Accelerated testing of stress corrosion crack initiation and growth of alloy 600 and alloy 690 in pressurized water reactor pwr is routinely conducted to reduce the time of the experiment on. Chloride stress corrosion cracking in austenitic stainless. Abstract the influence of dissolved hydrogen on primary water stress corrosion cracking pwscc of mill annealed alloy 600 was studied at temperatures ranging from 320 to 36012 and hydrogen contents ranging from 0 to 4 ppm using the slow strain rat. Because pwscc was not properly considered in vintage pressurized water. Introduction in the united states currently there are approximately 104 operating light water reactors. Alloy 600 is still in use in existing pressurized water reactor pwr. The earliest incidents of irradiation assisted stress corrosion cracking iascc in bwrs occurred during the early 1960s and were associated with cracking of type 304 stainless steel fuel cladding, where the driving forces for cracking were the increasing tensile hoop stress in the cladding due to the swelling fuel and the highly oxidizing conditions in the water. This type of corrosion is one of the primary lifelimiting degradation mechanisms of nickelbase alloy pressure boundary components, such as. While stress corrosion cracking scc is a major service life limiting mechanism for both pressurized water reactors pwrs and boiling water reactors bwrs, most of the corrosion research. Strainhardening may play an important role in the occurrence of intergranular scc. Stress corrosion cracking facts and how to reduce the.
In recent years, accidents of stress corrosion cracking scc in 316l ss pipes were reported in pwrs. Nuclear reactors nickel alloys primary water stress corrosion cracking. The impact of scc on a material usually falls between dry cracking and the fatigue threshold of that material. The crack growth rate cgr increased with increasing do content in the simulated pwr primary water. Extensive laboratory testing has shown that intergranular stress corrosion cracking igscc requires the presence of the following three key elements. Effects of chloride and oxygen on stress corrosion. This cracking can also occur when ammonia is intentionally added to process streams as a neutralizer by someone unaware of its potential effect on brass tubes. Steam generator sg drain nozzles on the cold leg side in a pressurized water reactor pwr have exhibited stress corrosion cracking scc. Iaea nuclear energy series stress corrosion cracking in light. Primary water stress corrosion cracking pwscc is an intergranular cracking. Affecting stress corrosion cracking in stainless steel piping in pressurized water reactors addressees all holders of an operating license or construction permit for a nuclear power pressurized water reactor pwr issued under title 10 of the code of federal regulations 10 cfr part 50. One of the main failure mechanisms that cause risks to pressurized water reactors pwr is the primary water stress corrosion cracking pwscc occurring in. It is especially important to avoid any mechanical tensile stress concentration, which will occur at sharp edges and notches.
Stress corrosion cracking of austenitic stainless steels 1011820 technical update, september 2005. Of these, 69 are pressurized water reactors pwrs and 35 are boiling water. How to reduce the risk of stress corrosion cracking scc the risk of stress corrosion cracking scc can be minimized through plant and equipment design. Effects of marine environments on stress corrosion.
Stress corrosion, also known as stress corrosion cracking, is a type of corrosion that occurs due to the simultaneous action of a corrodent and a sustained tensile stress. Primary water stress corrosion cracking pwscc of inconel 600 united states nuclear regulatory commission office of nuclear reactor regulation washington, d. Virtanen, stress corrosion cracking initiation and short crack growth behaviour in alloy 182 weld metal under simulated boiling water reactor hydrogen water chemistry conditions, in, 2016. Nrc staff actions to address primary water stress corrosion cracking in dissimilar metal butt welds the industry actions to develop and implement the mrp9 inspections allowed the nrc staff to pursue a process to codify requirements involving all stakeholders rather than to initiate other regulatory actions. Ammonia stress corrosion cracking is a form of stress corrosion cracking that commonly occurs in brass tubes in cooling water service that has been contaminated with ammonia due to biological growths or other contamination. The required tensile stresses may be in the form of directly applied stresses or in the form of residual. Primary water stress corrosion cracking of highchromium. The nuclear industry has developed several methods for mitigation of pwscc to prevent costly repairs to pressurized water reactor pwr components including surface stress improvement by peening. Stress corrosion crack growth tests of a cold worked nuclear grade 316l stainless steel were conducted in simulated pressurized water reactor pwr primary water environment containing various dissolved oxygen do contents but no dissolved hydrogen. Abstract the aging of water cooled and moderated nuclear steam supply systems inevitably has given rise to many material corrosion problems of which stress corrosion cracking scc is one of the mo. Stress corrosion cracking scc is the growth of crack formation in a corrosive environment. Primary water stress corrosion cracking pwscc of inconel 600. This alloy is wellknown to be susceptible to stress corrosion cracking. The goal of this work was to study the electrochemical corrosion behavior and scc susceptibility of alloy 182 weld in pwr primary water containing 25 cm 3 and 50 cm 3 h 2 kg h 2 o at.
