Characterization of Incandescent Particles Emitted by a Cut-Off Grinder During Decommissioning Operations for Evaluating Filter Degradation

The use of mechanical or thermal cutting tools when decommissioning nuclear facilities generates a lot of incandescent particles. These particles may represent a deterioration risk of the containment barriers associated with a potential fire hazard. The aim of this study is to characterize, in terms of temperature, diameter, and velocity, the incandescent particles emitted by a wheel grinder and to follow these parameters all along their path from emission point to their impact on the air filter. The characteristics of the particles correlated with a possible loss of filter efficiency should identify which particles degrade the filter. All the measurement techniques used to experimentally characterize 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 the particle tracking velocimetry (PTV) technique. An adaptation of a commercial monochromatic pyrometer is achieved to measure the temperature of the in-flight particles in a specific configuration. All of these techniques have been implemented on an experimental facility reproducing representative conditions of the cutting processes realized during dismantling operations. Both a global and a local approach to filter degradation are used to investigate the filter. The decontamination factor of a high efficiency particle air (HEPA) filter is measured, and detailed visualizations of the filter fiber deteriorations are obtained using a scanning electron microscope (SEM).