ATMOSPHERIC RADIOACTIVITY MONITORING
Uranium is a naturally occurring radioactive element that is mined in Australia as a commodity for export. Because of the radioactive properties of the mineral resource, uranium mining and milling can result in above background radiation doses to both workers and members of the public. The two airborne pathways that are important and may lead to an increased radiation exposure to members of the public are inhalation of dusts containing uranium and inhalation of radon and its progeny.

Why monitor the air?
Dusts containing uranium that are present in the atmosphere may be inhaled and retained in the lungs. The subsequent decay of uranium and its progeny nuclides can deliver a radiation dose to the soft tissue of the lungs.
Radon in the atmosphere
Radon is a naturally occurring radioactive gas formed through the decay of uranium. It emanates from uranium-bearing soils and rocks to the atmosphere where it is dispersed by wind currents. Radon decays through a series of short-lived progeny nuclides which are also radioactive. The inhalation of radon and its progeny can deliver a radiation dose to the soft tissue of the lung. The radon progeny, once inhaled, give rise to the majority of the radiation dose to people from radon in the atmosphere.

Trucks in operation inside the Ranger Mine pit

An operating open-cut uranium mine such as Ranger, is a potential source of radiation exposure to the local community via inhalation of uranium dusts and of radon and its progeny nuclides. Radon emanates from the orebody, while mining and milling operations can give rise to dusts that may be transported beyond mine lease boundaries. 
Air monitoring sites
The Environmental Research Institute of the Supervising Scientist (eriss) has conducted atmospheric radioactivity monitoring at three sites in the vicinity of the Ranger uranium mine – Jabiru, Jabiru East and the Four Gate Road radon station near Mudginberri – to measure radon progeny in air and long-lived alpha activity condentrations in airborne dust. This monitoring has been ongoing since January 2003. 

Counting dust filters for radon back in the lab

Monitoring results
The monitoring results (shown below) indicate that the contribution from the two pathways to members of the public. Radiation doses are less than 10% of the recommended annual dose constraint as recommended by the International Commission on Radiological Protection. The atmospheric monitoring conducted by eriss provides independent assurance that there is no unacceptable radiation risk to members of the local community from inhalation of radioactivity in air associated with Ranger operations.
Results of radon progeny monitoring (below left) and long-lived alpha concentration measurements (below right) show a seasonal pattern, with lower concentrations occuring in the wet season when generation of dusts and emanation of radon is suppressed.

Results of radon progeny monitoring (left) and long-lived alpha concentration measurements (right). The concentrations show a seasonal pattern, with lower concentrations occuring in the wet season when generation of dusts and emanation of radon is suppressed.

Jabiru water tower radon and dust monitoring station