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The absolute maximum fast flux is of special interest because of its
effect in Limiting the graphite lifetime and, thus, in defining the core
size. The maximum danage flux calculated in this study occurs near the
edge of the inner core and Fs, at full powerrr
In 30 years at 75% capacity factor, this leads to a fluence of 2.7 x
m-’ (2.7 x loz2 ~ m-~), which is well below the nominal graphite
damage limit of 3 x lo2‘ m-2 (3 x 10” cm-21,
3.1.5.3 Spectral and cross-section effects
A summary of relative absorptions, fission neutron productions, and
neutron flux by energy group is shown in Table 12. Many of the captures
are in the resonance range, largely in thorium and ’”u, which leads to a
larger absorption fraction in that group. In contrast, most ~f the fis-
sions are caused by thermal ~eutr~ns.
N ~ U ~ ~ Q I I
Relative Fraction of Fraction of
energy neut koa neutron fission neutrons
group flux absorptions produced