Analysis and characterization of deposit in filters of the stator cooling system of a Nuclear Power Plant

Abstract

In the stator cooling system of a Nuclear Power Plant, it was found that its filters were frequently saturated and a black solid deposit was found on its surface. The objective of this study was to analyze and characterize the material found on the filters and to determine its origins.  In order to achieve that, in first place a copper analysis was carried out using Total Reflection X-Ray Fluorescence (TRFX) and the percentage of organic matter (MO) of the solid was studied through calcination.  In a following step, to extend the characterization of the filter material, the solid was studied by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDAX) and by Fourier Transform Infrared Spectroscopy (FTIR).  For the determination of the origin, two main studies were carried out, on one hand; the water from the cooling system was analyzed by the inspection of filters placed downstream of the saturated filter, with SEM-EDAX. On the other hand, an extract from the hose used for the drying operation was studied by FTIR and SEM-EDAX methods, in order to determine if the deposit found in the filters could be related to its degradation and the consequent introduction of impurities into the system. From the analysis and characterization of the deposit in the filter, it was concluded that it was composed of a mixed organic and copper oxide matrix, the latter expected according to the materials of the system. The MO content was high and the FTIR analysis reflected the presence of vinyl bonds, indicating that the deposit is mainly composed of organic remains that are consistent with the material of the hose and its consequent degradation.