ML22284A144

Issuance of Amendment No. 200 Regarding the Revision of Methodology Used for Flood Hazard Analysis

ML22284A144
Person / Time
Site:	Perry
Issue date:	02/03/2023
From:	Scott Wall Plant Licensing Branch III
To:	Penfield R Energy Harbor Nuclear Corp
Wall S
References
EPID L-2021-LLA-0067
Download: ML22284A144 (28)

Text

February 3, 2023 Mr. Rod L. Penfield Site Vice President Energy Harbor Nuclear Corp.

Perry Nuclear Power Plant P.O. Box 97, SB306 Perry, OH 44081-0097

SUBJECT:

PERRY NUCLEAR POWER PLANT, UNIT NO. 1 - ISSUANCE OF AMENDMENT NO. 200 REGARDING THE REVISION OF METHODOLOGY USED FOR FLOOD HAZARD ANALYSIS (EPID L-2021-LLA-0067)

Dear Mr. Penfield:

The U.S. Nuclear Regulatory Commission (the Commission) has issued the enclosed Amendment No. 200 to Facility Operating License No. NPF-58 for Perry Nuclear Power Plant, Unit No. 1 (Perry). The amendment consists of changes to the Perry technical specifications (TSs) and Updated Safety Analysis Report (USAR) in response to your application dated April 7, 2021 (Agencywide Documents Access and Management System Accession No. ML21106A027), as supplemented by letters dated August 17, 2021, June 1, 2022, and December 16, 2022 (ML21237A075, ML22152A180, and ML22350A798, respectfully).

The amendment revises the methodology used for analysis of flooding hazards and drainage within the local intense precipitation domain and reflects the results of the new flood hazard protection scheme in the USAR. The amendment also adds a new limiting condition for operation to the TSs as TS 3.7.11, Flood Protection, and makes conforming changes to the TS Table of Contents.

A copy of the related Safety Evaluation is also enclosed. A Notice of Issuance will be included in the Commissions monthly Federal Register notice.

Sincerely,

/RA/

Scott P. Wall, Senior Project Manager Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-440

Enclosures:

1. Amendment No. 200 to NPF-58

2. Safety Evaluation cc: Listserv

ENERGY HARBOR NUCLEAR CORP.

ENERGY HARBOR NUCLEAR GENERATION, LLC DOCKET NO. 50-440 PERRY NUCLEAR POWER PLANT, UNIT NO. 1 AMENDMENT TO FACILITY OPERATING LICENSE Amendment No. 200 License No. NPF-58

1.

The Nuclear Regulatory Commission (NRC, the Commission) has found that:

A.

The application for amendment filed by Energy Harbor Nuclear Corp., et al.,1 dated April 7, 2021, as supplemented by letters dated August 17, 2021, June 1, 2022, and December 16, 2022, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commissions rules and regulations as set forth in 10 CFR Chapter I; B.

The facility will operate in conformity with the application, the provisions of the Act, and the rules and regulations of the Commission; C.

There is reasonable assurance (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commissions regulations; D.

The issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public; and E.

The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commissions regulations and all applicable requirements have been satisfied.

1 Energy Harbor Nuclear Corp. is authorized to act as agent for Energy Harbor Nuclear Generation, LLC and has exclusive responsibility and control over the physical construction, operation, and maintenance of the facility.

2.

Accordingly, the license is amended by changes to the Technical Specifications, as indicated in the attachment to this license amendment, and paragraph 2.C.(2) of Facility Operating License No. NPF-58 is hereby amended to read as follows:

(2)

Technical Specifications The Technical Specifications contained in Appendix A and the Environmental Protection Plan contained in Appendix B, as revised through Amendment No. 200, are hereby incorporated into the license.

Energy Harbor Nuclear Corp. shall operate the facility in accordance with the Technical Specifications and the Environmental Protection Plan.

3.

Accordingly, by Amendment No.200, the license is amended to authorize revision to the Updated Safety Analysis Report (USAR), as set forth in the application, as supplemented, and as evaluated in the NRC staffs safety evaluation issued with this amendment.

4.

This license amendment is effective as of its date of its issuance and shall be implemented within 180 days of the date of issuance. The USAR changes shall be implemented in the next periodic update to the USAR in accordance with 10 CFR 50.71(e).

FOR THE NUCLEAR REGULATORY COMMISSION Nancy L. Salgado, Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Attachment:

Changes to the Facility Operating License No. NPF-58 and Technical Specifications Date of Issuance: February 3, 2023 Joel S.

Wiebe Digitally signed by Joel S.

Wiebe Date: 2023.02.03 15:10:07 -05'00'

ATTACHMENT TO LICENSE AMENDMENT NO. 200 PERRY NUCLEAR POWER PLANT, UNIT NO. 1 FACILITY OPERATING LICENSE NO. NPF-58 DOCKET NO. 50-440 Facility Operating License No. NPF-58 Replace the following page of Facility Operating License No. NPF-58 with the attached revised page. The revised page is identified by amendment number and contains a marginal line indicating the area of change REMOVE INSERT Technical Specifications Replace the following pages of the Appendix A, Technical Specifications, with the attached revised pages. The revised pages are identified by amendment number and contain marginal lines indicating the areas of change.

REMOVE INSERT TOC iii and iv TOC iii and iv 3.7-21 3.7-22 Amendment No. 199, 200 C. This license shall be deemed to contain and is subject to the conditions specified in the Commissions regulations set forth in 10 CFR Chapter I and is subject to all applicable provisions of the Act and to the rules, regulations, and orders of the Commission now or hereafter in effect; and is subject to the additional conditions specified or incorporated below:

(1)

Maximum Power Level Energy Harbor Nuclear Corp. is authorized to operate the facility at reactor core power levels not in excess of 3758 megawatts thermal (100% power) in accordance with the conditions specified herein.

(2)

Technical Specifications The Technical Specifications contained in Appendix A and the Environmental Protection Plan contained in Appendix B, as revised through Amendment No. 200, are hereby incorporated into the license. Energy Harbor Nuclear Corp. shall operate the facility in accordance with the Technical Specifications and the Environmental Protection Plan.

(3)

Antitrust Conditions

a. Energy Harbor Nuclear Generation LLC shall comply with the antitrust conditions delineated in Appendix C to this license; Appendix C is hereby incorporated into this license.

PERRY - UNIT 1 iii Amendment No. 200 TABLE OF CONTENTS 3.6 CONTAINMENT SYSTEMS (continued) 3.6.2.2 Suppression Pool Water Level 3.6-39 3.6.2.3 Residual Heat Removal (RHR) Suppression Pool Cooling.. 3.6-40 3.6.2.4 Suppression Pool Makeup (SPMU) System. 3.6-42 3.6.3.1 Deleted 3.6.3.2 Primary Containment and Drywell Hydrogen Igniters. 3.6-46 3.6.3.3 Combustible Gas Mixing System... 3.6-49 3.6.4.1 Secondary Containment.. 3.6-51 3.6.4.2 Secondary Containment Isolation Valves (SCIVs).. 3.6-53 3.6.4.3 Annulus Exhaust Gas Treatment (AEGT) System.. 3.6-56 3.6.5.1 Drywell 3.6-59 3.6.5.2 Drywell Air Lock 3.6-61 3.6.5.3 Drywell Isolation Valves.. 3.6-65 3.6.5.4 Drywell Pressure... 3.6-69 3.6.5.5 Drywell Air Temperature.. 3.6-70 3.6.5.6 Drywell Vacuum Relief System. 3.6-71 3.7 PLANT SYSTEMS 3.7.1 Emergency Service Water (ESW) System - Divisions 1 and 2 3.7-1 3.7.2 Emergency Service Water (ESW) System - Division 3. 3.7-3 3.7.3 Control Room Emergency Recirculation (CRER) System.... 3.7-4 3.7.4 Control Room Heating, Ventilation, and Air Conditioning (HVAC)

System.... 3.7-8 3.7.5 Main Condenser Offgas.. 3.7-11 3.7.6 Main Turbine Bypass System. 3.7-13 3.7.7 Fuel Pool Water Level.. 3.7-14 3.7.8 Deleted 3.7.9 Deleted 3.7.10 Emergency Closed Cooling Water (ECCW) System.. 3.7-19 3.7.11 Flood Protection 3.7-21 3.8 ELECTRICAL POWER SYSTEMS 3.8.1 AC Sources - Operating. 3.8-1 3.8.2 AC Sources - Shutdown. 3.8-17 3.8.3 Diesel Fuel Oil, Lube Oil, and Starting Air 3.8-21 3.8.4 DC Sources - Operating. 3.8-24 3.8.5 DC Sources - Shutdown. 3.8-28 3.8.6 Battery Parameters.. 3.8-32 3.8.7 Distribution Systems - Operating.. 3.8-36 3.8.8 Distribution Systems - Shutdown.. 3.8-38 3.9 REFUELING OPERATIONS 3.9.1 Refueling Equipment Interlocks. 3.9-1 3.9.2 Refuel Position One-Rod-Out Interlock... 3.9-2 3.9.3 Control Rod Position... 3.9-4 (continued)

