Determination of Trace Nickel and Zinc in Borated Power Plant Waters Containing Lithium Hydroxide Using Nonsuppressed Conductivity Detection

Significance of the Topic

The monitoring of trace nickel and zinc in pressurized water reactor (PWR) primary coolant is critical for controlling corrosion, minimizing radiation fields, and reducing maintenance costs. Boric acid and lithium hydroxide are routinely added to PWR coolant for reactivity control and pH adjustment. Zinc injection suppresses cobalt activation on stainless steel surfaces, while nickel release from corrosion of steam generator alloys can exacerbate material degradation. Sensitive and selective analytical methods are therefore essential for reliable water chemistry management.

Objectives and Study Overview

This application note describes the development and validation of a cation-exchange ion chromatography method with nonsuppressed conductivity detection for the determination of low microgram-per-liter levels of nickel and zinc in simulated borated power plant waters containing lithium hydroxide. The goals include eliminating the need for complex postcolumn derivatization, achieving low detection limits through large-volume preconcentration, and evaluating method performance in high-matrix samples.

Methodology

Samples of deionized water and synthetic borated/lithium solutions (1,000–2,500 mg/L boron with 1.8–5 mg/L lithium) were prepared along with calibration standards (2.5–25 µg/L). A Thermo Scientific Dionex IonPac SCS 1 analytical column (4×250 mm) with SCG 1 guard column and a TCC-ULP1 concentrator (5×23 mm) enabled large-volume (3 mL) injections. The eluent comprised 2.5 mM methanesulfonic acid, 1.2 mM oxalic acid, and 2 mM ascorbic acid at 30 °C and 1 mL/min. Nonsuppressed conductivity detection provided a background of ~1,300 µS and noise of ~10 nS.

Instrumentation Used

• Thermo Scientific Dionex ICS-3000 IC system (DP dual pump, DC detector, autosampler)
• Dionex IonPac SCS 1 analytical column and SCG 1 guard column
• Thermo Scientific Dionex TCC-ULP1 concentrator column
• Conductivity detector configured for positive signal polarity
• Dionex Chromeleon 6.8 chromatography data system

Main Results and Discussion

Deionized water blanks showed no interfering peaks. Calibration curves for nickel and zinc were linear (r2 ≥ 0.9998) from 2.5 to 25 µg/L. Limits of detection were 0.76 µg/L for nickel and 0.43 µg/L for zinc (S/N=3); quantification limits were 2.5 and 1.42 µg/L (S/N=10). In simulated borated samples, retention time shifts up to 6.2% were observed due to high lithium concentrations, but quantitation was unaffected. Spike recoveries ranged from 95.4% to 102.5% for nickel and 94.0% to 100.4% for zinc across matrices. Precision (n=6) showed retention time RSDs below 0.35% and peak area RSDs below 2.3%.

Benefits and Practical Applications of the Method

• Avoids preparation and maintenance of postcolumn derivatization reagents
• Enables sub-µg/L detection of nickel and zinc in high-matrix samples
• Provides robust linearity, precision, and accuracy for nuclear power plant monitoring
• Streamlines routine water chemistry analysis in PWR primary coolant

Future Trends and Applications

Advances in ion chromatography detection, such as improved conductivity sensors and automated on-line sampling, will enhance continuous water chemistry monitoring. Integration with data analytics and process control systems may enable predictive maintenance and real-time corrosion management. Extension of this approach to other transition metals and radionuclide precursors will further support nuclear plant safety and efficiency.

Conclusion

The developed nonsuppressed conductivity IC method with large-volume preconcentration offers a simple, sensitive, and accurate approach for determining trace nickel and zinc in borated, lithium-containing PWR waters. It eliminates complex postcolumn chemistry while maintaining low detection limits and high reliability, making it well suited for routine nuclear water chemistry control.

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