A study of fission product transport from failed fuel during N reactor postulated accidents

This report presents a study of fission product transport behavior in N Reactor during a severe accident. More detail about fission product behavior than has previously been available is provided and key parameters that control this behavior are identified. The current report is an extension to a previous interum study that has added an aerosol formation model, replaced an older aerosol deposition model with an improved correlation, and incorporated results of a revised analysis of the process tubes. The LACE LA1 and LA3 tests are used to assess the revised model applied to determine aerosol deposition. The study concludes that a cesium iodide aerosol is likely to form near the downstream end of the process tubes. Transport of most of the released cesium and iodine as well as less volatile material depends on the behavior of this aerosol and the behavior is sensitive to several parameters that are not well known. If the environment is very clean and effluent flow is sufficient to support oxidation of the zircaloy and uranium of the process tubes, almost none of the aerosol deposits in the riser. Reduction of the effluent flow or the presence of high concentrations of aerosols of very low volatile material like zirconium, uranium, or their oxides causes deposition of the fission products in the riser piping. 24 refs., 18 figs., 11 tabs.