U.K. COMMERCIAL DATA EMPLOYED IN FFTF FUEL PIN AND SUBASSEMBLY CONCEPTUAL DESIGN

摘要

The fuel pin design from diametral growth viewpoint must be concerned with its relationship to the subassembly. The fuel pins are spirally wrapped with spacer wire and then assembled into a hexagonal bundle, fixed at one end with a grid spacer. Clearances between the wires and the adjacent fuel pins are small. During irradiation, the fuel pin diameter increases. In general, this diameter increase may consist of two components: One component is clad swelling and the other, if present, is mechanical strain in the clad resulting from the fuel swelling. This increased mechanical strain causes an increase in spacer wire tension. This in turn causes a larger spiral deflection of the fuel pin. Because all pins are in a similar environment, the pins will have a similar spiral deformation. Therefore, the entire pin bundle will have a spiral deformation pattern.