Stress corrosion cracking growth of alloy 800ng in. Originally selected for its high corrosion resistance, it exhibited, after a long operation period, susceptibility to stress corrosion cracking scc in pwr. Stress corrosion crack scc initiation of three millannealed alloy 600 heats. Evaluation of laser peening for mitigation of primary. Summer in south carolina, the issue has become significant for the us pwr industry. Pdf evaluation of primary water stress corrosion cracking.
This cracking was found first in piping and then became a significant issue for reactor pressure vessel rpv internals and rpv nozzle welds including nickel welds. Shallow intergranular attack andor cracks were found on most highenergy grain boundaries. Uniform corrosion, flowaccelerated corrosion fac, pitting, stress corrosion cracking scc, environmentally assisted fatigue and hydrogen embrittlement can all affect the major components of pwrs, despite. Although the nickel base materials were different from the present study, there are similarities to. The nozzles were made of forged and annealed alloy 600 uns n06600 base material containing welds with.
A reactor pressure vessel rpv in a nuclear power plant is the pressure vessel containing the nuclear reactor coolant, core shroud, and the reactor core. Evaluation of primary water stress corrosion cracking. Alloys 52 and 152 are highchromium weld metals used in reactor pressure vessel head penetration nozzles and as overlays, inlays, or onlays for dissimilar metal piping welds. Pdf for alloy 600, primary water stress corrosion cracking pwscc is one of the key material degradation mechanisms in pressurized water. However, with the discovery of stress corrosion cracking denoted as primary water stress corrosion cracking pwscc at several pwr plants over the past 5 years, the first being at v. Stress corrosion cracking is a form of localised failure which is more severe under the combined action of stress and corrosion than would be expected from the sum of the individual effects acting alone. Primary water stress corrosion cracking analysis in alloy. The purpose of this research was to compare the stress corrosion cracking scc resistance of materials used at the present time for steam generator sg tubing in pressurized water reactor pwr. Stress corrosion cracking scc is a significant ageing degradation mechanism for major components of both pressurized water reactors pwrs and boiling water reactors bwrs. Primary water stress corrosion cracking of highchromium, nickelbase welds near dissimilar metal weld interfaces nuregcr7226 on this page. Several major disasters have involved stress corrosion cracking, including the rupture of high pressure gas transmission pipes, the explosion of boilers, and the destruction of power. Stress corrosion cracking scc is the cracking induced from the combined influence of tensile stress and a corrosive environment. The work in this article is part of a project to develop a quantitative description of stress corrosion cracking scc on the secondary side of pressurized water reactor pwr steam generator tubing based on existing information from operating plants and from laboratory experiments.
Deterioration by clscc can lead to failures that have the potential to release stored energy andor hazardous substances. Evaluation of primary water stress corrosion cracking growth rates. A large variety of the structural metals present in primary and secondary circuits of pressurized water reactors pwrs suffer corrosion. It was found that a compact layer of cr 2 o 3 initially forms over a migrated grain boundary, driven by the diffusion of cr. Stress corrosion cracking tests were conducted in 36oc 680of pressurized water reactor pwr primary water using aerospacegrade super 718 with heat treatment variations which altered the local grain boundary chemistry. It can lead to unexpected sudden failure of normally ductile metal alloys subjected to a tensile stress, especially at elevated temperature. Stress corrosion crack initiation in machined type 316l.
