Vlad Korolevych

Canadian Nuclear Laboratories

Chalk River, K0J 1J0, Ontario, Canada

E-mail: vlad.korolevych@cnl.ca

Séverine Le Dizès-Maurel

IRS[N] PRP-ENV/SERIS/LM2E

CEN Cadarache bât 159 13115 St Paul-Lez-Durance, France

Courriel : severine.ledizes@irsn.fr

MODARIA TM-III, November 10, 2014, Vienna

MODARIA Working Group 7 (WG7): Harmonization and intercomparison of models

for accidental tritium releases

Conclusions of Interim Meeting of the WG7 in

Cherbourg, France, 10-13 June, 2014 and

WG7 goals for MODARIA TM-III

Cherbourg University area

The Lab

Main Conclusions of the WG7 Interim

meeting in Cherbourg: June 10-13, 2014

Name Affiliation

Mr J. WALKER AIEA - Austria

Ms N. KWAMENA CNSC - Canada

Mr H. NAGAI JAEA - Japan

Mr M. OTA JAEN - Japan

Ms M. CZERNICZYNIEC ARN - Argentina

Mr L. PATRYL CEA - France

Ms C. AULAGNIER EDF - France

Mr D. MARO IRSN - France

Ms S. LE DIZES-MAUREL IRSN - France

Mr V. DOLIN IEG – Kiev / Ukraine

Mr J. Welling PHE - United Kingdom

� Meeting participants

� WG7 Objectives

� Guidance on development and application of environmental

tritium transfer models based on the updated Aiken list

� Analysis of the tritium transfer in terrestrial ecosystems

� Identification of knowledge gaps and assessment of their

significance

� Inter-comparison of models on specific scenarios

� WG7 Objectives

� Guidance on development and application of environmental

tritium transfer models based on the updated Aiken list

� Analysis of the tritium transfer in terrestrial ecosystems

� Identification of knowledge gaps and assessment of their

significance

� Inter-comparison of models on specific scenarios

� CRL’2008 Scenario (Canada): blind test model results will be presented and

discussed

– HTO in air (intermittent routine release)

– HTO in soil and vegetation, OBT in vegetation and fruit

� IRSN’2013 Scenario (France): to be discussed (+ visit of the experimental site)

– HT and HTO in air, CO2 fluxes, soil water dynamics (lysimeters)

– HTO and OBT in vegetation and soil

� CNSC’2012 Scenario (Canada): distributed to participants when ready.

– HT and HTO in air

– HTO in vegetation and soil and OBT in soil

� Models Inter-comparison (3 scenarios)

� CRL’2008 Scenario (Canada): blind test model results will be presented and

discussed

– HTO in air (intermittent routine release)

– HTO in soil and vegetation, OBT in vegetation and fruit

� IRSN’2013 Scenario (France): to be discussed (+ visit of the experimental site)

– HT and HTO in air, CO2 fluxes, soil water dynamics (lysimeters)

– HTO and OBT in vegetation and soil

� CNSC’2012 Scenario (Canada): distributed to participants when ready.

– HT and HTO in air

– HTO in vegetation and soil and OBT in soil

� Models Inter-comparison (3 scenarios)

Data type Variable Units Time period Frequency

Meteorological Incoming Shortwave

Radiation

W/m2 15/4/08 - 08/12/08 30 mins

Incoming Longwave

Radiation

W/m2 15/4/08 - 08/12/08 30 mins

Precipitation rate mm/s 15/4/08 - 08/12/08 30 mins

Temperature °C 15/4/08 - 08/12/08 30 mins

Wind Speed m/s 15/4/08 - 08/12/08 30 mins

Pressure Pa 15/4/08 - 08/12/08 30 mins

Specific Humidity Kg/kg 15/4/08 - 08/12/08 30 mins

� Summary of AECL data from CRL’2008 scenario (1)

Data type Variable Units Time period Frequency

Source term Atmospheric HTO

activity*

Bq/L 15/4/08 - 08/12/08 30 mins (reconstr.)

Rain HTO

concentration**

Bq/L 15/4/08 - 08/12/08 Monthly

30 mins (reconstr.)

Tritium activity

at the site

Soil HTO at 0-35 cm Bq/L 30/7/08 – 23/10/08 On specific dates

HTO in soil and

vegetation

Bq/L 30/6/08 – 20/10/08 On specific dates

OBT*** in vegetation

and fruit

Bq/L 30/6/08 – 20/10/08 On specific dates

* The atmospheric HTO activity is modelled based on Ar-41 high-frequency monitoring and atm dispersion

modelling of HTO using the monitored source term. The reconstruction was QA checked by comparison against

a number of half-hourly HTO measurements plus weekly HTO monitoring results (both HTO samplers are

located in the immediate vicinity of the garden plot).

** The rain was measured monthly at ~7 km from the stack. We can deploy washout ratio approach for rain

deposition in CRL Scenario with the washout coeff 0.2 (Rain_HTO_conc in Bq/L =0.2* atm._moisture_HTO in

Bq/L). This is a bit unconventional, but the washout=0.2 provides reasonable fit to monthly observations of rain

HTO concentration at the monitoring site at ~7km.

