I 'The results obtained from radioactive elements appear likely to revolutionise the production of energy and, indeed, possibly the whole fabric of our civilisation.' — R N Kotee, South African Government Mining Engineer. 1915
Designed and edited by DM PubBc Relations Department of the Chamber of Mines of South Africa, PO Box 809. Johannesburg 2000. and the Atomic Energy Board of South Africa. Private Bag X256, Pretoria 0001, from whom further copies are available Produced with acknowledgement to the Nuclear Fuels Corporation of South Africa and the Council for Mineral Technology of South Africa
. Development of South Africa's uranium industry
THE first indications that gold deposits in the Wrtwatersrand area of South Africa hosted uranium were noted almost a century ago. In the late 1880s, Sir William Crookes, then chairman of the Royal Society, noted the green fluorescence of minute diamonds found in the gold-bearing ore which laboratory tests subsequently showed to be due to radioactivity. In 1923, R A Cooper, a Johannesburg metallurgist, analysed a concentrate from the City Deep Gold Mine, Johannesburg, and proved for the first time the presence of significant amounts of uranium in ores from the Wrtwatersrand.
"Among the waste," Cooper DrOF Milan, left, then Prime Minister of South Africa, reported to the Chemical, Metallurgical pressed the button to start up South Africa's first uranium and Mining Society of South Africa, "is extraction plant at West Rand Consolidated Mines, a variety of uraninite." Krugersdorp, on October 8, 1952. Assisting him was Sir His work aroused no excitement. George Albu, then Chairman and Managing Director of the Uranium was used only as a colouring General Mining and Finance Corporation agent and radioactivity was a curiosity under investigation by research workers thousands of kilometres away in Europe. Miners strove to extract only the immediately profitable gold from South 'Manhattan's' controllers: "The Rand South African uranium was committed Africa's mines. Radioactive minerals may be the largest low-grade uranium to the Combined Development Agency, including uranium were tossed aside on field in the world." Analysis of the official procurement organisation of to the mines' slimes dams. It took war 400 000 samples of ore suggested the British and United States to turn the world's attention to what is that a potential annual production of Governments, for use in nuclear now the greatest source of energy for 7 500 to 10 000 metric tons of weapons programmes. But by 1959, peaceful development. uranium oxide (UaOs) could be the military needs of those countries Heading the joint British-American expected. had begun to decline and the contracts search in the mid-1940s for uranium On October 8, 1952, the then Prime concluded between the Agency and the for 'Manhattan', the code name for the Minister of South Africa, Dr D F Malan, Atomic Energy Board of South Africa project to produce the world's first opened the country's first uranium were renegotiated. atomic bomD, Dr G W Bain of the production plant, at West Rand The rate of deliveries was reduced United States and Dr C F Davidson of Consolidated Mine, 30km west of and the period of supply extended, but the United Kingdom turned their Johannesburg. Uranium plants were the industry was compelled to cut back. attention to South Africa. Dr Bain built at other gold mines and by 1955, By 1965 annual production was down recalled Cooper's research. Before 12 plants fed by 19 mines were to 2 500 metric tons and the number of leaving the United States, he tested a achieving a total annual production of producing mines had been reduced to sample of gold-bearing ore from the 3 000 metric tons of UsOs a year. eight. The needs of the infant nuclear Witwatersrand. Development continued and reached power industry were insufficient to The two men came to South Africa its peak in 1959 when 26 uranium- absorb the full output of the major and investigated the ores of several producing mines with 17 plants uranium-producing countries. gold mines. They soon established the supplied almost 6 000 metric tons of It was not until the 1970s, when the presence of significant amounts of UaOe. world oil crisis spotlighted uranium as a uranium. Dr Davidson reported to At that time, the entire output of vital alternative fuel source for electric
South Africa's mineral wealth: Uranium 1 power generation, that the uranium ; industry was able to recover. Universal '._ -; concern amongst the leading industrial r i nations of the world in regard to the t?r stability and sufficiency of future fuel : -\ sources and of fossil fuels in particular, i;;-f led to a spectacular increase in the \:••% expected world consumption of uranium ~~}i for the generation of nuclear power. XT. Forecasts of the growth of nuclear j? i.; power were so optimistic that even the t'fa then-known exploitable uranium i-X •'-. resources were seen to be inadequate. '--•_'}-. Attention was drawn to the need for Ifpi. further advances in nuclear technology -"; and for the development of breeder :' ' reactors with their promise of an " -' almost limitless source of energy. Hydraulic sluicing of a slimes dam with a monitor gun to The South African mining industry produce feed material for the recovery plant at the Bast •/ was not slow to respond to the signal Rand Gold and Uranium Company Limited that the time had come once again for % the expansion of its uranium production capability. ;. Between 1975 and 1982 production - facilities were significantly expanded. • The total treatment capacity of the ;. industry was increased by 390 per • - cent from 1 395 000 metric tons cf ore ; . per month to 5 273 000 metric tons. of the major problems in tailings million metric tons of East Rand slimes '.: During 1981, 7 235 metric tons of recovery operations lies in the very dams. The overall grade of the slimes '•'-_ U30s were produced. large quantities of pulverised material is 0,53 g/ton gold. 0.04 kg/ton : By early 1982, the industry had been which have to be handled, which, in uranium and 1,04 per cent sulphur. : completely restructured. There were some instances, is made even more The total expenditure on the project 17 producing companies, operating 18 difficult by the location of the dumps to full production was over R140- treatment plants. To the byproduct amidst urban developments. million. It is treating 1,5-million metric producers — mainly mines whose After many years of technical study, tons of slimes a month and producing principal activity and source of revenue three large schemes are now in 150 metric tons of UaOe a year. was gold mining — there had been operation. The Orange Free State Joint Reclamation of tailings from the added some whose operations Metallurgical Scheme is recovering Stilfontein and Buffelsfontein gold afforded greater importance to uranium gold, uranium and sulphur from slimes mines, at the rate of 270 000 metric extraction. One of these was the Beisa dams owned by Free State Geduld tons per month, is being undertaken by Mine, owned by St Helena Gold Mines Mine, President Steyn