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Introduction to the ERICA Tool

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1 Introduction to the ERICA Tool
J.E. Brown (Norwegian Radiation Protection Authority)

2 What is ’ERICA’ ? ERICA project = Environmental Risks from Ionising Radiation in the Environment: Assessment and Management, contract no. FI6R-CT ) was co-funded by the European Union and 15 organisations in seven European Countries, between 2004 and 2007. The purpose of the project was to develop an approach whereby the impacts of ionising radiation on the environment could be assessed. ensure that decisions on environmental issues give appropriate weight to the exposure, effects and risks from ionising radiation. Emphasis on safeguarding the structure and function of ecosystems. To fulfil this objective, elements related to environmental management, risk characterisation and impact assessment have been integrated into what was termed the ’ERICA Integrated Approach.’ supported by the ERICA Tool.

3 Underlying approach to EIA in ERICA
Transfer in the environment Estimates of dose to biota from internal and external distributions of radionuclides Establish the significance of the dose rates the organisms are exposed to

4 Reference organisms Built around concept of reference organisms
ERICA reference organisms Selected on the basis of criteria – radioecological sensitivity, radiosensitivity, ecological relevance Bias towards European species Protected species in Europe – connection to legislation All default information on transfer and dose-rate estimation relate to these entities

5 Examples of reference organisms

6 Radionuclides Radionuclides to cover expected EIA scenarios, e.g. sources NORM Routine release (reprocessing, power production) accidents High level waste repository Basis for transfer data collation, radioisotopes of these elements basis for dosimetry work.

7 Physical transport – SRS 19
In many cases – empirical data available (monitoring, research studies, bespoke models) When this is not the case, the assessor can use generic models – fully implemented in the Tool

8 Transfer and dosimetry - simplifications
To tackle this daunitng taks we Have to accept that simplifcations are required. We can begin by contructing conceptual models which are themselves simplifcations of reality – this is taken from a coneptualised ecosystem as present by Ward Whicker and co workers. This type of conceptual model can be further simplified looking a particular components of the system in isolation, an example being soil to plant uptake that can, as we have done in ERICA, be modelled using a concneration ratio. In considering dose-rates to organisms we alos need to simplify the situation – on the left we have an aquatic invertbrate with numerous appendages – on the tight we have an idealised form opf this organism in the form of an ellipsoid allowing simpler dose-rate calculation and interpolation between simplifed forms of various sizes. Dose rate µGy/h per unit activity Bq/kg f.w.

9 Screening Dose-rate EU TGD used : protective of function and structure of ecosystem Dose-response curves from different extracted from the FREDERICA database Dose-effect curves for individual studies EDR10 = dose-rate which gives a 10 % effect in endpoints. Species Sensitivity Distribution  ”Hazardous Dose-rate 5 %” – (10 % effect in 5 % of species) Safety factor of 5 used (uncertainty and extrapolation) to derive a PNEDR. Screening dose rate (PNEDR) = 10 mGy/h Protective of sensitive endpoints (MB, RC) in sensitives species. PNEC = predicted no-effects concentration I dette sammenheng forskjelle statistisk metoder har vær brukt til å gi verdien som kan bli brukt i systemen. En hoved verktøy er den species sensitivity distribution hvor dose-effekt data for en utvalgt økosystem (f eks freskvann akvatisk) er tegnet inn som en kumulativ frekvens kurve, derretter en beste tilpassing linje er derivert og en PNEC = predicted no-effects concentration) kan bli beregnet. I ERICA dette typer verdier plus en sikkerhetsfaktor har vært brukt å berenger en screening verdier for Tier 1.

10 The ERICA Tool - What have we attempted to do ?
Integrate Tiered approach into a user-friendly computerised system Place emphasis on calculation but allow the user to document process/decisions Allow flexibility Each Tier incroporates this basic approach (transfer, dosimtery and comparsion with effects of radiation to the environment) in one way or another. Organised in tiers

11 At all tiers - process documented
Assessment details Assessment name + purpose, author Stakeholder involvement Type, description, reason for involvement, stage of involvement, influence-interest category, means of engagement Problem formulation Detailed description (industrial process, discharge regime, receiving medium, ecosystem, regulations) Transfer pathways and assessment endpoints Conceptual model Record decision Justification check on efficacy of stakeholder involvement

12 Sequence in the Tool – initial information

13 Data entry At Tiers 1 & 2, user can either
Enter empirical/bespoke-model data directly Use generic (transport) models (IAEA SRS-19) to generate activity data At Tier 3, generic models are unavailable as these generally provide conservative estimates of activity concentrations; more detailed analyses expected at this stage

14 Available models

15 Tier 1 – derivation of EMCL
Essentially this is the activity concentration of a given radionuclide in media (soil, sediment water) that will result in a dose-rate to the most exposed reference organism equal to the screening dose-rate. ‘F’ depends upon reference organism type (affects the DCC values, CRs and position within habitat) radionuclide (affects the DCC values, CRs and Kds). Where: F is the dose rate that an organism will receive for the case of a unit concentration in environmental media (in µGy/h per Bq/L or kg of medium). Dlim is the screening dose-rate or PNEDR (default = 10 µGy/h (ERICA D5); tool allows 40; 400 µGy/h (IAEA conclusions) or custom to be selected) The Environmental media concnetration limit is simply defined as the limiting dose or predictned no effects dose-rate divided by the factor F define as the dose-rate that an organism will reciecd for the case of a unit concnetration in environmental media.

