ML25034A117

ACRS Presentation Slides-NuScale SDAA FSAR Chapter 6, Section 17.4 and Chapter 19 Subcommittee Meeting

ML25034A117
Person / Time
Issue date:	02/12/2025
From:	Prosanta Chowdhury, Alina Schiller, Getachew Tesfaye NRC/NRR/DNRL/NRLB
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Non-Proprietary Presentation to the Advisory Committee on Reactor Safeguards Subcommittee Staff Review of NuScales US460 Standard Design Approval Application (SDAA)

Final Safety Analysis Report (FSAR), Revision 1 February 18th, 2025 (Open Session) 1 Chapters 6 and 19, and Section 17.4

Non-Proprietary Presentation to the ACRS Subcommittee Staff Review of NuScale SDAA FSAR, Revision 1 Chapter 6, Engineered Safety Features February 18th, 2025 (Open Session) 2

Non-Proprietary NuScale SDAA FSAR Chapter 6 Review NuScale submitted Chapter 6, Engineered Safety Features Revision 0 of the SDAA FSAR on December 31, 2022, and Revision 1 on October 31, 2023 NRC regulatory audit of Chapter 6 was performed from March 2023 to August 2023, generating 46 audit issues Questions raised during the audit were resolved within the audit. Six RAIs were issued, and the responses were acceptable Staff completed Chapter 6 review and issued an advanced safety evaluation to support todays ACRS Subcommittee meeting No significant changes between draft SE provided to ACRS on 1/18/25 and SE submitted on 2/12/25 3

Overview

Non-Proprietary NuScale SDAA FSAR Chapter 6 Review Technical Reviewers Robert Davis, NRR/DNRL/NPHP Matthew Yoder, NRR/DNRL/NCSG Syed Haider, NRR/DSS/SNSB Dan Widrevitz, NRR/DNRL/NVIB Brian Lee, NRR/DSS/SCPB Anne-Marie Grady, NRR/DRA/APLC Ryan Nolan, NRR/DSS/SNRB Sean Piela, NRR/DSS/SNRB Shanlai Lu, NRR/DSS/SNRB David Nold, NRR/DSS/SCPB Stephen Cumblidge, NRR/DNRL/NPHP Hanry Wagage, NRR/DSS/SCPB Project Manager

- Getachew Tesfaye, NRR/DNRL/NRLB 4

Contributors

Non-Proprietary NuScale SDAA FSAR Chapter 6 Review Section 6.1 - Engineered Safety Feature Materials Section 6.2 - Containment Systems Section 6.3 - Emergency Core Cooling System Section 6.4 - Control Room Habitability Section 6.5 - Fission Product Removal and Control Systems Section 6.6 - Inservice Inspection and Testing of Class 2 and 3 Systems and Components Section 6.7 - Main Steamline Isolation Valve Leakage Control System (BWR) 5 Sections

Non-Proprietary NuScale SDAA FSAR Chapter 6 Review Significant differences between NuScale DCA FSAR and NuScale SDAA FSAR include:

The use of ASME Code Case N-774, Use of 13Cr-4Ni (Alloy UNS S41500) Grade F6NM Forgings Weighing in Excess of 10,000 lb (4540 kg) and Otherwise Conforming to the Requirements of SA-336/SA-336M for Class 1, 2, 3 Construction Section III, Division 1.

• Code Case N-774 is listed in Regulatory Guide 1.84, Rev. 39, Design, Fabrication, and Material Code Case Acceptability, ASME Section III, Division 1, as permitted for use without conditions.

• F6NM replaces SA-508, Grade 3, Class 2 from the previous design for the upper CNV and a portion of the lower CNV below the upper/lower vessel flange.

6 Section 6.1.1 Engineered Safety Features Materials

Non-Proprietary NuScale SDAA FSAR Chapter 6 Review Welding/fabrication when using F6NM requires special considerations in addition to ASME Code requirements:

The applicant has considered the effect of welding procedures on the Martensite start (Ms) and Martensite finish (Mf) temperatures Applicant will not follow recommended preheat temperature listed in Section III, non-mandatory Appendix D regarding weld preheat temperatures The applicant is employing an extensive testing program to determine the appropriate preheat temperature to prevent hydrogen cracking while at the same time promote martensite formation.

7 Section 6.1.1 Engineered Safety Features Materials

Non-Proprietary NuScale SDAA FSAR Chapter 6 Review Welding/fabrication when using F6NM requires special considerations in addition to ASME Code requirements (cont):

Welding processes that employ flux may require post weld heat treatment (PWHT) times than those specified in ASME Code.

