Aluminum oxide film thickness and emittance.

摘要

Aluminum reactor components which are not actively cooled could be subjected to high temperatures due to gamma heating after the core coolant level dropped during the ECS phase of a hypothetical LOCA event. Radiative heat transfer is the dominant heat transfer process in this scenario and therefore the emittance of these components is of interest. Of particular interest are the safety rod thimbles and Mark 60B blanket assemblies; for the K Reactor, these components have been exposed to low temperature (< 55(degrees)C) moderator for about a year. The average moderator temperature was assumed to be 30(degrees)C. The Al oxide film thickness at this temperature, after one year of exposure, is predicted to be 6.4 (mu)m (plus minus) 10%; insensitive to exposure time. Dehydration of the film during the gamma heating accident would result in a film thickness of 6.0 (mu)m (plus minus) 11%. Total hemispherical emittance is predicted to be 0.69 at 96(degrees)C, decreasing to 0.45 at 600(degrees)C. Some phenomena which would tend to yield thicker oxide films in the reactor environment relative to those obtained under experimental conditions were neglected and the predicted film thickness values are therefore conservative. The emittance values predicted for a given film thickness are also conservative. The conservativisms inherent in the predicted emittance are particularly relevant for uncertainty analysis of temperatures generated using these values.