PERRY - UNIT 1 iv Amendment No. 200 TABLE OF CONTENTS 3.9 REFUELING OPERATIONS (continued) 3.9.4 Control Rod Position Indication.... 3.9-5 3.9.5 Control Rod OPERABILITY - Refueling. 3.9-7 3.9.6 Reactor Pressure Vessel (RPV) Water Level - Irradiated Fuel.. 3.9-8 3.9.7 Reactor Pressure Vessel (RPV) Water Level - New Fuel or Control Rods... 3.9-9 3.9.8 Residual Heat Removal (RHR) - High Water Level.. 3.9-10 3.9.9 Residual Heat Removal (RHR) - Low Water Level... 3.9-13 3.10 SPECIAL OPERATIONS 3.10.1 Inservice Leak and Hydrostatic Testing Operation 3.10-1 3.10.2 Reactor Mode Switch Interlock Testing 3.10-4 3.10.3 Single Control Rod Withdrawal - Hot Shutdown 3.10-6 3.10.4 Single Control Rod Withdrawal - Cold Shutdown. 3.10-9 3.10.5 Single Control Rod Drive (CRD) Removal - Refueling 3.10-13 3.10.6 Multiple Control Rod Withdrawal - Refueling.. 3.10-16 3.10.7 Control Rod Testing - Operating.. 3.10-18 3.10.8 SHUTDOWN MARGIN (SDM) Test - Refueling 3.10-19 3.10.9 Suppression Pool Makeup - MODE 3 Upper Containment Pool Drain-Down 3.10-23 4.0 DESIGN FEATURES 4.1 Site Location 4.0-1 4.2 Reactor Core 4.0-1 4.3 Fuel Storage. 4.0-2 5.0 ADMINISTRATIVE CONTROLS 5.1 Responsibility.. 5.0-1 5.2 Organization. 5.0-2 5.3 Unit Staff Qualifications.. 5.0-4 5.4 Procedures 5.0-5 5.5 Programs and Manuals.. 5.0-6 5.6 Reporting Requirements 5.0-16 5.7 High Radiation Area 5.0-19

Flood Protection 3.7.11 PERRY - UNIT 1 3.7-21 Amendment No. 200 3.7 PLANT SYSTEMS 3.7.11 Flood Protection LCO 3.7.11 Flood protection shall be provided for safety-related systems, structures, and components via deployment of flood barriers at a meteorological Trigger Event warning.

APPLICABILITY:

At all times.

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. Requirements of the LCO not met.

A.1 Deploy flood barriers.

Prior to being within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> of projected start of the Trigger Event B. Required Action and associated Completion Time of Condition A not met in MODE 1, 2, or 3.

B.1 Be in MODE 3.

AND B.2 Be in MODE 4.

12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> 36 hours C. Required Action and associated Completion Time of Condition A not met in other than MODE 1, 2, or 3.

C.1 Suspend CORE ALTERATIONS except for control rod insertion.

AND C.2 Initiate action to fully insert all insertable control rods in core cells containing one or more fuel assemblies.

AND Immediately Immediately (continued)

Flood Protection 3.7.11 PERRY - UNIT 1 3.7-22 Amendment No. 200 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME C. (continued)

C.3 Initiate action to restore primary containment to OPERABLE status.

AND C.4 Initiate action to restore isolation capability in each required primary containment penetration flow path not isolated.

AND

---

NOTE-------------

Entry and exit is permissible under administrative control.

C.5 Initiate action to close one door in each primary containment air lock.

1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> 1 hour 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.7.11.1 Monitor 7-day meteorological forecast for Trigger Event.

24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 200 TO FACILITY OPERATING LICENSE NO. NPF-58 ENERGY HARBOR NUCLEAR CORP.

ENERGY HARBOR NUCLEAR GENERATION LLC PERRY NUCLEAR POWER PLANT, UNIT NO. 1 DOCKET NO. 50-440

1.0 INTRODUCTION

By letter dated April 7, 2021 (Agencywide Documents Access and Management System Accession No. ML21106A027), as supplemented by letters dated August 17, 2021, June 1, 2022, and December 16, 2022 (ML21237A075, ML22152A180, and ML22350A798, respectfully), Energy Harbor Nuclear Corp. (EHNC, the licensee) submitted to the U.S. Nuclear Regulatory Commission (NRC, the Commission) a license amendment request (LAR) for the Perry Nuclear Power Plant, Unit No. 1 (PNPP) that would revise the methodology used for analysis of flooding hazards and drainage within the local intense precipitation (LIP) domain and reflect the results of the new flood hazard protection scheme in the Updated Safety Analysis Report (USAR); and would add a new limiting condition for operation (LCO) to the technical specifications (TSs) as TS 3.7.11, Flood Protection, and make conforming changes to the TS Table of Contents.

The April 7, 2021, application also contained two specific exemption requests to credit non-safety-related protection features including: (1) permanent (passive) and temporary (deployable) flood barriers and (2) the plant storm drain system in mitigation of flood levels during a LIP event. On October 31, 2022, a clarification call conference was held between EHNC and the NRC staff regarding draft staff requests for additional information (RAIs) pertaining to the two specific exemption requests. By "L-22-272, Supplement to License Amendment Request to Revise the Methodology Used for Flood Hazard Analysis (EPID L-2021-LLA-0067) and Withdrawal of Exemption Requests (EPIDs L-2021-LLE-0022 and [[Project reference" contains a listed "[" character as part of the property label and has therefore been classified as invalid.)|letter dated December 16, 2022]], EHNC withdrew both exemption requests.

The NRC staff participated in a virtual regulatory audit from July 25, 2021, to March 31, 2022 (ML21165A001), to ascertain the information needed to support its review of the application and to develop RAIs, as needed. During the audit, the staff identified a potential issue regarding the procedure for implementing flood protection barriers in the event of a LIP event. On May 6, 2022, the staff issued an audit summary (ML22101A282).

On July 6, 2021, the NRC published a notice of consideration of approval of the application in the Federal Register (86 FR 35544). The supplemental letter dated June 1, 2022, provided additional information that expanded the scope of the application as originally noticed.

Therefore, the NRC published a notice of consideration of approval of the application, as supplemented, in the Federal Register on July 15, 2022 (87 FR 42505). The supplemental "L-22-272, Supplement to License Amendment Request to Revise the Methodology Used for Flood Hazard Analysis (EPID L-2021-LLA-0067) and Withdrawal of Exemption Requests (EPIDs L-2021-LLE-0022 and [[Project reference" contains a listed "[" character as part of the property label and has therefore been classified as invalid.)|letter dated December 16, 2022]], provided additional information that clarified the application, did not expand the scope of the application as noticed, and did not change the NRC staffs proposed no significant hazards consideration determination as published in the Federal Register on July 15, 2022 (87 FR 42505).

1.1 Background

1.1.1 Original and Existing Site Condition The PNPP site was previously classified as a dry site according to the definition in Regulatory Guide (RG) 1.102, Flood Protection for Nuclear Power Plants, Revision 1, dated September 1976 (ML003740308). The safety-related structures of the plant are located within an isolated drainage area. The floors at plant grade are nominally set at Elevation (EL) 620 feet (ft) 6 inches. Under the existing analysis, the controlling flood and associated water levels impacting the PNPP site are a result of the surface drainage capabilities during the current LIP event. Plant flooding by LIP was prevented by the design of the storm drainage system and roof drainage system, which is hydraulically coupled to the storm drainage system.

In case of complete blockage of the storm drainage system, the PNPP site has been graded so that overland drainage will begin once ponding has reached EL 620 ft 4 inches. Assuming the worst-case scenario (that is, complete blockage of the site storm drainage system and using peak discharge from the most intense hour of the probable maximum precipitation (PMP)), the resulting increase in surface elevation of water flowing over the surrounding roads and railroads (acting as weirs) on site would not exceed one inch. Therefore, the ponding level of EL 620 ft 5 inches provided a one-inch margin over the nominal floor levels at plant grade of EL 620 ft 6 inches.

