NRC Presentation for July 24 25 2012 P bli M ti24-25, 2012 Public Meeting

Recommendation 2.1 Team

Hazard/Screening/Prioritization Topics For Discussion

• NRC Position on Site Response & Control Point Elevation Approaches

• NRC Screening for Risk Evaluation Method

Screening Factors for SPRA– Screening Factors for SPRA– Low Hazard Threshold (LHT)

• NRC Prioritization– Higher Priority: 3 years– Lower Priority: 4 years

• Outline for CEUS Hazard & Screening Submittals

Site Response & Control Point Elevation

• Site Response Status– Working with industry to develop process

to determine site amplification factors for plants

– Agreement on process (awaiting final g p ( greport)

– Process will incorporate both uncertainty and variation in site properties

– Details on expected documentation in plant-specific hazard submittals being worked out

• Control Point Elevation– Reached agreement with industry

Framework for Site Response Analysis: Limited at-Site Data

EarthquakeMagnitude

EarthquakeSource Model

Single-Corner

Vs Profile

Preferred

Upper Range(0.3)

G/GMAX andγ Models

EPRI-Soil*(0.5)

Site Variability

30

Kappa

Upper Range(0.3)

Mean

6.5

Model(0.5)

Double-CornerModel(0.5)

Base Case(0.4)

Lower Range(0.3)

Peninsular*(0.5)

Notes: *EPRI soil and Peninsular curves are to be used at soil sites, EPRI soft-rock and Linear are to be used for soft rock sites. 30 random profiles are generated for

each Base Case Vs model (Preferred, UR, LR). Each path is repeated for 11 acceleration levels.

EPRI-SRock*

(0.5)Linear*

(0.5)

30RandomProfiles

Base Case(0.4)

Lower Range(0.3)

Screening – Low Hazard Threshold

IPEEE Reduced-Scope Plant

GMRS exceeds SSE1.3xSSEbut not LHT

Either SMA or SPRAis appropriate

LHT=0.4g

Screening Criteria for Risk Evaluation

GMRS exceeds:SSELHTIPEEE HCLPF1.3xSSE

SPRA is necessary

NRC Prioritization

• Prioritization will occur after receiving hazard and screening submittals– Fall 2013 for CEUS– Spring 2015 for WUS

F i iti ti t ff ill t k i t• For prioritization staff will take into account amount of hazard exceedance, overall hazard level, and available resources

• Higher priority category (3 yrs) will be reserved for major exceedances and higher hazard levels

TOC/Template for CEUS Hazard & Screening Submittals

• Introduction• Seismic Hazard Results: GMRS

– Regional & Local GeologyProbabilistic Seismic Hazard Analysis– Probabilistic Seismic Hazard Analysis

– Site Response Evaluation– Ground Motion Response Spectrum

• Safe Shutdown Earthquake• Screening Evaluation• Interim Actions• Conclusions

NRC SMA with Enhancements

• NRC SMA is appropriate for sites where the reevaluated hazard is not considerably higher than the design basis hazard or for sites that have a relatively low seismic hazard levelrelatively low seismic hazard level

• Enhanced NRC SMA still considers only two initiators– Small break LOCA– Transients

• Use of screening tables reduces the scope of SSCs to be evaluated

NRC SMA with Enhancements – Reasons for enhancements

The reason for the NRC enhancements are as follows:

• To define the scope of analysis needed for information requested in 50.54(f) letterq ( )

• To provide staff positions on the major elements of SMA

• To update references to allow use of the recent advances in methods and guidance

• To incorporate references to applicable provisions of the ASME/ANS standard and positions of industry (SPID) endorsed by the NRC

NRC SMA with Enhancements (cont.) Key Positions Under Consideration

Initiating events: Transient and small LOCA with unrecoverable loss of offsite power

Mission time: Extended to 72 hrs. or stable shutdown state, whichever is longer

Scope of functions: Group A functions+ emergency core cooling late involving+ emergency core cooling late involving

recirculation and switchover phase + containment heat removal + containment over-pressure protection (early)+ containment integrity

(penetration and isolation) Containment structural failure modes: Need not be includedNon-seismic failures: To be included explicitlyHuman actions: To be included explicitly

NRC SMA with Enhancements (cont.) Key Positions Under Consideration

Screening of SSCs: EPRI NP-6041- SL Rev.1, other recent refs., SPID position

Plant walkdown: EPRI NP-6041- SL Rev.1, ASME/ANS Part 10, HLR-SM-D

Responses: ASME/ANS Part 10, SM-C1 to SM-C4 and SPID

Seismic margin (SSCs)

Fragility method: Section 5-2.2 of Part 5 of the ASME/ANS Part 5, also SPID provision of using CDFM with generic β

CDFM method: Section 10-2 of ASME/ANS Part 10, EPRI-TR

NRC SMA with Enhancements (cont.) Key Positions Under Consideration

High-frequency components : Treated through test programSoil failure modes: To be included as applicableSequence/Plant HCLPF: Convolution approach

