Effect of Chloride on Environmentally Assisted Cracking of Low Alloy Steels in Oxygenated High-Temperature Water — General Corrosion

Herbst, Matthias; Roth, Armin; Nowak, E. J.; Ilg, U.

doi:10.1007/978-3-319-48760-1_51

Cited by 3 publications

(7 citation statements)

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“…Similar observations on the effect of chloride transients with the RPV steel D (0.007 % S, low DSA susceptibility, lowest EAC susceptibility in PSI investigations) were obtained by M. Herbst et al [26,27] and Herter et al [28] in a very limited number of tests at slightly lower ECPs. In case of dormant cracks under pure constant load, no acceleration of SCC was observed even for prolonged and severe chloride transients of 50 ppb [27,28] and up to 150 ppb [28]. A single partial un-/reloading cycle immediately induced fast SCC during chloride transients with similar CGRs as in the PSI investigations.…”

Section: Nwc Environmentsupporting

confidence: 83%

“…In HWC environment (no potential gradient in crack crevice), the mass transport is only diffusion-driven with little enrichment and the situation with regard to transients is thus quite symmetric ( Figure 21). These observations were confirmed by micro-sampling experiments [27,35,36]. With bulk chloride contents of up to 100 ppb and an enrichment factor of 20 to 30, there is only a very slight acidification of the crack-tip environment (pH-shift at temperature of 1 to 1.5 units at maximum).…”

Section: Mechanistic Interpretationsupporting

confidence: 53%

“…After returning to high-purity water, the SCC CGRs quickly declined, but were then further growing with a slow SCC rate in several cases. In case of a sharp and very slowly growing crack under pure constant load, acceleration of SCC already occurred 3 hours after the addition of 50 ppb of chloride [27]. On the other hand, 100 h after a 100 h chloride transient of 50 ppb in case of a dormant crack, three partial un-& re-loading cycles did not induce accelerated SCC crack growth [28], indicating that the original crack crevice chemistry already had re-established at this time, as expected.…”

Section: Nwc Environmentmentioning

confidence: 99%

“…Chloride seems to reversibly adsorb on/in the oxide film and to alter the oxide film properties [27], which either could result in lower film rupture strains, less protective oxide layers or even in an (electro-)chemical break-down of the film. Thinner oxide films were observed in chloride containing hightemperature water [27], which facilitates film rupture by plastic slip at smaller strains. Stronger localized thinning of oxide film was observed for long exposure times in high chloride environments including pitting [27].…”

Section: Mechanistic Interpretationmentioning

confidence: 99%

“…Thinner oxide films were observed in chloride containing hightemperature water [27], which facilitates film rupture by plastic slip at smaller strains. Stronger localized thinning of oxide film was observed for long exposure times in high chloride environments including pitting [27]. These effects increase the oxide film rupture frequency and thus crack growth rate.…”

Section: Mechanistic Interpretationmentioning

confidence: 99%

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The influence of ppb levels of chloride impurities on the stress corrosion crack growth behaviour of low-alloy steels under simulated boiling water reactor conditions

Seifert

Ritter

2016

Corrosion Science

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The effect of chloride on the stress corrosion crack (SCC) growth behaviour in low-alloy reactor pressure vessel steels was evaluated under simulated boiling water reactor conditions. In normal water chemistry environment, ppb-levels of chloride may result in fast SCC after rather short incubation periods of few hours. After moderate and short-term chloride transients, the SCC crack growth rates return to the same very low high-purity water values within few 100 hours. Potential long-term (memory) effects on SCC crack growth cannot be excluded after severe and prolonged chloride transients. The chloride tolerance for SCC in hydrogen water chemistry environment is much higher.

