Figures L.2 and L.3 show the effect of the industry and regulatory safety culture, respectively, on the LOCA Ratio (i. e., the ratio of the LOCA frequency in the future to the LOCA frequency at 25 years) for Category 1 LOCAs. Figures L.4 and L.5 show the effect of industry and regulatory safety culture on the

LOCA Ratio for Category 4 LOCAs. Ratios less than 1.0 are indicative of a perceived reduction in the LOCA frequency as a result of improvements in the safety culture mindset. As can be seen in these figures, the panel members overwhelming expected the safety culture to either improve or remain constant over the next ten to fifteen years and beyond. The panel felt that the industry as whole was acting in a consistent manner. However, a few plants with a less diligent safety culture mindset would provide the greatest challenge from a LOCA perspective. It was thought that these outlier plants may not affect the mean trends, but could strongly influence the bounds. The Davis-Besse experience was frequently cited as an example of this effect. The panel also expressed the opinion that the industry and regulatory safety culture are highly positive correlated. Therefore, regulatory and industry changes are expected to occur virtually simultaneous.

Figure L.2 Effect of Utility Safety Culture on Category 1 LOCAs

LOCA Ratio: Future/Current

Figure L.3 Effect of Regulatory Safety Culture on Category 1 LOCAs

LOCA Ratio: Future/Current

Figure L.4 Effect of Utility Safety Culture on Category 4 LOCAs

L-4

LOCA Ratios: Future/Current

Figure L.5 Effect of Regulatory Safety Culture on Category 4 LOCAs

As can be seen in comparing Figures L.2 with L.4 and L.3 with L.5, the panel members felt that any improvements in safety culture would be more beneficial for the smaller LOCA categories than their larger counterparts because the smaller LOCA categories constitute the bulk of the experience base. The frequency of the larger LOCA categories due to safety culture effects is expected to remain relatively constant over time.

The bottom line from this discussion is that because the panel members felt that the effect of safety culture was relatively minor, the LOCA frequencies developed during this exercise were not modified to account for this effect. The main caveat to this general conclusion is the previously mentioned concern that the LOCA frequencies developed through the elicitation process could be significantly degraded by a safety-deficient plant operating philosophy. The other concern frequently expressed was that the industry safety culture mindset may deteriorate near the end of a plant’s license as management tries to “squeeze out” the final few years of operations without investing in the necessary maintenance activities. Also, near the end of the plant’s license there was a concern expressed that the morale of the plant’s operating staff may begin to erode as they foresee a potential loss of employment. These concerns are manifested in the higher LOCA Ratios for the 60/25 year results when compared with the 40/25 year results in Figures L.2 through L.5.