Text

Engineering Services Technical Report TR02060-001
	ML12348A398
Person / Time
Site:	Summer
Issue date:	11/20/2012
From:	Grybosky L, Winterhalter J; South Carolina Electric & Gas Co
To:	; Office of Nuclear Reactor Regulation
References
	RC-12-0189 TR02060-001, Rev 0
	Download: ML12348A398 (26)
	v • d • e

SOUTH CAROLINA ELECTRIC & GAS VIRGIL C. SUMMER NUCLEAR STATION NUCLEAR OPERATIONS ENGINEERING SERVICES TECHNICAL REPORT TR02060-001 Response to NRC Request for Information Pursuant to 10 CFR_50.54(f)

Reciardina the Floodina Aspects of Recommendation 2.3 of the Near-Term Task Force Review of Insights From the Fukushima Accident Verification Walkdown Report for VCSNS Plant Flood Protection Features REVISION 0 4,

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ORIGINATOR '--Lav( 7 rto4Grybosky/Jon A. Winterhalter DATE.

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APPROVAL AUTHORI`TY (VCSNS) - DATE RECORD OF CHANGES CHANGE TYPE APPROVAL CANCELLATION CHANGE TYPE APPROVAL CANCELLATION LETTER CHANGE DATE DATE LETTER CHANGE DATE DATE

Ii - - I I Recommendation 2.3 - Flooding Walkdown Report TR02060-001 Revision 0 Table of Contents SECTION PAGE

1. Purpose 1

2. Scope I

3. References 2

4. Walkdown Report 3

5. Figures 15

6. Attachments 15

7. Revision Summary 15

Recommendation 2.3 - Flooding Walkdown Report TR02060-001 Revision 0

1. Purpose The purpose of this Technical Report is to provide a written response to the U. S. Nuclear Regulatory Commission (NRC) pursuant to the requirements in Title 10 of the Code of Federal Regulations (10 CFR), Section 50.54(f) letter, dated March 12, 2012 (NRC 50.54(f) Letter), as applicable to the Virgil C. Summer Nuclear Station, Unit 1 (VCSNS).

As part of this request, licensees are required to perform walkdowns to verify that plant flood protection features, credited in the current licensing basis (CLB) for protection and mitigation from external flood events, are available, functional and properly maintained to ensure the operation of safety systems in the event of a credible flood event. This report documents the results of the flooding walkdowns that were performed at the plant on July 13-16, 2012, August 6-9, 2012 and October 1-3, 2012. The work for the flooding walkdowns was performed in compliance with the 10 CFR 50 Appendix B program.

Walkdown Record Forms and any other supplementary data supporting this Technical Report are included in Report TR02060-002. Report TR02060-002 is available at the VCSNS for review.

For purposes of this report, flooding refers to the external ingress of water resulting from local intense precipitation and severe weather conditions, which could adversely affect system, structures, and components (SSCs) important to safety and includes Probable Maximum Precipitation (PMP) and Probable Maximum Flood (PMF).

2. Scope This report is prepared by WorleyParsons under SCE&G Purchase Order NU-02SR747671, "Fukushima Flooding Walkdowns and Re-Evaluation."

The scope of this report is to respond to specific information requests from the NRC 50.54(f) Letter, which includes the following items:

1. Description of the design basis flood hazard levels for all flood-causing mechanisms, including groundwater ingress.

2. Description of the protection and mitigation features that are considered in the licensing basis elevation to protect against external ingress of water into SSCs important to safety.

3. Description of any warning systems to detect the presence of Water in rooms important to safety.

4. Discussion of the effectiveness of flood protection systems and exterior, incorporated, and temporary flood barriers. Discussion of how these systems and barriers were evaluated using the acceptance criteria developed in Item 1.h of 50.54(f) Enclosure 4.

5. Information related to the implementation of the walkdown process (e.g., details of selection of the walkdown team and procedures) and includes actions taken in response to the peer review.

