12 is connected to the flat side section 18 by means of a transverse continuous corner bend 22 of varying radii, with its outer longitudinal end portions 24 having a greater radius that its inner portion 26. At the top and bottom margins of the flat side sections 18 and 20, are upper and lower anti-hang-up tabs 28 and 28', respectively. In flat plane section 20 of perimeter strip piece 12 with its perimeter in said flat plane is a stress-relieving slot 30 which extends an equal slot perimeter length on either side of the longitudinal center line of the flat section 20. The length of slot 30 is approximately 1/3 to 1/2 of the width of the flat section 20. The width of slot 30 is preferably less than twice the thickness of the strip material which is typically a stainless steel such as "Inconel 625" or zirconium alloy such as "Zircaloy 4". As a comparison of FIG. 1 and its' flat sections 18 and 20, with FIGS. 2 and 3, and their flat sections 20 and 32, will show, it is possible to have transverse slots 30 in the flat sections on each side of the bend or bend line 22. This depends on whether the flat section 18, 20 or 32 is interrupted by fuel rod support arches 34 or by springs 36. The flat side sections 20 and 32 with arches 34 adjacent bend line 22 having much less cut-out periphery for stress relief that the flat side 18 which has a large spring 36 cut-out adjacent bend line 22 which will inherently stress relieve the corner-bend 22. It will thus be seen that a perimeter strip grid cornerpiece of increased flatness having two flat-side sections on either side of transverse bend line 22 is provided whether or not the fuel rod support structure on one or both sides of said bend line is a small cut-out for arches 34. This stress-relief is accomplished without a significant weakening of the strip in the portion or area near bend 22 containing the slot 30. It therefore maintains its required rigidity.