Validation of pretreatment of filter samples for airborne plutonium monitoring: a feasibility study

Airborne plutonium monitoring is a significant component of radioecology, environmental surveys and early warning. However, plutonium loss in pretreatment of filter samples can still be easily neglected, while suitable certified reference materials are currently unavailable. The feasibility of preparation of filter samplers was studied with regard to validation of pretreatment such as dry ashing. Utilising an in-house device, Pu-bearing soils are dispersed to aerosol by using a Venturi tube disperser, with the aerosol deposited into filter media to produce filter samples. During this process, the soil particles should be of the same distribution in the filter samples as in the real samples, hence the reliability of validation will be enhanced. This method was validated by the experimental results, where the relative uncertainties of the 239Pu content in soils with inhomogeneity are below 2%, while the soils can be transferred quantitatively with a device possessing (98.2 +/- 2.0)% efficiency. An ashing process for the filter samples at 600 degrees C for 6 h was then applied to the filter samples. The measured Pu-239 content in soil in the filter samples is consistent with uncertainties regarding the Pu-239 content in the soil only.