Last Revised: 11/20/2012 1:35:00 PM Page 1 of 15

Recommendation 2.3- Flooding Walkdown Report TR02060-001 Revision 0

6. Results of the walkdowns including key findings and identified degraded, non-conforming, or unanalyzed conditions.

7. Discussion of any cliff-edge effects identified and the associated basis.

8. Description of any other planned or newly installed flood protection systems or flood mitigation measures, including flood barriers that further enhance the flood protection.

Detailed walkdown report content requirements are included in Appendix D, "Walkdown Report" of NEI 12-07 [Rev. 0-A] (Reference 3.2).

3. References 3.1 U. S. Nuclear Regulatory Commission (NRC), "Request for Information Pursuant to Title 10 of the Code of Federal Regulations (10 CFR), Section 50.54(0 Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-Ichi Accident," March 12, 201:2 3.2 NEI 12-07 [Rev. 0-A], "Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features," May 2012 3.3 NEI 12-01 (Revision 0), "Guidelines for Assessing Beyond Design Basis Accident Response Staffing and Communications Capabilities," April 2012 3.4 NRC Letter to NEI, "Endorsement of Nuclear Energy Institute (NEI) 12-07, "Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features'," June 14, 2012 3.5 NEI Letter to NRC, "NRC Endorsement of NEI 12-07, 'Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features'," June 18, 2012 3.6 Training Preview (NANTEL for Flooding Taskforce) Rev 0 and related "Learning ObjectivesR4" 3.7 TR02060-002, 10 CFR 50.54(f) Regarding the Flooding Aspects of Recommendation 2.3 of the Near-Term Task Force Review of Insights From the Fukushima Accident, Verification WalkdoWn Report for VCSNS Plant Flood Protection Features - Walkdown Record Forms and Supplementary Data 3.8 Certified Survey Data, "V.C. Summer Station Unit 1," Required Survey Ground Shots, Glenn Associates Surveying, Inc., August 1, 2012, Revision 0 3.9 Photogrammetric Survey, "SUMMER_2012_DTM.DGN," by Glenn Associates Surveying, Inc., August 28, 2012 3.10 Photogrammetric Survey, "SUMMER_2012_TOPO.DGN," by Glenn Associates Surveying, Inc., August 28, 2012 Last Revised: 11/20/2012 2:22:00 PM Page 2 of 15

Recommendation 2 Flooding Walkdown Report TR02060-00i Revision 0

4. Walkdown Report Specific walkdown report content requirements are included in Appendix D, "Walkdown Report" of NEI 12-07 [Rev. 0-A] (Reference 3.2). The following subsections provide the requested information.

4.1 Current Licensing Basis (CLB) Flood Hazard Level The Virgil C. Summer Nuclear Station (VCSNS) site plan is shown on the attached Figure A for reference. The VCSNS site is the equivalent of a dry site as defined in RG 1.102. There are no major potential external sources that could result in flooding on site. The site is protected from flooding and wave run-up on the north side from the adjacent Monticello Reservoir by a properly designed exterior revetment barrier consisting of an embankment with protective stone riprap. The normal water elevation of Monticello Reservoir is 425.0 feet while site grade around the plant is typically at 435.5 feet. Plant grade is raised to 438 feet directly adjacent to the embankment at Monticello Reservoir creating, in effect, a minor levee referred to as the North Berm. The North Berm, including the elevation and riprap protected embankment, are designed to protect the site at a maximum elevation of 437.5 feet from postulated stormwater-related flood conditions, plus wave run-up, from Monticello Reservoir, as described in Chapter 2 of the FSAR.

The Monticello Reservoir is the nearest body of water to the site, and serves as the source of cooling and makeup water for the VCSNS. Monticello Reservoir has a surface area of about 6,800 acres and a storage volume. of about 400,000 acre-feet at the normal maximum water surface elevation of 425.0 feet.

