ML16272A220

Enclosure 1: Flood Walkdown Report (NRC 50.54(f) NTTF Recommendation 2.3), Dated November 27, 2012 (Redacted)

ML16272A220
Person / Time
Site:	Oconee
Issue date:	11/27/2012
From:	Duke Energy Carolinas
To:	Office of Nuclear Reactor Regulation
Shared Package
ML16070A295	List: ML16070A284 ML16070A287 ML16070A288 ML16070A290 ML16272A216 ML16272A217 ML16272A218 ML16272A220 ONS-2015-028, Supplemental Information Re NRC 2008 and 2012 Request for Information Pursuant to 10 CFR 50.54(f) Pertaining to External Flooding, Dated March 6, 2015 (Redacted)
References
FOIA/PA-2016-0071
Download: ML16272A220 (30)

Text

ML123380112 Oconee's Flood Walk-down Information Requested by NRC's March 12, 2012, I0CFR 50.54(f) Letter November 27, 2012

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Enclosure 1 Flood Walkdown Report (NRC 50.5.4 (f) NTTF Recommendation 2.3)

Flood Walkdown Report - NRC 50.54 (1) NTTF Recommendation 2.3 TABLE OF CONTENTS 1.0 PURPOSE.................. ......... ............................. ,........ :.................. 3 2.0 DESIGN METHOD/ANALYTICAL METHOD ....... ,.................................... ...... 3 3.0

SUMMARY

IN FORM~AI-ION.................................................................... 4 4.0 ASSUMPTIONS ....... ,................................................. ....... ...... .. ..... 4 5.0 TECHNICAL PRESENTATION. ..... .. ............ ,................................. 4 5.1. CURRENT LICENSING BASIS (CLB) FLOOD SCENARIOS.........,....................... 4 5.1.1 UFSAR Based Flooding.,,.. ..... ,,.,............ ...................................... 4 5J.1.. ProbableMaximum PeclpitatlOn....... ...... ......... ............. ..... .... ;.......

.... ...................... 4 5.1. 1.2. Keowee Reservoir Retention-,.............,..................* ...............  ;....,.,..... .. :*......................6 5.1.1.3 5SF Flood Protect/on.... ..........................................  ;..................................... ..... 6..

5.1.2 Safety Evaluation Based Flooding (Pending, NON UFSAR) .................... ,..7 51.2.1 Jocassee Sunny Day Failure- Safety Evaluation (SE)............. ......... ,.. ,,...*............. ............ ,...,7 5.2 Flood Mitigating Features and Their Effectiveness........................ ,.,.. .......... 9 5.2.1 PMP Protection Features ..... *,...,...,..,. .. ,........ .........

10 5.2.2 Keowee Reservoir Retention Features.,.......,...........,*.......................... 12 5.2.3 SSF Flood Protection Features ;.,... ....... *...,...,.,.....,..!.. 13 5.2.4 CAL Intedim Compensatory Measure (1CM) Features .... ............... .. ,,.

..... 13 5.2.5 Other Features ........... ,.............. ,......... ,.......... ...... .... .. :......... .18 5.12.6 Flood Warning systems.......................,............,................  :. .. ....... 19

5.3 DESCRIPTION

OF WALKDOWN PROCESS AND ACCEPTANCE CRITERIA,.. ........ 19 5.4 RESULTS OF WALKDOWNS .. ,...... ... ........ ,........,.............,..............,... 21 6.0 ComplianCe with NEI 12-07, Appendix D..... ,.................. .... ....... 24

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Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 1.0 PURPOSE This report documents the results of a Flood Design Basis Walkdown performed to provide information to the United States Nuclear Regulatory Commission (NRC) as requested by its letter dated March 12, 2012.

Background:

In response to the events at Fukushima Dai-ichi due to an earthquake and subsequent tsunami, the NRC issued an information request on Marchl 12, 2012, in accordance with Title 10 of the Code of Federal Regulations, Section 50.54(f). Enclosure 4 of the 50.54(f) letter is directed toward addressing the Near Term Task Force (NTTF) Recommendation 2.3 for Flooding and requested the results of a flooding design basis walkdown. The NRC subsequently endorsed the guidance document, NEI 12-07 (Rev. 0-A), as a satisfactory approach to providing this information. This report provides the information requested by the 50.54(f) letter as described in NE! 12-07. This report is based on the current External Flood Licensing Basis and the features that Oconee Nuclear Station (ONS) credits for mitigation of an external flood (as of September 2012). The SSC's that are further discussed in this report range from QA-1 to NON-QA. The walkdown findings were documented as an ONS calculation, which constitutes a retrievable location for the NTTF 2.3 Flood Walkdown Report and Walkdown Package.

