ML15070A608

Response to NRC Request for Info. Pursuant to 10 CFR 50.54(f) Seismic Aspects of Recommendation 2.1 of Near-Term Task Force Review of Insights from Fukushima Dai-ichi Accident: Seismic Hazard Screening Report. Part 2 of 2

ML15070A608
Person / Time
Site:	Diablo Canyon
Issue date:	03/11/2015
From:	Pacific Gas & Electric Co
To:	Office of Nuclear Reactor Regulation
References
DCL-15-035
Download: ML15070A608 (53)

Text

Enclosure 1 PG&E Letter DCL-15-035 Page 50 of 60 significant seismic margins (see Appendix B for discussion of the LTSP seismic margins).

A comparison of the GMRS with the LTSP seismic margin spectrum is shown in Figure 5.0-2. This comparison indicates that the GMRS is bounded by the LTSP seismic margin spectrum at all frequencies, including 1.33 Hz and those > 24 Hz- frequencies where the GMRS exceeds the design/licensing basis 1977 HE spectrum .

Therefore, comparing the results of the revised GMRS against the 1988 LTSP evaluation demonstrate that all structures, systems, and components required for safe shutdown, including vibration sensitive components, have a significant seismic design margin beyond the GMRS.

3.0 I

2.5

~ -- r-... ~,

GMRS LTSP Seismic Margin Spectrum 2.0 I I \

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§ 1.5

/; ........

~

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g

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~ 1.0 ..........__

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v 0.0 0.10 1.0 0 10.00 100.00 Frequency (Hz)

Figure 5.0-2: Comparison of GMRS and LTSP Seismic Margin Spectrum for DCPP (5%) Damping)

Based on the above comparisons to the design/licensing basis 1977 HE evaluation and the 1988 LTSP evaluation, there is reasonable assurance that DCPP remains safe to operate without undue risk to the public while an updated risk evaluation is being performed.

Enclosure 1 PG&E Letter DCL-15-035 Page 51 of 60 The consideration of potential loss of the water inventory from the SFPs, as described in Section 7 of the SPID (EPRI 2013a), has been addressed as part of the NTTF Recommendation 2.3: Seismic Walkdowns, as discussed in Section 5.2. The results of these walkdowns demonstrated that the potential for loss of the water inventory from the SFPs (e.g., rapid draindown) has been adequately addressed in the design and construction of DCPP's SFPs. Further evaluations of the potential loss of the water inventory from the SFPs will be performed once an NRC-endorsed guidance has been developed.

5.1 Expedited Seismic Evaluation Process The ESEP, as proposed in the NEI's letter to the NRC, dated April 9, 2013 (NEI 2013) and confirmed in NRC letter dated May 7, 2013 (NRC 2013), is described in EPRI Technical Report No. 3002000704 (EPRI 2013b).

The ESEP was intended as an interim measure to provide additional assurance of safety in cases where the GMRS significantly exceeds the plant design/licensing basis while additional risk evaluations (i.e., SMA, or SPRA) were being performed. However, as discussed in Section 5.0, the DCPP GMRS is bounded by other previous seismic evaluations, including the design/licensing basis 1977 HE evaluations and the 1988 LTSP evaluation. Therefore, there are no additional benefits in performing this activity in parallel with the more robust risk evaluation associated with updating/upgrading the SPRA. PG&E will devote the critical skilled resources to expediting the update/upgrade of the SPRA in order to gain additional risk insights in a timely manner.

5.2 Walkdowns to Address NRC Fukushima NTTF Recommendation 2.3: Seismic In response to the NRC's March 12, 2012 50.54(f) letter Fukushima NTTF Recommendation 2.3: Seismic (NRC 2012), PG&E performed walkdowns of the configuration of specific equipment and components in accordance with EPRI Technical Report No. 1025286 (EPRI 2012), as endorsed by the NRC in their letter dated May 31, 2012 (NRC 2012a). The goals of these walkdowns were to (a) verify that the current plant configuration was in accordance with the licensing basis; (b) verify that the current maintenance plans were adequate to maintain the plant configuration in accordance with the licensing basis; and (c) identify any seismic vulnerabilities. The potential for loss of water inventory from the SFPs (e.g., rapid draindown) was included in the scope of these walkdowns.

The walkdowns of DCPP, Units 1 and 2, as documented in several PG&E letters to the NRC (PG&E 2012, PG&E 2012a, PG&E 2013b, and PG&E 2014a) identified a number of potentially adverse seismic conditions, which were entered into the DCPP corrective action program. The engineering evaluations of the potentially adverse seismic conditions determined that they did not adversely affect the performance of any required safety functions, including the ability to maintain the water inventory of the SFPs during a seismic event. Therefore,

Enclosure 1 PG&E Letter DCL-15-035 Page 52 of 60 these walkdowns confirmed that the configuration of DCPP is within its seismic design/licensing basis and provided additional assurance of seismic safety.

The NRC has reviewed the DCPP NTTF Recommendation 2.3: Seismic walkdown submittal reports and the results of their staff assessment (NRC 2014a) concluded that sufficient information was provided by PG&E to be responsive to the requirements of their March 12, 2012 10 CFR 50.54(f) letter (NRC 2012).

Enclosure 1 PG&E Letter DCL-15-035 Page 53 of 60 6.0 Conclusions PG&E completed a seismic hazard and screening evaluation for DCPP in accordance with the NRC's Fukushima 10 CFR 50.54(f) request for information letter (NRC 2012), and consistent with the NRC endorsed SPID guidelines (EPRI 2013a). A GMRS was developed solely for the purpose of screening for additional evaluations in accordance with the SPID. The DCPP GMRS exceeds the design and licensing basis DOE spectrum in both the 1 to 10 Hz range and above 10 Hz. Therefore, an updated risk evaluation and a SFP evaluation for potential loss of water inventory, in accordance with the SPID (EPRI 2013a) will be performed.

PG&E also compared the GMRS with the LTSP seismic margin spectrum, described in Section 5.0. The comparison shows that DCPP's structures, systems and components required for safe shutdown and the SFPs have significant design margins beyond the GMRS. In addition, the results of the Fukushima NTTF Recommendation 2.3: Seismic walkdowns, described in Section 5.2, show that the potential for loss of water inventory from the SFPs has been adequately addressed. Therefore, DCPP remains safe to operate without undue risk to the public while an updated risk evaluation and detailed SFP evaluation for potential loss of water inventory are being performed.

PG&E will perform an update to the SPRA in accordance with the EPRI guidance (EPRI 2013a) in support of the resolution of Fukushima NTTF Recommendation 2.1: Seismic. PG&E believes that since there are no additional insights to be gained from an implementation of an ESEP, PG&E will devote its resources to performing a more robust SPRA. PG&E will perform additional evaluations of the SFPs to address potential loss of water inventory in accordance with the EPRI guidance (EPRI 2013a) and any additional NRC endorsed guidance that may be issued. The completion dates for the SPRA and SFP evaluations will be based on the schedule as defined in NEI's letter to the NRC, dated April 9, 2013 (NEI 2013) and confirmed in NRC's letter, dated May 7, 2013 (NRC 2013).

Enclosure 1 PG&E Letter DCL-15-035 Page 54 of 60 7.0 References 7.1 Electric Power Research Institute (a) EPRI 2012, "Seismic Walkdown Guidance for the Resolution of Fukushima Near-Term Task Force Recommendation 2.3: Seismic,"-

Technical Report No. 1025286, dated June 2012 (b) EPRI 2013a, "Seismic Evaluation Guidance- Screening, Prioritization and Implementation Details (SPID) for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic," Technical Report No. 1025287, dated February 2013 (c) EPRI 2013b, "Seismic Evaluation Guidance: Augmented Approach for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1:

Seismic," Technical Report No. 3002000704, dated April 2013 (d) EPRI 2013c, "EPRI (2004, 2006) Ground-Motion Model (GMM) Review Project," Technical Report No. 3002000717, 2 Volumes, dated June 2013 7.2 Pacific Gas and Electric Company (a) PG&E 1980, PG&E Report, "Seismic Evaluation for Postulated 7.5M Hosgri Earthquake- Units 1 and 2, Diablo Canyon Site," transmitted to the NRC as Amendment Nos. 50, 53, 54, 56, 59, 60, 62, 64, 66, 68, 70, 72, 75, 76, 77, 79, 82, and 83 to the Operating License Application for Diablo Canyon Power Plants Units 1 and 2," dated June 3, 1977 through June 6, 1980 (b) PG&E 1988, PG&E Report, "Final Report of the Diablo Canyon Long Term Seismic Program for the Diablo Canyon Power Plant," Enclosure to PG&E Letter DCL-88-192, "Long Term Seismic Program Completion," dated July 31, 1988 (c) PG&E 1990, PG&E Report, "Additional Deterministic Evaluations Performed to Assess Seismic Margins of the Diablo Canyon Power Plant, Units 1 and 2," Enclosure to PG&E Letter DCL-90-226, "Long Term Seismic Program Additional Deterministic Evaluations," dated September 18, 1990 (d) PG&E 1991, PG&E Report, "Addendum to the 1988 Final Report of the Diablo Canyon Long Term Seismic Program," Enclosure to PG&E Letter DCL-91-027, "Addendum to Long Term Seismic Program Final Report,"

dated February 13, 1991

Enclosure 1 PG&E Letter DCL-15-035 Page 55 of 60 (e) PG&E 2011, PG&E Report, "Report on the Analysis of the Shoreline Fault Zone, Central Coastal California, report to the U.S. Nuclear Regulatory Commission," Enclosure to PG&E Letter DCL-11-005, "Report on the Analysis of the Shoreline Fault Zone, Central Coastal California," dated January 7, 2011 (f) PG&E 2012, PG&E Letter DCL-12-118, "Response to Request for Information Pursuant to 10 CFR 50 .54(f) Regarding Recommendation 2.3 Seismic Unit 1,"dated November 27, 2012 (g) PG&E 2012a, PG&E Letter DCL-12-119, "Response to Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 2.3 Seismic Unit 2," dated November 27, 2012 (h) PG&E 2013, "Diablo Canyon Power Plant Units 1 & 2 Final Safety Analysis Report Update," Revision 21, dated September 2013 (i) PG&E 2013b, PG&E Letter DCL-13-054, "Response Amendment to Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 2.3 Seismic," DCPP Unit 2, dated May 22, 2013

0) PG&E 2013d, PG&E Letter DCL-13-044, "Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding the Seismic Aspects of Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident," dated April 29, 2013 (k) PG&E, 2014, PG&E Report, "Central Coastal California Seismic Imaging Project Report to the California Public Utilities Commission," Enclosure to PG&E Letter DCL-14-081, "Central Coastal California Seismic Imaging Project, Shoreline Fault Commitment," dated September 10, 2014 (I) PG&E 2014a, PG&E Letter DCL-14-041, "Response Update to Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 2.3 Seismic Unit 1,"dated May 8, 2014 (m) PG&E 2015, "Seismic Source Characterization for Probabilistic Seismic Hazard Analysis for the Diablo Canyon Power Plant, San Luis Obispo County, California," Report on the Results of the SSHAC Level 3 Study in Partial Compliance with NRC Letter 50.54(f), dated March 2015.

