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[en] This report briefly describes the neutrons and gamma rays emitted by active interrogation of HEU, briefly discusses measurement methods, briefly discusses sources and detectors relevant to detection of shielded HEU in Sealand containers, and lists the measurement possibilities for the various sources. All but one of the measurement methods detect radiation emitted by induced fission in the HEU; the exception utilizes nuclear resonance fluorescence. The brief descriptions are supplemented by references. This report presents some active interrogation possibilities but the status of understanding is not advanced enough to select particular methods. Additional research is needed to evaluate these possibilities

[en] Prompt neutron decay constants were measured for a delayed critical, unmoderated and unreflected U metal sphere at the Oak Ridge Critical Experiments Facility. Prompt neutron decay constant was 1.1095±0.0013 μs^-1. This can be used to verify calculational methods, both deterministic and Monte Carlo neutron transport methods. This value is in agreement with the value from GODIVA I data corrected for effects of support structure (1.10±0.01 μs^-1) but has a much smaller error as a result of the large number (167) of the measurements here and the high degree of sphericity of the sphere

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[en] The concept for the Oak Ridge Multiple Attribute System (ORMAS) is a Nuclear Materials Identification System (NMIS) time-dependent coincidence processor that incorporates gamma ray spectrometry and utilizes a small, lightweight, portable DT neutron (14.1 MeV) generator (1 x 10⁸ n/s), proton recoil scintillation detectors, and a gamma ray detector (HPGe). ORMAS is based on detecting fission neutrons and gamma rays from inherent source fission, fission induced by the external DT source, gamma ray detection of natural emissions of uranium and Pu, and induced gamma ray emission by the interaction of the 14.1 MeV neutrons from the DT source. This system is uniquely suited for detection of shielded highly enriched uranium (HEU), plutonium and other special nuclear materials, and detection of high explosives (HE), chemical agents, and in some cases, drugs. It could easily be adjusted to utilize a trusted processor that incorporates information barrier and authentication techniques using open software and then be useful in some international applications for materials whose characteristics may be classified. Since it is based entirely on commercially available components, the entire system, including the NMIS data acquisition boards, can be built with commercial off the shelf components (COTS). ORMAS incorporates the PINS technology of A. J. Caffrey of the Idaho National Engineering and Environmental Laboratory for HE, chemical agents, and drugs detection

[en] Nuclear reaction detectors capable of position sensitivity with submillimeter resolution in two dimensions are each provided by placing arrays of scintillation or wavelength shifting optical fibers formed of a plurality of such optical fibers in a side-by-side relationship in X and Y directions with a layer of nuclear reactive material operatively associated with surface regions of the optical fiber arrays. Each nuclear reaction occurring in the layer of nuclear reactive material produces energetic particles for simultaneously providing a light pulse in a single optical fiber in the X oriented array and in a single optical fiber in the Y oriented array. These pulses of light are transmitted to a signal producing circuit for providing signals indicative of the X-Y coordinates of each nuclear event. 6 figures

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