Howard Ocken, Keith Fruzzetti, Paul Frattini, and Christopher J. Wood

Recent Developments in PWR Zinc Injection

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This paper reviews the status of zinc injection in PWRs. Initial field applications have been undertaken to mitigate degradation of Ni-base structural alloys by primary water stress corrosion cracking. The first U.S. demonstration was at Farley 2 in 1994; zinc injection was later initiated at Farley 1 and Diablo Canyon 1 and 2. Reactor water zinc levels are in the 30-40 µg kg^-1 range, since laboratory results have shown that this concentration is needed to mitigate orimary water stress corrosion cracking. Zinc injection at low levels (~ 5 µg kg^-1) has been started at three Siemens-designed PWRs and at Palisades, where the aim is to lower shutdown radiation fields.
All U.S. PWRs injecting zinc have seen significant decreases in shutdown dose rates. Available data suggests it is premature to conclude if zinc mitigates primary water stress corrosion cracking.

PowerPlant Chemistry 2002, 4 (5)

Francis Nordmann, Agnes Stutzmann, Jean-Luc Bretelle

Overview of PWR Chemistry Options

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This paper describes the main options for the primary and secondary water chemistry of PWRs. After having focused on corrosion mitigation in the past, the options now emphasize cost saving, ease and reliability of operation, low activities, and limitation wastes.
For the primary coolant, the main options concern ways to get the optimum pH (lithium increase or enriched boric acid use), zinc addition, fuel axial offset anomaly limitation, and the best shutdown procedure to save time and efficiently eliminate radioactive elements.
For the steam-water system, the main options concern mitigation of Alloy 600 MA stress corrosion cracking of steam generator tubing, flow-accelerated corrosion of carbon steel and the control of steam generator fouling by selection of the most appropriate secondary water treatment (pH, amine, hydrazine concentration, dispersant addition).

PowerPlant Chemistry 2002, 4 (5)

Luis Carvalho, Rosa Crovetto, Gerry W. Sauve, and Paul Sehl

Cation Conductivity and Power Plant Reliability: A 20-Plant Survey

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The purity of steam and boiler feedwater is one of the most important criteria for ensuring component availability and reliability in power plants. Steam turbine manufacturers are tying increasingly stringent steam purity requirements to warranty clauses of their machinery.

Cation (acid) conductivity, with its many limitations, is the most prominent control parameter for steam purity enforced by turbine manufacturers. Low molecular weight aliphatic organic acids, carbon dioxide, and inorganic anions affect cation conductivity. According to the literature, specific corrosion effects of organic acids are inconclusive and deserve more research.

Independent power producers (IPP), unlike most utility generating stations, operate with minimal staff. IPP owners, in trying to comply with the tighter steam purity requirements, incur higher capital and operating expenditures with sophisticated water treatment equipment and more complex monitoring instrumentation. Additional on-site laboratory complexity and meaningful interpretation of all the collected data also burden the typical high-efficiency IPP operation. This paper reports on a survey of twenty operating plants (mostly power plants) across Canada ranging in pressure from 6.2 to 19.65 MPa (900 to 2850 psig). The paper presents data collected (cation conductivity, organic acids, turbine operating hours, and maintenance/inspection history) during the survey. Organic acid concentration, cation conductivity, and selected inorganic anions showed no correlation to system reliability in any of the plants surveyed.

PowerPlant Chemistry 2002, 4 (5)

R. K. Singh Raman

Thermal Scaling in the Context of Life Assessment and Microstructural Degradation of Weldments Steels in Steam Generation Systems

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The paper discusses the estimation of remnant creep life and determination of crack velocity using thickness of oxide scales that are generally present on the in-service steam generating systems. The prevalence of in-service failures in the welds of chromium-molybdenum ferritic steels causes great concern in steam generating/handling systems of power plants. This paper discusses the non-uniform scaling behavior across microstructural gradients in weldments of pressure vessel steels. The necessity for developing a global model for life assessment by relating oxide scale thickness with the time-temperature history of in-service welded components is also discussed. The paper also presents evidence of steam corrosion-assisted deterioration in microstructure that can profoundly affect the creep life.