7.3 United States Nuclear Regulatory Commission (a) NRC 1973, "Seismic and Geologic Siting Criteria for Nuclear Power Plants," Appendix A to Part 100, "Reactor Site Criteria," of Title 10, "Energy," of the Code of Federal Regulations, dated December 13, 1973

Enclosure 1 PG&E Letter DCL-15-035 Page 56 of 60 (b) NRC 1976, "Supplement No.5 to the Safety Evaluation Report by the Office of Nuclear Reactor Regulation, U.D. Nuclear Regulatory Commission, in the Matter of Pacific Gas and Electric Company, Diablo Canyon Nuclear Power Station, Units 1 and 2, Docket Nos. 50-275 and 50-323," NUREG-0675, Supplement No. 5, dated September 10, 1976 (c) NRC 1978a, "Seismic Design Classification," Regulatory Guide 1.29, Revision 3, dated September 1978 (d) NRC 1978b, "Supplement No. 7 to the Safety Evaluation Report by the Office of Nuclear Reactor Regulation, U.D. Nuclear Regulatory Commission, in the Matter of Pacific Gas and Electric Company, Diablo Canyon Nuclear Power Station, Units 1 and 2, Docket Nos. 50-275 and 50-323," NUREG-0675, Supplement No. 7, dated May 26, 1978 (e) NRC 1991, "Safety Evaluation Report related to the operation of Diablo Canyon Nuclear Power Plant, Units 1 and 2, Docket Nos. 50-275 and 50-323, Pacific Gas and Electric Company," NUREG-0675, Supplement No. 34, dated June 1991 (f) NRC 1997, "Recommendations for Probabilistic Seismic Hazard Analysis:

Guidance on Uncertainty and Use of Experts- Main Report,"

NUREG/CR-6372, Volume 1, dated April 1997 (g) NRC 2001, "Technical Basis for Revision of Regulatory Guidance on Design Ground Motions: Hazard- and Risk- Consistent Ground Motion Spectra Guidelines," NUREG/CR-6728, dated November 6, 2001 (h) NRC 2007, "A Performance-Based Approach to Define the Site-Specific Earthquake Ground Motion," Regulatory Guide 1.208, dated March 2007 (i) NRC 2012, letter from Eric J. Leeds (NRC) to All Power Reactor Licensees and Holders of Construction Permits in Active or Deferred Status, "Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-lchi Accident," dated March 12, 2012 (ADAMS Accession No. ML12056A046)

U) NRC 2012a, letter from David L. Skeen (NRC) to Adrian P. Heymer (NEI),

"Endorsement of Electric Power Research Institute (EPRI) Draft Report 1025286, 'Seismic Walkdown Guidance'," dated May 31, 2012

Enclosure 1 PG&E Letter DCL-15-035 Page 57 of 60 (k) NRC 2012b, "Practical Implementation Guidelines for SSHAC Level 3 and 4 Hazard Studies," NUREG-2117, Revision 1, dated April2012 (I) NRC 2012c, letter from Joseph M. Sebrosky (NRC) to Edward P. Halpin (PG&E), "Diablo Canyon Power Plant, Unit Nos. 1 and 2- NRC Review of Shoreline Fault (TAC Nos. ME5306 and ME5307)," dated October 12, 2012 (m) NRC 2013, letter from Eric J. Leeds (NRC) to Joseph E. Pollack (NEI),

"Electric Power Research Institutes Final Draft Report XXXXX, 'Seismic Evaluation Guidance: Augmented Approach for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic,' As an Acceptable Alternative to the March 12, 2012, Information Request for Seismic Reevaluations," dated May 7, 2013 (ADAMS Accession No. ML13106A331) 11 (n) NRC 2014, letter from Eric J. Leeds (NRC) to All Power Reactor Licensees and Holders of Construction Permits in Active or Deferred Status on the Enclosed List, "Supplemental Information Related to Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Seismic Hazards Reevaluations for Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-lchi Accident," dated February 20, 2014 (ADAMS Accession No. ML14030A046)

(o) . NRC 2014a, letter from James Kim (NRC) to Edward D. Halpin (PG&E),

"Diablo Canyon Power Plant, Units 1 and 2 - Staff Assessment of the Seismic Walkdown Reports Supporting Implementation of Near-Term Task Force Recommendation 2.3 Related to the Fukushima Dai-lchi Nuclear Power Plant Accident (TAC Nos. MF0117 and MF0118)," dated March 14, 2014.

(p) NRC 2014c, memorandum from Nicholas J. DiFrancesco (Senior Project Manager, Japan Lessons-Learned Division) to Sheena A. Whaley (Chief, Japan Lessons-Learned Division), "Summary of October 27, 2014, Category 2 Public Meeting with the Nuclear Energy Institute to Discuss Seismic Hazard Reevaluations Associated with Implementation of Japan Lessons-Learned Near-Term Task Force Recommendation 2.1, Seismic,"

dated December 15, 2014 (ADAMS Accession No. ML143078726) 11 EPRI Draft Report XXXXX referenced in the title of this letter corresponds to EPRI Technical Report No. 3002000704 (EPRI 2013b).

Enclosure 1 PG&E Letter DCL-15-035 Page 58 of 60 (q) NRC 2014d, memorandum from Nicholas J. DiFrancesco (Senior Project Manager, Japan Lessons-Learned Division) to Sheena A. Whaley (Chief, Japan Lessons-Learned Division), "Summary of December 4, 2014, Category 2 Public Meeting with the Nuclear Energy Institute to Discuss Seismic Hazard Reevaluations for the Western United States Sites Associated with Implementation of Japan Lessons-Learned Near-Term Task Force Recommendation 2.1, Seismic," dated December 15, 2014 (ADAMS Accession No. ML14342A901) 7.4 Nuclear Energy Institute (a) NEI 2013, letter from Anthony R. Pietrangelo (NEI) to David L. Skeen (NRC), "Proposed Path Forward for NTTF Recommendation 2.1 Seismic Reevaluations," dated April 9, 2013 (ADAMS Accession No. ML13101A379) 7.5 Other (a) AI-Atik, L., Abrahamson, N., Bommer, J., Scherbaum, F., Cotton, F.,

Kuehn, N. 2010, "The Variability of Ground-Motion Prediction Models and Its Components," Seismological Research Letters, Volume 81, Issue 5, pp. 794-801.

(b) DeMets, C., Marquez-Azua, B., and Cabrai-Cano, E. 2014, "A new GPS velocity field for the Pacific Plate- Part 1: constraints on plate motion, intraplate deformation, and the viscosity of Pacific basin asthenosphere" Geophysical Journal International, Volume 199: 1878-1899.

(c) GeoPentech 2015, "Southwestern United States Ground Motion Characterization SSHAC Level 3," Technical Report, Revision 1, dated February 2015 (d) Hanson, K.L., and Lettis, W.R. 1994, "Estimated Pleistocene slip rate for the San Simeon fault zone, south-central coastal California: in Alterman, I.B., McMullen, R.B., Cluff, L.S., and Slemmons, D.B. (editors),

• Seismotectonics of the Central California Coast Range, Geological Society of America Special Paper 292, pp. 133-150 (e) Hardebeck, J.L. 2010, "Seismotectonics and fault structure of the California central coast," Bulletin of the Seismological Society of America, Volume 100, Issue 3: pp 1031-1050.

(f) Hardebeck, J.L. 2013, "Geometry and earthquake potential of the Shoreline Fault, Central California," Bulletin of the Seismological Society of America Volume 103, Issue 1: pp 447-462

Enclosure 1 PG&E Letter DCL-15-035 Page 59 of 60 (g) Johnson, S.Y., Hartwell, S.R., and Dartnell, P. 2014, "Offset of Latest Pleistocene shoreface reveal slip rate on the Hosgri strike-slip fault, offshore central California," Bulletin of the Seismological Society of America, Volume 104, Issue 4, doi: 10.1785/012013057.

(h) Kamai, R., Abrahamson, N., Silva, W. 2014, "Nonlinear Horizontal Site Amplification for Constraining the NGA-West2 GMPEs," Earthquake Spectra, Volume 30, Issue 3, pp. 1223-1240 (i) Ktenidou, 0. and N. Abrahamson, 2015 "A methodology for the selection of data and the estimation of kappa (K) for hard rock sites in the NGA databases," Pacific Earthquake Engineering Research Center, PEER Report 2015/03.

U) Lin, P., N. Abrahamson, M. Walling, C.-T. Lee, B. Chiou, and C. C., Heng, 2011, "Repeatable path effects on the standard deviation for empirical ground-motion models," Bulletin of the Seismological Society of America, Volume 101, pp. 2281-2295.

(k) Lettis, W.R., and Hall, N.T. 1994, "Los Osos fault zone, San Luis Obispo County, California: in Alterman, I.B., McMullen, R.B., Cluff, L.S., and Slemmons, D.B. (editors), Seismotectonics of the Central California Coast Ranges," Geological Society of America Special Paper 292, pp.73-102, and Plate 5.

(I) Lettis, W.R., Kelson, K.l., Wesling, J.R., Angell, M., Hanson, K.L., and Hall, N.T. 1994, "Quaternary deformation of the San Luis Range, San Luis Obispo County, California," in Alterman, I. B., McMullen, R.B., Cluff, L.S.,

and Slemmons, D.B. (editors), Seismotectonics of the Central California Coast Ranges, Geological Society of America Special Paper 292, pp. 111-132.

(m) Lettis, W.R., Hanson, K.L., Unruh, J.R., Mclaren, M.K., Savage, W.U.

2004, "Quaternary Tectonic Setting of South-Central Coastal California,"

U.S. Geological Survey Bulletin, 1995 (AA): pp. 1-21.

(n) Mclaren, M.K., and Savage, W.U. 2001, "Seismicity of South-Central Coastal California: October 1987 through January 1997," Bulletin of the Seismological Society of America, Volume 91, Issue 4: 1629-1658.

Enclosure 1 PG&E Letter DCL-15-035 Page 60 of 60 (o) Willingham, C.R., Rietman, J.D., Heck, R.G., and Lettis, W.R. 2013, "Characterization of the Hosgri Fault Zone and adjacent structures in the offshore Santa Maria Basin, south-central California: in Keller, M.A .

. (editor), Evolution of Sedimentary Basins/Onshore Oil and Gas Investigations-Santa Maria Province," U.S. Geological Survey Bulletin 1995-CC, pp. 105 (revised version of 1995 report).

Enclosure 1 PG&E Letter DCL-15-035 Appendix A Page 1 of 13 Appendix A- Additional Seismic Hazard Curve Data

Enclosure 1 PG&E Letter DCL-15-035 Appendix A Page 2 of 13 A 1. 0 Hazard for the Reference Rock Site The mean hazard by source for the reference rock site are listed in Table A1.0-1 for 10Hz spectral acceleration and in Table A1.0-2 for 1 Hz spectral acceleration. The deaggregation of the mean hazard at the 1 x 1o-4 hazard level for 10 and 1 Hz are shown in Figures A 1.0-1 and A 1.0-2, respectively. The degregation shows that the hazard at DCPP at the 1 x 1o-4 hazard level is controlled by nearby earthquakes (< 10 km) with moment magnitudes (M) in the M6 to M8 range.

A2.0 Hazard for the Control Point The mean hazard for the control point and the fractiles of the hazard, that capture the epistemic uncertainty, are listed in Tables A2.0-1 through A2.0-7 for the peak acceleration and six spectral frequencies: 20, 10, 5, 2.5, 1, and 0.5 Hz.

A3.0 Site Amplification for the Control Point The median amplification (from the reference rock site to the control point) is listed in Table A3.0-1. The epistemic uncertainty in the median amplification is quantified by the logarithmic standard deviation listed in Table A3.0-1. The non-linear effects are captured addressed by the empirical ground motion models used for the reference rock site (Vs 30 = 760 m/s and kappa = 0.041 seconds). The aleatory variability of the site response is captured by the standard deviation of the empirical ground motions. The single-station sigma approach removes the differences in the site-specific site amplification from the traditional ergodic standard deviation, but the single-station sigma approach does not remove the aleatory variability in the site amplification from the empirically-based standard deviations.

Enclosure 1 PG&E Letter DCL-15-035 Appendix A Page 3 of 13 Table A 1.0-1: Mean Hazard by Source for the Reference Rock Site for 10Hz Spectral Acceleration .

