Predicting gaseous pollutant dispersion around a workplace.

Predicting the space-time evolution of a gaseous or particulate pollutant concentration in a ventilated room where a process operation is performed is imperative in hazardous activities, such as chemical or nuclear ones. This study presents a prediction of the space-time evolution of airborne pollutant dispersion following the accidental rupture of a containment enclosure (fume cupboard, glove box, pressurized gas duct, etc.). The final model is written as correlations inspired by the free turbulent jet theory, giving the space-time evolution of a pollutant concentration c (x,y,z,t) that has been formulated as a correlated function of various parameters: leak geometry (slot or round opening), emission type (continuous or transient), emission duration and initial emission velocity. These correlations are based on gas tracing experiments and on multidimensional simulations using computational fluid dynamics (CFD) tools. An instrumented experimental facility was used to simulate pressurized gas industrial failure, and the measurements performed gave the real-time evolution of a tracer gas concentration. Transient leak simulations were run in parallel with a CFD code. Comparisons between experimental and numerical results largely agree. A semiempirical model was built using a methodical parametric study of all the simulation results. This model is easy to use in safety evaluations of radioactive material containment and radiological protection inside nuclear facilities and for evaluating toxic gaseous compounds in the chemical industry.