Rob stressed that prior to their individual elicitations, each panel member needs to do their homework and answer as many of the elicitation questions as possible. Panel members can change their answers at any time during this exercise, including during the actual elicitation and afterwards.

It was indicated that the term “LOCA frequencies” should really be “LOCA probabilities” in this presentation during the analysis of the conditional emergency loading. Rob agreed to make this change to the presentation.

Pete Riccardella questioned whether we should expand the conditional seismic loads to conditional emergency and faulted loads which include transients like water hammer as well as seismic. Fred Simonen thought that we needed to talk with the PRA people. Alan Kuritsky (USNRC) indicated that these other potential LOCA causing events were currently not included in the PRAs. Rob suggested tabling this discussion until later in the agenda. Bruce Bishop thought that if we continued with the traditional seismic approach then we need to consider the fact that the snubbers may not work probably. Bruce indicated that there is a significant probability that the snubbers may not work as advertised.

Rob next addressed the top down elicitation structure. Bill Galyean used a top down approach where he assigned an overall piping LOCA contribution, and then looked at the breakdown in the contribution due to piping system, geometry, load history, mitigation, materials, and degradation mechanisms. Vic Chapman questioned what the top down approach gave us (we start with the final answer that we are looking for). Lee Abramson indicated that at the end of the day we will get numbers in each of the blocks on slide 3 so that we can decompose the problem into the small pieces. The panel members can initially choose either a top down or bottoms up approach.

Bruce Bishop asked how soon the panel members are going to have the final base case results prior to the first elicitation. Rob indicated that he would be working with the base case members the week of June 9 to finalize their answers. He hoped to have the final results by the end of June. However, the base case conditions are well-known

The panel members need to supply their answers (on a pre-established form) and the facilitation team will work with the individual panel members individually. The important point of the pre-elicitation exercise is to quantify the median value results, provide some qualitative uncertainty and also rationale. During the elicitations the panel members can change answers as they interact with the facilitation team and points are clarified.

Bruce Bishop felt that the “utility safety cultural” should be “utility operations cultural” in that safety and economic drivers both feed into the operations cultural. Karen Gott indicated that the IAEA definition of safety cultural (and how we defined safety cultural at the kick off meeting) includes both safety and economic aspects. With regards to the ratios on safety cultural issues, ratios greater than 1.0 indicate that things are getting worse; less than 1.0 means things are getting better.

Slide 6 shows a flow chart in which the question is which variables are independent. Variables in this context are geometry, load history, mitigation, materials, and degradation mechanisms. For these variables, each panelist may need to estimate the future impact of that variable, e. g., what new materials, or what new degradation mechanisms, should be expected in the future. We may want to look at the past to estimate what might happen in the future (e. g., Gery Wilkowski’s plot of new failure mechanisms with time which shows a new mechanism approximately every 7 years).

There ensued a long discussion on the comparisons of reference cases (defined at the kick off meeting) with baseline cases. We defined a reference case for each piping system (e. g., diameter, material, degradation mechanism, etc) whereas we only defined a few baseline cases to which the reference bases are to be compared (i. e., anchored). For example, the hot leg (base case) may be a natural comparison for the reference case for the cold leg.

For Questions 3A.1 and 3A.2 (slide 7) and all related questions, Rob will change the “surge line” to “cold leg” example so questions don’t refer to a system that is both a base case and a reference case, realizing that we will end up asking same question for a surge line as well. For those systems which have both a base case and a reference case, these comparisons may be more natural and easier than inter-system comparisons.

It was decided to eliminate the assessment of which variables are independent or dependent. All variables will be considered to be dependent as originally defined during the kick-off meeting. Thus, the original Question 3A.2 will be eliminated. Other References to correlated or independent variables in other questions should be eliminated in the final presentation version. For original Question 3A.3, the requirement to list at least 80 percent gets the most significant contributions, but not all of them.

There was considerable discussion on what the panel members would need to provide for Question 3A.3 and 3A.4. We need to know what variables have a major impact on LOCA frequencies to quantitative that impact as best as possible. Lee Abramson tried to make the point that things would become clearer once individual panel members got into their elicitations and tried to put numbers to the answers to the questions.

A question was asked if any attempt is going to be made to look at plants and determine how many plants have a certain combination of variables (V1, V2, V3, etc.), and how many plants have another set of variables (V2, V4, V5, etc.), and how many have another set. It was noted that some variables will be important at certain plants and other variables will be important at other plants. Rob indicated that it would be nice to have such information, but it was not practical to get such information in the time frame we have. This could possibly be a follow-on effort. However, it should be stressed that the plant design information will not likely result in a significant change in the analysis. If certain designs do not contribute to the LOCA frequencies then they are not significant contributors and the panelists can focus on designs that do as long as they exist in several plants. If the population of the significant contributors is in error by 2 to 3, it will likely not matter.

The only issue to avoid during quantification is if you believe that only a few (1 — 2) plants of a certain design, operating experience, etc. significantly contribute to the generic LOCA frequencies. These plants should not be explicitly considered in these generic estimates. However, but possibly applicability of these generic results to those design conditions should be discussed during the elicitation.