• Oxygen pickup from flux welding processes may require PWHT times greater than those specified in ASME Code to ensure adequate impact toughness.

8 Section 6.1.1 Engineered Safety Features Materials

Non-Proprietary NuScale SDAA FSAR Chapter 6 Review Welding/fabrication when using F6NM requires special considerations in addition to ASME Code requirements (cont):

ASME Code specifies that the PWHT temperature range, for F6NM welds, is 1050°F to 1150°F. The lower critical (Ac1) temperature for 410NiMo type weld metals and F6NM base material can be as low as 1150°F or slightly lower.

SDAA Section 6.1.1.1 will be modified to state, Post weld heat treatment of SA-336 Gr F6NM for the CNV and supports shall be 1075°F +/- 25°F.

• Provides adequate margin to ensure that PWHT temperature does not exceed Ac1.

Staff determined that additional controls/considerations placed on the fabrication of F6NM are adequate.

Staff conclusion did not change from the DCA 9

Section 6.1.1 Engineered Safety Features Materials

Non-Proprietary NuScale SDAA FSAR Chapter 6.2.1/6.2.2 Review 10 Major Design Changes from DCA to SDAA NPM-160 for US600 (DCA)

NPM-20 for US460 (SDAA)

Rated thermal power 160 MWt 250 MWt CNV upper vessel material SA-508 SA-336 (F6NM)

Reactor pool level 65 ft 52 ft Initial Reactor pool temperature 110 oF 140 oF (TS=120 oF)

Initial CNV wall temperature above pool level 240 oF 500 oF Number of RVVs 3

2 IABs used on RRVs & RVVs RRVs IAB release pressure range 900-1000 psid 400-500 psid Venturis used on None RRVs & RVVs DHRS operation for the DBE mitigation Not credited Credited CNV design pressure 1050 psia 1200 psia CNV design temperature 550 oF 600 oF

Non-Proprietary NuScale SDAA FSAR Chapter 6.2.1/6.2.2 Review 11 Additional Significant Changes from DCA to SDAA Containment Response Analysis Methodology (CRAM) TeR was IBRed in the DCA. Modified CRAM for the SDAA CNV design for NPM-20 is a part of the LOCA EM TR-0516-49422.

A CNV free volume ITAAC included in SDAA to ensure that the as-built CNV free volume bounds the minimum value of 6000 ft3used in the CNV safety analyses.

DHRS credited to SDAA CNV DBEs: Reactor cooling pool heat-up and thermal stratification effects on DHRS and CNV heat removal performance degradation Sensitivity of the CNV LOCA T/H response to break size & ECCS actuation Justification for the natural convection heat transfer modeling NuScale provided necessary analyses and justification through RAI 10359 response Containment P/T limiting design basis events have changed DCA SDAA Peak CNV Pressure DBE Inadvertant RRV opening RCS discharge line break LOCA Peak CNV Pressure 994 psia 937 psia CNV Pressure Margin

~5% (vs. pdesign = 1050 psia)

~22% (vs. pdesign = 1200 psia)

Peak CNV Temperature DBE RCS injection line break LOCA RCS discharge line break LOCA Peak CNV Wall Temperature 526 oF 533 oF CNV Temperature Margin 24 oF (vs. Tdesign = 550 oF )

67 oF (vs. Tdesign = 600 oF )

Non-Proprietary NuScale SDAA FSAR Chapter 6.2.1/6.2.2 Review 12 Staff Confirmatory Analysis Results for the SDAA NPM-20 CNV Staff (MELCOR) & Applicants (NRELAP5) Results for the Combined P/T Limiting DBA Case LOCA caused by RCS (CVCS) discharge line break from the downcomer (limiting CRAM DBE)

(DL) - A primary systems M&E release event NRELAP5 Results:

Peak containment pressure predicted is 937 psia (<1200 psia limit)

Maximum containment wall temperature predicted is 533 F (< 600 F limit)

Non-Proprietary NuScale SDAA FSAR Chapter 6.2.1/6.2.2 Review 13 Conclusions The containment safety analyses appropriately modeled the relevant phenomena in the NPM-20 CNV response including condensation heat

transfer, non-condensable gas

effect, decay

heat, choked

flow, DHRS/ECCS impact, and CNV heat removal to the reactor pool.

NuScale CNV design incorporates sufficient conservatism in the NPM-20 CNV model ICs/BCs for the US460 design.