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Section: Nwc Environmentsupporting

confidence: 83%

Section: Mechanistic Interpretationsupporting

confidence: 53%

Section: Nwc Environmentmentioning

confidence: 99%

Section: Mechanistic Interpretationmentioning

confidence: 99%

Section: Mechanistic Interpretationmentioning

confidence: 99%

See 3 more Smart Citations

The influence of ppb levels of chloride impurities on the stress corrosion crack growth behaviour of low-alloy steels under simulated boiling water reactor conditions

Seifert

Ritter

2016

Corrosion Science

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Contribution of research to the understanding and mitigation of environmentally assisted cracking in structural components of light water reactors

Tice

2017

Corrosion Engineering, Science and Technology

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Environmentally assisted cracking (EAC) is a potential threat to the safety and integrity of water-wetted components in operating water-cooled nuclear power plants. Two forms of EAC are commonly distinguished, depending on the form of loading contributing to damage: stress corrosion cracking (SCC) and corrosion fatigue. A number of instances of in-service degradation due to EAC have occurred in operating plants worldwide, often leading to unplanned plant outages. Understanding the causes of EAC is essential to minimise the loss of plant availability due to its occurrence and to avoid the possibility of catastrophic failure, for example, if a crack grew to a critical size in a major pressure boundary component. This paper will describe some examples of these phenomena in the main materials of construction of pressure boundary and other critical components in pressurised and boiling water reactors (BWRs). Over the last several decades, substantial research programmes have been carried out in a number of laboratories worldwide, aimed at further understanding of the processes leading to EAC to manage occurrences in plant and minimise future failures. Selected areas of research on EAC in light water reactor environments are discussed. Corrosion fatigue in low-alloy pressure vessel steels was the subject of considerable attention in the 1980s and early 1990s because of its potential threat to pressure vessel integrity and the publication of data, suggesting that there is a major influence of environment on fatigue crack growth in some laboratory tests. The author's research provided insight into the conditions under which the major environmental effects occur and contributed to the development of an ASME Code Case for pressurised water reactor (PWR) conditions which provided a means of screening based on steel sulphur content and loading conditions. More recently, the research focus in this area has moved to austenitic stainless steels, again providing support to Code Case development and furthering mechanistic understanding. A recent review of knowledge gaps for EPRI provides a basis for future research on environmentally assisted fatigue and will inform the development of new assessment methodologies. A key area of the current study concerns differences in loading conditions between specimens in laboratory tests and plant components subject to transient loading. In the case of SCC, stainless steels have shown the greatest propensity to cracking in BWRs, while Alloy 600 has been a major cause of in-service failures in PWRs, both on the primary side, as recognised by Coriou in the early 1960s, and in secondary environments where a number of different corrosionrelated failure processes have been identified. High-strength alloys, such as Alloy X-750 used for fastener applications, have also caused failures in both reactor types. For austenitic materials, SCC susceptibility is enhanced by irradiation, resulting in failures in core internals components. Ferritic stainless steels also undergo SCC under some specific circums...

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Impact of Chloride on the Environmentally-Assisted Crack Initiation Behaviour of Low-Alloy Steel under Boiling Water Reactor Conditions

Ritter

Seifert

2022

CMD

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Low-alloy reactor pressure vessel steels have a rather low susceptibility to stress corrosion cracking (SCC) in a boiling water reactor (BWR) environment if the high-temperature water contains no anionic impurities. Recent investigations revealed that under oxidizing BWR normal water chemistry (NWC) conditions extremely small amounts of chloride, can cause very high SCC growth rates in these materials. Therefore, the effect of continuous and temporary chloride additions on the crack initiation behaviour was explored by a series of constant extension rate tensile (CERT) and constant load tests in high-temperature water. In an NWC environment, containing ≥2 ppb of chloride, strain-induced corrosion cracking (SICC) initiation occurred briefly after the onset of plastic yielding and at much smaller strains than in high-purity water. On the other hand, under reducing hydrogen water chemistry conditions with up to 700 ppb chloride, no SICC was detected up to very high strains. CERT experiments, with moderate short-term chloride transients before and during the loading, showed that even serious mechanical loading transients, one day after returning to high-purity water, did not result in early SICC initiation.

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Effect of Chloride on Environmentally Assisted Cracking of Low Alloy Steels in Oxygenated High-Temperature Water — General Corrosion

Cited by 3 publications

References 4 publications

The influence of ppb levels of chloride impurities on the stress corrosion crack growth behaviour of low-alloy steels under simulated boiling water reactor conditions

The influence of ppb levels of chloride impurities on the stress corrosion crack growth behaviour of low-alloy steels under simulated boiling water reactor conditions

Contribution of research to the understanding and mitigation of environmentally assisted cracking in structural components of light water reactors

Impact of Chloride on the Environmentally-Assisted Crack Initiation Behaviour of Low-Alloy Steel under Boiling Water Reactor Conditions

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