Characterization of the Degradation of HEPA Filters Protected by Different Spark Arrestors for Various Cutting Means and Cutting Conditions

Abstract

The ageing of the nuclear installations induces new challenges regarding the containment of radioactive matter especially airborne contamination. The purification of the air using fibrous filters is the most widely used technology for the containment of this contamination. However, to ensure their role, they need to be protected. The release of incandescent particles cutting processes could reduce their efficiency. Many spark arrestors are available to protect the filters from hot particles. They are designed to be implemented upstream the filter. Three technologies of spark arrestors have been tested when they are exposed to a grinder or a plasma cutting process. The experiments have been performed for two different filters (450 and 1500 m3/h flow rate). The particle size distribution of the aerosol produced by a plasma torch cutting has been measured and shows two characteristic modes for this kind of generation process. The filtration efficiency of the high efficiency particulate air (HEPA) filter has been measured before and after the cutting (NF-EN-ISO-16170). During the experiments, the pressure drop of the HEPA filters has been measured to estimate their clogging rate. Results show that the plasma cutting is a more penalizing cutting process compared to metal grinder and that the metallic fibrous medium with the finest mesh has the better performance to protect filters from sparks. The cut length and the distance between the filter and the spark arrestor have also been studied, showing a limited impact on the degradation of the filtration efficiency.