Received December 21, 1976 Accepted for Publication September 7, 1977 Experience with continued operation of failed mixed-oxide fuel pins in liquid-metal-cooled reactors or in-pile sodium loops is available from a variety of beyond-fuel-failure experiments. The phenomena and effects on a large reactor system of continued beyond-fuel-failure operation are not well understood, but, except for the release and deposition of fission products and the chemical reaction of sodium coolant to oxide fuel, leading to pin swelling, no failure propagation due to continued operation of failed fuel pins has been observed. For economic reactor operation, further investigations are needed to establish a catalog of fuel failure types, sizes, and locations to describe the time-dependent effects of continued operation on reactor operation, shutdown requirements, instrumentation, surveillance, circuit systems, contamination, maintenance systems, and plant efficiency.