The Service Water Pond (SWP) is a Seismic Category 1 impoundment constructed adjacent to Monticello Reservoir that is physically separated by Seismic Category 1 dams and natural land masses. The SWP supplies water for the Service Water System under normal and emergency operations. The interconnecting pipe, through the operation of a butterfly isolation valve, permits the SWP to be supplied from Monticello Reservoir. For normal operating conditions, the Monticello Reservoir and SWP levels will fluctuate between elevations 420.5 feet and 425.0 feet.

The current licensing basis (CLB) documents were reviewed to compile the Flooding Walkdown Credited Features Checklist. The documents that were reviewed include: FSAR; Procedures; Technical Specifications; Maintenance Rule Procedures; LRA; LRA SER; LRA and SER Commitments; Design Calculations; Construction Drawings; NSR Structures DBD, Topical Seismic DBD, SW DBD; PLEX/LRA Technical Reports including: TROO170-001, -002, and -003; ES-0400 SW Pond Structure & Dam Inspections Guidelines; Fukushima Response letter to INPO iER 11-1 dated 4/15/11; NRC TI 2515-183 inspection results; CR-11-01207 (Lessons Learned from the IER 11-1 walkdowns); and IPEEE conclusions TR00310-001.

Last Revised: 11/20/2012 1:35:00 PM Page 3 of 15

Recommendation 2.3 - Flooding Walkdown Report TR02060-001 Revision 0 A spreadsheet was developed to record the documents that were reviewed to identify credited flood protection features. That spreadsheet, "VCSNS NTTF 2.3 Flooding Walkdowns Review of Current Licensing Basis References" is included as Attachment A in Report TR02060-002.

In summary, the flood hazard levels for VCSNS are as follows:

4.1.1 Flooding from Monticello Reservoir PMF Monticello Reservoir normal maximum still Water level is 425.0 feet, NGVD 29 (FSAR, Section 2.4.10). Maximum water level during Probable Maximum Flood (PMF), with wind storm surge and wave setup is defined as 436.6 feet, NGVD 29.

The North Berm top .is at design elevation 438.0 feet.

A conservative design basis assumption is that no water is released from the Fairfield Hydro station during the event. The controlled normal maximum reservoir still water level is assumed to be at elevation 425.0 feet. If water were released by Fairfield Hydro station, the water level would be less than 425.0 feet.

4.1.2 Flooding from the Service Water Pond (SWP) PMF Service Water Pond (SWP) normal maximum still water level is 422.0 feet, NGVD 29 (FSAR, Section 9.2.5.3.2.3.a). Maximum water level during Probable Maximum Flood (PMF), with wind storm surge and wave setup, is defined as 433.6 feet, NGVD 29. The West Embankment top is at design elevation 435.0 feet. The other dams forming the SWP have top design elevations of 438.0 feet.

The SWP is designed to preclude being flooded, or drained, by Monticello Reservoir. An interconnecting pipe is the only hydraulic connection between the SWP and Monticello Reservoir. This pipe is fitted with a butterfly isolation valve that is locked Closed during normal operation (FSAR Sections 2.4.8 and 9.2.5).

4.1.3 Local Intense Precipitation Local intense precipitation, defined as the greatest hourly depth of rainfall during the 6-hour probable maximum precipitation (PMP), has been determined to build up to elevation 436.15 feet on the site assuming no flow in the storm inlets and storm sewer pipe system (completely blocked) before overland flow allows surface runoff to flow off the plant site perimeter away from the main plant buildings (FSAR, Section 2.4.3.1.3).

The centerline elevation of the roads surrounding the perimeter of the plant area is at 436.0 feet. The overflow capacities of the surrounding .roads act as weirs up to elevation 436.0 feet, resulting in a maximum ponding elevation of 436.1.5 feet during the 6-hour PMP (FSAR, Section 2.4.3.1.3).

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Recommendation 2.3 - Flooding Walkdown Report TR02060-001 Revision 0 The roofs of safety-related buildings are designed to safely dispose of or store up to a maximum of 4 inches of local intense precipitation (FSAR, Section 2.4.10)..

