Nuclear core component hold-down assembly

摘要

A plate mounted fuel assembly hold-down system (88) that provides a defined channel for both the insertion and removal of reactor head mounted, fixed in-core detector instrumentation, provides a guided path for the fixed in-core detector during insertion, and shields the instrument shroud against coolant cross flow. The hold-down assembly (88) includes a base plate (90) that seats on the adapter plate (84) of the fuel assembly (22) and has openings that align with the control rod guide thimbles. A hollow sleeve extends through and below a central opening (92) in the base plate to mate with the fuel assembly instrument thimble (110). The sleeve extends above the base plate and through and above an upper core plate (40) of the reactor. A hold-down bar (96) is slidably mounted on the sleeve and is restrained below the top of the sleeve. A spring (98) is positioned around the sleeve and is captured between the hold-down bar and the base plate.