Environmental continuous air monitor for ambient transuranic particulates

We have constructed a working prototype of an environmental continuous air monitor (ECAM) for outdoor applications. The ECAM device is designed to continuously monitor the presence of transuranic contaminant aerosol below a size of 10 mm aerodynamic diameter. In remote operation, the ECAM can transmit radiological and meteorological data to a central processing location, where we have implemented geographical mapping and GPS capabilities into an integrated software package. The Canberra Alpha Sentry Monitor, a commercially available continuous air monitor (CAM) for indoor room applications, was used as the basic building block for the prototype. We increased the sample air flow to 4 cubic feet per minute (CFM) compared to the design air flow rate of 2 CFM. We also added a spread-spectrum radio data link between the CAM RS-232 serial port and a distant radio receiver that enables remote monitoring. In order to avoid collecting the large diameter particle fraction containing most of the inert mass that causes sample burial and alpha spectrum degradation, a Model 254 PM10 size-fractionating Wet from Graseby-Andersen was fitted to the Alpha Sentry Monitor. We removed the top cover of the CAM unit, and routed openings in the top surface of the CAM inlet. This allows air to flow into the inlet, down a collection tube, and then vertically into the CAM without the elbow and horizontal transition piece of the present in-line adapter. The air flows through a 47 mm filter, and the transuranic contamination is counted by a solid state alpha radiation detector, which is placed at a distance of 5 mm above the filter. The increased air flow significantly improves CAM alarm sensitivity and response time to an estimated level of 3.8x10-12 mCi/ml for an integration period 30 minutes. At the same time, the fractionating inlet removes a substantial amount of inert dust and thus enables extended monitoring without frequent maintenance