March 2013 Quarter
Production by quarter
| Langer Heinrich Mine |
Jun Qtr 2012 |
Sept Qtr 2012 |
Dec Qtr 2012 |
Mar Qtr 2013 |
| U3O8 Production (lb) |
1,322,480 |
1,290,462 |
1,418,583 |
1,230,081 |
Production for the March quarter totalled 1,230,081lb U3O8, which was 13% lower than the previous quarter. The plant continued to perform well and in accordance with the design parameters of the Stage 3 upgrade, which was designed around the limitations of the NamWater infrastructure that supplies water to the mine. Consequently, any disruption to the supply of water has a direct impact on production and during the quarter the supply was disrupted as NamWater acted to upgrade its supply infrastructure in the region to accommodate the additional water requirements associated with new mining developments (mainly the new Husab uranium mine).
This action is part of a long-standing initiative by NamWater to transition from aquifer water to desalinated water later in the year.
In order to overcome the current water supply constraint on production, an interim agreement is being concluded with NamWater and Areva, the owners of the desalination plant in Namibia, to access additional desalinated water, ahead of schedule, from May 2013. In addition to this, an increased focus on water conservation at site will mitigate against further disruptions.
This combined strategy of a short-term agreement and water conservation measures will eliminate any further disruptions to the water supply in the interim and thus allow a resumption of nameplate or better production.
Mining
The overall mined quantities decreased as planned over the March quarter. The mining schedule was previously revised as part of the cost rationalisation programme. Ore mining and availability remained unaffected.
| . |
Dec Qtr 2012 |
Mar Qtr 2013 |
| Ore mined (t) |
1,191,756 |
829,366 |
| Grade (ppm) |
798 |
823 |
| Additional low grade ore mined (t) |
757,649 |
531,667 |
| Grade (ppm) |
320 |
314 |
| Waste/Ore ratio |
2.54 |
3.88 |
Mining continued in three pits with sufficient ore exposed to fulfil plant feed requirements.
ROM ore stocks have been maintained at around four weeks’ supply while being supplemented by medium grade ores in line with the crusher blend requirements.
Process Plant
The increased plant throughput continued in the March 2013 quarter as reflected below:
| . |
Dec Qtr 2012 |
Mar Qtr 2013 |
| Ore milled (dry tonnes) |
914,847 |
797,696 |
| Grade (ppm) |
805 |
810 |
| Scrub efficiency (%) |
92.7 |
91.1 |
| Leach efficiency (%) |
95.1 |
95.8 |
| Wash efficiency (%) |
86.7 |
88.8 |
| Overall recovery (%) |
87.4 |
86.7 |
Ore feed tonnage through the process plant reduced by 12.8% with total throughput of 797,696t. The reduced throughput can be attributed to the temporary water constraints and some operational issues mainly in ion exchange. These issues have since been rectified. The water constraints, which influenced the general performance capability of the plant, were the most significant.
The scrub efficiency reduced to 91.1% (against a design of 93%). As reported previously, optimisation work in the screening area in order to further improve performance is ongoing, with the classification section remaining the focal area of these optimisation efforts.
The extraction in the leaching circuit continued to improve in line with expectations with a new quarterly record recovery of 95.8%. This improved performance is due to improved heat management and subsequent consistently higher leach temperatures as well as the previously reported initiatives on improving throughput consistency.
The efficiencies in the Counter-Current Decantation (CCD) circuit have improved as a result of the continuing optimisation efforts in this circuit. These improvements have had a further benefit of reducing overall water consumption and, as a consequence, reagent consumption leading to sustainable reductions in C1 operating costs. Further modifications and improved operating procedures are being implemented, which should lead to additional improvements.
The overall plant recovery reduced slightly to 86.7%. The most significant contributors were a result of lower scrub efficiency, lower ion exchange (“IX”) efficiency and a reduction in the return solution from the tailings storage facility. The leach section achieved record recovery whilst the wash efficiency also showed a marked improvement from the previous quarter.
Construction work on the newest tailings storage facility (“TSF3”) (full in-pit tailing deposition area) continued during this period and is scheduled for completion in the December quarter. It is now envisaged that the tailings deposition to TSF2 will extend to the second half of calendar year 2013. Construction of TSF2 extension also continued throughout the quarter.
Production Optimisation
Optimisation of the process continued during the quarter with material and sustainable gains being achieved:
-
Water consumption and, as a consequence, reagent consumption and soluble loss, have been significantly reduced;
-
CCD performance has been improved, with further improvements expected over the coming periods;
-
Operational stability has been improved, particularly the front end, with improved downstream performance; and
-
Heat recovery/management has been improved in the leach and flash circuits, resulting in higher average leach temperatures, and consequently, higher leach extractions.
The installation of the Hydrosort classification unit remains on track for commissioning early in the September quarter and is expected to improve front end ore beneficiation in the coming year.
Further optimisation targets are also being developed on the basis of expanded Stage 3 operating experience.