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Determination of the scavenging coefficients of gaseous and particulate chlorine 36 by rain

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Abstract

Chlorine 36 ( Half-life = 301,000 years) is a radionuclide with natural and anthropogenic origins that can be present in the effluents during decommissioning of nuclear power plants or during recycling of nuclear fuel (Orano La Hague). Once released into the atmosphere, chlorine 36 (gas and particles) can be transferred to the ground by dry and wet deposition. Because of its relatively high mobility in the geosphere and its high bioavailability in dissolved form, the fate of chlorine 36 is an issue for impact assessment. The wet deposition of gaseous and particulate chlorine 36 can be quantified from their respective scavenging coefficients. The scavenging coefficient reflects the amount of gas or particulate matter arriving on the ground via rainfall and allows a deposition flux to be determined. Thus, the objective of this study is to determine experimentally the scavenging coefficients of particulate and gaseous chlorine 36 by rain. For this purpose, an aerosol sampling was carried out with a low pressure impinger (0.02 - 10 µm) under the winds of the Orano recycling plant to determine the granulometric class of chlorine 36. Chlorine-36 concentrations were measured by accelerator mass spectrometry at ASTER-CEREGE (Accelerator for Earth Sciences, Environment, Risks, CEREGE, France). All samples were chemically prepared to extract the chlorides under the form of AgCl pellets. At IRSN La Hague technical platform (PTILH), located 2 km from Orano plant, an ELPI+ granulometer and a disdrometer were installed in order to determine the coefficients of particle removal by rain for all the granulometric classes. The determination of the scavenging coefficients requires the knowledge of the chlorine 36 content in the rainwater and in the atmosphere over a given period. For this purpose, a precipitation collector was installed at the IRSN La Hague technical platform (PTILH). The precipitation collector was equipped with a rain detector and opened only when rain was present. Near the precipitation collector, an AS3000 sampler trapped particulate chlorine on a composite teflon and fiberglass filter, and gaseous chlorine on an activated carbon cartridge. The average chlorine content measured in rainwater, in gaseous and particulate form, is respectively 3,4.107 at/l, 1,6.105 at/m3, 4.104 at/m3. Once the granulometric fraction of chlorine 36 will be acquired, the corresponding scavenging coefficient will be calculated from the ELPI+ and disdrometer data. As for the scavenging coefficient of gaseous chlorine 36, it will be determined from the amount of particulate chlorine 36 drawn down calculated from its scavenging coefficient in comparison with the amount of chlorine 36 present in rainwater and in the atmospheric concentrations of gaseous chlorine 36.
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Dates and versions

irsn-03875447 , version 1 (28-11-2022)

Identifiers

  • HAL Id : irsn-03875447 , version 1

Cite

Deo Gratias Kily Sourabie, Didier Hebert, L. Benedetti, E. Vitorge, B. Lourino Cabana, et al.. Determination of the scavenging coefficients of gaseous and particulate chlorine 36 by rain. 5th International Conference on Radioecology & Environmental Radioactivity, ICRER, Sep 2022, Oslo, Norway. ⟨irsn-03875447⟩
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