Nuclear fuel pellet retainer

A fuel pellet retainer spring assembly is disclosed for insertion to the open unsealed end of a fuel rod. The assembly includes a locking sleeve (S) having a normal radial diameter exceeding the inside radial diameter of the fuel rod cladding (6). This sleeve (S) is compressed to a diameter less than the inside diameter of the fuel rod cladding (C). Thereafter, the sleeve (S) is inserted. In the preferred embodiment, a washer (W1) and coil spring (40) precede the sleeve (S) into the fuel rod. The sleeve (S) is inserted and thereafter allowed to expand and key to the inside wall of the cladding (C). When the sleeve (S) is in place, the coil (40) bears against the inside portion of the radial sleeve (S) and forms the surface from which a fuel pellet biasing spring (40) maintains fuel pellets (P) within the unsealed fuel rod.