In April 1961, Atomic Power Development Associates (APDA) produced the “Summary of the APDA Fuel Development Programs.” Chapter XVII described a paste fuel concept. The report noted that there are “advantages inherent in a mobile-fueled reactor.” Patent number 3,169,117, entitled “Nuclear Reactor Paste Fuel Composition,” was issued on May 9, 1961. In May 1964, Argonne National Laboratory produced the “Catalog of Nuclear Reactor Concepts.” The chapter concerning paste fuels concluded: “The few paste-fuel concepts developed to date and the present early stages of such developments show that considerably more work probably will be required before the paste-fuel concept can be considered for commercial development.” This monograph enlarges upon and quantifies the APDA concept, which appears not to have been pursued. Additional passive safety concepts that might also eliminate the need for control assemblies are described. Several important consequences of continuously processed fuel that are not discussed in the APDA report are described in this paper, in particular, that the “iodine pit” startup control instability can be eliminated.