Design of LMFBR fuel handling machine

Includes bibliographical references (page 45)This study determined an acceptable design of a fuel handling\ud machine to refuel future liquid metal fast breeder reactors (LMFBR).\ud To date, approximately seven fuel handling machines have been designed'\ud and built for small scale liquid metal cooled reactors. Limitations\ud of these previously operated handling devices eliminated their use for,\ud the LMFBR. A study was therefore performed to establish a simple\ud machine to meet the more stringent design safety criteria for the future LMFBR spent fuel assemblies. This study was however restricted\ud to only those aspects of the design believed to be particularly\ud critical for such a fuel handling machine. Once these critical design:\ud aspects are satisfied, the detailed design can be prepared by more\ud conventional design techniques. Fuel assemblies from the reactor must be removed periodically and, replaced with new fuel assemblies. The heat generated by the fission\ud products in these spent fuel assemblies can cause the assemblies to\ud melt unless adequate cooling is provided. The cooling system is therefore the most critical component of the fuel handling machine.\ud Since provision for adequate heat removal from a spent fuel assembly\ud is the most critical aspect of the design, two independent heat\ud removal systems are suggested to provide near complete redundancy.\ud Each heat transfer system must be capable of removing the entire 27 Kw\ud generated internally in the spent assembly being removed. Sodium in\ud the liquid state is used to transfer heat from the fuel assembly to\ud the outside surface of the transfer container. In one of the two\ud independent cooling systems, all of the decay heat is transferred froi\ud the outside surface of the transfer container to an air-cooled cold wall\ud by radiation. In the second cooling system, cold argon is pumped\ud around the transfer container and through an air-to-argon heat\ud exchanger to remove all of the decay heat of the spent fuel assembly\ud by convection. Selection of the shielding material and the shielding dimension\ud is the second critical design problem considered. The choice for\ud shielding material is based on raw material costs, ease of fabrication,\ud and shielding performance. No definitive answer exists to this\ud selection problem, but this study showed that cast steel would be the\ud best shielding material for this application. A flexible member must be used to raise and lower the fuel handling machine's grapple into and out of the reactor liquid sodium.\ud To date none of the liquid metal reactor fuel handling machines have\ud been designed with this constraint. The design of this component\ud represented the third critical aspect of the design of the machine.\ud The results show that log chain would be the best choice of the five\ud alternative considered. A design concept for a IMFBR fuel handling machine evolved as a\ud consequence of the results obtained by examination of the three\ud critical design considerations discussed above