Trace-level determination of anions in the primary circuit of a PWR-type nuclear power plant using ion chromatography after inline sample preparation

Importance of the Topic

Monitoring trace anions such as chloride, nitrate, sulfate and organic acids in the primary coolant circuit of PWR reactors is essential to prevent material corrosion and assess ion exchanger performance. High levels of boric acid and cationic interferences in the reactor water challenge conventional analysis at the sub-ppb level.

Objectives and Overview of the Study

This work aims to develop an inline sample preparation workflow coupled with ion chromatography to achieve ultratrace determination of inorganic and organic anions in borated reactor water. Key objectives include matrix elimination, cation removal, inline calibration and preconcentration in a single automated system.

Methodology and Instrumentation

The method integrates the following steps:

• Inline cation exchange to remove interfering metal ions
• Matrix elimination of boric acid via rinsing the preconcentration column
• Preconcentration of sample volumes up to 2000 μL
• Inline calibration using a single concentrated standard and multi-injection loops
• Chemical suppression for conductivity detection

The instrumentation includes Professional IC 850 Anion with MCS Prep, Sample Processor 858, Advanced IC Liquid Handling unit, Dosing Unit with 800 Dosino, Metrosep A PCC 1HC preconcentration column, Metrosep A Supp 7 – 250 separation column with RP guard and a sodium carbonate eluent.

Main Results and Discussion

The system demonstrated excellent performance with relative standard deviations below 1% for all target anions and correlation coefficients above 0.9999. Detection was achieved at ppt levels for fluoride, glycolate, acetate, formate, chloride, nitrite, bromide, nitrate, phosphate and sulfate in reactor water. Inline calibration maintained linearity across the expected concentration range. The intact flow path and external sample preparation preserved separation efficiency and detection sensitivity even under harsh power plant conditions.

Benefits and Practical Applications

This fully automated inline approach offers:

• High precision ultratrace analysis in complex borated matrices
• Reduced manual handling and contamination risk
• Rapid single isocratic run for a broad panel of anions
• Adaptability to on-site monitoring in nuclear facilities for QA/QC and preventive maintenance

Future Trends and Potential Applications

Future developments may focus on further automation, miniaturized flow cells, coupling with mass spectrometry for enhanced selectivity, remote diagnostics, and integration of data analytics and machine learning for real-time water quality management.

Conclusion

The presented inline sample preparation with ion chromatography delivers a robust, precise and highly linear method for trace anion analysis in PWR primary circuit water despite challenging boric acid and cationic interferences.

References

T Hartmann, K H Viehweger, A Wille Trace level determination of anions in the primary circuit of a PWR type nuclear power plant using IC after inline sample preparation Poster 8.000.6071EN Metrohm AG Herisau Switzerland