128 research outputs found
Interaction of short cracks with the local microstructure
AbstractIncreasing the resistance of a material against fatigue crack growth by optimizing the microstructure is one of the major tasks of modern materials science. Thereby grain and phase boundaries are microstructural elements which can decelerate the propagation rate especially of short cracks. However, in different materials cracks and grain boundaries interact differently. For instance in some steels the blocking effect was only found for large angle grain boundaries while small angle boundaries showed nearly no effect. On the other hand in nickel based superalloys a retardation of cracks was found even for small angle boundaries when the crack was propagating in stage I. Even in front of the same grain boundary, the blocking effect varies for different cracks. To investigate this behaviour systematically focused ion beam (FIB) initiated cracks were used. By this method of artificial crack initiation the crack parameters like crack length and distance to the obstacle can be varied separately. Additionally special grain boundaries can be selected after a microstructural characterisation by electron backscatter diffraction (EBSD). Finally FIB tomography helps to understand the process how a crack overcomes a grain boundary
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Hanford Tank 241-S-112 Residual Waste Composition and Leach Test Data
This report presents the results of laboratory characterization and testing of two samples (designated 20406 and 20407) of residual waste collected from tank S-112 after final waste retrieval. These studies were completed to characterize the residual waste and assess the leachability of contami¬nants from the solids. This is the first report from this PNNL project to describe the composition and leach test data for residual waste from a salt cake tank. All previous PNNL reports (Cantrell et al. 2008; Deutsch et al. 2006, 2007a, 2007b, 2007c) describing contaminant release models, and characterization and testing results for residual waste in single-shell tanks were based on samples from sludge tanks
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Rhenium Uptake, as Analogue for Tc-99, by Steel Corrosion Products
Static batch experiments were used to examine the sorption of dissolved perrhenate [Re(VII)], as a surrogate for pertechnetate [Tc(VII)], on corrosion products of A-516 carbon steel coupons contacted with synthetic groundwater or dilute water. After 109 days of contact time, the concentration of dissolved Re(VII) in the synthetic groundwater matrix decreased by approximately 26%; the dilute water matrix experienced a 99% decrease in dissolved Re(VII) over the same time period. Bulk XRD results for the corroded steel coupons showed that the corrosion products consisted primarily of maghemite, lepidocrocite, and goethite. Analyses of the coupons by SEM/EDS indicated that Re was present with the morphologically complex assemblages of Fe oxide/hydroxide corrosion products for samples spiked with the highest dissolved Re(VII) concentration (1.0 mmol/L) used for these experiments. Analyses of corroded steel coupons contacted with solutions containing 1.0 mmol/L Re(VII) by synchrotron-based methods confirmed the presence of Re sorbed with the corrosion product on the steel coupons. Analyses showed that the Re sorbed on these corroded coupons was in the +7 oxidation state, suggesting that the Re(VII) uptake mechanism did not involve reduction of Re to a lower oxidation state, such as +4. The results of our studies using Re(VII) as an analogue for Tc(VII)-99 suggest that Tc(VII)-99 would also be sorbed with steel corrosion products and that the inventory of Tc(VII)-99 released from breached waste packages would be lower than what is now conservatively estimated
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Hanford Tank 241-C-103 Residual Waste Contaminant Release Models and Supporting Data
This report tabulates data generated by laboratory characterization and testing of three samples collected from tank C-103. The data presented here will form the basis for a release model that will be developed for tank C-103. These release models are being developed to support the tank risk assessments performed by CH2M HILL Hanford Group, Inc. for DOE
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Hanford Tanks 241-C-202 and 241-C-203 Residual Waste Contaminant Release Models and Supporting Data
As directed by Congress, the U. S. Department of Energy (DOE) established the Office of River Protection in 1998 to manage DOE's largest, most complex environmental cleanup project – retrieval of radioactive waste from Hanford tanks for treatment and eventual disposal. Sixty percent by volume of the nation's high-level radioactive waste is stored at Hanford in aging deteriorating tanks. If not cleaned up, this waste is a threat to the Columbia River and the Pacific Northwest. CH2M Hill Hanford Group, Inc., is the Office of River Protection's prime contractor responsible for the storage, retrieval, and disposal of Hanford's tank waste. As part of this effort, CH2M HILL Hanford Group, Inc. contracted with Pacific Northwest National Laboratory (PNNL) to develop release models for key contaminants that are present in residual sludge remaining after closure of Hanford Tanks 241-C-203 (C-203) and 241-C-204 (C-204). The release models were developed from data generated by laboratory characterization and testing of samples from these two tanks. These release models are being developed to support the tank closure risk assessments performed by CH2M HILL Hanford Group, Inc., for DOE
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Characterization of Vadose Zone Sediment: Borehole 299-E33-45 Near BX-102 in the B-BX-BY Waste Management Area
This report was revised in September 2008 to remove acid-extractable sodium data from Table 4.22. The data was removed due to potential contamination introduced during the acid extraction process. The remaining text is unchanged from the original report issued in 2002. The overall goal of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities. To meet this goal, CH2M HILL Hanford Group, Inc., asked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediments from within Waste Management Area B-BX-BY. This report is the first in a series of four reports to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from borehole 299-E33-45 installed northeast of tank BX-102
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Characterization of Vadose Zone Sediment: RCRA Borehole 299-E33-338 Located Near the B-BX-BY Waste Management Area
This report was revised in September 2008 to remove acid-extractable sodium data from Table 4.8. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in June 2003. The overall goals of the of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., are: 1) to define risks from past and future single-shell tank farm activities, 2) to identify and evaluate the efficacy of interim measures, and 3) to aid via collection of geotechnical information and data, future decisions that must be made by the U.S. Department of Energy (DOE) regarding the near-term operations, future waste retrieval, and final closure activities for the single-shell tank waste management areas. For a more complete discussion of the goals of the Tank Farm Vadose Zone Project, see the overall work plan, Phase 1 RCRA Facility Investigation/Corrective Measures Study Work Plan for the Single-Shell Tank Waste Management Areas (DOE 1999). Specific details on the rationale for activities performed at the B-BX-BY tank farm waste management area are found in CH2M HILL (2000)
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Characterization of Vadose Zone Sediment: Borehole 299-E33-46 Near B 110 in the B BX-BY Waste Management Area
This report was revised in September 2008 to remove acid-ectractable sodium data from Table 4.17. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in December 2002. The overall goal of the of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities. To meet this goal, CH2M HILL Hanford Group, Inc., asked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediment from within the B-BX-BY Waste Management Area. This report is the third in a series of three reports to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from a borehole installed approximately 4.5 m (15 ft) northeast of tank B- 110 (borehole 299-E33-46)
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