Mine, President Chemwes Limited. The reclaimed slime Limited, which is concerned primarily Brand Mine and Western Holdings. is transported over distances of up to with the production of uranium. Three Approximately 1 100 metric tons of 11km to a treatment plant for the others recover uranium from tailings LbOa are recovered annually — about recovery of uranium and pyrite. which dumps and, at the beginning of 1982, 15 per cent of South Africa's total is used for the production of sulphuric accounted for 27 per cent of all current output. acid. The uranium output at this plant during 1981 amounted to 668 metric uranium production. Another scheme is being handled by tons UsOs. South Africa's vast tailings deposits, the East Rand Gold and Uranium a legacy of past gold mining operations, Company Limited (Ergo), the target of More than 98 per cent of current are for the most part of extremely low which is, over 20 years, to remove the South African uranium production grade — 0,006 per cent uranium. One gold, uranium and sulphur in 378- comes either directly or indirectly from
2 South Africa's mineral wealth: Uranium EVANDER EAST RAND CENTAL RAND WESTRAND FAR WEST RAND 6 KLERKSDORP 7 ORANGE FREE STATE
The 'Golden Arc' made by the seven goldfields of South Africa. More man 98 per cent of South Africa's current uranium production comes either directly or indirectly from the mines of these fields
the gold and uranium mines of the output of ifeOs of the gold-uranium seven goldfields of the 'Golden Arc' of mining industry since 1952. That the Transvaal and Orange Free State. output has now reached 115 000 The balance is a byproduct of the metric tons — approximately one- second biggest open pit mining seventh of the total consumption of the operation in the world — the copper non-communist world over the same mine of the Palabora Mining Company period. Limited in the northeastern Transvaal. The Nuclear Fuels Corporation of South Africa (Nufcor), which does not have any counterpart in other major uranium-producing countries, plays an important role in the provision of services to all South African uranium producers, excepting only Palabora Mining Company, for the final processing and marketing of UaOs. Nufcor is welMcnown among uranium-consuming countries as the world's largest single supplier of LbOs and has an impeccable record of service to its customers. The corporation has handled the final processing and delivery of the entire
South Africa's mineral wealth: Uranium 3 The Western world's reasonably assured uranium 1 resources recoverable at <$130/kg U as at January 1,1981 Metric tons UaOs and percentage of total I m a Statistics of the uranium industry
SOUTH AFRICA possesses the second largest reasonably assured uranium resources in the Western world in the cost category $13O/kg U [$50/lb uranium oxide (LbOalJ and a re- evaluation and categorisation of the resources in the less than S8O/kg U ($30/lb LhOs) cost category has indicated resources adequate enough to ensure that the country would remain a major producer even at that level. Total: 2 705 000 metric tons UaOs
• The statistics on these pages are given in metric tons UiOa. The conversion factor from tons ifeOa to tons U is 0,848
SOUTH AFRICA'S URANIUM RESOURCES AS AT JANUARY 1,'1981
METRIC TONS tfeOsx '000
Rock type Reasonab y assured resources(RAR) Estimated additional resources (EAR) TOTAL RAR+EAR Recoverable Recoverable TOTAL Recoverable Recoverable TOTAL <$130/kg U at at RAR at at EAR <»OAgU {80-1130/ligU TOTAL 291,4 128.6 420,0 99.2 107,4 206,6 626,6 • In accordance with the classification recommended by the International Atomic Energy Agency, the above cost categories refer to the costs of production and not to the setting prices. Mining and metallurgical losses have been taken into account. South Africa's mineral wealth: Uranium m. w-PRODUCTIO ' N AND CAPACITY OF SOUTH AFRICA'S URANIUM PLANTS 1981 PRODUCTION 1980 PRODUCTION CAPACITY RANGE Metric Metric \i Metric Metric Tons ore Production START tons tons tons tons treated metric tons UP PROPERTY treated UsOa Hi treated UsOs per day U30e DATE ill x'000 produced in x'000 produced x'000 per annum 1 Vaal Reefs I*3J 8 501 1 694 3 9 043 1 758 24-31 1 200-2 400 1953, '56, '79 2 Western Deep Levels 1 2 331 212 2 1629 213 9-10 200-600 1970 « 3 185 479 1 3 078 435 9-10 200-600 1956 4 Buffslsfontein 1 3 135 632 1 3 101 604 8-9 600-1200 1957 5 West Rand Consolidated 0* 673 190 1 1 127 386 3-4 200-600 1952 6 Driefontein Consolidated 1 1309 242 1 1210 252 3-5 200-600 1956 7Randfontein 1 3 351 592 2 3 933 646 9-11 600-1200 1954. '78 8Blyvooruitzicht 1 1 933 315 1 1920 325 5-6 200-600 1953 9 Harmony 3 6 944 580 3 S 796 491 19-22 600-1200 1955, '80 10 East Rand Gold & Uranium 1 19211 302 1 18 289 295 50 100-300 1978 11 Joint Metallurgical Scheme 1 • 6 203' 1093 1 6 100* 977 15-20 600-1200 1977 12Chemwes 1 3 488 668 1 3 407 696 8-9 200-600 1979 13Palabora 1 n/a 234 1 >18 000 174 >50 n/a 1977 UBeåa These properties started operations in early 1982. Each has one plant 15 Western Areas and is capable cif treating 3 0 30 melric tons off TOTAL 16 60264 7 235 19 76 641 7 252 •Closed August 1981 Compnsos ASO 000 msfnc tons of conc&nb'stss from gold plants Compris&s A18 000 nwinc tons of conc&ntrotBS front gold plants TypM OF opocBUOfi 1,2,10 and 11: Anglo American Corporation of South Africa Umited 1. 2, 6, 8 and 9: Underground and reclaimed slimes The Joint Metallurgical Scheme consists of four companies: 3, 4 and 7: Underground Free State Gedutd Mines Ltd., President Brand Gold Mining Company Ltd 5: Underground (Closed August 1981) President Steyn Gold Mining Company Ltd. and Wester 10 and 12: Reclaimed slimes 3: Angtovaal Limited 11: Reclaimed slimes and some current residues from gold plants 4, 5, 12 and 14: General Mining Union Coporation Limited 13: Byproduct of open-pit copper mining 6: Gold Fields of South Africa Limited 14 and 15: Underground (Opened early 1982) 7 and 15: Johannesburg Consolidated Investment Company Limited 8 and 9: Rand Mines Limited 13: Palabora Mining Company Limited Uranium production Uranium production of I the Western world, 1980 •Uranium grade 6- (mines — excluding slimes) 5- -0,4 -0,3 111I OO CO to as 1, 5 1 1 2, 5 • 1 -0,2 en en en oo CM try 184 2 7 25 2 3 10 8 8 43 7 4 83 8 4 77 0 1 9 82 4 Metri c -0,1 ton s UiO a .