# Near-field atmospheric dispersion of a gas emitted from a hot source: a comparison between analytical modelling and in situ measurements

Mendez A.¹, Gée M.¹, Dupont S.², Laguionie P.¹

(1) Autorité de Sûreté Nucléaire et de Radioprotection (ASNR), PSE-ENV/STAAR/LERTA, 50130, Cherbourg-en-Cotentin, France

(2) INRAE, Bordeaux Sciences Agro, ISPA, F-33140 Villenave d'Ornon, France

INRAO

<figure><img src="image_1.png" /></figure>

orano

## 1 CONTEXT

<figure><img src="image_2.png" /></figure>

Incidents in nuclear facilities can lead to the emission of a radioactive plume dispersing into the atmosphere

<figure><img src="image_3.png" /></figure>

Unlike cold emissions, a plume rise occurs in the case of hot emissions

<figure><img src="image_4.png" /><figcaption>Cold emission</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Hot emission</figcaption></figure>

<figure><img src="image_6.png" /></figure>

Reliable estimation of radiological impact in the near field, where concentrations are highest, is critical. Two types of models can be used:

<figure><img src="image_7.png" /><figcaption>CFD models</figcaption></figure>

(6)

<figure><img src="image_8.png" /><figcaption>Analytical models</figcaption></figure>

(7)

Analytical models were initially developed for cold emissions
→ **How to take thermal plume rise into account?**

## 2 METHODOLOGY

### Experimental data acquisition

#### Four experimental campaigns

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Experimental implementation of a hot discharge using a propane flame generated by a burner

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Measurments of atmospheric conditions using a LiDAR and anemometers

<figure><img src="image_11.png" /></figure>

Establishment of a temperature profile using a mast

<figure><img src="image_12.png" /></figure>

Use of helium as a tracer gas

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Ground and airborne measurments of helium

<figure><img src="image_14.png" /><figcaption>COMPARISON</figcaption></figure>

### Analytical modelling: semi-empirical in 3 steps

<figure><img src="image_15.png" /><figcaption>1. Source characterization
   (T, u, r)</figcaption></figure>

Heskestad's formulas

<figure><img src="image_16.png" /></figure>

<figure><img src="image_17.png" /><figcaption>2. Transitional and final plume height
   ($\Delta h(x), \Delta h_f$)</figcaption></figure>

Briggs' model

<figure><img src="image_18.png" /></figure>

<figure><img src="image_19.png" /><figcaption>3. Passive dispersion
   ($C(x,y,z)$)</figcaption></figure>

Gaussian dispersion

<figure><img src="image_20.png" /></figure>

<footnote>(5) - Technical reference of the BUOYANT modelling system (model version 4.20), Juha Nikmo, (2019)</footnote>

<footnote>(7) - Dynamical dispersion in turbulent plumes, Matthew M. Scase (2018)</footnote>

<footnote>(1) - Volodymyr Zelesnky - X</footnote>

<footnote>(2) - Le séisme provoque un incendie dans une centrale nucléaire - France 24</footnote>

<footnote>(3) - Smokestack - Stock Photo © muha04 #1612138</footnote>

<footnote>(4) - Plume de fumée image stock. Image du sécurité, pétrole - 1981195</footnote>

<footnote>(6) - Plume de fumée image stock. Image du sécurité, pétrole - 1981195</footnote>