Mantra completed a Scoping Study on the Nyota Prospect in June 2009 utilising a counter current decantation (CCD) process route.The Scoping Study revealed that the process route could be further enhanced by the use of RIP.

ANSTO completed batch and pilot scale testwork and the results were used in an engineering and metallurgical trade off study between RIP and CCD. The testwork and trade off study has clearly demonstrated that the RIP process is the preferred process route for the MRP. The advantages of this process route are summarised as follows:

Simplification of operation with the removal of the CCD circuit; A significant reduction in size or elimination of the solvent extraction (SX) plant with the potential to go to direct precipitation; Reduction in overall reagent use; Smaller plant footprint; and Greater flexibility in the processing of mineralisation in varying host rock types.

The RIP process is currently being used by Paladin Energy Limited at their Kayelekera Project in Malawi and has been used in uranium recovery in the United States and former Soviet Union for many years. The company is well advanced in its Pre Feasibility Study (PFS) on Nyota and will be utilising

the RIP flowsheet in the capital and operating cost estimates for the Project.

Introduction

Following the completion of a 40,000m drilling program in late 2008, an Inferred MRE of 35.9 million pounds U3O8 (39.9 million tonnes at 409 ppm) was estimated at Nyota in early 2009. The current MRE was used as a base case scenario for the Scoping Study completed in June 2009 which supports the technical and economic viability of the MRP and its potential to generate strong cash margins.

Following the positive outcomes of the Scoping Study for the MRP, Mantra elected to complete a PFS on the Project. One key aspect of this PFS was to undertake metallurgical testwork at ANSTO in Sydney to evaluate the technical viability of incorporating a RIP circuit into the proposed process plant design.

The RIP Process

Around 1.2 tonnes of core material from Nyota representing the first five years of scheduled mining production, was utilised by ANSTO for the testwork. The work covered the beneficiation of the material through the scrubber, cyclones and thickener. This generated both a reject component (scats) and an upgraded feed slurry, which contained approximately 90% of the uranium. Sulphuric acid is then added to the slurry to dissolve (leach) the uranium. Once the uranium is dissolved the slurry is pumped to the RIP section of the process plant.

The RIP process works to the same principle as a conventional gold carbon in pulp (CIP) process. In the RIP process, resin beads are used instead of carbon to adsorb the uranium. This adsorption of the dissolved uranium takes place in a carousel arrangement of tanks which contain the resin and slurry. Once the resin is ‘loaded’ with the required concentration of uranium, the slurry and resin are screened to separate the loaded resin from the now barren slurry. This barren slurry is pumped to a thickener for water recovery and then to the tailings storage facility.

The screened loaded resin is transferred to an elution column where the uranium is stripped from the resin, to generate a uranium rich solution called an eluate. The stripped resin is returned to the RIP process. The eluate then passes through a small SX plant where trace impurities are removed prior to the precipitation of the final uranium product.

Testwork Completed by ANSTO

The testwork effectively assessed: the beneficiation of the material through the scrubber; the classification of the scrubbed ore using screens and a thickener; the rate and dissolution of the uranium (leaching); an assessment of the need for and amount of reagents required in the leach; the adsorption of uranium on to the resin; the elution of the uranium from the resin; and the opportunity to go to direct precipitation based on the purity of the solution from the elution stage, removing the need for an SX plant in the process flow sheet.

Testwork Outcomes

The key outcomes from the testwork are: The mineralised material beneficiated well, consistent with previous testwork and expectation; Leach recoveries are improved after contacting the leached slurry with resin resulting in higher overall uranium extraction than can be expected with a CCD/SX process; High leach rates were achieved within six hours; A reduction of leach reagents and the opportunity to potentially eliminate the need for iron and oxidant; Effective adsorption of uranium onto the resin in excess of 99%; Resin uranium loadings in excess of 30g/l can be achieved; The uranium is effectively eluted from loaded resin resulting in a high purity eluate; and The testwork confirmed that the leach process will operate at ambient temperature.

The results of the testwork programme have shown that the MRP mineralisation is amenable to the recovery of the uranium using an acid leach in combination with RIP.

The bench scale batch leach tests completed in this phase of testwork indicate that enhanced leaching of the uranium is taking place due to the RIP. This may lead to a reduction or possibly the elimination of the addition of iron and oxidant reagent addition to the leach process. Further testwork will be directed towards minimising or eliminating the requirement for these reagents.

The results indicated that there was a 99.6% adsorption rate of uranium onto the resin, with no significant competing gangue minerals adsorbed, highlighting the low impurity levels of the mineralisation.

Bench scale elution tests aimed at stripping the uranium from loaded resin were performed. The results showed that the uranium is easily eluted to form a high purity eluate that may be suitable for direct precipitation of uranium without the need for solvent extraction. Further work will be directed towards the direct precipitation of uranium from eluate. This work will be completed in the Bankable Feasibility Study and if it is successful will remove the need for an SX plant in the process flow sheet.

Acid consumption in the process is low. 20kg/t of acid is consumed in the leach and the 6 kg/t is consumed in the elution part of the process for a total 26kg/t of leach feed. This equates to 13kg/t of run of mine material, as the beneficiation halves the volume.