10Hz Los Local San Other Other PSA Total Hosgri Shoreline Osos San Luis source Andreas connected regional (g) Hazard fault fault fault Bay fault zone fault faults faults 0.01 3.9E-01 2.1 E-02 3.9E-04 8.3E-04 7.1 E-04 4.4E-03 9.0E-02 2.1 E-03 4.8E-02 0.05 7.5E-02 1.0E-02 2.7E-04 8.0E-04 5.8E-04 4.1 E-03 1.9E-02 1.3E-03 9.3E-03 0.1 3.1 E-02 6.5E-03 2.2E-04 7.3E-04 5.2E-04 3.4E-03 5.9E-03 8.5E-04 3.6E-03 0.2 1.2E-02 3.7E-03 1.7E-04 6.2E-04 4.5E-04 2.1 E-03 1.4E-03 4.6E-04 1.1 E-03 0.4 4.6E-03 1.8E-03 1.1 E-04 4.4E-04 3.4E-04 9.4E-04 1.5E-04 1.8E-04 2.2E-04 0.8 1.5E-03 6.5E-04 5.9E-05 2.1 E-04 1.9E-04 2.8E-04 1.0E-05 3.9E-05 2.1 E-05 1.5 3.7E-04 1.6E-04 1.8E-05 5.6E-05 6.5E-05 6.0E-05 5.5E-07 5.2E-06 1.5E-06 2.0 1.6E-04 6.7E-05 8.2E-06 2.5E-05 3.1 E-05 2.5E-05 1.3E-07 1.7E-06 4.1E-07 3.0 4.1 E-05 1.6E-05 2.2E-06 6.6E-06 9.0E-06 6.2E-06 1.3E-08 3.3E-07 5.6E-08 5.0 5.7E-06 2.1E-06 3.1 E-07 9.6E-07 1.4E-06 8.5E-07 5.9E-10 3.2E-08 3.5E-09 10.0 2.7E-07 8.9E-08 1.5E-08 4.8E-08 7.4E-08 4.0E-08 3.1 E-12 9.2E-10 4.8E-11 Table A 1.0-2: Mean Hazard by Source for the Reference Rock Site for 1 Hz Spectral Acceleration.

1Hz Los Local San Other Other PSA Total Hosgri Shoreline Osos San Luis source Andreas connected regiona (g) Hazard fault

• fault fault Bay fault zone fault faults I faults 0.01 1.8E-01 7.8E-03 2.7E-04 7.6E-04 5.6E-04 3.7E-03 4.8E-02 1.1 E-03 3.4E-02 0.05 1.6E-02 2.5E-03 1.4E-04 5.3E-04 3.8E-04 1.2E-03 4.2E-03 4.6E-04 2.4E-03 0.1 5.0E-03 1.3E-03 9.6E-05 3.9E-04 2.9E-04 5.2E-04 9.8E-04 2.1 E-04 5.0E-04 0.2 1.6E-03 6.8E-04 5.7E-05 1.9E-04 1.6E-04 1.8E-04 1.3E-04 5.4E-05 5.9E-05 0.4 4.5E-04 2.6E-04 2.1E-05 4.6E-05 5.2E-05 4.5E-05 9.7E-06 7.1 E-06 4 .2E-06 0.8 8.0E-05 5.4E-05 3.9E-06 5.3E-06 9.2E-06 6.5E-06 4.7E-07

• 5.5E-07 1.8E-07 1.5 1.0E-05 7.4E-06 5.2E-07 4.8E-07 1.2E-06 7.2E-07 1.9E-08 3.7E-08 7.2E-09 2.0 3.6E-06 ' 2.6E-06 1.8E-07 1.4E-07 4.0E-07 2.3E-07 3.9E-09 9.4E-09 1.4E-09 3.0 6.9E-07 5.2E-07 3.6E-08 2.2E-08 7.7E-08 4.2E-08 3.5E-10 1.2E-09 1.2E-10 5.0 7.2E-08 5.4E-08 3.9E-09 1.7E-09 7.9E-09 4.0E-09 1.1E-11 7.2E-11 3.5E-12

Enclosure 1 PG&E Letter DCL-15-035 Appendix A Page 4 of 13 DCPP: 10 Hz, AEP=l0-4 "a

~ 0.18 N

~ 0.16

....0 0.14 c

0

• .;= 0.12

..Q 0.1

• c c 0.08 0

u 0.06 Q,l bO

....c nl 0.04 Q,l 0.02 Col Q,l 0

c.

Distance (km)

Figure A 1.0-1: Deaggregation of the Reference Rock Site Hazard for 10Hz Spectral Acceleration for the 1E-4 Hazard Level.

Enclosure 1 PG&E Letter DCL-15-035 Appendix A Page 5 of 13 DCPP: 1 Hz, AEP=l0-4

"'C

0.25 N

fa

r:

s 0.2 c

0

• .g

..Q 0.15

• c c

8 0.1 ell fell 0.05 Col

~ 0 Distance (km)

Figure A 1.0-2: Deaggregation of the Reference Rock Site Hazard for 1 Hz Spectral Acceleration for the 1E-4 Hazard Level.

Enclosure 1 PG&E Letter DCL-15-035 Appendix A Page 6 of 13 Table A2.0-1: Mean and Fractiles of Hazard for the Control Point for Peak Acceleration PGA (g) Mean 5th

• 16m som 84tn 95m 0.02 7.0E-02 4:4E-02 4.9E-02 7.5E-02 1.2E-01 1.2E-01 0.05 2.3E-02 1.1 E-02 1.4E-02 2.3E-02 3.5E-02 3.8E-02 0.10 8.4E-03 3.5E-03 4.6E-03 8.4E-03 1.4E-02 1.5E-02 0.15 4.6E-03 1.6E-03 2.2E-03 4.3E-03 7.2E-03 8.5E-03 0.20 2.8E-03 9.1 E-04 1.4E-03 2.7E-03 4.7E-03 5.7E-03 0.25 2.0E-03 5.2E-04 8.3E-04 1.7E-03 3.3E-03 4.2E-03 0.30 1.4E-03 2.8E-04 4.9E-04 1.2E-03 2.4E-03 3.0E-03 0.40 7.3E-04 1.2E-04 2.4E-04 6.5E-04 1.5E-03 2.0E-03 0.50 4.3E-04 5.5E-05 1.2E-04 3.4E-04 8.8E-04 1.3E-03 0.60 2.8E-04 2.4E-05 5.8E-05 2.1 E-04 5.5E-04 7.9E-04 0.70 1.7E-04 1.0E-05 2.7E-05 1.1 E-04 3.8E-04 5.8E-04 0.85 8.6E-05 4.1 E-06 1.2E-05 5.7E-05 2.2E-04 3.5E-04 1.00 4.9E-05 1.8E-06 6.4E-06 3.1 E-05 1.2E-04 1.9E-04 1.20 2.6E-05 5.1 E-07 2.1 E-06 1.5E-05 7.1 E-05 1.3E-04 1.40 1.4E-05 2.3E-07 1.0E-06 7.6E-06 3.7E-05 7.1 E-05

• 1.60 8.2E-06 7.8E-08 4.0E-07 4.0E-06 2.3E-05 4.7E-05 1.80 4.9E-06 3.5E-08 2.0E-07 2.2E-06* 1.4E-05 3.1 E-05 2.0 3.2E-06 1.6E-08 9.5E-08 1.3E-06 8.9E-06 2.1 E-05 2.5 1.2E-06 2.1 E-09 1.6E-08 3.5E-07 3.3E-06 8.4E-06 3.0 5.0E-07 5.2E-10 3.4E-09 9.6E-08 1.3E-06 3.5E-06 4.0 1.3E-07 7.0E-11 4.3E-10 1.2E-08 2.3E-07 8.4E-07 5.0 3.8E-08 1.6E-11 1.1E-10 2.9E-09 7.2E-08 3.0E-07

Enclosure 1 PG&E Letter DCL-15-035 Appendix A Page 7 of 13 Table A2.0-2: Mean and Fractiles of Hazard for the Control Point for 20 Hz Spectral Acceleration 20Hz Mean 5th 16th 50th 84th 95th PSA (g) 0.02 7.5E-02 4.4E-02 4.8E-02 7.1 E-02 1.5E-01 1.6E-01 0.05 2.6E-02 1.3E-02 1.6E-02 2.6E-02 5.1 E-02 5.5E-02 0.10 1.0E-02 4.4E-03 5.7E-03 1.0E-02 2.1 E-02 2.4E-02 0.15 5.5E-03 2.1 E-03 2.9E-03 5.5E-03 1.2E-02 1.4E-02 0.20 3.6E-03 1.2E-03 1.7E-03 3.6E-03 7.9E-03 9.4E-03 0.25 2.5E-03 7.1 E-04 1.1 E-03 2.4E-03 5.8E-03 7.0E-03 0.30 1.8E-03 4.3E-04 7.2E-04 1.8E-03 4.2E-03 5.2E-03 0.40 1.0E-03 2.0E-04 3.6E-04 1.0E-03 2.7E-03

• 3.5E-03 0.50 6.6E-04 7.7E-05 1.6E-04 5.7E-04 1.8E-03 2.5E-03 0.60 4.0E-04 3.8E-05 8.7E-05 3.4E-04 1.2E-03 1.8E-03 0.70 2.7E-04 2.0E-05 5.0E-05 2.3E-04 9.3E-04 1.4E-03 0.85 1.6E-04 7.9E-06 2.3E-05 1.3E-04 5.9E-04 9.6E-04 1.00 9.4E-05 3.2E-06 1.1 E-05 6.7E-05 3.4E-04 6.0E-04 1.20 5.1 E-05 1.3E-06 4.9E-06 3.7E-05 2.4E-04 4.4E-04 1.40 2.9E-05 4.1 E-07 1.9E-06 1.8E-05 . 1.4E-04 2.7E-04 1.60 1.7E-05 2.1 E-07 1.0E-06 1.1 E-05 9.1 E-05 1.9E-04 1.80 1.1 E-05 7.4E-08 4.5E-07 6.1 E-06 6.0E-05 1.3E-04 2.0 7.2E-06 3.8E-08 2.4E-07 3.8E-06 3.9E-05 9.1 E-05 2.5 2.8E-06 9.5E-09 6.2E-08 1.3E-06 1.6E-05 4.3E-05 3.0 1.3E-06 2.0E-09 1.5E-08 4.8E-07 7.0E-06 2.0E-05 4.0 3.3E-07 2.5E-10 2.1 E-09 8.5E-08 1.6E-06 5.7E-06 5.0 1.2E-07 5.9E-11 4.3E-10 2.2E-08 5.5E-07 2.4E-06

