The need for criticality control in the proposed reprocessing of slightly enriched non-production fuels at Hanford has led to the development of a geometrically "safe", vertical tube, recirculating dissolver. A study of the nitric acid dissolution of uranium dioxide in a pilot plant dissolver of this type is reported here. The study was pointed toward the comparison of uranium dioxide dissolution rates in a batch and a recirculating dissolver and the definition of hydraulic problems associated with the recirculation of nitric acid, by air lift, technique through beds of reacting uranium dioxide.

The Hanford water treatment plants were operated for a number of years with alum as a coagulant and activated silica as a coagulant and a polyacrylamide as a filter conditioning agent. (other polyelectrolytes may be used.) Sufficient time has elapsed to make a comparison of the two methods of operation valid and useful. Such a comparison is the purpose of this paper.