The detector facilitates the identification of buried uranium deposits that have no surface radiometric expression.
The use of Alpha Track detectors offers explorers the opportunity of inexpensively detecting uranium mineralisation at depth.
Uranium is the first element in a long series of radioactive decay that produces radium and radon. Uranium is referred to as the parent element, and radium and radon are called daughter products.
The use of radon gas detectors to identify uranium mineralization is well known and has been applied since the 1960’s. Because radon is a gas, it has much greater mobility than uranium and radium, which are fixed in the solid matter in rocks and soils. Radon migrates to the surface by escaping into fractures and openings and into the pore spaces between grains of soil. The ease and efficiency with which radon moves in the pore space or fracture effects how much radon is detected at the surface. If radon is able to move easily in the pore space, then it can travel a great distance before it decays, and is therefore detectable at the surface above a uranium occurrence.
The Alpha Track method uses a small cellulose-nitrate film attached to the side of a small plastic sample cup. The film is not affected by light or any other form of electromagnetic radiation. The film is only sensitive to alpha particles emitted by daughter products of uranium (mainly radon).
Normally, the Alpha Track detectors are buried in holes approximately 50 to 75 cm deep over the area to be investigated. Commonly, a 100 meter by 100 meter grid is used. This may vary depending on the nature of the suspected mineralization and the size of the area being explored. The detectors are left in place for 30 days after which they are retrieved and returned to Alpha Track for processing.
The processing of the detectors entails the etching of the nitro-cellulose film. This etching process highlights the “damage tracks” caused by the alpha particles when they impinge on the nitro-cellulose film.
These tracks are counted optically and expressed in a “track count per square millimeter”. These counts are proportional to the radon gas levels at the sample site. Contour maps showing these results are also generated.
The device is simple to use, low in cost and measures a long-term sample of the radon soil gas and is therefore not subject to short term variations in radon concentrations.
The Alpha Track detectors can be used in areas covered by snow, in very wet areas and in drill holes.
Radon gas detection methods have been applied successfully in many areas of the world. These include the Athabasca Basin, sandstone roll-front deposits in the USA, unconformity vein deposits in Canada and calcrete deposits in Africa and Australia. The technique can also be used as a regional exploration tool. It will identify areas of increased uranium mineralisation and assist in the identification of prospective areas.
A reference guide for the identification of uranium ores and minerals.