View source for NL-22-0590, Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Exten

{{Adams
| number = ML22230C465
| issue date = 08/18/2022
| title = Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Exten
| author name = Gayheart C
| author affiliation = Southern Nuclear Operating Co, Inc
| addressee name = 
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000321, 05000366
| license number = 
| contact person = 
| case reference number = NL-22-0590
| document type = Letter type:NL, Response to Request for Additional Information (RAI)
| page count = 62
| project = 
| stage = Response to RAI
}}

=Text=
{{#Wiki_filter:Cheryl A. Gayheart          3535 Colonnade Parkway Regulatory Affairs Director Birmingham, AL 35243 205 992 5316 tel 205 992 7601 fax cagayhea@southernco.com August 18, 2022 Docket Nos.: 50-321                                                                     NL-22-0590 50-366                                                                 10 CFR 50.90 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Edwin I. Hatch Nuclear Plant - Units 1 and 2 Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, "Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b" Ladies and Gentlemen:
On October 26, 2021 [ADAMS Accession Number ML21300A153] and supplemented on April 29, 2022 [ML22119A144], pursuant to the provisions of Section 50.90 of Title 10 of the Code of Federal Regulations, Southern Nuclear Operating Company (SNC) requested amendments to Edwin I. Hatch Nuclear Plant, Units 1 and 2 (HNP) renewed facility operating licenses DPR-57 and NPF-5, respectively. The proposed amendment requested U.S. Nuclear Regulatory Commission (NRC) approval to modify Technical Specifications (TS) requirements to permit the use of Risk Informed Completion Times in accordance with TSTF-505, Revision 2, "Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b" [ML18183A493].
As part of their review of the license amendment request (LAR), NRC Staff transmitted requests for additional information (RAIs) on May 20, 2022 [ML22140A119] and June 6, 2022
[ML22157A354].
The Attachment to this letter provides responses to the RAIs referenced above.
SNC requests the same approval and implementation schedule as requested in its original application [ML21300A153]. The conclusions of the No Significant Hazards Consideration Determination and Environmental Consideration contained in the original application have been reviewed and are unaffected by this supplement.
In accordance with 10 CFR 50.91, SNC is notifying the State of Georgia of this RAI response by transmitting a copy of this letter, with attachment, to the designated State Official.
This letter contains no regulatory commitments. If you have any questions, please contact Amy Chamberlain at 205.992.6361.

U. S. Nuclear Regulatory Commission NL-22-0590 Page 2 I declare under penalty of perjury that the foregoing is true and correct. Executed on the 18th day of August 2022.
Respectfully submitted, C. A. Gayheart Director, Regulatory Affairs Southern Nuclear Operating Company CAG/ACC

==Attachment:==
SNC Response to NRC Request for Additional Information cc:     Regional Administrator, Region ll NRR Project Manager - Hatch Senior Resident Inspector - Hatch Director, Environmental Protection Division - State of Georgia RType: CHA02.004

Edwin I. Hatch Nuclear Plant - Units 1 and 2 Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, "Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b" NL-22-0590 Attachment SNC Response to NRC Request for Additional Information

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information SNC Response to NRC Request for Additional Information Nuclear Regulatory Commission (NRC) Staff transmitted requests for additional information (RAIs) via emails dated May 20, 2022 [ML22140A119] and June 6, 2022 [ML22157A354]. The RAIs were regarding SNCs license amendment request (LAR) for Hatch Nuclear Plant (HNP)
Units 1 and 2 to adopt Technical Specifications Task Force (TSTF) traveler TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b dated October 26, 2021 [ML21300A153]. The NRC Staffs RAIs are below; SNCs responses are provided following each RAI.
Probabilistic Risk Assessment Licensing Branch C (APLC) RAI Questions APLC-RAI Impact of Portable FLEX Equipment on Seismic Penalty The NRC memorandum dated May 30, 2017, Assessment of the Nuclear Energy Institute
[NEI] 16-06, Crediting Mitigating Strategies in Risk-Informed Decision Making, Guidance for Risk-Informed Changes to Plants Licensing Basis (ADAMS Accession No. ML17031A269),
provides the NRC staffs assessment of challenges to incorporating FLEX equipment and strategies into a probabilistic risk assessment (PRA) model in support of risk-informed decision-making in accordance with the guidance of Regulatory Guide (RG) 1.200, Revision 2 (ADAMS Accession No. ML090410014). With regards to equipment failure probability, in the memorandum dated May 30, 2017, the NRC staff concludes (Conclusion 8):
The uncertainty associated with failure rates of portable equipment should be considered in the PRA models consistent with the American Society of Mechanical Engineers/American Nuclear Society (ASME/ANS) PRA Standard as endorsed by RG 1.200. Risk-informed applications should address whether and how these uncertainties are evaluated.
With regards to human reliability analysis (HRA), NEI 16-06, Crediting Mitigating Strategies in Risk-Informed Decision Making, dated August 26, 2016 (ADAMS Accession No. ML16286A297), Section 7.5 recognizes that the current HRA methods do not translate directly to human actions required for implementing mitigating strategies. Sections 7.5.4 and 7.5.5 of NEI 16-06 describe such actions to which the current HRA methods cannot be directly applied, such as debris removal, transportation of portable equipment, installation of equipment at a staging location, routing of cables and hoses; and those complex actions that require many steps over an extended period, multiple personnel and locations, evolving command and control, and extended time delays. In the memorandum dated May 30, 2017, the NRC staff concludes (Conclusion 11):
Until gaps in the human reliability analysis methodologies are addressed by improved industry guidance, [Human Error Probabilities] HEPs associated with actions for which the existing approaches are not explicitly applicable, such as actions described in Sections 7.5.4 and 7.5.5 of NEI 16-06, along with assumptions and assessments, should be submitted to NRC for review.
Section 6 of Enclosure 2 to the LAR dated October 26, 2021, states that while Internal Events, Internal Flooding, and Fire PRA models credit only permanently installed FLEX equipment, portable FLEX equipment was credited in the Hatch Seismic PRA (SPRA) model. The Hatch SPRA is not directly used in the risk-informed completion time (RICT) program, but it is used to A-1

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information provide selected input into the calculation of the seismic core damage frequency (SCDF) and seismic large early release frequency (SLERF) penalty. It is unclear to the NRC staff how much of an impact the portable FLEX equipment would have on the evaluation of the SCDF and SLERF penalties. During the regulatory audit (ADAMS Accession No. ML21309A000) held on April 5 - 7, 2022, the licensee provided information on a FLEX sensitivity study for Hatch, Unit 1, that set the failure rates for portable FLEX equipment at 0.1/year and appeared to demonstrate that the uncertainty associated with the portable FLEX equipment does not significantly impact the bounding seismic penalty values. However, no information on a sensitivity study for Hatch, Unit 2, was provided nor were the base failure rates for the portable FLEX equipment. This information is needed to determine the overall impact of this source of uncertainty for this application.
Therefore, provide information on sensitivity studies for Hatch, Units 1 and 2, that address the impact of the portable FLEX equipment credited in the Hatch SPRA on the calculated SCDF and SLERF penalty values. Include the portable FLEX failure rates in both the base and sensitivity cases.
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Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information SNC Response to APLC-RAI Impact of Portable FLEX Equipment on Seismic Penalty The portable FLEX equipment credited in the Hatch Nuclear Plant (HNP) SPRA has no direct impact on the calculated SCDF penalty. As discussed in the HNP RICT LAR (ML21300A153),
the approach taken for the estimation of the SCDF penalty value is a mathematical convolution calculation of the current HNP seismic hazard curve with an estimate of the HNP plant-level seismic fragility. The assumed limiting plant level seismic capacity used in the Hatch seismic penalty calculation has a high confidence of low probability of failure (HCLPF) value of 0.30g peak ground acceleration (PGA) based on the HNP Individual Plant Examination of External Events (IPEEE) seismic analysis as documented in the HNP RICT LAR. The portable FLEX equipment credited in the SPRA has no impact on the plant-level HCLPF value based on the IPEEE. Therefore, the portable FLEX equipment credited in the Hatch SPRA has no impact on the calculated SCDF penalty. In addition, the portable FLEX equipment credited in the Hatch SPRA has no adverse impact on the SLERF penalty value as discussed in the following sections.
Table 1-1 lists the basic events for portable FLEX equipment credited in the Hatch SPRA Model of Record (MOR) including their basic event IDs, basic event descriptions, and nominal failure probabilities. For selected sensitivity cases, all of the portable FLEX equipment in Table 1-1 are not credited (i.e., set to TRUE) in order to calculate the impact on SCDF and SLERF.
Table 1-2 provides the SCDF and SLERF results for Unit 1 and Unit 2 for various cases. The main SPRA model (i.e., Case 1) used for the SPRA results comparison was described the Hatch Diesel Generator (DG) Liner LAR (ML20213C715), but also incorporates the various enhancements to the Flag and Recovery files as identified in the responses to RAIs 3a and 3b.
Some of the conservatisms associated with the SPRA model from the DG Liner LAR include, but are not limited to, the following:
: 1. Due to computation limitations and the computational time required to quantify hazard intervals %G12 (1.2g to <1.5g), %G13 (1.5g to <2g), and %G14 (>2g), the Unit 1 and Unit 2 fault trees have been modified so that these hazard bins are modeled to lead directly to CDF and LERF (i.e., Incremental Conditional Core Damage Probability (CCDP) and Conditional Large Early Release Probability (CLERP) equal to 1.0). This treatment is conservative; however, these hazard bins have high CCDPs and CLERPs and are not top contributors to the seismic results in the MORs, so this change has only a small impact on the Incremental CCDP (ICCDP) and Incremental CLERP (ICLERP) results for the DG Liner LAR risk informed application.
: 2. In order to reduce the computation time for the seismic PRA quantification, the Electric Power Research Institute (EPRI) ACUBE software was not used. Use of the Factored Minimum Cut Upper Bound (FMCUB) approach provides a slightly higher calculated CDF and LERF compared to use of ACUBE. However, the difference is identified to be small and did not adversely impact the ICCDP and ICLERP results for DG Liner LAR risk informed application.
Although the conservatisms identified above did not adversely impact the ICCDP and ICLERP results for the EDG CT risk informed application, the conservatisms resulted in a significant perceived increase in the base SCDF, base SLERF, and base SCLERP.
Table 1-2 provides the results for the following cases:
: 1. Case 1: Credit portable FLEX equipment. This is the nominal SPRA model (i.e., no DG Out of Service (OOS)) developed for the Hatch DG Liner LAR (ML20213C715), but also A-3

