Unrestricted Release Measurements with Ambient Air Ionization Monitors

ABSTRACT Radiation monitoring systems based on the long-range alpha detection (LRAD) technique, such as the BNFL Instruments IonSens, provide a single contamination measurement for an entire object rather than the more familiar series of individual readings for smaller surface areas. The LRAD technique relies on the ionization of ambient air molecules by alpha particles, and the subsequent detection of these ions, rather than direct detection of the alpha particles themselves. A single monitor can detect all of the ions produced over a large object (pipe, I-beam, reinforcing bar, etc.) and report a total contamination level for the entire surface of that object. Currently, both the unrestricted release limits specified in USDOE Order 5400.5 (and similar documents in other countries), and the definitions of radioactive waste categories, are stated in terms of contamination per area (e.g. 20 dpm/100 cm