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NRR E-mail Capture - NEI Slides for May 22, 2018, Public Meeting on 50.69 Seismic Alternatives
	ML18142C215
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Issue date:	05/22/2018
From:	Ed Miller; Special Projects and Process Branch
To:	Ed Miller; Special Projects and Process Branch
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NRR-DMPSPEm Resource From: Miller, Ed Sent: Tuesday, May 22, 2018 7:32 AM To: Miller, Ed

Subject:

NEI Slides for May 22, 2018, Public Meeting on 50.69 Seismic Alternatives Attachments: 50 69 Seismic Categorization Alternatives Presentation 05-22-2018.pdf Slides for the subject meeting attached.

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Hearing Identifier: NRR_DMPS Email Number: 384 Mail Envelope Properties (BL0PR0901MB2386D0DCFC559C855554AE78E9940)

Subject:

NEI Slides for May 22, 2018, Public Meeting on 50.69 Seismic Alternatives Sent Date: 5/22/2018 7:31:41 AM Received Date: 5/22/2018 7:31:46 AM From: Miller, Ed Created By: Ed.Miller@nrc.gov Recipients:

"Miller, Ed" <Ed.Miller@nrc.gov>

Tracking Status: None Post Office: BL0PR0901MB2386.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 44 5/22/2018 7:31:46 AM 50 69 Seismic Categorization Alternatives Presentation 05-22-2018.pdf 2550452 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received:

50.69 Seismic Categorization Options Greg Krueger, NEI Greg Hardy, SGH Pat ORegan, EPRI John Richards, EPRI NRC Meeting May 22, 2018

50.69 Seismic Categorization Options Review of key seismic categorization issues Proposed process

- Graded

- Three-tiered

- Focused on 50.69 seismic insights and updated seismic hazard levels New sensitivity study for Tier 2 plants to consider insights from potential seismically correlated fragilities and seismic interactions Schedule moving forward Discussion and NRC feedback 2

NEI 00-04 Risk Informed Categorization - Seismic Inputs Gap in information available to implement NEI 00-04

- Some plants dont fit within any of the three available options IPEEE SMA equipment list SPRA risk insights SCDF < 1% of IE CDF

- Includes plants that did not perform an SMA for IPEEE, and were not required to perform an SPRA in response to Fukushima Key questions

- Do seismic considerations provide unique risk insights in the 50.69 categorization process?

- Would such insights drive SSCs to be HSS?

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Application of Risk Informed Decision Making The application of a seismic alternative approach to inform the 50.69 categorization process is an example of risk informed decision making (RIDM)

The incorporation of insights from contemporary seismic PRAs provide a perspective on the seismic risk contribution to the 50.69 categorization decision making process A graded approach based on site seismic hazard is employed to highlight consideration of potential unique seismic insights using existing PRA models 4

Premise Extensive seismic reviews performed over the last 5 years

- Plant walkdowns performed to validate design basis compliance

- Additional confirmation of IPEEE seismic resolution implementation

- New site-specific seismic hazard estimates

- NRC grading of plants based on comparisons of design basis vs new hazards Even for high seismic hazard plants, there are limited unique component level insights

- Sensitivity studies show SPRAs produce few (if any) unique HSS components

- Expected insights for low and medium seismic hazard plants would be even more limited

- 50.69 Integral Importance Assessment makes it even less likely that seismic unique components would be HSS at lower hazard sites 5

50.69 Seismic Categorization Sensitivity Studies Determined how many and what kinds of SSCs would be categorized as HSS due to different hazard PRA models

- High seismic ground motion plants with new SPRAs as test cases

- Identify HSS components based on importance measures for model types using Internal Events, Fire, and Seismic PRA models

- Compared risk-significant (HSS) seismic components to those derived from internal events and/or fire models Study four plants with high seismic hazards and new SPRAs 6

50.69 Categorization - Sensitivity Studies Plant A Plant C Results from Plants A and B were presented at the October 23, 2017 meeting Results from Plant C were presented at the Plant B Plant D January 18, 2018 meeting Results from Plant D are consistent with the previous 3 results 7

50.69 Seismic Categorization Sensitivity Studies Sensitivity studies from high seismic hazard sites show limited unique insights at the component level

- HSS SSCs identified in the seismic PRAs are also identified as risk significant in the IE PRA and/or Fire PRA

- In certain limited cases, correlated failures in the Seismic PRA can lead to some components being candidate HSS due to seismic

- Would expect only a handful of such unique components

- Unique seismic HSS components expected to be even fewer at low and medium seismic hazard plants 8

50.69 Seismic Categorization Proposed Tiers Tier 1 - Low Seismic Hazard Sites

- Plants where the GMRS peak acceleration is at or EHORZaJRUZKHUHWKH*056a66(

Tier 2 - Medium Seismic Hazard Sites

- Plants where the GMRS to SSE comparison is greater than Tier 1 but not high enough to be treated as Tier 3 Tier 3 - High Seismic Hazard Sites

- Plants where the GMRS to SSE comparison is high enough that the NRC required the plant to perform an SPRA to respond to the Fukushima 50.54(f) letter 9

50.69 Seismic Categorization Proposed Seismic Criteria Tier 1 - Low Seismic Hazard Sites

- HSS SSCs identified in IE PRAs, Fire (PRA or SSEL) and other NEI 00-04 criteria such that no additional seismic considerations are necessary.