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information incorporates the various enhancements to the Flag and Recovery files as identified in the responses to RAIs 3a and 3b.
: 2. Case 2: Same as Case 1 but no credit for portable FLEX equipment.
: 3. Case 3: SPRA Model of Record (MOR) as documented in the Hatch RICT LAR.
: 4. Case 4: RICT seismic CDF and LERF penalty values as documented in the Hatch RICT LAR (same values apply to both Units 1 and 2).
Case 1a, with credit for portable FLEX equipment, shows that the Unit 1 SCDF and SLERF are 8.89E-07/yr and 2.32E-07/yr, respectively. Case 2a, which is the same as Case 1a except no credit for portable FLEX equipment (i.e., portable FLEX basic events set to TRUE), shows that the Unit 1 SCDF increases nearly 40% to 1.23E-06/yr, but there is a negligible increase in SLERF. The Case 2a SCDF of 1.23E-06/yr is slightly higher than the seismic penalty SCDF of 1.18E-06/yr from the Hatch RICT LAR shown in Case 4a. However, Case 2a is originally based on the SPRA model used for the DG Liner LAR , which incorporated conservatisms compared to the Hatch Seismic PRA MOR shown in Case 3a (H-RIE-SEIS-U00-001-002). If the SCDF of 6.8E-07/yr from the Hatch Unit 1 SPRA MOR (Case 3a) is also estimated to increase by approximately 40% when portable FLEX equipment is not credited, the SCDF would remain below the seismic penalty SCDF of 1.18E-06/yr. Therefore, the seismic penalty of 1.18E-06/yr for SCDF from the Hatch RICT LAR is evaluated to remain appropriate even when considering no credit for portable FLEX equipment. The Unit 2 results in Table 1-2 support a similar conclusion.
In addition, Table 1-2 supports that all SLERF cases remain below the seismic penalty of 2.95E-07/yr (i.e., Case 4a) for SLERF from the Hatch RICT LAR. Although Case 1b shows a Seismic Conditional Large Early Release Probability (SCLERP) of 0.31 for Unit 2, which is higher than the base SCLERP of 0.25 from the Hatch RICT LAR, Case 1b is based on the SPRA model used for the DG Liner LAR, which included conservatisms that increased the SLERF and associated SCLERP.
CONCLUSION The results in Table 1-2 support that the portable FLEX equipment credited in the Hatch SPRA has no impact on the calculated SCDF and SLERF penalty values in the Hatch RICT LAR.
Nevertheless, in order to address any remaining uncertainty associated with the seismic penalty and its use for the RICT program, the SCLERP for calculating the seismic LERF penalty will be set at 0.31 using the highest value shown for Case 1b in Table 1-2, which is based on the conservative SPRA model used in the Hatch DG Liner LAR.
For the Hatch RICT LAR, the seismic CDF penalty will remain at 1.18E-06/yr. However, the seismic LERF penalty will be increased from 2.95E-07/yr to 3.66E-07/yr (i.e., 1.18E-06/yr
* 0.31= 3.66E-07/yr).
Use of the seismic penalty for RICT, combined with showing that the SCLERP, and thus the seismic LERF penalty, decreases with FLEX credit, addresses uncertainty with the FLEX data.
Although the nominal probabilities for the portable FLEX equipment do not change the insights for the impact of FLEX for the RICT program, they are provided in Table 1-1.
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Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 1-1 Portable FLEX Equipment Credited in Hatch SPRA Model of Record (MOR)
Sensitivity Nominal Basic Event ID                Basic Event Description                          Case Probability Probability CC-FLEX-DGS-1         1/3, DGSS-FLEX-DG-A FAILS TO START           4.7E-03     Set to TRUE 2/3, DGSS-FLEX-DG-A DGSS-FLEX-DG-B FAIL TO CC-FLEX-DGS-2                                                      1.25E-05    Set to TRUE START 2/3, DGSS-FLEX-DG-A DGSS-FLEX-DG-C FAIL TO CC-FLEX-DGS-3                                                      1.25E-05    Set to TRUE START 3/3, DGSS-FLEX-DG-A DGSS-FLEX-DG-B DGSS-CC-FLEX-DGS-4                                                      4.28E-06    Set to TRUE FLEX-DG-C FAIL TO START CC-FLEX-DGS-5         1/3, DGSS-FLEX-DG-B FAIL TO START            4.7E-03     Set to TRUE 2/3, DGSS-FLEX-DG-B DGSS-FLEX-DG-C FAIL TO CC-FLEX-DGS-6                                                      1.25E-05    Set to TRUE START CC-FLEX-DGS-7         1/3, DGSS-FLEX-DG-C FAILS TO START           4.7E-03     Set to TRUE CC-FLEX-DGS-8         1/3, DGLR-FLEX-DG-A FAILS TO RUN FOR 14 HRS  9.74E-03    Set to TRUE 2/3, DGLR-FLEX-DG-A DGLR-FLEX-DG-B FAIL TO CC-FLEX-DGS-9                                                      3.14E-05    Set to TRUE RUN FOR 14 HRS 2/3, DGLR-FLEX-DG-A DGLR-FLEX-DG-C FAIL TO CC-FLEX-DGS-10                                                     3.14E-05    Set to TRUE RUN FOR 14 HRS 3/3, DGLR-FLEX-DG-A DGLR-FLEX-DG-B DGLR-CC-FLEX-DGS-11                                                     1.04E-05    Set to TRUE FLEX-DG-C FAIL TO RUN FOR 14 HRS CC-FLEX-DGS-12        1/3, DGLR-FLEX-DG-C FAILS TO RUN FOR 14 HRS  9.74E-03    Set to TRUE 2/3, DGLR-FLEX-DG-B DGLR-FLEX-DG-C FAIL TO CC-FLEX-DGS-13                                                     3.14E-05    Set to TRUE RUN FOR 14 HRS CC-FLEX-DGS-14        1/3, DGLR-FLEX-DG-B FAILS TO RUN FOR 14 HRS  9.74E-03    Set to TRUE CC-FLEXPORTPUMP-1     1/2, DPFS2FLEXPORTPUMPA FAILS TO START       1.85E-03    Set to TRUE CC-FLEXPORTPUMP-2     1/2, DPFS1FLEXPORTPUMPB FAILS TO START       1.85E-03    Set to TRUE 2/2, DPFS1FLEXPORTPUMPA CC-FLEXPORTPUMP-3                                                  1.23E-04    Set to TRUE DPFS1FLEXPORTPUMPB FAIL TO START 1/2, DPFR1FLEXPORTPUMPA FAILS TO RUN 14 CC-FLEXPORTPUMP-4                                                  9.15E-04    Set to TRUE HRS 1/2, DPFR1FLEXPORTPUMPB FAILS TO RUN 14 CC-FLEXPORTPUMP-5                                                  9.15E-04    Set to TRUE HRS 2/2, DPFR1FLEXPORTPUMPA CC-FLEXPORTPUMP-6                                                  3.3E-05     Set to TRUE DPFR1FLEXPORTPUMPB FAIL TO RUN 14 HRS A-5

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 1-2 Seismic PRA Results to Compare Impact of Crediting Portable FLEX Equipment Hatch Unit 1 Seismic PRA Results Case                                                           LERF Description               CDF (/yr)          SCLERP No.                                                            (/yr)
With credit for portable FLEX equipment.
(Nominal SPRA model with enhancements Case 1a                                              8.89E-07  2.32E-07 0.26 to Flag and Recovery files consistent with response to RAI 3a and 3b)
Same as Case 1 but no credit for portable Case 2a                                              1.23E-06  2.32E-07 0.19 FLEX equipment SPRA MOR (with credit for portable FLEX Case 3a                                              6.8E-07   1.4E-07  0.21 equipment) documented in RICT LAR Case 4a   Seismic Penalty documented in RICT LAR     1.18E-06  2.95E-07 0.25 Hatch Unit 2 Seismic PRA Results Case                                                           LERF Description               CDF (/yr)          SCLERP No.                                                            (/yr)
With credit for Portable FLEX equipment.
(Nominal SPRA model with enhancements Case 1b                                              8.21E-07  2.53E-07 0.31 to Flag and Recovery files consistent with response to RAI 3a and 3b)
Same as Case 1 but no credit for Portable Case 2b                                              1.10E-06  2.55E-07 0.23 FLEX equipment SPRA MOR (with credit for Portable FLEX Case 3b                                              5.6E-07   1.4E-07  0.25 equipment) documented in RICT LAR Case 4b   Seismic Penalty documented in RICT LAR     1.18E-06  2.95E-07 0.25 A-6

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information APLC-RAI Tornado Missiles Section 2.3.1, Item 7, of NEI 06-09 (ADAMS Accession No. ML122860402) states that the impact of other external events risk shall be addressed in the RMTS [risk-managed technical specifications] program, and explains that one method to do this is by documenting, prior to the RMTS program, that the external events that are not modeled in the PRA are not significant contributors to configuration risk. The NRC staffs safety evaluation for NEI 06-09 (ADAMS Accession No. ML071200238) states that [o]ther external events are also treated quantitatively, unless it is demonstrated that these risk sources are insignificant contributors to -configuration specific risk.
Table E4-4 of Enclosure 4 to the LAR dated October 26, 2021, indicates that the -tornado generated missile hazard is screened based on criteria C1 (Event damage potential is <
events for which plant is designed) of Table E4-5. Section 3 of Enclosure 4 to the LAR dated October 26, 2021, indicates that two nonconformances were identified, with one being corrected with a plant modification and the other, associated with service water systems, was evaluated and screened. However, the NRC staff reviewed a document, Plant Hatch Tornado Missile Project Summary Report [SNC826314], made available on the audit portal, which states that a Tornado Missile Risk Evaluation (TMRE) will need to be performed to conservatively estimate the risk of the remaining unprotected structures, systems, and components (SSCs) from tornado-generated missiles. The NRC staff notes that this risk appears to be related to -beyond design-basis events and that no TMRE documentation was provided in the application process.
During the regulatory audit (ADAMS Accession No. ML21309A000) held on April 5 - 7, 2022, the licensee indicated that the TMRE has not been performed and that there are no current plans to perform the analysis since no non-conformances exist in the plant. The NRC staff notes that the LAR dated October 26, 2021, provides the C1 criterion (corresponding to the plant design basis) for screening tornadoes and associated missiles. However, the information provided in the LAR dated October 26, 2021, appears to address beyond-design-basis tornado missiles risk and the licensee indicated during the audit that it will further examine the screening criteria that will cover beyond-design-basis tornado missiles.
Therefore, provide updated screening criteria for the tornado missiles hazard at Hatch, Units 1 and 2. Include, in the response, justification if the screening criteria are sufficient and adequate for this hazard.
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Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information SNC Response to APLC-RAI Tornado Missiles The HNP design and licensing bases do not include the requirement for protection against vertical missiles. Many of the SSCs potentially vulnerable to damage from vertical missiles were determined to have adequate protection. A set of SSCs was not evaluated for protection against vertical missiles; and these are the subject of the beyond design basis tornado missile risk associated with screening the tornado missile hazard. These SSCs are shown to be either protected (and thus supporting screening Criterion C1) or evaluated for risk impact (to support screening Criterion PS3)[1].
Appendix BB of Plant Hatch Tornado Missile Project Summary Report [SNC826314] provides a list of potentially vulnerable targets to vertical missiles; a few targets (IDs 9, 19, 30-31, and 35-36) have subsequently been evaluated as not vulnerable. The remaining SSCs are evaluated to determine their vulnerability to HNPs design basis missiles traveling in the vertical direction. SSCs which can be shown to be protected against or not damaged by such missiles are considered screened within the context of Criterion C1 of the HNP LAR Table E4-5. SSCs that cannot be shown to be protected against HNP design basis missiles traveling vertically are assessed probabilistically and screened using Criterion PS3 (i.e., EXT-C1, Criterion B) of HNP RICT LAR Table E4-5.
The evaluation and screening process is documented in SNC Calculation PRA-BC-H-22-004; the method and results are summarized here.
Screening with Criterion C1 Table 1 provides the list of SSCs vulnerable to vertical missiles. It is a subset of the SSCs in Appendix BB of SNC826314. Table 1 provides the results of the deterministic screening that was performed. Six sets of SSCs could not be screened using Criterion C1; they are again listed in Table 2.
The general methods used to screen SSCs potentially vulnerable to vertical missiles with respect to Criterion C1 are:
: a. Design basis missiles travelling vertically do not damage safety-related (SR) components. The HNP design basis tornado missiles are:
: 1) wood plank (4" x 12" x 12 ft. long, traveling at 300 mph) and
: 2) automobile (4000 lbs, travelling at 50 mph).
Per RG 1.76, Revision 1, the velocities of vertical missiles are defined in this assessment to be 67% of the maximum horizontal missile velocity.
: b. Damage to SR component has no or minimal impact on plant safe shutdown from at-power. This may be shown through qualitative or semi-quantitative arguments, which may rely upon factors such as: (a) more realistic success criteria, such as that used in the HNP Full Power Internal Events (FPIE); (b) redundancy and diversity of SSCs that can perform the same safety function; and/or (c) ruggedness of the SSC.
[1]
Screening Criteria are from Table E4-5 in the HNP TSTF-505 LAR (ML21300A153).
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Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 1 SSCs Potentially Vulnerable to Vertical Missiles From Table 3-1 of CALC PRA-BC-H-22-004 ID (1)      Description            Screen      Comments with C1 1-8         CST Level Switches     Yes         The switches and associated conduits are small for HPCI/RCIC swap                 targets, they are redundant, must fail in the actuated to Torus                           position, and are diverse to suppression pool high level actuation.
10          1N71F201               Yes         Valve is a relatively small target but in an uncovered valve pit. The valve only needs to open if the normally open (and protected) valve transfers closed. This is negligible risk.
11-14,      PSW TB Isolation       Yes         Valves are protected by grating that will stop design 25, and    Valves, except Unit 2              basis missiles travelling vertically. Hatches in grating 27          Division 2                         may not stop missiles, however the hatch opening is small, consists of (thinner) grating, and does not expose the valve operators to missiles. The pipes and mechanical portions of the valve are robust and are unlikely to be damaged to the point of failing to perform their function.
26 and 28   Unit 2 Division 2      No          Valves are protected by grating that will stop design PSW TB Isolation                   basis missiles travelling vertically. However, a thinner Valves                             hatch grating may result in a missile penetrating the hatch and potentially impacting both operators or cables for 2P41F316B and 2P41F316D. These valves must close to isolate the TB to allow adequate PSW flow to SR loads (including the EDGs). Valve failure could result in one division of PSW failing.
15-18,      PSW Isolation Valves   Yes         Valves are protected by grating that will stop design 21-24      to EDGs and RB                     basis missiles travelling vertically. Hatches in grating PSW Isolation Valves               may not stop missiles, however the hatch opening is to RB                              small, consists of (thinner) grating. Valves do not need to change position;. the pipes and mechanical portions of the valve are robust and are unlikely to be damaged to the point of failing to perform their function.
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Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 1 (continued)
SSCs Potentially Vulnerable to Vertical Missiles From Table 3-1 of CALC PRA-BC-H-22-004 ID (1)         Description           Screen      Comments with C1 20             2N71F013              Yes         Valve is a relatively small target but the grating over the valve pit is thin. The valve only needs to open if the normally open (and protected) valve transfers closed. This is negligible risk.
29             U2 N2 Tank            No          Large surface area and supports both units. Not able to screen deterministically.
32-34          Intake Structure      No          Grating protects against missiles, but vent hoods Fans (on Roof)                    could be crushed. 1 of 3 fans required.
37-51          EDG FO Storage        No          FO transfer pumps are vulnerable to missile strike Tanks and Transfer                through relatively thin manhole cover.
Pumps 53a            EDG Battery Room      Yes         Grating protects against missiles and ventilation not Fans                              needed for success 53b            EDG Switchgear        Yes         Grating protects against missiles and ventilation not Room Fans                         needed for success 53c            EDG Oil Storage       Yes         Grating protects against missiles and ventilation not Room Fans                         needed for success 53d            EDG Room Main         No          Grating prevents missile penetration; however, Exhaust Fans                      ventilation hoods can be crushed. 1 of 2 fans required for success.
53e            EDG Exhaust Piping    No          Muffler remains functional following missile strike; and Muffler                       however, exhaust pipes have not basis calculations for functionality on tornado missile strike.
Notes to Table 1:
: 1. ID is from SNC926314-01, Appendix BB.
                                                     