Enclosure 1 PG&E Letter DCL-15-035 Appendix A Page 8 of 13 Table A2.0-3: Mean and Fractiles of Hazard for the Control Point for 10 Hz Spectral Acceleration 10Hz Mean 5m 16th 50th 84th 95th PSA (g) 0.02 1.1 E-01 6.9E-02 7.5E-02 1.1 E-01 2.1 E-01 2.2E-01 0.05 4.0E-02 2.0E-02 2.3E-02 4.1 E-02 7.8E-02 8.4E-02 0.10 1.6E-02 6.9E-03 8.8E-03 1.7E-02 3.3E-02 3.6E-02 0.15 9.3E-03 3.5E-03 4.7E-03 9.2E-03 1.9E-02 2.1 E-02 0.20 6.2E-03 2.1 E-03 2.9E-03 6.1 E-03 1.3E-02 1.5E-02 0.25 4.5E-03 1.4E-03 2.0E-03 4.1 E-03 9.7E-03 1.1 E-02 0.30 3.3E-03 9.3E-04 1.4E-03 3.2E-03 7.1 E-03 8.6E-03 0.40 2.1 E-03 4.7E-04 7.9E-04 2.0E-03 4.8E-03 5.9E-03 0.50 1.4E-03 2.3E-04 4.2E-04 1.2E-03 3.4E-03 4.3E-03 0.60 9.5E-04 1.6E-04 3.0E-04 8.5E-04 2.4E-03 3.2E-03 0.70 6.7E-04 8.4E-05 1.8E-04 6.0E-04 1.9E-03 2.6E-03 0.85 4.4E-04 3.6E-05 8.5E-05 3.7E-04 1.3E-03 1.9E-03 1.00 2.9E-04 1.7E-05 4.4E-05 2.2E-04 8.8E-04 1.3E-03 1.20 1.7E-04 8.3E-06 2.3E-05 1.3E-04 6.6E-04 9.7E-04 1.40 1.0E-04 3.8E-06 1.2E-05 7.4E-05 4.3E-04 6.5E-04 1.60 6.5E-05 1.6E-06 5.6E-06 4.6E-05 3.1 E-04 4.9E-04 1.80 4.4E-05 8.5E-07 3.4E-06 3.1 E-05 2.2E-04 3.7E-04 2.0 2.9E-05 4.7E-07 2.0E-06 2.0E-05 1.5E-04 2.7E-04 2.5 1.2E-05 7.9E-08 4.6E-07 6.9E-06 7.2E-05 1.4E-04 3.0 6.1 E-06 2.9E-08 2.0E-07 3.5E-06 3.4E-05 7.6E-05 4.0 1.7E-06 4.0E-09 3.4E-08 7.2E-07 9.4E-06 2.4E-05 5.0 6.4E-07 5.6E-10 5.3E-09 2.0E-07 3.9E-06 1.1 E-05

Enclosure 1 PG&E Letter DCL-15-035 Appendix A Page 9 of 13 Table A2.0-4: Mean and Fractiles of Hazard for the Control Point for 5 Hz Spectral Acceleration 5Hz Mean 5m 16m 5om 84tn 95m PSA (g) 0.02 1.4E-01 9.6E-02 1.0E-01 1.4E-01 2.4E-01 2.5E-01

• 0.05 5.4E-02 2.8E-02 3.1 E-02 5.6E-02 9.0E-02 9.4E-02 0.10 2.1 E-02 9.5E-03 1.2E-02 2.2E-02 3.6E-02 3.9E-02 0.15 1.2E-02 4.8E-03 6.1 E-03 1.2E-02 2.0E-02 2.3E-02 0.20 7.9E-03 3.0E-03 4.0E-03 7.9E-03 1.4E-02 1.6E-02 0.25 5.7E-03 2.0E-03 2.8E-03 5.3E-03 1.0E-02 1.2E-02 0.30 4.4E-03 1.4E-03 2.0E-03 4.2E-03 7.5E-03 9.0E-03 0.40 2.8E-03 7.8E-04 1.2E-03 2.7E-03 5.0E-03 6.1E-03 0.50 2.0E-03 4.8E-04 7.8E-04 1.7E-03 3.6E-03 4.5E-03 0.60 1.4E-03 3.0E-04 5.1 E-04 1.3E-03 2.6E-03 3.3E-03 0.70 1.0E-03 1.9E-04 3.3E-04 8.8E-04 2.1 E-03 2.7E-03 0.85 6.9E-04 1.0E-04 1.9E-04 5.8E-04 1.5E-03 2.0E-03 1.00 4.9E-04 5.9E-05 1.2E-04 3.7E-04 9.9E-04 1.4E-03 1.20 3.1 E-04 2.5E-05 5.6E-05 2.4E-04 7.6E-04 1.1 E-03 1.40 2.0E-04 1.5E-05 3.5E-05 1.4E-04 5.1 E-04 7.5E-04 1.60 1.3E-04 7.3E-06 1.9E-05 9.4E-05 3.8E-04 5.8E-04 1.80 9.0E-05 4.2E-06 1.2E-05 6.2E-05 2.7E-04 4.3E-04 2.0 6.4E-05 1.8E-06 6.2E-06 4.2E-05 2.0E-04 3.3E-04 2.5 2.8E-05 4.9E-07 2.1 E-06 1.7E-05 9.9E-05 1.8E-04 3.0 1.4E-05 1.9E-07 9.2E-07 8.6E-06 5.1 E-05 9.6E-05 4.0 4.5E-06 2.7E-08 1.8E-07 2.1 E-06 1.5E-05 3.2E~05 5.0 1.7E-06 3.8E-09 3.3E-08 6.6E-07 6.4E-06 1.5E-05

Enclosure 1 PG&E Letter DCL-15-035 Appendix A Page 10 of 13 Table.A2.0-5: Mean and Fractiles of Hazard for the Control Point for 2.5 Hz Spectral Acceleration 2.5 Hz Mean 5th 16th 50th 84th 95th PSA (g) 0.02 2.0E-01 1.5E-01 1.6E-01 1.8E-01 2.2E-01 2.4E-01 0.05 7.4E-02 4.5E-02 4.9E-02 5.7E-02 6.9E-02 7.7E-02 0.10 2.9E-02 1.5E-02 1.7E-02 2.1 E-02 2.7E-02 3.2E-02 0.15 1.6E-02 7.2E-03 8.5E-03 1.1 E-02 1.4E-02 1.7E-02 0.20 1.0E-02 4.4E-03 5.3E-03 7.0E-03 9.2E-03 1.1 E-02 0.25 7.1 E-03 3.0E-03 3.7E-03 4.9E-03 6.7E-03 8.1 E-03 0.30 5.3E-03 2.0E-03 2.5E-03 3.5E-03 4.8E-03 5.9E-03 0.40 3.3E-03 1.1 E-03 1.5E-03 2.2E-03 3.1 E-03 3.8E-03 0.50 2.3E-03 6.9E-04 9.3E-04 1.4E-03 2.2E-03 2.8E-03 0.60 1.6E-03 4.2E-04 5.9E-04 9.4E-04 1.5E-03 2.0E-03 0.70 1.2E-03 3.0E-04 4.3E-04 7.1 E-04 1.2E-03 1.6E-03 0.85 8.3E-04 1.6E-04 2.4E-04 4.4E-04 8.2E-04 1.1 E-03 1.00 6.1 E-04 8.2E-05 1.3E-04 2.6E-04 5.2E-04 7.8E-04 1.20 3.7E-04 4.3E-05 7.4E-05 1.7E-04 3.7E-04 5.9E-04 1.40 2.5E-04 2.4E-05 4.1 E-05 9.7E-05 2.3E-04 3.9E-04 1.60 1.8E-04 1.4E-05 2.6E-05 6.6E-05 1.7E-04 2.9E-04 1.80 1.3E-04 7.8E-06 1.5E-05 4.2E-05 1.2E-04 2.2E-04 2.0 9.4E-05 4.2E-06 9.1 E-06 2.8E-05 8.3E-05 1.6E-04 2.5 4.6E-05 1.3E-06 3.3E-06 1.2E-05 4.0E-05 7.9E-05 3.0 2.4E-05 4.0E-07 1.2E-06 5.0E-06 2.0E-05 4.4E-05 4.0 8.4E-06 5.5E-08 1.9E-07 1.2E-06 5.8E-06 1.5E-05 5.0 3.5E-06 1.4E-08 5.7E-08 3.9E-07 2.4E-06 6.8E-06

Enclosure 1 PG&E Letter DCL-15-035 Appendix A Page 11 of 13 Table A2.0-6: Mean and Fractiles of Hazard for the Control Point for 1 Hz Spectral Acceleration 1.0 Hz Mean 5m 16tn 5om 84tn 95tn PSA (g) 0.02 6.3E-02 3.0E-02 3.2E-02 6.4E-02 7.2E-02 7.5E-02 0.05 1.7E-02 6.6E-03 7.7E-03 1.4E-02 1.7E-02 1.8E-02 0.10 5.3E-03 1.7E-03 2.3E-03 4.2E-03 5.6E-03 6.2E-03 0.15 2.7E-03 6.5E-04 1.0E-03 1.9E-03 2.9E-03 3.4E-03 0.20 1.7E-03 3.1 E-04 5.5E-04 1.2E-03 1.9E-03 2.3E-03 0.25 1.1 E-03 1.7E-04 3.4E-04 7.6E-04 1.3E-03 1.7E-03 0.30 8.1 E-04 8.2E-05 1.8E-04 4.8E-04 9.5E-04 1.3E-03 0.40 4.8E-04 2.7E-05 7.6E-05 2.5E-04 6.0E-04 8.4E-04 0.50 2.8E-04 1.2E-05 3.6E-05 1.3E-04 3.6E-04 5.4E-04 0.60 1.8E-04 4.7E-06 1.6E-05 7.1 E-05 2.2E-04 3.5E-04 0.70 1.2E-04 2.4E-06 9.1 E-06 4.5.E-05 1.5E-04 2.6E-04 0.85 7.3E-05 9.1 E-07 3.8E-06 2.3E-05 8.7E-05 1.6E-04 1.00 4.3E-05 3.4E-07 1.5E-06 1.1 E-05 4.6E-05 8.8E-05 1.20 2.4E-05 1.2E-07 6.6E-07 5.8E-06 2.9E-05 5.9E-05 1.40 1.4E-05 4.2E-08 2.6E-07 2.7E-06 1.5E-05 3.3E-05 1.60 9.2E-06 1.8E-08 1.3E-07 1.5E-06 9.8E-06 2.2E-05 1.80 5.9E-06 7.7E-09 6.0E-08 8.5E-07 6.2E-06 1.4E-05 2.0 4.0E-06 3.3E-:-09 2.8E-08 4.8E-07 3.9E-06 9.5E-06 2.5 1.7E-06 6.7E-10 6.8E-09 1.5E-07 1.5E-06 4.2E-06 3.0 7.9E-07 1.4E-10 1.6E-09 5.0E-08 5.9E-07 1.8E-06 4.0 2.2E-07 1.3E-11 1.7E-10 6.2E-09 1.1 E-07 4.4E-07 5.0 8.2E-08 2.6E-12 4.1E-11 1.5E-09 3.8E-08 1.7E-07

Enclosure 1 PG&E Letter DCL-15-035 Appendix A Page 12 of 13 Table A2.0-7: Mean and Fractiles of Hazard for the Control Point for 0.5 Hz Spectral Acceleration 0.5 Hz Mean 5th 16th 50th 84th 95th PSA (g) 0.02 2.0E-02 7.8E-03 9.0E-03 1.8E-02 2.2E-02 2.4E-02 0.05 4.5E-03 1.3E-03 1.7E-03 3.5E-03 4.7E-03 5.5E-03 0.10 1.3E-03 2.0E-04 3.4E-04 8.7E-04 1.5E-03 2.0E-03 0.15 5.6E-04 4.9E-05 1.1 E-04 3.0E-04 7.0E-04 1.1 E-03 0.20 3.1 E-04 1.6E-05 4.0E-05 1.5E-04 4.2E-04 7.1 E-04 0.25 1.8E-04 5.1 E-06 1.5E-05 7.0E-05 2.5E-04 4.6E-04 0.30 1.2E-04 2.3E-06 7.5E-06 3.6E-05 1.6E-04 3.0E-04 0.40 5.6E-05 4.8E-07 2.1 E-06 1.4E-05 7.5E-05 1.7E-04 0.50 2.9E-05 9.8E-08 6.2E-07 5.2E-06 3.6E-05 9.2E-05 0.60 1.6E-05 4.1 E-08 2.4E-07 2.4E-06 1.9E-05 5.4E-05 0.70 1.0E-05 1.1 E-08 9.1 E-08 1.1 E-06 1.2E-05 3.4E-05 0.85 5.5E-06 3.1 E-09 2.9E-08 4.5E-07 5.4E-06 1.8E-05 1.00 3.0E-06 1.0E-09 1.1 E-08 1.7E-07 2.4E-06 1.0E-05 1.20 1.5E-06 2.3E-10 3.6E-09 7.5E-08 1.3E-06 5.5E-06 1.40 8.7E-07 8.2E-11 1.2E-09 2.8E-08 5.3E-07 2.7E-06 1.60 5.2E-07 3.2E-11 5.2E-10 1.3E-08 3.0E-07 1.7E-06 1.80 3.2E-07 1.3E-11 2.3E-10 6.2E-09 1.7E-07 1.1 E-06 2.0 2.1 E-07 4.3E-12 8.3E-11 2.8E-09 8.9E-08 6.5E-07 2.5 S.OE-08 6.7E-13 9.3E-12 6.3E-10 2.9E-08 2.5E-07 3.0 3.6E-08 1.1 E-13 1.1E-12 . 1.4E-10 9.6E-09 9.7E-08 4.0 9.3E-09 S.OE-15 3.8E-14 5.4E-12 1.5E-09 2.1 E-08 5.0 3.2E-09 9.7E-16 2.3E-15 5.3E-13 3.9E-10 6.9E-09