„I I I I I I III I I I I I I I I I I I I I I I I I I 1 Squt h Wes t Afric a | Countr y | US A 1 Canad a 1 Sout h Afric a 1 Franc e 1 Australi a 1 Gabo n | Other s 1952 1960 1970 1980 I 'Based on information teteascd by the IAEA South African uranium production and grades Total: 51 879 metric tons UaOs South Africa's mineral wealth: Uranium 5 r "1 National policies SOUTH AFRICA'S national policies affecting the production and export of uranium are given expression in the Atomic Energy Act 1967, as amended. No person may prospect or mine for uranium without permission of the Minister of Mineral and Energy Affairs, but such permission may be withheld only if the Minister is satisfied that the security of the State could be endangered if the applicant was given permission to proceed. There are no restrictions on foreign participation in uranium prospecting and mining, and foreign-based operations are subject to the same legal requirements as domestic companies. In a practical sense, uranium Prospecting for uranium at Sutherland, Cape, part of the prospecting and mining is subject to Permo-Triassic Karoo uranium province (230 Ma) the mining laws and regulations generally applicable. The State does not actively undertake prospecting operations, but limits its activities to geological mapping, airborne surveys and regional hydrological, geochemical and geophysical investigations. Prospecting The Atomic Energy Act also provides that no person may dispose of uranium South Africa's commitment to ensure THE search for new deposits has or export it from South Africa, except that uranium is used for peaceful extended far beyond the area of the under the authority of the Minister. In purposes only, with the obvious greater Witwatersrand Basin. exercising this control, the Minister is exception of the Western nuclear Geologists have re-analysed granitic required to consult the Atomic Energy weapon states. No sale contract is deposits and younger sediments, Board of South Africa. In practice, the approved without knowledge of the previously regarded as uneconomic and Minister's functions are exercised by identity of the end-user and the specific exploration teams have been sent into the president of the Board, the purpose for which the uranium will be completely new areas. members of which represent various used. The Board insists on The combined deposits of uranium national interests, including the uranium undertakings from the recipient that the and gold found in South Africa allow for mining industry. uranium will be safeguarded under the economic extraction of uranium from All uranium sales contracts must be system approved by the International extremely low-grade ores and afford approved by the Board and exports of Atomic Energy Agency or an South African producers a long-term uranium in fulfillment of such contracts equivalent. The Board is compelled to stability not enjoyed by producers in are controlled by the issue of export ensure that uranium is not dissipated other countries. This allows them to permits. The regulatory policy of the by injudicious contracting by the private guarantee supply, which is why so Board is characterised by a recognition sector for the supply of uranium on many energy producers throughout the of the fact that the business of selling terms substantially less favourable than world look to South Africa for their uranium is the business of private those generally prevailing on the world requirements of uranium. enterprise and that the Board's concern market. This policy is Tully endorsed by Prospecting for gold and uranium in in the approval of uranium sales the uranium producers. the Witwatersrand Basin is usually by contracts should be directed only means of medium- to small-diameter towards issues of broad national diamond drill holes which can be any concern. The Board is conscious of depth from 100m to 4 000m. In other 6 South Africa's mineral wealth: Uranium r A laboratory worker using an electron probe micro-analyser in the research laboratories of the Johannesburg Consolidated Investment Company group. There is a continuous effort throughout the South African uranium industry to improve mining, recovery, extraction and processing techniques Research areas, extensive use is made of closely- THE South African mining industry has slimes dams incorporating the use of spaced rotary-percussion holes to been conscious of the need to strive for oxidation and bacteria; the development depths of 300m following-up airborne increased efficiency in the mining and and implementation at full plant scale and ground radiometric surveys, recovery of uranium from the very low- of the Bufflex and Purlex solvent geological mapping, geochemical grade ores of the Witwatersrand and extraction methods and subsequently sampling and radon emanometry. South Africa has become the world the countercurrent ion exchange (CIX) A large number of occurrences of leader in the exploitation of low-grade process; the production of high-purity uranium have been located in the region uranium ores. ammonium diuranate suitable for of the southern Karoo. Of particular Only one uranium deposit in South conversion to UF4; the development of interest was the discovery of Africa is of a higher grade than 0,05 equipment to control acid and oxidant uramferous coal in the strata of the per cent uranium, most are between additives in leaching and the provision Karoo Sequence in the northern 0,02 per cent and 0,04 per cent. of a set of 10 uranium reference matenals for analytical purposes, in Transvaal. Exploration has also taken Many new and improved methods of which project eight overseas place in Natal and the northwestern recovery have been investigated and laboratories also participated. Cape. the immense research effort involved has been undertaken by the Chamber of Mines and individual mining groups, the Atomic Energy Board and the Council for Mineral Technology (Mintek). Examples of the wide scope of this work are: Investigations into the uranium leaching process, including the in situ solubilisation of uranium present in South Africa's mineral wealth: Uranium fag Processing and marketing i- South Africa's uraiium NUFCOR, the Nudear Fuels The Nufcor tankers have two slurry and recent modifications to the Corporation of South Africa, is owned separate stainless steel compartments equipment have substantially increased by the South African gold and uranium of the Sphzer sphero-conical design. the total capacity of the lines beyond producers. The organisation operates a Each compartment has a capacity of the original 6 000 metric tons. central processing plant, markets about 13 metric tons of ADU as an Filter cake produced by passing the uranium concentrates throughout the aqueous slurry containing the equivalent ADU through a pair of filters is pressed non-communist world and co-ordinates of about 3,5 metric tons of uranium by a pair of rollers through 6mm the uranium industry's joint research oxide (U3Os). The slurry is pumped into diameter holes in a steel plate to form and development programme. storage tanks where it can be mixed spaghetti-like extrusions on a dryer belt. A fleet of road tankers is used to with ADU from other mines. During the drying process,, these transport uranium in the> form of The continuous and automatic part extrusions crack into 6mm pellets ammonium diuranate (ADU) from each of the plant process starts with filtration which, although subsequently abraded of Nufcor's member mines to the to remove most of the water from the and shrunk, determine the processing plant 50km west of slurry. This is followed by extrusion, characteristic granular texture of Johannesburg. At the mines the drying and calcining. The sequence is concentrates from the Nufcor plant. The uranium is concentrated from the followed in three similar production ADU is dried in a heated air stream at original ore some 1 000 times, making lines which can be operated 130°C, after which chips of ADU pass it economically and technically simultaneously. Each consists of a pair into one of three calcining furnaces. All advantageous to transport the material of rotary drum filters, an extruder, a are horizontal cylinders of stainless to a single central plant for treatment belt dryer and a rotary calcining kiln steel supported and turned on and further concentration. The Nufcor and was originally designed to have an electrically driven rollers. They are processing plant is centrally situated in annual capacity of almost 2 000 metric heated externally by Calrod elements relation to the mines of the 'Golden tons of ifeOa. However, changed and the calcining temperature, Arc'. physical characteristics of the ADU measured in the bed of the material. 