1 Fukushima Regulatory Response Workshop Washington, DC April 6, 2012 Seismic Issues Associated with NRC Near Term Task Force Recommendations 2.1 & 2.3 Divakar Bhargava Principal Engineer, Dominion Generation

2 Fukushima NTTF Recommendations 2.3 NRC Request for Information – 10 CFR 50.54(f) Letter dated March 12, 2012 NTTF Recommendation 2.3 –NRC’s Objectives –EPRI Tasks –Outline of Seismic Walkdown Requirements –Near Term Actions Needed by Licensees –Review Next Steps

3 Objectives for Recommendation Walkdowns NRC Objectives Stated in 50.54(f) Letter: –Identify and Address Degraded or Non-Conforming Conditions (i.e., Address Plant Vulnerabilities) –In accordance with: 10 CFR Part 50 App. A, GDC 2 10 CFR Part 100, App. A – Apply lessons learnt, as applicable, from: Ongoing inspections at Fukushima Dai-ichi and Daini North Anna - Mineral VA earthquake of August 23, 2011

4 NTTF Recommendation 2.3 – Walkdowns EPRI Tasks Task 1 - Develop generic seismic walkdown overview guideline and walkdown procedure –Background and purpose (i.e., verify that the current plant configuration is consistent with the licensing basis) –Guidance for selecting equipment to be included in the walkdowns –Requirements for walkdown team composition and qualifications –Documentation requirements –Guidance for Corrective Action Program for equipment not meeting the walkdown acceptance criteria Task 2 - Develop and conduct Seismic Walkdown Engineer (SWE) Training Course(s) –Recommended pre-walkdown actions –Description of the approach for conducting the walkdowns –Acceptance criteria –Checklist documentation requirements

5 Outline of Seismic Walkdown Requirements Personnel Qualifications Scope of Equipment Conduct of Walkdown Resolution of Items Requiring Further Evaluation Documentation/Submittal to NRC

6 Personnel Qualifications System or Design Engineers Seismic Walkdown Engineers –Degree or equivalent in mechanical or civil/structural engineering –Experience in seismic engineering as it applies to nuclear power plants (no required number of years) –Completion of 2-day NTTF 2.3 Seismic Walkdown Training Course or Equivalent

7 Scope of Equipment A sample of mechanical and electrical equipment –At least one item of equipment from each of 21 classes –Include equipment that was added to or modified since the IPEEE Improvements made as part of the licensee’s response to the IPEEE program Equipment that could rapidly drain the spent fuel pool

8 Conduct of Walkdown Evaluate equipment anchorage for degraded, non- conforming, or unanalyzed conditions Screen equipment and its surroundings for seismic interactions –Seismic spatial interactions –Seismically-induced fire interactions –Seismically-induced flooding Verify that IPEEE commitments to modify equipment have been completed Evaluate spent fuel pool equipment for seismic failure modes that could cause rapid draining

9 Resolution of Items Requiring Further Evaluation Identify the licensing basis for the seismic qualification of the equipment Determine whether the equipment installed in the plant meets its seismic qualification licensing basis –If the seismic qualification licensing basis is met, no further action is required –If the seismic qualification licensing basis is not met, enter into the plant corrective action program

10 Documentation/Submittal to NRC Description of seismic walkdown guidelines and procedure used and any exceptions taken Bases for and results of the selection of equipment identified for the walkdown Summary of the results of the walkdown List of equipment that could not be inspected due to inaccessibility Summary of items that required further evaluations and the results of those evaluations. Actions taken or planned to address any deviations from the plant licensing basis. Listing of seismic walkdown engineers, including a copy of their training certificates

11 Near-term Actions from Licensees Walkdowns Resurrect and update the IPEEE SSEL to the current plant configuration. Plant modifications since IPEEE New and replacement equipment Operator review is desirable Collect, review (and update, as needed) IPEEE seismic and structural calculations (SMA HCLPF or SPRA fragility). Collect, review and update IPEEE relay lists and relay seismic test data (This will likely be needed for 2.1) Identify equipment the failure or malfunction of which could cause rapid spent fuel pool drain down

12 NTTF Recommendation Next Steps NRC preliminary feedback from April 3, 2012 Public Meeting –(discuss) Next Steps: –Begin planning for 2.3 walkdowns Review draft guideline Participate in public meetings Collect plant documents and update SSELs Identify walkdown engineers / training –Perform walkdowns and prepare documentation and report for submittal

