Survey and characterization of feedwater venture fouling at nuclear power plants. Volume 1, Feedwater venturi fouling: Final report

Fouling of feedwater venturis in nuclear power generating plants was investigated by a survey of seven plants and by venturi inspections and deposit analyses at three plants. The information in this report will be useful to plant operators and chemists and to those involved in venturi manufacturing and calibration. Video inspection and SEM/EDS analyses show that deposits follow machining and polishing marks and that deposits accumulate on areas of abrupt flow transition. Also, corrosion of copper alloys downstream of the condensate polishers results in venturi fouling. The results indicate that feedwater venturi fouling can be minimized by (a) minimizing sharp flow transitions and turbulence within the venturis, (b) enhancing the surface smoothness, for example, by electropolishing, (c) minimizing copper-bearing alloys in the balance-of-plant, especially downstream of the condensate polishers, (d) minimizing exposure of the venturis to high concentrations of corrosion products during preoperational cleanup, and (e) minimizing the design velocity and/or pressure drop through the venturis. Alternate water chemistry, such as morpholine or other amines, for reducing venturi fouling was not investigated since most PWR plants had only recently converted to an alternate chemistry.