Gamma-Ray Detectors for Intelligent, Hand-Held Radiation Monitors

Small radiation detectors based on HgI2, bismuth germanate (BGO), plastic, or NaI(Tl) detector materials were evaluated for use in small, lightweight radiation monitors. The two denser materials, HgI2 and BGO, had poor resolution at low-energy and thus performed less well than NaI(Tl) in detecting low-energy gamma rays from bare, enriched uranium. The plastic scintillator, a Compton recoil detector, also performed less well at low gammaray energy. Two small NaI(Tl) detectors were suitable for detecting bare uranium and shielded plutonium. One became part of a new lightweight hand-held monitor and the other found use as a pole-mounted detector for monitoring hard-to-reach locations.