The IAEA is updating its simple methodology for calculation of doses to people from radioactive discharges.
The update will provide a harmonised dose assessment methodology for both humans and flora and fauna. The
approach is intended for the assessment of planned releases from facilities and estimates radiation exposure
during the 100th year of discharge (expected life-time of a nuclear facility). The environmental protection elements
of the methodology will, as far as practicable, utilise relevant aspects of the ICRP’s framework for environmental
protection. Here we describe the new IAEA methodology for calculating the radiation exposure of
terrestrial wildlife focussing on differences with existing methodologies and demonstrating the potential impact
of these differences.
The application of whole body concentration ratios, CRwo-soils, is often aimed to be conservative. However, it has
been suggested that the application of CRwo-soils in situations of prolonged atmospheric discharges will result in
an underestimation of the exposure of plants and some animals. This is because radionuclides deposited onto
plant surfaces are predicted to contribute a significant component of the total plant activity. Ignoring externally
deposited radionuclides from the assessment is also inconsistent with models used to assess human exposure.
Consequently, the new methodology adopted by the IAEA incorporates an explicit consideration of this exposure
pathway, including consideration of herbivorous animals feeding on plants with external deposition.
Other differences in the new approach compared to existing environmental assessment tools are the correction
of CRwo-soils for radionuclide physical half-life and the approach used to consider the scenario-specific contribution
of radioactive progeny to parent radionuclide dose.
The paper will compare results using the existing and new methodologies