Determination of Polyacrylic Acid in Nuclear Power Plant Pressurized Water Reactor Secondary Feed Water

Significance of the topic

The buildup of metal oxide deposits in pressurized water reactor (PWR) steam generators leads to reduced heat-transfer efficiency, increased corrosion risk, and lower plant output. Polyacrylic acid (PAA) is used as a polymeric dispersant to inhibit fouling and promote removal of iron-based deposits. Reliable measurement of low-level PAA in secondary feed water is essential to ensure dosage remains within operational limits and supports effective corrosion control.

Objectives and Study Overview

This work aimed to establish a simple, robust size-exclusion chromatography (SEC) method capable of quantifying PAA at concentrations below 20 µg/L in secondary feed water. The method needed to separate PAA from common feed-water additives, namely ethanolamine and hydrazine, and deliver accurate results in both simulated and real plant samples.

Methodology

• Chromatographic separation by SEC using an Acclaim SEC-1000 column (7.8 × 300 mm, 1000 Å pore).
• Eluent: ultrapure deionized water; flow rate: 1.0 mL/min; column temperature: 30 °C.
• Injection volume: 300 µL, detection by UV absorbance at 200 nm.
• Calibration: six-point curve from 5 to 200 µg/L PAA, quadratic fit (r2 > 0.999).
• Determination of method detection limits (MDLs) by seven replicate injections: ~2.2 µg/L in water and ~2.6 µg/L in real feed water.

Applied Instrumentation

• Thermo Scientific Dionex ICS-5000+ chromatography system (SP Single Pump, DC Detector/Chromatography compartment).
• Dionex AS-AP autosampler with 5.0 mL syringe and buffer line.
• ICS-Series variable-wavelength detector for ion chromatography (VWD-IC, 200 nm).
• Dionex Chromeleon CDS software version 7.1.

Main Results and Discussion

• PAA eluted at approximately 2.92 min with clear resolution from ethanolamine and hydrazine peaks, confirming no matrix interference.
• MDLs were determined as 2.16 µg/L in DI water and 2.55–2.60 µg/L in simulated and real secondary feed water.
• Spike-recovery tests at 6, 10, and 20 µg/L PAA yielded recoveries of 99.5–109% in both simulated and plant samples.
• Precision studies (n = 7) showed retention time RSD ≤0.7% and peak area RSD ≤6.6% across matrices.

Benefits and Practical Application of the Method

The water-only eluent eliminates the need for buffer preparation and minimizes UV background at 200 nm. The straightforward sample handling protocol and robust chromatographic performance make this method cost-effective for routine monitoring of PAA concentration in nuclear power plant secondary feed water.

Future Trends and Potential Applications

• Integration of on-line SEC monitoring for real-time PAA dosage control.
• Extension of the technique to other polymeric scale inhibitors used in power plant water treatment.
• Coupling SEC with advanced detectors, such as mass spectrometry, for polymer molecular-weight profiling.

Conclusion

A sensitive, reproducible SEC method was developed for quantifying low-level PAA in complex feed-water matrices containing ethanolamine and hydrazine. The approach offers nuclear plant operators a reliable analytical tool to support corrosion mitigation strategies.

References

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