Fast and Sensitive Determination of Transition Metals in Power Industry Waters Using Ion Chromatography

Significance of the Topic

Effective control of water chemistry is critical to the safe and efficient operation of nuclear power plants. Corrosion of reactor internals, turbine circuits, and associated piping can lead to radiation exposure during maintenance shutdowns and may accelerate fuel cladding degradation. Monitoring trace transition metals such as iron, copper, nickel, and zinc in both boiling water reactors (BWR) and pressurized water reactors (PWR) coolant streams is essential to detect early signs of corrosion and to manage radiological risks.

Objectives and Study Overview

This application note presents a rapid and sensitive ion chromatography (IC) method for simultaneous determination of Fe(III), Cu(II), Ni(II), and Zn(II) at sub-µg/L concentrations in power plant water samples. Two representative surrogate matrices were used:

• BWR surrogate: deionized water spiked with transition metals
• PWR surrogate: borated water containing lithium hydroxide, with and without added zinc

The study evaluates method linearity, limits of detection (LOD) and quantification (LOQ), accuracy (recovery), and precision (retention time and peak area reproducibility).

Methodology and Instrumentation

The method couples cation-exchange ion chromatography with postcolumn derivatization and visible absorbance detection:

• Instrumentation: Dionex ICS-3000 or ICS-5000 IC system with single- or dual-temperature zone column compartment, AS autosampler, and VWD detector
• Columns: IonPac CG5A guard column (2 × 50 mm) and CS5A analytical column (2 × 250 mm)
• Eluent: 7.0 mM pyridine-2,6-dicarboxylic acid (PDCA), 66 mM KOH, 5.6 mM K2SO4, and 7.4 mM formic acid at 0.30 mL/min
• Preconcentration: IonPac TCC-2 Trace Cation Concentrator, 3 × 35 mm, concentrating 4.7 mL sample
• Postcolumn: 0.24 mM PAR reagent delivered at 0.15 mL/min via PC10 pneumatic package; absorbance measured at 530 nm
• Software: Chromeleon CDS for data acquisition and processing

Sample containers and standards were rigorously cleaned and prepared to minimize blank contamination. Surrogate samples were prepared by spiking known amounts of transition metal standards into deionized or borated/lithiated water.

Main Results and Discussion

The method achieved excellent linearity (r>0.9997) over two orders of magnitude for Fe, Cu, and Zn; Ni showed slightly lower response but acceptable correlation. LODs were <0.06 µg/L for all analytes, with LOQs <0.2 µg/L. In BWR surrogate tests, recoveries ranged 84–103% across two spiking levels (0.2–1.0 µg/L), with retention time RSD ≤0.15% and peak area RSD ≤2.2%. In PWR surrogates containing 1000–2500 mg/L boron and 1.8–5.0 mg/L lithium (with or without 15 µg/L Zn), recoveries ranged 83–110% and precision remained comparable, demonstrating minimal matrix interference.

Benefits and Practical Applications

• High sensitivity and selectivity for multiple trace metals in complex reactor water matrices
• Rapid analysis time: all four analytes separated in under 10 minutes
• Robust performance in high-boron and lithium matrices without column overload
• Low carryover and minimal interferences from matrix cations
• Suitability for routine power plant coolant monitoring, QA/QC, and regulatory compliance

Future Trends and Opportunities

Advances in online IC systems and automated sample handling will enable real-time monitoring of transition metals in reactor coolant loops. Emerging chelating reagents and novel column chemistries may expand the scope to other corrosion-relevant elements such as cobalt isotopes or silver. Integration with predictive maintenance software and artificial intelligence could further optimize corrosion management strategies.

Conclusion

A postcolumn-derivatization IC method with visible absorbance detection has been developed and validated for the rapid, sensitive, and accurate determination of Fe(III), Cu(II), Ni(II), and Zn(II) at sub-µg/L levels in nuclear power plant water matrices. Excellent linearity, low detection limits, high recoveries, and robust precision support its application in routine coolant chemistry monitoring for both BWR and PWR systems.

Reference

1. World Nuclear Association. Nuclear Power Reactors. Updated Nov 2010.
2. Nuclear Energy Institute. Key Issues: Electricity Supply. Updated Aug 2010.
3. Nordmann, F. Aspects of Chemistry in French Nuclear Power Plants. ICPWS-14, Kyoto 2004.
4. Piippo, J.; Saario, T. Influence of Zinc on Oxide Layer Growth. BNES Conference 1996.
5. Marchetti, L.; Perrin, S.; Raquet, R.; Pijolat, M. Corrosion Mechanisms of Ni-Alloys. Mater Sci Forum 2008.
6. Boiling Water Reactor Chemistry Performance Monitoring Report, EPRI 2009.
7. Dionex Application Note 250: Trace Ni and Zn in Borated Power Plant Waters, 2010.
8. Dionex Application Note 158: Trace Metals in Power Industry Samples, 2004.
9. Dionex Application Note 131: Transition Metals at ppt Levels in High-Purity Water, 1998.