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Galvanic corrosion study of container materials using zero resistance ammeter

Description: Galvanic corrosion behavior of A 516 steel separately coupled to six different corrosion-resistant alloys was investigated in an acidic brine (pHa2.70) at 30{degree}C 60{degree}C and 80{degree}C using zero resistance ammeter technique. The corrosion-resistant alloys include Alloys 825, G-3, G-30, C-4 and C-22; and Ti Grade-12, which were coupled to A 516 steel at an anode-to- cathode area ratio of one. The galvanic current and galvanic potential were measured as a function of time at all three temperatures. Optical microscopic examination was also performed on all tested specimens to evaluate the extent of surface degradation due to galvanic coupling. The overall results are presented in this paper.
Date: November 1, 1997
Creator: Roy, A. K., LLNL
Partner: UNT Libraries Government Documents Department

Effect of environmental variables on localized corrosion of high-performance container materials

Description: Electrochemical cyclic potentiodynamic polarization (CPP) experiments were performed on several candidate high-performance waste package container materials to evaluate their susceptibility to localized corrosion in aqueous environments relevant to the potential underground high-level nuclear waste repository. This paper presents the results of this study showing the effects of chloride ion (Cl) concentrations, pH, temperature, and electrochemical potential scan rate on the pitting corrosion behavior of these materials.
Date: January 1, 1997
Creator: Roy, A.K.; Fleming, D.L. & Lum, B.Y.
Partner: UNT Libraries Government Documents Department

Effect of chloride concentration and pH on pitting corrosion of waste package container materials

Description: Electrochemical cyclic potentiodynamic polarization experiments were performed on several candidate waste package container materials to evaluate their susceptibility to pitting corrosion at 90 degrees C in aqueous environments relevant to the potential underground high-level nuclear waste repository. Results indicate that of all the materials tested, Alloy C-22 and Ti Grade-12 exhibited the maximum corrosion resistance, showing no pitting or observable corrosion in any environment tested. Efforts were also made to study the effect of chloride ion concentration and pH on the measured corrosion potential (Ecorr), critical pitting and protection potential values.
Date: December 1, 1996
Creator: Roy, A.K.; Fleming, D.L. & Gordon, S.R.
Partner: UNT Libraries Government Documents Department

Engineered materials characterization report for the Yucca Mountain Site Characterization Project. Volume 2, Design data

Description: This is Volume 2 of the Engineered Materials Characterization Report which presents the design data for candidate materials needed in fabricating different components for both large and medium multi-purpose canister (MPC) disposal containers, waste packages for containing uncanistered spent fuel (UCF), and defense high-level waste (HLW) glass disposal containers. The UCF waste package consists of a disposal container with a basket therein. It is assumed that the waste packages will incorporate all-metallic multibarrier disposal containers to accommodate medium and large MPCs, ULCF, and HLW glass canisters. Unless otherwise specified, the disposal container designs incorporate an outer corrosion-allowance metal barrier over an inner corrosion-resistant metal barrier. The corrosion-allowance barrier, which will be thicker than the inner corrosion-resistant barrier, is designed to undergo corrosion-induced degradation at a very low rate, thus providing the inner barrier protection from the near-field environment for a prolonged service period.
Date: August 1, 1995
Creator: Konynenburg, R.A.; McCright, R.D.; Roy, A.K. & Jones, D.A.
Partner: UNT Libraries Government Documents Department

Status report: stress corrosion cracking of Ni-base and Ti alloys milestone No.wp267M4

Description: Susceptibility to stress corrosion cracking (SCC) of two candidate alloys for the inner container of the multibarrier nuclear waste package was evaluated by using wedge-loaded, precracked, double-cantilever-beam (DCB) specimens and the slow-strain-rate (SSR) test technique. Materials tested included Alloy C-22 and Ti Gr-12. A deaerated 90 C acidic brine (pH {approx} 2.70) containing 5 weight percent NaCl was used as the test environment. Both DCB and SSR tensile specimens were machined from mill-annealed plate materials. No additional thermal treatments were given to these specimens prior to their being exposed to the test solution. The DCB testing was performed for periods ranging from one through eight months. The initial and final stress intensity factor (K{sub I} and K{sub f}) values were calculated using a standard fracture-mechanics equation. Fractographic evaluation of the broken DCB specimens was performed by using scanning electron microscopy (SEM) to analyze the characteristics of failures.
Date: December 1, 1998
Creator: Roy, A K
Partner: UNT Libraries Government Documents Department

