No abstract available

[en] A Sn-25 at.% Li alloy has been fabricated by starting with pure Sn and Li. The alloy was cast into various shapes and sent to researchers in several organizations in the United States and abroad for property measurements. The fabrication procedure involved gradual addition of Li from a separate vessel into a vessel that contained Sn; continuous stirring of the mixture during Li addition increased the Li content of the alloy gradually from 0 to the final value of 25 at.%. The melting temperature of the alloy was 334 C; its density was 6.36 g/cm(sup 3). Results are presented on microstructure, chemical composition, phase distribution, and microhardness of the alloy. Several experiments were conducted to evaluate the chemical reactivity of the alloy with air, water, and steam. Results showed that the alloy undergoes catastrophic oxidation when T and gt;250 C in air and develops an oxide scale in water at temperatures up to 95 C. Exposure in low-pressure steam at 200 C caused significant swelling and cracking of the alloy

[en] The relative effect of approx. 12 anion species, in conjunction with hydrogen and sodium cations, on the stress-corrosion-cracking (SCC) behavior of lightly sensitized Type 304 stainless steel was investigated in constant-extension-rate-tensile (CERT) tests at 289⁰C in water with 0.2 ppM dissolved oxygen at total conductivity values of less than or equal to 1 μS/cm. The results show that the sulfur species, either in acid or sodium form, produce the highest degree of IGSCC relative to other anions. The effect of temperature on the SCC behavior of the material was investigated in CERT tests over the range 110 to 320⁰C in high-purity water and in water containing 0.1 and 1.0 ppM sulfate as H₂SO₄ at a dissolved oxygen concentration of 0.2 ppM. The CERT parameters were correlated with impurity concentration (i.e., conductivity) and the electrochemical potential of platinum and Type 304 stainless steel electrodes in the high-temperature environments. Maximum IGSCC occurred at temperatures between approx. 200 and 250⁰C in high-purity water, and the addition of sulfate increased the average crack growth rates and the temperature range over which maximum susceptibility occurred. A distinct transition from intergranular to transgranular and ultimately to a ductile failure mode was observed as the temperature increased from approx. 270 to 320⁰C in high-purity water. This transition was attributed to a decrease in the open-circuit corrosion potential of the steel below a critical value of approx. 0 mV(SHE) at the higher temperature. A large decrease in the crack growth rates of fracture-mechanics-type specimens of the steel was also found when the temperature was increased from 289 to 320⁰C in high-purity water with 0.2 ppM dissolved oxygen. 26 references, 8 figures, 6 tables

[en] The influence of different impurities, viz., oxyacids and several chloride salts, on the stress-corrosion-cracking (SCC) of sensitized Type 304 stainless steel (SS) was investigated in constant-extension-rate-tensile (CERT) tests in 289⁰C water at a low dissolved-oxygen concentration (<5 ppB). Cyclic loading experiments on fatigue precracked fracture-mechanics-type specimens of this material and Type 316NG were also performed at 289⁰C in low-oxygen environments with and without sulfate at low concentrations. In these experiments, the crack growth behavior of the materials was correlated with the type and concentration of the impurities and the electrochemical potentials of Type 304 SS and platinum electrodes in the simulated hydrogen-water chemistry environments. The information suggests that better characterization of water quality, through measurement of the concentrations of individual species (SO₄^2-, NO₃^-, Cu²⁺, etc.) coupled with measurements of the corrosion and redox potentials at high temperatures will provide a viable means to monitor and ultimately improve the performance of BWR system materials

No abstract available

[en] Fixed-load Mode I/Mode III comparative tests have been conducted on lightly sensitized (EPR = 2 C/cm²) Type 304 SS specimens in 289⁰C oxygenated water with other impurity additives. Substantial susceptibility to IGSCC was shown in Mode I but no conclusive evidence for SCC was found in Mode III. These results are consistent with a hydrogen embrittlement mechanism of crack advance, but electrochemical measurements seem to accord better with a slip-dissolution mechanism. Further studies are needed to clarify the operative mechanism(s)

[en] Intergranular stress corrosion cracking (IGSCC) of sensitized Type 304 stainless steel (SS) has been a recurrent problem in the high-temperature water environment of boiling-water-reactors (BWRs) over the past two decades. The synergistic effects of environmental and material variables on stress corrosion cracking (SCC) of Type 304 SS were investigated at 289⁰C by means of constant-extension-rate-tensile (CERT) tests at a strain rate of 1 x 10^-6/s. Correlations among environmental variables (dissolved oxygen and impurity concentrations, viz., H₂SO₄, steady-state open-circuit electro-chemical potential) and the SCC susceptibility parameters have been determined. The extensive results over a wide range of open-circuit corrosion potential conditions were analyzed by a model which accounts for the effects of environmental variables, microstructure (e.g., degree of sensitization) and strain rate. The results are consistent with a slip-dissolution mechanism for SCC. Furthermore, representation of the dependence of corrosion potential and average crack growth rate on the dissolved oxygen concentration of the water by a simple mathematical function, in conjunction with the theoretical model, enables predictions of both strain rate and environmental effects on the SCC susceptibility of sensitized Type 304 SS. 12 refs., 7 figs

[en] A series of dynamic pressure tests have been conducted within EBR-II subassembly ducts. The tests were designed to simulate bursting of a driver-fuel element in a cluster of such elements at their burnup limit during off-normal conditions in EBR-II. The major objective of the tests was to assure that such failure, which might cause rapid release of stored fission gas, would not deform or otherwise damage subassembly ducts in a way that would hinder movement of a control rod. The test results are described

[en] A Sn-25at.%Li alloy has been fabricated by starting with pure Sn and Li. The alloy was cast into various shapes and sent to researchers in several organizations in the United States and abroad for property measurements. The fabrication procedure involved gradual addition of Li from a separate vessel into a vessel that contained Sn; continuous stirring of the mixture during Li addition increased the Li content of the alloy gradually from 0 to the final value of 25 at.%. The melting temperature of the alloy was 334 deg. C; its density was 6.36 g/cm³. Results are presented on microstructure, chemical composition, phase distribution, and microhardness of the alloy. Several experiments were conducted to evaluate the chemical reactivity of the alloy with air, water, and steam. Results showed that the alloy undergoes catastrophic oxidation when T>250 deg. C in air and develops an oxide scale in water at temperatures up to 95 deg. C. Exposure in low-pressure steam at 200 deg. C caused significant swelling and cracking of the alloy

[en] Slow-strain-rate tensile tests and microstructural analysis by Auger electron spectroscopy were conducted on specimens of high- and commercial-purity (HP and CP) heats of Type 304 stainless steel obtained from neutron absorber tubes and a control blade sheath after irradiation up to 2.5 x 10^2l n·cm^-2 (E > l MeV) in boiling water reactors (BWRs). The susceptibility of the HP absorber tubes to intergranular stress corrosion cracking (IGSCC) was higher than that of the CP absorber tubes or the CP control blade sheath. IGSCC susceptibilities of the BWR components could not be correlated to segregation impurities on grain boundaries. However for comparable fluence levels, Cr on grain-boundaries