Modeling hideout processes in prototypical tube/tube support plate heated crevices

Over the past several years, several forms of corrosion of steam generator tubing have been a problem of significant concern. In local crevices and occluded regions, restricted flow combined with excessive heat fluxes results in the local concentration of non volatile impurities. Corrosion products and particulate matter accumulate in the form of porous deposits to create an aggressive environment leading to corrosion. A detailed model of the transport processes that processes that produce concentrated solutions locally in pressurized water reactor steam generators has been developed. The model describes the heat, mass and momentum transfer processes that occur in porous deposits of the crevices. The model is used to predict the concentration of a species in the pore solution as a function of time and at steady state and the model predictions are compared to available experimental data. Rockwell International has constructed a device which mimics the geometry and operating conditions of a Tube/Tube support plate crevice in a pressurized water reactor steam generator. This apparatus is instrumented to measure the crevice chemistry as a function of time. Under conditions with caustic contamination, solutions were extracted from the crevice and the bulk while the system was operating at temperature.The mass of caustic accumulated was measured as a function of time. A similar simulator has been utilized by San Jose State University. Using feed solutions of 30, 60, and 120 ppm sodium chloride and crevice powers of 85, 150 and 230 Watts, San Jose State University has measured the mass of sodium chloride in the packed crevice as a function of time. The application of the model to the experimental data obtained by Rockwell International and San Jose University is described in this paper.The modeling predictions were in good agreement with the experimental results. (authors)