Summary of the 7th Technical Advisory Committee (TAC) Meeting
Date:
Place:

May 22 – 26, 2017
Nuclear Risk Research Center (NRRC), Central ResearchInstitute of Electric Power Industry

Participants:
TAC:
Mr. Stetkar (Chair), Mr. Afzali, Dr. Chokshi, Mr. Miraucourt,
Prof. Takada, Prof. Yamaguchi
NRRC:
Dr. Apostolakis (Head), Experts of the Nuclear Risk ResearchCenterIndustry:
Experts of TEPCO Holdings, TEPCO SYSTEMS, Shikoku
EPCO for respective topics

Proceedings
All topics were discussed in full committee. In addition, two discussion
sessions took place with lectures by Mr. Stetkar and Mr. Afzali on Failure
Criteria and RIDM in Design respectively.
May 22 (Mon.)
Topic 1: External Natural Event Research NRRC presented the current R&D status of the “Tornado”, “Senior
Seismic Hazard Analysis Committee (SSHAC) Project at Ikata 3”, and“Tsunami PRA”.
 TAC members commented as follows:- High winds of typhoon may be a more significant risk than tornado.
It is important to consider this factor in risk assessment for NPP.
- Various parameters of a tornado (rotation speed, moving velocity,path width, path length, etc.) have a correlation. You should consider
this interrelationship in modeling the tornado hazard.
- You should be cautious about excessive confidence in the results fromsingle research papers regarding ground motion modeling. Severalmodels should be reviewed and considered in the uncertainty
analysis.
- Median Tectonic Line is a significant contributing factor to theseismic motion evaluation of Ikata3. Uncertainty in estimating
seismic motion due to MTL should be examined.
- As to the methodology to determine scenario tsunami conditions for1

tsunami fragility analysis, you should explain the meaning and roleof the hazard control point (CP) in more detail.
（Handouts）
1-1. Estimating tornado and typhoon wind hazards
1-2. Tornado Missile Strike Probability Assessment
1-3. An Estimation Method for Tornado Missile Strike Probability underAssumption of Statistically Isotropic Tornado Path Directions (Reference)
1-4. Current Status of Ikata SSHAC Level 3 Project
1-5. Determination of scenario tsunami conditions for fragility assessment basedon hazard disaggregation
May 23 (Tue.)
Topic 2: Risk Assessment Research NRRC presented the current R&D status of “Human Reliability
Assessment (HRA) Guide” and “Fire PRA Guide”.
 TAC members commented as follows:- From the experience of the US, the process of timeline creation isvery important for HRA. It would be better to state explicitly how todevelop a timeline in the guide. Times should be derived from thesimulator or plant-specific thermal-hydraulic analyses.
- The HRA guidance should describe how to perform a "timeuncertainty analysis" and how to account for that analysis during
quantification of the human error probabilities (HEPs).
- The HRA guide should provide one or more practical examples thatshow how a deviation scenario is developed and how it is included ina PRA model.
- To collect past fire events, some ingenious ways should be consideredsuch as getting access to the logbooks of the NPP fire brigades.
- The proposed screening approach of the fire events should bereexamined to avoid improper screening-out.
- All tasks of the fire PRA guidance should be tested in an integrated
pilot application for a Japanese NPP before the guide is issued forgeneral use.
(Handouts)
2-1. NRRC HRA Guide Combining the NRC Narrative Approach with the EPRI
HRA Calculator22-2. Implementation Guide on Human Reliability Analysis (HRA) for PRA
2-3. Current Status of the Fire PRA Research Activities

May 24 (Wed.)
Topic 3: Risk-Informed Decision Making (RIDM) Promotion Team and Pilot
Projects• TEPCO and TEPCO SYSTEMS presented the current status of theKashiwazaki-Kariwa (KK) 6/7 pilot project. Shikoku EPCO presented
the current status of the Ikata 3 pilot project.
• NRRC presented the current status of the activities of the RIDMPromotion Team.
• TAC members commented as follows:- The initiating event groups should carefully account for transientsand a comprehensive list of plant-specific support system failures.
- The review of seismic PRA should be held at the NPP site because it
necessitates an actual plant walk-down. Also, experts of both systemand fragility should participate in the review.
- It is strongly recommended that operators at the site be involved inall stages of PRA model development.
（Handouts）
3-1. KK-7 Project, Internal Event Operating Level 1 PRA Model, Sophistication
Progress Report
3-2. KK Project – Comments & Answers
3-3. Ikata Unit3 Project Status Update
3-4. Expert meeting summary
3-5. RIDM Promotion Team Status Update
May 25 (Thu.)
Topic 4: Discussions on Failure Criteria and RIDM in Design
 “Discussion on Failure Criteria” took place with a lecture by Mr. Stetkar
and a presentation of NRRC. “Discussion on RIDM in Design” took placewith a lecture by Mr. Afzali and a presentation of NRRC.
(Handouts)
4-1. Comments on Plant-Specific Failure Data (Mr. Stetkar)
4-2. Component Failure Analysis Examples from Ikata 34-3. Discussion on Risk Informed Decision Making Applied in Design of3

Nuclear Power Plants
4-4. Direction of Risk Informed /Performance Based Design Application
related to Seismic Evaluation
4-5. Technology Inclusive Risk-Informed, Performance-Based Design andLicensing Technical Requirements for Non-LWRs (Mr. Afzali)
Topic 5: Exit Meeting
TAC and NRRC had a discussion on how to organize future meetings.
May 26 (Fri.)
Committee internal meeting.

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