Image Number 4 for United States Patent #4855100.
A reconstitutable control rod spider assembly includes a spider structure, control rods, and attachment joints for detachably fastening the control rods to the spider structure. Each attachment joint includes a connecting finger of the spider structure having a central bore extending therethrough and a pair of opposing flat segments formed on the interior thereof, and an elongated upper end plug of each control rod inserted through the finger bore and having a pair of opposing flat sectors formed on the exterior thereof beng interfitted with the opposing flat segments on the connectng finger to retain the control rod in a predetermined angular position relative to the finger. The upper end plug also has an externally-threaded portion formed on the exterior thereof above the flat sectors and being disposed above the connecting finger, and a pilot aligning portion formed on an outer terminal end thereof above the externally-threaded portion. Also, a securing nut having a central bore, an open bottom end and a closed top end, is inserted over the pilot portion and the externally-threaded portion of the upper end plug and has a radially flexible and expandable thread-defining element captured in the bore of the nut. The element is detachable fastened on the externally-threaded portion of the upper end plug to secure the upper end plug to the connecting finger.