SUBJECT: COMMENTS ON NRC PROPOSED RULE ...

Plant Layout Modification -- Physical separation of redundant
vital systems implies sufficient isolation to eliminate connnon induced
failures. Such separation could include component relocation, cable
and piping rerouting, and the addition of barriers to increase com-
partmentalization. In contrast to separacior., relocation of vital
equipment into more protectable configurations could include colocat-
ing components with similar vulnerabilities into hardened compartments
(e.g., a motor control center) or locating the spent fuel pool below
grade. iolocation requires careful analysis, however, ts balance
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vulnerability should the hardened compartment be breached;
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increased protectability of compact locations against the increased
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System Design Changes -- Independence of the ac and dc electric
power trains requires that each train be self-sufficient. For this
goal to be achieved, each train must have its own buses, cables,
switchgear, batteries, battery chargers, and diesel generators. fir-
thermore, the trains could be housed in separate buildings between
which there is no direct access. The analysis examines the increased
construction costs associated with such canplete separation and the
costs due to associated effects on operations. Complete separation
also implies that cooling water, fuel, and ventilation for the diesels
must be separated and protected in some manner. The assumption that
such separation enhances safety is examined.
An examination of damage control options may also suggest system
design modifications which could enhance the likelihood of successful
dnmage control. Such design changes might inilude the addition of
blind flanges in certain cooling systems, which could be opened to
connect alternate water supplies or bypass disabled components. The
changes might also include the provision of standby pumps and trans-
formers. Previous alternative containment design studies23 were
reviewed to examine the potential effectiveness of such alternatives
againmt aabotaqe incidents and aqainst the cost associated with the
changes.