Modelling magnetite particle deposition in nuclear steam generators and comparisons with plant data

A computer code called SLUDGE has been developed that can be used to model secondary-side steam generator (SG) fouling as a function of time and operating conditions while still providing details of the deposit distribution throughout the SG. Tube deposits are predicted to grow at average rates of 4.4 and 1.1 μm/a on the hot side and cold side of the bundle, respectively. This is in good agreement with available plant data. SLUDGE under-predicts the magnitude of the tubesheet deposit, which implies that mechanisms in addition to gravitational settling may be responsible. One such mechanism, centrifugal separation of particles from the fluid streamlines, increased deposition towards the periphery of the tubesheet, but did not predict a realistic sludge pile. Comparison between the deposits on the horizontal surfaces of the tube support plates and the tubesheet suggests that the rate of particle removal at the tubesheet may have been overestimated. SLUDGE predicts a kidney-bean shaped sludge pile on the tubesheet when the re-entrainment rate is set equal to zero. (author). 17 refs., 1 tab., 6 figs