Enclosure 1 PG&E Letter DCL-15-035 Appendix A Page 13 of 13 Table A3.0-1: Median Amplification Factors and Epistemic Uncertainty for the Control Point Using the Empirical Site Response Approach. (Amplification is with respect to a reference rock site with Vs 30 = 760 m/s and kappa= 0.041 seconds).

logarithmic Median Standard Deviation Freq (Hz) Amplification (LN units) 100.00 0.74 0.20 50.00 0.73 0.20 33.30 0.70 0.20 20.00 0.59 0.20 13.30 0.59 0.21 10.00 0.59 0.22 6.67 0.61 0.22 5.00 0.68 0.22 4.00 0.79 0.22 3.33 0.88 0.22 2.50 1.21 0.22 2.00 1.21 0.22 1.33 1.21 0.23 1.00 1.00 0.24 0.67 1.00 0.26 0.50 1.00 0.27 0.33 1.00 0.35 0.20 1.00 0.35 0.10 1.00 0.35

Enclosure 1 PG&E Letter DCL-15-035 Appendix 8 Page 1 of 9 Appendix 8- Long Term Seismic Program Seismic Margin Spectrum

Enclosure 1 PG&E Letter DCL-15-035 Appendix 8 Page 2 of 9 81.0 Introduction The purpose of this Appendix is to document the seismic margins associated with the 1988 Long Term Seismic Program (LTSP) evaluation of Diablo Canyon Power Plant (DCPP) (see the 1988 DCPP LTSP Final Report (PG&E 1988), the 1991 Addendum to the DCPP LTSP Final Report (PG&E 1991 ), and the Supplement No. 34 of the Safety Evaluation Report (SER) for DCPP (NRC 1991 )). The resulting response spectrum, herein, is defined as the LTSP seismic margin spectrum.

82.0 Long Term Seismic Program Background License Condition No. 2.C.(7) of the DCPP Unit 1 operating license, required, in part that:

"PG&E shall develop and implement a program to reevaluate the seismic design bases used for the DCPP."

Pacific Gas and Electric Company's (PG&E's) seismic reevaluation effort in response to the license condition was titled the "Long Term Seismic Program."

The LTSP included a seismic probabilistic risk assessment (SPRA) and a deterministic seismic margin assessment (SMA). The results of the LTSP are described in the 1988 LTSP Final Report (PG&E 1988) and the 1991 Addendum to the LTSP Final Report (PG&E 1991 ). The Nuclear Regulatory Commission's (NRC's) review and acceptance of the LTSP evaluations are documented in DCPP SER Supplement 34 (NRC 1991 ).

82.1 LTSP Ground Motion Site-specific free-field ground motions were developed by PG&E based on the following (PG&E 1988, Chapters 2 through 4):

(a) regional geology, seismology, geophysics, and tectonics investigations (b) characterization of seismic source (c) characterization of ground motions, using both empirical analysis and numerical modeling PG&E's horizontal site-specific 1988 LTSP response spectrum is shown in Figure 82.1-1 (PG&E 1988, Figure 7-2) and tabulated in Table 82.1-1. Note

Enclosure 1 PG&E Letter DCL-15-035 Appendix 8 Page 3 of 9 that the 84th percentile response spectrum was used as input to the deterministic evaluations.

I I I I I iII I I 2 5 10 50 100 Frequency (Hz)

Figure 82.1-1: Horizontal 1988 LTSP Response Spectrum for DCPP (From LTSP Final Report, Figure 7 -2)

Enclosure 1 PG&E Letter DCL-15-035 Appendix 8 Page 4 of 9 Table 82.1-1: Horizontal 1988 LTSP Response Spectrum for DCPP (5%) Damping)

Period Frequency 84th Percentile Spectral Acceleration (sec.) (Hz) (g) 0.0250 40.000 0.830 0.0303 33.000 0.830 0.0400 25.000 0.964 0.0500 20.000 1.110 0.0700 14.286 1.344 0.0850 11.765 1.508 0.1000 10.000 1.654 0.1200 8.333 1.819 0.1400 7.143 1.918 0.1500 6.667 1.947 0.1700 5.882 1.976 0.2000 5.000 2.006 0.2500 4.000 2.015 0.3000 3.333 1.962 0.4000 2.500 1.763 0.5000 2.000 1.554 0.7500 1.333 1.109 1.0000 1.000 0.831 1.5000 0.667 0.524 2.0000 0.500 0.356 82.2 LTSP HCLPF Capacities The high-confidence-low-probability-of-failure (HCLPF) capacities of structures, systems, and components that were found to be governing in the deterministic seismic margin assessment associated with the implementation of the LTSP are described in Chapter 7 of the 1988 LTSP Final Report (PG&E 1988) and updated in Chapter 7 of the 1991 Addendum of the LTSP Final Report (PG&E 1991).

The fragilities and HCLPF capacities for DCPP structures, systems, and components are defined based on the 5 percent damped horizontal spectral acceleration value, averaged over the frequency range of 3.0 to 8.5 Hz. This is illustrated in Figure 82.2-1 (based on Figure 7-40 from the 1988 LTSP Final Report - PG&E 1988).

Enclosure 1 PG&E Letter DCL-15-035 Appendix 8 Page 5 of 9 3 8.5 Frequency (Hz)

Figure 82.2-1: Frequency Range Associated with HCLPF Capacities for DCPP (From PG&E 1988, Figure 7-40) 83.0 Minimum Seismic Margin As indicated in Tables 7-1 and 7-2 of the 1988 LTSP Final Report (PG&E 1988), the turbine building is the structure with the lowest HCLPF capacity and the emergency diesel generator (EDG) control panels are the component whose failure could lead to significant seismic risk to the plant with the lowest HCLPF capacity. The HCLPF capacities of these structures, systems, and components were updated by PG&E using the conservative deterministic failure margins method (PG&E 1990) and summarized in Table A7-1 of the 1991 Addendum to LTSP Final Report (PG&E 1991). The HCLPF capacities for the turbine building and the EDG control panels are listed in Table 83.0-1.

Enclosure 1 PG&E Letter DCL-15-035 Appendix B Page 6 of 9 Table 83.0-1: Limiting HCLPF Capacities for DCPP (PG&E 1988 and PG&E 1991) sse 84th Percentile HCLPF Capacity (g)

Name PG&E 19881 PG&E 1991 2 Turbine Building 2.21 2.89 EDG Control Panels 2.69 2.62 Since the average 5 percent damped spectral acceleration for the 84th percentile 1988 LTSP horizontal response spectrum is 1.94 g (see Figure 82.2-1) and the HCLPF capacity for the limiting structure, system, and components (EDG control panels) is 2.62 g, the minimum seismic margin is 2.62 g/1.94 g = 1.35.

Note that Section 3.8.1.5 of the NRC's SER associated with the 1988 LTSP (NRC 1991) states:

"the staff generally agrees with the PG&E's statement that all components whose failure could lead to seismic risk to the plant have at least a margin of 40 percent when their HCLPF capacities are compared with the 84-percent, site-specific, ground-motion demand."

Therefore, the use of a minimum seismic margin of 1.35 is conservative relative to the NRC's conclusions for the 1988 LTSP.

84.0 LTSP Seismic Margin Spectrum The resulting LTSP seismic margin spectrum is the product of the 84th percentile 1988 LTSP ground motion response spectrum (Table 82.1-1) and the minimum seismic margin from Section 83.0 (1.35). The LTSP seismic margin spectrum is shown in Figure 84.0-1 and tabulated in Table 84.0-1.

1988 HCLPF capacities are from Tables 7-1 and 7-2 of the 1988 LTSP Final Report (PG&E 1988).

2 1991 HCLPF capacities are from Table A7-1 of the 1991 Addendum to the LTSP Final Report (PG&E 1991 ).

Enclosure 1 PG&E Letter DCL-15-035 Appendix B Page 7 of 9 3.0 v '-,~

~

~- LTSP Seismic Margin Spectrum v

2.5

~~

2.0 J ~

§

~

1:

0

...Cl) 1.5 I \

~v "'~

a; u

u

<(

iij uCl) 1.0 II" Q.

C/)

ll 0.5 IJ 0.0 0.10 1.00 10.00 100.00 Frequency (Hz)

Figure 84.0-1: LTSP Seismic Margin Spectrum for DCPP (5%> Damping)

Enclosure 1 PG&E Letter DCL-15-035 Appendix B Page 8 of 9 Table 84.0-1: LTSP Seismic Margins Spectrum for DCPP (5%, Damping)

Period Frequency Spectral Acceleration (sec) (Hz) (g) 0.0100 100.0000 1.121 0.0250 40.0000 1.121 0.0303 33.0000 1.121 0.0400 25.0000 1.301 0.0500 20.0000 1.499 0.0700 14.2857 1.814 0.0850 11.7647 2.036 0.1000 10.0000 2.233 0.1200 8.3333 1 2.456 0.1400 7.1429 2.589 0.1500 6.6667 2.628 0.1700 5.8824 2.668 0.2000 5.0000 2.708 0.2500 4.0000 2.720 0.3000 3.3333 2.649 0.4000 2.5000 2.380 0.5000 2.0000 2.098 0.7500 1.3333 1.497 1.0000 1.0000 1.122 1.5000 0.6667 0.707 2.0000 0.5000 0.481

Enclosure 1 PG&E Letter DCL-15-035 Appendix 8 Page 9 of 9 85.0 References 85.1 Pacific Gas and Electric Company (a) PG&E 1988, PG&E Report, "Final Report of the Diablo Canyon Long Term Seismic Program for the Diablo Canyon Power Plant," Enclosure to PG&E Letter DCL-88-192, "Long Term Seismic Program Completion," dated July 31, 1988 (b) PG&E 1990, PG&E Report, "Additional Deterministic Evaluations Performed to Assess Seismic Margins of the Diablo Canyon Power Plant, Units 1 and 2," Enclosure to PG&E Letter DCL-90-226, "Long Term Seismic Program Additional Deterministic Evaluations," dated September 18, 1990 (c) PG&E 1991, PG&E Report, "Addendum to the 1988 Final Report of the Diablo Canyon Long Term Seismic Program," Enclosure to PG&E Letter DCL-91-027, "Addendum to Long Term Seismic Program Final Report," dated February 13, 1991 85.2 Nuclear Regulatory Commission (a) NRC 1991, "Safety Evaluation Report related to the operation of Diablo Canyon Nuclear Power Plant, Units 1 and 2, Docket Nos. 50-275 and 50-323, Pacific Gas and Electric Company," NUREG-0675, Supplement No. 34, dated June 1991

Enclosure 1 PG&E Letter DCL-15-035 Appendix C Page 1 of 18 Appendix C - PPRP Endorsements

Enclosure 1 PG&E Letter DCL-15-035 Appendix C Page 2 of 18 Diablo Canyon Seismic Source Characterization SSHAC Project Participatory Peer Review Panel Closure Letter

Enclosure 1 PG&E Letter DCL-15-035 Appendix C Page 3 of 18 March 10, 2015 Mr. KentS. Ferre Project Manager Pacific Gas & Electric Company 245 Market St.

