Estimating doses from Aboriginal bush foods post-remediation of a uranium mine

PUBLIC EXPOSURE TO EXTERNAL GAMMA RADIATION ON A MINE LANDFORM COVERED BY LOW URANIUM GRADE WASTE ROCK

Public exposure to external gamma radiation on the waste-rock-covered-8.5-km2-planned final landform from rehabilitation of the Ranger uranium mine was assessed. The average above-background dose rate from external gamma radiation on the planned final landform was determined to be 6.0 × 10-3 mSv d-1. This dose rate was one order of magnitude higher than that for inhalation of radon progeny and two orders of magnitude higher than that for inhalation of radionuclides in dust on the final landform. The above-background annual effective dose to the public from external gamma radiation when the envisioned land use by Aboriginal traditional owners was averaged over the entire 79 km2 Ranger Project Area was about 4.1 × 10-2 mSv. The results of this study may provide general guidance to sites elsewhere on the relative importance of the external gamma pathway and assist in the development or assessment of rehabilitation plans for uranium mining sites.

Modelling the dispersion of radon-222 from a landform covered by low uranium grade waste rock

The dispersion of ²²²Rn from the planned remediation of the Ranger U mine in the wet-dry tropics of Northern Australia was modelled. Dry and wet season contour maps of ²²²Rn dose normalised to ²²⁶Ra activity concentration in the proposed waste rock substrate on the remediated landform were developed. Three example exposure scenarios were assessed based on an anticipated waste rock ²²⁶Ra activity concentration of 800 Bq kg^-1. The estimated above-background annual dose from ²²²Rn to hypothetical receptors at the Aboriginal community at Mudginberri (∼10 km NNW) was 0.005 mSv and at the township of Jabiru (∼7 km W) was 0.033 mSv. The estimated above-background annual dose for the hypothetical worst case scenario, representing a receptor 1 km WNW of the landform centroid during the dry season and at the centroid during the wet season, was 0.13 mSv. Variability analysis on the 20 y meteorological dataset used in the dispersion modelling showed that the dry and wet season ²²²Rn dose predictions in any single year could be approximately double those of an average year, which suggests that estimates of average ²²²Rn dose should potentially be doubled if the assessment aim is to demonstrate compliance with the public dose limit.

Whole organism to tissue concentration ratios derived from an Australian tropical dataset

Whole organism to tissue concentration ratios (CR_wo-tissue) were derived for six wildlife groups (freshwater birds, freshwater bivalves, freshwater fishes, freshwater reptiles, freshwater vascular plants and terrestrial mammals). The wildlife groups and data represented species common to tropical northern Australia. Values of CR_wo-tissue were derived for between 6 and 34 elements, depending upon wildlife group. The values were generally similar to international reference values. However, differences for some element-tissue combinations could affect radiation dose estimates for wildlife in certain environmental exposure situations, including uranium mining, where these data are intended to be applied.

Australia's proactive approach to radiation protection of the environment: how integrated is it with radiation protection of humans?

Australia's regulatory framework has evolved over the past decade from the assumption that protection of humans implies protection of the environment to the situation now where radiological impacts on non-human species (wildlife) are considered in their own right. In an Australian context, there was a recognised need for specific national guidance on protection of non-human species, for which the uranium mining industry provides the major backdrop. National guidance supported by publications of the Australian Radiation Protection and Nuclear Safety Agency (Radiation Protection Series) provides clear and consistent advice to operators and regulators on protection of non-human species, including advice on specific assessment methods and models, and how these might be applied in an Australian context. These approaches and the supporting assessment tools provide a mechanism for industry to assess and demonstrate compliance with the environmental protection objectives of relevant legislation, and to meet stakeholder expectations that radiological protection of the environment is taken into consideration in accordance with international best practice. Experiences from the past 5-10 years, and examples of where the approach to radiation protection of the environment has been well integrated or presented some challenges will be discussed. Future challenges in addressing protection of the environment in existing exposure situations will also be discussed.