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David Copplestone (University of Stirling). Whats the issue? Obtaining air concentrations for noble gases Estimating doses to wildlife from noble gases.

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Presentation on theme: "David Copplestone (University of Stirling). Whats the issue? Obtaining air concentrations for noble gases Estimating doses to wildlife from noble gases."— Presentation transcript:

1 David Copplestone (University of Stirling)

2 Whats the issue? Obtaining air concentrations for noble gases Estimating doses to wildlife from noble gases

3 Nuclear power plants ~ 85% of the total activity released is in the form of noble gases (Ar-41, Kr-85) Except for one model, none of the available tools estimate doses to wildlife from noble gases Most analogue radionuclides that could be used will massively over predict the dose rate

4 Initially, during screening, used Cs-137 as analogue Essentially any release containing Ar-41 or Kr-85 exceeded the screening value Very conservative Lead to refining of modelling approach

5 Various tools for atmospheric modelling (see Jordis presentation) Essentially need to predict the air concentration at the point of interest (i.e. where biota are) following release Simple models likely to be sufficient (dose rates are typically very small) SRS-19 or R91 should be adequate

6 Need the distance to receptor Release height Wind speed Time wind blows in the direction of the receptor Duration of discharge Buildings nearby? Deposition coefficients (wet and dry) Etc.

7 Noble gases have a small but finite solubility in water and body fluids Dose contribution is negligible (CRs therefore set to 0) Noble gases are not deposited to soil (so no plant uptake etc) Will be exchange within the air pore volume of surface soil (but small component) So assumes pore air concentration = ground level air concentration Other factors as default in dose assessment tool (e.g. occupancy factors)

8 Initially produced back in 2001 Updated a couple of times No further development work (superseded by ERICA Tool) Freely available (documented) spreadsheet model for coastal, freshwater and terrestrial ecosystems Limited radionuclide list and transfer parameter database

9 Ensure macros are enabled in Excel

10 Enter 1 Bq/m3 in each Ar-41, Kr-85

11 Press F1 to bring up the control panel

12

13 For similar reference organisms then it is possible to add the dose rate from Ar-41 and Kr-85 to the dose rates predicted by other tools (gives total dose rate) Generally negligible dose rates but addresses perception issues and is more realistic than using analogues


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