Abstract: An emergency device for the control of the displacement of a conveying carrier for a nuclear fuel assembly, in which the conveying carrier (6) moves under the effect of a push-pull chain (15) actuated by a driving mechanism causing, according to the direction, its winding on itself in spiral so as to pull the carrier, or its unwinding by forming then a carrier rigid pushing element, including a connecting member between the chain and the carrier, formed of two portions (27,38) connected to each other by a pin which can be broken when required in order to disconnect the two portions and to free the carrier from the chain.Breaking of the pin is due to the effect of a traction exerted remotely from the carrier on a control cable (16) such that, after breaking, the cable can apply a traction on the carrier so as to bring it back freely, independently of the chain, to a predetermined position.