Vaporisation rates of CsOH and CsI in conditions simulating a severe nuclear accident

The vaporisation rates of volatile fission product compounds are critical p arameters for modelling aerosol formation following a severe nuclear accide nt. The vaporisation of CsOH and CsI was studied in a pure steam atmosphere at ambient pressure (85-89 kPa) by increasing the temperature of the flow furnace up to 1000 degrees C. For this purpose, samples were doped with a s mall amount of radioactive tracer. The vaporisation rate was then determine d from the decrease in sample activity with time, using a germanium gamma d etector placed outside the furnace. Calculated vaporisation rates obtained by solving complete velocity, temperature and vapour concentration profiles surrounding the sample with FLUENT CFD-software, were in reasonable agreem ent with the data. A simple engineering calculation agrees almost perfectly with the FLUENT results, if a constant valuer Sh approximate to 8, for the Sherwood number is used. (C) 2000 Elsevier Science Ltd. All rights reserve d.