Zinc, nickel, calcium, and magnesium in borated water of a pressurized water reactor (PWR)

Significance of the Topic

Monitoring trace metal impurities in the primary coolant of pressurized water reactors (PWRs) is critical for ensuring materials integrity, minimizing corrosion and extending component lifetime. Boric acid and lithium hydroxide used for reactivity control and pH adjustment create a challenging matrix for trace analysis of zinc, nickel, calcium and magnesium at sub-ppb levels.

Study Objectives and Overview

This application note describes a robust ion chromatography (IC) method capable of quantifying ultra-low concentrations of Zn, Ni, Ca and Mg in high-borate and lithium-rich PWR primary circuit water. The approach integrates inline preconcentration and matrix elimination to achieve reliable sub-parts-per-billion detection.

Methodology and Instrumentation

The analytical workflow combines direct conductivity detection with automated sample handling and inline preconcentration using the MiPCT-ME technique. Key parameters and equipment include:

• Inline eluent preparation: 2.5 mmol/L HNO₃ and 0.5 mmol/L oxalic acid
  
• Columns: Metrosep C4-250/2.0 (analytical), Metrosep C4 Guard/2.0, Metrosep C PCC 1 HC/4.0 (preconcentration)
  
• Flow rate: 0.4 mL/min; Injection volume: 1.0 mL; Column temperature: 32 °C; Total run time: 18 min
  
• Sample handling: 858 Professional Sample Processor and two 800 Dosinos for precise delivery
  
• Instrumentation:
  
  • 850 Professional IC Cation
  • IC Conductivity Detector
  • 849 Level Control for inline eluent preparation

Main Results and Discussion

Analysis of artificial PWR coolant (2 g/L boron, 3.3 mg/L lithium) yielded the following trace metal concentrations with excellent precision and recovery:

• Nickel: 2.01 µg/L (RSD 3.8 %, Recovery 100.4 %)
• Zinc: 2.07 µg/L (RSD 4.6 %, Recovery 103.5 %)
• Magnesium: 2.43 µg/L (RSD 1.5 %, Recovery 113.5 %)
• Calcium: 2.68 µg/L (RSD 2.1 %, Recovery 109.8 %)

The inline preconcentration effectively removed the high borate background, enabling accurate quantification at sub-ppb levels.

Benefits and Practical Applications

The described IC method offers:

• High sensitivity for routine monitoring of corrosion-related metals in PWR primary coolant
• Minimal sample preparation through inline matrix elimination
• Automation for high throughput and reproducibility
• Compliance with stringent reactor water quality standards

Future Trends and Opportunities

Advancements that could further enhance PWR coolant analysis include:

• Integration of on-line IC systems for real-time monitoring
• Coupling with mass spectrometric detection for improved selectivity
• Development of novel sorbent materials for faster preconcentration
• Application of machine learning for data interpretation and predictive maintenance

Conclusion

The presented IC workflow demonstrates a reliable, sensitive and automated solution for the determination of trace zinc, nickel, calcium and magnesium in challenging borated water matrices of PWRs. Inline preconcentration and matrix elimination ensure sub-ppb detection with excellent precision and recovery, supporting corrosion control and regulatory compliance.

Reference

• Metrohm IC Application Note C-138: Zinc, nickel, calcium, and magnesium in borated water of a pressurized water reactor (PWR)