The Laboratory for the Study of Chemical Kinetics, Combustion and Reactivity (C3R) is a joint research laboratory established by the IRSN, the CNRS and the University of Lille 1 Science and Technology.
Context and research themes
Founded in 2009, the C3R constitutes an on-going collaboration between the IRSN, represented by the Department for the Study and Experimental Research into Chemistry and Fire (SERCI), and the Physics and Chemistry of Combustion and Atmospheric Processes Laboratory (PC2A/UMR 8522), a joint unit set up by the CNRS and the University of Lille 1. Research resources, in the form of equipment, personnel and finance, have all be provided jointly by the two organisations, together with their extensive expertise and knowledge.
The C3R employs a total of 29 staff, of whom 14 are permanent employees. The contribution from PC2A is three full-time equivalent staff and 10 permanent employees, while the IRSN has provided 2.1 full time equivalent staff 3 PhD students, and 2 post-docs).
The joint directors of the C3R are Laurent Cantrel from the IRSN and Laurent Gasnot from PC2A, alternating in the posts of director and co-director.
The research carried out by the C3R falls into four main topic areas:
- Chemical kinetics in the gas phase (iodine, ruthenium, etc.);
- Heterogeneous chemistry: The chemical reactivity of aerosols and surface interactions;
- Combustion chemistry and soot formation;
Two complementary approaches have been adopted in order to understand and model the complex phenomena that occur during a core melt-down accident, conditions that are difficult to reproduce in a laboratory:
- An experimental approach using a number of different experimental facilities: Small-scale experimental facilities, such as a laminar flat flame burner and a falling liquid film reactor, coupled with state-of-the-art analytical techniques, including laser diagnostics based on laser-induced fluorescence and cavity ring-down spectroscopy, and intermediate scale reactors such as the Chip-LP experimental facility dedicated to the study of the reactivity of iodine at high temperature in the presence of particles.
These advanced measurement techniques benefit from a strong contribution in the field of metrology to the development and implementation of analytical techniques, especially the optical expertise made available by the national optical metrology platform (MEOL) in Lille.
- A theoretical approach based on quantum chemistry and statistical simulations of classical molecular mechanics with the aim of interpreting experimental data, developing reaction mechanisms, identifying system effects, and the extrapolation of results beyond the experimental conditions.
In understanding and modelling soot formation, priority has initially been given to an experimental approach in order to build up a database of experimental results. The technique of in situ laser-induced incandescence (LII) will be used to characterise the soot, while the PAHs will be measured by means of mass spectrometry, chromatography and laser-induced fluorescence (LIF).
The chemistry of fission products during a core melt-down accident
A better understanding of the reactivity of the radioelements released during a core melt-down accident in an nuclear reactor, especially those that are the most radiotoxic such as iodine and ruthenium, will facilitate progress in understanding the mechanisms of the chemical reactions in which they are involved and which influence their behaviour. The ultimate aim is a more accurate prediction of the source term, i.e. the discharge of any of these radioelements into the environment.
One important task is to improve the modelling of the transport of iodine in the reactor coolant system. The fluid in which the iodine is transported is a complex oxidising or reducing medium containing a large number of chemical elements in the form of aerosols, vapour and gas. The temperature of this medium may vary dramatically as it circulates through the reactor coolant system. The improvement of these models, especially by taking into account the kinetic parameters of the chemical reactions taking place in the gas phase, should result in a better speciation of the iodine in the vicinity of the breach in terms of both the gas/aerosol distribution and the chemical compounds formed.
This work will eventually be incorporated into the Astec (Accident Source Term Evaluation Code) simulation software used to evaluate the discharge of fission products in the event of an accident.
The physics and chemistry of fire
The C3R is also making a contribution to upstream research relating to fire in the type of confined and ventilated environment typical of nuclear installations. This work consists of modelling the formation of combustion products such as polycyclic aromatic hydrocarbons (PAH), which act as precursors for soot formation. This soot affects the combustion kinetics, and may block the filters in the ventilation systems, cause malfunctions in electrical equipment, and hinder the operations of the fire service. The objectives of this research are firstly to obtain a better characterisation of the formation of this soot from an experimental point of view, and then to develop and validate reaction mechanisms that may be used to predict this formation.
The modelling of the behaviour of soot in fires in a confined environment is a shared research objective with the Laboratory for the Study of Fires in a Confined Environment (Etic), a laboratory founded jointly by the IRSN, the CNRS and the Universities of Aix Marseille I and II. This work will eventually be incorporated into the Isis fire simulation for safety software in order to evaluate the consequences of a fire in a confined environment.
Topics to be studied in the period 2010-2013
- Determination of the thermo-kinetic parameters and the development of reaction mechanisms for modelling the chemical reactivity of iodine in a reactor coolant system.
- Chemical reactivity of aerosols (especially Csl).
- Physical and chemical properties of the oxides and nitroxides of iodine.
- Experimental characterisation of the formation of soot particles.
- Theoretical chemical modelling of surface-particle interactions.
Facilities and techniques
- Available theoretical chemistry software (Gaussian03 and Molcas 7.0) for the quantum modelling of molecules and reactions in the gas phase with access to the molecular properties and the thermo-kinetic parameters of the elementary reactions.
- Development of software to meet specific requirements, including the molecular dynamics software package SPyDERS, with one of the aims being the calculation of the volatility of solvated species.
- Experimental facilities dedicated to homogeneous and heterogeneous (particle-gas) chemistry.
- A range of high-performance analytical techniques, including chromatographic approaches, spectroscopic methods, and laser diagnostics in association with MEOL.