San Francisco, CA 94177

SUBJECT:

Diablo Canyon Seismic Source Characterization SSHAC Project Participatory Peer Review Panel Closure Letter

Dear Mr. Ferre,

The Participatory Peer Review Panel (PPRP, the "Panel") for the Diablo Canyon Seismic Source Characterization (SSC) SSHAC Project (the "DCPP SSC Project") is pleased to issue this PPRP Closure Letter containing our findings with respect to the project. The four Panel members (Kevin J. Coppersmith, Steven M. Day, Neal W.

Driscoll, . and Thomas K. Rockwell) participated in the Project in a manner fully consistent with the SSHAC Guidance 1 for a SSHAC Level 3 study. The Panel was actively engaged in all phases and activities of the Project's implementation, including the development of the Project Plan, review of analyses performed by the Technical Integration (TI) Team to support the evaluation and integration processes, review of interim products, and review of the draft project report and the final project report.

Consistent with regulatory guidance for SSHAC projects, the role of the PPRP is to conduct a review of both the process followed and the technical assessments made by the Tl Team. Accordingly, this letter documents the activities that the PPRP has undertaken in its review of the Project, its review of the adequacy of the process followed, and its findings relative to the technical adequacy of the resulting sse model.

Consistent with SSHAC Guidance, the Panel was fully engaged in peer-review interactions with the DCPP SSC Tl Team throughout the entire project performance-from development of the Project Plan through finalization the Project Report. The participatory peer review process entails the continual review of a project from its start to its completion. Thus, proper implementation requires adequate opportunity during the conduct of the study for the PPRP to understand the data, models, and methods being evaluated; the analyses performed for the study; the Tl Team's integration activities that lead to sse models and uncertainties; and the completeness and clarity of the technical 1

Budnitz, R.J., G. Apostolakis, D.M. Boore, L.S. Cluff, K.L. Coppersmith, C.A. Cornell, and P.A. Morris (1997). Recommendations for Probabilistic Seismic Hazard Analysis: Guidance on Uncertainty and the Use of Experts (known as the "Senior Seismic Hazard Analysis Committee Report", or "SSHAC Guideline"), NUREG/CR-6372, U.S. Nuclear Regulatory Commission, TIC; 235076, Washington, D.C.

NRC (2012). Practical Implementation Guidelines for SSHAC Level3 and 4 Hazard Studies, NUREG-2117, U.S. Nuclear Regulatory Commission, Washington, D.C.

DCPP SSG PPRP Closure Letter 3-10-15 Page 1

Enclosure 1 PG&E Letter DCL-15-035 Appendix C Page 4 of 18 justifications given in the documentation. Participatory review also involves opportunities for the PPRP to provide its reviews and comments in written and verbal form during the conduct of the project, such that the suggestions and recommendations made by the Panel can be considered by the Tl Team in a timely fashion prior to completion of the work.

The meetings attended and observed by the PPRP for the DCPP sse project are summarized in the table below. The PPRP assumed an active participant role in Workshop #3 and the PPRP Briefings.

Meeting Type Date(s) Topic(s)

Kick off meeting August 25, 2011 Kick off meeting November 29 - Workshop #1 Workshop December 1, 2011 Working Meeting March 28, 2012 Characteristic earthquake review Logic tree and sensitivity for magnitude PDF Working Meeting April11, 2012 and earthquake recurrence Working meeting May 14, 2012 sse work plan review, overall logic tree structure Project and Workshop #2 planning, logic tree Working Meeting June 19-20, 2012 structure, sensitivity analyses, Hosgri, Los Osos, San Luis Bay, and Shoreline logic trees Workshop #2 planning, logic tree sensitivity Working Meeting October 25-26, 2012 review Workshop November 6-8, 2012 Workshop #2 Review Workshop 2, 2013 plan, data needs Working Meeting December 11, 2012 table 2013 Schedule and Assignments, Offshore Working Meeting February 20, 2013 seismic stratigraphy project PE presentation Working Meeting September 20, 2013 Alternative fault model evaluation Working Meeting November 5-6, 2013 Presentation of draft SSC Model V2 Rupture Models, Sam Johnson PE Working Meeting March 5, 2014 presentation, Recurrence model Workshop March 25-27, 2014 Workshop #3 Modifications to Preliminary Fault and Working Meeting June 23-24, 2014 Deformation models, open items following Preliminary SSC Model PPRP Briefing July 24-25, 2014 DCPP SSC Model Final PPRP Briefing, Part 1 DCPP SSC Model Final PPRP Briefing, Part 2, PPRP Briefing October 31, 2014 Time Dependency Model The PPRP, collectively and individually, understood fully the SSHAC Guidance for a structured participatory peer review and the requirements for a SSHAC Level 3 project; had full and frequent access to information and interacted extensively with the Tl Team throughout the project; provided peer-review comments at multiple stages; and, as documented within the final report, was fully engaged to meet its peer-review obligations in an effective way. The Panel concludes that its ongoing review and DCPP SSC PPRP Closure Letter 3-10-15 Page2

Enclosure 1 PG&E Letter DCL-15-035 Appendix C Page 5 of 18 feedback interactions with the Tl Team during the conduct of the DCPP SSC project activities fully met the expectations for a SSHAC Level 3 study.

SSHAC Process Review Fundamentally, the question of whether or not a project follows a proper SSHAC Level 3 process is answered by comparing the process used with the process outlined generally in the SSHAC implementation guidance issued by the NRC. NRC (2012, Table 4-1) identifies the essential steps in a SSHAC Level 3 study that define the minimum required activities:

1. Select SSHAC Level

2. DevelopProject Plan

3. Select project participants

4. Develop project database

5. Hold workshops (minimum of three, focused on available data, alternative models, and feedback)

6. Develop preliminary model(s) and Hazard Input Document (HID)

7. Perform preliminary hazard calculations and sensitivity analyses

8. Finalize models in light of feedback

9. Perform final hazard calculations and sensitivity analyses

10. Develop draft.and final project report 11 . Particip~tory peer review of entire process Review of the project documentation, as well as ongoing participatory peer review throughout the project, leads to the conclusion that the essential steps of a SSHAC Level 3 process have been followed in the DCPP SSC Project. For example, a Project Plan was issued at the start of the project that outlined the project activities and the roles and responsibilities of all project participants; a major effort was devoted to developing a project database that was accessible to the Tl Team; three topical workshops were held to identify available data, to discuss alternative methods and models, and to present feedback based on preliminary interpretations; preliminary models were developed and seismic hazard calculations conducted to provide additional feedback to the Tl Team; draft and final reports were developed that documented the process followed and the technical assessments made; and a peer review process was conducted that included both participatory aspects and late-stage reviews (e.g., review of the draft report).

In light of due consideration of the essential elements of a SSHAC process and the specific manner in which the DCPP sse Project was conducted, the Panel concludes that the project performed all essential steps consistent with current state-of-practice guidance for a SSHAC Level 3 process.

As explained in NUREG-2117 (NRC, 2012), the SSHAC process consists of two important activities , described as follows:

DCPP SSG PPRP Closure Letter 3-10-15 Page 3

Enclosure 1 PG&E Letter DCL-15-035 Appendix C Page 6 of 18 "The fundamental goal of a SSHAC process is to carry out properly and document completely the activities of evaluation and integration, defined as:

• Evaluation: The consideration of the complete set of data, models, and methods proposed by the larger technical community that are relevant to the hazard analysis.

• Integration: Representing the center, body, and range of technically defensible interpretations in light of the evaluation process (i.e., informed by the assessment of existing data, models, and methods)."

These activities are essential to any SSHAC study and the Panel has followed the DCPP SSC Project closely to ensure that both activities have been adequately conducted. A third key activity of a SSHAC process is the documentation phase, which ensures that all evaluation and integration activities are properly supported and captured in the written record.

During the Evaluation phase of the DCPP SSC Project, the Tl Team considered new data, models, and methods that have become available in the technical community in recent years. Importantly, the Tl Team evaluated the wealth of onshore and offshore data that have recently been collected as part of the AB 1632 studies required by the State of California, as well as numerous data collection activities conducted by federal and state researchers such as the USGS and California Geological Survey. Workshop

1. 1 was devoted to reviewing these disparate datasets and to identifying which data could be used to develop the SSC model. Continuing the evaluation process, Workshop

1. 2 focused on alternative methods and models that pertain to the hazard-significant SSC issues. Significant representation of these alternative viewpoints was made by the participation of resource and proponent experts at the workshop. The Panel concludes that the Tl Team conducted an adequate evaluation process.

The Integration phase of the project entails the building of the SSC model to capture current knowledge and uncertainties. Care was given in the model-building process to appropriately distinguish between epistemic uncertainties and aleatory variability. The Tl ,

Team conducted multiple working meetings and other interactions to ensure that the center, body, and range of technically defensible interpretations were included in the SSC model. Importantly, the Team also received appropriate communications from the Project Technical Integrator (PTI) regarding the required elements of the SSC model needed for consistency with the ground motion models being developed in parallel as part of the Southwest United States Ground Motion Characterization Project. A preliminary SSC model was developed prior to Workshop #3 and hazard calculations were conducted for purposes of sensitivity analysis feedback. At Workshop #3, the PPRP was given the opportunity to provide their feedback on the preliminary model and to challenge the Tl Team with respect to the technical justifications for their SSC model assessments and associated uncertainties. The Tl Team used the feedback gained from the hazard calculations and PPRP comments to prioritize their efforts in the final SSC model development process. The tectonic complexity of the DCPP study region requires a complex sse model to completely and appropriately capture current DCPP SSC PPRP Closure Letter 3-10-15 Page4

Enclosure 1 PG&E Letter DCL-15-035 Appendix C Page 7 of 18 knowledge and uncertainties. Efforts were made to simplify the models when it could be shown that detailed characterization would not lead to significant differences in the hazard results. The Panel concludes that such simplifications were justified and appropriate.

In support of the Documentation phase of the project, the Tl Team developed a comprehensive Draft Report that was provided to the PPRP for detailed review. To ensure that schedule constraints for the project were met, the report was provided to the PPRP in major installments consisting of multiple chapters and appendices. The role of the Panel's review was specifically to ensure that all evaluation and integration activities were described completely, and that the sse model was adequately justified technically. Written comments were provided by the PPRP to the Tl Team and, after revision of the report in light of those comments, written responses by the Team were provided to the PPRP to ensure proper closure of each comment.

Based on the review of the evaluation and integration activities conducted by the Tl Team, as well as the documentation of these activities in the PSHA report, the PPRP concludes that the SSHAC process has been adequately conducted.

SSHAC Technical Review The role of the PPRP in the review of the technical aspects of the project is specified in NUREG-2117 (USNRC, 2012) as follows:

"The PPRP fulfills two parallel roles, the first being technical review.

This means that the PPRP is charged with ensuring that the full range of data, models, and methods have been duly considered in the assessment and also that all technical decisions , are adequately ju~tified and documented.

The responsibility of the PPRP is to provide clear and timely feedback to the TI/TFI and project manager to ensure that any technical or process deficiencies are identified at the earliest possible stage so that they can be corrected. More commonly, the PPRP provides its perspectives and advice regarding the manner in which ongoing activities can be improved or carried out more effectively. In terms of technical review, a key responsibility of the PPRP is to highlight any data, models or proponents that have not been considered. Beyond completeness, it is not within the remit of the PPRP to judge the weighting of the logic-trees in detail but rather to judge the justification provided for the models included or excluded, and for the weights applied to the logic-tree branches."

