Determination of Trace Organic Acids and Inorganic Anions in Boric Acid-Treated Power Plant Waters Using an Automated Reagent-Free Ion Chromatography System

Importance of the Topic

The reliable control of trace ionic contaminants in boric acid–treated waters is critical for nuclear power plants to minimize corrosion in steam generators and turbines. Sub-µg/L levels of aggressive anions such as chloride, sulfate, nitrite, and organic acids can catalyze stress corrosion cracking, lead to component damage, and cause unplanned shutdowns. Automated, high-sensitivity analyses support the stringent guidelines set by organizations like EPRI.

Objectives and Study Overview

This study demonstrates a fully automated, reagent-free ion chromatography (RFIC) approach to determine trace organic acids (formate, acetate, glycolate) and inorganic anions (fluoride, chloride, nitrite, sulfate, bromide, nitrate, phosphate) in simulated power plant waters containing 1 000–2 500 mg/L boron and 1.8–5 mg/L lithium.

Methodology and Instrumentation

An ICS-3000 RFIC system is configured with:

• Electrolytically generated KOH eluent (EGC II KOH, 7–60 mM gradient)
• Continuously regenerated anion trap (CR-ATC) upstream of the degasser
• ASRS ULTRA II suppressor and CRD 200 for carbonate removal
• IonPac AG15/AS15 (2 × 50 mm/2 × 250 mm, 2 mm i.d.) separation columns
• UTAC-ULP1 concentrator (5 × 23 mm) for 2 mL sample preconcentration
• Dual-pump Automation Manager and AS-HV autosampler for online matrix elimination and standard spiking
• CR-CTC II trap column to remove lithium from samples

Samples (up to 10 mL DI rinse) are loaded on the concentrator, rinsed to eliminate borate matrix, then eluted onto the AS15 column with a stepwise KOH gradient. Detection is by suppressed conductivity in recycle mode at 65 mA.

Main Results and Discussion

Method detection limits ranged from 0.006 µg/L (fluoride) to 0.050 µg/L (bromide, phosphate). Calibration was linear (r² > 0.999) over µg/L to low mg/L ranges. Precision (n = 10) was typically <0.1% RSD (retention time) and <3% RSD (peak area). Recoveries for spiked samples in 1 000–2 500 mg/L boron matrices were 89–112%. Automated inline spiking minimized contamination and improved reproducibility. Borate elutes well before chloride, enabling quantitation of early-eluting organic acids.

Benefits and Practical Applications

• High sensitivity and automation reduce manual eluent preparation, spiking errors, and contamination risks.
• Sub-µg/L monitoring of corrosive anions supports compliance with nuclear plant water chemistry guidelines.
• Online standard generation and spiking streamline quality control and method validation.
• Reagent-free eluent generation and trap columns lower labor and improve baseline stability.

Future Trends and Potential Applications

Advances may include coupling RFIC with mass spectrometry for structural confirmation, miniaturized high-throughput formats, and expanding to other challenging matrices (e.g., high-pressure boiler waters). Integration with advanced data analytics and remote monitoring could further enhance corrosion control strategies.

Conclusion

This RFIC approach delivers accurate, precise, and contamination-free analysis of trace organic and inorganic anions in boric acid–treated power plant waters. The combination of electrolytic eluent generation, trap columns, and automated autosampling provides a robust workflow for routine water chemistry monitoring in nuclear and industrial applications.

Reference

1. Millet P.J.; Wood C.J. Recent advances in water chemistry control at US PWRs. Int. Water Conf. 1997.
2. IAEA TECDOC-1361. Assessment and management of ageing of major nuclear power plant components. 2003.
3. EPRI, Water Chemistry Guidelines for PWR Secondary Systems. 2006.
4. Dionex Application Note 166: Eluent generation for trace anion analysis of borated waters. 2004.
5. Dionex ICS-3000 RFIC system manuals (EGC II, CR-ATC, CR-CTC II, ASRS ULTRA II). 2005–2007.