MODARIA WG8 Biota modelling: Further development of transfer and exposure models and application to scenarios
Objectives ........ to improve Member States’ assessment capabilities for protection of the environment by comparing, improving and validating models being used or developed, for biota dose assessment as part of the regulatory process of licensing and compliance monitoring of authorised releases of radionuclides.
Why? • Revised BSS – assessment of radiological environmental impact • Revised ICRP Recommendations & RAP Framework developments • Available models are relatively new and being developed • Various national initiatives
What did EMRAS I & II WG’s achieve? • Demonstrated that the dosimetric components (DCC) of commonly used models give generally comparable estimates of dose when assume homogenous distribution in organism and media. • But not the transfer components – predictions of organisms equilibrium activity concentrations vary by orders of magnitude
Scenario applications
Perch Lake (Chalk River Canada) • Models validated using laboratory data performed relatively poorly • Models using water chemistry in transfer prediction performed relatively well • Predictions for mammals/heptofaua poor
Perch Lake (Chalk River Canada) • Models validated using laboratory data performed relatively poorly • Models using water chemistry in transfer prediction performed relatively well • Predictions for mammals/heptofaua poor
Chernobyl Exclusion Zone • Orders of magnitude variation in predicted organism concentrations • External dose predictions reasonable (TLDs on small mammals) • Importance of correct parametersation of diet in foodchain models
Chernobyl Exclusion Zone • Orders of magnitude variation in predicted organism concentrations • External dose predictions reasonable (TLDs on small mammals) • Importance of correct parametersation of diet in foodchain models
Little Forest Burial Ground • How to address ‘unusual’ exposure scenarios (tree growing on waste trenches) • Progeny assumptions
Beaverlodge Lake • Progeny assumptions • Data gaps • Recommendations on monitoring programmes (organisms and radionuclides) • Heterogeneous media distribution • Uncertainty of Kd • ‘Consensus approach’
‘Wetland’ • Perhaps surprisingly little variation in organism activity concs (draft wildlife TRS available) • Assumptions of diet source 14 C (Bq/kg f.w.) Erica (eriss/ARPANSA ) (aquatic or terrestrial) 100000 Erica (ANSTO) • External dose - correction (or Erica (CEH) Erica (SCK) 10000 RESRAD-Biota not) of soil moisture content K-Biota • First model-data comparison of Measured 1000 C-14 specific activity approaches 100 for wildlife 10 1 Trees Small Peat Insects Frogs Snakes Rodents plants moss
‘Benefits’ • Realisation of need to compile transfer parameters (CR) for wildlife (EMRAS II WG) – used for draft IAEA TRS on wildlife CR values and ICRP-114 • Various model improvements/identification of limitations • Training
MODARIA – potential activities • Scenario applications – those to date relatively simplistic – concentrated on model-data comparisons and not application to assessments – How integrate with human assessments
MODARIA – potential activities • Training – best practice guidance (linked to scenarios) • Non-equilibrium conditions (EMRAS II review) – Identify scenarios (source terms/radionuclides) where dynamic models may be required – Scenarios testing using existing models/adapt human assessment models (compare to equilibrium assumptions) – How interpret results?
MODARIA – potential activities • ‘Dosimetry’ – Heterogeneous distribution in environment – Heterogeneous distribution in organism (other on-going activities?) – Plant geometetries
Interactions with other WG • Integration human-wildlife assessment • Effects group (interpretation of dynamic models, heterogeneous distribution activities) • Developments for ‘Radioecology data’ WG (inc. application of outputs) feedback limitations/scenario applications • Scenario sharing (marine, legacy, routine releases)
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