Consistent with this NRC guidance, the PPRP reviewed at multiple times during the project the Tl Team's evaluations of data, models, and methods, as well as the Team's development and technical justification for the SSC model. These reviews DCPP SSC PPRP Closure Letter 3-10-15 Page 5

Enclosure 1 PG&E Letter DCL-15-035 Appendix C Page 8 of 18 included conference calls, post-workshop meetings, written comments, and the review of drafts of the PSHA report. Through these reviews, the PPRP communicated feedback to the Tl Team regarding data and approaches that did not appear to have been considered, suggestions for methods being used within the technical community that should be evaluated by the Team, and recommendations for ways that the documentation could be improved to strengthen the discussion of the technical bases for the assessments.

Requirements for a successful integration or model-building phase of a SSHAe Level 3 process are that it is informed by a complete evaluation of all relevant data, models, and methods during the evaluation phase of the project, that all assessments are technically defensible, and that the developed models are thoroughly documented so as to be transparent to users. During the course of the integration process, the Tl Team found that the available set of methods or model elements were not sufficient to properly and completely represent current knowledge and uncertainty in some components of the model. In those cases, the Tl Team developed a refined set of model elements or concepts that-although they are not radically different from current practice-provide approaches that the Team concluded were more effective in modeling technical aspects than available tools. For example, the SSe model includes a series of fault geometry models and rupture sources that span the range of credible interpretations of available data. Key aspects of these rupture sources are assessed based on a consideration of constraints from geologic, geomorphic, geophysical, and seismological data.

A strong requirement of the SSHAe Guidance is that all elements of the SSe model must be completely documented and adequately justified technically. This is particularly true of new model elements that have not enjoyed the benefit of use on multiple projects or that have not been subject to peer review within the larger technical community.

Particularly in those cases, the PPRP must ensure that the model elements are sufficiently justified and adequately defended in the project documentation. This has been the case in the DePP SSe Project. Examples of new approaches include the use of a slip rate allocation approach to characterizing rupture sources, incorporating new magnitude frequency distributions, and the adoption of a non-Poisson temporal model.

To review these concepts and applications to the sse model, the PPRP was present as observers at workshops where these concepts were presented, provided written comments in response to those workshops, asked questions and provided feedback in a workshop environment regarding the adequacy of the technical justification for the models, participated in briefings and conference calls related to the topics, and provided detailed written comments related to the draft project report. Based on this process of participatory review throughout the course of the project, the PPRP concludes that the bases for the sse model elements are technically defensible, and that the technical assessments and process for arriving at the model elements are adequately documented.

Throughout the course of the PPRP review, the Tl Team was responsive to the questions, comments, and suggestions made by the PPRP relative to the technical aspects of the project. Therefore, the Panel concludes that the technical aspects of the DCPP SSC PPRP Closure Letter 3-10-15 Page6

Enclosure I PG&E Letter DCL-15-035 Appendix C Page 9 of 18 projects have been adequately addressed and all written comments provided by the Panel, including those made following each workshop and those pertaining to the Draft Report, are hereby considered to be closed.

Conclusion Based on our observation of the completeness and professional standard by which the evaluation and integration activities were conducted, the Panel concludes that the data, models, and methods within the larger technical community have been properly evaluated, and that the center, body, and range of technically defensible interpretations have been appropriately represented in the SSC model. Accordingly, the Panel concludes that both the process and technical aspects of the DCPP sse assessment fully meet accepted guidance and current expectations for a SSHAC Level 3 study.

We appreciate the opportunity to provide our review of the project.

Sincerely, DCPP PPRP Members

~$L)t7 Kevin J. Coppersmith, Chair Steven M. Day

(* ()

• \~

Neal W. Driscoll J ,ku:*tt t~ l.t-47 Thomas K. Rockwell DCPP SSC PPRP Closure Letter 3-10-15 Page 7

Enclosure 1 PG&E Letter DCL-15-035 Appendix C Page 10 of 18 Participatory Peer Review Panel Closure Letter, Southwest United States Ground Motion Characterization Level 3 SSHAC Project and Tl Team - PM Response to PPRP Closure Letter

Enclosure 1 PG&E Letter DCL-15-035 Southwestern United States Appendix c 11 18 Ground Motion Characterization SSHAC Level 3 Page of TECHNICAL REPORT- Rev. 2 PPRP CLOSURE LETTER March 10, 2015 Dr. Carola Di Alessandro SWUS Project Manager GeoPentech, Inc.

525 N. Cabrillo Park Drive, Suite 280 Santa Ana, CA 92701

Subject:

Participatory Peer Review Panel Closure Letter, Southwest United States Ground Motion Characterization Level 3 SSHAC Project

Dear Dr. Di Alessandro:

The Participatory Peer Review Panel (PPRP, also referred to herein as the "Panel") for the Southwest United States (SWUS) Ground Motion Characterization (GMC) Project is pleased to issue this PPRP Closure Letter. Herein we describe our participation in the SWUS GMC SSHAC Level3 project and present our findings. Pursuant to the guidelines for a SSHAC Level 3 study (NUREG/CR-6372; NUREG-2117), the PPRP was engaged at all stages of the project, including review of the final Project Plan, Workshop agendas and participant lists; the planning of the evaluation and model integration activities; and review of the project documentation. Throughout the project, the Panel reviewed and provided regular feedback on both the process followed, and the technical assessments made, by the Technical Integrator (TI) Team. By this letter the Panel documents the activities it has performed in the course of its review, its assessment of the process followed relative to SSHAC Level3 expectations, and its assessment of the technical rationale underlying the GMC model.

The PPRP issued a previous letter dated February 24, 2015 . In that letter, the Panel noted that there were limitations in the completeness and clarity of the project documentation. Those limitations were noted as exceptions to the Panel's finding that the project successfully met SSHAC Level 3 expectations. Since that time, the Tl Team has produced a final report, designated Rev2, addressing the final set of comments from the Panel (PPRP Submittal No.3, February 20, 2015). The Panel has reviewed Rev2 (including a short addendum supplied to the PPRP in draft form on March 9 which the Tl Team has assured in writing will be incorporated in the final version) and finds that all material concerns have been adequately addressed and are now closed, apart from one remaining exception that will be described at the end of the SSHAC Process Review section below. Two GMC models were developed for application to Diablo Canyon Power Plant (DCPP) and Palo Verde Nuclear Generating Station (PVNGS),

respectively . The exception applies only to the GMC model for DCPP, and is not relevant to the case of PVNGS.

1 Appendix B- PPRP Closure Letter Page B-1

Enclosure 1 PG&E Letter DCL-15-035 Southwestern United States Appendix c 12 18 Ground Motion Characterization SSHAC Level 3 Page of TECHNICAL REPORT- Rev. 2 PPRP Activities in Support of the SWUS GMC Review In a SSHAC Level 3 study, the PPRP fulfills two roles. The first is that of technical review, in which the Panel ensures that the full range of data, models and methods are considered and that technical decisions and judgments are adequately justified and documented. The second is that of process review, under which the Panel ensures that the study maintains conformity with the SSHAC Level 3 guidelines. To fulfill these roles, the Panel requires adequate opportunities to gain understanding of the data being used, the analyses being performed, the Tl Team's evaluations of data and models, and the technical justifications for the Tl Team's model decisions. The table below summarizes the formal project activities in which the Panel participated . Fulfilling these roles also requires the Panel to provide regular feedback to the Tl Team during the course of the project. In addition to verbal feedback during Working Meetings and Workshops, the Panel provided written comments and recommendations at key stages of the project.

Those written submittals are also noted in the table.

Date PPRP Activity June21 , 2012 Working Meeting #1 (Planning). All PPRP members attended.

July 18, 2012 Working Meeting #2 (Planning). All PPRP members attended.

August 27, 2012 Kick-off Meeting. Al l PPRP members attended.

September 17, 2012 PPRP submittal of written comments on the Project Plan.

October 8, 2012 Working Meeting #3. PPRP representatives attended as observers.

November 3, 2012 PPRP submittal of written comments on revised Project Plan.

November 29, 2012 PPRP submittal of PPRP endorsement letter for Project Plan.

December 10, 2012 ~orking Meeting #4. PPRP representatives attended as observers.

February 11, 2013 rv'\forking Meeting #5. PPRP representatives attended as observers.

March 19-21, 2013 rv'\'orkshop #1 : Critical issues and Data Needs. All PPRP members attended as observers. The PPRP provided verbal feedback to the Tl Team at the end of each day of the Workshop April 12, 2013 Working Meeting #6. PPRP representatives attended as observers.

April21 , 2013 PPRP subm ittal of written comments on Workshop #1.

May 23, 2013 orking Meeting #7. PPRP representatives attended as observers.

June 24, 2013 orking Meeting #8. PPRP representatives attended as observers.

July 16, 2013 orking Meeting #9. PPRP representatives attended as observers.

August 21, 2013 orking Meeting #10. PPRP representatives attended as observers.

October 2, 2013 orking Meeting # 11. PPRP representatives attended as observers.

October 15, 2013 orking Meeting #12. PPRP representatives attended as observers.

October 22-24, 2013 rv" orkshop #2 : Proponent Models and Alternative Interpretations. All PPRP members attended as observers. The PPRP provided verbal feedback to the Tl

!Team at the end of each day of the Workshop.

November 26, 2013 ~orking Meeting #13. PPRP representatives attended as observers.

December 3, 2013 PPRP submittal of written comments on Workshop #2.

~January 2, 2014 ~orki ng Meeting #14. PPRP representatives attended as observers.

~anuary 28-29, 2014 Special Working Meeting. All PPRP members attended as observers.

March 3, 2014 Working Meeting #15. PPRP representatives attended as observers.

March 10-12, 2014 III'Vorkshop #3 : Preliminary GMC Models and Hazard Feedback. All PPRP members attended as participants. The PPRP provided verbal feedback to the ITI Team at the end of each day of the Workshop.

March 24, 2014 III'Vorking Meeting #16. PPRP representatives attended as observers.

~pril21, 2014 PPRP submittal of written comments on Workshop #3.

2 Appendix B- PPRP Closure Letter Page B-2

Enclosure 1 PG&E Letter DCL-15-035 Southwestern United States Appendix c 13 18 Ground Motion Characterization SSHAC Level 3 Page of TECHNICAL REPORT- Rev. 2 May 14, 2014 PPRP Closure Pre-Briefing. All PPRP members attended as participants.

Wuly 17-18, 2014 PPRP Closure Briefing . All PPRP members attended as participants.

December 13, 2014 ~ubmittal No. 1 of PPRP written review comments on SWUS GMC Report:

~omments on SWUS GMC Report Rev.O, Chapters 7, 10, 11 , 12, 13, and

~ppendices L, M, N, and R.

December 16, 2014 [Teleconference, PPRP and Tl Team , to discuss the PPRP written review pomments, Submittal No. 1.

January 5, 2015 ~ubmittal No. 2 of PPRP written review comments on SWUS GMC Report:

~omments on SWUS GMC Report Rev.O, Chapters 6, 8, 9, 14, and Appendices H, I, J, K, 0 , and Q.

January 7, 2015 [Teleconference, PPRP and Tl Team, to discuss the PPRP written review pomments, Submittal No. 2.

January 26, 2015 [Teleconference, PPRP and Tl Team, to discuss the main modifications introduced in SWUS GMC Report Draft Rev.1.

February 9, 2015 [Teleconference, PPRP and Tl Team, to discuss observations from PPRP partial review of SWUS GMC Report Draft Rev.1.

February 16, 2015 [Teleconference, PPRP and Project Manager to discuss project completion schedule.

February 20, 2015 Submittal No. 3 of PPRP written review comments on SWUS GMC Report:

Comments on SWUS GMC Report Draft Rev.1.

