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Correlations were developed to model the performance of two types of multi-inlet aerosol sampling cyclones. The body of one cyclone had the Lapple conventional geometry and the other had a shorter design, which was one-half the length of the Lapple geometry. Four cyclones of each type were constructed, with body diameters of 38.1, 57.2, 88.9, and 139.7 mm. Each cyclone was tested at several flow rates, with the range of flow rates for the entire data set being from 9.4 L/min to 1027 L/min. Aerodynamic particle cutpoint diameters, D 0.5, were determined for several sets of test conditions, consisting of a given cyclone type and a fixed flow rate. The range of cutpoints determined in the experiments was 3.9−17.1 μm aerodynamic diameter. Experimental data were correlated to a logarithmic-linear relationship:  C 0.5 1/2 D 0.5 /d c = ln a + b ln Re f where C 0.5 is Cunningham's slip correction for the cutpoint size; d c is the cyclone diameter; and, Re f is the flow Reynolds number, which is characterized by the air inlet velocity and the width of the channel between the cyclone body and the outlet tube. The correlation coefficients, r 2 , for data of the long and short multi-inlet cyclones to the log-linear model were 0.984 and 0.991, respectively. The log-linear relationship between the size parameter and the flow Reynolds numbers was re-arranged to provide working relationships for designers. Fractional efficiencies were measured for each cyclone, and sigmoid curves were fitted to the data that provide a relationship between fractional efficiency and dimensionless particle size, (D a − D 0.5)/D 0.5, where D a is the aerodynamic particle diameter.

Cerium oxide (CeO2) dust is recommended as a surrogate for plutonium oxide (PuO2) in airborne release fraction experiments. The total range of applicable particle sizes for PuO2 extends from 0.0032 µm (the diameter of a single PuO2 molecule) to 10 µm (the defined upper boundary for respirable particles). For particulates with a physical particle diameter of 1.0 µm, the corresponding aerodynamic diameters for CeO2 and PuO2 are 2.7 µm and 3.4 µm, respectively. Cascade impactor air samplers are capable of measuring the size distributions of CeO2 or PuO2 particulates. In this document, the aerodynamic diameters for CeO2 and PuO2 were calculated for seven different physical diameters (0.0032, 0.02, 0.11, 0.27, 1.0, 3.2, and 10 µm). For cascade impactor measurements, CeO2 and PuO2 particulates with the same physical diameter would be collected onto the same or adjacent collection substrates. The difference between the aerodynamic diameter of CeO2 and PuO2 particles (that have the same physical diameter) is 39% of the resolution of a twelve-stage MSP Inc. 125 cascade impactor, and 34% for an eight-stage Andersen impactor. An approach is given to calculate the committed effective dose (CED) coefficient for PuO2 aerosol particles, compared to a corresponding aerodynamic diameter of CeO2 particles. With this approach, use of CeO2 as a surrogate for PuO2 material would follow a direct conversion based on a molar equivalent. In addition to the analytical information developed for this document, several US national labs have published articles about the use of CeO2 as a PuO2 surrogate. Different physical and chemical aspects were considered by these investigators, including thermal properties, ceramic formulations, cold pressing, sintering, molecular reactions, and mass loss in high temperature gas flows. All of those US national lab studies recommended the use of CeO2 as a surrogate material for PuO2. Definitions Activity Median Aerodynamic Diameter (AMAD) ICRP Definition-Fifty per cent of the activity in the aerosol is associated with particles of aerodynamic diameter greater than the AMAD. Aerodynamic Diameter-The diameter of a hypothetical (spherical) particle of unit density (1.0 g/cc) that has the same (terminal) settling velocity as the particle under consideration.