Nuclear Energy for New Europe 2009

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No: 408

Conference: Nuclear Energy for New Europe 2009

Title: Speciation of Aerosols Transported in the Primary Circuit: A Comparative Study

Theme: Severe Accidents

Author(s): Marion Lacoue-Negre, Herve Mutelle, Frederic Cousin, Sophie Sobanska, Claude Bremard

Contact : Marion Lacoue-Negre

E-mail: marion.lacoue-negre@irsn.fr

Address: IRSN/DPAM/SERCI/L2EC
13108 Saint Paul lez Durance

Country: France

In case of a severe accident in a nuclear power plant, the quantity of iodine that can be released into the environment is a major issue. The simulations performed with computer codes can not account totally for the behaviour of iodine observed in the PHEBUS-FP tests. One approach to improve the models aims to determine the molecular composition of the particles formed in the primary circuit. An experimental program on this subject is currently in progress at IRSN in collaboration with the CNRS/LASIR. In this work, we investigate the interactions between species that can directly affect iodine chemistry, especially Mo and Cs compounds in the primary circuit.
The experimental line, named GAEC (Generation of AErosols in the primary Circuit), has been developed to produce aerosols representative of those which would be released into the primary circuit in case of a severe accident. Vaporised species in the I-Cs-Mo system are mixed with a carrier gas consisting of argon and steam at temperatures close to 1600°C in a high temperature furnace. Temperature quickly decreases to reach 150°C. At the end of the GAEC line, condensed species are collected on a quartz fiber filter with a poral grade of 1.6 µm and gases are trapped inside bubbling bottles containing an alkaline solution. Chemical species collected on the filter are analysed by complementary analytical techniques: microscopic and imaging Raman scattering for molecular analysis, Environmental Scanning Electron Microscopy (ESEM) and Scanning Electron Microscope coupled with a Wavelength Dispersive Spectrometer (SEM-WDS) for elemental analysis. Trapped species inside bottles are analysed by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS).
This paper presents GAEC experimental results and compares them to predictive results obtained with SOPHAEROS code. This module of the integral code ASTEC predicts transport in the reactor coolant system of vapours and aerosols formed by condensation of materials released from the degraded core. SOPHAEROS calculates aerosol size distribution and chemical speciation of aerosol and vapour phases. The basis of the chemical modelling is calculation of thermodynamic chemical equilibrium.
Preliminary results obtained by simultaneous vaporisation of CsI and MoO3 show the formation of caesium molybdates CsxMoyOz unpredicted by SOPHAEROS calculation.

No:	408
Conference:	Nuclear Energy for New Europe 2009
Title:	Speciation of Aerosols Transported in the Primary Circuit: A Comparative Study
Theme:	Severe Accidents
Author(s):	Marion Lacoue-Negre, Herve Mutelle, Frederic Cousin, Sophie Sobanska, Claude Bremard
Contact :	Marion Lacoue-Negre
E-mail:	marion.lacoue-negre@irsn.fr
Address:	IRSN/DPAM/SERCI/L2EC 13108 Saint Paul lez Durance
Country:	France

In case of a severe accident in a nuclear power plant, the quantity of iodine that can be released into the environment is a major issue. The simulations performed with computer codes can not account totally for the behaviour of iodine observed in the PHEBUS-FP tests. One approach to improve the models aims to determine the molecular composition of the particles formed in the primary circuit. An experimental program on this subject is currently in progress at IRSN in collaboration with the CNRS/LASIR. In this work, we investigate the interactions between species that can directly affect iodine chemistry, especially Mo and Cs compounds in the primary circuit. The experimental line, named GAEC (Generation of AErosols in the primary Circuit), has been developed to produce aerosols representative of those which would be released into the primary circuit in case of a severe accident. Vaporised species in the I-Cs-Mo system are mixed with a carrier gas consisting of argon and steam at temperatures close to 1600°C in a high temperature furnace. Temperature quickly decreases to reach 150°C. At the end of the GAEC line, condensed species are collected on a quartz fiber filter with a poral grade of 1.6 µm and gases are trapped inside bubbling bottles containing an alkaline solution. Chemical species collected on the filter are analysed by complementary analytical techniques: microscopic and imaging Raman scattering for molecular analysis, Environmental Scanning Electron Microscopy (ESEM) and Scanning Electron Microscope coupled with a Wavelength Dispersive Spectrometer (SEM-WDS) for elemental analysis. Trapped species inside bottles are analysed by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). This paper presents GAEC experimental results and compares them to predictive results obtained with SOPHAEROS code. This module of the integral code ASTEC predicts transport in the reactor coolant system of vapours and aerosols formed by condensation of materials released from the degraded core. SOPHAEROS calculates aerosol size distribution and chemical speciation of aerosol and vapour phases. The basis of the chemical modelling is calculation of thermodynamic chemical equilibrium. Preliminary results obtained by simultaneous vaporisation of CsI and MoO3 show the formation of caesium molybdates CsxMoyOz unpredicted by SOPHAEROS calculation.