The PNPP site is in a coastal watershed that drains into Lake Erie. The mean lake level is more than 40 ft below the plant grade. Two parallel streams run adjacent to the plant area. The larger stream designated by the licensee as the Major Stream has a drainage basin area of 7.2 square miles and runs northwestward within 1,000 ft of the southwest corner of the plant property. The Major Stream is a natural stream and was incorporated into the original plant construction. The smaller stream designated by the licensee as the Minor Stream, diverted by a diversion channel (Diversion Channel or Diversion Stream) as described in the LAR, has a drainage area of 0.8 square miles, runs northward, and is located to the east of the plant. The Diversion Channel for the Minor Stream was not installed during the original plant construction.

1.1.2 Site Condition Changes and Methodology Changes for Flood Hazard Analysis On March 12, 2012, the NRC issued a letter to all power reactor licensees and holders of construction permits in active or deferred status titled Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident (ML12053A340) (hereafter, 10 CFR 50.54(f) letter). During the development of its response to the 10 CFR 50.54(f) letter, the licensee was unable to locate certain analyses supporting the PNPP USAR discussions regarding external flooding hazards. To verify water levels over the LIP domain based on the as-found site configuration, another study calculation was prepared.

The licensee indicated that changes to the immediate and local PNNP site area throughout the life of the facility have occurred. Those changes have influenced the hydrologic condition at the site. The licensee analyzed floods in three different areas due to the changes: (1) the entire plant site was analyzed for a LIP event, (2) the Major Stream area adjacent to the southwest portion of the plant site was analyzed under updated PMF conditions, and (3) the Minor Stream area adjacent to the northeast was evaluated under updated PMF conditions. The safety-related structures of PNPP are located within the drainage basin of the LIP domain (the first area).

In the LIP domain, the licensee indicated that changes such as the installation of various security features, including the vehicle barrier system and jersey barriers, as well as the multi-layered perimeter fence, have affected the runoff characteristics of overland flow and its discharge out of the LIP domain. In addition, several plant buildings have been erected since license issuance, including the Administration Building, Service Building Annex, security access structures, and portions of the Warehouse. Site improvement initiatives, such as the paving of previously grass and gravel areas, have altered the drainage patterns and runoff coefficients. To accommodate the various changes and evolving drainage characteristics, extensions and additions to the storm drain system have occurred.

In the Major Stream area, which is the second area in the licensees analysis, the licensee modified the stream embankment at the railway bridge and raised the plant access road to avoid flood flow over the railway and the road. The embankment modification can release some flood flow into the flood plain. In the Minor Stream area, which is the third area in the licensees analysis, the licensee installed the Diversion Channel to convey the upstream flow away from the plant site and discharge the flood flow directly into Lake Erie. The changes in the Major Stream and Minor Stream areas were made because of the reevaluated external flooding hazards in response to the 10 CFR 50.54(f) letter.

The simple methodology previously used for establishing the USAR-described LIP flood for the LIP domain cannot account for the cumulative effect of the PNPP site condition changes.

Therefore, the licensee used new methodologies to analyze the LIP flood within the LIP domain, as well as PMF within the Major Stream and Minor Stream areas. Since the modification of the stream channel embankment in the Major Stream area and the installation of the Diversion Channel in the Minor Stream area are part of the flood protection improvement for the plant, and are part of the results in response to the 10 CFR 50.54(f) letter, the licensee included them in the LAR as part of the site condition changes.

2.0 REGULATORY EVALUATION

2.1 Description of Proposed License Change To address the changes related to external flooding events at the PNPP, the licensee elected to reconstitute the design basis analyses for the LIP domain using a more appropriate methodology (i.e., a two-dimensional unsteady state model, FLO-2D Pro software computer program) and implement site modifications to alleviate the reconstituted flood hazards. Also, in response to the reconstituted hydrologic analysis, the licensee revised the flood hazard protection scheme for the site.

For the LIP event, which represents the bounding external flood hazard for PNPP, protection is provided via a combination of permanent and temporary incorporated barriers. Structures, systems, and components (SSCs) required to achieve and maintain cold shutdown are only passively protected up to and including the effects of the Standard Project Storm (SPS). For

hazards exceeding the SPS, up to and including the PMP event of the LIP domain, operator action is required to deploy protection features. Operator action is limited to the deployment of removable incorporated barriers in the form of flooding stop logs. The requirements and guidance for this action are incorporated into plant off-normal instructions. Entry into the plant off-normal instructions is initiated by a meteorological forecast warning. This action is required by the proposed new PNPP TS 3.7.11. If barriers are not deployed in the timeframe allotted by this TS, a plant shutdown is required to be initiated.

Under the reconstituted LIP flood hazard results, a new methodology is also used to address flood-borne missiles. These missiles were not previously considered. The proposed revised PNPP USAR Section 3.5.1.4, Missiles Generated by Natural Phenomena, would include a discussion of flood-borne missiles.

2.2 Flood Protection Licensing Basis PNPP was designed to meet the General Design Criteria (GDC) in Appendix A, General Design Criteria for Nuclear Power Plants, to 10 CFR Part 50, Domestic Licensing of Production and Utilization Facilities, including GDC 1, Quality standards and records, GDC 2, Design bases for protection against natural phenomena, and GDC 4, Environmental and dynamic effects design bases. The current licensing basis for flood protection is contained in Section 2.4, Hydrologic Engineering, of the PNPP USAR (ML21361A222). The design parameters applicable to the design basis flooding are found in USAR Section 2.3, Meteorology. Table 1.8-1, Conformance to NRC Regulatory Guides, of USAR Chapter 1 (ML21307A198) discusses the licensees conformance to the relevant regulatory guides related to flood protection.

2.3 Applicable Regulatory Requirements 2.3.1 Limiting Conditions for Operation and Surveillance Requirements The regulation at 10 CFR 50.36(b) states, in part, that:

Each license authorizing operation of a utilization facility will include technical specifications. The technical specifications will be derived from the analyses and evaluation included in the safety analysis report, and amendments thereto, submitted pursuant to [10 CFR] 50.34 [Contents of applications; technical information]. The Commission may include such additional technical specifications as the Commission finds appropriate.

In 10 CFR 50.36, Technical specifications, the Commission established its regulatory requirements related to the content of TSs. Pursuant to 10 CFR 50.36, TSs are required to include items in the following categories related to station operation: (1) safety limits, limiting safety system settings, and limiting control settings; (2) LCOs; (3) surveillance requirements (SRs); (4) design features; and (5) administrative controls. The rule does not specify the specific requirements to be included in a plants TSs. The regulation also states, in part, that [a]

summary statement of the bases or reasons for such specifications, other than those covering administrative controls, shall also be included in the application, but shall not become part of the technical specifications.

As stated in 10 CFR 50.36(c)(2)(i), Limiting conditions for operation are the lowest functional capability or performance levels of equipment required for safe operation of the facility. When a

limiting condition for operation of a nuclear reactor is not met, the licensee shall shut down the reactor or follow any remedial action permitted by the technical specifications until the condition can be met.

10 CFR 50.36(c)(2)(ii) states that an LCO of a nuclear reactor must be established for each item meeting one or more of the following criteria:

(A)

Criterion 1. Installed instrumentation that is used to detect, and indicate in the control room, a significant abnormal degradation of the reactor coolant pressure boundary.

(B)

Criterion 2. A process variable, design feature, or operating restriction that is an initial condition of a design basis accident or transient analysis that either assumes the failure of or presents a challenge to the integrity of a fission product barrier.

(C) Criterion 3. A structure, system, or component that is part of the primary success path and which functions or actuates to mitigate a design basis accident or transient that either assumes the failure of or presents a challenge to the integrity of a fission product barrier.

(D) Criterion 4. A structure, system, or component which operating experience or probabilistic risk assessment has shown to be significant to public health and safety.

10 CFR 50.36(c)(3) requires TSs to include SRs, which are requirements relating to test, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the LCOs will be met.

2.3.2 General Design Criteria 10 CFR Part 50, Appendix A, GDC 1, is related to quality standards and codes and states, in part, that SSCs important to safety must be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the safety functions to be performed.

10 CFR Part 50, Appendix A, GDC 2, is related to consideration of the most severe of the natural phenomena that have been historically reported for the site and surrounding area, with sufficient margin for the limited accuracy, quantity, and period of time in which the historical data have been accumulated.