PowerPlant Chemistry 2002, 4 (5)

Andrei Yu. Petrov, Caibin Xiao, Donald A. Palmer, and D. Whitney King

Chemiluminescence Method for the Determination of Sub-µg kg-1 Copper Concentrations

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Copper deposition in high-pressure steam turbines represents a significant source of performance and reliability loss to fossil power plants with mixed-metallurgy feedwater systems. Provisions for reliable and prompt monitoring of low concentrations of copper compounds at power plants as specified by recent copper guidelines have become more crucial. This paper presents the chemiluminescence method for the determination of low (µg kg^-1 and sub-µg kg^-1) copper concentrations and provides a comparison with ion chromatography and graphite furnace atomic absorption.

PowerPlant Chemistry 2002, 4 (5)

Beverly Newton

Use of Ion Chromatography for Measuring Ions in Water to Protect The New Generation Gas-Fired, Combined Cycle Power Plants

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The use of ion chromatography for monitoring corrosive ions in water has been implemented at several new combined cycle, gas fired power plants in the U.S. Due to stringent requirements for clean water to prevent corrosion and plugging of turbine components, this methodology is predicted to have a significant impact in extending useful operating lifetimes and to measurably increase the availability of components in contact with water. Ion chromatography, due to its ability to identify individual anion and cation species, to achieve parts-per-trillion detection limits, and to operate on-line, has played a central role in the effectiveness of these water chemistry monitoring programs. Ion chromatography has provided the capability to distinguish between corrosive and non-corrosive ionic intrusions, identify and eliminate sources of corrosive ingress, optimize and extend the lifetime of demineralizer resins, measure hideout return, determine mass balances, and maintain neutral anion-to-cation balances. Cost savings due to chemistry monitoring programs using ion chromatography have been estimated to be in the millions of dollars per year.

This paper provides an overview of the applications and justification (using case studies) for using ion chromatography for the analysis of water in these new generation power plants.

PowerPlant Chemistry 2002, 4 (5)

Anton E. Cattaert

Major Reliability and Lubricant Consumption Savings at Tutuka Power Station

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The proper selection and management of lubricants is very important for both improvement of equipment reliability and reduction of operating cost. The paper briefly describes actions undertaken as part of the establishing and optimizing of a basic lubricant condition-monitoring program. These efforts have resulted in considerable cost savings.

PowerPlant Chemistry 2002, 4 (5)

Reinhard Wloch und Wilhelm Hild

Ein neues und verbessertes Verfahren zur Vermeidung von Korrosion auf Kupfer und Kupferlegierungen in Kühlwassersystemen

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Zur Vermeidung von Korrosion auf Kupfer und Kupferlegierungen in Kühlwassersystemen werden üblicherweise Azole als sogenannte Buntmetallinhibitoren eingesetzt. Die Wirksamkeit und die Stabilität der Azole in einem kühlwasserführenden Medium ist abhängig von der Stabilität und der Beständigkeit des vom eingesetzten Azols gebildeten Schutzfilms an der Buntmetalloberfläche (Kupfer oder Kupferlegierung). Ein wichtiger Faktor, der die Stabilität des eingesetzten Buntmetallinhibitors beeinflusst ist die Verwendung eines oxidierenden Biozids (Chlor, Chlorbleichlauge oder bromabspaltende Produkte) zur Kontrolle der mikrobiologischen Aktivität im Kühlsystem. Die Instabilität des Buntmetallinhibitors in Gegenwart von oxidierenden Bioziden kann dazu führen, dass die Korrosionsrate auf Kupfer und Kupferlegierungen oder auch die galvanische Korrosion auf Normalstahl bzw. der Verbrauch an oxidierendem Biozid beeinflusst wird.

Von BetzDearborn wurde daher ein neuer Buntmetallinhibitor mit verbesserten Korrosionseigenschaften und einer höheren Stabilität des gebildeten Inhibitorfilms im Vergleich zu herkömmlichen Inhibitoren entwickelt. In mehreren Anwendungsbespielen konnte gezeigt werden, dass durch den Einsatz des neuen Inhibitors die Korrosionsraten auf Buntmetall, auch in Gegenwart oxidierender Biozide, deutlich verbessert werden.

PowerPlant Chemistry 2002, 4 (5)