Electrochemical corrosion studies of container materials in repository-relevant environments

Description: The Office of Civilian Radioactive Waste Management (OCRWM) of the United States Department of Energy (USDOE) is evaluating Yucca Mountain in southern Nevada to determine its suitability as a site for a mined geologic disposal system for the disposal of spent fuel and high-level nuclear waste. Framatome Cogema Fuels (FCF), as a part of the Management and Operating (M&O) team in support of the Yucca Mountain Site Characterization Project (YAD), is responsible for designing and developing the waste package for this potential repository. As part of this effort, Lawrence Livermore National Laboratory (LLNL), also a member of the M&O team is responsible for testing materials and developing models for the materials to be used in the waste package. Based on a literature review of the anticipated degradation modes that may occur under the repository-relevant environmental conditions, LLNL has identified a large number of engineering materials for the various components of the waste package. One step in evaluating the performance of these materials is to conduct preliminary tests under these repository-relevant environmental conditions. This report is aimed at presenting the results of scoping electrochemical cyclic potentiodynamic polarization (CPP) experiments using nine candidate waste package container materials in various environments.
Date: December 12, 1995
Creator: Roy, A. K.; Henshall, G. A. & McCright, R. D.
Partner: UNT Libraries Government Documents Department

Localized corrosion of container materials under potentiodynamic and potentiostatic controls

Description: Potentiodynamic and potentiostatic polarization experiments were performed on ten candidate waste package container materials to evaluate their pitting tendency at ambient and elevated temperatures in aqueous environments relevant to the potential underground nuclear waste repository. Results indicate that of all the materials tested, Alloys G-30, C-4 and C-22, and Ti Gr-12 exhibited the maximum corrosion resistance, showing no pitting or observable dissolution in any environment tested. These experimental results will be used in identifying a group of potential container materials having the desired corrosion resistance.
Date: May 1, 1996
Creator: Roy, A. K.; Fleming, D. L. & Gordon, S. R.
Partner: UNT Libraries Government Documents Department

Stress corrosion cracking of Fe-Ni-Cr-Mo, Ni-Cr-Mo and Ti alloys in 90{degrees}C acidic brince

Description: Susceptibility to stress corrosion cracking (SCC) of candidate materials for the inner container of the multi-barrier nuclear waste package was evaluated by using wedge-loaded precracked double- cantilever-beam (DCB) specimens in deaerated acidic brine (pH at 2.70) at 90{degrees}C. Materials tested include Alloys 825, G-30, C-4, 625 and C-22; and Ti Grade- 12. Duplicate specimen of each material was loaded at different initial stress intensity factor (K) values ranging between 23 and 46 ksi/in. Both metallography and compliance method were used to determine the final crack length. The final stress intensity for SCC (K{sup ISCC}) was computed from the measured final wedge load and the average crack length. The results indicate that in general, the final crack length measured by metallography and compliance was very close to each other, thus, providing very similar K{sup ISCC} values. While tests are still ongoing, the preliminary results suggest that, compared to other five alloys tested, Alloy 825 may exhibit the maximum tendency to SCC.
Date: November 1, 1997
Creator: Roy, A.K.; Fleming, D.L. & Lum, B.Y.
Partner: UNT Libraries Government Documents Department

Electrochemical and metallographic evaluation of alloys C-22 and 625

Description: Electrochemical cyclic potentiodynamic polarization (CPP) experiments were performed on Alloys C-22 and 625 to evaluate their susceptibility to localized corrosion in acidic brines of various salt content at 90{degrees}C. The microstructures of both tested and untested specimen`s were evaluated by optical microscopy. This paper presents the results showing the effect of chloride ion concentration on the pitting and crevice corrosion behavior of these alloys, and the relationship of the observed microstructures to the resulting surface degradation modes.
Date: May 1, 1997
Creator: Roy, A. K.; Fleming, D. L. & Lum, B. Y.
Partner: UNT Libraries Government Documents Department

Engineered materials characterization report for the Yucca Mountain Site Characterization Project. Volume 3: Corrosion and data modeling

Description: This three-volume report serves several purposes. The first volume provides an introduction to the engineered materials effort for the Yucca Mountain Site Characterization Project. It defines terms and outlines the history of selection and characterization of these materials. A summary of the recent engineered barrier materials characterization workshop is presented, and the current candidate materials are listed. The second volume tabulates design data for engineered materials, and the third volume is devoted to corrosion data, radiation effects on corrosion, and corrosion modeling. The second and third volumes are intended to be evolving documents, to which new data will be added as they become available from additional studies. The initial version of Volume 3 is devoted to information currently available for environments most similar to those expected in the potential Yucca Mountain repository. This is volume three.
Date: August 1, 1995
Creator: Van Konynenburg, R.A.; McCright, R.D.; Roy, A.K. & Jones, D.A.
Partner: UNT Libraries Government Documents Department

