Mining, Processing and Engineering

Rössing Uranium’s operations are built on two distinct activities: mining uraniumbearing rock, and processing this ore into uranium oxide for the world's nuclear energy market which fuels the generation of electricity. Our attention is directed towards creating shareholder value and maintaining a secure and viable business, as well as ensuring we remain a long-term contributor to Namibia’s economy.

The uranium located in our mining licence area is embedded in very hard and abrasive granitic rock, known as 'alaskite'. To move the necessary volume of ore and waste, we must conduct blasting operations at least once a week.

Electric and diesel-powered shovels load uraniumbearing ore onto haul trucks, which transport the ore to the primary crushers for the frst stage in the crushing process.

From there, the crushed ore is conveyed to the coarse ore stockpile, where it is reclaimed and put through additional crushing stages in the Fine crushing plant, before the processing stage of operations begins.


Processing plant operations are closely managed from the Central processing control (CPC) room.

 

Mining operations

Having returned to a four-panel shift roster and a seven-day operations schedule at the end of 2015, 2016 witnessed an increase in production of rock mined.

We mined a total of 24.4 million tonnes of rock, of which 8.0 million tonnes were uranium-bearing ore from the open pit and 16.5 million tonnes were waste rock. In addition, 1.2 million tonnes of uraniumbearing ore was fed from the stockpiles to achieve a waste-to-ore strip ratio of 1.97 and a ratio of 0.56 in respect of ore milled to waste rock removed.

The north-west area of the open pit, referred to as Phase 2 of the SJ Pit, was the main source of uranium-bearing ore in 2016.

A key focus in 2016 was on the segregation of light vehicles and heavy mobile equipment traffc, which progressed well in some areas. These efforts will continue in 2017.

The highlight of the year was an initiative on the part of a number of Rössing Uranium's personnel to identify productivity and effciency improvements in both the operational and maintenance areas. The impact on equipment availability has been signifcant. We now need to focus on operational productivity in the areas of shift change, cycle times and payloads.

Drape wire meshing project

During 2016, the geotechnical team completed a drape wire meshing project aimed at reducing the risk of rock falls around the Trolley 14 area of the open pit. The project began towards the end of 2015.

In the preceding reporting year, rock fall had earlier damaged the installed trolley system, leading to increased production costs due to downtime for repairs. This ramp is one of the major arteries of the pit and will be accessed for the life of mine up to 2025.

The slope above Trolley 14 was designed to be 15-m high benches with a 10-m catchment bench. However, in some cases the crest was damaged due to subsequent blasting activities. The result was a rock mass with loose blocks hanging along the crest of the bench face. This was the source of rock fall.

Although temporary measures were put in place to mitigate the identifed risk, it was imperative that a long-term solution be found in order to minimise the danger posed by these rock-fall hazards to the operations below this area. The solution was found in drape meshing.

A total of 16,500 m2 of mesh was laid, requiring 13 rope-access technicians working on the slope with four assistants and a site manager from the contractor company. The project was overseen by Rössing Uranium's geotechnical team.

The meshing was done by ‘rolling’ the wired drape mesh down the slope with the assistance of a crane and winches as well as rope-access personnel tying the mesh together. Each panel was attached to the adjacent panel with wire fasteners forming one, large blanket on the slope.

The benefts of the Trolley 14 meshing project are far reaching, as the meshing area is now safe from any rockfalls from the Trolley 14 area.

Looking ahead

Objectives for 2017 are to improve availability of mining equipment, maintain a highly effective utilisation of equipment and improve scheduling, together with an upgrade of the mining dispatch system.

Processing Operations

The Processing Plant is responsible for the extraction of uranium from mined ore through a number of stages to produce uranium oxide. This product is securely packed and shipped to our customers for further conversion. The aim of the plant is to produce targeted quantities of uranium oxide in the most effcient and safe manner possible.

In the previous reporting year we experienced major challenges at the counter current decantation thickeners and at one point enjoyed only 50 per cent availability of thickeners, which exposed us. With a focused approach from our maintenance and engineering departments, we increased our overall thickener availability from 50 per cent in 2015 to a targeted 80 per cent in 2016. This greatly improved the washing effciency and overall recovery of uranium.