NuScale SDAA FSAR Chapter 6 provides sufficient and acceptable information for analyzing the M&E release into the CNV for the spectrum of primary and secondary design basis events, and determining the limiting CNV pressure and temperature response.

NuScale CNV design meets all regulatory requirements and acceptance criteria for the containment safety design.

Non-Proprietary NuScale SDAA FSAR Chapter 6.2.5 Review 14 Significant Changes from DCA to SDAA Change DCA SDAA Applicable Regulation 10 CFR 50.44(c) 10 CFR 50.44(d)

Guidance SRP 6.2.5, 19.0 RG 1.7, SRP 19.0 Combustible Gas Control CNV combustion analysis PAR maintains inert CNV Safety category No PAR Safety-related PAR ITAAC none Physical arrangement and installation; analysis and test of recombination rate; part of EQ Tech Specs none LCO 3.6.4 on PAR operability CGC technical report TR-0716-50424, rev 1 Several - prop, ECI Exemption Request #2 Uncertain means of post-accident monitoring of H2, O2 No post-accident H2, O2 monitoring

Non-Proprietary NuScale SDAA FSAR Chapter 6.2.5 Review The CNV is not inert (<4% O2 in presence of H2) during a design basis accident (DBA) in the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of a non-core damage AOO.

10 CFR 50.44(c) applies mainly to severe accidents 10 CFR 50.44(d)(2) applies to the the safety impacts of combustible gases during design basis and significant beyond design basis accidents 15 Acceptability of 50.44(d) as Applicable Regulation for CGC in SDAA

Non-Proprietary NuScale SDAA FSAR Chapter 6.2.5 Review Combustible Gas Control conclusion:

During non-core damage DBA LOCA, PAR is credited to maintain an inert CNV Post severe accident, CNV remains inert without crediting PAR During long term radiolysis, PAR is credited to maintain an inert CNV Exemption request #2 Post accident monitoring of H2 and O2 not required to assess core damage. Assessment to be accomplished by core exit thermocouples and radiation monitors beneath the bioshield.

16 Conclusion

Non-Proprietary NuScale SDAA FSAR Chapter 6 Review Significant differences between NuScale DCA FSAR and NuScale SDAA FSAR include:

F6NM replaces SA-508, Grade 3, Class 2 from the previous design for the upper CNV and a portion of the lower CNV below the upper/lower vessel flange.

Staff verified that material change would not result in significant impacts on fracture toughness management of CNV.

Staff conclusion did not change from DCD.

17 Section 6.2.7 Fracture Prevention Containment Vessel

Non-Proprietary NuScale SDAA FSAR Chapter 6 Review Significant differences between NuScale DCA FSAR and NuScale SDAA FSAR include:

Addition of passive Emergency Supplemental Boron (ESB) feature.

Chapter 14 includes first of a kind test Extended Passive Cooling topical report and SDAA 15.0.5 contain boron transport methodology and analysis Removal of Inadvertent Actuation Block Valves (IABs) on Reactor Vent Valves (RVVs) - IABs retained for Reactor Recirculation Valves (RRVs).

Inclusion of flow restricting venturis in RVVs and RRVs.

Exclusion of flange breaks from LOCA break spectrum evaluated in SER 15.6.5 ECCS actuation signals changed to RPV riser level.

Chapter 15 review confirms modeling of the riser level sensor 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> timer actuates ECCS valves after an automatic or manual trip Recirculates boron from ESB into core to maintain subcriticality Vents accumulated combustible gas from radiolysis 18 Section 6.3 Emergency Core Cooling System (ECCS)

Non-Proprietary Presentation to the ACRS Subcommittee Staff Review of NuScale SDAA FSAR, Revision 1 Chapter 17, Quality Assurance and Reliability Assurance, Section 17.4, Reliability Assurance Program February 18, 2025 (Open Session) 19

Non-Proprietary NuScale SDAA FSAR Section 17.4 Review NuScale submitted Chapter 17, Quality Assurance and Reliability Assurance, Revision 0 of the NuScale SDAA FSAR on December 28, 2022, and Revision 1 on October 31, 2023.

NRC performed a regulatory audit as part of its review of Chapter 17, Section 17.4, from March 2023 to June 2024.

Questions raised during the audit were resolved within the audit. One RAI was issued, and the response was acceptable.

Staff completed the review of Chapter 17, Section 17.4 and issued an advanced safety evaluation to support the ACRS Subcommittee meeting.