Effect of controlled potential on SCC of nuclear waste package container materials

Description: The slow-strain-rate (SSR) test technique was used to evaluate the susceptibility of Titanium (Ti) Gr-7 (UNS R52400) and Ti Gr-12 (UNS R53400) to stress corrosion cracking (SCC). Ti Gr-7 and Ti Gr-12 are two candidate container materials for the multi-barrier package for nuclear waste. The tests were done in a deaerated 90 C acidic brine (pH {approx} 2.7) containing 5 weight percent (wt%) sodium chloride (NaCl) using a strain rate of 3.3 x 10{sup -6} sec{sup -1}. Before being tested in the acidic brine, specimens of each alloy were pulled inside the test chamber in the dry condition at ambient temperature. Then while in the test solution, specimens were strained under different cathodic (negative) controlled electrochemical potentials. These controlled potentials were selected based on the corrosion potential measured in the test solution before the specimens were strained. Results indicate that the times to failure (TTF) for Ti Gr-12 were much shorter than those for Ti Gr-7. Furthermore, as the applied potential became more cathodic, Ti Gr-12 showed reduced ductility in terms of percent reduction in area (%RA) and true fracture stress ({sigma}{sub f}). In addition, TTF and percent elongation (%El) reached the minimum values when Ti Gr-12 was tested under an impressed potential of -1162 mV. However, for Ti Gr-7, all these ductility parameters were not significantly influenced by the changes in applied potential. In general, the results of hydrogen analysis by secondary ion mass spectrometry (SIMS) showed increased hydrogen concentration at more cathodic controlled potentials. Optical microscopy and scanning electron microscopy (SEM) were used to evaluate the morphology of cracking both at the primary fracture face and the secondary cracks along the gage section of the broken tensile specimen. Transgranular secondary cracks were observed in both alloys possibly resulting from the formation of brittle titanium hydrides due to cathodic ...
Date: August 1, 1999
Creator: Lum, B Y; Roy, A K & Spragge, M K
Partner: UNT Libraries Government Documents Department

Localized corrosion of candidate container materials in ferric chloride solutions

Description: Localized corrosion behavior of candidate inner and outer container materials of currently-designed nuclear waste package was evaluated in aqueous solutions of various concentrations of ferric chloride (FeCl{sub 3}) at 30 C, 60 C and 90 C using the electrochemical cyclic potentiodynamic polarization (CPP) technique. Materials tested include A 5 16 carbon steel and high-performance alloys 825, G-3, G-30, C-4, 625. C-22, and Ti Gr-12. A 516 steel suffered from severe general and localized attack including pitting and crevice corrosion. High-nickel alloys 825 and G-3 also became susceptible to severe pitting and crevice corrosion. The extent of localized attack was less pronounced in alloys G-30 and C-4. Alloy 625 experienced severe surface degradation including general corrosion, crevice corrosion and intergranular attack. In contrast, only a slight crevice corrosion tendency was observed with nickel-base alloy C-22 in solutions containing higher concentrations of FeCl{sub 3} at 60 C and 90 C. Ti Gr-12 was immune to localized attack in all tested environments. The test solutions showed significant amount of precipitated particles during and after testing especially at higher temperatures.
Date: October 1, 1998
Creator: Fleming, D L; Lum, B Y & Roy, A K
Partner: UNT Libraries Government Documents Department

Stress corrosion cracking of Ni-base and Ti alloys under controlled potential

Description: Susceptibility to stress corrosion cracking (SCC) of alloy C-22 and Ti Gr-12, two candidate alloys for the inner-container of the multi-barrier nuclear waste package, was evaluated by using the slow-strain-rate (SSR) test technique in a deaerated acidic brine (pH {approx} 2.70) at 90 C. The strain rate used was 3.3 x 10{sup {minus}6} sec{sup {minus}1}. Prior to being tested in the acidic brine, specimens of each alloy were pulled inside the test chamber in the dry condition at room temperature (RT). Then specimens were exposed to the test solution while being strained under different controlled electrochemical potentials. The magnitude of the controlled potential was selected based on the corrosion potential measured in the test solution prior to straining of the specimen. Results indicate that, for Ti Gr-12, the times to failure were significantly shorter compared to those for alloy C-22. Furthermore, Ti Gr-12 showed reduced ductility in terms of percent reduction in area and true fracture stress, as the controlled potential became more cathodic. Results also indicate that the time-to-failure and percent elongation reached the minimum values when Ti Gr-12 was tested under impressed potential of {minus}1162 mV. Finally, metallographic examination was performed to evaluate the primary fracture, and the secondary cracking, if any, along the gage section of the broken tensile specimen.
Date: October 22, 1998
Creator: Estill, J C; Gordon, S R; Logeteta, L F & Roy, A K
Partner: UNT Libraries Government Documents Department

