Mantra Resources has begun a pre-feasibility study (PFS) on heap leaching lower grade mined ore at the company’s Mkuju River Project in Tanzania for the project’s second phase of growth.

The phase 1 of the project, which is currently the subject of the company’s definitive feasibility study (DFS), is targeting approximately 3.7 million pounds of uranium a year using the Resin-in-Pulp (RIP) metallurgical process.

It is envisaged that phase 2, the heap leaching of lower grade mined ore, would begin after the RIP circuit has reached steady state operations and provide the project with an incremental increase in production over and above the targeted annual production rate of phase 1.

The commencement of the Heap Leach PFS follows positive results from initial heap leach testwork campaigns conducted at the ANSTO and SGS facilities in Australia.

The company said that the initial testwork clearly demonstrated that the low grade ore is particularly amenable to heap leaching.

The results of column testwork, which simulates a heap leaching process, were very encouraging, indicating a uranium recovery rate of approximating 80% in eight days with a low acid consumption of approximately 8kg per tonne.

The company believes there is the opportunity for an incremental increase in production through the recovery of additional uranium from the lower grade (less than the current resource cut-off grade of 200 ppm U3O8) material, which is currently being mined and treated as waste in the pit optimization process for Phase 1.

The Heap Leach PFS is due to be completed during the first quarter of 2011 and will include further resource modeling and detailed leaching testwork to allow grade/recovery relationships to be investigated, the minimum cut-off grade for economic treatment of the Nyota orebody to be determined and additional data for engineering, design and costing to be generated.

Upon successful completion of the Heap Leach PFS, it is planned to progress to a DFS, which will include integrated metallurgical testwork and an updated Environmental Impact Statement.