Screening with Criterion PS3 (EXT-C1, Criterion B)
SSCs that cannot be shown to be protected against HNP design basis missiles traveling vertically are assessed probabilistically and screened using Criterion PS3 (EXT-C1, Criterion B) of HNP RICT LAR Table E4-5. For screening tornado missiles, PS3 [EXT-C1, Criterion B]
requires the design basis tornado hazard frequency be less than 1E-5/yr. Consistent with , Section 3 of the HNP RICT LAR (ML21300A153), NUREG/CR-4461, Rev 2 A - 10

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information (ML070810400) is used to determine the tornado hazard at HNP. F-Scale wind speeds from Table 6-1 of NUREG/CR-4461, Rev 2 are provided in Table 4-1. These are used to determine a conservative hazard frequency, based on the guidance in NEI 17-02 (ML17268A036). For the HNP 300 mph tornado wind speed, frequency = 4.55E-8/yr. This hazard frequency is significantly less than 1E-5/yr, as required by Screening Criterion PS3.
CCDP is calculated using a modified version of the HNP average maintenance FPIE PRA model. The FPIE PRA is adjusted to produce the following configuration for quantification of the CCDPs used in this assessment:
x   Dual unit loss of offsite power (LOSP) initiated sequences only (all other initiators removed from the model quantification) x   Offsite AC power recovery disabled (i.e., no offsite AC recovery credited) x   SSCs protected from tornado missiles are not affected (i.e., no tornado missile induced failure modes added into the PRA model for these SSCs) x   Tornado missile failure basic events are added to the fault trees for all the SSCs not screened using Criterion C1 (i.e., those SSCs in Table 2). Basic event failure probabilities for tornado missile failures are also provided in Table 2.
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Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 2 SSCs Considered in CCDP Calculation From Table 3-1 of CALC PRA-BC-H-22-004 ID(1)             Description             Comments                                 Tornado Missile Failure Probability (2) 26 and 28         Unit 2 Division 2       Failure probability of both valves       7.4E-3 Plant Service           failing from single missile hit Water (PSW)
Turbine Building (TB) Isolation Valves 29                Unit 2 N2 Tank          Tank is large and roof is engineered     1.0 sheet metal. No credit taken for the tank, conservatively set to 1.0 32-34             Intake Structure        Individual fan hood crushing             Single fan: 2.9E-2 Fans (on Roof)          probabilities (one for each of three fan Double: 1.5E-2 hoods) and adjacent fan hood correlated crushing (A/B and B/C only).
37-51             Emergency Diesel        Assume strike on manhole cover fails     5.3E-3 (each tank)
Generator (EDG)         both transfer pumps. Fuel oil transfer Fuel Oil (FO)           is not needed for several hours and Storage Tanks           all pumps can be cross-tied to any and Transfer            tank, but conservatively not credited.
Pumps                   Manhole cover is 1/8. Included in DG failure probability for CCDP calculation.
53d               EDG Room Main           Grating prevents missile penetration;    1.2E-2 per fan hood Exhaust Fans            however, ventilation hoods can be crushed. 1 of 2 fans required for success.
53e               EDG Exhaust             Muffler remains functional following     2.2E-2 per EDG Piping and Muffler      missile strike; however, exhaust pipes have not basis calculations for functionality on tornado missile strike.
Notes to Table 2:
: 1. ID is from SNC926314-01, Appendix BB.
: 2. Tornado Missile Failure Probabilities calculated in PRA-BC-H-22-004 The CCDP results are provided below in Table 3.
A - 12

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3 - HNP Units 1 and 2 CCDPs From Table 4-2 of CALC PRA-BC-H-22-004 Unit       CCDP HNP1       2.17E-3 HNP2       2.37E-3 The CCDP for either unit is much less than the 0.1 Screening Criterion PS3 [EXT-C1, Criterion B], and thus tornado missiles are screened from HNP1 and HNP2.
A - 13

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information APLC-RAI (Revised Audit Question 12)
Section 2.3.1, Item 7, of Nuclear Energy Institute (NEI) 06-09, Risk Informed Technical Specifications Initiative 4b: Risk Managed Technical Specifications (RMTS), Revision 0-A, dated October 12, 2012 (ADAMS Accession No. ML122860402), states that the impact of other external events risk shall be addressed in the risk management technical specification (RMTS) program and explains that one method to do this is by performing a reasonable bounding analysis and applying it along with the internal events risk contribution in calculating the configuration risk and the associated RICT [Risk-Informed Completion Time]. The NRC staffs safety evaluation (SE) for NEI 06-09 states that Where PRA models are not available, conservative or bounding analyses may be performed to quantify the risk impact and support the calculation of the RICT.
In the license amendment request (LAR), the seismic penalty approach is used to quantify the risk impact and to support the RICT evaluation. Section 5 of Enclosure 4 to the LAR indicates that a seismic PRA (SPRA) for the Hatch plant was developed and that the Hatch SPRA was not directly used in the RICT program but provided input into the calculation for seismic core damage frequency (SCDF) and seismic large early release frequency (SLERF) penalty values.
The licensee compared the estimated SCDF penalty for the proposed RICT calculations against the point-estimate SCDF from the site-specific SPRA. In addition, the licensee used the SLERF to SCDF ratio from the site-specific SPRA to determine the SLERF penalty for use in the proposed RICT calculations.
The comparison of the estimated SCDF and SLERF penalties against the corresponding point-estimate mean values from the site-specific SPRA does not provide justification that the SCDF and SLERF penalty estimates are conservative. There is no upper bound on the change-in-risk calculation, and the change in risk can exceed the base SCDF and SLERF.
However, it appears to the NRC staff that the SPRA could provide the means to justify that the proposed SCDF and SLERF penalty estimates are conservative, consistent with the NRC staffs SE for NEI 06-09.
During the regulatory audit conducted on April 5 - 7, 2022, the licensee attempted to address this concern by referencing Table 3.5-1 and 3.5-2 in License Amendment Request to Revise the Required Actions of Technical Specifications 3.8.1, AC Sources - Operating, for One-Time Extension of Completion Time for Unit 1 and Swing Emergency Diesel Generators, dated July 31, 2020 (ADAMS Accession No. ML20213C715). However, the NRC staff identified potentially non-conservative Incremental Conditional Core Damage Probability (ICCDP) and Incremental Conditional Large Early Release Probability (ICLERP) values listed in Table 3.5-1 for the diesel generator (DG) 1C seismic hazard, as well as other cases for other PRAs. As a result of this inquiry, the licensee reviewed its calculations and identified errors involved in the modeling and provided reevaluated results for Hatch, Unit 1, DG 1C on the portal for the NRC staff to review.
To allow the NRC staff to better understand the effect of these changes on the RICT program, the licensee is requested to address the following:
: a. Briefly describe the modeling errors identified in the quantification results provided in Tables 3.5-1 and 3.5-2. Include in the response how each error was resolved across all hazards. Include identification of errors determined to impact the PRA models (i.e.,
internal events, internal floods, internal fire, seismic) and the real-time risk (RTR) model A - 14

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information being used to support the review of the TSTF-505 LAR and confirm the resolution has been incorporated into the models as applicable.
: b. For any changes to the PRA models identified in part(a) that are used to support the TSTF-505 LAR, provide detailed justification that there is no adverse impact on the RICT program. Ensure justification includes evaluation across all hazards and the affected Hatch, Units 2, DGs.
: c. Confirm if the Hatch SPRA core damage frequency (CDF) and large early release frequency (LERF) point estimates provided in the TSTF-505 LAR are affected by the aforementioned modeling errors; if so, update the affected values in Section 5 of Enclosure 4 to the TSTF-505 LAR.
: d. The NRC staff notes that information provided in Tables 3.5-1 and 3.5-2 indicates that the SCDF and SLERF penalty values proposed in the TSTF-505 LAR are conservative when compared to the change-in-risk calculations from the Hatch SPRA for all DGs, except for EDG 1C for Hatch, Unit 1. Provide updated Table 3.5-1 for DG 1C for Hatch, Unit 1, reflecting the resolution of the modeling errors. Also, confirm that any changes to the SPRA model identified in part (a) do not affect the conclusion regarding the conservatism of the SCDF and SLERF penalty values proposed in the TSTF-505 LAR.
A - 15

