Environmental Impact Statement - radioactive monticello

Appendix G
The staff noted that the offsite economic cost risk at Monticello is larger than that estimated at
other sites having similar core damage frequency and population doses. In response to-the
staff's RAI, NMC stated that the economic value parameters used as input to the Monticello
MACCS2 analyses are consistent with industry guidance, and produced results that are
considered to be appropriate for the Monticello site. Upon further review by the staff, the
differences in offsite economic cost risk between sites appear to be due to the differences in
the site-specific 50-mile population distributions.
The staff concludes that the methodology used by NMC to estimate the offsite consequences
for Monticello provides an acceptable basis from which to proceed with an assessment of risk
reduction potential for candidate SAMAs. Accordingly, the staff based its assessment of offsite
risk on the CDF and offsite doses reported by NMC.
G.3 Potential Plant Improvements.
The process for identifying potential plant improvements, an evaluation of that process, and the
improvements evaluated in detail by NMC are discussed in this section.
G.3.1 Process for Identifying Potential Plant Improvements
NMC's process for identifying potential plant improvements (SAMAs) consisted of the following
elements:
* Review of the most significant basic events from the Levels 1 and 2 PSA,
" Review of Phase II SAMAs from license renewal applications for seven other U.S. nuclear
sites,
* Review of potential plant improvements identified in the Monticello IPE and IPEEE, and
" Review of seven dominant room/burn areas, and SAMAs that could potentially reduce the
associated fire risk.
Based on this process, an initial set of 40 candidate SAMAs, referred to as Phase I SAMAs,
was identified. In Phase I of the evaluation, NMC performed a qualitative screening of the initial
list of SAMAs and eliminated SAMAs from further consideration using the following criteria:
* The SAMA is not applicable at Monticello due to design differences,
* The SAMA is of low benefit in boiling water reactors,
August 2006 G-13 NUREG-1437, Supplement 26 I