Rob Tregoning then made a presentation on LOCA frequency determination using expert elicitation. The objectives of this presentation are to motivate the expert elicitation effort, discuss the limitations of relying solely on past operating experience; present ongoing NRC-sponsored research in this area; define the objective of the expert elicitation; outline the approach; and discuss the structure of the kick-off meeting. Some of the specific key points from his presentation and subsequent discussion are outlined below:

• The LB LOCA design basis size will be determined by considering all relevant LOCA sources.

A PFM-based model is under development for predicting LOCA contributions as a function of break size. This code will also account for LOCAs from non-piping sources, and will include contributions from future unknown failure mechanisms. Expert elicitation input from this panel will be used throughout program development.

• The objectives of the elicitation are to

• Develop future SB, MB, and LB LOCA frequency estimates extending up through the end of the plant-license-renewal period (approximately 35 years).

• Develop benchmark problems and standardized inputs for conducting PFM simulations of LB LOCA events in important BWR and PWR systems.

• The elicitation approach will construct base cases. Quantitative LOCA estimates as a function of break size will be developed for these base cases. Then, important variables and issues will be discussed within the relative framework of the base cases.

Discussion: It was stressed that the base cases will just provide a reference point. Adjustments to the base cases will account for the impact of those issues which contribute significantly to the LOCA frequencies. These adjustments must consider their effect on current LOCA frequencies and their time dependence up through the end of the plant license-renewal period (~ 35 years).

• The programmatic approach for the elicitation was presented. It consists of the following important areas.

• Conduct the kick-off meeting

• Develop elicitation questions

• Allow individual study to develop answers for elicitation questions

• Conduct the individual elicitations

• Analyze results (facilitation team)

• Conduct a wrap-up meeting

Discussion: It was conveyed that when the facilitation team queries each elicitation panel member, best estimate answers will be sought as well as the uncertainty in the estimates. It was also stressed that each panel member need not answer all questions, but only those that they feel that they are qualified and comfortable with answering. However, people will be encouraged to answer all questions, even in areas outside of their specific expertise. Uncertain knowledge should be reflected in the uncertainty estimates. Rob Tregoning indicated that one job of the facilitation team will be to filter out responses which are not well-founded, and exclude them from the final analysis.

• The principal components of the kick-off meeting were reviewed again. There are several major objectives which need to be accomplished during this kick-off meeting:

• Present the elicitation objectives and define fundamental terms to ensure common understanding.

• Undergo elicitation training to understand the process and approach.

• Construct methodology for developing baseline LOCA estimates. Develop a classification scheme and approach for issues which could affect the baseline LOCA estimates.

• Identify and classify issues for consideration. Discuss issues as necessary for clarification.

• Agree on significant issues to include in the elicitation.

• Determine the structure of the elicitation questions.