Mixer spool effectiveness and pressure loss evaluations for low pressure reactors

摘要

Process tube and fuel jacket failures due to corrosion are recurring problems in the operation of nuclear reactors and are generally accentuated by coolant temperature increases. Water mixer fuel pieces which mix the subchannel flow streams are used in the production reactor fuel columns to reduce peripheral and hole-to-annulus coolant temperature disparities and, thus, to reduce corrosion problems. The mixer in current use is approximately two inches long and is attached to a six inch fuel piece. This fuel element with attached mixer is generally placed as the seventh fuel element from the downstream end of the charge. A new miser design has been proposed and is shown. Its basic operation is similar to that of the present design (H-3-17493) in that it exchanges the flow stream in the central hole with fluid in the annulus. The standard mixer utilizes circular interchannels to perform the fluid interchange, whereas, the new mixer uses larger channels of rectangular cross-section. The purpose of this study was to evaluate the mixing effectiveness and pressure loss characteristic of this new mixer and to compare it with the performance of the standard mixer.