Application of ERICA outputs and AQUARISK to evaluate radioecological risk of effluents from a nucle

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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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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
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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
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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
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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

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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
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Scenarios
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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
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EXPOSURE Estimation

• Dose-rate from averaged radionuclide
  concentrations
• - Scenario 1

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EXPOSURE Estimation

• Dose from averaged radionuclide concentrations
• - Scenario 2

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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
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RESPONSE Estimation

• Dose-response cumulative probability (data from
  FRED)

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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
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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
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Results Tier-2 Assessment

• Probability of criteria exceedence

Quantitative, probabilistic, radioecological risk
assessment
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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
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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
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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
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Some Lessons

• Bioavailability (particulate adsorption)
• Co-60 dominant in the marine environment
• Categories within FRED(ERICA)

Quantitative, probabilistic, radioecological risk
assessment
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Thank you.