Background Objective - to demonstrate Radioecological Risk Assessment

1. Application of ERICA outputs and AQUARISK to evaluate radioecological risk of effluents from a nuclear site J. Twining & J. Ferris

2. Outline of talk • Background Objective - to demonstrate Radioecological Risk Assessment • Dose Assessment software - EXPOSURE • FASSET Radiation Effects Database - RESPONSE • Ecological Risk Assessment (AQUARISK) • Case Study in Radioecological Risk Assessment • Results • Conclusions Quantitative, probabilistic, radioecological risk assessment

3. Radiological Dose - EXPOSURE • Radiological Impact Analysis for Coastal Aquatic Ecosystems V1.15 and Freshwater Ecosystems V1.15 • Converts measured or modelled radioactivity concentrations in water (Bq L-1) into dose rates (Gy hr-1) • For a range of radiologically significant nuclides, biota and habitats • Each organism is represented as an ellipsoid for LET calculations • Assessment of dose to each organism is determined using concentration factors (internal dose) and positioning relative to soil/sediment or water (external dose). Quantitative, probabilistic, radioecological risk assessment

4. Radiological Effect - RESPONSE (FASSET Radiation Effects Database, FRED) • FRED is a database of published information on the effects of acute and chronic exposure to ionising radiation on different biota (EC 5th Framework FASSET initiative) • Groups data by: • wildlife “group” (e.g. amphibians, reptiles, mammals etc.) • umbrella endpoint: mutation, morbidity, reproduction, mortality • Provides information on dose (rate) response Quantitative, probabilistic, radioecological risk assessment

5. Exposure curve Response curve Probability density (derived from frequency of observations) % of species likely to be affected (Log) Dose-rate (µGy hr-1) reduction in dose-rate required to achieve a tolerable level of harm Ecological Risk Assessment (AQUARISK) • A 3-tiered approach • Tier-1: Comparison with regulatory limits or guidelines • Tier-2: Desk-top study involving available and relevant literature data • Tier-3: Site-specific data and modelling • The 2nd & 3rd Tiers use probability density functions to derive site &/or species specific acceptability criteria • Convolution of the Exposure and Response PDFs • determines the likely degree of ecological impact and • the extent of • remediation • required

6. Case Study - Scenarios • Effluent releases from ANSTO at the LHSTC in Sydney, Australia • (1) Routine releases into the marine environment at Potter Point via the sewage system and tertiary treatment at Cronulla STP • (assumes 735x dilution as realistic for the site, chronic exposure) • (2) Possible accidental release into the Woronora River after failure of the main holding tank • (assumes no loss of activity overland, no dilution, acute exposure) Quantitative, probabilistic, radioecological risk assessment

7. Scenarios (1) Potter Point • (2) Woronora R

8. AQUARISK Input data - EXPOSURE • Monitoring data for 3H, 60Co, 131I & 137Cs over Jan 2002-Jun 2003 based on monthly averages • Activity concentrations were converted to dose rates using either Coastal or Freshwater RIA software (using updated CFs and default weighting factors) • Once converted to dose-rate no differentiation was made for radionuclide • Only used output for organisms that corresponded to data available in the FASSET Radiation Effects Database (FRED) Quantitative, probabilistic, radioecological risk assessment

9. EXPOSURE Estimation • Dose-rate from averaged radionuclide concentrations • - Scenario #1

10. EXPOSURE Estimation • Dose from averaged radionuclide concentrations • - Scenario # 2

11. AQUARISK Input data - RESPONSE • FASSET Radiation Effects Database (FRED) (using categories and information in the FRED to select data for use in Radioecological Risk Assessment) • HNEDRs and LOEDRs only, and excluding ‘Background’ data (retains ~10% of available data) • no distinction based on radionuclide • no discrimination based on effect measured (all adverse effects assumed to be ecologically relevant) • all units converted to Gy hr-1 or Gy (using conservative assumptions) Quantitative, probabilistic, radioecological risk assessment

12. RESPONSE Estimation • Dose-response cumulative probability (data from FRED)

13. Results: Tier-1 assessment • Scenarios (1) and (2) both pass a Tier-1 assessment against international recommendations Garnier LaPlace et. al. 2006 – Freshwater ecosystems  10Gy hr-1 Maximum estimated dose rates for all spp. (Gy hr-1, n = 162) (1) Routine release into a marine ecosystem 0.3 [(2) Accidental release to a freshwater system 8.7] Quantitative, probabilistic, radioecological risk assessment

14. Results: Tier-2 AQUARISK-derived criteria (using data selected from the FRED) • Criteria for 90-95% protection (using Acute &/or Chronic data selected from the FRED) cover the range of international dose-rate recommendations (i.e. 10 – 400 uGy.hr-1) • Criteria based exclusively on chronic RESPONSE data are substantially lower • Max. est. acute dose in Scenario (2) is 0.006 Gy Quantitative, probabilistic, radioecological risk assessment

15. Results: Tier-2 Assessment • Probability of criteria exceedence Quantitative, probabilistic, radioecological risk assessment

16. Results: Tier-2 Assessment (cont.) estimated proportion of affected species • Convolution of the EXPOSURE and RESPONSE probability density functions indicates the % of species potentially affected • Scenario (1) - Marine = 1.5 to 2.5% (depends on selection of ‘Acute & Chronic’ or ‘Chronic only’ RESPONSE data) • Scenario (2) - Freshwater = 0.2 to 0.3% (depends on selection of ‘Acute & Chronic’ dose-rate data or ‘Acute only’ dose data) Quantitative, probabilistic, radioecological risk assessment

17. Conclusions - Case study • Scenarios (1) and (2) pass the Tier-1 RRA and hence can be considered of low risk to the organisms in the receiving environments • Tier 2 assessments using AQUARISK indicate lower dose rate criteria may be applied for chronic, routine releases under Scenario (1) • - Operational efforts should focus on Co-60 • However, low species impacts are predicted for either scenario even when all conservative assumptions have been applied in line with the Precautionary Principle. • Biomonitoring under scenario (1) has not shown any adverse effects at Potter Point Quantitative, probabilistic, radioecological risk assessment

18. Conclusions - general • Available software can be conservatively and successfully applied to RRA • Calculated exposure criteria (90-95% spp protection) are comparable to published recommendations, BUT chronic exposure criteria are substantially lower • Straightforward technique was used here • - Scenario selections could be more realistic (mixing-zone dilutions and bioavailability) and can be refined to suit other site-specific applications • Improved selectivity of RESPONSE data will help (more site-relevant data recovery from the FRED) Quantitative, probabilistic, radioecological risk assessment

19. Some Lessons • Bioavailability (particulate adsorption) • Co-60 dominant in the marine environment • Categories within FRED(ERICA) Quantitative, probabilistic, radioecological risk assessment

20. Thank you.