The work reported here was funded by Washington River Protection Solutions (WRPS). Dave Swanberg with WRPS led the effort and provided both programmatic guidance and technical input to the project team. These screening tests were very laboratory intensive. At Pacific Northwest National Laboratory (PNNL), Ben Williams was instrumental in preparing the Cast Stone specimens and conducting the leach tests. Don Rinehart prepared the simulants. Keith Geiszler, Steve Baum, Igor Kutnyakov, Christian Iovin, and Dennesse Smith analyzed the many samples. Stan Pitman, Mike Dahl, and Karl Mattlin conducted the compressive strength measurements. At Savannah River National Laboratory (SRNL), Vickie Williams was the cornerstone of the preparation and measurement of the Cast Stone fresh properties, Kim Wyszynski and Vickie Williams prepared the simulants, and David Best, Whitney Riley, and Beverly Wall performed the analyses. John Harris with LaFarge graciously provided the dry blend ingredients sourced from the northwest.

Many international border crossings presently screen cargo for illicit nuclear material using radiation portal monitors (RPMs) that measure the gamma ray and/or neutron flux emitted by vehicles. The fact that many target sources have a point-like geometry can be exploited to detect subthreshold sources and filter out benign sources that frequently possess a distributed geometry. This report describes a two-step process, which has the potential to complement other alarm algorithms, for detecting and characterizing point sources. The first step applies a matched filter whereas step two uses a weighted nonlinear least squares method. In a basecase simulation, matched filtering detected a 250-cps source injected onto a white-noise background at a 95% detection probability and a 0.003 false alarm probability. For the same simulation, the maximum likelihood estimation technique performed well at source strengths of 250 and 400 cps. These simulations provided a best-case feasibility study for this technique, which will be extended to experimental data that possess false point-source signatures resulting from background shielding caused by vehicle design and cargo distribution.

Magnitude, distance, and amplitude corrections (MDAC) made to observed regional amplitudes are necessary so that what remains in the corrected amplitude is mostly information about the seismic source type. Corrected amplitudes can be used in ratios to discriminate between earthquakes and explosions. However, source effects remain that cannot easily be determined and applied as amplitude corrections, such as those due to depth, focal mechanism, local material property, and apparent stress variability. We develop a mathematical model to capture these nearsource effects as random (unknown), giving an error partition of three sources: model inadequacy, station noise, and amplitude correlation. This mathematical model is the basis for a general multistation regional discriminant formulation. The standard error of the discriminant includes the variances of model inadequacy and station noise, along with amplitude correlation in its formulation. The developed methods are demonstrated for a collection of Nevada test site (NTS) events observed at regional stations (see Fig. 1). Importantly, the proposed formulation includes all corrected amplitude information through the construction of multistation discriminants. In contrast, previous studies have only computed discriminants from single stations having both P and S amplitudes. The proposed multistation approach has similarities to the wellestablished m b versus M s discriminant and represents a new paradigm for the regional discrimination problem.

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The authors constructed a prototype Time-Encoded Signature (TES) system, complete with automated detection algorithms that can be used to detect point-like gamma-ray sources in search applications where detectors observe large variability in background count rates beyond statistical (Poisson) noise. The person-carried system consists of two cesium iodide scintillators placed on opposite sides of a lead shield. This geometry mitigates systematic background variation and induces a unique signature upon encountering point-like sources. This manuscript focuses on the development of detection algorithms that identify point-source signatures while remaining computationally simple. The latter constraint derives from the instrument's mobile (and thus low power) operation. The authors evaluated algorithms using both simulated and field data. The results of this analysis demonstrate the capability to detect sources at a wide range of source-detector distances using computationally simple algorithms.