February 24, 2015 Subm ittal of Closure Letter based on Draft Rev.1 The PPRP finds that the level of ongoing review it was able to undertake, and the opportunities afforded the PPRP to provide feedback to the Tl Team, met the expectations for a SSHAC Level 3 study. Interactions with the Tl Team provided ample opportunity for the Panel to gain an understanding of the technical bases for the Tl Team's evaluations. The Panel also was given adequate opportunity to query the Tl Team, especially in Workshop #3 and in the Pre-Closure Briefing and Closure Briefing, to assess the justification provided for their model decisions. The Tl Team provided written responses to each formal PPRP submittal, and in nearly every case the PPRP and Tl Team subsequently discussed the comments and replies in a conference call or Working Meeting.

SSHAC Process Review NUREG-2117 describes the goal of a SSHAC process as being "to carry out properly and document completely the activities of evaluation and integration, defined as:

Evaluation: The consideration of the complete set of data, models and methods proposed by the larger technical community that are relevant to the hazard analysis.

Integration: Representing the center, body, and range of technically defensible interpretations in light of the evaluation process (i.e., informed by the assessment of existing data, models, and methods)."

During the Evaluation activities, the Tl Team considered new data, models and methods that have been introduced within the technical community since the previous seismic hazard studies were conducted for nuclear power plants in California and Arizona. The 3

Appendix 8- PPRP Closure Letter Page B-3

Enclosure 1 PG&E Letter DCL-15-035 Southwestern United States Appendix c 14 18 Ground Motion Characterization SSHAC Level 3 Page of TECHNICAL REPORT- Rev. 2 Team evaluated newly available ground motion databases, ground motion prediction equations (GMPEs), and ground motion simulation techniques. Notably, the Tl Team evaluated methods for the representation of non-Gaussian aleatory variability, as well as newly available methods for the visualization and characterization of epistemic uncertainty in ground motion prediction.

The PPRP finds that the Tl Team's evaluation and the documentation thereof are consistent with the expectations for a SSHAC Level 3 study, apart from the specific reservation noted at the end of this section.

The Integration phase entails thoroughly documenting the technical bases for all elements of the GMC model, to provide assurance that the center, body and range of technically defensible interpretations have been captured. The Tl Team used a new statistical technique to generate a suite of representative models for median ground motion prediction that collectively represent the epistemic uncertainty in ground motion more broadly than do the published GMPEs alone. This technique is combined with a new method to select and weight the predictions of the expanded suite of models. The Tl Team's method for assigning weights is based on consideration of appropriate data sets and numerical simulations, with adequate justification. The Tl Team's model for aleatory variability and weighting of alternative aleatory models is also adequately justified.

The PPRP finds that the Tl Team's GMC model integration and the documentation thereof are consistent with the expectations of a SSHAC Level3 project, apart from the specific reservation noted in the next paragraph.

The Panel finds that the Tl Team's evaluation of directivity models has limitations. The Tl Team make use of a simplified directivity model to save computational time, and the final report adequately describes that model, how it is used, and some of its limitations.

However, because the simplified model is unpublished, it is also necessary for the Tl Team to document that the simplified model is appropriate for the purpose for which it is applied, in the sense that it gives results that are essentially consistent with the published and peer-reviewed model that it is intended to approximate. The final report (in the March 9 addendum) documents the performance of the simplified model through comparison with results from a hazard calculation that uses the full, published directivity model. At hazard levels of 1o-4 and above, the full model calculation confirms the conclusion obtained using the simplified model. At hazard levels below 1o- 4, however, the difference in calculated hazard between the full model and the simplified model increases with decreasing hazard level. This increasing trend has not been satisfactorily explained, has not been explored beyond the single fault case provided in the March 9 addendum, and has not been quantified in terms of impact on equal-hazard spectra at hazard levels of 1a-s and lower. Because the key rationale for the zero weighting of the directivity branch in the GMC model for periods longer than 0.5 s (the period range where the directivity effect applies) is the weak sensitivity of hazard to the directivity effect calculated using the simplified model, the PPRP finds that this weighting lacks sufficient technical justification.

4 Appendix B- PPRP Closure Letter Page B-4

Enclosure 1 PG&E Letter DCL-15-035 Southwestern United States Appendix c 15 18 Ground Motion Characterization SSHAC Level 3 Page of TECHNICAL REPORT- Rev. 2 SSHAC Technical Review NUREG-2117 describes the PPRP's technical review role as follows:

"The PPRP fulfills two parallel roles, the first being technical review. This means that the PPRP is charged with ensuring that the full range of data, models, and methods have been duly considered in the assessment and also that all technical decisions are adequately justified and documented.

The responsibility of the PPRP is to provide clear and timely feedback to the TI/TFI and project manager to ensure that any technical or process deficiencies are identified at the earliest possible stage so that they can be corrected. More commonly, the PPRP provides its perspectives and advice regarding the manner in which ongoing activities can be improved or carried out more effectively. In terms of technical review, a key responsibility of the PPRP is to highlight any data, models or proponents that have not been considered. Beyond completeness, it is not within the remit of the PPRP to judge the weighting of the logic-trees in detail but rather to judge the justification provided for the models included or excluded, and for the weights applied to the logic-tree branches."

As summarized in the table above, the PPRP reviewed the Tl Team's evaluations of data, models and methods on multiple occasions, and through various means, including written communications, in-person meetings, teleconferences, and review of the project report. The Panel was given adequate opportunity to question the Tl Team concerning details oftheir analysis, and provided feedback verbally and in writing. The Tl Team was responsive to the technical input from the Panel. The Tl Team's responses included evaluating additional data sets suggested by the Panel, undertaking additional analyses to address specific Panel technical questions or concerns, and examining and assessing alternative technical approaches suggested by the Panel.

The PPRP therefore concludes that it has been afforded an adequate basis for technical assessment of the Tl Team's evaluations and model integration. As noted above in the final paragraph of the SSHAC Process Review section, the evaluation of directivity effects has been inadequate and may constitute a technical limitation of the study. Apart from that reservation, the PPRP finds that the project meets technical expectations for a SSHAC Level 3 study.

Conclusion On the basis of its review of the SWUS GMC project, the PPRP finds that the project meets, with respect to both process and technical standards, the expectations for a 5

Appendix 8- PPRP Closure Letter Page B-5

Enclosure 1 PG&E Letter DCL-15-035 Southwestern United States Appendix c 16 18 Ground Motion Characterization SSHAC Level3 Page of TECHNICAL REPORT- Rev. 2 SSHAC Level 3 study, with the reservation cited above. That reservation pertains specifically to application of the directivity component of the GMC model to the DCPP site.

Sincerely,

~$btl' Steven M. Day Kenneth W. Campbell Chair, PPRP Member, PPRP Brian Chiou Thomas K. Rockwell Member, PPRP Member, PPRP 6

Appendix 8- PPRP Closure Letter Page B-6

Enclosure 1 PG&E Letter DCL-15-035 Southwestern United States Appendix c 17 18 Ground Motion Characterization SSHAC Level3 Page of TECHNICAL REPORT- Rev. 2 Tl TEAM- PM RESPONSE TO PPRP CLOSURE LETTER The PPRP letter identifies a limitation of the study due to the use of the Watson-Lamprey directivity model for the sensitivity studies that supported the Tl Team judgment that directivity had only a small effect on the low-frequency ground-motion hazard at DCPP. The Watson-Lamprey model provides a simplified method to include the directivity in the CY14 model in a more efficient manner by randomizing over the hypocenter locations and developing site-specific adjustments to the median and standard deviation of the ground motion for the common-form models. The limitation is related to the differences in the computed hazard if the directivity model from CY14 is applied directly into the hazard rather than using the Watson-Lamprey implementation of the CY14 directivity scaling.

This limitation does not apply to PVNGS as there are no faults within 40 km of the site in the PVNGS SSC. The directivity model of CY14 reduces the directivity effects to zero for distances greater than 40 km, so there would be no directivity effects if the CY14 model was applied directly to the hazard calculations for the PVNGS site.

For DCPP, the differences between the directivity effects computed using the CY14 model directly and using the Watson-Lamprey model are discussed in Section 6.5 of this report. Including directivity for randomized hypocenter locations leads to additional variability of the low-frequency ground motion.

This variability is combined with the total standard deviation . The key issue is if the standard deviation, developed from residuals from GMPEs that generally do not include directivity as a predictive parameter, should be reduced to account for the expected improved fit to the data if directivity parameters are included in the model. That is, should the additional aleatory variability be added to the standard deviation from the GMPEs or should it be added to a reduced standard deviation model that accounts for an improved fit if directivity parameters are included in the GMPE model.

The Watson-Lamprey model assumes that the standard deviations from the published GMPEs include the effects of variability due to directivity, and therefore, applies a reduction to standard deviation before adding the directivity effect on the standard deviation. If this reduction is not applied, then there will be an increase in the total standard deviation which leads to an increase in the hazard at low hazard levels. Section 6.5 shows examples of the effect on the hazard for these two alternatives. Developing a directivity model that is consistent with the median and standard deviation of the GMPEs remains an area of research.

The directivity sensitivity studies in this report that used the Watson-Lamprey model were for a period of 2 seconds. At this period, the reduction to the standard deviation in the Watson-Lamprey model is zero. Therefore, the conclusions from the hazard sensitivity for directivity are not affected by the approach of using a reduction to the standard deviation before adding the directivity effects. This Appendix B - PPRP Closure Letter Page B-7

Enclosure 1 PG&E Letter DCL-15-035 Southwestern United States Appendix c 18 18 Ground Motion Characterization SSHAC Level 3 Page of TECHNICAL REPORT- Rev. 2 remains an issue for periods longer than 3 seconds, but the Watson-Lamprey model is not applied in the final GMC model.

At a period of 3 seconds, using either approach leads to a small effect on the hazard at the 1E-4 hazard level as shown in Section 6.5. The directivity effect is primarily a standard deviation effect. If the directivity effect is applied to the full standard deviation (without reductionL then there is a potential increase of 2% to 8% for the ground motion at the 1E-4 to 1E-6 hazard level forT = 3 seconds. This increase reflects the effect of the increased standard deviation. The range of total standard deviation models developed in Chapter 13 of this report for a period ofT= 2 seconds leads to a broad range (15%

to 25%) for 1E-4 to 1E-6, as shown in the hazard sensitivity results in Section 14. The same range of epistemic uncertainty will apply forT= 3 seconds. The Tl Team agrees that implementation of directivity into ground-motion models needs further research and that there is uncertainty in the effect of directivity on the total standard deviation, but, given that the potential range of the directivity effects is well within the range captured by the epistemic uncertainty in the total sigma logic tree, the Tl Team judges that total sigma logic tree adequately captures the potential range of the standard deviation including directivity effects. The limitation noted by the PPRP does not significantly affect the range of the standard deviation of the ground-motion model for application to DCPP.

Appendix B- PPRP Closure Letter Page B-8

Enclosure 2 PG&E Letter DCL-15-035 Regulatory Commitments PG&E is making the following regulatory commitment in this submittal:

Commitment Due Date PG&E will submit the resolution of the PPRP identified To be determined request as soon as it is completed.

In this submittal, Pacific Gas and Electric Company (PG&E) is revising the regulatory commitment made in PG&E Letter DCL-13-044, "Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding the Seismic Aspects of Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident," dated April 29, 2013.

PG&E committed to follow the guidance provided in NEI letter, "Proposed Path Forward for NTTF Recommendation 2.1: Seismic Reevaluations," dated April 9, 2013, with two clarifications. The guidance provided in the NEI letter was to utilize the Electric Power Research Institute Report No. 1025287, "Seismic Evaluation Guidance: Screening, Prioritization, and Implementation Details (SPID) for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1:

Seismic," dated November 2012 for the performance of the seismic reevaluations.

This commitment indicated that PG&E will perform the ground motion response spectrum comparison. PG&E's interim evaluation in preparation for the seismic probabilistic risk assessment (SPRA), as described in Enclosure 1, provides reasonable assurance that it is safe to operate DCPP while the updated/upgraded SPRA is being developed. As a result, performance of an expedited seismic evaluation process is not necessary.