Australia's only research reactor is providing an important service for the growing mineral sands industry - while also protecting workers and consumers from naturally occurring radioactivity.
Nearly everything contains naturally occurring radioactive elements that emit low levels of ionising radiation, but some things are more radioactive then others, and may need to be considered carefully. These include the wide array ofproducts that come from mineral sands, such as the pigment used in white paint, ceramics, and a range of specialist products used in industry. Mineral sands, which have emerged as a $1.2 billion export industry for Australia, contain low levels of naturally occurring radioactivity, which occurs in the original ore.
Australia's only nuclear research reactor, operated by the Australian Nuclear Science and Technology Organisation (ANSTO) at Lucas Heights, plays a significant role in analysing mineral sand concentrates. The key to one of these processes is Neutron Activation Analysis (NAA), a technique which uses the reactor to determine element concentrations in a sample.
These analyses are carried out by Becquerel Laboratories. Since 1987, Becquerel has used the reactor to analyse tens of thousands of mineral samples, providing an important service for mining companies seeking to accurately assess the potential of mining projects. NAA causes isotopes of a range of elements to become radioactive by capturing one extra neutron during neutron bombardment in the reactor. This induced radioactivity can then be measured with great sensitivity and this in turn allows determination of a wide range of elements in the sample.
While NAA has been a popular method for many years for assays of a range of elements including gold, tungsten and antimony, the procedure is also proving increasingly popular in the mineral sands industry where the radioactiveelement, thorium, can be found in significant concentrations associated with such minerals as zircon, rutile, ilmenite and the rare earth minerals.
According to ANSTO's Doug Collier, an expert in naturally occurring radioactivity in minerals, NAA is the "Rolls Royce method", without the price tag, for accurately detecting thorium in minerals.
"The mineral sands industry is at the forefront of the non-uranium mining industry in recognising the need to manage naturally occurring radioactivity in minerals," he said. "NAA is a method that can be used to detect the potential radioactivity of samples before they are processed. If you want the right information for thorium, you would initially choose NAA, which also has the advantage of being fast compared to some other methods. This allows the radioactivity to be better managed, ultimately protecting workers and consumers alike."
According to Dr David Garnett, CEO of Becquerel Laboratories, an additional benefit of the process is that it does not need to dissolve samples. Some minerals are extremely difficult to dissolve and this can be a major problem with other analytical techniques. In contrast NAA provides a total analysis of each sample regardless of its mineralogy.
"Neutron Activation Analysis has been tried and tested over many years, with increasingly sophisticated methods of measurement," Dr Garnett said. "This method is widely regarded as a fundamental analysis technique used by the 'umpires' to settle any kind of uncertainty. As such it has an important role in increasing the confidence people have in Australian mineral analyses."