10 CFR Part 50, Appendix A, GDC 4, is related to the ability of SSCs important to safety to be protected from dynamic effects, including the effects of missiles, from events and conditions outside the nuclear power unit.

2.3.3 Other Regulations 10 CFR 100.10(c) is for factors to be considered when evaluating sites and the physical characteristics of the site, including seismology, meteorology, geology, and hydrology.

10 CFR Part 50, Appendix B, Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants, establishes quality assurance requirements for the design, manufacture, construction, and operation of nuclear power plant SSCs that prevent or mitigate the consequences of postulated accidents that could cause undue risk to public health and safety.

The pertinent requirements of Appendix B apply to all activities affecting the safety-related functions of those SSCs.

Under 10 CFR 50.90, Application for amendment of license, construction permit, or early site permit, whenever a holder of a license wishes to amend the license, including technical specifications in the license, an application for amendment must be filed, fully describing the changes desired. Under 10 CFR 50.92(a), determinations of whether to grant an applied for license amendment are to be guided by the considerations that govern the issuance of initial licenses to the extent applicable and appropriate. Both the common standards for licenses in 10 CFR 50.40(a), and those specifically for the issuance of operating licenses in 10 CFR 50.57(a)(3), generally provide that there must be reasonable assurance that the activities at issue will not endanger the health and safety of the public, and that the applicant will comply with the Commissions regulations.

2.4 Applicable Regulatory Guidance 2.4.1 Standard Review Plan NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR [Light-Water Reactor] Edition (SRP), establishes criteria that the NRC staff uses in evaluating whether a licensee meets the NRCs regulations.

Section 2.4.2, Floods, Revision 4, dated March 2007 (ML070100647), is related to hydrologic engineering and flood analysis, and it also covers the potential effects of LIP.

Section 2.4.3, Probable Maximum Flood (PMF) on Streams and Rivers, Revision 4, dated March 2007 (ML070730405), is related to the hydrometeorological design basis that is developed to determine the extent of any flood protection required for those SSCs necessary to ensure the capability to shut down the reactor and to maintain it in a safe shutdown condition.

Section 2.4.10, Flooding Protection Requirements, Revision 3, dated March 2007 (ML070730437), is related to the flood protection requirements for the safety-related SSCs.

Section 2.4.14, Technical Specifications and Emergency Operation Requirements, Revision 3, dated March 2007 (ML070730455), is related to the actions specified in the TSs to shut down the plant and take appropriate emergency measures when the site is susceptible to flooding.

Section 16.0, Technical Specifications, Revision 3, dated March 2010 (ML100351425), is related to consistency with the applicable Standard Technical Specifications (STSs) for each of the LWR nuclear designs. The current STS that is applicable to the PNPP is NUREG-1434, Standard Technical Specifications, General Electric BWR/6 Plants, Volume 1, Specifications, and Volume 2, Bases, Revision 5.0, dated September 2021 (ML21271A582 and ML21271A596, respectively).

2.4.2 Standard Technical Specifications As described in the SRP, as part of the regulatory standardization effort, the NRC staff has prepared STSs for each of the LWR nuclear designs. Accordingly, the staffs review includes consideration of whether the proposed changes are consistent with the applicable STSs, as modified by NRC-approved changes called travelers. In addition, the guidance states that comparing the proposed changes to previous STSs can help clarify the TS intent. The current STS that is applicable to the licensees facility is NUREG-1434, Revision 5.0.

2.4.3 Regulatory Guides RG 1.29, Seismic Design Classification for Nuclear Power Plants, Revision 6, dated July 2021 (ML21155A003), describes a method of identifying and classifying those features of LWR nuclear power plants that must be designed to withstand the effects of the safe-shutdown earthquake (SSE)

RG 1.59, Design Basis Floods for Nuclear Power Plants, Revision 2, dated August 1977 (ML003740388), describes acceptable methods for determining the design basis flood conditions that nuclear power plants located on sites along streams must withstand without a loss of safety-related functions.

Regulatory Position C.1 states, in part, that:

The conditions resulting from the worst site-related flood probable at a nuclear power plant with attendant wind-generated wave activity constitute the design basis flood conditions that safety-related [SSCs]

identified in [RG] 1.29 must be designed to withstand and retain capability for cold shutdown and maintenance thereof.

Regulatory Position C.2 provides discussion of an alternative to designing hardened protection for all safety-related SSCs. Hardened protection is described as meaning structural provisions incorporated in the plant design that will protect SSCs from the static and dynamic effects of floods. Each component of the protection must be passive and in place, as it is to be used for flood protection, during normal plant operation. It is permissible not to provide hardened protection for some of these features if sufficient warning time is shown to be available to shut the plant down and implement adequate emergency procedures.

Regulatory Position C.3 states, in part, that:

Significantly adverse changes in the runoff or other flood-producing characteristics of the site environs, as they affect the design basis flood, should be identified and used as the basis to develop or modify emergency operating procedures, if necessary, to mitigate the effects of the increased flood.

RG 1.102 describes types of flood protection acceptable to the NRC for the safety-related SSCs identified in RG 1.29. In addition, RG 1.102 describes acceptable methods of protecting nuclear power plants from the effects of PMP falling directly on the site. The definition of PMP is contained in RG 1.59. PMP is the estimated depth for a given duration, drainage area, and time of year for which there is virtually no risk of exceedance. The PMP for a given duration and

drainage area approaches and approximates the maximum that is physically possible within the limits of contemporary hydrometeorological knowledge and techniques.

3.0 TECHNICAL EVALUATION

3.1 Flood Protection Scheme and Structural Design 3.1.1 Alignment with Regulatory Guidelines The licensee indicated that, as indicated in PNPP USAR Section 2.4, the design of PNPP for flood protection conforms to the guidelines of RG 1.102, Regulatory Position C.1, and RG 1.59, Regulatory Positions C.1 and C.2. No exceptions to the guidance in these two regulatory guides have previously been taken. Regulatory Position C.2 in RG 1.59 provides an alternative to designing hardened protection for all safety-related SSCs. Hardened protection is described as meaning structural provisions incorporated in the plant design that will protect SSCs from the static and dynamic effects of floods. Each component of the protection must be passive and in place, as it is to be used for flood protection, during normal plant operation. It is permissible in Regulatory Position C.2 not to provide hardened protection for some of these features if sufficient warning time is shown to be available to shut the plant down and implement adequate emergency procedures, while safe shutdown SSCs remain fully passively protected.

The reconstituted LIP flood levels necessitated a fundamental change to the protection scheme for the LIP event at the PNPP site. Potential flood waters now exceeded door thresholds of safety-related buildings and non-safety environmental interfaces. Therefore, deployable flood barriers for doorways are required to protect the structures from inundation. A non-safety-related building (structure) is considered an environmental interface to a safety-related building if external floodwaters would enter the safety-related building if the existence of all or part of the non-safety-related building was removed. Where water levels exceed either door thresholds, wall penetrations, or rise above the first-floor grade of a building, flood protection is necessary to meet the requirements of incorporated barriers as defined in RG 1.102.

Flood panels (stop logs) are proposed to be used at the PNPP site to provide flood protection at doorways where flood levels exceed their thresholds. The stop logs used as flood barriers would provide protection from flood waters up to approximately 2 ft in height. This is adequate to prevent water intrusion into the door with the maximum water depth (approximately 1.625 ft).

The licensee stated that all flood panels and door threshold ramps that are considered incorporated barriers have been analyzed and designed to protect against the static and dynamic forces and, where applicable, the missiles generated during the postulated event.

Therefore, the licensee determined that the use of incorporated barriers to prevent floodwaters from entering SSCs during a LIP event meets the intent of RG 1.102. The licensee also proposed an inspection plan that would require periodic inspections of the material condition of the flood barriers, including the gasketed sealing surfaces. The inspection plan would also ensure that the channels are free of any material that could interfere with barrier deployment or mating surfaces. Furthermore, the barriers would be added to the Plant Operator Rounds or other applicable periodic activity. In this way, the barriers would be confirmed to be staged at the designated locations, thus ensuring deployment readiness. Temporary incorporated barriers would be required to be located at the exterior doors of plant buildings that, in some locations, function as normal ingress and egress paths. For all man doors and some rollup doors, the doors function as emergency exits for plant personnel and may function as emergency entrances (such as for medical first responders or fire brigade members). Using permanent incorporated barriers (that is, leaving the flood panels in place during normal operation) would

result in a safety hazard for plant personnel. Therefore, for these instances, an advance warning time would be incorporated into the flood hazard protection scheme. Safety-related features located within the PNPP site would be protected up to and including the SPS using passive (permanent or normally installed) flood protection barriers. For any precipitation event larger than the SPS, including the PMP event, permanent barriers and removable flood panels would be used.

