Spacer for LMFBR's fuel assembly

The use of wire wraps or grid spacers is the alternative measures for radially supporting the large number of fuel elements within an LMFBR's fuel assembly. The wire wraps are usually preferred on account of their smaller pressure loss, while the grid spacers are considered to effectively prevent the bundle-duct interaction and the wear marks on the fuel elements which are inevitable with the wire wraps. Hence it has been desired to develop low-pressure-loss grid spacers. This paper, introducing the effective flow cross section coefficient β, represents the method of evaluating the grid spacer pressure loss. The correlation between β and the design parameter of grid elements was systematically investigated in a water-flow test. As a result, an advanced grid spacer with pressure loss as low as that of wire wraps have been developed. (author)