Reference levels for existing exposure situations in Australia
The reference levels for existing exposure situations in Australia are:
| Application | Reference level |
|---|---|
Exposure to indoor ²²²Rn For applying optimisation of protection for dwellings, mixed–use buildings and most workplaces the derived reference level is 200 Bq m-3 1 | 10 mSv y-1 |
| Transition from an emergency exposure situation to an existing exposure situation3 | 20 mSv y-1 |
| Remediation of legacy and post–accident sites4 | 10 mSv y-1 |
| Aircrew exposure to cosmic rays5 | 6 mSv y-1 |
| Radionuclides of natural origin in commodities6 | 1 mSv y-1 |
| Radionuclides in bulk material of commodities7 | 1 mSv y-1 |
- If measured values are found to consistently exceed this level, consideration should be given to possible remedial action within the context of optimisation.
- Employers should ensure that the activity concentration of ²²²Rn in the workplace is as low as reasonably achievable below this derived reference level and should ensure that protection is optimised. If, despite all reasonable efforts by the employer to reduce the activity concentration of radon, the activity concentration of ²²²Rn in the workplace remains above the derived reference level, the relevant clauses for occupational exposure in planned exposure situations as stated in the Code for Radiation Protection in Planned Exposure Situations, RPS C–1 (ARPANSA 2016), must apply (clauses 3.1.12, 3.1.20–3.21 and 3.2.10, RPS C–1).
- As a long-term objective the reference level for the optimisation of protection for the transition from an emergency exposure situation to an existing exposure situation should be selected from the lower part of the reference band of 1-20 mSv y-1.
- In Australia, an intermediate reference level of 10 mSv y-1 applies to legacy and post-accident sites and revision of the intermediate reference level to improve the situation progressively is required. The remediation of contamination from past activities or accidents requires a site–specific reference level in the range of 1 to 20 mSv y-1, based on prevailing circumstances to guide the optimisation of radiation protection after an assessment of the site. The reference level for remediation applies to additional exposure (i.e. above natural background levels).
- A reference level of 6 mSv y-1 is considered appropriate for use in Australia and is endorsed by employers.
- Exposure to radionuclides in each of the commodities. The investigation levels for drinking water would be triggered at a lower dose than the 1 mSv y-1 reference level (for more information see NHMRC 2011).
- The clauses for existing exposure situations apply to material containing radionuclides of natural origin at an activity concentration of less than 1 Bq g-1 for any radionuclide in the uranium decay chain or the thorium decay chain and of less than 10 Bq g-1 for 40K. For radionuclides of natural origin, bulk amounts of material are to be considered on a case–by–case basis by using a dose criterion of 1 mSv y-1.