Considerable success was also achieved in removing bottle necks and improving milling effciencies. The goal was to reach 38,000 tonnes crushed per day consistently. After analysing the downtime trend and removing bottlenecks, the frequency with which we achieved more than 2,000 tonnes per hour crushed improved from an average of 11 per cent achieved during the six months prior to the project to 15 per cent during the three months of the project. It is expected that when this improvement continues to increase, it will contribute signifcantly to the achievement of 38,000 tonnes crushed per day. A post-implementation review is scheduled for October 2017 to assess the effectiveness of these improvements in addressing the bottlenecks to consistent throughput.

These efforts, combined with having returned to a 24-7 production, resulted in increased mill throughput and a 48 per cent rise in production from 1,245 tonnes of uranium oxide produced in 2015 to 1,850 tonnes in 2016.

In addition, the mine completed a high calc (calcium carbonate) engineering study and is ready to implement changes to the counter current decantation thickeners in 2017. In the near future we expect to mine higher grade ore with a high calc index. It will therefore be important for the plant to have the capacity to process it. The implementation of these changes will enable us to process high calc ore, with a higher uranium grade, more effciently.

 


A GD drill in the open pit preparing a blast area.

Looking ahead

In 2017 we will continue with the refurbishment of the major process tanks, as well as with the seepage upgrade project. The seepage upgrade project will be implemented to improve the monitoring of seepage systems and improve in seepage recovery.

In addition, a water saving project will be implemented to minimise fresh water usage in the mine as well as maximise the use of recycled water.

 

Engineering and projects

During 2016 the Projects section was responsible for designing and implementing various capital and operational improvement projects. Among others, three major projects were undertaken.

 


Safety signage ensures that workers adhere to the specified PPE (Personal Protection Equipment) requirements for each area.

Relocating section of Trolley 13 infrastructure

Since the mid 1980s when the frst 1200 volt DC trolley-assist system was installed on the 10-degree gradient pit ramps, the mine has operated its 730E Haulpak fleet successfully.

The immediate benefts of trolley assists are that fully laden trucks accelerate from 11.5 km/h to roughly 17 km/h, shortening the cycle times and increasing the refuelling intervals. Also, engine life is beneftting from trolley assist as, in effect, electricity is used as a source of energy to propel the truck up the 10 per cent gradient haul road, instead of diesel. Lastly, by using electricity, the trade of between electricity and diesel usage ensures a huge cost saving.

An assessment in early 2016 indicated that the mine would beneft from fast-tracking the relocation of a section of Trolley 13 line, as the tonnage exiting the open pit via Haulroad 17 compared with Trolley 13 will be ten times more. The relocation was completed during the reporting year and in December 2016, the fully tested, commissioned and operational Trolley 17 line was handed over to mining operations.

Upgrading of lost opportunity and reporting system

Initially developed to be used by the production team to gain visibility on downtimes and reduced feed in the respective plants, the engineering team also started using the lost opportunity and reporting system to identify engineering opportunities and problem areas.

During 2016, the system was upgraded to link in with other Rio Tinto business units for greater effciency. The system was implemented and went live in May 2016; since then it has been expanded to suit Rössing Uranium's requirements. Custom reports can now be compiled to enable decision making to identify bottlenecks in the production process. The system can drive costs reduction through structured problem solving and continuous improvement, while causes of unplanned downtime can be identifed and unplanned production losses reduced.

Reagent plant upgrade

The upgrade of the Reagent plant was successfully completed.

 


Information systems and technology

Radio network in the open pit

The radio network system was upgraded in 2013 from an analogue to a digital system. The current network covers a number of areas at the mine.

The network experienced 'dead spots' which resulted in a safety risk and also impacted production.

During 2016, radio network experts from a local service provider undertook a system review and optimisation exercise. Based on the assessment, adjustments have been made to the antennas and radios. Since then, the system has been stable and fully functional.

The radio network will be extended in 2017 to areas that are not covered yet.

Honeywell fail-over servers moved to IT server room

The Processing plant control system, the Honeywell Experion Plant Knowledge System, is the core of the plant's operation. A failure of this system will result in an inability to operate without mitigation.

In 2015, the mine invested in signifcant upgrades and improvements to this system which now employs newer technologies such as virtualisation and faulttolerant ethernet to improve resiliency.

The Processing plant control network has now been redesigned and developed with the Central processing control building at the centre of operations.