RG 1.59, Regulatory Position C.2.d, states that, in addition to Position C.2.b, at least those SSCs necessary for cold shutdown and maintenance thereof are designed with hardened protective features to remain functional while withstanding the entire range of flood conditions up to the PMP. Hardened protection is a structural provision that is passive and in place during normal plant operation, intended to protect SSCs from the static and dynamic effects of floods.

As described above, the proposed PNPP flood hazard protection scheme includes the use of passive flood protection barriers to mitigate the effects of all storms up to and including the SPS.

While not entirely permanent, the barriers are normally installed at the required location. For flood protection in response to storms in excess of the SPS, up to and including the PMP, temporary incorporated barriers are proposed to be deployed. Because the barriers would not be in place during normal plant operation, they are not considered hardened protection. The concept of using an advanced warning alert in response to flood protection, where sufficient warning time is available to bring the plant to a safe shutdown condition, is considered within RG 1.102. For PNPP, the proposed new flood hazard protection scheme includes a two-tier meteorological alert used to initiate deployment of temporary flood barriers. The first-tier alert of 2.1 inches of precipitation in a 24-hour period is used to initiate heightened awareness of plant personnel. The second-tier alert of 1.9 inches of precipitation in a one-hour period serves as the initial condition for entry into plant off-normal instructions, which include deployment of temporary flood barriers. Due to the changes in watershed discussed in this safety evaluation and the unusual circumstances leading to this issue at PNPP, this use of temporary flood barriers is incorporated in the proposed PNPP USAR changes as an exception to RG 1.102.

3.1.2 New Methodology for Addressing Flood-Borne Hazards and for Crediting Non-Safety-Related Protection Features for Flood Mitigation Under the reconstituted LIP flood hazard results, a new methodology is proposed to be used to address flood-borne missiles, because the current licensing basis for PNPP does not include flood-borne missiles. The licensee selected the guidance of Federal Emergency Management Agency (FEMA) P-259, Engineering Principles and Practices for Retrofitting Flood-Prone Residential Structures (Third Edition, January 2012), to provide a methodology for determining floodwater loading missile effects. FEMA P-259 is a publicly available document. The methodology was used in a calculation at PNPP to demonstrate the capability of the temporary flood mitigation panels and permanent protection features (closure plates, ramps) to withstand the hydrostatic and hydrodynamic forces resulting from the reconstituted LIP domain flood hazards. The calculation extracts peak floodwater depths and velocities for protected plant doorways (man doors and roll-up doors) and other relevant openings from reconstituted LIP analyses results. Using this information, the calculation employs typical fluid mechanics formulae to determine forces that act on the panels and other protection features (static and dynamic). These forces are determined using the guidance of FEMA P-259, which provides equations for calculating impact force from objects carried by moving water. Applicable flood-borne missiles are determined by review of the PNPP existing tornado missile spectrum.

Screening of this spectrum is performed to determine which tornado missiles are also applicable to flood-borne missiles. The selected flood-borne missile is evaluated to ensure that it is bounding of any other expected flood-borne missile hazards. The selected flood-borne missile

weight is then utilized in the FEMA P-259 methodology to determine the resultant equivalent loads (forces). These resulting forces are used to determine material stresses in the flood panels, other protection features, and mounting hardware using structural evaluation and strength of material formulae, which are then compared to allowable values. Allowable values are obtained from appropriate source documents, such as the American Institute of Steel Construction (AISC) Manual and American Concrete Institute (ACI) codes.

The licensees proposed new flood hazard protection scheme for PNPP credits the non-safety-related building exteriors themselves or credits a wall or curb around the perimeter of the applicable buildings. The protective wall or curb is constructed to an appropriate height and with sufficient margin to prevent flood water intrusion. Gaps are present only where temporary flood panels protect personnel or equipment openings (doors). The licensee noted that the protective features were analyzed and determined to be capable of withstanding the static and dynamic loads resulting from the analyzed flood conditions. With respect to water surface elevations above the nominal flood elevation of doors leading into plant structures, the licensee is installing flood barriers at the applicable doorways to provide a seal to prevent water from entering building structures. The barriers consist of installation of the steel end channels of the barrier system, which are attached to the building structure and allow for the installation of aluminum stop logs with seals to provide the flood protection. A total of 89 door locations are identified as points of interest with each assigned an identification number. All flood panels and door threshold ramps that are considered incorporated barriers have been analyzed and designed to protect against the static and dynamic forces and, where applicable, the missiles generated during the postulated event.

The stop logs used as flood barriers provide protection from flood waters up to approximately 2 ft in height. This is adequate to prevent water intrusion into the doors with the maximum water depth (Door 2HB 306-maximum water depth above ground elevation is 1.625 ft and Door 0SB 107-maximum water depth above ground elevation is 1.395 ft). The licensee stated that the aluminum flood barriers are capable of withstanding the postulated flood waters, including dynamic loading from impact velocity and impact from postulated flood-borne debris.

With respect to flood waters being present against the exterior of plant structures, the licensee is installing a flood barrier wall (either concrete or aluminum) as overall protection against water entry into plant buildings. The concrete walls are nominally 8 inches thick and 2 ft high at the building environment interface. The aluminum walls are comprised of modular segments, prefabricated using 1/4-inch aluminum plate, that are nominally 1.5 ft high and secured to the structure using concrete anchors. The segments are provided with 1/2-inch gaskets that form the seal at the panel-to-panel interface, as well as at the panel to concrete interface.

The licensee noted that the actual forces experienced by plant structures during a LIP event, the controlling flood event for the PNPP site, are far less than other design basis GDC 2 forces (specifically, tornado wind loads). For non-safety-related structures, the relatively low flood water heights and low velocities are analytically demonstrated to be within the capacity of the non-safety-related building exteriors (where credited) or the protection features provided at the environmental interface.

Because buildings have already been constructed, non-safety protection features, including the concrete portion of non-safety-related building walls, newly installed flood walls or curbs (either concrete or aluminum), flood panels, and non-safety-related building roofs (including roof drains and scuppers) are used for mitigation of the reconstituted design basis external flood hazard events. These protection features were not designed, fabricated, erected, or initially tested

consistent with SSCs that provide a safety-related function. Having been purchased and installed as non-safety related, these features do not fall under the scope of quality assurance program (QAP) controls. Therefore, the licensee proposed to credit existing (newly installed) non-safety-related protection features, including permanent (passive) and temporary (deployable) flood barriers that perform a mitigative function to act as an environmental interface for safety-related SSCs during external flood hazard events.

3.1.3 Flood Protection Scheme Evaluation The licensee proposed to transition from an all-passive flood hazard protection scheme to a combination of a passive and operator action-based flood hazard protection scheme. For off-site hazards (Lake Erie and streams adjacent to the site), PNPP is protected by topographic features, such as the Lake Erie bluff, and exterior barriers in the form of engineered channels and the recently installed berm. For the LIP domain, passive (permanent or normally installed) flood protection features protect the site up to and including the SPS. For a precipitation event larger than the SPS, temporary flood protection features would be utilized, specifically, removable flood panels (stop logs). These flood panels are either normally installed or stored in a central location to be deployed in accordance with operational procedures. Protection is provided at all environmental interfaces, including both safety and non-safety structures. The NRC staff notes that RG 1.102 allows for the use of temporary barriers (i.e., stop logs) if unusual circumstances arise after construction that would warrant consideration of using temporary flood barriers. The staff considers the reconstituted LIP flood hazard to be an unusual circumstance that warrants the use of temporary barriers around the building openings. This use of temporary barriers provides a reasonable approach to mitigate the effects of the LIP event while maintaining plant personnel safety by providing unobstructed exits during emergency situations. RG 1.59, Regulatory Position C.2, permits not to provide hardened protection for some of these features if sufficient warning time is shown to be available to shut the plant down and implement adequate emergency procedures, while safe shutdown SSCs remain fully passively protected. The licensee has provided clear guidance regarding when the temporary barriers must be installed, including a proposed TS that requires plant shutdown if the barriers are not installed in the appropriate time. The staff finds that this proposal meets the RG 1.102 guidelines because the use of incorporated barriers, supplemented with temporary barriers in unusual circumstances, is one of the three acceptable methods of flood protection in RG 1.102, and the RG 1.59, Regulatory Position C.2, guidance.

