Instrumentation thimble tube with instrument tube lateral restraint.

摘要

A nuclear fuel assembly for a pressurized water nuclear reactor has a spring (136) and dimple (134) structure formed in a non-radioactive insert tube (132) placed in the top of a sensor receiving instrumentation tube thimble (92) disposed in the fuel assembly (38) and attached at a top nozzle (102), a bottom nozzle (104), and intermediate grids (106). The instrumentation tube thimble (92) is open at the top, where the sensor (66) or its connection extends through the cooling water for coupling to a sensor signal processor. The spring and dimple insert tube (132) is mounted within the instrumentation tube thimble (92) and extends downwardly adjacent the top. The springs (136) and dimples (134) restrain the sensor (136) and its connections against lateral displacement causing impact with the instrumentation tube thimble (92) due to the strong axial flow of cooling water. The instrumentation tube (92) has a stainless steel outer sleeve (112) and a zirconium alloy inner sleeve (116) below the insert tube (132) adjacent the top. The insert tube (132) is relatively non-radioactivated inconel alloy. The opposed springs (136) and dimples (134) are formed on diametrically opposite inner walls of the insert tube (132), the springs (136) being formed as spaced axial cuts (138) in the insert tube (132), with a web (140) of the insert tube between the cuts (138) bowed radially inwardly for forming the spring (136), and the dimples (134) being formed as radially inward protrusions opposed to the springs (136). <IMAGE>