X-SIAL USE ONLY FCD/TN-22 1. (2.73 This report was printed for circulation within the Research Establishment of the Australian Atomic Energy Commission. It has not been reviewed for general issue. It must not be quoted as an official document of the Commission. EUEL CYCLE DEVELOPMENT SECTION MATERIALS DIVISION PROCESSES FOR U02 PRODUCTION "07 R.W. HUBERY M.G. BAILLIE Issued August 1966 a ONLY ABSTRACT This report reviews the methods used for the production of uranium concentrates in Australia, and available processes for their purification and conversion to reactor grade uranium dioxide. CONTENTS Pa^e No. INTRODUCTION 1 PRODUCTION OP URANIUM CONCENTRATES 1 2.1 Australian Flants 1 2.1.1 Radium Hill - Port Pirie 2 2.1.2 Rum Jungle 2 2.1.3 South Alligator River 3 2.1.4 Mary Kathleen 4 2.2 The Importance of Solvent Extraction in Australia 5 2.3 Other Processes of Interest 5 PURIFICATION OF URANIUM CONCENTRATES 6 3.1 Main Production Methods 6 3.1.1 Solvent extraction - A.D.U. process 6 3.1.2 Solvent extraction - denitration process 7 3.1.3 Fluid-hed fluoride volatility process 7 3.2 Other Processes of Interest 8 CONVERSION TO URANIUM DIOXIDE 8 4.1 Existing Processes for the Production of Uranium Dioxide 9 4.1.1 Conversion of A.D..U.-derived UO^ to UO„ 9 4.1.2 Conversion of denitration-derived U0-, to UCL 10 J 4.1.3 Conversion of UF6 to U02 10 4.2 Other Conversion Processes 11 4.3 Products other than Oxide 11 COMMENTS ON URANIUM DIOXIDE PRODUCTION ROUTE 11 ACKNOWLEDGEMENT 12 REFERENCES 13 Contents (Continued) Figure 1. Flowsheet of Ore Treatment at Radium Hill and Port Pirie, S.A. Figure 2. Flowsheet of Ore Treatment at Rum Jungle, N.T. Figure 3. Flowsheet of Ore Treatment at Mary Kathleen, Qld. Figure 4. Production Flowsheets based on Purification of Yellow Cake "by Solvent Extraction Figure 5» Flowsheet for Production of UIV from Yellow Cake "by a Fluid- Bed Fluoride Volatility Route Figure 6. Alternative Flowsheets for Purification of Yellow Cake Figure 7« Flowsheets for Conversion of Purified IIBV to U00 1. INTRODUCTION The existence of uranium minerals in Australian ore-bodies has been known for many years, the first record of an occurrence having been made in 1894. Since then many other occurrences have been reported (AAEC 9th Annual Report 1961)• In 1944 when the search began in earnest due to urgent requirements "by the UICAEA, the only significant known deposits were at Mount Painter and Radium Hill in South Australia. This search resulted in the discovery of uranium at Rum Jungle in 1949 and later in the South Alligator Valley of the Northern Territory, where the United Uranium and South Alligator Uranium mines are located. It also resulted in the discovery of the Mary Kathleen deposit near Mount Isa in Queensland in 1954. These four areas have produced virtually all the uranium mined in Australia up to the present time. The first full-scale mining of uranium ore was commenced in November 1954 at Radium Hill. The concentrated ore was treated at Port Pirie in South Australia and yellow cake produced for sale overseas. This operation continued until 1962 when all operations ceased. Operations have also ceased at all the other major uranium production centres listed above, with the exception of Rum Jungle. This is due to the fact that contracts for supply of concentrate have been filled and suitable market opportunities are not available at this time. Production at Rum Jungle is oontinuing, the yellow cake product being stockpiled. Some effort has been made to obtain preliminary estimates of the likely cost of converting Australian yellow cake to U0p in Australia. This was done by means of a research contract to the Australian Mineral Develop­ ment Laboratories to cost plants of throughput 10, 50 and 200 tons per year of UOp (Goldney 1966). Their estimates have indicated that, at an output of 10 tons per year the cost of U0p would be $22.4 per kg, at 50 tons per year it would be $12.1 per kg, and at 200 tons per year it would be $9*9 per kg, based on a price of $3.20 per pound for U^0„ raw material. 2. PRODUCTION OF URANIUM CONCENTRATES By far the greater part of the world supply of uranium concentrates is recovered by a "conventional process" involving leaching, partial purifi­ cation and precipitation. Depending upon the composition of the ore the leaching step may be carried out under acid or alkaline conditions and purification achieved by solvent extraction, ion exchange or resin-in-pulp ion exchange. In some plants direct precipitation of pregnant leach liquors has been practiced but, except for the case of carbonate leaching, this technique is not favoured due to low efficiency and poor product quality. The final concentrate produced by all plants is in the form of yellow cake which contains 40 per cent, to 85 per cent, of U\0Q. Other processes are sometimes used where uranium is recovered as a by-product of monazite or phosphate treatment plants. These techniques have been surveyed by Clegg and Foley (1958) and will not be examined here. 2.1 Australian Plants Treatment plants in Australia are located at or close to the currently developed ore bodies. The flowsheets for these plants generally -2- follow the "conventional process" but all differ in minor ways to cope with local variations in the types of ores treated. 