Under the reconstituted LIP flood hazard results, a new methodology would also be used to address flood-borne missiles, which were not considered in the original license application. The licensee used FEMA P-259 to provide a methodology for determining floodwater loading missile effects. These resulting forces are used to determine material stresses in the flood panels (barriers), other protection features, and mounting hardware and then compared to allowable values from appropriate source documents, such as the AISC Manual and ACI codes. The NRC staff audited calculation 50:77.000, Evaluation of Flood Barriers, to evaluate the existing concrete and aluminum flood barrier wall design and found that the barriers can resist the design basis flood-borne missile, hydrostatic, and hydrodynamic loads.

The licensee has evaluated the resulting static and dynamic loadings at safety-related buildings (structures) and non-safety-related buildings (structures) that function as an environmental interface to determine the flood protection requirements. The protective features were analyzed and determined to be capable of withstanding the static and dynamic loads resulting from the analyzed flood conditions. The NRC staffs audit confirmed that the licensee used an appropriate methodology to address flood-borne missiles, and that the licensees concrete and

aluminum flood barrier walls can resist the design basis flood-borne missile, hydrostatic, and hydrodynamic loads. In addition, the licensee has proposed an inspection plan that will verify that the concrete and aluminum walls are not experiencing degradation that would impact their ability to perform their intending function. Therefore, based on the above, the staff finds that the licensees flood barrier walls are acceptable to protect against the new flood hazard and that it is acceptable for the licensee to take credit for these non-safety-related features for flood mitigation.

3.2 Flood Model 3.2.1 Current Flood Protection Plan PNPP USAR Section 2.4 presents elevations using a U.S. Geological Survey (USGS) datum that is equivalent to the National Geodetic Vertical Datum of 1929 (NGVD 29). NGVD 29 is a publicly available document. The USAR indicates that the design basis flooding level (DBFL) is 620 ft 6 inches, the nominal elevation of the PNPP building floors.

The PNPP USAR indicates that the licensee originally used two simple equations to calculate flood flow rates and elevations for the local flooding due to a LIP event. One is the Rational formula for computing overland flow, and the other is the Weir Flow formula for computing water flowing over roads and railways on site. The Rational formula and the Weir Flow formula do not account for complications in the runoff processes. Additionally, these formulae neglect the advantages of runoff storage and assume a steady-state flow condition.

The LIP temporal distribution was based on the guidance of Hydrometeorological Report (HMR)-33 and the hourly distribution taken from the U.S. Department of the Interior, Bureau of Reclamation, Design of Small Dams, Washington, D.C., Second Edition, 1973. Design of Small Dams is a publicly available document. The licensees previous computations for flood elevations were based on the PMP event totaling 33.9 inches of depth with a 48-hour duration derived from HMR-33 methodology. The LIP event was determined by a temporally front-loaded storm distribution with the peak hourly intensity of 13.1 inches per hour, using a 6-hour subset of the 48-hour PMP event.

The surface runoff hydrographs for the Major Stream and the Minor Stream were generated by triangular synthetic unit hydrograph method and with no rainfall loss. In the LAR, the licensee did not change the triangular synthetic unit hydrograph method and the assumption of no rainfall loss remains in the surface runoff computations.

There are three separate storm drainage systems on the PNPP site - two draining to the west and a third draining to the east. Previously, the entire site area was subdivided into discrete sub-basins for hydrologic computations, such that the overland flows are no more than 300 ft before they reach a drainage inlet or catch basin. As described in the PNPP USAR, overland flow of storm water during a LIP event without considering the functioning of the storm drain system reached EL 620 ft 5 inches as the worst-case scenario (i.e., complete blockage of the storm drainage and using peak discharge from the most intense hour of the LIP). In this worst-case scenario, the ponding level of EL 620 ft 5 inches is below the nominal floor elevation at 620 ft 6 inches and provides a one-inch margin.

3.2.2 Proposed Flood Protection Plan The licensees updated maximum flood elevation exceeds the DBFL elevation of 620 feet and 6 inches. Therefore, with the update, the licensee proposed flood protection measures for the NRCs approval. Further, these flood protection measures have been installed and implemented since the licensees response following the 10 CFR 50.54(f) letter.

To analyze the LIP flooding with the PNPP site condition changes as described in section 1.1.2 of this safety evaluation, the licensee bounded the study area within the LIP domain. External plant flooding analysis for a LIP event included the functioning of the existing storm drainage system and roof drainage system. The licensee provided the flood modeling case of partial capacity of the storm drainage system, which was simulated by reducing pipe sizes and their inlets for debris partially blocking the drains. The site has been graded so that overland flow will occur away from the site and the buildings. The licensee indicated that the LIP is the controlling flood and that the associated water levels impacting the PNPP site are a result of the surface drainage capabilities partially functioning during a LIP event. However, the licensees modeling results show that the LIP flood elevations at many critical door locations exceed the plant floor elevations. The licensee has flood door-barriers ready in place for installations to prevent the excess flood elevations from intruding into the interior of the plant buildings during a LIP event.

The licensee provides deployable flood door-barriers (24 inches tall) at the critical door locations with margins to the flood elevations to keep the flood elevation below the top of the door-barriers. At the exterior of the buildings relevant to the critical doors, permanent short flood walls (24 inches tall) have been built against the LIP flood.

3.2.3 Flood Model Evaluation Based on its review described in sections 3.2.3.1 through 3.2.3.5 below, the NRC staff finds that the licensees updated flood hazard analysis is technically acceptable to support the proposed USAR revision.

3.2.3.1 LIP and PMP Changes The LIP flood is the result generated from a LIP event in the PNPP site. The PMFs in the Major Stream and Minor Stream areas are the results generated from the PMP event occurring in upstream watersheds. In its application, the licensee re-evaluated the LIP and PMP events with the adjusted hourly rainfall intensities and the total precipitation depths re-calculated based on the same previous HMR-33 methodology as described in section 3.2.1 of this safety evaluation.

The licensees proposed LIP and PMP update values are slightly modified when compared to the previous values (see Table 1).

As shown in Table 1, the licensees updates are increased by a small amount due to the difference between graphical and numerical interpolations in charts. These increases are less than 3% of the previous PMP and LIP. Based on the small increases with the adjusted hourly rainfall intensities, the NRC staff determined that the re-calculated PMP and LIP are acceptable.

Table 1 Precipitation Comparison Events PMP LIP Total Depth (inch)

Peak (inch/hour)

Duration (Hour)

Total Depth (inch)

Peak (inch/hour)

Duration (Hour)

Previous Design Basis 33.9 13.1 48 26.7 13.1 6

Proposed New Design Basis 34.73 13.19 48 26.91 13.19 6

Due to the PMP being updated and the drainage areas being revised with the new installed Diversion Stream, the PMFs for the Major Stream and Minor Stream are also changed (see Table 2).

Table 2 Changes of Upstream Watershed Areas and PMF Peaks Major Stream Minor Stream Drainage Area (square miles)

Peak of PMF (cubic feet per second [cfs])

Drainage Area (square miles)

Peak of PMF (cfs)

Previous Design Basis 7.16 31,250 0.76 7,000 Proposed New Design Basis 7.44 32,760 0.59 4,330 The NRC staff used a USGS quadrangle map and a watershed delineation tool to check the drainage areas and found that the changes of drainage areas are reasonable. The staff checked the changes of the PMF peaks, resulting from the updated drainage areas and PMPs. Based on the triangular synthetic unit hydrograph method, the staff found that the changes of PMFs are acceptable.

3.2.3.2 Flooding in the Major Stream Area for a PMP Change Regarding the flood in the Major Stream area resulting from the PMF re-calculation (Table 2),

the licensee removed a portion of the existing railway embankment to the southwest of the rail line bridge crossing the Major Stream. The removal of the embankment allows greater conveyance of flow in the southern overbanks of the Major Stream and prevents flow from overtopping the rail line. Furthermore, the licensee raised a secondary (contractor) access road to prevent any remaining backwater from overtopping the road. This modification resulted in the concentration of Major Stream runoff to be carried to flood plain and Lake Erie, rather than to other areas of the PNPP site.

In its August 17, 2021, supplement, the licensee provided the input data to a HEC-RAS model.

