خلاصه اختراع : The nuclear reactor fuel assembly comprises a bundle of fuel elements installed in the frame formed by guide channels and retention grids, bottom nozzle, a removable head comprising collet tubes, upper mantle, a support element, and springs. Collet tubes are made of two coaxially arranged tubes, the lower and upper, with the provision of movement of one pipe relative to another. On the side surfaces of each pipe, stops are made that interact with each other and provide the selected length of the collet pipe, while the pipe passing through the hole in the plate of the operation mantle has a rigid fastening to the specified plate. The support element is a pipe with rigidly fixed plate interacting with the spring, and the upper mantle is made in the form of a pipe located coaxially to the pipe support element with necessary mounting and having a gap at the bottom of bosses, interacting with springs, and in the upper part of the support that interacts with the tube support element, with the plate supporting element opposite each of the bosses of the upper mantle is provided with holes, the shape of which conforms to the shape of the boss of the upper mantle, the margin between the hole in the plate supporting element and the boss is not less than the mounting gap between the upper tube mantle and tube support element. For mounting and dismounting the removable head, a device can be used in accordance with RF patent No. 2075118. The proposed improvement in the design of the removable head of the fuel Assembly makes it possible to reduce its dimensions while maintaining the fixation of the fuel Assembly in the reactor's internals at the time of damping the decreasing regulator.