A method for calculating the coating stress distribution resulting from the statistical spread of geometrical parameters in irradiated fuel particle batches has been developed by Gulden et al. The existing method utilizing coated particles is extended in two ways:

  1. A more realistic treatment of the buffer layer is adopted, taking into account its physical properties.
  2. A statistical distribution according to Weibull has been adopted for the silicon carbide layer strength.
Calculations with both the new and the old assumptions were performed on one feed particle and one breed particle type. It is shown that the two modifications influence the results of the original method. It was found that the extension of the first assumption has no influence on the stress distribution and the fraction of breaking feed particles, but it changes the stress distribution of the breed particles significantly. The fraction of broken particles at end burnup is increased by a factor of ∼10. The extension of the second assumption affects the fraction of broken feed as well as that of the breed particles. Depending on the Weibull parameter, m, the number of failed feed particles increases by a factor of 1.3 to 2; the corresponding factor for breed particles is between 3.5 and 60.