2.0 DESIGN METHOD/ANALYTICAL METHOD The 10 CFR 50.54(f) letter was issued in the course of implementing the lessons learned from the accident at the Fukushima Dai-ichi nuclear facility. The NRC accepted NEI 12-07 as a guideline document created by the Nuclear Energy Institute (NEI), which describes a process for performing the requested work. The following is an excerpt from the NRC'S acceptance letter.

"The NRC staff confirmed that the guidance directs the licensee to perform the walkdowns in a manmer that will address the Requested Information items 1l.a through 1.j in the 10 CFR 50.54(f) letter. Additionally, the NRC staff finds that Appendix D, "Walkdown Report,"' of NEI 12-07 delineates the appropriate information to be submitted in response to Requested Information items 2.a through 2.h of the 50.54(f) letter.

As described above, the NRC staff has reviewed the guidance contained in NEI 12-07 and finds that performance and reporting of flooding protection walkdowns in accordance with this document would be responsive to the 10 CFR 50.54(f) letter.'"

ONS took no exceptions to the NEI 12-07 guidelines and implemented the methods that were recommended for completing the walkdowns. The NE! 12-07 document was found to be acceptable as a walkdown procedure and was utilized by Oconee in the performance of the walkdown process. No exceptions were taken to the NEI 12-07 walkdown process.

Accordingly, the Walkdown forms in Appendix B of NEL 12-07 were used to perform the walkdowns, including a peer review required by the forms.

The technical detail contained in this report is derived from referenced information contained in the calculation written to document the walkdown findings.

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Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 CZNT.JNJ ZEZU~IIT EJTEIrClTZ.

3.0

SUMMARY

INFORMATION The requested Flood walkdowns required ONS to inspect all flood mitigation features and procedures that make- up the current licensing basis. The walkdowns incorporated a thorough review of all features, procedures, preventive maintenance (PM) programs, and early warning detection systems. The findings support that all mitigation and protection features are expected to successfully perform their design basis function. Minor issues were discovered throughout the wvalkdown process and these issues have been captured in the plant Corrective Action Program (Problem Identification Program -PIP). None of the issues challenge Oconee's ability to maintain the safety condition of the Nuclear Station.

One deficiency, as defined by NE! 12-07, was found related to digital readouts of the voltmeters at the Keowee Spiliway. This issue has been captured in PIP and does not negatively affect the operability of the Keowee Spiliway.

The walkdown effort was performed, and this report is in full compliance with NEI 12-07. All inspection requirements were met and no exceptions were taken to the NRC approved process laid out in NEI 12-07.

4.0 ASSUMPTIONS There were no assumptions used in the walkdown process. Every feature was either walked down specifically for the NTTF 2.3 Flood Walkdown in November of 2012, or within the past-year for various other reasons.

5.0 TECHNICAL PRESENTATION Thiis portion of the report is provided to describe the current, as Of November 2012, External Flood Licensing Basis and the features that ONS credits in the mitigation of an external flood.

5.1 CURRENT LICENSING BASIS (CLB) FLOOD SCENARIOS 5.1.1 UFSAR Based Flooding 5.1.1.1 Probable Maximum Precipitation This discussion focuses on theProbable Maximum Precipitation (PMP) and its impact on the local drainage basins. For Oconee, there are two (2) drainage basins of concern when impacted by precipitation. The first basin is the larger Keowee reservoir drainage basin that encompasses an approximate 439 square mile area (Updated Final Safety Analysis Report (UFSAR) 2.4.1.2).

This basin is associated with "External" rainfall and its analysis. The second basin is the smaller local drainage basin which is associated with "Local" (or ONS site related) rainfall and its analysis. The local drainage basin can be further divided into two areas. The first encompaSSes an approximate 129 acre area around Oconee Nuclear Station and the second is the approximate 9.5 acre local drainage basin around Keowee Hydro Station. The Oconee local drainage basin is Page 4

Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3

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characterized by a ridge line on the north and west that slopes east-south- east into the relatively level yard (Approximate Elevation: 796 feet). On the east side-of the. yaird, the terrain continues its slope to the east-south-east to the Keowee river channel (Approximate Elevation: 672.5 feet).