8 Soutfl Africa's mineral wealth: Uranium reaches just under 500%. The ADU operation, the Corporation has never chips are transformed successively failed to meet commitments in full from yellow ADU at the inlet of the accordance with its supply contracts. furnace, through orange UO3, to grey- The co-ordination of the industry's green concentrates consisting of a research and development programme mixture of UO2 and UO3 in the is a* combination of projects, some approximate proportions U3O8. jointly with the Atomic Energy Board of The U3O8, commonly referred to South Africa or the Council for Mineral commercially as 'yellow-cake', is then Technology and others which are sampled by lot size and packed into undertaken solely by the industry. tarred 210 litre 16-gauge steel drums. The projects are essentially practical Each contains about 350kg of investigations directed specifically concentrates. Upon despatch, the towards applications in the fields of drums are assembled in standard 6m process improvement or cost ribbed-steel shipping containers which reduction. This collaborative research are sent by road and rail to the port of and development effort has been Durban for shipment. extremely fruitful in ensuring that the The marketing of the LbOa produced South African uranium industry has at tiie Nufcor plant is undertaken by been able not only to keep abreast of Nufcor. South African itaOs is sold to technological developments but has nuclear reactor owners throughout the also, in a number of instances, been the non-communist world. Nufcor has an first to introduce innovations in outstanding reputation for reliability. uranium treatment processes. During more than 25 years of South Africa's mineral wealth: Uranium 9 I I REPUBLIC OF SOUTH I J AFRICA IH SOUTH WEST AFRICA 1 BOPHUTHATSWANA 2 TRANSKEI 3 LESOTHO 4 SWAZILAND 5 CISKEI The geology of South Africa's APPROXIMATE LOCATIONS uranium occurrences OF URANIUM PROVINCES IN SOUTHERN AFRICA WITHIN South Africa, uranium basin edge to advance progressively occurrences are found in: Precambrian farther towards the depositional axis. Surficial formations, quartz pebble conglomerates. The final depository was smaller than • recent to tertiary Precambrian alkaline complexes, the original, so that, overall, the Sandstone and coal, Cambrian to Precambrian granite sediments were laid down in a • permo-triassic gneiss, Permotriassic sandstone and shrinking basin. coal and Recent to Tertiary Surficial Conditions were generally Granite gneiss, alaskite formations. About 11 per cent of South and pegmatite, cam- transgressive in the Lower brian to precambrian Africa's uranium resources occur Witwatersrand Division and generally outside the Witwatersrand Basin, the regressive in the Upper Division. Alkaline complexes, most important being the uraniferous Second order transgressions and precambrian coal deposits of the northern Transvaal, regressions were superimposed on followed by the sandstone occurrences Quartz-pebble conglo- these primary trends. Between the in the southern Karoo, the carbonatite merate—precambrian base of the Lower Division and the base at Phalaborwa and the surficial (Producing mines) of the Upper Division, the edge of the deposits of the northern Cape. basin moved southeastward by 60km and the depositional axis by about Quartz pebble 10km. A high-energy transfer system from conglomerates the source to the depository took the The average average content of form of a relatively short, linear fluvial uranium in the ores of the array. From the areal geometry of the Witwatersrand — usually in the form different stratigraphic horizons, the of uraninite — varies between 100 patterns of facies variations, the trends I grams and 2 000 grams of uranium in the changes of grain skes of oxide (UaOs) per metric ton. sediments, the directions and patterns According to D A Pretorius in a of palaeoflow, the nature of the paper in the Geological Society of South environmental indicators and the Africa, Special Publication No 6 distribution of heavy minerals; it would uranium field, which measured 40km in (1977), the Witwatersrand depository appear that a gold and uranium field is length down the central section, 50km (2 800 Ma — 2 500 Ma) is an a fluvial fan or fan delta formed where in width in the midfan section and intermontane, intracratonic, yoked the river system debouched into the 90km in width in the fanbase section. basin with a fault-bounded lake via a canyon cut through the high The western margin of this fan was northwestern edge and a gently ground to the northwest of the 45km long and the eastern flank 60km. downwarping more passive peripheral faults. Six fluvial fans have so far been southeastern boundary. The enclosed In this type of environment, there discovered — those constituting the basin was at least 350km long in an were far greater amounts of water than Orange Free State, Klerksdorp, West east-northeasterly direction and 200km on a typical alluvial fan and the energy Wits, West Rand, East Rand and wide in a north-northwesterly direction. level was higher than that on an Evander goldfields. The structural environment oceanic delta. After emerging from the The original Central Rand, on which resembled that of the Basin and Range canyons, the rivers flowed short the Main Reef conglomerates were Province, but had a far wetter climate. distances over a piedmont plain and discovered, would seem to be a The Basin was a shallow water lake or then dispersed through a braided- geographical entity only, since inland sea. The depository became stream pattern into the basin. The geologically, it represents the structurally more unstable with time, a fluvial fans were restricted to the coalescence of the eastern part of the pattern of interference folding produced northwestern margin of the depository West Rand fan and the western part of structural depressions and culminations and some of them coalesced in their the East Rand fan. The gold and on the rim and within it. The various more distal parts, leading to the uranium mineralization has been impression of extensive sheets of gold and uranium fields developed in recognised to occur in five forms: In the uniform gravel. downwarps between basement domes. matrices of the conglomerates, in The northwestern side was episodically