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

• 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

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

Loire River (EDF)

Loire River system

Allier

CherIndre

Creuse

Vienne

Clain

Belleville

DampierreSt Laurent

Chinon

Civaux

Beaulieu

Gien

Ouzouer

Maine

Orléans

Beaugency

NouanBlois

Tours

La ChapelleBertignolles

Saumur

Angers

Montjean

Vienne River system

Civaux

Clain

Creuse

Loire

Vienne River system

Civaux

Clain

Creuse

Loire

Legend:

NPP locationCalculation station

• 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

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

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

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)

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

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

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)

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?

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.

Transfer parameters - Chernobyl

• Generally good agreement all species – Sr, Pu, Am, Cs

0.1

1.0

10.0

100.0

Pu Great tit Pu Long-tailed tit Pu Bank vole Am Bank vole

Bq

kg

-1 f

w

Transfer parameters - Chernobyl

• Generally good agreement all species – Sr, Pu, Am, Cs– Tier 3: some predicted 95th %ile < maximum

observed

Measured whole-body activity concentration (Bq kg-1 FW)

Predicted whole-body activity concentration

(Bq kg-1 FW)+

Species/ area n Mean Min. Max. Mean

5th

percentile 95th

percentile 137Cs Low C. glareolus 3 3820 3140 4660 A. flavicollis 18 3130 1270 9750

19900 1500 69500

Medium C. glareolus 39 70500 17000 252000 A. flavicollis 10 59700 24100 143000

116000 8310 411000

High C. glareolus 2 2260000 1350000 3180000 Microtus spp. 11 611000 252000 1140000 268000 21600 952000 A. flavicollis 2 145000 108000 183000 90Sr Low C. glareolus 3 7710 3050 10300 A. flavicollis 18 7410 1390 21100

3940 292 13300

Medium C. glareolus 39 19500 4290 36000 A. flavicollis 10 24700 16000 34000

33400 1940 121000

High C. glareolus 2 81300 65600 96900 Microtus spp. 11 107000 38100 167000 102000 6550 357000 A. flavicollis 2 66600 46600 86700

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)?

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

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

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?]

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 ?

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

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

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])

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