The purpose of this presentation was to review the conditions analyzed by the base case team and summarize the calculated results to date. This talk served as a prelude for the next four presentations by the base case team members.

The base case results will be used to anchor elicitation responses by the elicitation panel members as part of their individual elicitations. The elicitation members can use one or all of the base case results directly for their anchoring, or provide their own base case analysis if they choose. There were a total of five (5) base cases defined at the first elicitation meeting in February, see Table B.2.1.

As part of the base case effort, the base case members were to evaluate the LOCA frequencies at 25 years (current-day), 40 years (end-of-plant-license), and 60 years (end-of-plant-license-renewal). These results will then be used by the individual elicitation panel members to anchor their respective responses so that they can estimate the various LOCA frequencies at these same time periods.

The goal for the base case members is to calculate results for the set of conditions listed in Table B.2.1. The base case members also shared their results and presentations prior to this meeting so that there was a common format for the presentations. At this time the base case results comparison charts in the handouts should be viewed as works in progress. Furthermore, some results from Vic Chapman (OJV Consultancy) are still forthcoming. Vic and Chris Bell need to provide additional information to the panel members on how they conducted their base case analyses.

The current base case results are summarized in slides 16 through 20 of this presentation. For David Harris’s calculations, the frequency results at 60 years were averaged over the 20 year time period from 40 to 60 years while the 25 year estimates were averaged over the first 25 years of operation. It is important that results are consistent (with consistent assumptions and conditions) among each base case team member.

The hot leg results (PWR-1 on page 18 of the handout) indicates large initial uncertainty. Bruce Bishop questioned if the results are for individual welds or the overall system. The response was that the intent was that these results should reflect the frequencies for the overall system. It was pointed out that the hot

leg results should reflect the LOCA frequencies for the hot leg only. The results should not consider all the other lines associated with the RCS, i. e., the cold leg, cross over, surge line, etc.

The slides 21 and 22 (Remaining Work and Differences Among Methodologies) of Rob’s presentation (Base Case Conditions and Summary Results) were not included in the handout and were to be filled out later by the team members. These updates will be posted on the ftp site once available. It was indicated that the LOCA frequencies for the lower leak rate categories (> 100 gpm [380 lpm]) include all the incidences of LOCAs in the higher leak rate categories, e. g., the 100,000 gpm (380,.000 lpm) bin should include all incidences of LOCAs in the 500,000 gpm (1,900,000 lpm) bin.