15.74. Compared with present large reactors having electrical gener­ating capacities in the 1000-MW range, we have seen that smaller passive reactors in the 600-MW(el) range have a number of attractive features. The new designs are simpler since the passive features eliminate the need for some active safety systems. They generally are more forgiving to op­erator and system failures and are designed to have longer plant lifetimes. They have generally received favorable public attention since press de­scriptions have emphasized that the industry has something new to offer in safety.

15.75. The smaller plants can be built faster, an attractive feature that reduces the indirect construction costs. Also, for a utility considering a restart of its nuclear program, a smaller reactor would require less financial exposure than a large plant and might be more commensurate with load growth requirements. Siting for a smaller plant is likely to be easier.

15.76. Opinions differ regarding whether or not the inherent economy of scale advantage of the large plant can be counteracted by the system simplification and manufacturing advantages of the smaller plant. Although cost estimates for the large evolutionary plants yield about the same results as those for the smaller passive plants, the former estimates are based on proven systems and are therefore likely to be more reliable. Furthermore, it has been pointed out that the large fraction of the capital cost required for the nonnuclear part of the plant is subject to the scaling factor, leading to the conclusion that on a unit energy basis, generating costs for the large plant are likely to be less than for the smaller plant. However, until more information becomes available, it appears that a size preference should be based on considerations other than the economy-of-scale issue.