Outdoor exposure due to long-range atmospheric transport of radon can it be assessed by modelling?

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Outdoor exposure due to long-range atmospheric transport of radon can it be assessed by modelling?

Denis Quelo, Arnaud Querel, Thierry Doursout

To cite this version:

Denis Quelo, Arnaud Querel, Thierry Doursout. Outdoor exposure due to long-range atmospheric transport of radon can it be assessed by modelling?. 19th international conference on harmonisa- tion within atmospheric dispersion modelling for regulatory purposes, HARMO, Jun 2019, BRUGES, Belgium. 2019. �hal-02635629�

Outdoor exposure due to long-range atmospheric transport of radon can it be assessed by modelling?

Denis QUÉLO1, Arnaud QUÉREL1, Thierry DOURSOUT

11nstitute for Radiological Protection and Nuclear Safety (IRSN), PSE-SANTE, SESUC, BMCA, Fontenay-Aux-Roses, France

Significant Radon-222 air concentration at one location is the combination of a potentially high local source - within few kilometers - and a long- distance origin - dozens or hundreds of kilometers.

A local source can be estimated by modelling or measuring the ground exhalation rate. A distant origin is far more problematic to determine since it involves all the atmospheric processes and many potential exhalation sites. Therefore, the simulation of Radon-222 air concentrations must be made at regional or continental scale. We built a Radon-222 atmospheric transport modelling calculation chain, from input data to model-to-measurement

comparisons.

Case study: atmospheric transport of radon

® Précipitation

© Exhalation of

radon(gas)

Radon daughters (particles)

214 210

y Po ^{160 IJS y} Po

214 A ^{84 210} A ⁸⁴

Bi ^{/ P a|}

*pN

02 ^{/ P °4}

83 210 83 206

20 m Pb ^{5 d} Pb

82 ^{22 y} 82

Increase of dose rate

0)

QO

© Fast

radioactive decay of daughters

Peak of dose

rate time

© Deposit of

daughters © Radiation Monitoring station

Context

In the event of an incident or accident involving radioactive materials, IRSN provides guidance to public authorities on the technical, public health and medical actions to be taken to

protect the population and the environment.

Radon-222 is a progeny of U-238, naturally found in the Earth’s crust. After diffusing out of the soil, it reaches the atmosphere. As a noble gas, it does not interact with other gas or aerosol particles.

Transported by the atmosphere, it can be breathed. Its disintegration inside the lung can damage the cells, increasing the risk of cancer. Radon-222 is therefore a major public health issue in some regions.

Several times a year, alarms of this emergency monitoring network are triggered: these gamma dose rate peaks occurred during rainfall events because radon progenies concentrate in rain drops and fall down to the ground.

Source term

Output

Radon peak forecast, model-to-measurement

comparisons

Observations

Although these peaks are safe for the population or environment, it is necessary to discriminate whether it comes from the natural radioactivity or if an accidental release of

radioactive materials happened.

METEO FRANCE

Met data

At:1H ; Ax=Ay=0.1°

»10km

Atmospheric transport + Dose rate assessment:

Long range transport model of the operational response platform C3X

The monitoring network Téléray in France:

Hundreds of

gamma dose rate monitoring

stations recording data each ten

minutes all year round.

The model is validated with observed gamma dose rate .. ... and radionuclides air concentrations

Gamma dose rate simulated and observed are compared. The simulation is satisfying when the source term, the winds and the precipitations are well- performing.

Observed gamma dose is well reproduced. Statistics have to be generated to qualify our gamma-dose results, and to qualify the model itself.

The mean air concentration of the Rn-222 and daughters is well correlated with the observation, until the Bi-210.

Air concentrations (Bq.m-3)

50

40

30 _UQJ Ü3

OJ

20 -ë

eu

10

50

40

LHC

30

D

T3

X3

%

■OJ

10

Local time

Bi-210 is generated very slowly and comes in a large part from volcanoes

Outdoor radon exposure

Outdoor exposure to radon: the role of long-range atmospheric transport?

When breathed, the radon-222 disintegrated inside the lung can damage the cells, increasing the risk of cancer.

Radon-222 air concentration at one location is the combination of a potentially high local source - within few

kilometres - and probably a long-distance origin - dozens or hundreds of kilometres. Conclusion

Variability of Rn-222 air concentration at the ground-level for several times during August, 2107 This preliminary study shows the feasibility of modelling atmospheric

radon at regional scale.

Outputs for IRSN:

•Forecast of dose rate peaks.

•Improve the atmospheric transport model (wet deposition modelling).

•Atmospheric radon exposure by inhalation.

H19-107 HARMO 19th 3-6 June 2019, Bruges, Belgium