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information SNC Response to APLC-RAI (Revised Audit Question 12)
Response 3a When evaluating the results of the seismic model for the 1C emergency diesel system outages in Tables 3.5-1 and 3.5-2 of the Hatch DG Liner LAR, the NRC noted that the 1C DG OOS case evaluation resulted in a reduction in risk for the seismic hazard. Upon further investigation, SNC identified issues with the PRAQuant advanced tab settings, Flag file settings, and recovery file settings associated with the quantification of the various hazard groups for the DG Liner LAR.
Observations from the SNC investigation included the following:
: 1. In the U1 and U2 models, FLEX associated events set to a probability value in the flag files were not in the seismic cutsets. On further investigation, it was evident that the treatment of events set to 1.0 as TRUE described below, combined with the command
         **COMPRESS** 1 at the end of the seismic recovery file, were removing the events from the cutset so that a reviewer could not easily identify what was occurring.
: 2. Another cause of the seismic risk decrease with the 1C DG OOS case noted by the NRC was the incorrect selection of a seismic basic event for DG 1B availability and its use to represent the mode selector switch for supplying AC power to Unit 1 or Unit 2. The event in the seismic model represents the split fraction for the operator to align the swing diesel when the accident conditions are similar between the units and does not represent the alignment of the mode selector switch.
: 3. In the U1 and U2 internal events models, consequential recovery of AC power was in cutsets where recovery was not applicable.
The summary of the issues discussed above are provided in Table 3a-1. The issues were identified through comparing the base risk cutset with the DG OOS case and verifying the cutsets missing in the DG OOS case were due to events set to False in the flag file.
Tables 3a-2 through 3a-18 identify changes made to ensure the results were reasonable and all cutsets from base risk were in the DG OOS case for Unit 1, along with new cutsets containing an OOS DG event. Tables 3a-2 through 3a-18 compare the PRAQuant, Recovery rule and flag files from the original DG Liner LAR (i.e., left hand side of table) and updated evaluation (i.e.,
right hand side of table) to support this RAI response. The items changed are in red font, and the number on the side provides the line number in which change takes place.
PRAQuant and Recovery File Changes for Nominal Cases PRAQuant and Recovery file changes are provided for the following hazards (in the following order):
: 1. Fire PRAQuant (Table 3a-2) and Recovery (Table 3a-3) files
: 2. Internal Flood PRAQuant (Table 3a-4) and Recovery (Table 3a-5) files
: 3. Internal Events PRAQuant (Table 3a-6) and Recovery (Table 3a-7) files
: 4. Seismic CDF and LERF PRAQuant (Tables 3a-8 and 3a-9) and Recovery (Table 3a-10) files A - 16

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information PRAQuant, Flag, and Recovery File Changes for 1C EDG OOS Cases PRAQuant, Flag, and Recovery file changes are provided for the following hazards (in the following order):
: 1. Fire PRAQuant (Table 3a-11) and Recovery (Table 3a-12) files
: 2. Internal Flood PRAQuant (Table 3a-13) and Recovery (Table 3a-14) files
: 3. Internal Events PRAQuant (Table 3a-15) and Recovery (Table 3a-16) files
: 4. Seismic Flag (Tables 3a-17) and Recovery (Table 3a-18) files Conclusion The changes in the PRAQuant, Flag, and Recovery files are judged to result in relatively minor differences in the Unit 1 CDF and LERF results for both the nominal cases and the DG 1C OOS cases over all hazard groups. Similar changes were identified for both the Unit 2 nominal cases and the DG 2C OOS case over all hazard groups. The identified changes were entered into the SNC Corrective Action Program and will be tracked and integrated into the Hatch PRA model maintenance and update process.
Table 3a-1 Summary of Modeling Issues Identified for Hatch DG Liner LAR Software No. Issue                                              Resolution       Change Application The compression of events in the recovery rule file before                                       Add line near top of Changes to Fire, Recovery file for:
applying recovery to cutsets is Internal Flood, due to the Compress 1 1                                      Recovery File   Internal Events, statement at the end of the                                         **SET EVENTS and Seismic seismic recovery file. However,                                     UNKNOWN**
recovery files.
these events are PROB in the
* flag file.
Changes to Fire, PRAQuant passing events set                        Internal Flood,  Add line for:
using PROB to QRecover as                          and Internal 2   TRUE and triggering                PRAQuant        Events, consequential offsite power                        PRAQuant file    NoSendFailureList recovery in inapplicable cutsets.                  advanced         = True settings.
The location in the recovery rule                                   Add line near top of Changes to Fire, Recovery file for:
file for setting sequence flags to Internal Flood, TRUE and creating non-minimal 3                                      Recovery File   Internal Events,
        - erroneous results - cutsets and                                   **SET EVENTS and Seismic causing results to differ between                                   TRUE**
recovery files.
the base and DG OOS cutsets.                                        SEQ*
A - 17

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-1 (continued)
Summary of Modeling Issues Identified for Hatch DG Liner LAR Software No. Issue                                                  Resolution         Change Application Move recovery rules to be higher in the recovery file:
                                                                                 **CHANGEEVENT The location of the application-Changes to Fire,   S** +OPHE-REC-specific rule file for removing and Internal Flood,    PSW-F portion for applying recovery to cutsets 4                                        Recovery File     Internal Events,   Fire recovery file, relevant to offsite power and Seismic        and recovery and applying PSW recovery files.
recovery.
                                                                                 **RECOVERY**
DEL 0 portion for Internal Flood and Internal Events recovery file.
Use of an incorrect basic event                                           Remove line for:
to show that the 1B diesel is                          Changes to 5                                        Flag File aligned to Unit 1 for 1A and 1C                        Seismic flag file. FL-DG1BALIGN-diesels out of service.                                                   SPRA EQU .F.
A - 18

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Note: Tables 3a-2 through 3a-18 compare the PRAQuant, Recovery rule and flag files from the original DG Liner LAR (i.e., left hand side of table) and updated evaluation (i.e., right hand side of table) to support this RAI response. The items changed are in red font, and the number on the side provides the line number in which change takes place.
Table 3a-2 Identification of Changes in Fire PRA PRAQuant File for Nominal Cases 2                      <Model                   <>           2                    <Model FaultTreeFile                                             FaultTreeFile
                      ="..\H1_CBM_R                                             ="..\H1_CBM_R EV_8_IFL_ASM.                                             EV_8_IFL_ASM.
CAF"                                                      CAF" DatabaseFile=                                             DatabaseFile=
                      "..\H1_CBM_RE                                             "..\H1_CBM_RE V_8_ASM.rr"                                               V_8_ASM.rr" MasterFlagFil                                             MasterFlagFil e="..\H1_CBM_                                             e="..\H1_CBM_
REV_8_FLG_ABA                                             REV_8_FLG_ABA O_ASM.FLG"                                                O_ASM.FLG" CutsetFile="H                                             CutsetFile="H 1_CBM_REV_8_A                                             1_CBM_REV_8_A BAO\"                                                     BAO-PC\"
LogFile="Chan                                             LogFile="Chan gedCheckLog.t                                             gedCheckLog.t xt"                                                       xt" Initiators="%                                             Initiators="%
Intiators="%*                                             Intiators="%*
LocalFlags="%                                             LocalFlags="%
FLD*=False; %                                             FLD*=False; %
IE*=False; %G                                             IE*=False; %G
                      *=False"                                                  *=False" TrueEvent=".T                                             TrueEvent=".T FalseEvent=".                                             FalseEvent=".
F." />                                                    F." />
A - 19

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-2 (continued)
Identification of Changes in Fire PRA PRAQuant File for Nominal Cases 3                   <Options                          3                <Options ACUBECount="1                                      ACUBECount="1 000"                                               000" ACUBEEnabled=                                      ACUBEEnabled=
                   "false"                                            "false" ClearLog="tru                                      ClearLog="tru e"                                                 e" CompressAll="                                      CompressAll="
26"                                                26" CurrentQuanti                                      CurrentQuanti fier="Quant_F                                      fier="Quant_F TREX1901"                                          TRW6419" CutsetFormat=                                      CutsetFormat=
                   "2"                                                "2" DeleCurVal="t                                      DeleCurVal="t rue"                                               rue" ExpandMods="t                                      ExpandMods="t rue"                                               rue" FalseEvent=".                                      FalseEvent=".
F"                                                 F" MaxRecoveries                                      MaxRecoveries
                   ="6"                                               ="6" PruneBeforeFl                                      NoSendFailure ags="false"                                        List="True" RunMissing="f                                      PruneBeforeFl alse"                                              ags="false" SaveAll="fals                                      RunMissing="f e"                                                 alse" ShellWindowSt                                      SaveAll="fals ate="1"                                            e" Singlefile="f                                      ShellWindowSt alse"                                              ate="1" TrueEvent=".T                                      Singlefile="f
                   "                                                  alse" TruncateToZer                                      TrueEvent=".T o="False" />                                       "
TruncateToZer o="False" />
A - 20

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-3 Identification of Changes in Fire PRA Recovery File for Nominal Cases
                                            -+         3               **SET EVENTS UNKNOWN**
4               *
                                            -+         6               **SET EVENTS TRUE**
7               SEQ*
                                            -+         9               **SUBSUME**
10              **COMPRESS**
4
                                            -+         12              **CLEAR RECOVERY FLAGS**
13              **MAX RECOVERIES**
1 14              ;
15              ; add op action 16              ;
17              **CHANGEEVENT S** +OPHE-REC-PSW-F 18              %HF_1101J*
SEQ_SBO_28
                                                                       -OPHE* -CC-SW-1 19              **CHANGEEVENT S** +OPHE-REC-PSW-F 20              %HF_1101J*
SEQ_SBO_5
                                                                       -OPHE* -CC-SW-1
                                            -+         22              **SET EVENT PROBS**
23              OPHE-REC-PSW-F .05 A - 21

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-3 (continued)
Identification of Changes in Fire PRA Recovery File for Nominal Cases
                                            -+         25              **COMPRESS**
2 7                 **CLEAR                  +-
RECOVERY FLAGS**
9                 **SUBSUME**              +-
10                **COMPRESS**
30 2478              **CLEAR                  +-
RECOVERY FLAGS**
2479              **MAX RECOVERIES**
1 2480              ;
2481              ; add op action 2482              ;
2483              **CHANGEEVENT S** +OPHE-REC-PSW-F 2484              %HF_1101J*
SEQ_SBO_28
                   -OPHE* -CC-SW-1 2485              **CHANGEEVENT S** +OPHE-REC-PSW-F 2486              %HF_1101J*
SEQ_SBO_5
                   -OPHE* -CC-SW-1 2488              **SET EVENT              +-
PROBS**
2489              OPHE-REC-PSW-F .05 2492              SEQ_*                    +-
A - 22

