Measurement of the median particle size diameter of airborne particles collected within Duratek\u27s Metal Melt facility

Concerns related to the occupational health of workers employed in the nuclear industry continue unabated. Often the concern for workers involves the potential absorbed dose to critical organs, and the associated potential health risk that results from inhaling airborne radioactive particulate material. The ability to determine the particle size in the workplace provides useful information to this end. Measurement techniques used to measure and quantify particle size diameters must be capable of providing data on the contaminant within the size range reaching the critical organs. Representative large area air samples were collected on four days over an eight-month period, atop the furnace deck located inside the contamination zone (CZ) process area in Duratek\u27s Metal Melt facility (MMF). These samples were collected as various client nuclear power customers\u27 waste metals were processed. Following the sample collection process, the samples were weighed and analyzed using two different techniques to determine the subsequent particle size distribution. The sampling and analysis techniques used for this work provide a reasonable estimate for the typical particle size distribution of airborne particulate material found within Duratek\u27s MMF. Completion of this work has resulted in the determination of the median projected area diameter (MPAD), and the associated activity median aerodynamic diameter (AMAD) of airborne particulate material in the MMF during routine operation. The MPAD finding will be used to determine the effectiveness of current procedural and engineering controls in use to protect workers from the inhalation of airborne particulate material. In addition, the AMAD value can be used in conjunction with Duratek\u27 s bioassay program to correct intake estimates. Results from this analysis yielded an MPAD value of 2.5 µm, having a geometric standard deviation of 2.6. An MPAD value of 2.5 µm correlates to an AMAD value of 5 µm, assuming a particle physical density of 4 g/cm3 and is spherical in shape. This value is 5 times the size of the 1 µm value currently used in the International Commission Radiological Protection (ICRP) 30 lung deposition model. However, it should be noted that ICRP 66 lists 5 µm AMAD values for possible use in internal dosimetry calculations