UFSAR Section 2.4.2.2 defines ther Probable Maximum Precipitation (PMP) as 26.6 inches of rain falling within a 48-hour period, thus proviiding the magnitude (quantity) of rain and the duration of the rainfall event. The distribution of they rainfall *overthe 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> period was

,patterned after an actual storm that occurred on August 13-15, 1940 (UFSAR 2.4.2.2).

The UFSAR states that "essential"' systems and componentsr are designed, fabricated and erected to Withstand forces that might be imposed by natural phenomena that include, in part, ground water and flood (UJFSAR 3.1.2). The essential systems and components were defined to include the Reactor Coolant System, Reactor Vessel InternalS, Reactor Building, Engineered SafegUards Systems and the Electric Emergency Power Sources. As delineated ini UFSARSection 3.4.1 1,

• Class 1 structures have measures to protect them from floods. Section 3.4.1.,1 states that the plant yard elevation is 796.0 feet mean sea level (msl) and the minimum external access elevation for the Auxiliary, Turbine and Service Buildings is 796.5 feet msl, creating a 6 inch water "sill". This sill constitutes a barrier to flood water entering Class. 1 Structures and provides water detention capacity (ponding) over the yard area, thereby reducing the impact of*a storm's peak rainfall. Also, there is "a surface water drainage system that protects the plants facilities from local precipitation"' (UrFSAR- 3.4.1!.1). Implicit to the surface water drainage system :(the corrugated metal pipe drainage system), is the free edge along: the cast-south-east Side of the plant. While surface water doesn't cascade down this slope during normal rainfall (erosion), this flow path provides an additional feature in the overall flood mitigation strategy. In summary, rainfall would initially surface-flow to the yard drainage system and be removed from the plant

• yard, until the: yard drainage system reaches its capacity. Water would then begin (starting at the catch basin locations) to pond over the plant yard where it would be detained until the yard drain system "catches up" with the precipitation, or in the most extreme cases,: the water would surface flow to and cascade over the free edge and down the eastern slope of the plant.

Adverse weather conditions that could be assumed to simultaneously occur with the PMP could include typical storm conditions, making work outside dangerous or difficult. However, Lthe licensing basis protective features for the PMP event are passive in nature and exist or :are staged prior to the event occurring.

The weather conditions that initiate the PMP flooding event are described in the Oconee Severe.

Weather Preparations PrOcedure. Specifically, these conditions include rainfall in excess of 4 inches of rain :in any 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> period. This procedure dictates actions to be taken prior to the weather event arriving.

Because this flooding event is 48 hrs in duration, local flood heights vary with time.

A new calculation for the Licensinag Basis PMP which estimates the local flood heights around

'the ONS site is in the review stage. However, at the time of this report, the calculation was not Page 5.

Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3

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complete calculationand is not incorporated is discussed in Sectioninto 5.2 the CLB.report,)

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.. preliminary 5.1.1.2 Keowee Reservoir Retention Asecond external flood initiator is the Keowee Reservoir. Section 2.4.1 .1, "Site and Facilities" of the UFSAR describes this feature by the height of the retention dikes and dams of the Keowee Reservoir. It states: "All of the man-made dikes and dams forming the Keowee ReservOir rise to an elevation of 815 ft msl including the intake channel dike." Lake Keowee was formed in 1971 by the Keowee Dam on the Keowee River and the Little River Dam on the Little Ri'ver. Its primary purpose is to provide cooling water for ONS and a water source for the Keowee Hydro Electric Station. At full pond, 800 ft msl, Lake KeoWee has a surface area of 18,373 acres, a Shoreline of approximately 300 mi, and a v~olume of 955,586 ac-ft, and a total drainage area of' about 439 square mi. The Jocassee and Keowee Reservoirs and the hydroelectric stations located at the reservoirs are owned and operated by Duke Energy. The UFSAR further describes floods on the Keowee Reservoir by stating "While spiliway capacities at Keowee and Jocassee have been designied to pass the design flood with no Surcharge on full pond, the dams and other hydraulic structures have been designed with adequate freeboard: and structural safety factors to safely accommodate the effects of the maximum hypothetical precipitation. Because of the time-lag, characteristics of the runoff hydrograph aftera storm, it is not, considered credible that the maximum reservoir elevation due to the maximum hypothetical precipitation would occur simultaneously with winds causing maximum wave heights and run-ups." (UFSAR Section 2.4.2.2.) There is one exception to the Keowee Reservoir Retention dikes and dams maximum 815 ft mnsl elevation. This exception is described as "Two Reinforced Concrete Trenches extend through the Intake Dike with a minimum elevation of 810 ft' msl, with all removable covers removed. These trenches are protected from wave action by the Condenser Cooling Water (CCW) Intake Structure and the Causeway at the west end of the Intake Structure. Therefore only the maximum reservoir elevation of 808 ft msl is applicable with regard to flooding t~hrough the reinforced concrete trenches."(UFSAR Section 2.4.2.2)