No significant changes between draft SE provided to ACRS on 1/18/25 and SE provided on 2/12/25 20 Overview

Non-Proprietary NuScale SDAA FSAR Section 17.4 Review Technical Reviewers Alissa Neuhausen, NRR/DRA/APLC Steven Alferink, NRR/DRA/APLC Keith Tetter, NRR/DRA/APLC Project Managers Prosanta Chowdhury, PM, NRR/DNRL/NRLB Getachew Tesfaye, Lead PM, NRR/DNRL/NRLB 21 Contributors

Non-Proprietary NuScale SDAA FSAR Section 17.4 Review EDAS provides power to maintain ECCS valves closed during normal operation and contributes to defense in depth in the design.

Reactor vent valves do not include an inadvertent actuation block valve.

Safety-related PAR added to maintain the containment atmosphere inert during design-basis events and significant beyond-design-basis events.

Safety-related steam generator system and safety-related components in the control rod drive system are not identified as risk-significant in FSAR Table 17.4-1 These SSCs perform the same system functions in the US600 design and were identified as risk significant in the DCA.

Significant Changes from DCA to SDAA 22

Non-Proprietary NuScale SDAA FSAR Section 17.4 Review Augmented design requirements for EDAS are comparable with the design requirements for D-RAP SSCs.

SER Section 6.2.5 concludes that the safety classification of the PAR is acceptable.

The SGS and CRDS components are safety-related and subject to the requirements of the QAPD TR described in FSAR Section 17.5.

The staff finds that the design and quality requirements for EDAS, the PAR, SGS, and the safety-related CRDS components meet the intent of the Commission policy stated in item E of SECY-95-132.

resulting from the classification of SSCs is consistent with the intent of guidance in SRP Section 17.4.

Conclusion 23

Non-Proprietary Presentation to the ACRS Subcommittee Staff Review of NuScale SDAA FSAR, Revision 1 Chapter 19, Probabilistic Risk Assessment and Severe Accident Evaluation February 18, 2025 (Open Session) 24

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review NuScale submitted Chapter 19, Probabilistic Risk Assessment and Severe Accident Evaluation, Revision 0 of the NuScale SDAA FSAR on December 31, 2022, and Revision 1 on October 31, 2023 NRC regulatory audit of Chapter 19 was performed from March 2023 to August 2023, generating 173 audit issues Issues raised during the audit were resolved within the audit. 6 RAIs (15 Questions) were issued, and the responses were acceptable Staff completed Chapter 19 review and issued an advanced safety evaluation to support today's ACRS Subcommittee meeting Since providing draft SE to ACRS on 1/18/25, Table 19.1-4 was updated to include COL Item Nos. 19.1-7 and 19.1-8, which were inadvertently missed from the draft SE 25 Overview

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review Technical Reviewers

- Alissa Neuhausen, Branch Chief, NRR/DRA/APLC

- Marie Pohida, NRR/DRA/APLC

- Sunwoo Park, NRR/DRA/APLC

- Keith Tetter, NRR/DRA/APLC

- Michael Swim, NRR/DRA/APLC

- Anne-Marie Grady, NRR/DRA/APLC

- Steven Alferink, NRR/DRA/APLC

- George Wang, NRR/DEX/ESEB

- Thinh Dinh, NRR/DRA/APLB

- Ryan Nolan, NRR/DSS/SNRB 26 Contributors Project Managers

- Alina Schiller, PM, NRR/DNRL/NRLB

- Getachew Tesfaye, Lead PM, NRR/DNRL/NRLB

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review 19.1 Probabilistic Risk Assessment 19.2 Severe Accident Evaluation 19.3 Regulatory Treatment of Nonsafety Systems 19.4 Strategies and Guidance to Address Mitigation of Beyond-Design-Basis Events 19.5 Adequacy of Design Features and Functional Capabilities Identified and Described for Withstanding Aircraft Impacts 27 Sections

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review 28 Significant Changes to Risk Profile Between DCA and SDAA Core Damage Frequency (CDF)

CDF increased due to more frequent actuation of ECCS valves.

Dominant contributors to CDF include high winds, module drop, external floods, internal events, and internal fires.

Large Release Frequency (LRF)

LRF decreased due to earlier actuations of ECCS valves.

Contribution to LRF from breaks outside containment decreased.

Addition of digital reactor building crane control system minimizes operator error.