The largest of the fans was that heavily pyritic sands filling erosion but continuously rising, causing the constituting the East Rand gold and channels during successive cycles of 10 South Africa's mineral wealth: Uranium 4 SV; iBis! • BLOEMFONTEIN* fes NORTH WESTERN CAPE ii SURFICIAL PROVINCE sedimentation, on quartzites along a sedimentation. In the conceptual model channels, thicker and coarser clastic plane of unconformity between of a typical Witwatersrand goldfield sediments, and higher concentrations of successive cycles of sedimentation, on illustrated, the apex of the fluvial fan detrital gold and uranium. shales along planes of unconformity was located along the tectonically The material laid down between the and in carbon seams on, or adjacent unstable basin edge where repeated lobes took the form of sands, silts and to, planes of unconformity. uplift of the source area side took place muds, similar to that which The three last mentioned types of along longitudinal faults. accumulated on the fan margins and reef were formed in the terminal stages The fanheads of earlier fans were base. Conditions under these lower- of one cycle of sedimentation and the uplifted and reworked into later fans, energy regimes at times provided the two first mentioned in the initial stages while the midfan and fanbase sections optimum environment for the growth of of a succeeding cycle. The gold and were structurally depressed and algae or lichens, which took the form of uranium were transported as detrhal thereby preserved. The downward thin algal mats. The gold was of too particles and in solution as chloride and displacement of the midfan and fanbase fine a grain to settle in the fanhead cyanide complexes. Concentration took caused transgression of the lake f acies. The highest concentrations took place physically through gravity settling waters, producing winnowing of the place in the midfan lobes, with the and subsequent winnowing by wave fines and lag concentrations of the peak of uranium mineralisation a little and current action: and biochemically heavier minerals. Longshore currents farther down the slope. The energy through interaction between the gold moved the finer sediments farther level dropped too low to permit the and uranium and the algal or lichen away from the entry points to form transportation of detrital gold to the colonies that preferentially developed asymmetrical fans owing to the fanbase section, but the gold and about the mouth of the major rivers; in clockwise movement of the water in the uranium in solution interacted with the the quieter-water conditions on the depository. The typical fluvial fan had beiogenic material in the low-energy margins and fanbases of the fluvial two main lobes in which were located a environments. A fluvial fan was built up fans and at the end of certain cycles of larger number of braided-stream in a series of pulses of sedimentation. South Africa's mineral wealth: Uranium 11 i k II l?3 I which started with pragradation during røgiwittion, went through aggradation during transgression and ended with degradation during stillstand. These three stages constituted a singfe cycle of sedimentation. A new cycle was initiated through tectonic adjustment along the longitudinal faults. Theadjustnvitt produced a steepening A conceptual model of a Witwatersrand goldfield as a fluvial fan developed at the mouth of a major river flowing from a source area in the northwest and debouching of the pabeoslopa and the increased into a shallow-water, intermontane, intractronic lake over a peripheral hinge-line competency of the streams brought constituted by faults parallel to the depositional axis, as devised by Pretorius in greater amounts of coarsø debris onto 1974. (Graphic with acknowledgement to 'Minerals Science Engineering'). the fan. The higher energy level caused progradatkm and a consequent regressive relationship with the earlier sediments. The first pulse laid down an openwork gravel and the next pulse the sand matrix. Heavy minerals were brought in with the sand phase and as the energy level dropped transgression took place, with the deposition of finer grained material until a state of equilibrium was reached'and deposition came to a standstill. End-of-cyde winnowing by the waters of the streams and the lake produced a greater concentration of residual heavy minerals on the erosion in the carbonatHe at Loolekop, which tonnages of low-grade mineralisation in surface. Incipient tectonic activity forms the central core of the a number of localities in the caused tilting of the surface, producing Phalaborwa Igneous Complex (2 000 northwestern Cape. the unconformable relationships Ma) in the northern Transvaal. Tests between successive cycles. showed that the deposit held little Karoo sandstone On the surface, degradation was promise as a primary source of and coal enchanced, winnowing intensified, and radioactive minerals, but justified a tag concentration brought to an large scale copper mine. The Permo-Triassic (230 Ma) Karoo optimum. Continued tectonic Today at Phalaborwa, copper and uranium province which stretches in a adjustment culminated in the other associated minerals are being broad arc from Aberdeen in the prograding sedimentation of the next mined at the world's second biggest southwest to Sutherland in the west cycle. The turbulent gravels broke up open-pit mining operation and uranium and Qwa-Qwa in the northeast the deposmonal floor and incorporated is recovered as a byproduct. represents a mineral province of the thin streaks of lag gold and uranium significant potential. Most of the on the unconformity. These minerals Granite gneiss uraniferous sandstone deposits have could have been introduced into the been found in the various formations of gravels by pickup from the footwall Uranium occurs in low concentrations the Beaufort Group, but some have sediments and downward infiltration either in disseminated form or been located as high up in the during the sand pulse that succeeded associated with fracture zones in the sequence as the Clarens Formation of the laying down of the pebbles. granitic and metamorphic rocks of the the Stormberg Group. The Namaqua/Natal belt (1 000 Ma) in the mineralisation occurs mainly as tabular, Alkaline complexes northwestern Cape, in southern Natal irregular lenses within thick <5m — and within the Bushveld Igneous 6m) channel sandstones and is In 1952 uranothorianite was discovered Complex (1 950 Ma). There are large controlled by the presence of 12 South Africa's mineral wealth: Uranium carbonaceous material, permeability and discontinuous erosion surfaces within the sandstones. Grades vary from trace amounts to more than two per cent ibOs with an average of about 1kg ihOs/ton over 1m width. In some areas results have been sufficiently encouraging to justify in-depth feasibility studies. In 1981, uraniferous coal was investigated in the Springbok Flats of the northern Transvaal. The uranium is concentrated near the flanks of the subsidiary basins over a relatively large area and although the average grade is low, the area is