Primary Water SCC Understanding and Characterization Through Fundamental Testing in the Vicinity of the Nickel/Nickel Oxide Phase Transition

Morton, David Alexander Vodden; Attanasio, Steven A.; Young, George A.

doi:10.2172/821310

Cited by 24 publications

(14 citation statements)

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“…The only significant difference that was observed between as-machined corrosion coupons and the tensile specimen oxide films was that in addition to outer layer spinel crystals, NiO was also observed in the outer layer, Figure 18. This difference was expected since the corrosion coupon study was performed well into the nickel metal regime whereas SCC initiation tests were performed at a hydrogen level corresponding to the Ni/NiO phase transition to maximize the SCC susceptibility [2]. …”

Section: Scc Initiation Specimensmentioning

confidence: 99%

“…Many PWSCC key parameter dependencies suggest that corrosion/oxidation is a fundamental subprocess in the overall mechanism. PWSCC, for example, exhibits a maximum in susceptibility in a narrow ~ 100 mV corrosion potential window about the Ni/NiO phase transition [2], PWSCC shows a significant Arrhenius temperature thermal activation energy (Q) of ~33 kcal/mol [3] and chromium additions are known to be beneficial. Recent laboratory studies [4,5] have been performed to characterize the morphology and composition of oxides that form on nickel based alloys in primary water and to discern SCC mechanistic implications.…”

Section: Introductionmentioning

confidence: 99%

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Nickel Alloy Primary Water Bulk Surface and SCC Corrosion Film Analytical Characterization and SCC Mechanistic Implications

Morton¹,

Lewis²,

Hanson³

et al. 2007

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Section: Scc Initiation Specimensmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nickel Alloy Primary Water Bulk Surface and SCC Corrosion Film Analytical Characterization and SCC Mechanistic Implications

Morton¹,

Lewis²,

Hanson³

et al. 2007

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“…The effect of dissolved hydrogen level on CGRs in Ni alloys has been investigated by Morton et al in SCC studies. 64 Several conclusions wee reached. A change in hydrogen level alters the electrochemical potential, and the growth rate exhibits a maximum at potentials in proximity to the Ni/NiO phase transition.…”

Section: Effect Of Water Chemistrymentioning

confidence: 96%

Crack Growth Rates of Nickel Alloy Welds in a PWR Environment

Alexandreanu

Chopra

Shack

2006

Volume 1: Codes and Standards

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In light water reactors (LWRs), vessel internal components made of nickel-base alloys are susceptible to environmentally assisted cracking. A better understanding of the causes and mechanisms of this cracking may permit less conservative estimates of damage accumulation and requirements on inspection intervals. A program is being conducted at Argonne National Laboratory to evaluate the resistance of Ni alloys and their welds to environmentally assisted cracking in simulated LWR coolant environments. This report presents crack growth rate (CGR) results for Alloy 182 shielded-metal-arc weld metal in a simulated pressurized water reactor (PWR) environment at 320°C. Crack growth tests were conducted on 1-T compact tension specimens with different weld orientations from both double-J and deep-groove welds. The results indicate little or no environmental enhancement of fatigue CGRs of Alloy 182 weld metal in the PWR environment. The CGRs of Alloy 182 in the PWR environment are a factor of ≈5 higher than those of Alloy 600 in air under the same loading conditions. The stress corrosion cracking for the Alloy 182 weld is close to the average behavior of Alloy 600 in the PWR environment. The weld orientation was found to have a profound effect on the magnitude of crack growth: cracking was found to propagate faster along the dendrites than across them. The existing CGR data for Ni-alloy weld metals have been compiled and evaluated to establish the effects of key material, loading, and environmental parameters on CGRs in PWR environments. The results from the present study are compared with the existing CGR data for Ni-alloy welds to determine the relative susceptibility of the specific Ni-alloy weld to environmentally enhanced cracking. iv Intentionally Left BlankForeword v This report presents crack growth rate data and the results of the corresponding fracture surface and metallographic examinations from cyclic loading and primary water stress-corrosion cracking (PWSCC) tests of two nickel-base Alloy 182 (A182) weldments, which are typical of those used in vessel penetrations and piping butt welds in nuclear power plants. The effect of crack orientation with respect to dendrite orientation is the most significant variable investigated in this study. However, this report also includes a review of data from several laboratories, which describes the effects of material composition, loading characteristics, and chemistry of the aqueous environment. The main conclusion is that the PWSCC growth rates described for A182 specimens in this report are comparable to the crack growth rates that characterize the performance of Alloy 600 (A600).This report is the first in a series documenting the results of crack growth rate testing in vessel head penetration materials, focusing on the weld metals, A182 and A152, and including results of some tests of the base metals, A600 and (eventually) A690. The results presented in this report were obtained in tests of a laboratory-fabricated, shielded metal arc welding deposit of A182. ...

