Patent ID: 8410423

Claim:
A nuclear gauge, comprising: a gauge housing having a vertical cavity therethrough and a base, the base including a base track portion disposed therein; at least one radiation detector located within the housing and adjacent to the base of the housing; a vertically moveable source rod extending into the cavity of the gauge housing; a radiation source operatively positioned within a distal end of the source rod, the source rod being vertically extendable and retractable to a plurality of predetermined source rod positions so as to change the spatial relationship between the radiation source and the at least one radiation detector; and a radiation shield assembly comprising: a sliding block positionable to move laterally between two positions, a first position blocking a distal end of the vertical cavity of the gauge housing such that radiation is shielded from exiting the cavity and a second position adjacent to the vertical cavity and allowing vertical movement through the radiation shield assembly; a track configured to receive the sliding block and guide movement of the sliding block; a spring engaging the sliding block and biasing the sliding block into the first position; a safety shield, the safety shield including a shield track segment therein that comprises at least a portion of the track; and at least one replaceable sliding guide positionable within the track adjacent the sliding block, the at least one replaceable sliding guide configured to reduce friction as the sliding block moves between the first position and the second position, wherein the at least one sliding guide is insertable into at least one cavity in the track such that an outer surface of the at least one sliding guide is flush with at least one outer wall of the track.