UFSAR Section 18.3.8, Federal Energy Regulatory Commission (FERC) Five Year Inspections describes the Keowee Reservoir Retention items as: the Keowee River Dam, Little River Dam, Little River Dikes A, B, C, D, Oconee Intake Canal Dike, Keowee Spiliway, Keowee Intake, and Keowee powerhouse. This sections states, "Inspections of the Keowee River Dam; Little River Dam; Little River Dikes A, B, C, D; Oconee intake Canal Dike; Keowee Spillway and Left Abutment, Keowee Intake and Powerhouse are performed in accord ance with the requirements in 18 CFR Part 12, Safety of Water. Power Projects and Project Works."

5.1.1.3 SSF Flood Protection:

An additional Licensing caveat exists in ONS's UFSAR. UFSAR Section 9.6.3.1i describes the design basis loads for the Standby Shutdown Facility (SSF). 'The original design* basis for the SSF stated, "Flood studies show that Lake Keowee and Jocassee are designed with adequate margins to contain and control floods... The Final Safety Analysis Report (FSAR) addresses OCronee's location as ona ridgeline 100' above mnaximum known floods. Therefore, external Page 6

Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 flooding due to rainfall affecting rivers and reservoirs is not a problem. The 5SF is within the site boundary and, therefore, is not subject to flooding from lake waters." (UFSAR Section 9.6.3.1). In: 1983, a Jocassee dam failure study Was completed to determine-the maximum water

-h~eight around the SSF if a postulated failure of the Jocassee'Dam is considered. The results of the Study estimated a peak flood elevation of 817.45 ft msl at the Keowee darn, and an ONS yard flood level of 4.71 ft. In response to this study, ONS erected several walls approximately 5 ft tall around the entrances tO the SSF as a risk reduction measure. This was not part of the design basis. Based on Oconee's September'26, 2008 response to a 10CFR 50.54 (f) request for information, ONS increased the height of the flood wall, around the SSF by 2.5 ft. The :resulting elevation of 803.5 ftresl provides additional margin.

The UFSARSection 9.6.3.1 was. updated to say: "As a PRA enhancement the 5SF is provided with a five foot eXternal- flood wall which is equipped with a water tight, door near the south entrance of the SSF. A stairway over the wall provides access to the north entrance. The yard elevation at both the north and the south entrances to the SSF is 796.0 ft msl .Based on the as-built configuration of the 5' flood wall provided at the north entrance and the flood wall at the south entrance to the SSF,. SSF external flood pr'otection is provided for flooding that does not exceed 80.1 feet above mean sea level." In its current as-built condition, the SSF has flood.

protection features up tO elevation 803 '-6" msl.

5.1.2 Safety Evaluation Based Flooding (Pending, NON UFSAR) 5.1.2.1 Jocassee Sunny Day Failure -Safety Evaluation (SE)

A unique external flood initiating eyent is the Sunny Day Failure of the Jocasseel Dam. This initiator is derived from an NRC SE dated January 28, 2011i, addressing commitments made in regards to the June 22, 2010 Confirmatory Action Letter (CAL) to address external flooding concerns. This initiating event is 'unique in that its basis originates from an SE, not the UFSAR=.

The discussion below is a synopsis of the SE.

inr April 2006, the U.S. NRC staff questioned the flood protection barrier for the SSF. The NRC identified that the licensee had incorrectly calculated the Jocassee Dam Failure frequency .and had not adequately addressed the potential consequences of flood heights predicted at ONS.

