Anti-vibration flux thimble

A thimble for accommodating a movable in core detector and which resists vibrations caused by turbulence in the coolant flow of a nuclear reactor includes a portion of preselected length with an increased outside diameter. The conventionally-sized thimble is sheathed with a tubing adapted for insertion within the reactor, the tubing at a leading end thereof being fixed to the conventionally-sized thimble and at a trailing end thereof being slidingly coupled to the conventionally-sized thimble. A bullet-shaped member seals the leading end and facilitates its insertion. (author)