Rich rewards - uranium mining

Materials World magazine
,
3 Nov 2013

Uranium mining brings with it a host of issues as well as benefits. Nevertheless, demand is on the rise for the foreseeable future, says Mark Kenwright, Associate Director of Geology and Resources at Wardell Armstrong International. So what are the issues to consider?

Nuclear power is an issue that divides public opinion like few others – but there’s no doubt that the global demand for uranium is steadily rising. With oil and gas supplies predicted to run out by the end of this century, and with energy consumption inexorably increasing in line with population growth, some see nuclear as the only viable way of meeting medium-term demand – at least until renewable energy alternatives reach critical mass.

Many governments, including France, Japan and China, are backing their belief in nuclear with major commitments to new nuclear power stations. Thirty-one countries currently generate nuclear power worldwide. As of May 2013, there were 436 operational nuclear reactors for electricity generation worldwide, with 70 new plants in 14 countries under construction and planned to open over the next few years. Turkey and UAE are building plants for the first time, with Lithuania and potentially Estonia planning to re-open or build new ones.

Nuclear provided around 12% of the world’s electricity production in 2011. France leads the way with 74.8% of its demand met by nuclear, while Slovakia, Belgium, Ukraine and Hungary get more than 40% of all their electricity supplies from nuclear and a further 13 countries received more than 25% from nuclear sources.

Quite apart from power generation, of course, uranium is also used in consumer products, food and agriculture, industrial applications and medicine. To match growing world demand, established uranium mines such as those in Niger, Namibia, USA, Kazakhstan and Canada are now being joined by operations in Tanzania, with new exploration in Niger, Kazakhstan and Argentina, among others.

An increasing proportion of uranium, now 45%, is produced by in situ leaching (ISL). Since 2009, ISL operations in Kazakhstan have produced the largest share of world uranium. Conventional underground mining (excluding Olympic Dam) accounts for just under 30%, with conventional open pit just over 20%.

After a decade of falling mine production to 1993, output of uranium has generally risen and now meets 86% of demand for power generation. Current annual global production is around 68kt U3O8, while potential annual demand could well rise to 89kt–137kt U3O8  over the next 20 years.

Estimated future production from existing mines will not be sufficient. The current balance comes from secondary sources, including stockpiled uranium held by utilities, but these are now largely depleted. Reprocessing and recycling can add additional fuel, but this is conducted at only 11 plants worldwide. The shortfall can therefore largely only be filled by increased exploration and extraction.

One factor in favour of uranium exploitation is that it can be mined at far lower grades than other minerals. For example, copper is mined in Democratic Republic of Congo at 1–3% (or 10,000–30,000ppm) whereas uranium can be extracted at only 1,000ppm (0.1%) or lower. At the other end of the scale, gold can be mined at as little of 1g/t or 1ppm. Commodity price is the key to mining economically, as the concentration of these elements ranges from 1ppm to 30,000ppm.

The perception of scarcity drove the spot price for uncontracted sales to more than US$140/lb U3O8  in 2007, although it has settled back to US$40–45 in 2013. Most uranium is supplied under long-term contracts, and these prices are generally at a premium to the spot market.

As oil and gas become increasingly scarce, the price of uranium is likely to increase. This will drive further new investment in additional mines and processing plant. As the price goes up, it will become economically viable to mine more from existing reserves, as well as reprocessing existing waste and tailings dams. Previously uneconomic resources will also become mineable reserves.

Positive findings

Uranium is one of the most abundant elements in Earth’s crust. It is naturally occurring, usually in hard rock such as granite or consolidated sediments such as limestone and sandstone. Exploration is naturally tailored to match the different types of deposit and ore bodies, of which there are typically three: roll front deposits, flat lying tabular ore bodies, and tectonic-lithological deposits typically close to large structures.

So how do the exploration methods for finding uranium deposits compare with those for other minerals? Some of the steps are similar, but many of the techniques are different – especially the use of radiometric measurements down-hole, handheld scintillation gamma detectors, and seismic surveys.

A desk study normally comes first – a review of any existing reports, geophysics, the potential reworking of raw data and new interpretation.

It is also essential to find out who owns the mineral rights and apply to acquire them before committing money to exploration. If they are available (at the right price), a grassroots programme is normally the next step.

This typically involves regional soil sampling on lines at 1–2km spacing with 500–200m spacing along the line. A wide range of elements (around 30–50) are typically assayed using the inductively coupled plasma mass spectrometry (ICP) method.

This leads to the identification of potential regional uranium targets, refined by intermediate soil sampling and ground mapping. Further refinements identify mine-sized potential targets for uranium mineralisation. Once drilling has identified a potential resource, a scoping study makes sense to determine the size and grade of any deposit that is likely to be of economic value.

So much for the theory, but there can be a thousand pitfalls between the initial excitement of finding what looks like a viable deposit and extracting it profitably. As well as issues around CSR, political, cultural and environmental sensitivities, uranium by its very nature brings a unique set of safety and security concerns.

One way to avoid some of the more obvious pitfalls is to build in regular review and reporting milestones. These can be financial, work- or resultsrelated. Rather than getting too caught up in the momentum of an exploration programme, it pays to discover any potential critical flaw very early, before pouring in millions of dollars.

The second key to project success is an early scoping study (once a preliminary resource is delineated) to identify any fatal flaws in a project. As well as saving a lot of time and money this can also reveal any metallurgical issues. Many have found out too late that the uranium horizon is too thin or too deep, that the ore body is in the wrong orientation, that in situ mining is impossible because a local community relies on the groundwater, that there is a major political objection such as proximity to a national park, or simply that there is no local power source or extra electricity supply available. Many uranium deposits, after all, are in the middle of deserts.

Since the in situ recovery method is often used to mine uranium, environmental and social concerns can often be a major factor in the permitting of mines. Holes are drilled at regular intervals into ore bodies in sandstone horizons between impermeable clay layers, allowing an acid or alkaline solution to be pumped through and become impregnated with low-grade uranium. This is then passed through a processing plant for recovery.

After a positive scoping study comes the more detailed feasibility stage. An environmental impact assessment should limit any adverse effect on groundwater, seawater, air or surrounding ecology, including effects from tailings or waste dams. A closure plan is also mandatory, and should also be created for the responsible rehabilitation of the land.

Uranium mining can also attract specific political and safety risks. In May 2013, the Agadez mine in Niger fell victim to a terrorist suicide attack, while radioactive material has been stolen from a uranium plant in the Democratic Republic of Congo and remains unaccounted for. Caesium 137 (used in density probes) represents a potential threat if it were ever to be used in a so-called dirty bomb, and has also been stolen by criminals worldwide.

Such high profile risks and their potentially catastrophic fallout naturally make mining companies and their investors nervous. They call for the most stringent safety and security processes for the protection of mine workers, local communities, mineral assets and the global community.

On the other side of the coin, countries such as Australia have led the way in terms of best mining practice. The In Situ Recovery Uranium Mining Best Practice Guide produced by the Australian government has set the standard worldwide.

Uranium mining has much in common with other types of mineral extraction – but much also that makes it truly unique. If nuclear power generation is to meet the rising global demand for safe and sustainable energy, it asks some big questions of mining companies. However, for those who tap into the right specialised experience and advice, the rewards can be rich indeed.

For more information, contact Katrin Naefe, +44 (0)1295 256138  

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