Managing uranium mine waste

 

Key Points

  • Many industries produce waste of various kinds and most discharge these wastes directly into the environment. The uranium and nuclear industries contain their wastes to their own sites (either mines or nuclear power plants)
  • Management of tailings (mine waste) at uranium mines isolates the material from the surrounding environment and contains the waste on the mine site.
  • The Australian uranium industry applies world’s best practice in designing and building tailings storage facilities and continually improves its knowledge and practice in this area
  • The techniques for managing uranium tailings are essentially the same as those for managing tailings from the mining of any other mineral
  • Independent research demonstrates that tailings management is very successful
  • The fact that uranium tailings are moderately radioactive does not alter their tailings management requirements 

It is sometimes suggested that, because uranium mine waste cannot be monitored for the period of the half-life of the radioactivity in the waste, it would be better not do the mining that gives rise to the waste in the first place.

This proposition misunderstands both the environmental requirements for managing uranium waste (more commonly known as tailings) and the requirements for managing tailings from any mining.

Contrary to some suppositions, environmental requirements do not insist that mines be ‘monitored for 10,000 years’.   The figure of 10,000 years comes, in fact, from a document detailing the Ranger mine’s environmental requirements, namely, that ‘Final disposal of tailings must be undertaken, to the satisfaction of the Minister with the advice of the Supervising Scientist on the basis of best available modelling (emphasis added), in such a way as to ensure that: (i) the tailings are physically isolated from the environment for at least 10,000 years; and (ii) any contaminants arising from the tailings will not result in any detrimental environmental impacts for at least 10,000 years’.

Of course one can’t monitor a uranium tailings storage facility – or any former mine - for 10,000 years. In any case, the tailings task is not to monitor but to isolate the tailings.

The task of managing uranium mine tailings is essentially the same as managing tailings of other mines: to prevent the tailings travelling beyond the storage facility.

Guidelines and standards for best practice exist for stabilising tailings and containing them in ways that isolate them from the environment and greatly reduce – if not eliminate – the risks that they pose.

For example, the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) produces the definitive framework guide; the Minerals Council of Australia produces a strategic framework guide, and the Commonwealth Department of Resources, Energy and Tourism produces a best practice guide.

The techniques for managing tailings in any type of mine vary according to the mine type, geography, geology and weather conditions of each particular site. For example, managing tailings in an arid environment requires different techniques from doing so at a site in tropical or wet temperate environments.

The mining industry and the engineering profession are experienced in managing tailings in all types of environments; it is a core capability and the mining industry manages tailings well.

Individual cases of poor performance will excite emotion but are not good guides to the risks involved in managing tailings.

The Committee on Tailings Dams and Waste Lagoons, a committee of the International Commission on Large Dams, reported in 2001 on the risks of dangerous occurrences in this area and showed that ‘the effect of improving understanding of the behaviour of dams has resulted in improved methods of design and construction’ and that the record of these kinds of dams has improved continuously over the last 150 years.

13% of dams experienced failures during the period 1850 to 1900 and this had reduced to 0.2% by the 1960s. The record shows that problems with tailings dams are few and far between.

The fact that the tailings are radioactive is not very relevant:

  • First, because miners manage tailings according to well-known and well-practiced principles
  • Second, because the radioactivity of tailings is always less than the radioactivity of the ore that contained the uranium in the first place. Mining the ore does not increase the radioactivity. Extracting the uranium from the rest of the material in the ore reduces the radioactivity to around 80 – 85% of its original (natural) level.
  • Depending on the volume of material used to cover and seal tailings dams and isolate them from the environment, the level of radioactivity near the tailings storage will be around the same as or less than the pre-existing background radioactivity level
  • Third, because one of the properties of radiation is that it disappears over time,  while the toxic materials in the tailings dams from other minerals that do not have half-lives never disappear.

Solution mining (or in situ recovery) obviates the need for tailings management.

The geological structures which make solution mining feasible (that is, the containment of a uranium deposit within a geologically sealed structure, known as an aquifer) facilitate the containment of materials that would otherwise be brought to the surface and managed as tailings in an underground or open-pit mine. The solutions used to dissolve the uranium and bring it to the surface do not dissolve the other radioactive elements within the deposit. They remain contained underground.

April 2010