Min-Max method acceptable with justification

Documentation: As per ISG-20 and position of SPID on sequences before screening of componentsHCLPFs for leading sequences separately for CDF and LERFHCLPFs for sequences separately with and without non-seismic failures

Peer review: SPID

Use of IPEEE Screening

• Purpose: To provide an avenue for licensees that performed a quality IPEEE to use those risk insights, if applicable, to screen out from additional risk evaluations

• Definition: A quality IPEEE submittal is one that provides confidence that the risk insights areprovides confidence that the risk insights are understood and remain valid and applicable

• What must be demonstrated: Technical elements of the IPEEE are sufficient to support overall results and risk insights from the IPEEE are still valid under current configurations and operations

Use of IPEEE Screening (cont.)

• In addition to NEI proposal, NRC is developing criteria for determining adequate quality

• To demonstrate adequate quality and applicability – licensees will need to submitapplicability – licensees will need to submit sufficient information and justification in their hazard and screening submittals to the NRC

• NRC basis for reviewing adequacy will rely on an overall demonstration of quality as well continued applicability of the IPEEE demonstrated risk insights

IPEEE Screening Adequacy Review NEI Proposal

• Commitments made under IPEEE have been met

• Identified deficiencies to NUREG-1407 in NRC SER are properly justified or correctedp p y j

• Verify major plant modifications since IPEEE have not degraded/impacted IPEEE conclusions

• Focused Scope plants upgrade to Full Scope

• Not applicable to Reduced-Scope plants

IPEEE Screening Considerations

• Staff separated essential elements into four categories1. IPEEE commitments, status, and verification

• Covered by NEI proposal2. Peer Review

• Confirmation of adequate peer review3. Applicability and continued validity of results

• Structural models, ISRS, SSC screening, etc. meet intent of ANS/ASME standard and respective SPID positions

• Confirm the adequacy of LERF evaluations as required by IPEEE

4. Documentation• Documentation should be provided for each of the above

elements in the submittal report to the NRC• An example justification provided in SPID could be jointly

developed by staff and industry to provide guidance on necessary level of documentation

NRC Feedback on Use of Existing Structural Models

The NRC agrees with the five criteria provided in the SPID with the following additions and clarifications:

• Review should be performed by experienced structural and SSI engineers (and a peer reviewer) to assess the applicability of the existing models

• Models should be adequate to capture vertical• Models should be adequate to capture vertical responses - as needed

• Need to add assurance that the model appropriately captures the soil behavior or is appropriately conservative

• Discussion to demonstrate adequacy must be provided in the submittal package to NRC

If necessary the existing structural models can be enhanced to bring them to an acceptable level

NRC Feedback on Use of Scaling

• SPID can provide general guidance, referring to existing documentation

• SPID should provide examples of what is clearly appropriate and clearly not appropriate (NRC requested to see examples at July meeting)requested to see examples at July meeting)

• Scaling where the shape of the new hazard spectrum is substantially different (1 – 10 Hz) than the previous spectrum requires strong justification

• Use of scaling should be reviewed by an experienced structural engineer and should be peer reviewed and discussed in the documentation.

NRC Feedback on High Frequency Equipment List

• The component list in EPRI 1015109 is generally acceptable

• Justification/technical basis should be provided for the additional components not included (such as those in thenot included (such as those in the AP1000 high frequency sensitive equipment list)

• NRC should review the draft testing plan once developed

• NRC will review information related to the test input motions

NRC Feedback on Use of CDFM & FAM

• The use of CDFM with a generic beta to develop the fragility is acceptable. However, the most risk significant components should be reevaluated using the separation of variables method for use in the integrationg

• The full distribution of uncertainty is useful for consideration of different initiators

• The hazard has been rigorously characterized in terms of uncertainties so the risk analysis needs to similarly reflect the uncertainties.

NRC Feedback on Use of Rock Founded Structures For Developing ISRS

• General agreement on the use of fixed base models provided that the study is conducted on a rigid structure (~10Hz) t d t t th ti f thto demonstrate the conservatism of the method.

• The use of a fixed base model should be reviewed by an experienced structural engineer (and peer reviewer) and should be justified in the submittal report to NRC.

NRC Feedback on SPID Document and Path Forward

• NRC Feedback will be ongoing as SPID is developed– SPID positions as agreed upon in previous

meetings should be incorporated into document– Supporting studies needed for closure

• Scaling examples (SPID-4)• Component screening sensitivity study (SPID-5)• High Frequency Phase 1 test plan and program (SPID-

7)• Fixed based analysis for more rigid structure (SPID-11)

– Need industry position and approach on SFP– Further discussion to assess R2.1 approach vs.

SPRA standard– Reach consensus on SPRA HCLPF spectra for

IPEEE screening