Design for thermal stresses in probabilistic form in clad fuel plates

This paper presents equations for the mean values and standard deviations of thermal stresses developed in flat elements. These include clad fuel plates with uniform heat generation in the fuel zone and flat plate claddings with exponential heat generation. Inherent in these equations are the facts that (1) design variables are generally characterized by spectra of values, rather than by unique values, and (2) a small, but finite, probability of failure must be recognized in any design. By coupling the stresses due to the applied loading as calculated by the equations given in the paper with the strength available in a material, reliability (or the alternative probability of failure) can be calculated. Conversely, for a given reliability the appropriate dimensions can be determined. Appropriate illustrations of application of these equations are provided through tables and figures. The difficulty of relying on a factor of safety is demonstrated. (Auth.)