two types of host rocks. The contour line in red color, referred to as the critical
contour line, indicates the nominal criticality criterion, k eff = 0.98. The triangular
region results from the fact that the HMVF cannot be greater than VVF. In either
case of rock, the k eff value tends to be greater for a greater value of VVF (i.e., to the
right along the horizontal axis). A maximum k eff is observed as HMVF increases for
a fixed VVF. If the VVF is 0.094 or smaller for sandstone Fig. 4 (a) and 0.265 for
iron-rich rock Fig. 4 (b), then the uranium deposition is always subcritical. We call
this threshold VVF as the minimum critical VVF hereafter. The comparison
between sandstone and iron-rich rock shows importance of rock compositions. For
the iron-rich rock, the likelihood of criticality event would be significantly smaller
because iron strongly absorbs neutron.
Fig. 4 a k eff contour plot for
fractured sandstone with
fractured geometry I. b k eff
contour plot for iron-rich rock
with fractured geometry I
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X. Liu
contour line, indicates the nominal criticality criterion, k eff = 0.98. The triangular
region results from the fact that the HMVF cannot be greater than VVF. In either
case of rock, the k eff value tends to be greater for a greater value of VVF (i.e., to the
right along the horizontal axis). A maximum k eff is observed as HMVF increases for
a fixed VVF. If the VVF is 0.094 or smaller for sandstone Fig. 4 (a) and 0.265 for
iron-rich rock Fig. 4 (b), then the uranium deposition is always subcritical. We call
this threshold VVF as the minimum critical VVF hereafter. The comparison
between sandstone and iron-rich rock shows importance of rock compositions. For
the iron-rich rock, the likelihood of criticality event would be significantly smaller
because iron strongly absorbs neutron.
Fig. 4 a k eff contour plot for
fractured sandstone with
fractured geometry I. b k eff
contour plot for iron-rich rock
with fractured geometry I
274
X. Liu