Scc is highly chemically specific in that certain alloys are likely to undergo scc only when exposed to a small number of chemical environments. For these systems, the utilities have always controlled boiler water water purity input to the boiler is a good. Pressurized water nuclear reactors in the united states generate about percent of u. Though efficient, these reactors face a unique challenge with stress corrosion cracking scc. Alloy 600, a nicrfe alloy, is widely used as the pressure boundary component of pressurized water reactors pwrs, such as steam generator. Within the pressure vessels, there are many internal structures that support the reactor core,maintain fuel assembly alignment, etc.
Effect of surface treatments on microstructure and stress corrosion cracking scc of 308l weld metal in primary pressurized water reactor environment. Assessment of weld overlays for mitigating primary water. Intergranular stress corrosion cracking in pressurized water reactor safety injection accumulator nozzles united states nuclear regulatory commission office of nuclear reactor regulation washington, d. Alloy 600 cracking and boric acid corrosion of lightwater reactor pressure vessel. Stress corrosion crack initiation of two thermallytreated, coldworked cw alloy 690 uns n06690 materials was investigated in 360oc simulated pwr primary water using constant load tensile clt tests and blunt notch compact tension bnct tests equipped with direct current potential drop dcpd for insitu detection of cracking. Stress corrosion cracking an overview sciencedirect topics. Intergranular stress corrosion cracking growth behavior of. Stress corrosion crack initiation of alloy 600 in pwr primary water. Stress corrosion cracking of alloy 600 in pwr primary water. Effect of surface treatments on microstructure and stress. However, the inspections required by order ea03009 will ensure that cracking is identified in. Influence of dissolved hydrogen on primary water stress. Chloride stress corrosion cracking clscc is one the most common reasons why austenitic stainless steel pipework and vessels deteriorate in the chemical processing and petrochemical industries.
A highresolution characterization of the initiation of. Stress corrosion cracking of alloy 718 in pressurized. The nozzles were made of forged and annealed alloy 600 uns n06600 base material containing welds with alloys 82 uns n06082 and 182 uns w86182. Current nrc perspectives concerning primary water stress. In many cases, problems with stress corrosion cracking scc can. All holders of operating licenses or construction permits for pressurized. Quantitative assessment of submodes of stress corrosion. Stress corrosion crack initiation of alloy 690 in simulated pressurized water reactor primary water was studied through highresolution characterization of grain boundaries at different stages of the initiation process. Primary water stress corrosion cracking pwscc of inconel 600 addressees. Stress corrosion cracking international institute of. Boiling water reactors bwrs experienced intergranular stress corrosion cracking igscc in austenitic stainless steel during this time.
Nrc regulatory issue summary 200825 primary water stress. The description above for scc behavior in coldrolled austenitic steels in simulated pwr primary water is a similar scenario to that for the mechanism of primary water stress corrosion cracking of alloy 600 in simulated pwr primary water. The corrosion fatigue cf and stress corrosion cracking scc crack growth rates cgrs of type 316ln ss and its welds that are used for pressurized water reactor primary water components were. Primary water stress corrosion cracking behavior of an. Steam purity stress corrosion cracking, gek7 2281 general description remain dissolved in the steam and pass into the turbine. Stress corrosion cracking scc is a significant material degradation for major components of both pressurized water reactors pwrs and boiling water reactors. All holders of operating licenses or construction permits for pressurized water.
A method to assess and predict pressurized water stress corrosion cracking in operational nuclear power plants and the effect of adding zinc compounds into. This mechanism is characterized by corrosion in the microscopic granular composition of a metals surface. Outside diameter stress corrosion cracking of stainless. Effect of dissolved oxygen content on stress corrosion. For several decades pressurized water reactors have experienced primary water stress corrosion cracking pwscc within alloy 600 components and welds.
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