Experimental investigations of the hydraulic field in wire-wrapped LMFBR core assemblies☆

Abstract An investigation of the hydraulic behavior of wire-wrapped fuel and blanket assemblies was conducted in an air flow test facility. The test section was a large scale sector (slightly more than one-sixth) of prototypic fuel and blanket assemblies of the Clinch River Breeder Reactor Plant; the scale factor was approximately 11:1 and 5:1 for the fuel and blanket, respectively, thus allowing a very large number of measurements within each subchannel. The purpose of these experiments is discussed along with a brief state of the art review; also discussed is the role of these tests on the core thermal-hydraulic design through calibration and verification of the analytical codes employed in the design. The test section and experimental procedures are illustrated. Experimental results are discussed in detail: static pressure gradients; local and average cross flow through the gap spacing between rods as a function of the wire wrap position and at all typical locations in the assembly; detailed axial velocity mappings in the inboard and peripheral channels. The physical significance of the results is interpreted and the fundamental difference in the hydraulic behavior of fuel and blanket assemblies is pointed out, discussed and explained in terms of fundamental geometric parameters. The application of the fuel assembly data to calibration/verification of subchannel analysis and distributed parameter codes is presented in detail. A quantitative model of the cross flow driving forces is elaborated as the starting point for a comprehensive phenomenological modeling of the hydraulic behavior of wire-wrapped assemblies.