4.1.4 Broad River Flooding Flooding from the Broad River was not. considered due to the elevation difference from the river to the site. Nominal site grade of 435 feet is 150 feet above the Broad River flood plain.

4.2 CLB Credited Flood Protection and Mitigation Features The current licensing basis (CLB) takes credit for flood protection from several types of features. All of these features are "Incorporated or Exterior Passive" features, as defined in NEI 12-07 [Rev. 0-A], Section 3. These credited feature types are grouped as follows:

1. Dams (and Berms) - Minimum top dam and berm elevations prevent Monticello Reservoir or the Service Water Pond from flooding the site during probable maximum precipitation (PMP) and probable maximum flood (PMF) events.

2. Grade - Site grade was designed such that rainfall runoff during PMP event flows overland to prevent flooding of buildings, exterior equipment, and systems.

3. Exterior Building Walls - Walls protect buildings from infiltration of flood waters during PMP/PMF; penetrations (for pipes/conduitsldoors) are included in their respective wall. Below-grade penetrations are sealed and thick concrete walls are protected on their outside surfaces by a continuous waterproofing membrane. Waterstops are provided at joints.

4. Floor Slabs - Slabs protect buildings from infiltration of flood waters during PMPtPMF.

5. Roofs - Protect buildings from infiltration of flood waters from local intense precipitation PMP No flood mitigation features are credited in the CLB.

There are no plant procedures requiring actions in the VCSNS CLB that provide for flood protection or mitigation.

No flooding occurs on site during current licensing basis PMP or PMF events.

Therefore, flood duration is not a concern.

Last Revised: 11/2012012 1:35:00 PM Page 5 of 15

Recommendation 2.3 - Flooding Walkdown Report TR02060-001 Revision 0 4.3 Flood Warning Systems 4.3.1 As the VCSNS site is the equivalent of a dry site relative to flood protection, no formal flood warning system is in place to warn of potential flooding. Procedures and systems do exist to warn of extreme weather events. They are as follows:

1. EPP-015, "Emergency Plan Procedure, Natural Emergency" This procedure addresses seismic events, tornados, hurricanes, winter storms, and Fairfield Hydro dam failure.

2. OAP-109.1, "Operations Administrative Procedure, Guidelines for Severe Weather" This procedure addresses cold and hot weather, hurricanes, high winds, and heavy rain.

4.4 Effectiveness of Flood Protection Systems & Exterior, Incorporated, and Temporary Barriers All of the credited flood protection features are "Incorporated or Exterior Passive" features. There are no "Incorporated or Exterior Active" features and there are no "Temporary" features.

Flood protection features whose conditions prevent the flood protection feature from performing its credited function during a design basis external flooding event are reported as deficiencies and entered into the licensee's Corrective Action Program (CAP). A detailed discussion of these deficiencies and how they have been entered into the CAP are included in Section 4.6 and Section 4.8, respectively.

4.5 Walkdown Process and Team 4.5.1 Walkdown Guidance The NEI 12-07 [Rev. 0-A] guidelines were followed for walkdown procedures. No active features requiring simulation were identified.

4.5.2 Walkdown Team The following WorleyParsons personnel received training in the NANTEL training course "Flood Protection Verification (Generic Verification Walkdown of Plant Protection Features)":

Ronald J. Cox, mechanical/piping designer, 39 years of experience, 14 years of VCSNS plant experience Jon A. Winterhalter, PE, civil engineer, 38 years of experience, VCSNS plant experience beginning 1974 Last Revised: 11/20/2012 1:35:00 PM Page 6 of 15

Recommendation 2.3 - Flooding Walkdown Report TR02060-001 Revision 0 Lawrence Grybosky, PE, civil/geotechnical engineer, 13 years of experience Benjamin E. Culbert, structural designer with 12 years of experience, 3 years of VCSNS plant experience Pradeep Velugubantla, civil engineering, 8 years of experience The Curriculum Status report documenting successful training completion is included in Attachment A.

