CHARACTERIZATION OF INCANDESCENT PARTICLES EMITTED BY A CUT-OFF GRINDER DURING DECOMMISSIONING OPERATIONS FOR EVALUATING FILTERS DEGRADATION
Résumé
The use of mechanical or thermal cutting tools in decommissioning of nuclear facilities generates a lot of incandescent particles. Those particles may represent a deterioration risk of the containment barriers associated with a potential risk of fire starting. The aim of this study is to characterize the incandescent particles emitted by a wheel grinder (in terms of temperature, diameter and velocity) and to follow those parameters all along their path from their emission point to their impact on the air filter. The characteristics of particles correlated with a possible loss of filter efficiency should highlight the destructing particles for the filter. All the measurement techniques used to characterize experimentally the incandescent particles are presented in this article. Particles are characterized in terms of diameter by microscope visualizations. The particle velocity is measured with a high speed camera using Particle Tracking Velocimetry (PTV) technique. An adaptation of a commercial monochromatic pyrometer is achieved to measure the in-flight particles temperature in our specific configuration. All of these techniques have been implemented on an experimental facility which reproduces representative conditions of the cutting processes realized during dismantling operations. Concerning the investigation of the filter, a global and a local approaches about filter degradation are used. The decontamination factor of High Efficiency Particle Air (HEPA) filter is measured, and detailed visualizations of the filter fibers deteriorations are obtained using Scanning Electrons Microscope (SEM).