Diffusion screen removal of radon progeny from continuous air monitoring samples

Radon progeny are ubiquitous in plutonium facility workplace atmospheres, which often must be continuously monitored for the presence of low concentrations of transuranic contaminants. The alpha decay energy of the /sup 218/Po and /sup 212/Bi (6 MeV) radon and thoron daughters is sufficiently close to the alpha energies of important actinides such as /sup 239/Pu (5.15 MeV) and /sup 241/Am (5.5 MeV) that considerable interference in the process of detection can result. A novel approach to suppressing the contributions of these background alpha-emitters to the transuranic count based on selective removal of high diffusion mobility size particles containing radon daughters has been developed. Laboratory investigations of several factors of determining the performance of such an approach have been completed, and a prototype continuous air monitor has been successfully built and tested incorporating a screened inlet.<>