A Study of the Influence of Wind on the Containment of Pollutants inside Industrial Buildings

Industrial buildings, as in the nuclear industry, are equipped with ventilation systems, the main role of which is to ensure pollutant containment inside the facility during normal, damaged or accidental situations. To do this, the ventilation system is designed to maintain rooms at lower pressure with respect to the outside environment. The air, taken from the outside, thus flows from the rooms with the lowest contamination risk to the rooms with the highest contamination risk, before being filtered and released into the atmosphere. Wind creates pressure fields along the external envelope and communicating openings of the facility, which can modify internal airflows, notably leakage flow rates of rooms. In order to study the combined effects of wind and mechanical ventilation, a methodology for carrying out reduced-scale experiments to predict isothermal flows, in steady and transient states, has been developed and then numerically and experimentally validated. The application of this methodology to two standard nuclear configurations has led to experiments performed in the Jules Verne climatic wind tunnel of the CSTB in order to study the containment of this kind of configuration subjected to wind effects. It was shown that wind effects, in steady state, can lead to partial or total loss of the pollutant containment, with the mechanical ventilation on or off. Moreover, wind turbulence generates significant fluctuations of pressures and flow rates that can bring about instantaneous reversal leakage flow rates, which cannot be identified in steady state. From these experimental results, the zonal code SYLVIA, developed by IRSN and used notably to support safety assessments in nuclear buildings, has been validated for taking into account wind effects in steady and transient states