Aerosol Physics Considerations for Using Cerium Oxide CeO_2 as a Surrogate for Plutonium Oxide PuO_2 in Airborne Release Fraction Measurements for Storage Container Investigations LAUR-17-24562

摘要

Cerium oxide (CeO_2) powder is recommended as a surrogate for plutonium oxide (PuO_2) in airborne release fraction experiments. The total range of applicable particle sizes for PuO_2 extends from 0.0032 μm (the diameter of a single PuO_2 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 CeO_2 and PuO_2 are 2.7 μm and 3.4 μm, respectively. Cascade impactor air samplers are capable of measuring the size distributions of CeO_2 or PuO_2 particulates. In this document, the aerodynamic diameters for CeO_2 and PuO_2 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, CeO_2 and PuO_2 particulates with the same physical diameter would be collected onto the same or adjacent collection substrates. The difference between the aerodynamic diameter of CeO_2 and PuO_2 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 PuO_2 aerosol particles, the use of CeO_2 would have a direct relationship to PuO_2 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 CeO_2 as a PuO_2 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 CeO_2 and PuO_2 material, all recommended the use of CeO_2 as a surrogate material for PuO_2.