Experiences of applying R&D 128, the ERICA Tool and RESRAD-BIOTA: Use and ‘misuse’

1. Experiences of applying R&D 128, the ERICA Tool and RESRAD-BIOTA:Use and ‘misuse’ Mike WoodUniversity of Liverpool

2. Scope • Practical application of the approach(es) you are familiar with • R&D 128 (SP1a) • ERICA • RESRAD-BIOTA • Specifically • What works? • What doesn’t work? • What extra may be required? • etc….

3. Drigg coastal sand dunes, UK • North West of England (West Cumbria) • 10km south of Sellafield • Adjacent to the Low-Level Repository near Drigg

5. Why dunes? • Protected site • NATURA 2000 • Site of Special Scientific Interest (SSSI) • Lake District National Park • Local nature reserve • Support a number of protected species • Potential to be impacted by anthropogenic radionuclide contamination • Includes a ‘non-standard’ contamination pathway (sea-to-land transfer) • Includes organisms for which few or no radioecological data exist (e.g. transfer data for reptiles) • opportunity to test model assumptions and predictions

6. Data collection • Sampling undertaken at Drigg dunes 2005 – present • Part-funded by EC 6th Framework ERICA project, Environment Agency and English Nature (Natural England) • Collected media and biota samples • Sampling undertaken by UoL and analysis by CEH (with support from UoL and WSC)

7. Data available

8. Comparing the models • Measured activity concentrations in media and biota for a range of radionuclides including Sr-90, Cs-137 and Am-241 • Opportunity to compare models on the basis of • ‘Model – Measured’ comparison for activity concentrations in a range of biota • ‘Model – Model’ comparison for dose rate predictions • Aim to use the three models that are readily available to third parties as a minimum • ERICA • R&D 128 • RESRAD-BIOTA

9. Comparing the models • Measured activity concentrations in media and biota for a range of radionuclides including Sr-90, Cs-137 and Am-241 • Opportunity to compare models on the basis of • ‘Model – Measured’ comparison for activity concentrations in a range of biota • ‘Model – Model’ comparison for dose rate predictions • Aim to use the three models that are readily available to third parties as a minimum • ERICA • R&D 128 • RESRAD-BIOTA

10. R&D 128 (SP1a)

11. R&D 128 assessment • The model needs to be parameterised to enable predictions to be made for specific organisms • R&D 128 is an Excel-based spreadsheet tool so there are no wizards to help you do this • Effectively need to create a new organism by modifying values in the spreadsheets

12. R&D 128 assessment • Three important decisions • Geometry • 17 geometries for terrestrial organisms. Which do I choose?

13. Geometry • Geometries set up for particular reference organisms but…. • geometry is just a shape used to define the DPUC value • To identify geometry to use for a new organism need to know the dimensions of the organism (x, y, z) • Can often get average or maximum length from ecological references but rarely, if ever, get all 3 dimensions • Calculate from images has become a fairly common solution • How do you decide which of the 17 geometries (and hence DPUC values) to select? • Comparing organism you wish to create with default reference organism geometries on the basis of ‘surface area:volume ratio’ is the best approach

14. Geometry

15. Geometry • SP1a ranks default organisms on the basis of ‘surface area:volume ratio’ so can select the reference organism geometry to use for your new organism • Problem • SP1a does not tell user how to calculate ‘surface area:volume ratio’ for an ellipsoid based on x,y,z • Solution • Google it! • BUT • An example of where guidance information could be improved

16. R&D 128 assessment • Three important decisions • Geometry • 17 geometries for terrestrial organisms . Which do I choose? • Concentration factors • Appropriate concentration factors to use for the species under assessment • Where possible, used defaults for the organism type e.g. for Mallard used bird • Where not possible, followed SP1a guidance and used CFs for similar organism e.g. for Great Crested Newt used reptile • Occupancy factors • In soil? • On soil? • In air? • Information from R&D 128 defaults, ecological references and knowledge of species

17. Parameters for R&D 128 model run

18. Parameters for R&D 128 model run

19. R&D 128 assessment • Tool is a spreadsheet system with worksheets that cannot be modified • For each run of the tool, can only use one set of CFs and OFs for a particular geometry • All new organisms based on reptile or bird egg geometry • Need to re-run tool a number of times • Time consuming • Lots of copying and pasting involved

20. ERICA • Tool help file & D-ERICA • Again need to parameterise but facilitated by ‘Add organism’ wizard • Define geometry in tool based on x,y,z • Enter mass • Assign occupancy factors • Define concentration ratios • used default values • NOTE: Drigg data used in derivation of CRs in latest version of tool so changed back to pre-Drigg CRs (avoid self-validation)