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-4 Identification of Changes in Internal Flood PRA PRAQuant File for Nominal Cases 2                     <Model                <>        2                  <Model FaultTreeFile                                       FaultTreeFile
                    ="..\H1_CBM_R                                       ="..\H1_CBM_R EV_8_IFL_ASM.                                       EV_8_IFL_ASM.
CAF"                                                CAF" DatabaseFile=                                       DatabaseFile=
                    "..\H1_CBM_RE                                       "..\H1_CBM_RE V_8_ASM.rr"                                         V_8_ASM.rr" MasterFlagFil                                       MasterFlagFil e="..\H1_CBM_                                       e="..\H1_CBM_
REV_8_FLG_ABA                                       REV_8_FLG_ABA O_ASM.FLG"                                          O_ASM.FLG" CutsetFile="H                                       CutsetFile="H 1_CBM_REV_8_F                                       1_CBM_REV_8_F LOOD\"                                              LOOD-PC\"
LogFile="REV8                                       LogFile="REV8
                    -1TOP-IL-                                           -1TOP-IL-LOG.txt"                                            LOG.txt" Initiators="%                                       Initiators="%
Intiators="%*                                       Intiators="%*
LocalFlags="%                                       LocalFlags="%
HF*=False; %I                                       HF*=False; %I E*=False; %G*                                       E*=False; %G*
                    =False"                                             =False" TrueEvent=".T                                       TrueEvent=".T FalseEvent=".                                       FalseEvent=".
F." />                                              F." />
A - 23

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-4 (continued)
Identification of Changes in Internal Flood PRA PRAQuant File for Nominal Cases 3                     <Options                         3                 <Options ACUBECount="1                                       ACUBECount="1 000"                                                000" ACUBEEnabled=                                       ACUBEEnabled=
                    "false"                                             "false" ClearLog="tru                                       ClearLog="tru e"                                                  e" CompressAll="                                       CompressAll="
26"                                                 26" CurrentQuanti                                       CurrentQuanti fier="Quant_F                                       fier="Quant_F TREX64-SEIS"                                        TRW6419" CutsetFormat=                                       CutsetFormat=
                    "2"                                                 "2" DeleCurVal="t                                       DeleCurVal="t rue"                                                rue" ExpandMods="t                                       ExpandMods="t rue"                                                rue" FalseEvent=".                                       FalseEvent=".
F"                                                  F" MaxRecoveries                                       MaxRecoveries
                    ="6"                                                ="6" PruneBeforeFl                                       NoSendFailure ags="false"                                         List="True" RunMissing="f                                       PruneBeforeFl alse"                                               ags="false" SaveAll="fals                                       RunMissing="f e"                                                  alse" ShellWindowSt                                       SaveAll="fals ate="1"                                             e" Singlefile="f                                       ShellWindowSt alse"                                               ate="1" TrueEvent=".T                                       Singlefile="f
                    "                                                   alse" TruncateToZer                                       TrueEvent=".T o="False" />                                        "
TruncateToZer o="False" />
A - 24

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-5 Identification of Changes in Internal Flood PRA Recovery File for Nominal Cases
                                              -+       3                 **SET EVENTS UNKNOWN**
4                 *
                                              -+       6                 **SET EVENTS TRUE**
7                 SEQ_*
                                              -+       9                 **SUBSUME**
10                **COMPRESS**
4
                                              -+       12                **CLEAR RECOVERY FLAGS**
                                              -+       14                ;Remove illegitimate cutsets.
These cutsets have OSP recovery successful on the success branch of the sequence but no credit for OSP recovery on the failure branch
                                              -+       16                **RECOVERY**
DEL 0 17                SEQ_LOSP-2 SEQ_OSPREC OPHE*
18                SEQ_LOSP-5 SEQ_OSPREC OPHE*
A - 25

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-5 (continued)
Identification of Changes in Internal Flood PRA Recovery File for Nominal Cases
                                              -+        25               **SET EVENTS UNKNOWN**
26
* 10                  **COMPRESS**             <>        31               **COMPRESS**
30                                                  4
                                              -+        83               ;These cutsets conservativel y applied a 5 hour OSP recovery when 10 hours is warranted
                                              -+        85               **MAX RECOVERIES**
1 86               **RECOVERY**
NR-OSP-5to10H 0.523 87               SEQ_LOSP-9 CONSEQ-NR1-5H 88               SEQ_GT_10 CONSEQ-NR1-5H 89               SEQ_GT_3 CONSEQ-NR1-5H 90               SEQ_LOSP-13 CONSEQ-NR1-5H 91               SEQ_LOSP-16 CONSEQ-NR1-5H 92               SEQ_GT_16 CONSEQ-NR1-5H 93               SEQ_LOSP-22 CONSEQ-NR1-5H 94               SEQ_LOSP-19 CONSEQ-NR1-5H 95               SEQ_GT_22 CONSEQ-NR1-5H 96               SEQ_GT_19 CONSEQ-NR1-5H 97               SEQ_LOSP-9 ZNR-OSP-5H A - 26

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-5 (continued)
Identification of Changes in Internal Flood PRA Recovery File for Nominal Cases 98               SEQ_GT_10 ZNR-OSP-5H 99               SEQ_GT_3 ZNR-OSP-5H 100              SEQ_LOSP-13 ZNR-OSP-5H 101              SEQ_LOSP-16 ZNR-OSP-5H 102              SEQ_GT_16 ZNR-OSP-5H 103              SEQ_LOSP-22 ZNR-OSP-5H 104              SEQ_LOSP-19 ZNR-OSP-5H 105              SEQ_GT_22 ZNR-OSP-5H 106              SEQ_GT_19 ZNR-OSP-5H
                                              -+        108              **SUBSUME**
109              **COMPRESS**
4 A - 27

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-6 Identification of Changes in Internal Events PRA PRAQuant File for Nominal Cases 2                     <Model                <>        2                  <Model FaultTreeFile                                      FaultTreeFile
                     ="..\H1_CBM_R                                      ="..\H1_CBM_R EV_8_IFL_ASM.                                      EV_8_IFL_ASM.
CAF"                                               CAF" DatabaseFile=                                      DatabaseFile=
                     "..\H1_CBM_RE                                      "..\H1_CBM_RE V_8_ASM.rr"                                        V_8_ASM.rr" MasterFlagFil                                      MasterFlagFil e="..\H1_CBM_                                      e="..\H1_CBM_
REV_8_FLG_ABA                                      REV_8_FLG_ABA O_ASM.FLG"                                         O_ASM.FLG" CutsetFile="H                                      CutsetFile="H 1_CBM_REV_8_F                                      1_CBM_REV_8_F PIE\"                                              PIE-PC\"
LogFile="Rev8                                      LogFile="Rev8
                     -IE-Log.txt"                                       -IE-Log.txt" Initiators="%                                      Initiators="%
Intiators="%*                                      Intiators="%*
LocalFlags="%                                      LocalFlags="%
HF*=False; %F                                      HF*=False; %F LD*=False; %G                                      LD*=False; %G
                     *=False"                                           *=False" TrueEvent=".T                                      TrueEvent=".T FalseEvent=".                                      FalseEvent=".
F." />                                             F." />
A - 28

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-6 (continued)
Identification of Changes in Internal Events PRA PRAQuant File for Nominal Cases 3                     <Options                         3                 <Options ACUBECount="1                                      ACUBECount="1 000"                                               000" ACUBEEnabled=                                      ACUBEEnabled=
                     "false"                                            "false" ClearLog="tru                                      ClearLog="tru e"                                                 e" CompressAll="                                      CompressAll="
26"                                                26" CurrentQuanti                                      CurrentQuanti fier="Quant_F                                      fier="Quant_F TREX1901_X64_                                      TRW6419" WRAP"                                              CutsetFormat=
CutsetFormat=                                      "2" "2"                                                DeleCurVal="t DeleCurVal="t                                      rue" rue"                                               ExpandMods="t ExpandMods="t                                      rue" rue"                                               FalseEvent=".
FalseEvent=".                                      F" F"                                                 MaxRecoveries MaxRecoveries                                      ="6"
                     ="6"                                               NoOverridePro NoOverridePro                                      bs="false" bs="false"                                         NoSendFailure PruneBeforeFl                                      List="True" ags="false"                                        PruneBeforeFl RunMissing="f                                      ags="false" alse"                                              RunMissing="f SaveAll="fals                                      alse" e"                                                 SaveAll="fals ShellWindowSt                                      e" ate="1"                                            ShellWindowSt Singlefile="f                                      ate="1" alse"                                              Singlefile="f TrueEvent=".T                                      alse"
                     "                                                  TrueEvent=".T TruncateToZer                                      "
o="False" />                                       TruncateToZer o="False" />
A - 29

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-7 Identification of Changes in Internal Events PRA Recovery File for Nominal Cases
                                             -+        3                 **SET EVENTS UNKNOWN**
4                 *
                                             -+        6                 **SET EVENTS TRUE**
7                 SEQ_*
                                             -+        9                 **SUBSUME**
10                **COMPRESS**
4
                                             -+        12                **CLEAR RECOVERY FLAGS**
                                             -+        14                ;Remove illegitimate cutsets.
These cutsets have OSP recovery successful on the success branch of the sequence but no credit for OSP recovery on the failure branch
                                             -+        16                **RECOVERY**
DEL 0 17                SEQ_LOSP-2 SEQ_OSPREC OPHE*
18                SEQ_LOSP-5 SEQ_OSPREC OPHE*
A - 30

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-7 (continued)
Identification of Changes in Internal Events PRA Recovery File for Nominal Cases
                                             -+         23               **SET EVENTS UNKNOWN**
24
* 8                  **COMPRESS**             <>         28               **COMPRESS**
30                                                   4
                                             -+         33               **REPLACE EVENTS**
OPHEELAP-ALTPWR-X 1.0 34               OPHEELAP-ALTPWR OPHEELAP-ALTPR-FLAG
                                             -+         48               **COMPRESS**
2 26                 **REPLACE                <>         50 EVENTS**
OPHEELAP-ALTPWR-X 1.0 27                 OPHEELAP-                           51 ALTPWR OPHEELAP-ALTPR-FLAG
                                             -+         85               ;These cutsets conservativel y applied a 5 hour OSP recovery when 10 hours is warranted
                                             -+         87               **MAX RECOVERIES**
1 88               **RECOVERY**
NR-OSP-5to10H 0.523 A - 31

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-7 (continued)
Identification of Changes in Internal Events PRA Recovery File for Nominal Cases 89               SEQ_LOSP-9 CONSEQ-NR1-5H 90               SEQ_GT_10 CONSEQ-NR1-5H 91               SEQ_GT_3 CONSEQ-NR1-5H 92               SEQ_LOSP-13 CONSEQ-NR1-5H 93               SEQ_LOSP-16 CONSEQ-NR1-5H 94               SEQ_GT_16 CONSEQ-NR1-5H 95               SEQ_LOSP-22 CONSEQ-NR1-5H 96               SEQ_LOSP-19 CONSEQ-NR1-5H 97               SEQ_GT_22 CONSEQ-NR1-5H 98               SEQ_GT_19 CONSEQ-NR1-5H 99               SEQ_LOSP-9 ZNR-OSP-5H 100              SEQ_GT_10 ZNR-OSP-5H 101              SEQ_GT_3 ZNR-OSP-5H 102              SEQ_LOSP-13 ZNR-OSP-5H 103              SEQ_LOSP-16 ZNR-OSP-5H 104              SEQ_GT_16 ZNR-OSP-5H 105              SEQ_LOSP-22 ZNR-OSP-5H 106              SEQ_LOSP-19 ZNR-OSP-5H 107              SEQ_GT_22 ZNR-OSP-5H 108              SEQ_GT_19 ZNR-OSP-5H
                                             -+         110              **SUBSUME**
111              **COMPRESS**
4 A - 32

