The nozzles were made of forged and annealed alloy 600 uns n06600 base material containing welds with. Steam generator sg drain nozzles on the cold leg side in a pressurized water reactor pwr have exhibited stress corrosion cracking scc. A method to assess and predict pressurized water stress corrosion cracking in operational nuclear power plants and the effect of adding zinc compounds into. Primary water stress corrosion cracking of highchromium, nickelbase welds near dissimilar metal weld interfaces nuregcr7226 on this page. 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. Stress corrosion cracking scc is a significant material degradation for major components of both pressurized water reactors pwrs and boiling water reactors. Alloy 600 is still in use in existing pressurized water reactor pwr. Although the nickel base materials were different from the present study, there are similarities to. 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.
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. Originally selected for its high corrosion resistance, it exhibited, after a long operation period, susceptibility to stress corrosion cracking scc in pwr. 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. Stress corrosion cracking international institute of. 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. Stress corrosion cracking an overview sciencedirect topics. All holders of operating licenses or construction permits for pressurized water. Evaluation of laser peening for mitigation of primary.
Extensive laboratory testing has shown that intergranular stress corrosion cracking igscc requires the presence of the following three key elements. One of the main failure mechanisms that cause risks to pressurized water reactors pwr is the primary water stress corrosion cracking pwscc occurring in. Nrc regulatory issue summary 200825 primary water stress. Cracking can initiate at the inside surface of these materials, in part, because of tensile residual stresses introduced by welding. Stress corrosion crack scc initiation of three millannealed alloy 600 heats. It can lead to unexpected sudden failure of normally ductile metal alloys subjected to a tensile stress, especially at elevated temperature. 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. Pressurized water nuclear reactors in the united states generate about percent of u. Alloy 600, a nicrfe alloy, is widely used as the pressure boundary component of pressurized water reactors pwrs, such as steam generator. Nuclear reactors nickel alloys primary water stress corrosion cracking. 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. This alloy is wellknown to be susceptible to stress corrosion cracking.
Introduction in the united states currently there are approximately 104 operating light water reactors. Shallow intergranular attack andor cracks were found on most highenergy grain boundaries. Though efficient, these reactors face a unique challenge with stress corrosion cracking scc. Corrosion in pressurized water reactors pwrs sciencedirect. 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.
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. This type of corrosion is one of the primary lifelimiting degradation mechanisms of nickelbase alloy pressure boundary components, such as. 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. All holders of operating licenses or construction permits for pressurized. Stress corrosion cracking growth of alloy 800ng in. Stress corrosion cracking scc is a significant ageing degradation mechanism for major components of both pressurized water reactors pwrs and boiling. Stress corrosion cracking facts and how to reduce the. 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. In many cases, problems with stress corrosion cracking scc can. 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. 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. Evaluation of primary water stress corrosion cracking. Effect of surface treatments on microstructure and stress. Of these, 69 are pressurized water reactors pwrs and 35 are boiling water.
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 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 analysis in alloy. Within the pressure vessels, there are many internal structures that support the reactor core,maintain fuel assembly alignment, etc. 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. However, the inspections required by order ea03009 will ensure that cracking is identified in. Outside diameter stress corrosion cracking of stainless. A large variety of the structural metals present in primary and secondary circuits of pressurized water reactors pwrs suffer corrosion. Summer in south carolina, the issue has become significant for the us pwr industry. Chloride stress corrosion cracking in austenitic stainless. The impact of scc on a material usually falls between dry cracking and the fatigue threshold of that material.
Strainhardening may play an important role in the occurrence of intergranular scc. Primary water stress corrosion cracking pwscc of inconel 600. A highresolution characterization of the initiation of. 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. Stress corrosion cracking of alloy 718 in pressurized. Effect of dissolved oxygen content on stress corrosion. Intergranular stress corrosion cracking growth behavior of.
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 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. Pdf for alloy 600, primary water stress corrosion cracking pwscc is one of the key material degradation mechanisms in pressurized water. Pdf evaluation of primary water stress corrosion cracking. 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. Effects of chloride and oxygen on stress corrosion. Stress corrosion crack initiation in machined type 316l. Effects of marine environments on stress corrosion. Steam purity stress corrosion cracking, gek7 2281 general description remain dissolved in the steam and pass into the turbine. It is especially important to avoid any mechanical tensile stress concentration, which will occur at sharp edges and notches. 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. Stress corrosion cracking of alloy 600 in pwr primary water. Boiling water reactors bwrs experienced intergranular stress corrosion cracking igscc in austenitic stainless steel during this time. Primary water stress corrosion cracking pwscc of inconel 600 united states nuclear regulatory commission office of nuclear reactor regulation washington, d.
Stress corrosion cracking behavior of alloy 182 weld in. For these systems, the utilities have always controlled boiler water water purity input to the boiler is a good. Primary water stress corrosion cracking of highchromium. 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, 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. Stress corrosion cracking scc is the growth of crack formation in a corrosive environment. 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. Scc is highly chemically specific in that certain alloys are likely to undergo scc only when exposed to a small number of chemical environments. Primary water stress corrosion cracking pwscc is an intergranular cracking. Iaea nuclear energy series stress corrosion cracking in light.
The primary purpose of this research is to examine the stress corrosion cracking scc resistance of alloy 800ng in pressurized water reactor pwr primary water and pressurized heavy water reactor phwr primary water. Stress corrosion cracking scc is the cracking induced from the combined influence of tensile stress and a corrosive environment. Effect of surface treatments on microstructure and stress corrosion cracking scc of 308l weld metal in primary pressurized water reactor environment. Primary water stress corrosion cracking behavior of an. Stress corrosion cracking of austenitic stainless steels 1011820 technical update, september 2005. Quantitative assessment of submodes of stress corrosion. Intergranular stress corrosion cracking in pressurized water reactor safety injection accumulator nozzles united states nuclear regulatory commission office of nuclear reactor regulation washington, d. The crack growth rate cgr increased with increasing do content in the simulated pwr primary water. For several decades pressurized water reactors have experienced primary water stress corrosion cracking pwscc within alloy 600 components and welds. 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. In recent years, accidents of stress corrosion cracking scc in 316l ss pipes were reported in pwrs. Primary water stress corrosion cracking pwscc of inconel 600 addressees.
Many of these nozzles are joined to the rpv by dissimilar metal welds that may be affected by stress corrosion cracking andor corrosion fatigue 2. 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. 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. Current nrc perspectives concerning primary water stress. 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. Alloy 600 cracking and boric acid corrosion of lightwater reactor pressure vessel. 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. Because pwscc was not properly considered in vintage pressurized water. The required tensile stresses may be in the form of directly applied stresses or in the form of residual. 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. Assessment of weld overlays for mitigating primary water. This mechanism is characterized by corrosion in the microscopic granular composition of a metals surface. 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.
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. Evaluation of primary water stress corrosion cracking growth rates. 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. For alloy 600, primary water stress corrosion cracking pwscc is one of the key material degradation mechanisms in pressurized water reactors pwrs. Influence of dissolved hydrogen on primary water stress. Deterioration by clscc can lead to failures that have the potential to release stored energy andor hazardous substances. 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. Stress corrosion crack initiation of alloy 600 in pwr primary water.
714 445 134 507 319 113 865 967 335 1151 695 1323 937 1417 209 185 105 724 1362 826 77 1405 45 75 448 1517 1274 816 543 574 491 1178 409 102 889 280 474 1154 726 275 381 540 1474 733