The Defense Threat Reduction Agency (DTRA) requires the capability to detect 1kg of highly enriched uranium (HEU) shielded by a 1 mm lead shield from a 2 meter standoff position in less than 1 minute. The sensor should be man-portable, battery-operated and capable of field operation by field personnel with a minimum of training. The unit should be capable of operating for 12 hours without recharging. The sensor, not including the power source, should be transportable as checked baggage on commercial airlines. The unit should be free of liability or safety issues. Operation at a standoff distance of 20 meters is desirable.

A minimal amount of shielding drastically decreases the radiation signature of uranium. Passive radiation detection technologies for shielded highly enriched uranium rely on the detection of impurities whose presence and relative abundance vary widely. Active radiation detection techniques present potential liability issues in public or non-controlled settings and possible safety issues in other settings. Under international agreements, monitoring HEU storage with confidence may become a problem. In border and portal monitoring situations, active techniques may only be used if personnel are isolated from packages, an operational restriction on deployment. At larger standoff distances, current passive and active radiation detection approaches have very poor sensitivity. A standoff detector capable of sensing shielded HEU either passively or with minimal active interrogation would be of interest to DTRA.

- Quoted from the DTRA03-001 Statement of Need

The RADMAN project at WKU was begun in 1997. The objective was to build a hand-held portable gamma ray scanner for U.S. Customs in response to a Broad Agency Announcement, and part of a proposal to this BAA. In order to minimize the cost of the final project, a number of commercial-off-the-shelf items were used in its construction including: an AMPTEK 8000A multichannel analyzer, a 1” CsI detector crystal mounted on a pin-diode with an amplifier, and an Everex palm-top.

The analysis software was to perform the following functions: 1) calibrate the system automatically during battery charging, 2) acquire and store a background in an autonomous manner which would be used later automatically, 3) acquire a spectrum whenever the user desired, 4) strip the background from the spectrum with the background, 5) use the Method of Mariscotti to find peaks, 6) match these peaks (in keV) against a table of known gamma rays, 7) determine if these gamma rays were significantly above background and their threat potential and 8) return the results (including threat potential) to the user. Another secondary function was to graph these spectra and peak locations.

• Radman Side View.

• Radman Top View.

The Radman software was later modified to be a subsystem in the PELAN. In 2002, we participated in a demonstration of this subsystem for the U.S. Navy. The only false negatives occurred when a low energy source was abundantly shielded (the calculated attenuation of the shielding  was 10^-81).

We also performed a number of in-house proof-of-principle measurements to detect shielded radiological materials. Based on these measurements, we expect that we could detect 1 Ci of ¹³⁷Cs shielded with 10 cm of Pb at a distance 22 m. For HEU, we have calculated that we can detect 1 kg of HEU in 1 mm of Pb at a distance of 14 m. At this time, they nearly meet the desired requirement of 20 m in DTRA’s statement of need. We believe that with some research into sensitivity that we can meet the desired requirements.

For more detailed information, please see the Publications portion of this web site.