regarded as a potentially viable uranium district. The Witwatersrand Basin as revealed by the • Surficial deposits removal of the overlying more recent rock formations (after Borchers, 1960}. In southern Africa, Tertiary to Recent (0,1 Ma — 10 Ma) surficial uranium occurrences have received a much attention following their discovery in Australia and South West Africa during the early Seventies. The exploitation effort moved to South Africa during the mid-1970s, employing largely airborne radiometric surveys. finer matrix material. In a number of levels of uranium and are unlikely to - In South Africa, the occurrences are localities in the northern Cape uranium ever constitute a viable resource. There located within the palaeodrainages of occurs in association with have been indications, however, that the major river systems of the diatomaceous peaty earth, the marine phosphate deposits of the northwestern Cape. All are tributaries representing paleo marsh or bog Agulhas Bank contain somewhat higher of the Orange River and flow in a conditions which developed as a result levels of uranium. northerly direction away from a of ponding within the channels. Extensive deposits of black sands transcontinental warp axis. The whole The mineralisation is usually occur along the Natal coast and are area lies within the 200mm isoheyt. associated with organic-rich bands. mined near Richards Bay, largely for which appears to be one of the main Uraninite is the main uranium mineral, the rare earth content. Substantial limiting factors regarding the but some uranium may occur as an reserves of monazite, which contain distribution of the occurrences. The organo-complex. Most of the deposits appreciable amounts of uranium and uranium is derived from the undertving investigated to date appear to be of too thorium, are also present. granitic and metamorphic rocks as also limited an extent or too low a grade to the Dwyka finite of Permian age. justify exploitation at present. The uraniferous surficial deposits occur either in 'calcrete' deposits Phosphates formed under oxidising conditions or in association with a peaty diatomaceous Although South Africa's large resources earth, deposited under reducing of igneous as well as evaporitic conditions. In the calcrete type the phosphates contain some uranium, uranium mineralisation occurs largely in investigations have shown that the the form of carnotite as grain coatings igneous phosphates from the around pebbles or associated with the Phalaborwa Complex contain very low South Africa's mineral wealth: Uranium 13 r Processes used in the extraction of South Africa's uranium PROCESSES for the extraction of has prevented the full exploitation of process the measurement of natural uranium from conglomerate ores in conglomerate texture to obtain a gamma radiation from the contained particular have undergone a number of reduction in process costs. On the uranium mineralisation together with an developments since testwork other hand the tendency for uranium assessment of ore volume by means of commenced in the Forties. Process minerals to comminute somewhat more a light extinction technique is used as evolution is far from complete and the rapidly than other conglomerate criteria in deciding whether to accept search for more economic extraction components can be used to split the or reject a particle of ore. techniques continues both in the feed to a mill into high- and low-grade A typical radiometric sorter is the research laboratories of the mining streams. Western Deep Levels, Model 17 produced by Ore Sorters groups and at the Council for Mineral Driefontein Consolidated and (Africa) (Pry) Limited, in which a feed Technology (Mintek). A number of Blyvoorutoicht mines all screen their presentation system is used to channel projects are financed by the Nuclear feed at size ranges of between 3mm incoming material into single file Fuels Corporation of South Africa and 19mm to concentrate 60 per cent streams of spaced rocks. The racks (Nufcor). of the uranium in an undersize fraction then pass through a radiation comprising some 30 per cent of the measuring system and a light box Pre-concontration feed weight. arrangement before leaving the belt at Gravity separation, which has been some 5 m/s. An electronic processor The leaching of uranium from its ore successfully employed for the removal tracks the position of each rock in each and the subsequent separation of of coarse gold, has enjoyed less of the single file streams, assesses the solids and liquids, required by most success in the concentration of counts received and the light box processes before the uranium can be Witwatersrand uranium minerals. A indications of surface area, compares recovered, is a costly process. particularly interesting development, the computed LbOe content of the rock Solid/liquid separation alone can however, has been the evolution of a against a pre-set cut off level and account for between 15 per cent and gravity leach process to recover decides whether to initiate a blast to 35 per cent of the capital costs and uranium from the carbonatite contained separate the ore particle from the waste between 10 per cent and 20 per cent of in the Phalaborwa Igneous Complex, stream trajectory. the operating costs. where a combination of Reichert Cones Existing sorters can only handle It is, therefore, of some economic and shaking tables is employed to broken rock within a certain size range, advantage to upgrade the uranium upgrade a flotation tailings with a so only a portion of the feed to the mill content of the feed to the leach plant by 0,0035 per cent uranium oxide (LbOs) can be sorted in this fashion. Nine rejecting as much low-grade ore at as content to a final table concentrate Model 17s are expected to come into containing 3,0 per cent ifeOs. early a stage as possible. In fact, some operation at Western Deep Levels of the earliest research on the The development of wet high- during early 1982, of which five will be extraction of uranium from intensity magnetic separators has two-channel machines sorting Wrtwatersrand conglomerate was reached a point where the processing —150+65mm and a further four will be concerned with the problem of pre- of finely ground para-magnetic particles five-channel machines sorting concentration and it was found that in a pulp stream has become possible. -65+25mm material. Material sent to some 70 per cent to 80 per cent of the One major shortcoming, namely a the waste dump should assay less than uranium could be concentrated into 20 tendency for the ferromagnetic matrix 20ppm USOB and pilot experiments per cent of the feed weight by flotation. to become blocked with wood chips using a Model 17 on Vaal Reef ore to This however was considered and ferromagnetic particles, has been sort -115+65mm indicate that a inadequate and the acid leaching of the overcome by the development, at tailings of less than 15ppm is entire tailings from the cyanidation Mintek, of a system to continuously attainable. process was accordingly adopted. dean the steel balls that usually At the Welkom Gold Mine crushed The