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-8 Identification of Changes in Seismic PRA CDF PRAQuant File for Nominal Cases 2                     <Model               <>         2                <Model FaultTreeFile                                    FaultTreeFile
                     ="H1_IxxS_REV                                    ="H1_IxxS_REV
_8_ASM.caf"                                      _8_ASM.caf" DatabaseFile=                                    DatabaseFile=
                     "H1_CBM_REV_8                                    "H1_CBM_REV_8
_ASM.rr"                                         _ASM.rr" RecoveryFile=                                    RecoveryFile=
                     "CBM_RECV_U12                                    "CBM_RECV_U12
_REV_8_SEISMI                                    _REV_8_SEISMI C.recv"                                          C.recv" MasterFlagFil                                    MasterFlagFil e="FRAGILITY.                                    e="FRAGILITY.
flg"                                             flg" CutsetFile="U                                    CutsetFile="U 1_Cutsets_Sei                                    1_Cutsets_Sei smic\CDF\1E-                                     smic-10\"                                             PC\CDF\1E-TrueEvent=".T                                    10\"
                     ."                                               TrueEvent=".T FalseEvent=".                                    ."
F." />                                           FalseEvent=".
F." />
A - 33

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-8 (continued)
Identification of Changes in Seismic PRA CDF PRAQuant File for Nominal Cases 3                        <Options                         3                       <Options ACUBECount="5                                            ACUBECount="5 00000"                                                   00000" ACUBEEnabled=                                            ACUBEEnabled=
                       "false"                                                  "false" ACUBEOpts="/I                                            ACUBEOpts="/I MP /N"                                                   MP /N" ClearLog="tru                                            ClearLog="tru e"                                                       e" CurrentQuanti                                            CurrentQuanti fier="Quant_F                                            fier="Quant_F TREX64-SEIS"                                             TRW6419" DeleCurVal="t                                            DeleCurVal="t rue"                                                     rue" ExpandMods="f                                            ExpandMods="f alse"                                                    alse" NoSendFailure                                            NoSendFailure List="True"                                              List="True" RunAcubeExe="                                            RunAcubeExe="
True"                                                    True" RunMissing="f                                            RunMissing="f alse"                                                    alse" SaveAll="fals                                            SaveAll="fals e"                                                       e" ShellWindowsS                                            ShellWindowsS tate="True"                                              tate="True" Singlefile="f                                            Singlefile="f alse" />                                                 alse" />
Note: No changes needed for the Seismic PRAQuant file. However, this comparison table is provided to show that the entry for NoSendFailureList="True" already existed in the SPRA PRAQuant file for the DG Liner LAR.
A - 34

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-9 Identification of Changes in Seismic PRA LERF PRAQuant File for Nominal Cases 2                     <Model              <>          2                <Model FaultTreeFile                                     FaultTreeFile
                    ="H1_IxxS_REV                                     ="H1_IxxS_REV
_8_ASM.caf"                                       _8_ASM.caf" DatabaseFile=                                     DatabaseFile=
                    "H1_CBM_REV_8                                     "H1_CBM_REV_8
_ASM.rr"                                          _ASM.rr" RecoveryFile=                                     RecoveryFile=
                    "CBM_RECV_U12                                     "CBM_RECV_U12
_REV_8_SEISMI                                     _REV_8_SEISMI C.recv"                                           C.recv" MasterFlagFil                                     MasterFlagFil e="FRAGILITY.                                     e="FRAGILITY.
flg"                                              flg" CutsetFile="U                                     CutsetFile="U 1_Cutsets_Sei                                     1_Cutsets_Sei smic\LERF\1E-                                     smic-11\"                                              PC\LERF\1E-TrueEvent=".T                                     11\"
                    ."                                                TrueEvent=".T FalseEvent=".                                     ."
F." />                                            FalseEvent=".
F." />
A - 35

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-9 (continued)
Identification of Changes in Seismic PRA LERF PRAQuant File for Nominal Cases 3                        <Options                         3                       <Options ACUBECount="5                                            ACUBECount="5 00000"                                                   00000" ACUBEEnabled=                                            ACUBEEnabled=
                       "false"                                                  "false" ACUBEOpts="/I                                            ACUBEOpts="/I MP /N"                                                   MP /N" ClearLog="tru                                            ClearLog="tru e"                                                       e" CurrentQuanti                                            CurrentQuanti fier="Quant_F                                            fier="Quant_F TREX64-SEIS"                                             TRW6419" DeleCurVal="t                                            DeleCurVal="t rue"                                                     rue" ExpandMods="f                                            ExpandMods="f alse"                                                    alse" NoSendFailure                                            NoSendFailure List="True"                                              List="True" RunAcubeExe="                                            RunAcubeExe="
True"                                                    True" RunMissing="f                                            RunMissing="f alse"                                                    alse" SaveAll="fals                                            SaveAll="fals e"                                                       e" ShellWindowsS                                            ShellWindowsS tate="True"                                              tate="True" Singlefile="f                                            Singlefile="f alse" />                                                 alse" />
Note: No changes needed for the Seismic PRAQuant file. However, this comparison table is provided to show that the entry for NoSendFailureList="True" already existed in the SPRA PRAQuant file for the DG Liner LAR.
A - 36

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-10 Identification of Changes in Seismic PRA Recovery File for Nominal Cases
                                           -+          3              **SET EVENTS UNKNOWN**
4              *
                                           -+          6              **SET EVENTS TRUE**
7              SEQ_*
                                           -+          9              **SUBSUME**
10             **COMPRESS**
4
                                           -+          14             **SET EVENTS UNKNOWN**
6                  **COMPRESS**           <>          17             **COMPRESS**
30                                                4
                                           -+          6155           SEQ_*
6151               **COMPRESS**           <>          6162           **COMPRESS**
1                                                 30 A - 37

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-11 Identification of Changes in Fire PRA PRAQuant File for DG OOS Cases 2                   <Model                <>          2               <Model FaultTreeFile                                     FaultTreeFile
                   ="..\H1_CBM_R                                     ="..\H1_CBM_R EV_8_IFL_ASM.                                     EV_8_IFL_ASM.
caf"                                              caf" DatabaseFile=                                     DatabaseFile=
                   "..\H1_CBM_RE                                     "..\H1_CBM_RE V_8_ASM.rr"                                       V_8_ASM.rr" MasterFlagFil                                     MasterFlagFil e="..\H1_CBM_                                     e="..\H1_CBM_
REV_8_FLG_ABA                                     REV_8_FLG_ABA O_ASM.FLG"                                        O_ASM.FLG" CutsetFile="H                                     CutsetFile="H 1_CBM_REV_8_A                                     1_CBM_REV_8_A BAO\"                                             BAO-PC\"
LogFile="Chan                                     LogFile="Chan gedCheckLog.t                                     gedCheckLog.t xt"                                               xt" Initiators="%                                     Initiators="%
Intiators="%*                                     Intiators="%*
LocalFlags="%                                     LocalFlags="%
FLD*=False; %                                     FLD*=False; %
IE*=False; %G                                     IE*=False; %G
                   *=False"                                          *=False" TrueEvent=".T                                     TrueEvent=".T FalseEvent=".                                     FalseEvent=".
F." />                                            F." />
A - 38

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-11 (continued)
Identification of Changes in Fire PRA PRAQuant File for DG OOS Cases 3                   <Options                          3               <Options ACUBECount="1                                     ACUBECount="1 000"                                              000" ACUBEEnabled=                                     ACUBEEnabled=
                   "false"                                           "false" ClearLog="tru                                     ClearLog="tru e"                                                e" CompressAll="                                     CompressAll="
26"                                               26" CurrentQuanti                                     CurrentQuanti fier="Quant_F                                     fier="Quant_F TREX1901"                                         TRW6419" CutsetFormat=                                     CutsetFormat=
                   "2"                                               "2" DeleCurVal="t                                     DeleCurVal="t rue"                                              rue" ExpandMods="t                                     ExpandMods="t rue"                                              rue" FalseEvent=".                                     FalseEvent=".
F"                                                F" MaxRecoveries                                     MaxRecoveries
                   ="6"                                              ="6" PruneBeforeFl                                     NoSendFailure ags="false"                                       List="True" RunMissing="f                                     PruneBeforeFl alse"                                             ags="false" SaveAll="fals                                     RunMissing="f e"                                                alse" ShellWindowSt                                     SaveAll="fals ate="1"                                           e" Singlefile="f                                     ShellWindowSt alse"                                             ate="1" TrueEvent=".T                                     Singlefile="f
                   "                                                 alse" TruncateToZer                                     TrueEvent=".T o="False" />                                      "
TruncateToZer o="False" />
A - 39

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-12 Identification of Changes in Fire PRA Recovery File for DG OOS Cases
                                            -+         3               **SET EVENTS UNKNOWN**
4               *
                                            -+         6               **SET EVENTS TRUE**
7               SEQ*
                                            -+         9               **SUBSUME**
10              **COMPRESS**
4
                                            -+         12              **REPLACE EVENTS**
MNUN1R43S001C 1.0 13              CC-DGS-102 14              **REPLACE EVENTS**
MNUN1R43S001C 1.0 15              CC-DGS-142 16              **REPLACE EVENTS**
MNUN1R43S001C 1.0 17              CC-DGS-182 18              **REPLACE EVENTS**
MNUN1R43S001C 1.0 19              CC-DGS-222
                                            -+         21              **CLEAR RECOVERY FLAGS**
22              **MAX RECOVERIES**
1 23              ;
24              ; add op action A - 40

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-12 (continued)
Identification of Changes in Fire PRA Recovery File for DG OOS Cases 25              ;
26              **CHANGEEVENT S** +OPHE-REC-PSW-F 27              %HF_1101J*
SEQ_SBO_28
                                                                       -OPHE* -CC-SW-1 28              **CHANGEEVENT S** +OPHE-REC-PSW-F 29              %HF_1101J*
SEQ_SBO_5
                                                                       -OPHE* -CC-SW-1
                                            -+         31              **SET EVENT PROBS**
32              OPHE-REC-PSW-F .05
                                            -+         34              **COMPRESS**
2 7                 **CLEAR                  +-
RECOVERY FLAGS**
9                 **SUBSUME**              +-
10                **COMPRESS**
30 2478              **CLEAR                  +-
RECOVERY FLAGS**
2479              **MAX RECOVERIES**
1 2480              ;
2481              ; add op action 2482              ;
A - 41

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-12 (continued)
Identification of Changes in Fire PRA Recovery File for DG OOS Cases 2483              **CHANGEEVENT S** +OPHE-REC-PSW-F 2484              %HF_1101J*
SEQ_SBO_28
                   -OPHE* -CC-SW-1 2485              **CHANGEEVENT S** +OPHE-REC-PSW-F 2486              %HF_1101J*
SEQ_SBO_5
                   -OPHE* -CC-SW-1 2488              **SET EVENT              +-
PROBS**
2489              OPHE-REC-PSW-F .05 2492              SEQ_*                    +-
A - 42

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-13 Identification of Changes in Internal Flood PRA PRAQuant File for DG OOS Cases 2                     <Model                <>        2                  <Model FaultTreeFile                                      FaultTreeFile
                    ="..\H1_CBM_R                                      ="..\H1_CBM_R EV_8_IFL_ASM.                                      EV_8_IFL_ASM.
CAF"                                               CAF" DatabaseFile=                                      DatabaseFile=
                    "..\H1_CBM_RE                                      "..\H1_CBM_RE V_8_ASM.rr"                                        V_8_ASM.rr" MasterFlagFil                                      MasterFlagFil e="..\H1_CBM_                                      e="..\H1_CBM_
REV_8_FLG_ABA                                      REV_8_FLG_ABA O_ASM.FLG"                                         O_ASM.FLG" CutsetFile="H                                      CutsetFile="H 1_CBM_REV_8_F                                      1_CBM_REV_8_F LOOD\"                                             LOOD-PC\"
LogFile="REV8                                      LogFile="REV8
                    -1TOP-IL-                                          -1TOP-IL-LOG.txt"                                           LOG.txt" Initiators="%                                      Initiators="%
Intiators="%*                                      Intiators="%*
LocalFlags="%                                      LocalFlags="%
HF*=False; %I                                      HF*=False; %I E*=False; %G*                                      E*=False; %G*
                    =False"                                            =False" TrueEvent=".T                                      TrueEvent=".T FalseEvent=".                                      FalseEvent=".
F." />                                             F." />
A - 43

