General overview of processes, existing tritium modelling capabilities and WG7 activities Vlad Korolevych Environmental Technologies Branch Chalk River Laboratories Chalk River, Ontario Canada November 11, 2013, Vienna UNRESTRICTED / ILLIMITÉ
On WG7 accomplishments Aiken List (1990,1997) has been followed, updated and in many aspects implemented in the tritium transfer models suite: Germany France Japan Romania USA Canada UNRESTRICTED / ILLIMITÉ 2
Aiken List 1990 Workshop on Tritium, Aiken, SC,USA Raskob, W., and P. Barry. "Importance and variability in processes relevant to environmental tritium ingestion dose models." Journal of environmental radioactivity 36.2 (1997): 237-251. UNRESTRICTED / ILLIMITÉ UNRESTRICTED / ILLIMITÉ 3 3
On WG7 accomplishments In Canada COG: OBT SOTAR’ 08 Kim SB, PA Davis, RB Richardson, 2008. Contribution of OBT to total tritium dose. COG-07-3035 COG: OBT SOTAR’ 13 Kim SB, VY Korolevych, J Olfert, 2013 OBT SOTAR COG-13-3007 A few measurements of OBT are representative of the long term tritium accumulation in plants and human dose, but HTO are not. The magnitude of TFWT HTO fluctuations (comprised of basic small scale spatio-temporal variability , hydrologic and dendrologic variability across the landscape, variability caused by the known diurnal and seasonal cycles) makes the statistical significance of effects seen in medium-size datasets low. The need to monitor OBT UNRESTRICTED / ILLIMITÉ 4
Emerging issues • Requirement for ingestion dose accounted in accidental release assessments • The need for residual dose and long term effects account UNRESTRICTED / ILLIMITÉ 5
WG7 objectives • Guidance on development and application of environmental tritium transfer models based on the updated Aiken List • Inter-comparison of models for specific scenarios • Analysis of the TT in terrestrial ecosystems • Identification of knowledge gaps and assessment of their significance UNRESTRICTED / ILLIMITÉ 6
WG7 objectives (2) Provide guidance on: • Uptake of tritium by vegetated and non-vegetated soil • Transfer of HTO and the dynamics of HTO in the soil- plant-atmosphere complex • Re-emission of HTO from soil as a secondary source Attempt formalization of the guidance on : • Turnover of OBT in litter and soil UNRESTRICTED / ILLIMITÉ 7
1990 Workshop on Tritium, Aiken, SC,USA Raskob, W., and P. Barry. "Importance and variability in processes relevant to environmental tritium ingestion dose models." Journal of environmental radioactivity 36.2 (1997): 237-251. UNRESTRICTED / ILLIMITÉ 8
1990 Workshop on Tritium, Aiken, SC,USA Raskob, W., and P. Barry. "Importance and variability in processes relevant to environmental tritium ingestion dose models." Journal of environmental radioactivity 36.2 (1997): 237-251. UNRESTRICTED / ILLIMITÉ 9
WG7 objectives (3) • Develop path forward in the investigation of of outstanding issues • Extend Aiken List towards the following: – Wet deposition and re-emission (rain-time in canopy processes) – Formation of the organically bound tritium at night – Turnover of OBT in litter and soil (prioritize associated issues) UNRESTRICTED / ILLIMITÉ 10
Future prospects for WG7 • Advanced experimental datasets collection pertaining to the updated Aiken List • Deposition and re-emission * scenarios (dry and wet conditions, diurnal effects, seasonal effects) • OBT translocation in plants and soil ____ *) residual dose contribution UNRESTRICTED / ILLIMITÉ 11
Outstanding challenges UNRESTRICTED / ILLIMITÉ 12
Outstanding challenges (TBR’ 97) • Explicit modeling of proper parameterization of the uppermost soil layer (1-2 mm) interaction with atm HTO • Modelling of OBT fractionation and cycling (e.g. in soil) UNRESTRICTED / ILLIMITÉ 13
Outstanding challenges (3) • Explicit modeling of proper parameterization of the uppermost soil layer (1-2 mm) • Interaction with atm HTO • Modelling of OBT fractionation and cycling (e.g. in soil) UNRESTRICTED / ILLIMITÉ 14
Outstanding challenges (3) • Explicit modeling or proper parameterization of the uppermost soil layer (1-2 mm) interaction with atmoshere (rapid HTO uptake and re-emission) • Modelling of OBT fractionation and cycling (e.g. in soil) • Field-scale parameterization of tritium transfer UNRESTRICTED / ILLIMITÉ 15
Thank you UNRESTRICTED / ILLIMITÉ AECL - OFFICIAL USE ONLY / À USAGE EXCLUSIF - EACL 16
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