Atmospheric transport of radon and radon progeny

Background
Current research projects
Some relevant publications

Background

Radon (symbol Rn) is a radioactive gas. Three isotopes of radon occur naturally:

Isotope	Origin	Half-life
Rn-219	Actinium series	3.96 seconds
Rn-220	Thorium series	55.6 seconds
Rn-222	Uranium series	3.82 days

Each of these can be present in the air we breathe, mainly originating from soil and from building materials (eg brick, concrete). The process by which radon transfers from such materials to the air is called 'exhalation'.

Of the three isotopes, Rn-222 is thought to be the most important for human health considerations because of its relatively long half-life. The rate of Rn-222 exhalation from uranium minesite materials (such as ore and waste rock) is greater than that for normal soils because Rn-222 is produced as part of the uranium decay chain.

Because radon is an 'inert' (or 'noble') gas, it does not tend to attach to any surfaces. This means that if an atom of radon is breathed in, it is unlikely to attach to the lungs or airway passages, and will be breathed out again (unless by chance it decays while in the lung). The decay of Rn-222 gives rise to a number of radioactive progeny, and if these are breathed in then they can become attached to the surfaces of the lungs and airways. Consequently, it is the radon progeny which actually cause most of the radiological dose, rather than the radon itself.

Current research projects

Radon emanation studies at rehabilitated Nabarlek mine site

Recording Radon and Thoron emanation rates at the rehabilitated Nabarlek mine site (photo: S Tims)

Radon exhalation rate from the Ranger uranium mine
Radon exhalation from a rehabilitated landform

Radon exhalation rate from the Ranger uranium mine

This project consists of the following parts:

(a) Geographic variability in radon exhalation flux over the Ranger site (carried out in collaboration with the Queensland University of Technology and Ranger uranium mine). Project leader: Dr Andreas Bollhöfer.

(b) Diurnal and seasonal variability in radon exhalation flux at selected locations in the Alligator Rivers Region.
Project leader: Dr Andreas Bollhöfer.

Radon exhalation from a rehabilitated landform

This project aims at measuring radon exhalation and its temporal variability from a trial rehabilitated landform at Ranger uranium mine. Radon exhalation for various cover and vegetation types, taking into account weathering and compaction effects and the effect of developing vegetation on the landform, will be determined.

The project will enable eriss to predict a long term radon exhalation flux from and contribute to the development of soil closure criteria for the rehabilitated Ranger mine.

Project leader: Dr Andreas Bollhöfer.

Some relevant publications

Lawrence CE, Akber RA, Bollhöfer A & Martin P, 2009. Radon-222 exhalation from open ground on and around a uranium mine in the wet-dry tropics. Journal of Environmental Radioactivity 100, 1–8.

Bollhöfer A, 2007. The geographical variability of airborne radon concentration at the rehabilitated Nabarlek mine site during the dry season 2005. Internal Report 527, Supervising Scientist, Darwin. Unpublished paper.

Bollhöfer A, Storm J, Martin P & Tims S 2005. Geographic variability in radon exhalation at a rehabilitated uranium mine in the Northern Territory, Australia. Environmental Monitoring and Assessment 114, 313-330.

Martin P, Tims S, Ryan B & Bollhöfer A 2004. A radon and meteorological measurement network for the Alligator Rivers Region, Australia. Journal of Environmental Radioactivity 76, 35-49.

Akber RA & Pfitzner JL 1994. Atmospheric concentrations of radon and radon daughters in Jabiru East. Technical memorandum 45, Supervising Scientist for the Alligator Rivers Region, AGPS, Canberra.

Akber R, Pfitzner J & Johnston A 1992. Radon transport from Ranger Uranium Mine: A review of the public radiation dose estimates. Radiation Protection in Australia 10, 41-46.

Akber RA, Johnston A & Pfitzner J 1992. Public radiation exposure due to radon transport from a uranium mine. Radiation Protection Dosimetry 45, 137-140.