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-13 (continued)
Identification of Changes in Internal Flood PRA PRAQuant File for DG OOS Cases 3                     <Options                        3                  <Options ACUBECount="1                                      ACUBECount="1 000"                                               000" ACUBEEnabled=                                      ACUBEEnabled=
                    "false"                                            "false" ClearLog="tru                                      ClearLog="tru e"                                                 e" CompressAll="                                      CompressAll="
26"                                                26" CurrentQuanti                                      CurrentQuanti fier="Quant_F                                      fier="Quant_F TREX64-SEIS"                                       TRW6419" CutsetFormat=                                      CutsetFormat=
                    "2"                                                "2" DeleCurVal="t                                      DeleCurVal="t rue"                                               rue" ExpandMods="t                                      ExpandMods="t rue"                                               rue" FalseEvent=".                                      FalseEvent=".
F"                                                 F" MaxRecoveries                                      MaxRecoveries
                    ="6"                                               ="6" PruneBeforeFl                                      NoSendFailure ags="false"                                        List="True" RunMissing="f                                      PruneBeforeFl alse"                                              ags="false" SaveAll="fals                                      RunMissing="f e"                                                 alse" ShellWindowSt                                      SaveAll="fals ate="1"                                            e" Singlefile="f                                      ShellWindowSt alse"                                              ate="1" TrueEvent=".T                                      Singlefile="f
                    "                                                  alse" TruncateToZer                                      TrueEvent=".T o="False" />                                       "
TruncateToZer o="False" />
A - 44

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-14 Identification of Changes in Internal Flood PRA Recovery File for DG OOS Cases
                                              -+       3                 **SET EVENTS UNKNOWN**
4                 *
                                              -+       6                 **SET EVENTS TRUE**
7                 SEQ_*
                                              -+       9                 **SUBSUME**
10                **COMPRESS**
4
                                              -+       12                **REPLACE EVENTS**
MNUN1R43S001C 1.0 13                CC-DGS-102 14                **REPLACE EVENTS**
MNUN1R43S001C 1.0 15                CC-DGS-142 16                **REPLACE EVENTS**
MNUN1R43S001C 1.0 17                CC-DGS-182 18                **REPLACE EVENTS**
MNUN1R43S001C 1.0 19                CC-DGS-222
                                              -+       21                **COMPRESS**
2
                                              -+       23                **CLEAR RECOVERY FLAGS**
A - 45

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-14 (continued)
Identification of Changes in Internal Flood PRA Recovery File for DG OOS Cases
                                              -+        25               ;Remove illegitimate cutsets.
These cutsets have OSP recovery successful on the success branch of the sequence but no credit for OSP recovery on the failure branch
                                              -+        27               **RECOVERY**
DEL 0 28               SEQ_LOSP-2 SEQ_OSPREC OPHE*
29               SEQ_LOSP-5 SEQ_OSPREC OPHE*
                                              -+        36               **SET EVENTS UNKNOWN**
37
* 10                  **COMPRESS**             <>        42               **COMPRESS**
30                                                  4
                                              -+        94               ;These cutsets conservativel y applied a 5 hour OSP recovery when 10 hours is warranted
                                              -+        96               **MAX RECOVERIES**
1 A - 46

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-14 (continued)
Identification of Changes in Internal Flood PRA Recovery File for DG OOS Cases 97               **RECOVERY**
NR-OSP-5to10H 0.523 98               SEQ_LOSP-9 CONSEQ-NR1-5H 99               SEQ_GT_10 CONSEQ-NR1-5H 100              SEQ_GT_3 CONSEQ-NR1-5H 101              SEQ_LOSP-13 CONSEQ-NR1-5H 102              SEQ_LOSP-16 CONSEQ-NR1-5H 103              SEQ_GT_16 CONSEQ-NR1-5H 104              SEQ_LOSP-22 CONSEQ-NR1-5H 105              SEQ_LOSP-19 CONSEQ-NR1-5H 106              SEQ_GT_22 CONSEQ-NR1-5H 107              SEQ_GT_19 CONSEQ-NR1-5H 108              SEQ_LOSP-9 ZNR-OSP-5H 109              SEQ_GT_10 ZNR-OSP-5H 110              SEQ_GT_3 ZNR-OSP-5H 111              SEQ_LOSP-13 ZNR-OSP-5H 112              SEQ_LOSP-16 ZNR-OSP-5H 113              SEQ_GT_16 ZNR-OSP-5H 114              SEQ_LOSP-22 ZNR-OSP-5H 115              SEQ_LOSP-19 ZNR-OSP-5H 116              SEQ_GT_22 ZNR-OSP-5H 117              SEQ_GT_19 ZNR-OSP-5H A - 47

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-14 (continued)
Identification of Changes in Internal Flood PRA Recovery File for DG OOS Cases
                                              -+        119              **SUBSUME**
120              **COMPRESS**
4 Table 3a-15 Identification of Changes in Internal Events PRA PRAQuant File for DG OOS Cases 2                     <Model                 <>        2                  <Model FaultTreeFile                                       FaultTreeFile
                     ="..\H1_CBM_R                                       ="..\H1_CBM_R EV_8_IFL_ASM.                                       EV_8_IFL_ASM.
CAF"                                                caf" DatabaseFile=                                       DatabaseFile=
                     "..\H1_CBM_RE                                       "..\H1_CBM_RE V_8_ASM.rr"                                         V_8_ASM.rr" MasterFlagFil                                       MasterFlagFil e="..\H1_CBM_                                       e="..\H1_CBM_
REV_8_FLG_ABA                                       REV_8_FLG_ABA O_ASM.FLG"                                          O_ASM.FLG" CutsetFile="H                                       CutsetFile="H 1_CBM_REV_8_F                                       1_CBM_REV_8_F PIE\"                                               PIE-PC\"
LogFile="Rev8                                       LogFile="Rev8
                     -IE-Log.txt"                                        -IE-Log.txt" Initiators="%                                       Initiators="%
Intiators="%*                                       Intiators="%*
LocalFlags="%                                       LocalFlags="%
HF*=False; %F                                       HF*=False; %F LD*=False; %G                                       LD*=False; %G
                     *=False"                                            *=False" TrueEvent=".T                                       TrueEvent=".T FalseEvent=".                                       FalseEvent=".
F." />                                              F." />
A - 48

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-15 (continued)
Identification of Changes in Internal Events PRA PRAQuant File for DG OOS Cases 3                     <Options                         3                 <Options ACUBECount="1                                      ACUBECount="1 000"                                               000" ACUBEEnabled=                                      ACUBEEnabled=
                     "false"                                            "false" ClearLog="tru                                      ClearLog="tru e"                                                 e" CompressAll="                                      CompressAll="
26"                                                26" CurrentQuanti                                      CurrentQuanti fier="Quant_F                                      fier="Quant_F TREX64-SEIS"                                       TRW6419" CutsetFormat=                                      CutsetFormat=
                     "2"                                                "2" DeleCurVal="t                                      DeleCurVal="t rue"                                               rue" ExpandMods="t                                      ExpandMods="t rue"                                               rue" FalseEvent=".                                      FalseEvent=".
F"                                                 F" MaxRecoveries                                      NoOverridePro
                     ="6"                                               bs="false" NoOverridePro                                      NoSendFailure bs="false"                                         List="True" PruneBeforeFl                                      PruneBeforeFl ags="false"                                        ags="false" RunMissing="f                                      RunMissing="f alse"                                              alse" SaveAll="fals                                      SaveAll="fals e"                                                 e" ShellWindowSt                                      ShellWindowSt ate="1"                                            ate="1" Singlefile="f                                      Singlefile="f alse"                                              alse" TrueEvent=".T                                      TrueEvent=".T TruncateToZer                                      TruncateToZer o="False" />                                       o="False" />
A - 49

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-16 Identification of Changes in Internal Events PRA Recovery File for DG OOS Cases
                                             -+        3                **SET EVENTS UNKNOWN**
4                *
                                             -+        6                **SET EVENTS TRUE**
7                SEQ_*
                                             -+        9                **SUBSUME**
10               **COMPRESS**
4
                                             -+        12               **REPLACE EVENTS**
MNUN1R43S001C 1.0 13               CC-DGS-102 14               **REPLACE EVENTS**
MNUN1R43S001C 1.0 15               CC-DGS-142 16               **REPLACE EVENTS**
MNUN1R43S001C 1.0 17               CC-DGS-182 18               **REPLACE EVENTS**
MNUN1R43S001C 1.0 19               CC-DGS-222 20               **COMPRESS**
2
                                             -+        22               **CLEAR RECOVERY FLAGS**
A - 50

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-16 (continued)
Identification of Changes in Internal Events PRA Recovery File for DG OOS Cases
                                             -+        24               ;Remove illegitimate cutsets.
These cutsets have OSP recovery successful on the success branch of the sequence but no credit for OSP recovery on the failure branch
                                             -+        26               **RECOVERY**
DEL 0 27               SEQ_LOSP-2 SEQ_OSPREC OPHE*
28               SEQ_LOSP-5 SEQ_OSPREC OPHE*
                                             -+        33               **SET EVENTS UNKNOWN**
34
* 8                  **COMPRESS**             <>        38               **COMPRESS**
30                                                  4
                                             -+        43               **REPLACE EVENTS**
OPHEELAP-ALTPWR-X 1.0 44               OPHEELAP-ALTPWR OPHEELAP-ALTPR-FLAG
                                             -+        58               **COMPRESS**
2 A - 51

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-16 (continued)
Identification of Changes in Internal Events PRA Recovery File for DG OOS Cases 26                 **REPLACE                <>        60 EVENTS**
OPHEELAP-ALTPWR-X 1.0 27                 OPHEELAP-                          61 ALTPWR OPHEELAP-ALTPR-FLAG
                                             -+        95               ;These cutsets conservativel y applied a 5 hour OSP recovery when 10 hours is warranted
                                             -+        97               **MAX RECOVERIES**
1 98               **RECOVERY**
NR-OSP-5to10H 0.523 99               SEQ_LOSP-9 CONSEQ-NR1-5H 100              SEQ_GT_10 CONSEQ-NR1-5H 101              SEQ_GT_3 CONSEQ-NR1-5H 102              SEQ_LOSP-13 CONSEQ-NR1-5H 103              SEQ_LOSP-16 CONSEQ-NR1-5H 104              SEQ_GT_16 CONSEQ-NR1-5H 105              SEQ_LOSP-22 CONSEQ-NR1-5H 106              SEQ_LOSP-19 CONSEQ-NR1-5H 107              SEQ_GT_22 CONSEQ-NR1-5H 108              SEQ_GT_19 CONSEQ-NR1-5H A - 52