2.1.1 Radium Hill - Port Pirie Full-scale mining and metallurgical treatment was commenced at Radium Hill by the South Australian Government in November 1954. The con­ centrates were stockpiled until the beginning of chemical extraction at Port Pirie in August 1955. Total capital investment at Radium Hill was $10 million, and at Port Pirie about $3.6 million (South Australian Department of Mines 1961). The ore bodies at Radium Hill contained the little-knovm pseudo- mineral davidite as the principal uranium bearing species, although some carnotite was present to a small extent in the oxidised zone. The davidite was present as part of a complex association of intergrowths and ex- solutions of rutile, davidite, ilmenite, haematite and other heavy minerals. The minute scale of these intergrowths made selective pre-concentration of davidite uneconomic. However, some upgrading of the ore was obtained by heavy-media concentration of the heavy mineral intergrowths followed by selective flotation. The overall concentration achieved in this way was about a factor of ten, resulting in significant savings in transport costs to the chemical treatment plant at Port Pirie (Rodgers 1958) • At this plant leaching of the ore required the use of hot concentrated sulphuric acid to achieve satisfactory reaction rates. Removal of solids from the leach liquors was done in the conventional manner using counter- current decantation techniques followed by filtration. Primary purification was achieved by means of ion exchange columns arranged in duplicate for continuous production followed by two-stage pre­ cipitation of the yellow cake. After washing, extruding and drying this concentrate averaged about 72 per cent, by weight U-.0„ (Page et al. i960). The flowsheet for these plants appears in Figure 1. On completion of its contract for the supply of uranium oxide concen­ trate to the Combined Development Agency in December 1961, the South Australian Government closed the mine and treatment plants at Radium Hill and Port Pirie. In view of the low grade of the remaining ore bodies at Radium Hill, it seems unlikely that these facilities v/ill be used for uranium production in the foreseeable future. 2.1.2 Rum Jungle Uranium oxide has been in continuous production at Rum Jungle since September 1954. Management of the mining and treatment facilities has been successfully carried out on behalf of the Commonwealth Government by Territory Enterprises Proprietary Limited, a subsidiary company of Consoli­ dated Zinc Proprietary Limited. Three major ore bodies have been mined in this area so far, all of which contain uraninite (pitchblende) as the primary uranium mineral. White's deposit was the first to be mined and, in addition to uranium, produced approximately 8,000 tons of copper in the form of flotation and cementation concentrates. Significant quantities of copper were not encountered in the -3- mining of Dyson' s deposit or in the higher grade Rum Jungle Creek South deposit. The treatment plant at Rum Jungle, as originally constructed in 1954, was a conventional xDlant (Baker 1958) • Pachuca leaching with sulphuric acid was used followed by counter-current decantation, filtration, ion- exchange purification and magnesia precipitation in the same manner as for the contemporary plant at Port Pirie. Acid usage was rather high at 300 pounds per ton of ore due to the presence of phosphatic and dolomitic acid- consumers in the ore, The concentrate produced at this plant was approximately 53 per cent. U-.0o by weight (Page et ai. 19°0) which was an adequate grade for marketing in 1954• However, by 19^3 when the contract for sale of uranium oxide to the Combined Development Agency had been completed, it was evident that concen­ trate of this grade could no longer compete with that produced in newer plants, Work was therefore commenced on modifications to the plant. The principal alteration carried out at this time was the replacement of ion- exchange equipment by solvent extraction contactors employing a tertiary amine as extractant. As a result of these changes and a change of mill feed to ore from the Rum Jungle Creek South deposit, the grade of concentrate is now estimated to be in the range 80 to 85 per cent.