Evaluation of Method for Radioactive Cesium in Flue Gas by Measurement of Particle Number Concentrations

Abstract

Radioactive cesium concentrations in flue gas are measured using the official analytical method stipu-lated by the Ministry of the Environment. Using this method, radioactive cesium is analyzed for dust collected by filters and fluids collected in impingers. Although filters are known to collect sufficient radioactive cesium in flue gas, no detailed data are available for their ability to collect ultrafine particulate matter. Therefore, this study was conducted to evaluate the official analytical method by measuring the number concentration of particles in the actual incinerator flue gas. Results demonstrate that the number concentration of ultrafine particles (particles with < 0 . 3 μ m diameter) at the bag filter inlet is 10 6 cm − 3N , although it is 10 2 cm − 3N at the outlet of the impinger. This finding demonstrates that approximately 99 . 99 % of the ultrafine particles can be captured using the official analytical method. Furthermore, when the radioactive cesium in the collected particles at the outlet of the impinger was analyzed, its concentration was found to be below the limits of detection. This finding confirms that the official analytical method is appropriate for taking samples of radioactive cesium in flue gas.