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-16 (continued)
Identification of Changes in Internal Events PRA Recovery File for DG OOS Cases 109              SEQ_LOSP-9 ZNR-OSP-5H 110              SEQ_GT_10 ZNR-OSP-5H 111              SEQ_GT_3 ZNR-OSP-5H 112              SEQ_LOSP-13 ZNR-OSP-5H 113              SEQ_LOSP-16 ZNR-OSP-5H 114              SEQ_GT_16 ZNR-OSP-5H 115              SEQ_LOSP-22 ZNR-OSP-5H 116              SEQ_LOSP-19 ZNR-OSP-5H 117              SEQ_GT_22 ZNR-OSP-5H 118              SEQ_GT_19 ZNR-OSP-5H
                                             -+        120              **SUBSUME**
121              **COMPRESS**
4 A - 53

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-17 Identification of Changes in Seismic PRA Flag File for DG OOS Cases 288                 ;Flag events            +-
to lock shared diesel to Unit 1 during 1C outage.
Appear in recovery rules so set to 1.0 289                 FL-DG1BALIGN-SPRA EQU .F.
Note: Flag event FL-DG1BALIGN-SPRA EQU .F. was deleted from the updated Flag file on the right hand side.
Table 3a-18 Identification of Changes in Seismic PRA Recovery File for DG OOS Cases
                                             -+        3                   **SET EVENTS UNKNOWN**
4                   *
                                             -+        6                   **SET EVENTS TRUE**
7                   SEQ_*
                                             -+        9                   **SUBSUME**
10                  **COMPRESS**
4
                                             -+        12                  **REPLACE EVENTS**
MNUN1R43S001C 1.0 13                  CC-DGS-102 A - 54

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3a-18 (continued)
Identification of Changes in Seismic PRA Recovery File for DG OOS Cases 14                **REPLACE EVENTS**
MNUN1R43S001C 1.0 15                CC-DGS-142 16                **REPLACE EVENTS**
MNUN1R43S001C 1.0 17                CC-DGS-182 18                **REPLACE EVENTS**
MNUN1R43S001C 1.0 19                CC-DGS-222
                                                 -+           21                **COMPRESS**
2
                                                 -+           25                **SET EVENTS UNKNOWN**
6                     **COMPRESS**              <>           28                **COMPRESS**
30                                                       4
                                                 -+           6166              SEQ_*
6151                  **COMPRESS**              <>           6173              **COMPRESS**
1                                                        30 Response 3b The sensitivity cases in the response to RAI 3b are focused on the risk impact of DG 1C OOS on all Unit 1 hazard groups because the NRC noted that the DG 1C OOS case evaluation in the DG Liner LAR resulted in a reduction in risk for the seismic hazard, which led to the evaluation of the modeling errors as discussed in RAI 3a. In addition, individual DG OOS cases typically result in relatively high increases in CDF and LERF compared to other single SSC OOS cases, especially for seismic events, which often lead to loss of offsite power. Therefore, the DG OOS case is an appropriate representative case for the purposes of comparing calculated delta A - 55

Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information seismic CDF and LERF values against seismic penalty values. For similar reasons, the risk impact of DG 2C OOS was quantified to calculate the risk impact on CDF and LERF for all Unit 2 hazard groups.
The left-hand side of Table 3b-1 provides the Unit 1 PRA quantification results from Tables 3.5-1 and 3.5-2 of the DG Liner LAR for the nominal and DG 1C OOS cases. The right-hand side of Table 3b-1 provides the updated results in red text based on the changes in the PRAQuant advanced tab settings, Flag file, and recovery file identified in the response to RAI 3a above. Table 3b-1 shows relatively minor differences in the CDF and LERF results for both the nominal cases and the DG 1C OOS cases.
Table 3b-2 indicates that the increase in risk for the Unit 2 Internal Events and Fire CDF and LERF PRA quantification results for the DG 2C OOS case are higher than the comparable DG 1C OOS cases. Table 3b-2 indicates that the increase in risk for the Internal Flood and Seismic cases are comparable for the DG 2C and DG 1C OOS cases. The seismic CDF and LERF results for the DG OOS cases remain below the seismic CDF and LERF penalty values of 1.18E-06/yr and 2.95E-07/yr, respectively, in the Hatch RICT LAR. As noted in the response to RAI 1, while the seismic CDF penalty value will remain at 1.18EE-06/yr, the seismic LERF penalty value is proposed to be increased from 2.95E-07/yr to 3.66E-07/yr to account for an increased SCLERP value of 0.31.
It is recognized that the increase in FPIE PRA and Fire PRA risk for the Unit 2 DG 2C OOS quantification is higher than the increase in FPIE PRA and Fire PRA risk for the Unit 1 DG 1C OOS quantification. Conservatisms in the Unit 1 DG 1C OOS case quantification were reviewed in detail to support the DG Liner LAR. Some conservatisms in the Unit 1 DG 1C OOS case quantification were reduced to support more realistic quantitative results as needed to support the DG Liner LAR. Potential conservatisms in the Unit 2 DG 2C OOS case quantification were not re-evaluated in detail for the purposes of this RAI response. However, any potential conservatism in the FPIE PRA and Fire PRA risk for the Unit 2 DG 2C OOS case quantification does not alter the conclusion that the seismic CDF and LERF penalty values in the Hatch RICT LAR are not impacted. In addition, the conclusions from the DG Liner LAR are not impacted because the risk impact of DG 2C OOS was not in the scope of the DG Liner LAR.
The identified changes were entered into the SNC Corrective Action Program and are being tracked and integrated into the Hatch PRA model maintenance and update process. Therefore, the identified changes will be accounted for in the hazard PRA models quantified to support the RICT program.
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Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3b-1 Results for Unit 1 Quantification with EDG 1C OOS Cases with Modeling Issues Resolved (Original results taken from Table 3.5-1 of DG Liner LAR for DG 1C OOS)
Unit 1 EDG 1C Case - ICCDP                                 New Results                       % Change Updated PRA        CDFBASE                                          Updated                  Updated CDFINST (/yr) Time     ICCDP                     CDFINST Hazard     (/yr)                                         CDFBASE (/yr)               ICCDP
(/yr)
Internal                                 19                                           3.26E-5.01E-06     1.09E-05              3.07E-07   4.84E-06       1.11E-05             6%
Events                                  days                                            07 Internal                                 19                                           4.76E-2.38E-07     1.06E-06              4.28E-08   2.45E-07       1.16E-06             11%
Flood                                   days                                            08 Internal                                 19                                           8.85E-5.89E-05     7.58E-05              8.80E-07   5.89E-05       7.59E-05             1%
Fire                                    days                                            07 19      0.00E+0                              1.35E-Seismic      9.53E-07     8.64E-07                         8.89E-07       9.15E-07              NA days        0                                   09 Total                                    19                                           1.26E-6.51E-05     8.86E-05              1.23E-06   6.49E-05       8.91E-05             3%
Risk                                    days                                            06 Unit 1 EDG 1C Case - ICLERP                                New Results                       % Change Updated       Updated PRA        LERFBASE    LERFINST                                                Updated Time    ICLERP   LERFBASE      LERFINST Hazard          (/yr)      (/yr)                                                 ICLERP
(/yr)        (/yr)
Internal                                 19 3.66E-07   6.40E-07             1.43E-08  3.46E-07     6.46E-07    1.56E-08    9%
Events                                  days Internal                                 19 5.95E-09   2.35E-08             9.14E-10  6.11E-09     2.66E-08    1.07E-09    17%
Flood                                   days Internal                                 19 3.64E-06   4.05E-06             2.13E-08  3.64E-06     4.06E-06    2.19E-08    2%
Fire                                    days 19      0.00E+0 Seismic         2.47E-07   2.15E-07                       2.32E-07     2.38E-07    3.12E-10     NA days        0 19 Total Risk      4.26E-06   4.93E-06             3.49E-08  4.22E-06     4.97E-06    3.89E-08    11%
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Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Table 3b-2 Results for Unit 2 Quantification with EDG 2C OOS Cases with Modeling Issues Resolved Unit 2 EDG 2C Case - ICCDP (Note 1)                              New Results Updated     Updated              % Change PRA           CDFBAS     CDFINS                                               Updated Time   ICCDP        CDFBASE     CDFINST Hazard        E (/yr)    T (/yr)                                               ICCDP
(/yr)       (/yr)
Internal N/A        N/A      N/A     N/A        7.16E-06    5.91E-05 2.70E-06        N/A Events Internal N/A        N/A      N/A     N/A        2.98E-07    1.43E-06 5.89E-08        N/A Flood Internal N/A        N/A      N/A     N/A        5.51E-05    9.67E-05 2.17E-06        N/A Fire Seismic          N/A        N/A      N/A     N/A        8.21E-07    8.46E-07 1.30E-09        N/A Total Risk       N/A        N/A      N/A     N/A        6.34E-05    1.58E-04 4.93E-06        N/A Unit 2 EDG 2C Case - ICLERP (Note 1)                             New Results Updated     Updated               % Change PRA          LERFBAS    LERFINS     Tim    ICLER                              Updated LERFBASE    LERFINST Hazard       E (/yr)    T (/yr)     e      P                                  ICLERP
(/yr)       (/yr)
Internal N/A         N/A      N/A     N/A       3.49E-07    1.77E-06  7.40E-08        N/A Events Internal N/A         N/A      N/A     N/A       7.05E-09    5.27E-08  2.38E-09        N/A Flood Internal N/A         N/A      N/A     N/A       3.62E-06    5.87E-06  1.17E-07        N/A Fire Seismic         N/A         N/A      N/A     N/A       2.53E-07    2.61E-07  4.16E-10        N/A Total Risk      N/A         N/A      N/A     N/A       4.23E-06    7.95E-06  1.94E-07        N/A Note (1): The Unit 2 EDG 2C OOS Case results were not previously quantified because they were not required for the scope of the DG Liner LAR.
Response 3c Table 3b-1 supports that resolution of the model errors still results in a change in risk for the DG 1C OOS that is bounded by the seismic penalties. Table 3b-2 also supports that resolution of the model errors still results in a change in risk for the DG 1C OOS that is bounded by the seismic penalties. Therefore, the SCDF and SLERF penalties in the Hatch RICT LAR are not affected by the modeling errors and resolutions identified in the response to RAI 3a. As noted in the response to RAI 1, while the seismic CDF penalty value will remain at 1.18EE-06/yr, the seismic LERF penalty value is proposed to be increased from 2.95E-07/yr to 3.66E-07/yr to account for an increased SCLERP value of 0.31.
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Attachment to NL-22-0590 SNC Response to NRC Request for Additional Information Refer to the first paragraph in the response to RAI 3b for a discussion of why the DG 1C and DG 2C OOS quantifications are appropriate representative cases for the purposes of comparing calculated delta seismic CDF and LERF values against seismic penalty values.
Response 3d Refer to Table 3b-1 for the updated information for Tables 3.5-1 and 3.5-2 of the DG Liner LAR for DG 1C OOS for the Unit 1 SPRA quantification results reflecting the resolution of the modeling errors discussed in the response to RAI 3a. As discussed in the response to RAI 3c the changes to the SPRA model identified in the response to RAI 3a do not affect the conclusion regarding the conservatism of the SCDF and SLERF penalty values proposed in the TSTF-505 LAR.
In order to address any remaining uncertainty associated with the seismic penalty and its use for the RICT program, the SCLERP for calculating the seismic LERF penalty will be set at 0.31 using the highest value shown for Case 1b in Table 1-2 in the response to RAI 1. The higher observed SCLERP is being driven by the conservative SPRA model used in the Hatch DG Liner LAR and not due to the resolution of the errors discussed in the responses to RAIs 3a and 3b.
For the Hatch RICT LAR, the seismic CDF penalty will remain at 1.18E-06/yr. However, the seismic LERF penalty will be increased from 2.95E-07/yr to 3.66E-07/yr (i.e., 1.18E-06/yr
* 0.31
= 3.66E-07/yr).
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