Auxiliary system for assisting a movement system of fuel elements of a nuclear reactor

An auxiliary system (5) for assisting a movement system of fuel elements of a nuclear reactor comprises a movable guide tool (20), extending substantially along an axis (X) and cooperating with a grab member (2) for guiding a fuel element (4) coupled to the grab member (2); and a movement and lock device (21) acting on the tool (20) for connecting in a releasable manner the tool (20) to the grab member (2); the device (21) comprises: male and female connection elements (11, 34) cooperating for releasably coupling the tool (20) to the grab member (2) axially in a first translation direction along the axis (X); and a releasable safety mechanism (38), movable for locking axially the tool (20) with respect to the grab member (2) in a second translation direction along the axis (X), opposite to the first translation direction, and for preventing disengagement of the male and female connection elements (11, 34).