*** Total not rinsed OBT (i.e. non-exch +exchOBT)

� Summary of AECL data from CRL’2008 scenario (2)

� SOLVEG and TOCATTA-χ predict quite well the evolution of TFWT in plant leaves: good timing of

the predicted HTO pulses as compared to the observations

� Unexplained discrepancy between modelled OBT and measurements (measured OBT/TFWT ~ 5 vs

predicted OBT/TFWT ~ 1)

� Still unexplained averaged high OBT/HTO ratio observed in plants (in CRL scenario)

Possible explanations : red = must be investigated in first / blue = investigation is scheduled

� Samples preparation?

� Measurements representative enough? (exch- and non-exch OBT…) ?

� Reconstructed HTO in rain is validated?

� Exhaustivity of source term?

� Specificity of reactors (PWR : France / Japan - BWR : Japan - PHWR : Argentina / Canada) ?

� Recomposition of HTO / HT with other compounds released by the plant to produce tritiated species ?

� Cation exchange capacity in the soil-plant system ?

� Isotopic fractionation ? (to be addressed by hydroponic culture by 2016)

� Formation of OBT at night?

� Is there a direct pathway between HTO in air and plant OBT that the models have ignored?

� …

� Conclusions about the inter-comparison exercise(CRL’2008 scenario)

� But strong similarities between SOLVEG and TOCATTA-χ

Experimental data needs

� Air (and rain) HTO / HT / other compounds above the site at an hourly

time-step

� Plant growth information : LAI, density, plant height, roots depth (option)

� Soils information : porosity, granulometry, texture (% of clay)

� All meteorological data (air T, humidity, long-wave solar radiation

(upwind and downwind if it is possible) / PAR, wind speed, precipitations

at a hourly time-step)

Planned model enhancements

� Should we wait for the three scenarios (CRL, CCSN,

IRSN) to be implemented in the models to identify any

model enhancements about OBT ?…

� …

Planned future experiments

� Specific experiments should be carried out for studying the following

processes:

� isotopic fractionation of tritium in plants,

� formation of OBT during night time…

� …

These two topics will be adressed by IRSN in 2015-2016 based on hydroponic

cultures

� CRL’2008 Scenario (Canada): blind test model results will be presented and

discussed

– HTO in air (intermittent routine release)

– HTO in soil and vegetation, OBT in vegetation and fruit

� IRSN’2013 Scenario (France): to be discussed (+ visit of the experimental site)

– HT and HTO in air, CO2 fluxes, soil water dynamics (lysimeters)

– HTO and OBT in vegetation and soil

� CNSC’2012 Scenario (Canada): distributed to participants when ready.

– HT and HTO in air

– HTO in vegetation and soil and OBT in soil

� Models Inter-comparison (3 scenarios)

� CRL’2008 Scenario (Canada): blind test model results will be presented and

discussed

– HTO in air (intermittent routine release)

– HTO in soil and vegetation, OBT in vegetation and fruit

� IRSN’2013 Scenario (France): to be discussed (+ visit of the experimental site)

– HT and HTO in air, CO2 fluxes, soil water dynamics (lysimeters)

– HTO and OBT in vegetation and soil

� CNSC’2012 Scenario (Canada): distributed to participants when ready.

– HT and HTO in air

– HTO in vegetation and soil and OBT in soil

� Models Inter-comparison (3 scenarios)

� WG7 Objectives

� Guidance on development and application of environmental

tritium transfer models based on the updated Aiken list

� Analysis of the tritium transfer in terrestrial ecosystems

� Identification of knowledge gaps and assessment of their

significance

� Inter-comparison of models on specific scenarios

� 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.

• Identify key processes and develop path forward:

– Explicit modeling of proper parameterization of the uppermost soil

layer (1-2 mm) interaction with atm. HTO

– Wet deposition and re-emission (rain-time in-canopy processes);

Include dewfall processes and dew-driven HTO deposition

• Extend Aiken List:

– Formation of OBT in dark reactions: interaction of so-formed OBT

with HTO deposited onto leaves:

o During rainy weather

o At night

– Turnover of OBT in litter abd soil (prioritize issues)

� WG7 scope of work

� WG7 scope of work (continued)

• Provide guidance on tritium land-atmosphere transfer:

– Foliar uptake and re-emission as an integral part of soil-plant-

atmosphere complex

– Turnover of OBT in litter and soil

– Parameterization of vegetated and non-vegetated soil

o Uptake of HTO

o Re-emission of HTO

• Discuss identified knowledge gaps and future experiments

• Discuss regulatory prospective for WG7 work

Documented efforts and plansProcesses Participants

/ Affiliation

Deadline

Uptake of tritium by vegetated and non-vegetated soils

Vladimir KorolevychAECL-CRL

11/2014

Re-emission of tritium (HTO) from soils as asecondary source

Nana-OwusuaKwamena CCSN

11/2014

Dynamics of tritium transfer (HTO) into plant-atmosphere system : foliar uptake and re-emission of HTO

Séverine Le Dizès-Maurel, Céline AulagnierIRSN / EDF

11/2014

Formation of Organically Bound Tritium (OBT)at night, linked to the respiration process

Ota MasakazuJAEA

11/2014

Turnover of Organically Bound Tritium (OBT)in litter and soils

Ota MasakazuJAEA

11/2014

Chemistry and microbiological processes insoils included HT oxydation

Mariela CzerniczyniecARN

?

Thank you