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review 29 Focus Areas for PRA and SA Review Impact of changed ECCS actuation setpoints Augmented DC power system (EDAS) modeling CVCS line breaks outside containment Unisolable CVCS breaks outside containment Density wave oscillation (DWO) impact on Steam Generator Tube Failure (SGTF)

Addition of reactor building crane (RBC) digital control system Top Support Structure (TSS) connection to RBC Addition of passive autocatalytic recombiner (PAR)

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review 30 Impact of ECCS Actuation Changes on CDF and LRF Approximately 90 percent of core damage scenarios involve incomplete ECCS actuation.

Low RCS level (top of the riser) and Low Low RCS level (mid-riser) result in earlier ECCS actuation.

8-hour ECCS timer added; Operator action to bypass timer after checking shutdown margin and hydrogen concentration found not to be a significant human action.

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review 31 EDAS Modeling in PRA ECCS reactor vent valves held closed by EDAS Not identified as risk significant from PRA importance measures.

Single failure proof system.

Physical separation between divisions.

Failure of two channels of module-specific EDAS results in reactor trip and ECCS actuation.

CCFs not modeled between electrical buses in separate compartments Data for EDAS CCF modeled in PRA is derived from operating plant data where DC power is safety-related FSAR states that EDAS will be included in the Owner Controlled Requirements Manual (OCRM) and the Maintenance Rule.

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review 32 CVCS line breaks outside containment Flow restricting venturis in injection and discharge lines control inventory loss and reduce LRF from CVCS line breaks outside of containment.

If at least one train of the DHRS is available and all ECCS valves are open, PRA success criteria are met.

Pumped injection via CFDS and CVCS is not needed for scenarios where all ECCS valves open in contrast to the DCA.

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review 33 Unisolable CVCS breaks outside containment The likelihood of weld failures at the junction between the containment vessel and the CVCS containment isolation valves are not modeled in the PRA.

The plant behavior and consequences of an unisolable CVCS LOCA outside of containment are modeled through the CVCS break downstream of containment isolation with failure of containment isolation.

The low weld failure frequency is identified as a key source of Level 2 uncertainty.

The impact on LRF is minimized by leak detection and operator response.

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review 34 DWO Impact on SGTF Initiating Event and PRA Results PRA did not explicitly model impact of DWO on SGTF.

Staff considered worst-case hypothetical impacts of DWO on PRA results.

Multiple SGTF Loss of both trains of DHRS NuScale sensitivity analyses demonstrate that the PRA results and insights are insensitive to the SGTF initiating event frequency and a loss of both trains of DHRS.

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review 35 RBC Control System Reduces Module Drop Contribution The RBC digital control system significantly decreases the contribution of operator errors of commission.

Dominant contributors to module drop are redundant load path failures (i.e., catastrophic gear box and wire rope failures)

The RBC digital control system is classified as non-safety related, risk significant, and SIL3.

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review 36 TSS Connection to Module Crane If a dropped module strikes an operating module, piping, including pressurizer spray piping and DHRS piping, at the front of the NPM has the potential to be impacted.

The safety-related CVCS CIVs location under the TSS protects these CIVs from postulated dropped NPM impacts.

The TSS is classified as non-safety related and risk significant in FSAR Table 17.4-1.

If the CIVs close but both trains of DHRS are unavailable, if one RSV successfully cycles open and closed, as needed, the RCS depressurizes, and the ECCS is demanded.

If the RSVs fail to open, ECCS functioning remains a success path.

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review A single safety-related passive autocatalytic recombiner (PAR) was added to the design.

The PAR is not modeled in the PRA.

Equipment survivability dose for PAR:

Post severe accident, the two functions that must be maintained are containment integrity and post-accident monitoring.

The PAR has been added to Table 19.2-8, Equipment Survivability List.

A new COL Item 19.2-4 states that the COL applicant will identify from Table 19.2-8, Equipment Survivability List, the components and their severe accident doses for cases in which the severe accident dose is greater than the EQ dose, as described in COL Item 19.2-4 37 Addition of PAR

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review 38 Conclusion Staff reviewed the NuScale US460 design-specific PRA and other PRA-related information in FSAR Section 19.1, in accordance with:

SRP Section 19.0.

DC/COL-ISG-028 for applicable modes and hazards The applicant addressed the full scope of internal and external initiating events for both full power and LPSD conditions.

The applicant developed quantitative risk insights for multi-module internal events and qualitative risk insights for multi-module shutdown and external events.

The PRA is of sufficient technical adequacy to support the SDA.

The staffs review concludes that the Commissions CDF and LRF goals have been met with margin.

