The CHIP programme aims to better quantify the amount of iodine that may be released (source term) during a core meltdown accident in a nuclear reactor. The "analytical" line studies the chemical mechanisms involved in the formation of iodine species for homogeneous gas-phase reactions of quaternary systems (I, O, H) by means of pre-mixed flame configurations.
This programme will make it possible to:
- Ascertain basic kinetic data for mixtures containing iodine, hydrogen, and steam;
- Supplement the databases (chemical speciation of gaseous iodine species and basic kinetic data) needed to model the behaviour of radioactive fission products in the primary cooling system of a pressurised water reactor (ASTEC software developed by IRSN/DPAM).
Experimental device and test condition
The device includes:
- Several reagent feed pipes (iodine from a hydrogen iodine (HI) cylinder, hydrogen/ steam generator, O2 combustive agent from a gas cylinder, other reagents such as Cs, Cd, etc.);
- A burner supplied with a premixed gas mixture ensuring the formation of a 1D flame in which the reagents can react;
- A low-pressure combustion chamber;
- On-line gas sampling systems;
- Analytical devices for identifying and quantifying the species under investigation (molecules, atoms and radicals).
This device is used to determine quantitative profiles of change in chemical species as a function of the temperature profile in the flame. The experimental data are used to develop complex reaction mechanisms. The experimental parameters are the temperature (500 - 2,000 K) and the concentration ratios of the chemical reagents. They are representative of the different ranges covered under accident conditions in the primary cooling system of a pressurised water reactor.