Having obtained the component mean fluence, tem­perature, and weight loss, the variation of these para­meters throughout the particular component of interest is required.

The fluence reduces exponentially away from the fuel in the radial direction, but is influenced by surrounding fuel sources. The exact distribution is usually calculated using a reactor physics code for a 5 x 5 array pertinent to the area of interest. Figure 14 is an example for the Windscale Piles.

Thus, the spatial and temporal fluence distribu­tion throughout a graphite component can be calcu­lated. The component temperature can be calculated using finite element analysis through knowledge of the surrounding gas temperature, accounting for the

5% of the reactor heat which is generated within the graphite. Graphite weight loss variation within a component is more complex and is calculated by various empirical industry codes. If the axial variation in fluence, temperature, and weight loss along the brick length is deemed to be important, three-dimen­sional physics, temperature, and weight loss calcula­tions will be required.