High-temperature spontaneous Raman spectra were collected for aqueous chemical species of interest to the power generation industry. These spectra were collected at temperatures between 22°C (72°F) and 300°C (572°F) and at pressures sufficiently high to maintain single-phase aqueous solutions. Spectra were obtained for pure water and aqueous solutions of sodium hydroxide, ammonium hydroxide, morpholine, sodium sulfate/bisulfate, sodium carbonate/bicarbonate, sodium phosphate, and sodium silicate at concentrations between 0.01% (100 ppm) and 10% by weight. Concentrations in this range are expected within crevices and under deposits in steam generators, boilers, and turbines in both fossil and nuclear power plants. Also, high-temperature spontaneous Raman spectra were collected for mixtures of sodium hydroxide, boric acid, sodium sulfate, disodium phosphate (DSP), potassium chloride, and hydrochloric acid.
These laboratory experiments demonstrated the feasibility of making in situ, real-time chemical measurements at locations that are frequent sites of corrosion damage resulting from highly concentrated aqueous solutions. The measurement techniques were quantitative and capable of uniquely identifying chemical species, such as sulfate and bisulfate ions, at elevated temperatures. The upper test temperature is not a technical limitation and was chosen because it corresponds to a typical temperature within commercial nuclear steam generators.