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“…While the mechanistic origin is unclear, there are consistent data showing that CGRs of Ni-base alloys peak near the Ni/NiO phase boundary. [35][36][37] Thus, to isolate the effect of temperature, the tests are conducted so that the difference between the corrosion potential of the specimen and that of the Ni/NiO phase transition was maintained approximately constant. The Ni/NiO phase transition is very close to the H 2 /H 2 O phase transition, and the latter controls the corrosion potential of the simulated primary water environment.…”

Section: Primary Water Environmentmentioning

confidence: 99%

“…However, the corrosion potential for the Bechtel Bettis tests conducted at 360°C (680°F) with 150 cc/kg hydrogen was farther removed from the Ni/NiO phase transition than in the case of the 338°C (640°F) tests with 40-60 cc/kg hydrogen. As such, since the CGRs are highest near the Ni/NiO phase transition and decrease as the potential deviates from this transition, 36,37 the CGRs in the 360°C tests may have been reduced because of the high dissolved hydrogen levels. Thus, the actual activation energy for the Bechtel Bettis data may be somewhat higher than that determined in Fig.…”

Section: Activation Energy For Scc Crack Growthmentioning

confidence: 99%

Crack growth rates and metallographic examinations of Alloy 600 and Alloy 82/182 from field components and laboratory materials tested in PWR environments.

Alexandreanu¹,

Chopra²,

Shack³

2008

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In light water reactors, components made of nickel-base alloys are susceptible to environmentally assisted cracking. This report summarizes the crack growth rate results and related metallography for field and laboratory-procured Alloy 600 and its weld alloys tested in pressurized water reactor (PWR) environments. The report also presents crack growth rate (CGR) results for a shielded-metal-arc weld of Alloy 182 in a simulated PWR environment as a function of temperature between 290°C and 350°C. These data were used to determine the activation energy for crack growth in Alloy 182 welds. The tests were performed by measuring the changes in the stress corrosion CGR as the temperatures were varied during the test. The difference in electrochemical potential between the specimen and the Ni/NiO line was maintained constant at each temperature by adjusting the hydrogen overpressure on the water supply tank. The CGR data as a function of temperature yielded activation energies of 252 kJ/mol for a double-J weld and 189 kJ/mol for a deep-groove weld. These values are in good agreement with the data reported in the literature. The data reported here and those in the literature suggest that the average activation energy for Alloy 182 welds is on the order of 220-230 kJ/mol, higher than the 130 kJ/mol commonly used for Alloy 600. The consequences of using a larger value of activation energy for SCC CGR data analysis are discussed.iv This page is intentionally left blank. Foreword vThis report presents crack growth rate (CGR) data and the results of the corresponding fracture surface and metallographic examinations from cyclic loading and primary water stress-corrosion cracking (PWSCC) tests of two nickel-base Alloy 182 (A182) weldments. These weldments are typical of those used in vessel penetrations and piping butt welds in nuclear power plants. The effect of crack orientation with respect to dendrite orientation is the most significant variable investigated in this study. However, this report also compiles data from other laboratories that describe the effects of material composition, loading characteristics, and chemistry of the aqueous environment. The PWSCC growth rates described for the A182 specimens in the report are comparable to the CGR that characterize the performance of Alloy 600 (A600).This report is one of a series of reports documenting the results of CGR testing in vessel head penetration materials. This report focuses on the Alloy 82 (A82) and A182 weld metals. This report also presents results from tests of the A600 base metal. The researchers tested (1) a laboratory-fabricated, shieldedmetal-arc deposit of A182; (2) a weldment sample from the J-groove weld of a control rod drive mechanism nozzle from the Davis-Besse Nuclear Power Plant; and (3) a hot leg nozzle-to-safe end weld from the Virgil C. Summer Nuclear Station.

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Primary Water SCC Understanding and Characterization Through Fundamental Testing in the Vicinity of the Nickel/Nickel Oxide Phase Transition

Cited by 24 publications

References 1 publication

Nickel Alloy Primary Water Bulk Surface and SCC Corrosion Film Analytical Characterization and SCC Mechanistic Implications

Nickel Alloy Primary Water Bulk Surface and SCC Corrosion Film Analytical Characterization and SCC Mechanistic Implications

Crack Growth Rates of Nickel Alloy Welds in a PWR Environment

Crack growth rates and metallographic examinations of Alloy 600 and Alloy 82/182 from field components and laboratory materials tested in PWR environments.

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