The NRC staff reviewed the licensees input data to the HEC-RAS modeling of the Major Stream flood profile within the reach adjacent to the plant. The staff has found acceptable the HEC-RAS model as one of the river hydraulic models for simulating flood conditions since using

the model is a common practice in hydrologic engineering. The HEC-RAS was developed by U.S. Army Corps of Engineers for simulating river flow conditions. Based on the licensees detailed stream cross sections, appropriate stream hydraulic parameters, and the PMF peak setup in the flood modeling as a constant steady flow rate (32,760 cfs), the staff finds that the modeling reasonably produced the flood condition at the Major Stream area. Comparing the licensees flood inundation map and the flood elevations of the modeling results, the staff determined that the modifications of the Major Stream embankment and the access road keep the flooding area at a significant distance away from plant structures.

3.2.3.3 Flooding in the Minor Stream Area for a PMP Change Regarding the flood in the Minor Stream area resulting from the PMF re-calculation (Table 2),

the stream no longer functions as a natural stream or river due to the installation of a new Diversion Channel. This new Diversion Channel intercepts the previous Minor Stream and diverts stream flow directly to Lake Erie. A portion of the previously engineered Minor Stream located between the plant area and the Diversion Stream remains at the site. This remnant section of the Minor Stream no longer functions as a traditional stream. The remnant Minor Stream, as it is now referred to, is a drainage swale located entirely within the LIP domain. Also, an engineered earthen embankment (termed the Diversion Stream berm) was installed to separate the LIP domain from the Diversion Stream and the original Minor Stream watershed.

The NRC staff reviewed the licensees input data to the HEC-RAS modeling of the Minor Stream flood profile within the reach of the Diversion Channel. Based on the licensees detailed stream cross sections, appropriate stream hydraulic parameters, and the PMF peak that was used in the modeling as a constant steady flow rate (4,330 cfs), the staff finds that the modeling reasonably produced the flood condition at the Minor Stream area. Using the simulated flood elevations and the licensees inundation map, the staff determined that the Diversion Channel and its embankment keep the flooding area away from plant structures.

3.2.3.4 Flooding in the LIP Domain for a LIP Change Regarding the updated flood in the LIP domain, the licensee used a two-dimensional unsteady flow model, FLO-2D computer program, to simulate the flood condition for the PNPP site. The simulation included partial functioning of the existing site drainage system and a conservative hypothetical berm breach outflow from the Diversion Stream to the LIP domain. The breach outflow is part of the models boundary condition as the worst hypothetical flood condition. The results showed that the simulated flood elevations exceed the doorway floor elevations at the plant. The licensee uses temporary door-barriers as a flood mitigation measure for protecting the safety-related SSCs under a LIP event. In response to the simulation results, the licensee has established a storm drain maintenance program to ensure the proper functioning of the site drainage system during the LIP event.

In its August 17, 2021, supplement, the licensee provided the input data to a FLO-2D model.

The NRC staff reviewed the licensees input data used in the FLO-2D modeling of the PNPP site flooding within the LIP domain. The staff finds the FLO-2D model to be an adequate model for simulating site flooding since the FLO-2D model is one of the surface runoff models based on hydrologic and hydraulic theories. The model has been used in hydrologic engineering practices and recognized by the community of practice. The staffs review included the breach outflow hydrograph assigned to the boundary condition of the modeling. Based on reviewing the FLO-2D modeling that included the uniform gridded size of the LIP domain, detailed site drainage system, the postulated 50% reduction of the drainage capacity, and the peak of LIP

temporal distribution (13.19 inches/hour), the staff finds that the modeling setup is reasonable, and that the modeling results adequately represent the flood conditions at the doorways of the plant. Based on the modeling results, the staff finds that the simulated flood condition at various doorways needs temporary flood door-barriers to prevent the flood from intruding into the doors.

The staff determined that the licensees door-barriers and the partial functioning (50% capacity reduction) of the drainage system are reasonable. As part of flood mitigation during the LIP event, the licensee includes a storm drainage maintenance plan to ensure that the storm drains function as intended, and an inspection plan to ensure that the deployable door-barriers are in place to prevent the flood flow from entering the plant buildings.

Based on the reasonably calculated simulated flood elevations, the licensee setup a flood protection scheme by installing operable door-barriers at various doorways where flooding is expected. At the exterior areas of the plant buildings, the licensee installed passive flood barriers such as exterior concrete walls. The licensee has established an action plan based on anticipated water levels prior to a LIP event to ensure that there is adequate time to install the temporary door-barriers. The licensee indicated that the warning time and deployment time are sufficient. However, in the case where the temporary door-barriers cannot be completely installed within the required period (12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />) the licensee will be required by proposed new TS 3.7.11 to start to safely shut down the plant within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. The temporary door-barrier installation and flood warning time are part of the licensees flood protection measures. (More detail regarding flood protection and warning time is in section 3.2.3.5 of this safety evaluation).

Based on the above, the NRC staff determined that the flood protection level is consistent with the design criteria described in Appendix A to RG 1.59 and in RG 1.102 and, therefore, concludes that the site flood mitigation scheme is acceptable.

3.2.3.5 Flood Protection Measures and Warning Time Following its initial response to the 10 CFR 50.54(f) letter, the licensee modified the Major Stream channel and built a Diversion Channel to direct the Minor Stream flow away from the plant. The Diversion Channel and the berm are part of the flood protection measures. The modification of the Major Stream is also included as part of the flood protection measures.

Some flood walls and other permanent flood barriers were installed above the floor by approximately 2 ft at the exterior of the plant buildings. In addition to these permanent flood protection measures, the licensee arranged for deployable door-barriers for use as temporary flood protection measures. The temporary door-barriers are approximately 2 ft high at the doors of the plant buildings. The NRC staff finds that the permanent and temporary flood protection measures adequately protect the PNPP site and that the temporary flood protection measures are consistent with flood protection measures described in RG 1.102 and, therefore, are acceptable for use as temporary flood protection measures.

The NRC staff also reviewed the warning time required for installing the deployable door-barriers as temporary flood protection measures. The licensee set 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> for the advanced weather forecast time that bounds the estimated time of deploying the door-barriers in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and plant shutdown in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. The licensee set warning indicators that are in two tiers of rainfall rates. The low tier is based on a forecast of 2.1 inches of rainfall in 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, and the high tier is based on a forecast of 1.9 inches of rainfall in one hour. The low tier is used for sending an initial alert to the plant operators. The high tier is used to initiate the door-barrier installation and start the off-normal instructions. These are included as part of the proposed new TS 3.7.11 and the Operations Requirement Manual. Since the higher tier rainfall rate of 1.9 inches in one hour is much less than the 13.19 inches of rainfall in one hour of a LIP event,

which is the peak intensity of a control event to inundate the PNPP site, the staff finds that the two tiers of warning time are acceptable.

3.3 Proposed New Flood Protection Technical Specification 3.3.1 Proposed New LCO Criterion In its June 1, 2022, supplement, the licensee proposed to add a new TS 3.7.11 to address flood protection requirements. The LCO for the proposed new TS 3.7.11 would require the licensee to provide flood protection for safety-related SSCs by deploying flood barriers when a meteorological report indicates the potential for a LIP flooding event (i.e., the Trigger Event).

This meteorological report is referred to in the LCO as a Trigger Event warning.

As discussed above, the timely deployment of the flood barriers is necessary to ensure that safety-related SSCs remain capable of performing their safety functions during a LIP flooding event. The affected SSCs are safety-related and include those needed to achieve and maintain cold shutdown. The licensee only needs the deployable flood barriers during a LIP flooding event. The licensee identified the LIP event of concern as being 1.9 inches of rainfall in an hour.

If the meteorological forecast were to predict a potential for a storm of this intensity or greater, then it would constitute a Trigger Event warning at which time, the licensee would be required by proposed new TS 3.7.11 to deploy the flood barriers at least 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> before the projected start of the LIP flooding or Trigger Event. If the barriers are not deployed in time, a plant shutdown would be initiated.

The NRC staff evaluated the licensees proposed new LCO against the requirements of 10 CFR 50.36 and the guidance in the SRP and the STS. To determine if the LCO was required to be included in TSs, the staff compared the purpose of the proposed LCO for flood protection to the four criteria for establishing LCOs in 10 CFR 50.36(c)(2)(ii). The staff determined that since the licensees accident and transient analyses do not assume a flooded condition at the start of or during a design basis accident or transient, the deployment of the flood barriers is an operating restriction necessary to maintain an initial condition for a design basis accident or transient. Therefore, the proposed LCO meets Criterion 2 of 10 CFR 50.36(c)(2)(ii). Similarly, since the barriers are a primary success path for mitigating a design basis LIP flooding event, the proposed LCO also meets Criterion 3 of 10 CFR 50.36(c)(2)(ii). Therefore, the proposed LCO meets the criteria for inclusion in the PNPP TSs.

