Thermal, hydraulic, and corrosion aspects of PWR steam generator problems
TL;DR: In this paper, a review of PWR steam generators is presented, focusing more on the designs that have experienced problems and the effort expended to correct them, including denting, wastage, intergranular attack, stress corrosion cracking, corrosion fatigue and pitting on the outside surfaces of the tubes.
Abstract: Two types of PWR steam generators are in use: recirculating steam generators (RSGs) and once-through steam generators (OTSGs). Most of the units and vertical and this review will be limited to vertical units. Some of these steam generators have operated with a minimum of problems while other steam generator designs have experienced a variety of corrosion and mechanically induced problems. The discussion will focus more on the designs that have experienced problems and the effort expended to correct them. Corrosion problems include denting, wastage, intergranular attack, stress corrosion cracking, corrosion fatigue, pitting on the outside surfaces of the tubes, and stress corrosion cracking the inner surfaces of the tubes. Mechanical concerns have included water hammer, thermal stratification in feed-water pipes, fretting and wear of the tubes caused by excessive tube vibration, and erosion-corrosion. These problems have caused unscheduled outages and expensive repairs.
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107 citations
01 Jan 2007
TL;DR: In this paper, the authors review some examples of corrosion and particularly stress corrosion problems from the author's experience of interpreting and modelling these phenomena in PWR systems, including the major issue of Alloy 600 intergranular cracking in primary PWR coolants, for which both adequate life prediction models and remedial measures now exist.
Abstract: The aging of water cooled and moderated nuclear steam supply systems has given rise to many material corrosion problems of which stress corrosion cracking has proved to be one of the most serious. The aim of this paper is to review some examples of corrosion and particularly stress corrosion problems from the author’s experience of interpreting and modelling these phenomena in PWR systems. Examples of stress corrosion cracking in PWR systems described include the major issue of Alloy 600 intergranular cracking in primary PWR coolants, for which it is generally perceived that both adequate life prediction models and remedial measures now exist. Intergranular corrosion and stress corrosion cracking of Alloy 600 steam generator tubes that occur in occluded superheated crevices on the secondary side of steam generators due to hide-out and concentration of water borne impurities are also addressed. Rather less extensive or well known examples are discussed such as the stress corrosion cracking of carbon and low alloy steels and of stainless steels in occluded dead-leg situations where it is sometimes difficult to guarantee adequate control of water chemistry, particularly at plant start-up. Reference is also be made to the use of high strength fastener materials in PWR systems as well as to the emerging issue of the effect of high neutron doses on the stress corrosion resistance of core structural components fabricated from austenitic stainless steels.
43 citations
TL;DR: The Global Nuclear Energy Partnership (GNEP) as discussed by the authors is an initiative to expand the use of nuclear energy to meet increasing global energy demand in an environmentally sustainable manner, to address nuclea...
Abstract: The goals of the Global Nuclear Energy Partnership (GNEP) are to expand the use of nuclear energy to meet increasing global energy demand in an environmentally sustainable manner, to address nuclea...
33 citations
01 Jan 1999
TL;DR: In this paper, a set of tools for assessing the fouling propensity of a given support design were presented, including criteria for support fouling, correlation of fouling with parameters such as mass flux and quality, descriptions of experimental tools such as flow visualization and measurement of pressure loss profiles, and analytical tools.
Abstract: Abstract It is hypothesized that the thermal-hydraulic environment plays a role in the fouling of tube supports in nuclear steam generators. Experiments were performed to simulate the thermal-hydraulic environment near various designs of supports. Pressure loss, local velocity, turbulence intensity, and local void fraction were measured to characterize the effect of the support. Fouling mechanisms specific to supports were inferred from these experimental data and from actual steam generator inspection results. An analytical model was developed to predict the rate of particulate deposition on the supports, to better understand the complex processes involved. This paper presents the following set of tools for assessing the fouling propensity of a given support design: (1) proposed fouling mechanisms, (2) criteria for support fouling propensity, (3) correlation of fouling with parameters such as mass flux and quality, (4) descriptions of experimental tools such as flow visualization and measurement of pressure-loss profiles, and (5) analytical tools. An important conclusion from this and our previous work is that the fouling propensity is greater with broached support plates, both trefoil and quatrefoil, than with lattice bar supports and formed bar supports, in which significant cross flows occur.
19 citations
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...sign: (1) proposed fouling mechanisms, (2) criteria for...
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TL;DR: Main strengths and shortcomings of present thermal hydraulic analysis methodology are summarized, areas for further research and development are suggested, and topics reviewed include geometry representation of U-tube and once-through steam generators for three-dimensional analysis.
17 citations
References
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01 Jan 1966TL;DR: Abrasive and other types of wear include: adhesives, lubrication, friction, and adhesion, as well as material properties that influence surface interaction as discussed by the authors.
Abstract: Material Properties That Influence Surface Interactions. Surface Interactions. Friction. Types of Wear. Adhesive Wear. Abrasive and Other Types of Wear. Lubrication. Adhesion. Appendix. Sample Problems. Index.
3,042 citations
TL;DR: In this paper, a method for predicting the deposition of particles entrained in turbulent flow is described, ranging from molecular size to ∼100µ in diameters, and the method predicts the deposition particles from molecular to diameters.
Abstract: This paper describes a method for predicting the deposition of particles entrained in turbulent flow. The method predicts the deposition of particles ranging from molecular size to ∼100µ in diamete...
209 citations
TL;DR: In this article, the fluid-force coefficients for a row of cylinders and a square array are determined from available experimental data and critical flow velocities are calculated as a function of system parameters.
Abstract: The fluid-force coefficients for a row of cylinders and a square array are determined from available experimental data and critical flow velocities are calculated as a function of system parameters. Experimental data for critical flow velocities are found to be in good agreement with the analytical results. It is concluded that different stability criteria have to be utilized in different parameter ranges because of different instability mechanisms. 25 refs.
101 citations
TL;DR: In this article, a review of French data showed a reversal of the usual sensitizing effect in the case of intergranular stress corrosion cracking in high temperature, deaerated water.
Abstract: Intergranular stress corrosion cracking (SCC) of Inconel 600 is of concern to the nuclear power industry. Heat exchangers in commercial nuclear systems have shown SCC in only a fraction of a percent of the tubes in high temperature water, but laboratory SCC of Ni-containing alloys have been demonstrated by several research groups. This review revolves around French data, which show a reversal of the usual sensitizing effect in the case of SCC in high temperature, deaerated water. There is no cracking reported in material first heated so as to precipitate carbides at the grain boundaries, whereas high temperature annealed conditions lead to intergranular SCC in the same laboratory experiments. Electrochemically, SCC and also grain boundary corrosion are related to the potential level of a given test; however, it is not yet understood how the different grain boundary zones in Inconel 600 corrode (with and without applied stress) so that the mechanism of cracking remains speculative. Cr-depletion is...
88 citations
77 citations