Publications

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An assessment of the effects of cation concentration on the thermophysical properties of salts in the temperature range of 300 to 500°C was investigated. The latent heat and density exhibit a statistically relevant dependence upon mixtures, while heat capacity, viscosity, and thermal conductivity did not exhibit statistical differences among mixtures in the range of temperature studied. Heat capacity tended to be nearly flat while in the liquid state for mixtures at each temperature. Density of the mixtures decreases linearly with temperature. Mixture composition influenced density, with a relative variation up to 2% over the temperature range investigated. Viscosity decreased as a function of temperature in a non-linear fashion and methods used here tended to exhibit a higher value than literature values. Thermal conductivity used laser flash and transient wire methods. Transient wire found no differences between mixtures within repeatability of the measurement, while laser flash was found to not work well for molten nitrate salts due to the large error.

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Two classes of materials, poly(methylene diphenyl diisocyanate) or PMDI foam, and cross-linked epoxy resins, were characterized using thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC), to help understand the effects of aging and %E2%80%9Cbake-out%E2%80%9D. The materials were evaluated for mass loss and the onset of decomposition. In some experiments, volatile materials released during heating were analyzed via mass spectroscopy. In all, over twenty materials were evaluated to compare the mass loss and onset temperature for decomposition. Model free kinetic (MFK) measurements, acquired using variable heating rate TGA experiments, were used to calculate the apparent activation energy of thermal decomposition. From these compiled data the effects of aging, bake-out, and sample history on the thermal stability of materials were compared. No significant differences between aged and unaged materials were detected. Bake-out did slightly affect the onset temperature of decomposition but only at the highest bake-out temperatures. Finally, some recommendations for future handling are made.

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This report describes the development of a new detection method for electrostatic discharge (ESD) testing of explosives, using a single-lens reflex (SLR) digital camera and a 200-mm macro lens. This method has demonstrated several distinct advantages to other current ESD detection methods, including the creation of a permanent record, an enlarged image for real-time viewing as well as extended periods of review, and ability to combine with most other Go/No-Go sensors. This report includes details of the method, including camera settings and position, and results with wellcharacterized explosives PETN and RDX, and two ESD-sensitive aluminum powders.

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Hydrogen getters were tested for use in storage of plutonium-bearing materials in accordance with DOE's Criteria for Interim Safe Storage of Plutonium Bearing Materials. The original studies, documented in Sandia Report SAND2007-0095, included HiTop getter material aged for 3 months at 70°C. This material was aged for an additional 3 months for a total of 6 months at 70°C, and the performance of the getter was evaluated again and documented in Sandia Report SAND2007-1789P. This material was then aged for an additional 7 months for a total of 13 months at 70°C, and the performance of the getter under recombination and gettering conditions was evaluated. A sample of the 13 months aged getter was exposed to radiation at SRNL, and the performance of this sample was also evaluated. The results of the 13 months study is reported in SAND2007-7165P. The HiTop material was aged for an additional 5 months for a total of 18 months. This material was split into two samples with the second sample being exposed to radiation at SRNL. The performance of the 18 month aged HiTop material is covered in this report. The 18-month aged material showed similar performance under gettering conditions to the previously aged material: the recombination rate is well above the required rate of 45 std. cc H₂/h, and the gettering reaction occurs in the absence of oxygen at a slower rate. Both pressure drop measurements and ¹H NMR analyses support these conclusions. ¹H NMR analyses show extremely minor changes in the 18-month aged material, which can be possibly attributed to slight decomposition of the HiTop material or absorption of contaminants during the aging process.

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