Engineered materials characterization report for the Yucca Mountain Site Characterization Project. Volume 1, Introduction, history, and current candidates

Description: The purpose of the Yucca Mountain Site Characterization Project is to evaluate Yucca Mountain for its suitability as a potential site for the nation`s first high-level nuclear waste repository. As part of this effort, Lawrence Livermore National Laboratory (LLNL) has been occupied for a number of years with developing and evaluating the performance of waste packages for the potential repository. In recent years this work has been carried out under the guidance of and in collaboration with the Management and Operating contractor for the Civilian Radioactive Waste Management System, TRW Environmental Safety Systems, Inc., which in turn reports to the Office of Civilian Radioactive Waste Management of the US Department of Energy. This report summarizes the history of the selection and characterization of materials to be used in the engineered barrier system for the potential repository at Yucca Mountain, describes the current candidate materials, presents a compilation of their properties, and summarizes available corrosion data and modeling. The term ``engineered materials`` is intended to distinguish those materials that are used as part of the engineered barrier system from the natural, geologic materials of the site.
Date: August 1, 1995
Creator: Van Konynenburg, R.A.; McCright, R.D.; Roy, A.K. & Jones, D.A.
Partner: UNT Libraries Government Documents Department

Galvanic corrosion-effect of environmental and experimental variables

Description: Galvanic corrosion behavior of A 516 steel coupled to alloy C-22 and Ti Gr-12, respectively was evaluated in an acidic brine (pH {approx} 2.75) at 30 C, 60 C and 80 C using zero resistance ammeter method. A limited number of experiments were also performed in a neutral brine involving A 516 steel/alloy C-22 couple. The steady-state galvanic current and galvanic potential were measured as functions of anode-to-cathode (A/C) area ratio and electrode distance. Results indicate that the galvanic current was gradually reduced as the A/C area ratio was increased. No systematic trend on the effect of A/C area ratio on the galvanic potential was observed. Also, no significant effect of electrode distance on the galvanic current and galvanic potential was evident. In general, increased galvanic current was noticed with increasing temperature. The limited data obtained in the neutral brine indicate that the galvanic current was reduced in this environment, compared to that in the acidic brine. Optical microscopic examination was performed on all tested specimens to evaluate the extent of surface damage resulting from galvanic interaction. A 516 steel suffered from general corrosion and crevice corrosion in all environments tested. Very light crevice corrosion mark was observed with alloy C-22 and Ti Gr-12 in the acidic brine at 60 C and 80 C. However, this mark appears to be a surface discoloration and no actual crevice was detected.
Date: November 1, 1998
Creator: Fleming, D L; Lum, B Y & Roy, A K
Partner: UNT Libraries Government Documents Department

SCC evaluation of candidate container alloys by DCB method

Description: The authors use a solid mechanics approach to investigate hydride formation and cracking in zirconium-niobium alloys used in the pressure tubes of CANDU nuclear reactors. In this approach, the forming hydride is assumed to be purely elastic and its volume dilation is accommodated by elasto-plastic deformation of the surrounding matrix material. The energetics of the hydride formation is revisited and the terminal solid solubility of hydrogen in solution is defined on the basis of the total elasto-plastic work done on the system by the forming hydride and the external loads. Hydrogen diffusion and probabilistic hydride formation coupled with the material deformation are modeled at a blunting crack tip under plane strain loading. A full transient finite element analysis allows for numerical monitoring of the development and expansion of the hydride zone as the externally applied loads increase. Using a Griffith fracture criterion for fracture limitiation, the reduced fracture resistance of the alloy can be predicted and the factors affecting fracture toughness quantified.
Date: September 24, 1999
Creator: Roy, A.K.; Freeman, D.C.; Lum, B.Y. & Spragge, M.K.
Partner: UNT Libraries Government Documents Department