Trace anions including chromate in water-steam circuit of a boiling water reactor (BWR)

Significance of the Topic

The quality of feed water and steam cycle water in boiling water reactors (BWR) is critical to prevent corrosion and maintain reactor safety. Monitoring trace anions, including chromate as an indicator of material degradation, provides an early warning of potential corrosion products and ensures system integrity.

Objectives and Study Overview

This application note describes an automated ion chromatography method to detect ultratrace levels of fluoride, chloride, nitrate, sulfate, oxalate, and chromate in water–steam circuits of BWRs. The goal is to achieve sensitive, accurate, and reproducible measurements with minimal manual intervention.

Methodology and Instrumentation

Automated sample preparation employs Metrohm’s Inline Preconcentration (MiPCT) system combined with a Professional Sample Processor for precise liquid handling. A single multi-ion calibration standard covers all target anions, simplifying workflow.

• Instrumentation:
  
  • 850 Professional IC Anion – MCS
  • IC Conductivity Detector
  • 858 Professional Sample Processor
  • 800 Dosino for liquid handling
  • 849 Level Control for inline eluent preparation
• Columns:
  
  • Metrosep A Supp 5 – 150/4.0
  • Metrosep A Supp 4/5 Guard/4.0
  • Metrosep A PCC 1 HC/4.0
• Eluent (inline): 4.8 mmol/L Na₂CO₃ and 1.5 mmol/L NaHCO₃
• Suppressor regenerant: 100 mmol/L H₂SO₄
• Rinsing solution: Ultrapure water
• Flow rate: 0.8 mL/min; Injection volume: 40 µL; Column temperature: 30 °C; Analysis time: 16 min

Main Results and Discussion

Trace levels (approx. 0.11–0.23 µg/L) of all target anions were quantified with satisfactory precision and recovery.

• Fluoride: 0.11 µg/L, RSD 4.4%, Recovery 109%
• Chloride: 0.21 µg/L, RSD 1.7%, Recovery 104%
• Nitrate: 0.23 µg/L, RSD 2.7%, Recovery 113%
• Sulfate: 0.21 µg/L, RSD 2.3%, Recovery 106%
• Oxalate: 0.20 µg/L, RSD 8.2%, Recovery 100%
• Chromate: 0.19 µg/L, RSD 3.6%, Recovery 96%

The method demonstrates robust reproducibility and accuracy at sub-microgram levels, enabling reliable monitoring of corrosive species and early detection of chromium release.

Benefits and Practical Applications

This approach offers full automation, inline preconcentration, and single-standard multi-ion calibration. It minimizes manual handling and reduces contamination risk. The technique is suitable for routine quality control in nuclear power plant laboratories and can be adapted for other low-level anion monitoring tasks.

Future Trends and Opportunities

Advances in microfluidics and on-line monitoring could further streamline analysis and provide real-time data. Integration with plant control systems and predictive maintenance algorithms may enhance operational safety. Expansion to additional corrosive or regulatory-relevant anions could broaden application scope.

Conclusion

The described ion chromatography method reliably quantifies ultratrace anions, including chromate, in BWR water–steam circuits. Its high sensitivity, precision, and automation support proactive corrosion control and quality assurance in nuclear power environments.

References

• IC Application Note S–306, Metrohm