Run SM-3 covered 947.4 hours of which 669.2 hours were on slurry. Behavior of the system with slurry concentrations of 200 and 400 g Th/l were explored. Modifications made to the loop since the end of run SM-2 gave a flow of 360 gpm vs 230 gpm previously, and the blanket inlet nozzles were cut down from 2 in. ID to 1 1/2 in. sch 80 pipe, giving a velocity of 35 ft/sec out of the nozzles. The slurry was found to be suspended apparently uniformly in the blanket under the operating conditions and also with the flow reduced to 300 gpm by reducing the alternating current frequency. A further reduction to l97 gpm appeared to give conditions similar to run SM-2, with a much more marked concentration gradient in the blanket. The run was interrupted at 947.4 hr by a pump bearing failure. (auth)