occurrence of both gold and comprise the separatory matrix. A full ore is screened at 6mm to produce scale WHIMS machine capable of uranium in the matrix of the pebble high- and low-grade products. The treating 30 metric tons per hour of conglomerate suggests that the -75O+5Omm fractions of the low- reclaimed tailings material has been removal of the barren pebbles would grade material are sorted using a four- installed at the Stitfontein gold mine. provide a degree of enrichment at a channel Model 17 to remove comparatively coarse size. However, One of the more promising uraniferous ore for return to the high- the tendency for breakage to occur developments in pre-concentration is grade stream (which alone is treated for across the pebbles during comminution the radiometric ore sorter. In »his the extraction of both gold and 14 South Africa's mineral wealth: Uranium The Bacterial Film Oxidation (BACFOX) plant at Buffelsfontein mine, the first of its kind, which oxidises ferrous leach liquor for recycling to the uranium leach uranium). A similar application to the vary widely. Thus moderate additions the cost of ferric ion provision, elevated —10O+63mm fraction of a low-grade of sulphuric acid and manganese temperature etc. stream at Free State Saaiplaas is under dioxide to ores from the Kimberley Reef An interesting technique developed consideration, while four RM161 six- on the East Rand and the Monarch and for the production of ferric ions uses a channel sorters are in use at the Bird Reefs on the West Rand results in bacterial oxidation of the ferrous ion Buffelsfontein Gold mine sorting uranium dissolutions of 90 per cent. present in the internal recycle stream -50+25mm material to provide a However, similar conditions, when but perhaps the most promising reject fraction containing less than applied to ores from the Vaal and method of dealing with refractory 25ppm of UaOs. Dominion Reefs, provide uranium uranium ores involves the use of extractions of only some 50 per cent to pressure leaching. Two pressure 60 per cent and an improvement in Leaching techniques have been subjected to recovery requires, at the least, elevated examination for use on Witwatersrand leach temperatures. The attachment of an acid leach ores. The first of these is a horizontal, process to existing cyanidation circuits A possible cause of such refractory mechanically agitated autoclave was the major plant modification in the behaviour could be the presence of operating at a temperaure of 170°C early days of uranium recovery from such minerals as brannerite, euxenite, and an oxygen partial pressure of 700 Witwatersrand ores. The realisation thorite and monazite as well as more kPa. Materials problems encountered that, by leaching the uranium first, resin readily teachable primary uranium. A and progressively overcome have poisoning by cobatti-cyanides could be more agressive leaching environment included impeller blades (covered with avoided and gold recovery enhanced, for refractory uranium minerals can be mechanically bonded, fused alumina led to the use of the so-called reverse- provided by the use of ferric sulphate in tiles), pressure letdown (using leach process. The ease with which conjection with sulphuric acid. Careful "Refrax" chokes) and mechanical uranium can be extracted from attention has to be paid to the cost of seals for the multi-staged centrifugal Witwatersrand ores has been found to the extra uranium recovered in terms of pumps. The second device. South Africa's mineral wealth: Uranium 15 2 South Africa's mineral wealth: Uranium 1 at present being tested on a pilot scale, Witwatersrand conglomerate resins now used in continuous is a pipe reactor. An installation processing could be applied to many of contractors (CIX). The tolerance of designed to treat some 40 000 metric the Karoo sandstone deposits. some of these devices to a limited tons per month has been installed at In the case of the uranium present in amount of solids in solution obviated the Randfbntein Estates Gold Mining the uranothorianite of the Phalaborwa the need for careful clarification prior to Company. By pressurizing the pulp to Complex, a hot nitric acid leach is recovery- As resins can handle some 6 000 kPa using a sophisticated employed, whereby bcth the thorium solutions of lower uranium tenor than diaphragm pump, heating the pulp to and the uranium (concentrated some wruld, economically, be the case with 160°C and injecting oxygen, reaction 40- to 50-fold by gravity concentration solvents, the continuous ion exchanger kinetics are enhanced to a point where processes) are taken into solution for can receive pregnant solution from a residence times are reduced from some subsequent recovery by solvent countercurrent decantation circuit and 20 hours to 2,5 hours. extraction. pass an enriched pregnant solution, Unlike Wrtwatersrand conglomerate containing uranium stripped from the ore, the sandstone uranium deposits of Recovery resin, to a solvent extraction circuit the Karoo contain quantities of acid with a very pure OK liquor as the final consuming minerals. Such deposits are The first uranium recovery plants on the product. usually processed using alkaline Witwatersrand used conventional drum The picture has been further lixn/iarrts, especially carbonate filtration for the separation of solids and complicated by the introduction of the solutions. liquids followed by fixed-bed ion belt filter, a device offering an In view of the greater cost of such exchange. However, the previously acceptably low loss of uranium trapped lixhriant which must be imported .into mentioned tendency of cooafti- in the filter cake in a single stage of South Africa, a controlled acid teach cyanides present in solution to poison filtration as opposed to either the was developed whereby a constant the resin led to the adoption of solvent multiple stages often demanded with addition of sulphuric acid was used to extraction in the form of the so-called drum filters, or the high wash ratios maintain a pulp pH value in the vicinity "Purlex" process. The subsequent requiring to be accommodated when of two. By this means consumption of development of the "reverse-leach" using countercurrent decantation. acid is kept within economic limits and process for uranium dissolution . Recently the economics of several the established technology of permitted a return to ion exchange liquid/solid separation and uranium ACCELERATOR AND STABILIZER UNIT Operating principle of RTX Model 17 ore sorter ORE WASTE 16 South Africa's mineral wraith: Uranium "1 f recovery circuits were examined; these were: (1) Two stages of drum filtration with clarification and solvent extraction (SX). (2) Countercurrent decantation (CCD) with clarification and solvent extraction. - (3) CCD with continuous ion exchange (CIX) and solvent extraction. (4) Belt filtration with clarification and SX. (5) Belt filtration with CIX and SX. Calculations suggested that the fifth would yield the highest net present value, assuming that belt filtration maintenance did not amount to more than 4 per cent of the capital cost. The third