Tier 2 - Medium Seismic Hazard Sites

- Seismic unique insights may be possible from seismically correlated fragilities or interaction concerns. Use seismic walkdowns and proposed sensitivity studies to identify those HSS insights.

Tier 3 - High Seismic Hazard Sites

- Unique seismic insights expected to be limited but difficult to exclude. Use SPRA in accordance with NEI 00-04.

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Tier 1 - Low Seismic Hazard Sites Low seismic hazard sites not expected to have unique seismic HSS SSCs

- Seismic not a driving risk in the integrated importance review

- HSS SSCs identified by IE PRA and Fire PRA and other NEI 00-04 criteria adequately address seismic risks Low seismic sites unlikely to identify unique seismic insights No explicit seismic assessment as part of the categorization process 11

Tier 2 Seismic Walkdowns and Sensitivity Studies Start with SSCs in categorized system Screen selected SSCs that dont need to be considered in seismic evaluation Use a walkdown to identify conditions that would meet seismic-correlated fragilities and/or seismic interaction criteria of the proposed approach Use IE PRA common cause failure modeling approach to identify the system components that exceed criteria of the proposed approach 12

Tier 2 Seismic Walkdowns and Sensitivity Studies SSCs in a system to be categorized

- Identify SSCs in the system to be categorized

- Group SSCs by seismic equipment class (e.g. MCCs, horizontal pumps) to facilitate further seismic evaluations 13

Tier 2 Seismic Walkdowns and Sensitivity Studies Screen selected SSCs that do not need to be considered in the seismic evaluation

- Screen out inherently rugged SSCs (would not be modeled in an SPRA)

- Screen out SSCs not used in functions that mitigate core damage or functions related to containment performance (do not contribute to CDF or LERF)

- Screen out SSCs that are already HSS in other 50.69 categorization evaluations (no need for further consideration) 14

Tier 2 Seismic Walkdowns and Sensitivity Studies Perform evaluations to identify SSCs that could experience seismic correlated failures or common interaction failures

- Perform walkdown to identify correlation and interaction conditions

- Consider plant-specific seismic capacity screening for items that would be unlikely to be dominant risk contributors

- Identify SSCs considered seismically correlated in SPRA

- Identify SSCs subject to common seismic interaction failures 15

Tier 2 Seismic Walkdowns and Sensitivity Studies Perform Common Cause type evaluation to identify HSS SSCs

- For SSCs identified as seismically correlated or subject to common interaction failures, create Seismic Common Cause Groups in the IE PRA

- Quantify LOOP/SBO and SLOCA events to determine F-V and RAW importance measures

- SSCs with F-V or RAW values above thresholds designated as HSS (IDP cannot override) 16

Planned Schedule Completing report describing the process

- Published as EPRI Technical Update by July 31

- Free to public to facilitate NRC review and utility application Send to NRC for review Select pilot plants to submit LARs based on this criteria

- One or more LAR pilots in Tier 1 group

- One or more LAR pilots in Tier 2 group Follow-on plant review and approval process 17

Summary Proposed process

- Provides high confidence proper SSCs are being identified as HSS

- Provides greater consistency/stability than alternatives

- Consistent with transformative regulatory direction

- Uses insights from previous seismic evaluations and four 50.69 test cases at high seismic sites to understand the seismic impacts on categorization

- Offers graded criteria, incorporating unique seismic HSS insights

- Includes a new IE PRA sensitivity study for Tier 2 sites to derive key unique seismic insights associated with correlated seismic failures 18

Summary (continued)

Review of the EPRI report and submitted pilots provides NRC an opportunity to evaluate the process in a cost effective manner The proposed criteria would enable consistent implementation by the licensees and streamlined review and approval for follow-on sites 19

TogetherShaping the Future of Electricity 20

Backup Slides 21

NEI 00-04 Categorization Process HSS High Safety Significant Risk (HSS)

Characterization Integrated Decision-Making RISC-1 and HSS

Internal Event Panel (IDP) Review RISC-2 Risks

Fire Risks HSS

Seismic Risks Operating

Other HSS Experience External Risks Defense in Depth Engineering LSS

Shutdown Characterization DBA / Licensing Low Safety LSS Significant Risks Requirements Risk Sensitivity PRA (LHSS)

LSS Study RISC-3 and LSS RISC-4 22

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