16 Tier 1 Risk Quotients Where RQn = Risk quotient for radionuclide “n” Mn = measured activity concentration for radionuclide “n” in medium M in Bq per L for water or Bq per kg of soil/sed EMCLn = Environmental Media Concentration Limit for radionuclide “n” (same unit) User prompted to enter (maximum) activity concentrations in environmental media only. Results : If RQ < 1 the probability of exceeding the benchmark is acceptably low (< 5%) - justification for terminating risk calculation at this stage If RQ >= 1 unacceptable probability (>5 %) that benchmark exceeded – further assessment recommended  Tier 2

17 Tier 1 : Sequence in the Tool

18 Tier 2 Measurement endpoint = dose-rates in reference organisms
Assessment context Radionuclide and reference organisms selected by user As for Tier 1 different dose-rate benchmarks can be selected : default ERICA 10µGy/h; 40;400 µGy/h IAEA conclusions; Custom

19 Tier 2 : basic equations

20 Note on DCCs We calculate weighted total dose rates (in µGy/h) and therefore need to consider radiation weighting factors (dimensionless). Where wf = weighting factors for various components of radiation (low beta, b + g and alpha) DCC = dose conversion coefficients in µGy/h per Bq/L or kg

21 Tier 2 – risk quotients Uncertainty Factors applied to ensure conservatism (assume exponential distribution for RQ – described later) Where RQ i= Risk quotient for reference organism “i” DTOT = Total dose rate (mGy/h) DLIM = Screening dose rate or PNEDR (10mGy/h) Again Risk quotients are used. This time they are defined by : This time the analysis is made on an organism by organism basis, i.e. the total dose rate for reference organism 1 is caluclated and compared against the PNEDR, then this i procedure is repeated for ref organism 2 and so on. The RQ for all organims must be less than 1 to avoid exceedence. This is less conservative than the apporach taken at Tier 1 where the limting organism was selected for each radionuclide and the limiting values added together. In practice it is not possible at Tier 2 to treat the RQ on a radionuclide by radionuclide basis because the DLim (PNEDR) relates to a total dose – it is therefore not possible to add radionuclide specific RQs for different organisms in the same way as we did in Tier 1. Furthermore, we feel that the approach outlines for Tier 2 is justified because the assessor needs to actively select the refeence organisms to be included in the calculation at Tier 2 whereas this is not the case at Tier1 (all organisms are automatically included as default). .

22 Tier 2 it is possible to… See how CRs have been derived and edit if necessary (kds can also be edited) Inspect and edit occupancy factors and radiation weighting factors Input data (empirical/bespoke model) for environmental media and/or reference organism (rules to ”back-calculate” depend on data entry) – Note ”expected”values should be entered. Inspect and edit % dry weight soil or sediment

23 Results at Tier 2

24 Tier 2 – Sequence in the Tool

25 Tier 3 – Risk analysis Risk = function (probability, Consequences)
Probablity concerns the uncertainty of results and can be classified Type I – Limited knowledge about the system Type II – Variability In ERICA (Tier 3) the assessor can account for the variability in the underlying parameters.

26 Tier 3 – Sequence in the Tool

27 Web address + Future plans
IRSN, Swedish Radiation Safety Authority, Facilia, CIEMAT, Environment Agency UK, CEH and NRPA. Yearly meetings to discuss improvements and suggestions for new functionality

28 Background literature
Brown, J.E., Alfonso, B., Avila, R., Beresford, N.A., Copplestone, D., Pröhl, G., Ulanovsky A. (2008). The ERICA Tool. Journal of Environmental Radioactivity 99, Issue 9, pp Oughton, D.H., Agüero, A., Avila, R., Brown, J.E., Copplestone, D., Gilek M. (2008). Addressing uncertainties in the ERICA Integrated Approach. Journal of Environmental Radioactivity, Volume 99, Issue 9, Pages Hosseini, A., Thørring, H., Brown, J.E., Saxén, R., Ilus E. (2008).Transfer of radionuclides in aquatic ecosystems – Default concentration ratios for aquatic biota in the Erica ToolJournal of Environmental Radioactivity, Volume 99, Issue 9, Pages

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