GB1303836A - - Google Patents

Abstract

1303836 Fuel elements COMITATO NAZIONALE PER L'ENERGIA NUCLEARE 5 Feb 1970 [6 Feb 1969] 5623/70 Heading G6C A spacer grid for use in a fuel element comprising an assembly of parallel, spaced fuel rods consists of laminar members disposed end-on to the coolant flow, the contact of the members with each fuel rod being along three generatrices thereof which are spaced at equal angles from one another, each rod being rigidly supported at two of the contact lines and elastically at the third. In the embodiment shown in Figs. 1 and 2, the grid is formed from two types of laminar members having the same height h and crossing each other at right angles. The members 2 of the first type, of which there are twice as many as of the second type, are made of a thin metal band along which at regular intervals equal to twice the side a of the square grid mesh, two parallel lengthwise incisions are made at a distance from the edges of the band equal to “ the band width. The band is then pressed in such a way that the portion between the two incisions forms a bridge projecting from one side of the band, while the other portions form similar narrower bridges projecting from the other side of the band. The members 3 of the second type are also made of a thin metal band which at regular intervals equal to the side a of the square grid mesh is incised and pressed similarly to member 2, the bridges however being shallower and having an outwardly arcuated profile for greater elasticity. The members 2, 3 are interlocked at right angles by means of vertical slits extending for ¢ their height, a short tubular element 14 provided with four slots 90 degrees apart being inserted at each crossing of the members 2, 3. Each fuel rod 1 abuts against the mesh structure along three generatrices of the rod for a length equal to ¢ L. The corners 4, 5 of the bridges of the members 2 provide rigid support while the ridges 6 of the profiled bridges of the members 3 provide elastically yielding support. In other embodiments, the bridges are formed by rectangular inserts with rounded off corners such as may be obtained by sawing a thinwalled tube of rectangular cross-section into sections (Fig. 4, not shown) and the structural members corresponding to the members 3 of the first embodiment comprise flat bands inserted between two bands corrugated in such a way that curved vertical ridges are obtained facing the fuel rods (Fig. 6, not shown).