The NRC staff found the selection of the Trigger Event warning to be acceptable because it will ensure that operators will be able to deploy the barriers prior to the onset of the LIP flooding event. The licensee determined that the flood protection barriers are needed in any plant operating mode. Since a Trigger Event can occur at any time, the licensee proposed the LCO Applicability to be At all times. This is acceptable because it will ensure that the licensee regularly monitors meteorological reports and deploys the flood barriers whenever a Trigger Event warning occurs regardless of the plant operating mode.

3.3.2 Proposed New LCO Conditions The licensee proposed three new Conditions and associated Required Actions and Completion Times (CT) to be entered, if applicable, when the LCO is not met.

Condition A Condition A addresses the action to be implemented when the notification of a Trigger Event is received. Once a Trigger Event warning is received, the LCO is not met until the flood barriers are deployed. Required Action A.1 requires that the flood barriers be deployed no later than 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> before the projected start of the Trigger Event. As noted in section 3.1.3 of this safety evaluation, the NRC staff has found the licensees proposed flood barrier scheme to be an acceptable means of providing flood protection in a LIP event. The CT for Required Action A.1 for deploying the barriers is Prior to being within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> of projected start of the Trigger Event. The licensee stated that its monitoring of the meteorological forecast would provide it with ample time to deploy the flood barriers. Based on this, the staff concludes that the CT for Required Action A.1 is reasonable because it provides adequate time after the meteorological warning (the Trigger Event warning) to deploy the flood barriers and it ensures that the flood protection is in place long before the onset of the LIP flooding event.

Condition B Condition B addresses the situation in which the licensee is unable to complete Required Action A.1 by its associated CT while in Modes 1, 2, or 3. Required Action B.1 requires the licensee to take the plant to Mode 3 (Hot Shutdown) within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Required Action B.2 requires the licensee to take the plant to Mode 4 (Cold Shutdown) within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. The Required Actions are reasonable because they ensure that the plant will be brought to a Cold Shutdown (Mode 4) in an orderly fashion prior to the onset of a LIP event if the licensee is unable to deploy the flood barriers in time. The CT is reasonable given that it allows an orderly shutdown of the plant to be completed prior to the onset of a LIP flooding event.

Condition C Condition C addresses the situation in which the plant is in an operating mode other than Modes 1, 2, or 3 (e.g., Mode 4 (Cold Shutdown)) and the licensee is unable to complete Required Action A.1 by its associated CT. In this Condition, the licensee must complete the following Required Actions:

C1.

Immediately suspend CORE ALTERATIONS except for control rod insertion, and C2.

Immediately initiate action to fully insert all insertable control rods in core cells containing one or more fuel assemblies, and C3.

Initiate action to restore primary containment to OPERABLE status within one hour, and C4.

Initiate action to restore isolation capability in each required primary containment penetration flow path not isolated within one hour, and C5.

Initiate action to close one door in each primary containment air lock within one hour Required Actions C.1 and C.2 are immediate actions to be taken if the licensee is unable to deploy the flood barriers by the CT while in a Mode other than Modes 1, 2, or 3. These actions will prevent an inadvertent criticality from occurring during the LIP flooding event, reducing the possibility of potential radioactive releases. Therefore, the NRC staff concludes that these actions are acceptable. As stated in PNPP TS 1.3, Completion Times:

When Immediately is used as a Completion Time, the Required Action should be pursued without delay and in a controlled manner.

Therefore, the immediate CT for Required Actions C.1 and C.2 is reasonable because it ensures that they will be completed without delay.

In addition to taking Required Actions C.1 and C.2 to prevent an inadvertent criticality, Required Actions C.3, C.4, and C.5 are actions taken to restore the containment as a boundary for controlling potential radioactive releases. These actions are acceptable because they will provide additional protection against an uncontrolled release. The CT of initiating the Required Actions within one hour is acceptable because the length of time to complete these actions can vary depending on the maintenance activities that are ongoing at the time that the Condition is entered and because the licensee will continue the actions until all requirements of Condition C are completed. In addition, the licensee will have taken the immediate actions in Required Actions C.1 and C.2 to prevent an inadvertent criticality.

3.3.3 Proposed New Surveillance Requirement The licensee proposed one SR for proposed new TS 3.7.11. This SR would require the licensee to monitor the 7-day meteorological forecast for Trigger Events on a 24-hour frequency. The purpose of this SR is to ensure that the licensee has sufficient advance notification of a Trigger Event to allow timely deployment of the flood barriers as required by Required Action A.1. The licensee stated that monitoring the meteorological report on a 24-hour basis would provide it with ample time to deploy the flood protection barriers if it were to receive a Trigger Event warning; therefore, the NRC staff concludes that the proposed SR is sufficient to ensure that the requirements of the LCO will be met.

3.3.4 Proposed Conforming Change to the TS Table of Contents The licensee proposed to revise the TS Table of Contents to reflect the proposed additions to the TSs, as described in sections 3.3.1 through 3.3.3 of this safety evaluation, and as detailed in the June 1, 2022, supplement. The proposed changes to the TS Table of Contents are editorial and do not change any technical content and are consistent with the other proposed changes.

Therefore, the NRC staff finds the proposed changes to the TS Table of Contents acceptable.

3.3.5 Flood Protection Technical Specification Conclusion Based on the above, the NRC staff determined that the proposed new TS 3.7.11 satisfies the requirements of 10 CFR 50.36(c)(2)(i) because its proposed LCO specifies the lowest functional capability or performance levels of equipment required for safe operation of the facility. There is reasonable assurance that the required actions to be taken when the LCO is not met provide adequate protection of public health and safety and will be completed in a timely manner. In addition, facility operations in accordance with the LCO can be conducted without endangering the health and safety of the public. The proposed new TS 3.7.11 also satisfies the requirements of 10 CFR 50.36(c)(3) because its proposed SR assures that the LCO will be met. Therefore, the staff concludes that proposed new TS 3.7.11 is acceptable.

4.0 STATE CONSULTATION

In accordance with the Commissions regulations, the State of Ohio official was notified of the proposed issuance of the amendment on January 9, 2023. The State official had no comments.

5.0 ENVIRONMENTAL CONSIDERATION

The amendment changes requirements with respect to the installation or use of facility components located within the restricted area as defined in 10 CFR Part 20 or changes surveillance requirements. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration as published in the Federal Register on July 6, 2021 (86 FR 35544) and July 15, 2022 (87 FR 42505), and there has been no public comment on such finding. Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.

6.0 CONCLUSION

The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) there is reasonable assurance that such activities will be conducted in compliance with the Commissions regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributors: Y. Cheng, NRR J. Ma, NRR R. Elliott, NRR A. Armstrong, NRR S. Wall, NRR Date of issuance: February 3, 2023

SUBJECT:

PERRY NUCLEAR POWER PLANT, UNIT NO. 1 - ISSUANCE OF AMENDMENT NO. 200 REGARDING THE REVISION OF METHODOLOGY USED FOR FLOOD HAZARD ANALYSIS (EPID L-2021-LLA-0067)

DATED FEBRUARY 3, 2023 DISTRIBUTION:

Public PM File Copy RidsNrrPMPerry Resource RidsACRS_MailCTR Resource RidsNrrDorlLpl3 Resource RidsRgn3MailCenter Resource RidsNrrDssStsb Resource RidsNrrDexExhb Resource RidsNrrDexEseb Resource RidsNrrDssScpb Resource RidsNrrDroIqvb Resource RidsNrrLASRohrer Resource RidsNrrLASLent Resource AArmstrong, NRR BLee, NRR BLehman, NRR JMa, NRR JLopez, NRR KSee, NRR YCheng, NRR RElliott, NRR RHernandez, NRR HAhn, NRR Accession No.: ML22284A144 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DEX/EXHB/BC NAME SWall SRohrer BHayes DATE 01/03/2023 01/10/2023 01/17/2023 OFFICE NRR/DEX/ESEB/BC NRR/DSS/STSB/BC NRR/DSS/SCPB/BC NAME ITseng VCusumano BWittick DATE 01/10/2023 01/09/2023 01/12/2023 OFFICE NRR/DRO/IQVB/BC OGC - NLO NRR/DORL/LPL3/BC NAME KKavanagh JWachutka NSalgado (JWiebe for)

DATE 01/09/2023 02/02/2023 02/03/2023 OFFICE NRR/DORL/LPL3/PM NAME SWall DATE 02/03/2023 OFFICIAL RECORD COPY