21. Parameters for ERICA model run

22. Parameters for ERICA model run

23. Sr-90 activity concentrations

24. Cs-137 Activity concentration

25. Am-241 activity concentrations

26. Cs-137 Total unweighted dose rate

27. Am-241 Total unweighted dose rate

28. Perch Lake, Canada • EMRAS BWG scenario • Canadian shield lake • Received inputs of Sr-90, Co-60, Cs-137 and H-3 (amongst others) • AECL have activity concentration data for a range of biota in the lake • UoL and NRPA ran RESRAD-BIOTA as ‘informed users’(experienced with other tools but notRESRAD-BIOTA)

29. Valuable exercise • Applied by people involved with development of other tools but no previous experience of RESRAD-BIOTA • For model intercomparisons – important distinction between applications by developers and applications by ‘informed users’ • EMRAS has compared the ‘mathematics’ and started comparing applications (mainly by developers). There is a need to direct effort towards applications by users • Tool developers may access ‘inaccessible’ parts of tool • Tests tool user friendliness and accompanying documents • Realistic application • Begin to quantify a different aspect of tool uncertainty (the user)

30. Approach • RESRAD-BIOTA 1.22 beta version • Scenario required calculation of • Whole-body activity concentrations for key receptor species (Bq/kg FW) • Internal unweighted dose rates (µGy/h) • External dose rates (µGy/h) • NOTE: RESRAD-BIOTA only gives total dose • Application guided by • Tool + help • User guide (US DOE, 2004) • Some reference to technical reports (US DOE, 2002) • Web-based database (bioaccumulation factors and distribution coefficients)

31. The RESRAD-BIOTA Tool • The tool can be used for either terrestrial or aquatic (freshwater) assessments • Four generic organisms that have been parameterised: • Aquatic animal • Riparian animal • Terrestrial animal • Terrestrial plant • Assessments can be run to predict doses to these organisms • Level 3 includes ‘New organism’ wizard • possibility to create additional organisms based on one of the four generic organisms • allows calculations to be performed for specific species

33. Level 3 Assessment • Sediment data entry – dry weight or fresh weight • Not clear from tool, help or user guide • UoL assumed dry weight, NRPA assume fresh weight • First major decision and already the ‘informed users’ are taking different approaches! • Another example of where assessor needs clearer guidance • Predictions for specific biota so ‘New organism’ wizard used • When setting up new organisms need to parameterise • UoL decided to run allometrically for all organisms that were identified as particular species in the scenario and use BiVs for the rest • NRPA used BiVs only • UoL decision to run allometrically for everything (including a snail!) was probably not the best! However, no clear guidance as to extent of allometric functionality when using the tool • NRPA decision to run all with default BiVs may result in overly conservative predictions

34. Co-60 Modelled-to-measured ratio

35. Co-60 Modelled-to-measured ratio

36. Summary: What works? • All three tools do what they are designed to do • Predictions of measured data ‘aren’t bad’ • R&D 128 is generally conservative

37. Summary: What doesn’t work? • Guidance (in tools and supporting documentation) • R&D 128 • How do you calculate the ‘surface area:volume ratio’? • RESRAD-BIOTA • Do you enter sediment as fresh weight or dry weight? • When is it appropriate to run allometrically?

38. Summary: What extra may be required? • To facilitate the creation of new organisms, it would help if the R&D 128 spreadsheets could be set up to allow the same geometry to be run for a number of CF and OF combinations at the same time • To improve decision making it would be helpful to have the dose rate report from RESRAD-BIOTA showing internal and external dose rates as well as total dose rates

39. Summary: etc……! • There are differences in predictions due to ‘mathematics’ and assumptions behind tools • EMRAS BWG work helping to quantify and explain this • Effectively get handle on tool ‘error’ when compared to ‘real’ values • BUT…..of potentially greater significance in terms of error is that associated with the user • EMRAS BWG has focussed on intercomparison of tools by the tool developers • The one scenario where two tool developers attempted to run another organisation’s model revealed major differences in the approach and results obtained

40. Summary: etc……! • Valuable to investigate this aspect further • Take each tool in turn and have the developer and a number of ‘informed users’ run the tool for a particular scenario • Start to quantify the ‘error’ associated with the user • Help tool developers to identify areas of their tool and associated documentation that could be revised to provide clearer instruction to the assessor • Especially important for freely available tools that can be used by third parties • Hopefully this afternoon may start this process!!