15 research outputs found
Influence of temperature, strain rate and thermal aging on the structure/property behavior of uranium 6 wt% Nb
A rigorous experimentation and validation program is
being undertaken to create constitutive models that elucidate the
fundamental mechanisms controlling plasticity in uranium-6 wt.% niobium
alloys (U-6Nb). These models should accurately predict high-strain-rate
large-strain plasticity, damage evolution and failure. The goal is a
physically-based constitutive model that captures 1) an understanding of how
strain rate, temperature, and aging affects the mechanical response of a
material, and 2) an understanding of the operative deformation mechanisms.
The stress-strain response of U-6Nb has been studied as a function of
temperature, strain-rate, and thermal aging. U-6Nb specimens in a
solution-treated and quenched condition (ST/Q) and after subsequent aging at
473K for 2 hours were studied. The constitutive behavior was evaluated over
the range of strain rates from quasi-static (0.001 sec to dynamic
(2000 sec and temperatures ranging from 77 to 773K. The
yield stress of U-6Nb was exhibited pronounced temperature sensitivity. The
strain hardening rate is seen to be less sensitive to strain rate and
temperature beyond plastic strains of 0.10. The yield strength of the aged
material is less significantly affected by temperature and the work
hardening rate shows adiabatic heating at lower strain rates (1/s)
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Preliminary safe-handling experiments on a mixture of cesium nickel ferrocyanide and equimolar sodium nitrate/nitrite
As part of the Hanford Site's evaluation of the potential hazards associated with the storage of ferrocyanide wastes generated when ferrocyanide was used to scavenge radiocesium from waste supernates in the 1950s, the Pacific Northwest Laboratory (PNL) subcontracted with Los Alamos National Laboratory (LANL) to perform a series of sensitivity tests. These test supplement PNL's thermal sensitivity testing results on the reactivity of cesium nickel ferrocyanide (Cs{sub 2}NiFe(CN){sub 6}) and nitrates and nitrites (Burger and Schelle 1991). LANL used a selected set of their standard tests to determine the sensitivity of a mixture of Cs{sub 2}NiFe(CN){sub 6} (FECN-1) and equimolar sodium nitrate and nitrite oxidant to nonthermal and thermal stimuli. The stoichiometric ratio of oxidant to Cs{sub 2}NiFe(CN){sub 6} in the tested mixture FECN-1 was 1.1:1. The appendix presents the results of the LANL testing of the sensitivity of FECN-1 to initiation by mechanical impact, spark, friction, and various thermal conditions. In addition to the sensitivity testing, LANL used an Accelerating Rate Calorimeter (ARC) to estimate the behavior of large batches of the mixture
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Cygnus experiment at Los Alamos
The Cygnus experiment at Los Alamos National Laboratory has been designed to study, with high angular accuracy, point sources of gamma rays of energy above 10/sup 14/ eV. The experimental detector consists of an air shower array to observe gamma-ray showers and a shielded, large-area track detector to study the muon content of the showers. In this paper we present preliminary data from the array and describe its performance. 9 refs., 3 figs
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Ferrocyanide-containing waste tanks: Ferrocyanide chemistry and reactivity
The complexing constant for hexacyano-iron complexes, both Fe(2) and Fe(3), are exceptionally large. The derived transition metal salts or double salts containing alkali metal ions are only slightly soluble. The various nickel compounds examined in this study, i.e., those predicted to have been formed in the Hanford waste scavenging program, are typical examples. In spite of their relative stability towards most reagents under ambient conditions, they are all thermodynamically unstable towards oxidation and react explosively with oxidants such as nitrate or nitrate salts when heated to temperatures in excess of 200{degree}C. 42 refs., 5 figs., 3 tabs