Determination of Trace Copper, Nickel, and Zinc in Boiling Water Reactors Using Nonsuppressed Conductivity Detection

Importance of the Topic

The integrity of boiling water reactors (BWRs) depends critically on tight control of trace metal contaminants such as copper, nickel, and zinc. These transition metals arise from corrosion of plant components and can accelerate intergranular stress corrosion cracking (IGSCC), leading to costly outages, component replacement, and increased radiation exposure. Sensitive routine monitoring of these ions at sub-μg/L levels is therefore essential to ensure reactor safety, reduce maintenance costs, and prolong equipment life.

Objectives and Study Overview

This study aims to develop and validate a simple, reliable ion chromatographic method using cation-exchange separation coupled with nonsuppressed conductivity detection for quantifying trace levels of copper, nickel, and zinc in a simulated BWR coolant matrix. Key goals include optimizing sample concentration, column selection, eluent composition, and evaluating performance metrics such as detection limits, linearity, precision, and recovery.

Methodology and Instrumentation

A deionized water matrix was spiked with known amounts of Cu, Ni, and Zn to simulate BWR feedwater. An 8 mL sample loop loaded onto a Trace Cation Concentrator (TCC-ULP1) preconcentrated analytes prior to analysis on a 2 mm Thermo Scientific Dionex IonPac SCS 1 column. The eluent consisted of 2 mM methanesulfonic acid (MSA) with 0.5 mM oxalic acid at 0.25 mL/min, maintained at 30 °C. Nonsuppressed conductivity detection was used to record analyte signals. Calibration standards ranged from 0.25–5.0 μg/L (Zn) and 0.5–5.0 μg/L (Cu, Ni). Performance was assessed by replicate injections over three days.

Used Instrumentation

• Thermo Scientific Dionex ICS-2100 or equivalent system
• Single isocratic pump, vacuum degasser, 6-port valve
• Dionex AS autosampler with 10 mL syringe and 8.2 mL needle
• Trace Cation Concentrator (TCC-ULP1, 5 × 23 mm)
• Conductivity cell and column heater enclosure
• Chromeleon CDS software version 7.1

Main Results and Discussion

Limits of detection (3× noise) were 0.14 μg/L (Cu), 0.12 μg/L (Ni), and 0.054 μg/L (Zn). Limits of quantification (10× noise) were 0.45, 0.40, and 0.18 μg/L, respectively. Calibration exhibited excellent linearity (r² > 0.999), and intraday retention time RSDs were <0.5% while peak area RSDs remained below 6%. Recoveries for 0.5 μg/L spikes ranged from 92.2–99.4%, confirming method accuracy. Chromatograms showed clear separation of Cu, Ni, and Zn from common cations without interference.

Benefits and Practical Applications

Compared to postcolumn colorimetric detection (PAR reagent), the nonsuppressed conductivity approach requires fewer reagents, simpler preparation, and reduced analysis time while still achieving sub-μg/L sensitivity. Routine implementation in nuclear power plant laboratories can streamline monitoring, improve turnaround, and lower operating costs.

Future Trends and Possibilities

Future work may integrate larger sample volumes via an independent loading pump to achieve even lower detection limits. Adaptation to online or inline monitoring platforms could enable continuous real-time analysis. Extending the method to additional transition metals or leveraging hybrid detectors (e.g., mass spectrometry) may further enhance selectivity and broaden applicability across diverse industrial water matrices.

Conclusion

The developed cation-exchange method with nonsuppressed conductivity detection on a 2 mm IonPac SCS 1 column provides a robust, sensitive, and accurate solution for quantifying trace copper, nickel, and zinc in BWR coolant. Its simplicity and performance make it suitable for routine nuclear power plant water chemistry monitoring to safeguard reactor integrity.

Reference

• World Nuclear Association. Nuclear Power in the World Today. 2011.
• World Nuclear Association. Nuclear Power in the USA. 2011.
• World Nuclear Association. World Energy Needs and Nuclear Power. 2011.
• Nuclear Energy Institute. Key Issues: Electricity Supply. 2011.
• World Nuclear Association. Nuclear Power Reactors. 2011.
• Electric Power Research Institute. BWR Water Chemistry Guidelines–2004 Revision.
• Electric Power Research Institute. Chemistry Monitoring and Control for Fuel Reliability. 2004.
• Dionex Application Note 277: Transition Metals in Power Industry Waters Using IC. 2011.
• Dionex Application Note 250: Trace Ni and Zn in Borated Power Plant Waters. 2010.