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A filtered containment venting system was developed for nuclear power plants. In the Fukushima Dai-ichi Nuclear Accident, widespread land contamination was caused by cesium-137. This system was developed to filter aerosol particles and reduce the amount of radioactive particle release, while protecting the primary containment vessel from over pressure by venting gas from the vessel. Performance tests were conducted under various vent gas flow rate conditions to ascertain decontamination factors for aerosol particles with various diameters. It was observed through the tests that aerodynamic diameter was a good index for characterizing various aerosol particles for the filtered containment venting system. Test results showed that the decontamination factors were well over 1,000 for aerosol particles with aerodynamic diameters larger than 0.4 μm. For aerosol particles with aerodynamic diameters larger than 0.2 μm, the decontamination factors significantly increased with the diameter. This suggested that inertial deposition was the governing mechanism for filtering aerosols in this system. The decontamination factor of the water scrubber section of the filter increased with the increase in Stokes number.

A suction air cooling by water spray has been used for inlet air of gas turbines. The cooling performance depends on spray characteristics and surrounding conditions. The aims of this study are to understand the spray characteristics under the various humidity conditions and to discuss influences of humidity on spray characteristics and cooling performance. A Phase Doppler Anemometry (PDA) provides spray characteristics. Air temperatures before cooling and after cooling are measured under various humidity conditions and the number of nozzles. Two types of nozzles, that is, an impaction PIN Jet nozzle and a Hole type nozzle, are tested. For both nozzles, evaporation of droplets becomes inactive with high humidity condition. For PIN Jet nozzles, spray droplets exist in large area and are smaller than those of Hole nozzle. For Hole nozzle, droplets size is larger at spray outer edge and spray area is smaller compared with PIN Jet nozzle. The cooling performance for PIN Jet nozzle is larger than that of Hole nozzle. The cooling performance becomes better when spray flow rate increases.