Neutron spectroscopy evolved from James Chadwick’s initial discovery of the neutron back in 1932. The evolution of this technology has recently taken another leap forward thanks to its recent application to downhole assaying, which enables near real-time collection of assay data in a fast, semi-autonomous system.
The successful and effective adaptation of this technology to the mineral resources sector was made possible by a partnership between Sodern – the developers of the FastGrade downhole spectroscope and MPC Kinetic – the developers of the semi-autonomous, truck-mounted rig and data logging system, Oresight.
BHP were also heavily involved in bringing this technology across from the oil and gas industry and applying it in their iron ore businesses. Ultimately, this joint partnership and collaboration of minds has resulted in a revolutionary new technology that is fast, accurate and also improves the safety of assay, drilling and blasting personnel.
In simple terms, the FastGrade sensor emits neutrons from a pulsed neutron generator, which penetrate surrounding rock inside the bore hole. As the neutrons penetrate, they collide and interact with the various minerals and materials in the bore hole. Almost instantaneously, these collisions, in turn, emit gamma photons – effectively creating a unique signal from each type of element in the test zone.
A high-resolution Lanthanum Bromide (LaBr) scintillating material is coupled with a photomultiplier to convert the gamma photons to electrical pulses. Complex analytical software and specialised digitisers sort and count each unique signal and process them to build a complete spectrum of the materials’ chemistry present in each segment of the scan as it moves up the bore hole.
MPC Kinetic were instrumental in the development of Australia’s first fully autonomous excavator – featured on the front cover of the AMR in June 2020. This pioneering Australian company turned its attention to building a semi-autonomous carrier system to allow the fast and efficient deployment of the FastGrade sensor in rugged mining environments.
The end result is a truck-mounted system that provides downhole logging with no physical inputs from the operator, removing even more personnel from the blast pad.
Engineering and safety controls on these downhole assay units include:
- Zero manual handling required through mechanical systems.
- Automated winch to maximise logging efficiency and remove potential for human error.
- Automated and manual lockouts associated with radiation detectors.
- Air-conditioned cabins to reduce operator’s exposure to dust, noise and the elements.
- OreSight downhole assay units are operated from a driving position – there is no
requirement for the operator be outside the vehicle when working in mining operations.
All MPC Kinetic vehicles are actively monitored with IVMS as standard to ensure that driving risks are minimised.
Using the WA-built Oresight, integrated with the FastGrade sensor technology, allows the logging of up to 60 bore holes in a 12-hour shift. The collected data is transmitted via 4G to MPC Kinetic’s real-time operations centre – Oresight Central. Once the operator moves the truck to a bore hole and initiates the process, the Oresight system takes over.
The FastGrade sensor is automatically lowered to the bottom of the hole and then raised at the required rate to provide timely, yet accurate, high resolution readings of the ground chemistry in 20cm vertical sections, with up to 80cm total diameter penetration. Case studies have revealed that grade assessment errors have been reduced from 3% to 1% when comparing conventional methods with MPC Kinetic’s new spectroscopy technology.
As the Oresight truck is being moved on to the next hole, the data from the previous hole is being uploaded to the cloud server and is almost instantly made available to mine staff managing the drill and blast process. An assay testing procedure that used to take days has now been condensed to mere hours with the added benefits of increased sample accuracy and greater worker safety.
Oresight could be described as IoT for ore sampling.
Integration with Mine Modelling Systems
Instead of using an ore spotter, the data obtained from the FastGrade sensor can be fed electronically into the mine model, giving management more control of the process and simultaneously making dilution and extraction blocks more accurate. This allows mine planners to assign their mining blocks appropriately. If they want to blast to a surface and they find that the surface is not where it was thought to be, pre-measurement, this information allows them to fine tune the blast appropriately.
Revolutionising In-Pit Assays
This new system sits neatly between the drilling and blasting phases in the pit. The speed and accuracy of the assay results mean that drill rigs are not held up awaiting results and blasting is not delayed. This significantly improves productivity and directly translates to more tonnes recovered per shift.
Furthermore, there is no need for personnel to handle the physical samples that must be gathered for conventional assay testing. This takes even more staff out of harm’s way in the pit, improving overall safety conditions.
There are even more advantages to the FastGrade system over conventional physical sampling. Firstly, sampled data remains in situ for far more accurate resource modelling, which translates directly into more accurate block modelling and higher profitability potential from each blast. Additionally, there is no loss of core, no averaging of sample materials that can result from typical material recovered from RC drilling. Instead of assaying the partially homogenous material recovered from the drilling, FastGrade samples the material in the hole to build a highly accurate sub-surface dataset of both the nature and quantity of the elements present – in 20cm increments.
The Oresight platform’s learning process is calibrated before use at each site. This usually entails logging a training set of data on-site in order to set a benchmark for the geoscience team, which focusses on the elements they are primarily seeking while simultaneously filtering localised extraneous background data.
This initial calibration is a once-off and the calibration is monitored at regular intervals, normally after a set number of logging hours, to ensure this high degree of accuracy is maintained for the life of mine.
Reduced Explosives Cost
The FastGrade tool can provide a spectral response at a high vertical resolution; allowing explosives to be targeted much more effectively than is the case with one or two physical samples gathered from each blast hole.
The high-resolution data also allows ore waste boundaries to be better defined and allows the spectral response to be used to identify formation types. This data can be built into the blasting model, allowing for accurate sequential loading of the blast hole, which will maximise the blast performance both by fragmentation and cost effectiveness.
Reduced Laboratory Costs
Depending on the resource type and product, Oresight’s downhole assays can be used as a partial or complete replacement for assaying at various stages of the resource development and mining process. This leads to a direct reduction of laboratory costs and ancillary costs associated with handling and shipping physical samples. The ability of the tool to gather data in almost all hole types means that the costs associated with twinned core holes as a quality control can also be removed.
Wider Rollout of the Technology
After 10 years of development and 18 months of rollout into the market, MPC Kinetic is ready to broaden the application of this technology into other markets. This will include deployment into bauxite, copper and nickel mining where elements are mined in bulk in open-cut operations. Naturally, this expansion will see Oresight and FastGrade sold internationally to other strong mining regions such as South America, Canada, Africa and Europe.
Once again, MPC Kinetic has demonstrated its ability to develop state-of-the-art technology to deliver more accurate results, in near real-time while simultaneously providing semi-autonomous operation, reducing costs, improving worker safety and improving the accuracy of mine block models.
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