SUBJECT: COMMENTS ON NRC PROPOSED RULE ...

6. ALTERNATE PLANT CONFIGURATIONS
As indicated in Section 4, a number of the design options were
selected for further development or conceptual design. It should be
noted that the designs developed to implement these options are only
examples. That is, there may be other designs which accomplish the
sve,purpose. Also. these concepts. as developed, relate primarily to
PWR plants, although similar ideas may be applicable to BWR plants.
During the initial stages of the conceptual design work, it became
apparent that two of the options could be combined. Thus, after these
options were combined, conceptual designs and cost estimates were
developed for the following:
1. Hardened enclosures for makeup water tanks (1.8).
2. Physicclly separated and protected redundant trains of eafety
equipment (11.5). his includes separation of containment
penetrations for redundant trains of safety equipment
(II.l).)
3. Hardened decay heat removal system (IV.1).
In addition, the possibility of additional isolation of low-pressure
connections to the primary coolant system (111.1) was examined and the
cost estimated, although no new designs were created.
The conceptual designs and the associated cost estimates are
discussed in detail in Appendix G. The cost estimates are summarized
in Tabla 6-1,which shows the estimated total costs for the design
alternatives as well as the cost increase relative to the reference
plant. The reference plant does not include the additional protective
features in its design. Only cost differences were estimated in the
case of options 11.5 (including 11.1) and 111.1. and,therefore, only
cost increases are tabulated. These estimates, which are in 1978