Elicitation Question (EQ) 3A. 1 compares a base case to a reference case, then EQ 3 A.4 will use the impact of the important variables to compare other similar piping systems to the reference cases. Reference cases are the link back to the base case for which we will have actual LOCA frequency estimates. The panel members don’t have to do the mapping back to the base cases, the facilitation team will do that. Then the facilitation team will filter the results up (bottoms up approach) to get an overall LOCA frequency.

There was some discussion about how the facilitation team would integrate these results and how the panelists could account for these individual contributions.

Again, it was emphasized that if panel members are not comfortable in answering specific questions, then they need to say so. If the panel members need to make a crude assumption, then do so, but indicate that during the individual elicitations so the facilitation team can help estimate the level of uncertainty. Dave Harris thought that it won’t be clear to him how this all fits together until he starts the process. Then he is sure that he will have a lot of questions. Rob Tregoning and Lee Abramson told him, and the rest of the panel members, to call them for any clarification of questions. Rob also indicated that he will be contacting each panelist prior to their elicitation to discuss issues.

The flow chart on slide 9 is for a “top down” approach, much in the motif of what Bill Galyean discussed on Day 1. As part of this approach, one only needs to tie one system (of those identified as being important contributing systems to LOCA frequencies) to the base case since previously we had identified individual piping system contributions. One can make this connection through a reference case if not a base case system, or can tie directly to the base case if the system is a base case system. This approach may be more straightforward for people who need to integrate variables in mind, which might lead to more uncertainty.

Panel members can chose which approach to follow (top down or bottoms up), and they can switch back and forth depending on different systems. As part of their homework prior to their elicitation, they only need to do one approach, but the facilitation team may ask about each approach during the elicitation. There will be different tables to fill out with each approach. The bottoms up approach may be more rigorous with less subjectivity, but the top down approach may be easier to understand. One can get top down answers from the bottoms up approach, but can’t do reverse. By doing both approaches for certain systems, panelists can search for consistency in their analysis.

Rob discussed the elicitation questions related to non-piping components starting at slide 12. At the kick­off meeting in February we didn’t spend as much effort developing the base case and reference cases for non-piping components as we did for the piping systems. Thus, these gaps needed to be filled during the remainder of this meeting.

Slide 12 illustrates the flow chart for the “bottoms up” approach for the non-piping components. At the kick-off meeting, we had identified five (5) non-piping components to consider (pressurizer, valves, pumps, RPVs, and steam generators). In order to estimate the frequencies for these non-piping components, the panel members need to pick either a piping or non-piping base case for comparison. The facilitation team will integrate the results in a manner similar to the bottoms up approach for piping systems.

There was a question about the nature of the non-piping base case conditions, especially in light of the thorough discussion about the piping base cases during the previous day. We had originally planned to have precursor data for the non-piping base cases for comparison. However, we do not have data identified yet. We may have to drop the idea of using non-piping base cases and only have piping base cases to compare to. We will come back to this issue later in the afternoon.

Bruce Bishop felt that tying non-piping components back to piping base cases would be difficult. He foresaw lots of dissimilarities between non-piping and piping in failure mechanisms, etc. He suggested that we try our best to come up with some non-piping base cases. Even if we can’t come up with base cases for all 5 of the components, if we could come up with base cases for a few, that would be better than nothing.

Pete Riccardella asked if we have defined the failure mode for these non-piping components. Rob felt that we don’t have a clear definition at this time. Rob felt that we had to take more of a mechanistic viewpoint. There was also general confusion about the definition of “failure mode” for the non-piping issues. Rob indicated that this means the failure mechanism. It was agreed that “failure mechanism” is a preferable term and Rob will change the phrasing for the elicitation questions from “failure mode” to “failure mechanism” to avoid any confusion.

It was again emphasized that the panel members will not be asked to provide absolute LOCA frequencies. However, if a panel member prefers to think in terms of frequencies, they should feel free to do so. Elicitation questions will ask for relative comparisons with the base cases and other conditions. The facilitation team will then make the calculations to get the absolute LOCA frequencies. The panel members should make the best comparisons possible and are not compelled to answer questions in areas where they have no expertise.

Rob showed an example of a table that he may provide the panel members for them to fill out for EQs 3B.1 and 3B.2 for the top down approach, see Table B.2.2.

The complete set of tables to be filled out for the elicitation will be provided electronically by Rob. There will be a space for comments in each table row to initiate discussion during the elicitation process. The tables will be provided in Excel format. If a panel member wants to change the Excel spreadsheet format they should feel free to do so as long as the cell references for each answer remains unchanged. The final calculations will be done in Excel. Therefore, the elicitation results should be provided to Rob in the excel spreadsheets if at all possible. Hardcopies or MS Word versions of the tables can provide upon request.

Rob will provide the panel members with a copy of the spreadsheet that he will use to calculate LOCA frequencies sometime during the elicitation process. Rob will attempt to complete this spreadsheet to the individual elicitations so that the panel members can see how their responses reflect their calculated LOCA frequencies. However, this will be a lower priority than coordinating the information exchange among the expert panel and finishing the base case calculations.

Table B.2.2 Elicitation Questions 3B.1 & 3B.2