Online trace analysis of anions in the primary circuit of nuclear power plants

Significance of Online Trace Anion Monitoring in Nuclear Power Plants

Continuous corrosion control in the primary circuit of pressurized water reactors (PWRs) is essential to maintain the integrity of metal components under high temperature and pressure. Trace anions, even at microgram-per-liter levels, accelerate corrosion and may compromise the reactor’s safety. Implementing a sensitive, automated analytical method ensures rapid detection of aggressive species and enables immediate corrective measures.

Objectives and Overview

This work presents an integrated solution for online monitoring of trace anions in the primary coolant circuit of PWRs. The aims include:

• Detecting fluoride, chloride, nitrate, sulfate and phosphates alongside organic degradation products (glycolate, formate, acetate) and chromate.
• Operating in the presence of up to grams-per-liter concentrations of boric acid and lithium hydroxide.
• Providing real-time data and alarm functions to prevent corrosion damage.

Methodology and Instrumentation

The analytical platform is the 2060 IC Process Analyzer, a modular ion chromatograph designed for process environments. Key features:

• Inline Preconcentration: Enriches trace anions from large sample volumes for enhanced sensitivity.
• Inline Matrix Elimination and Neutralization: Removes high levels of H3BO3 and LiOH without manual intervention.
• Integrated Eluent Generation: Produces a stable eluent stream, ensuring consistent baselines.
• Conductivity Detection: Provides quantitation of ionic species across ng/L to percentage levels.
• Multi-stream Capability: Connects up to 20 sampling points for sequential analysis.
• Automated Calibration and Diagnostics: Software control enables scheduled calibrations, trend monitoring, and alarm outputs via Modbus or discrete I/O.

Main Results and Discussion

Using a test sample spiked with 2 g/L of various anions in the presence of 2 g/L boric acid and 3.3 mg/L LiOH, the system achieved:

• Limits of detection in the low microgram-per-liter range.
• High reproducibility with excellent recovery rates for all target anions.
• Simultaneous quantification of organic degradation products and chromate, enabling early diagnosis of ion exchanger failure and corrosion onset.
• Stable operation over several weeks with no manual sample handling.

Benefits and Practical Applications

The online 2060 IC Process Analyzer delivers:

• Real-time monitoring with automatic alarms to prevent irreversible corrosion damage.
• Reduction in labor and human error through full automation of sample conditioning and analysis.
• Comprehensive water chemistry profiling by combining anion and cation detection.
• Cost savings by protecting expensive assets such as reactor internals, heat exchangers, and turbines.

Future Trends and Opportunities

Advances in process ion chromatography and inline sample treatment are expected to include:

• Integration of spectroscopic detectors for complementary species identification.
• Improved data analytics and machine learning for predictive corrosion modeling.
• Miniaturized, wireless analyzers for decentralized field deployment.
• Expanded range of detectable contaminants, including radionuclides and metal ions.

Conclusion

The presented online ion chromatography solution effectively addresses the challenges of trace anion analysis in PWR primary circuits. Its combination of inline preconcentration, matrix elimination, automated calibration, and multi-stream capability ensures reliable, continuous monitoring of aggressive species. This approach enhances plant safety, minimizes corrosion risks, and supports regulatory compliance.

Reference

• AN-S-306 – Trace anions including chromate in water-steam cycle of a boiling water reactor (BWR).
• AN-Q-006 – Online analysis of trace anions in borated water of a pressurized water reactor (PWR).
• 8.000.6071EN – Trace-level determination of anions in the primary circuit of a PWR-type nuclear power plant using ion chromatography after inline sample preparation.