Raman spectroscopy for in-situ characterisation of steam generator deposits

Fouling of secondary-side of nuclear steam generators by corrosion products transported by the feedwater is a serious problem. The build-up of deposits on the tubes can lower the heat transfer and provide sites for localised corrosion by the impurities. The deposits are removed by chemical and/or mechanical cleaning techniques. For the optimal conditions and procedures, the composition of the deposits is required. This composition also gives information on the chemistry conditions within the steam generator and feedtrain. At the present time, samples of deposits are removed from the steam generator and characterised ex-situ. In this procedure the sample may undergo chemical and physical surface changes. Hence an in-situ technique for determining the chemical composition of the compounds present would be valuable. This paper describes the development of a remote characterisation technique based on vibrational spectroscopy. The remote Raman spectroscopy uses fiber optics to transmit laser energy to the inspection region and scattered light back to the spectrometer. Thus Raman spectroscopy is applied to make in-situ deposit analysis. Raman spectra of some of the more common chemical compound in the deposits are presented