The site walkdown team consisted of four or five of the trained WorleyParsons personnel and one or more of SCE&G engineering, plant, or security personnel.

Each WorleyParsons walkdown team member was fully indoctrinated and trained relative to the NEI 12-07 [Rev. 0-A] guidelines, current licensing basis credited flood prevention or mitigation features, and other related directives, information, and recommendations. In addition, two (2) of the WorleyParsons walkdown team members completed confined space entry training and fall protection training.

While onsite, the walkdown team was supported by WorleyParsons home office senior mechanical and electrical discipline staff and project management.

Additionally, site-located client engineering and plant staff assisted the project walkdown team in collection of supplemental documents, procedures, plant history, and in location/positive identification of features during the walkdowns. The NRC resident inspector was invited to accompany the licensee during the walkdowns, and participated in two walkdowns.

4.6 Walkdown Results: Key Findings, Degraded, Non-Conforming, or Unanalyzed Conditions A list with a total of 62 credited flood protection features was developed from the CLB documents that were reviewed (refer to Section 4.1). All 62 credited flood protection features were walked down and observations were recorded on Walkdown Record Forms. In accordance with NEI 12-07 [Rev. 0-A], only the key findings are summarized herein. The Walkdown Record Forms are included in Report TR02060-002 and are available at the: plant site for review.

Degraded, non-Conforming, or unanalyzed conditions are described below, and include references to the Condition Report (CR) that enter the conditions into the licensee's correction action program (CAP). Available physical margin (APM) describes the flood margin available for applicable flood protection features at a site, and is the difference between licensing basis flood height and the flood height at which water could affect a structure, system, or component (SSC) important to safety.

Last Revised: 11/20/2012 1:35:00 PM Page 7 of 15

Recommendation 2.3 - Flooding Walkdown Report TR02060-001 Revision 0 4.6.1 The following deficiencies were observed during the flooding walkdowns and entered into the CAP as CR-12-04133:

4.6.1.1 North Berm (Credited Feature ID DE-1): Top of berm elevation is below CLB elevation 438.0 feet (low point elevation is 437.7 feet). The CLB APM of 1.40 feet is reduced to 1.10 feet. The berm being at a lower elevation than in the CLB reduces its flood protection margin. This feature was evaluated and recommended as "OPERABLE" in the CR. A detailed discussion on the CR is included in Section 4.8.

4.6.1.2 North Dam (Credited Feature ID DE-2): Top of berm elevation is below CLB elevation 438.0 feet (low point elevation is 437.1 feet); The CLB APM of 4.40 feet (internal, the side of the Service Water Pond) is reduced to 3.50 feet and the CLB APM of 1.40 feet (external, the side of Monticello Reservoir) is reduced to 0.50 feet. The berm being at a lower elevation than in the CLB reduces its flood protection margin. This feature was evaluated and recommended as "OPERABLE" in the CR. A detailed discussion on the CR is included in Section 4.8.

4.6.1.3 East Dam (Credited Feature ID DE-3): Top of berm elevation is below CLB elevation 438,0 feet (low point elevation is 437.5 feet). The CLB APM of 4.40 feet (internal) is reduced to 3.90 feet and the CLB APM of 1.40 feet (external) is reduced to 0.90 feet. The berm being at a lower elevation than in the CLB reduces its flood protection margin. This feature was evaluated and recommended as "OPERABLE" in the CR. A detailed discussion on the CR is included in Section 4.8.

4.6.2 The following deficiencies were observed during the flooding walkdowns and entered into the CAP as CR-1 2-03267:

4.6.2.1 Auxiliary Building, North Wall (Credited Feature ID EBW-2): Door thresholds were below the CLB flood elevation of 436.15 feet, thus eliminating APM for this credited feature. The lowest door threshold was at elevation 435.9867 feet. This feature was evaluated and recommended as "OPERABLE but DEGRADED, see CER for Corrective Action(s)" in the CR.