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A Method of Discriminating Transuranic Radionuclides from Radon Progeny Using Low-Resolution Alpha Spectroscopy and Curve-Fitting Techniques

Konzen, Kevin*; Brey, Richard

doi: 10.1097/HP.0b013e31824641a8

222Rn (radon) and 220Rn (thoron) progeny are known to interfere with determining the presence of long-lived transuranic radionuclides, such as plutonium and americium, and require from several hours up to several days for conclusive results. Methods are proposed that should expedite the analysis of air samples for determining the amount of transuranic radionuclides present using low-resolution alpha spectroscopy systems available from typical alpha continuous air monitors (CAMs) with multi-channel analyzer (MCA) capabilities. An alpha spectra simulation program was developed in Microsoft Excel visual basic that employed the use of Monte Carlo numerical methods and serial-decay differential equations that resembled actual spectra. Transuranic radionuclides were able to be quantified with statistical certainty by applying peak fitting equations using the method of least squares. Initial favorable results were achieved when samples containing radon progeny were decayed 15 to 30 min, and samples containing both radon and thoron progeny were decayed at least 60 min. The effort indicates that timely decisions can be made when determining transuranic activity using available alpha CAMs with alpha spectroscopy capabilities for counting retrospective air samples if accompanied by analyses that consider the characteristics of serial decay.

This research explores the possibility of using an alpha CAM for counting retrospective air samples to expedite the determination of transuranic radionuclides in the presence of radon progeny.

*Radiological Technical Advisor for the Idaho Cleanup Project, Idaho Falls, ID; †Idaho State University, Pocatello, ID.

The authors declare no conflict of interest.

©2012Health Physics Society