circuit was adopted for expansion of the uranium plant at Blyvooruitzicht with the unclarified thickener overflow being treated ir. South Africa's mineral wealth: Uranium 17 i r The Valindaba site of the Uranium Enrichment Corporation of South Africa limited, where South Africa's enrichment acovhes are undertaken Closing the fuel cycle GIVEN the large uranium resources of Although information concerning the South Africa and the country's exact nature of the separation element technological ability to extract and and its technology remain classified, it refine them, it was logical that has been revealed that the UCOR consideration should be given to the process is of an aerodynamic type. By ultimate beneficiation of uranium — virtue of careful experimental and enrichment — and to the utilisation of advanced theoretical work it has been uranium for power production. possible to develop what in effect is a Investigations along both lines werr high performance stationary-walled commenced in the early Sixties and centrifuge, using a mixture of uranium pursued with considerable success. hexafluoride and hydrogen as process Financial and manpower limitations fluid. reinforced by the almost worldwide In this process however, the "cut", preference for power reactors which which is the ratio of product to feed used slightly enriched fuel led South stream, is not 0,5 as in the diffusion Africa to abandon development of a process and simple cascading is not promising natural-uranium reactor possible without substantial losses. concept and to concentrate on a unique South Africa's solution to this problem process for enriching uranium which . was the development of a new culminated in 1975 with the release by technique, the helikon cascade, based the Uranium Enrichment Corporation of on the principle that an axial-flow South Africa Ltd (UCOR) of details of compressor can simultaneously the process and the pilot plant then transmit several gas streams of under construction. different isotopic composition without 8 South Africa's mineral wealth: Uranium ~l r PeBndaba, South Africa's National Nudear Research Centre and the headquarters of the Atomic Energy Board of South Africa there being significant mixing between the field of conversion and a large-scale for South Africa's own domestic them. The UCOR process must conversion plant was planned and is requirements by extending the pilot therefore be regarded as a combination now under construction on the UCOR plant. The expanded complex will start of the separation element and this site adjacent to the enrichment plant. producing enriched uranium from the technique. At UCOR it is possible to This plant will utilise non-nuclear grade mid-Eighties. achieve the desired enrichment with a ammonium diuranate obtained from the South Africa's domestic requirements relatively small number of large mines as feedstock (instead of the usual are represented by the Koeberg nuclear separation units by fully utilising the nuclear grade uranyl nitrate) and will power station near Cape Town. The high separation factor available (1,025 manufacture its own hydrofluoric acid first unit of Koeberg is expected to go - 1,030 depending on economic (HF) from fluorspar and its own into operation in early 1983 and the considerations). By 1977 the pilot fluorine. HF production will exceed the second should be commissioned a year plant ai Valindaba was fully conversion plant's requirements and later. UCOR's production will be aimed commissioned and performing well and the excess will be sold. at providing enriched uranium for the possibility of building a large scale The world picture at uranium Koeberg's future reloads from the production plant based on the helikon enrichment demand and production is second half of the Eighties and, by technique was being investigated. changing and an analysis of the future virtue of the flexibility of the UCOR The realisation that the uranium situation suggests heavy oversupply process, at meeting the requirements hexafluoride (UFs) plant would be during the Eighties, diminishing of any additional nuclear power stations needed to supply the feedstock for an somewhat during the following decade which the Electricity Supply enrichment plant resulted in the but nevertheless predicting adequate Commission of South Africa may decide construction by the Atomic Energy enrichment capacity to satisfy demand to construct. The domestic fabrication Board of a pilot plant for the conversion up to the end of the century. of fuel elements for power reactors is of uranium into UFe. Valuable Accordingly, UCOJVs production plans not a matter of immediate importance experience was accordingly gained in have been modified to cater primarily since initially it will be performed South Africa's mineral wealth: Uranium 19 through the reactor vendors. In the The remaining operation which South Africa the step is one which longer term, however, consideration is finally completes the full fuel cycle is need only be considered in the very to be given to the advisability from all that of reprocessing spent fuel long term ånd may never enjoy points of view — economic, political elements to extract for reuse the attention especially if the concept of and strategic — of establishing a residual unburned uranium and joint safeguarded regional reprocessing fabrication facility in South Africa. Of Plutonium. This is the step which is centres is realised. In the meantime the the country's ability to do so there is most beset with political problems establishment of a national waste little question and a pointer in this Quite apart from its intrinsic repository is being actively pursued and direction was the announcement in technological complexities. From the areas suitable from the geological, 1981 that the research reactor purely economic point of view atone, hydrological and sociological points of SAFARI-1 is now being fuelled with however, the creation of a reprocessing view are the subject of detailed elements fabricated by the Atomic capability only becomes of significance investigation. Energy Board of South Africa from once a country has a substantial enriched uranium supplied by UCOR. installed nuclear power capacity. For Koeberg, South Africa's Uret nuclear power station, under construction. The first 922 MW unit should be commissioned in early 1983 20 South Africa's mineral nealth: Uranium South Africa's mineral wealth: Uranium Covar and graphics by Barnard Sargant Photographs: Paga 1, ThtSttr: Page 2. Anglo American Corporation of South Africa Limited P»o»«8»rrf7,Johar»)8»t»irQCor»oBdit»dlmBitrrwmCompanvLirnitBd Paga 8, Chamber of Mnaa of South Africa: Page 16, Nuchar Active Paga 18, Uranium Enrichment Corporation of South Africa United: Paga 19, Atomic Enargy Board of South Africa Paga 20. ElectricitySupply Cornmisaian of South Africa Typaaeta»idaub-a«itarionthaAte»aiactrnnfcaniDVigay8t»matSoumAf^^ Colour aaparatioita by ALM Proeasa Engraving (Pty) Limitad, Johannaaburg Printad by Noriharn Caps Printers Limitad. comar Baan and Wars straata, Kanbarlay, northern Cape MB OF SOUTH WDM HD WOES MR M2 — May 1M2