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review H2 Combustion in the CNV The DCA addressed a potential combustion event in the CNV analytically and demonstrated that the CNV design pressure was not exceeded.

SDAA added a PAR which precludes combustion events from occurring during DBAs and SAs.

Containment Performance (no combustion)

SDAA Table 19.2-1, "Core Damage Simulations for SA Evaluation", identifies the spectrum of severe accidents that may challenge CNV integrity.

SDAA Tables 19.2 19.2-7 document that CNV design pressures, including H2 generated, are not exceeded.

Conclusion The applicant addressed severe accidents consistent with Commission policy.

SDAA design for containment performance meets:

the containment structural integrity criteria of RG 1.7, rev 3, "Control of Combustible Gas Concentrations in Containment."

the containment leak tight criteria of SECY-93-087.

39 Conclusion

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review 40 BDG Evaluation for RTNSS BDGs not scoped into RTNSS

1) Do not prevent the occurrence of an initiating event

2) Not needed for long-term, post-accident plant capabilities

3) Not needed to support defense-in-depth systems All components of the backup power supply system, including the BDG enclosures, are seismic Category III.

The BDG enclosure is rated for wind speeds in excess of the weather-related events considered in the LOOP initiating event.

Criterion C: SSC functions relied to meet the Commission goals for CDF < 1x10-4/yr and LRF < 1x10-6 /yr and SSCs needed to maintain initiating event frequencies at the comprehensive baseline PRA levels (SECY-94-084)

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review Staff has reviewed the NuScale US460 evaluation of RTNSS SSCs in FSAR Section 19.3, in accordance with:

SRP Section 19.3.

NuScale did not identify any SSCs in the scope of RTNSS.

Staff finds that no SSCs meet the criteria for requiring additional regulatory treatment.

41 Conclusion

Non-Proprietary NuScale SDAA FSAR Chapter 19 Review Adequacy of Design Features and Functional Capabilities Identified and Described for Withstanding Aircraft Impacts: Structural Steel-Plate Composite Walls (only applicable to SDAA)

Both global and local assessment use experimental data to benchmark the methodology and results Followed NEI 07-13, Revision 8 with no exceptions Additional key design features (only applicable to SDAA)

Strengthen SC wall to RC slab connections Local detailing with tie rods in SC wall-to-wall connection Structural steel beam seat connections along RX-B and RX-D Credit RWB as Intervening Structure to limit potential strike locations to the west end of the RXB (only applicable to DCA) 42 Aircraft Impact Analysis

Non-Proprietary TOPIC - 5 Principles of Risk Informed Decisionmaking Principle 1: Meets current regulations or exemption requested

• Yellow indicates applicant/licensee has provided some information on the topic.

Staff still needs information, but theres a clear path forward.

Principle 2: Consistent with the defense-in-depth philosophy

• Green indicates that all reviewers agree that applicant/licensee has provided sufficient information.

• E.g., backup systems that are available to mitigate the event Principle 3: Maintains sufficient safety margins

• Red indicates that there is broad agreement that applicant/licensee did not provide information to make a regulatory finding. There is no clear path forward.

Principle 4: Increase in risk is small and consistent with the intent of the Commissions Safety Goal Policy Statement

• Integrated review team is established among technical review branches and risk analysts to align on a decision considering all 5 principles of RIDM.

Principle 5: Performance measurement strategies available for monitoring Integrated Review Approach - Communication Tool

Non-Proprietary Acronyms LOOP LRF NPM OCRM PAR PRA RBC RCS RSV RTNSS SBO SDAA SGTF SRP TSS Backup Diesel Generator Common Cause Failure Core Damage Frequency Containment Flood and Drain System Containment Isolation Valve Combined License Chemical and Volume Control System Design Certification Application Decay Heat Removal System Density Wave Oscillations Emergency Core Cooling System Augmented DC Power System Equipment Qualification Final Safety Analysis Report Loss of Coolant Accident BDG CCF CDF CFDS CIV COL CVCS DCA DHRS DWO ECCS EDAS EQ FSAR LOCA Loss of Offsite Power Large Release Frequency Nuclear Power Module Owner Controlled Requirements Manual Passive Autocatalytic Recombiner Probabilistic Risk Assessment Reactor Building Crane Reactor Coolant System Reactor Safety Valve Regulatory Treatment for Non-Safety-Systems Station Blackout Standard Design Approval Application Steam Generator Tube Failure Standard Review Plan Top Support Structure