Applications of water-based neutron detectors for nuclear safeguards and security

The depletion of national helium-3 stockpiles has necessitated the development of non- helium-3 based neutron detectors. The Water Neutron Detector (WaND) is a novel concept that utilizes gadolinium-doped water as a neutron multiplicity counting medium for special nuclear material. The detection system meets standards set forth by [1] for helium-3 replacement technologies. It has high efficiency (28%), a short neutron capture time (~15 microsecond, tunable based on the gadolinium percentage), high gamma rejection (108:1 for cobalt-60), and is robust, nontoxic, and non-flammable. The active detector volume is 1.02 m3 deionized water doped with 0.25% of the neutron capture agent gadolinium, in a soluble chloride compound. The detection principle relies on the Cherenkov light created following a gamma cascade from a neutron capture on gadolinium. Recently, the WaND system has been investigated for applicability to neutron multiplicity counting for International Atomic Energy Agency (IAEA) safeguards purposes. Research will be presented describing the detector’s technical merits as outlined by the 2013 IAEA Workshop on Requirements and Potential Technologies for Replacement of 3He Detectors in IAEA Safeguards Applications. Overall, the WaND system compares favorably, especially as a dedicated assay tool for low plutonium quantities.