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

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Presentation on theme: "Application of ERICA outputs and AQUARISK to evaluate radioecological risk of effluents from a nuclear site J. Twining & J. Ferris."— Presentation transcript:

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

2 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 Outline of talk Quantitative, probabilistic, radioecological risk assessment

3 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). Radiological Dose - EXPOSURE Quantitative, probabilistic, radioecological risk assessment

4 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 Radiological Effect - RESPONSE (FASSET Radiation Effects Database, FRED) Quantitative, probabilistic, radioecological risk assessment

5 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 2 nd & 3 rd Tiers use probability density functions to derive site &/or species specific acceptability criteria Probability density (derived from frequency of observations) Exposure curve Response curve (Log) Dose-rate (µGy hr -1 ) % of species likely to be affected reduction in dose-rate required to achieve a tolerable level of harm Convolution of the Exposure and Response PDFs determines the likely degree of ecological impact and the extent of remediation required Ecological Risk Assessment (AQUARISK)

6 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) Case Study - Scenarios Quantitative, probabilistic, radioecological risk assessment

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

8 Monitoring data for 3 H, 60 Co, 131 I & 137 Cs over Jan 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) AQUARISK Input data - EXPOSURE Quantitative, probabilistic, radioecological risk assessment

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

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

11 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) AQUARISK Input data - RESPONSE Quantitative, probabilistic, radioecological risk assessment

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

13 Scenarios (1) and (2) both pass a Tier-1 assessment against international recommendations Maximum estimated dose rates for all spp. ( Gy hr -1, n = 162) (1) Routine release into a marine ecosystem0.3 [(2) Accidental release to a freshwater system 8.7] Results: Tier-1 assessment Quantitative, probabilistic, radioecological risk assessment Garnier LaPlace et. al – Freshwater ecosystems 10 Gy hr -1

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 Gy Quantitative, probabilistic, radioecological risk assessment

15 Probability of criteria exceedence Results: Tier-2 Assessment 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 )

17 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 Conclusions - Case study Quantitative, probabilistic, radioecological risk assessment

18 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 Conclusions - general

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

20 Thank you.


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