Seismic restraint means for radiation detector

Seismic restraint means are provided for mounting an elongated, generally cylindrical nuclear radiation detector within a tubular thimble in a nuclear reactor monitor system. The restraint means permits longitudinal movement of the radiation detector into and out of the thimble. Each restraint means comprises a split clamp ring and a plurality of symmetrically spaced support arms pivotally mounted on the clamp ring. Each support arm has spring bias means and thimble contact means eg insulating rollers whereby the contact means engage the thimble with a constant predetermined force which minimizes seismic vibration action on the radiation detector. (author)