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Experiences from testing the ERICA Integrated Approach

Experiences from testing the ERICA Integrated Approach. Case study application of the ERICA Tool and D-ERICA. Objectives. To assess the applicability of draft versions of D-ERICA and ERICA Tool

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Experiences from testing the ERICA Integrated Approach

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  1. Experiences from testing the ERICA Integrated Approach Case study application of the ERICA Tool and D-ERICA

  2. Objectives • To assess the applicability of draft versions of D-ERICA and ERICA Tool • To compare predicted and observed activity concentrations in biota (and water/sediments for aquatic ecosystems) • Where possible, to compare observed radiation induced effects with estimated doses and predicted effects • To make recommendations to the ERICA consortium

  3. Drigg Coast Sand Dunes UK (WSC, Uni. Liverpool) • Natura 2000 site – receiving contamination from Sellafield marine discharges • Opportunity to address identified deficits in FASSET methodology & respond to stakeholders • ERICA sampling campaign • Full role-play assessment of regulated site

  4. Loire River (EDF) • River receives discharges from a number of nuclear power plants • Opportunity to compare ERICA predictions to those of model developed specifically to assess the Loire

  5. Sellafield Marine (NRPA & WSC) • Anthropogenically contaminated marine site • Comparatively large database available (1980 and 2005 assessed) • Opportunity to compare with site specific model predictions • Full role-play assessment of regulated site

  6. Komi Republic (NRPA & IOB) • High levels of natural radionuclides (Th and U series) – range of historical practices • Comparatively large database now available • Biological effects studies in area

  7. Chernobyl (CEH & IRL) • ERICA study to measure external dose rates to small mammals at three sites using attached TLDs (within 10 km zone) • Large database of whole-body activity concentrations available for wide range of biota (predominantly Cs & Sr, some actinides)

  8. Exposure to background radiation • Drigg case study Tier 2 conservative RQ > 1 due to natural background radionuclides • ERICA is for assessment of incremental dose rates • Example of poor definition of ERICA Integrated Approach in draft documentation • Now clearly stated and discussed

  9. Conservatism at Tier 2 • Tier 2 conservative dose rate should ≈ Tier 3 95th %ile estimate • Sellafield Marine Case Study (using one of two possible media inputs) Tier 3 - 95th%ile higher than Tier 2 conservative estimate

  10. Conservatism at Tier 2 • Tier 2 conservative dose rate should ≈ Tier 3 95th %ile estimate • Sellafield Marine Case Study (using one of two possible media inputs) Tier 3 - 95th%ile higher than Tier 2 conservative estimate • Not observed for other case studies (some reservations re input water concentrations)

  11. Conservatism at Tier 2 • Tier 2 conservative dose rate should ≈ Tier 3 95th %ile estimate • Sellafield Marine Case Study (using one of two possible media inputs) Tier 3 - 95th%ile higher than Tier 2 conservative estimate • Not observed for other case studies (some reservations re input water concentrations) • Need to further test Tier 2 ‘uncertainty factor assumptions’ • in PROTECT scenarios?

  12. Lichen • Lichen and Bryophyte’ reference organism is the limiting organism for a number of radionuclides (mostly natural isotopes). • for 210Po, the associated EMCL value of 25 Bq kg-1 DW soil • due to high CR • The use of a soil-biota CR may not be applicable • Acute exposure data (for mortality) suggest that lichens have a low radiosensitivity. Implementation of a predicted no effects dose rate (as used to define the screening dose-rate at Tiers 1 and 2) derived to be protective of all organism types within terrestrial ecosystems may be overly conservative for lichens and mosses.

  13. Transfer parameters - Chernobyl • Generally good agreement all species – Sr, Pu, Am, Cs

  14. Transfer parameters - Chernobyl • Generally good agreement all species – Sr, Pu, Am, Cs • Tier 3: some predicted 95th %ile < maximum observed

  15. Transfer Parameters - Komi • Generally Ra-226, Th-232 & U-238 ‘agree well’ or are over predicted (ash weight soil used): • Ra-226 tree under predicted • U-238 & Th-232 under predicted voles [limited data available] • Non-linearity (potential but not investigated)?

  16. Transfer parameters - Drigg • Cs-137 consistently over predicted (1-2 orders of magnitude) • Most default data relate to post Chernobyl studies (likely to be for organic soils) • Am-241 under predicted in higher plants • Site receives aerial deposition (sea-land) • A number of CR values tested were ‘guidance values’ – gave reasonable predictions

  17. Transfer parameters - freshwater • No case study tested freshwater CR values • ERICA participating in EMRAS BWG freshwater scenario • Test version Kd values criticised as being ‘old’ • Updated with EMRAS TRS364rev outputs

  18. Transfer parameters - Marine • For Pu, Am and Cs – generally reasonable agreement • Over predicted fish Pu [but observed data edible tissues not whole-body] • Cs-137 activity concentrations in seabirds 500x higher than observed data [observed data all for gull sp. – feeding in terrestrial ecosystems?]

  19. Dosimetry • Chernobyl case study – predicted external dose rate predictions agreed well with measurements from ‘TLD-collars’ • Komi and Chernobyl – reasonable agreement between gamma air kerma rates and predicted external dose rates (& TLD results for Chernobyl) • Include ability to input dose rates ? • Include advice that gamma air kerma rates can be used to verify external dose rate predictions ?

  20. Dosimetry – create organism • Restriction on size: • 0.0017 to 550 kg on soil • 0.0017 to 6.6 kg in soil • 0.035 to 2 kg for flying animals • Limits usefulness (e.g. for European bat spp., large burrowing animals etc.) • Revised Help documents limitations and provides advice on approaches to best model user defined organisms (& limitations) • Limitations more obvious on Tool screen

  21. Effects summaries • Tier 2 effects summaries criticised as not being very useful (often lots of contradictory data or no data) • Now improved - summary’ by dose range

  22. Tier 3 link to FREDERICA • Criticised as being of little aid to decision maker as expert interpretation would be required • But this is Tier 3 and it is anticipated that experts will need to be consulted • FREDERICA is an up to date, freely accessible database which provides a useful expert tool (others outside the ERICA consortium are using it [e.g. Chambers et al. 2006])

  23. ERICA outputs – the future • Consortium agreement to manage potential Tool development and maintain databases • Tool and databases will continue to participate within IAEA EMRAS BWG scenarios (outputs available end 2007) • ERICA outputs will be assessed within the PROTECT project • Special issue of J. Environ. Radioact. in preparation

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