13 BACK-UP SLIDES ON NTTF 2.1

14 Industry Position on NTTF Recommendation Primary Course of Action Industry Objectives: –Emphasis on analyses that focus on safety significant structures, systems and components of plant –Streamlining of analysis steps and resources Industry positions developed to accomplish the objectives within the timeframe identified in NRC 50.54(f) letter –These positions could eliminate SPRA/SMA effort for some plants and reduce SPRA/SMA effort by 30% to 40% for others, so industry can redirect resources appropriately –Many of the positions (have been/will be) discussed by my colleagues here, others are discussed in this presentation NRC staff’s initial feedback - April 3 Public Meeting

15 NTTF Recomm Proposed Industry Positions “Screening, Prioritization and Implementation Details” Reference Number Position (f) letter A1SE1 Figure 1 Reference 1Use of updated EPRI attenuation model1 2Use of existing site conditions1 3Use of existing structural models6a, 6b 4Scaling of responses to develop ISRS6, 6a 5Screening criteria for SSCs6a, 6b 6Use of IPEEE HCLPF to compare GMRS for screening3, 5 7Treatment of HF3, 6a, 6b 8Use of CDFM and separation on variables methods6a 9Approach for SFP evaluations7a, 7b 10 Overall approach relative to RG and ANS/ASME EE standard ALL 11Consideration of rock founded structures for developing ISRS6a, 6b 12Use of IPEEE hazard to compare to new hazard for screening3, 5

16 NTTF Recommendation 2.1 – Industry Position on Structural Models and Scaling of Responses Position: Existing structural models can be used in seismic structural analysis generated to support SPRAs or SMAs. –Justification: Existing models are reasonably complex; usually have two or three dimensions and multiple frequencies and mode shapes. Conservatism has been demonstrated, e.g., from North Anna August 23, 11 event Position: Scaling of in-structure response spectra (ISRS) based on previous analyses –Justification: Scaling of ISRS is considered a technically sound approach and has been used in previous SPRAs Note: Some follow-up studies may be done to solidify the above positions

17 NTTF Recommendation 2.1 – Industry Position on Screening Criteria for Evaluation of SSCs Position: SSCs with high seismic capacity can be expected to be small contributors to the SCDF and can be excluded from the systems logic model. –SSCs with a mean point estimate probability of failure less than 1E-7 can be considered to constitute a small contributor to SCDF –Screening or ranking of SSCs from a preliminary SPRA plant logic model can be done by performing a parametric sensitivity analyses with assumed initial fragilities and ranges of fragility values Justification: Screening methods have been used in past SPRAs and SMAs. Screening of SSCs helps focus the scope of the fragility/HCLPF calculations

18 NTTF Recommen. 2.1 – Industry Position on Use of CDFM and Separation of Variable Methods Position: Hybrid / CDFM approach is an acceptable method for generating fragilities within a SPRA. Use CDFM approach, as much as possible, to calculate fragilities. The CDFM method will determine a HCLPF value, which can be converted into fragility parameters Justification: CDFM is a simpler method for the majority of engineers to learn and apply, as compared to the fragility method and will provide reasonable estimate of fragility

19 NTTF Recommendation 2.1 – Industry Position on Rock founded structures for developing ISRS Position: The original definition of rock (> 3,500 ft/sec) can be used for the development of the ISRS. Fixed based models can be used in dynamic analyses of rock-founded structures using this original definition of rock Justification: Past experience has shown that the amplified response spectra in the 1-10 Hz are approximately the same from a fixed based model vs. a model that uses soil- structure interaction (SSI) analysis

20 NTTF Recommendation 2.1 – Industry Position on Use of IPEEE hazard to compare to new hazard for screening Position: In the screening process to determine whether a plant needs to perform a SPRA or SMA, the GMRS/SSE comparison is not be the only consideration. Plants can be screened out (i.e., no SMA or SPRA required) if the mean estimate of seismic CDF decreases for the new hazard curve compared to the CDF from hazard curves used during the IPEEE (EPRI-1989 and LLNL-1992) Justification: When the risk to a plant has decreased, further SPRA/SMA is not required. NRC used this type of approach in their safety/risk assessment of GI-199, as documented in Information Notice