Year
2017
Abstract
Cerium oxide (CeO2) powder 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. For values of the calculated committed effective dose (CED) coefficient for PuO2 aerosol particles, the use of CeO2 would have a direct relationship to PuO2 material based on molar equivalent. In addition to the analytical information developed for this document, a literature search identified publications that investigated 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, compacting, sintering, molecular reactions, grain size measurements and mass loss in high temperature gas flows. Of the studies that worked with CeO2 and PuO2 material, all recommended the use of CeO2 as a surrogate material for PuO2.