A Fingerprinting Detector for Special Nuclear Material Based on Optically Coupled BGO/BC454 Scintillators with a Mixed Neutron/Gamma- Ray Signal*.

One of the most difficult issues faced by negotiators of disarmament treaties is arranging for joint verification of extremely sensitive items such as nuclear warheads, components, and materials. A possible approach obtains a “nuclear fingerprint” of the item using a detector system that cannot be reverse engineered. One system being evaluated consists of optically coupled bismuth germanate (BGO) and boron-loaded plastic (BC454) scintillators. The BC454 combines neutron moderation (H) and detection (10B) at the molecular level, which provides high detection efficiency and short die-away time, and the BGO mixes in a gamma-ray signal. Experiments have been performed to characterize the detector’s response and to validate the computer simulations using both spectral and multiplicity data. The detector system has also been tested for possible verification activities involving dismantlement of nuclear weapons.