Neutron-gamma hodoscope detection of fissile materials

The neutron-gamma hodoscope has been developed to make use of two aspects of the fission process that occur during severe safety testing of nuclear reactor fuel; fission-product heating that induces realistic effects in the fuel and penetrating radiation that enables the imaging of fuel behavior. During in-pile transient reactor experiments, the radiation which escapes from the test fuel, its surrounding coolant, and a thick-walled container is detected by a large collimated array that produced cineradiographic images. Phenomena observed in hundreds of destructive experiments have included pre-failure fuel motion, cladding breach, and post-failure fuel motion. On the basis of this successful 25-year experience, application of hodoscope techniques to arms control treaty verification is now being studied. 7 refs., 13 figs

Intrinsic-surface-tag image authentication

The objective of this work is to further the development of a unique treaty limited item (TLI) intrinsic surface tag for arms control applications. This tag's unique feature is the ability to capture the sub-micron scale topography of the TLI surface. The surface topography is captured by plastic castings of the surface as digitally imaged by an electron microscope. Tag authentication is accomplished by comparing digital castings images obtained in two different inspections. Surface replication experiments are described, as these experiments from the basis for the authentication algorithm. Both the experiments and the authentication algorithm are analyzed using the modulation transfer function. Recommendations for future improvements in tag authentication are also suggested by the modulation transfer function analysis. 4 refs

Developments in radiation hodoscope technology for arms control treaty verification

New hodoscope radiation detection technology developments offer a wide range of unique capabilities for arms control treaty verification (ACTV). Originally developed for civilian nuclear power research by Argonne National Laboratory, this concept uses a radiation detector array to detect objects inside opaque containments. To avoid unnecessary intrusiveness in treaty verification, spatial resolution must be limited and confirmed. Material density data and identification by radiation means may be either required or prohibited. ACTV instruments also should be inherently resistant to false indications--either accidental, or from attempt at deception. Hodoscope technology can meet these needs. ACTV hodoscopes do not require the heavy collimators of reactor hodoscopes, and relatively weak sources are sufficient. Gamma-ray transmission hodoscopes can be used to inspect canisters, railcars, etc. or to monitor objects such as rocket motors. This technique is deception-resistant: absorbers hidden to mask objects will be detected; and sources hidden to mask absorption will be substracted out as background. Nuclear warheads are detectable by strong gamma-ray absorption. In some cases, intrinsic gamma-ray radiation from warheads also could be used in a passive mode. Neutron hodoscopes can utilize neutron transmission, intrinsic neutron emission, or neutron reactions (either prompt or delayed) stimulated by a neutron source. Warheads can be counted by tomography, or by simple analysis of count rate curve patterns, depending on application. Hodoscope technology is a powerful tool for potential treaty verification uses; This paper considers that technology. 21 refs., 8 figs., 1 tab

Hodoscope performance tests on a 91-pin fuel bundle at PARKA. [LMFBR]

Joint LASL/ANL studies of the fuel motion performance capability of a fast-neutron hodoscope have been performed on a 91-pin fuel bundle. Optimization of the neutron detectors used in the hodoscope was also investigated. The neutron detectors tested were a Hornyak button and a stilbene detector with pulse shape discrimination. These studies show that a hodoscope can provide useful fuel motion detection capability for large bundles and that the amount of information provided is greatly increased by the use of neutron detectors with high neutron thresholds and high detection efficiency. These measurements indicate that the TREAT hodoscope can be upgraded to meet most of the fuel motion diagnostic requirements of new safety facilities

Teaching Access, or Freedom of Information Law

Based on the author\u27s experience developing and administering the course and materials, this article provides an introduction and resources to teach a graduate journalism or professional law school course on access to government, commonly called freedom of information law , which may be constructed as a capstone course in law school. The appendices provide supporting material and references

Fusion-Fission Hybrid Reactors

to the design of hybrid reactors and to inform the new generation of hybrid reactor researchers of the hybrid reactor data base developed in the seventies and early eighties

In-situ material-motion diagnostics and fuel radiography in experimental reactors

Material-motion monitoring has become a routine part of in-pile transient reactor-safety experiments. Diagnostic systems, such as the fast-neutron hodoscope, were developed for the purpose of providing direct time-resolved data on pre-failure fuel motion, cladding-breach time and location, and post-failure fuel relocation. Hodoscopes for this purpose have been installed at TREAT and CABRI; other types of imaging systems that have been tested are a coded-aperture at ACRR and a pinhole at TREAT. Diagnostic systems that use penetrating radiation emitted from the test section can non-invasively monitor fuel without damage to the measuring instrument during the radiographic images of test sections installed in the reator. Studies have been made of applications of hodoscopes to other experimental reactors, including PBF, FARET, STF, ETR, EBR-II, SAREF-STF, and DMT

Understanding correlation coefficients in treaty verification. Revised

When a pair of images is compared on a point-by-point basis, the linear-correlation coefficient is usually used as a measure of similarity or dissimilarity. This report evaluates the theoretical underpinnings and limitations of the linear-correlation coefficient, as well as other related statistics, particularly for cases where inherent white noise is present. As a result of the limitations in linear-correlation, an additional step has been derived -- local-sum clustering -- in order to improve recognition of small dissimilarities in a pair of otherwise identical images. Results show an optimal three-stage procedure: first, establish congruence of the two images; second, use the linear-correlation coefficient as a test of true negatives; and, third, qualify a true positive by using the cluster (local-sum) method. These three algorithmic stages would be especially useful in application to arms control treaty verification, particularly for comparison of unique identifiers (tags or seals). This is illustrated by comparing scanning-electron microscope topographical images for an intrinsic-surface tag