Unsteady aspects of sodium-water-air reaction
Résumé
One important issue for the Sodium Fast Reactor (SFR) concept is the reactivity of metallic sodium and its exothermal reaction with water. In particular during equipments washing operations, sodium needs to be firstly converted ('destroyed') into non reactive species via a chemical reaction with water. Today, such operations are performed in tanks that confine the system and mitigate the consequences of any possible abnormal condition. Some data were obtained from experiments run by the French Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA) and were used as a basis for modelling. Among the principal phenomena identified so far are rapid water vaporization, hydrogen emission and explosion in air. High explosive-like pressure waves are generated from which sodium fragmentation and dispersion in water may ensue increasing the overall reactivity. It is extremely important to clarify the phenomenology to allow realistic extrapolation to full scale plants. A state of the art is proposed in this paper, starting from available experimental data and present perception of the physics. A comparison with present modelling strategy is also performed, underlining the necessity to improve a different and more physical approach aimed to well represent dynamic aspects of reaction.