Based on concerns raised by the NRC, by letter dated August 15, 2008, (ML081640244) the NRC requested information in a 10CER 50.54(f) letter. Duke Energy responded on:

September 26, 2008 (ML082750!106)r to the licensee request. The NRC staff reviewed the information and based on the review, the NRC staff found' that the information proyided by the licensee did not demonstrate that the :ONS site would be adequately protected from. external flooding events. SpecifiCally the licensee did not:(l) provide an adequate inundation study, (2) provide a deterministic resolution of this matter, and (3) provide a schedule to resolve the external flooding issue in a timely manner.

After further correspondence, the NRC Staff issued a Confirmatory Action Letter to the licensee on June 22, 2010, requesting the following-: 1) submit to the NRC all documentation necessary to page 7

Flood Waikdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 demonstrate that the inundation of the ONS site, from the postulated failure of Jocassee Dam, has been bounded 2) by November 30, 2010, submit a list of all modifications necessary to:

mitigate the inundation, and 3) make all necessary modifications by November 30, 2011.

The staff also requested that the compensatory measures (CMs) listed in the CAL remain in place until final resolution has been agreed upon between the licensee and the NRC staff.

The SE goes on to discuss its evaluation of the methods and parameters chosen to be used by Duke Energy. It concludes by stating: "The u nmitigated Case 2 dam breach parameters that Were used in the flooding models, provided by Duke Energy for ONS site, demonstrated that the*

licensee has included conservatisms of the parameters utilized in the dam breach scenario. These conservatisms pr'ovide the staff with additional assurance .that the above Case 2*scenario will bound the inundation at ONS, therefore providing reasonable assurance for the overall flooding scenario: at the site. This new flooding scenario is based on a-random -sunny-day failure of the Jocassee Dam. This Case 2 scenario will be the new flooding basis for the site." (SE dated January 28, 2011) The final commitment listed in the SE states that the, licensee has committed to keep the compensatory measures in place until final resolution has been agreed upon between the licensee and ;the NRC staff."

There are no assumed adverse weather conditions that occur simultaneously with the Dam break and its associated mitigation strategies. The Case.2 scenario, as described in the SE produces a flood height of 81 5'-0" msl in the Oconee Yard. This flooding event lasts approximately 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> before the: flood waters recede below yard level. The CAL dated. June 22, 20110 has a list.of committed compensatory measuires tO be implemented by the licensee. The Compensatory Measures are listed in the-table below:,

Table 1: Compensatory Measures from CAL dated June 22, 2010 No. CompenSatory Measures Implementation

. . .... _ Status Perform flooding studies using the 1-EC-RAS model for,comparison with 1 previous DAMBRK models to more accurately represent anticipated flood Completed

___heights in thie west yard following a postulated failure of the Jocassee Dam Maintain plans, procedures (Jocassee and Oconee) and guidance documents implemented (Oconee) to address .mitigation of postulated flood events which could render the SSF inoperable and are consistent~with cunrent 2 perspectives gained foilpwing the H-EC-RAS sensitivity studies and the Completed-

'subsequent 2d inundation studies. TO the extent p~ractical, the mitigatiOn strategy is similar to existing extensive plant damage-scenario (B.5.b)

___equipment, methods and criteria.

Duke Energy H-ydro Generation will create a guidance document to 3 .consolidate river management and storm managemnent processes. (Includes* Completed

___the Jocassee Development and the Keowee Development) ________

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No. Compensatory Measures Implementation

_____Status Maintain a dam safety inspection program that includes: (I) weekly damn safety inspections of the Jocassee Dam by Duke Energy personnel, (2) dam 4 safety inspections following any 2-inch or greater rainfall or felt seismicCoped event, (3) annual dam safety inspections by FERC representatives, (5) fiveCoped year safety inspections by FERC approved consultants, and (6) five year underwater inspections......

Maintain a monitoring program that includes:' (1) continuous remote S monitoring from the Hydro Central Operating Center in Charlotte, NC, (2) 5 monthly monitoring of observation wells, (3) weekly monitoring of seepage Completed

___monitoring points, and (4) annual surveys of displacement monuments.

6 oASsignoasean Oconeestts engineer as Jocassee Dam contact to heighten awareness Completed Install ammeters and voltmeters on Keowee spillway gates for equipmentCoped 7__ condition monitoring.Coped 8 Ensure Forebay and Tailrace level 'alarms are provided for Jocassee toomlee

___ support timely detection of a developing dam failure.Coped Add a storage building adjacent to the Jocassee spillway to house the backup Coped

___ spillway gate operating equipment (e.g. compressor and air wrench)Coped Obtain and stage a portable generator and electric drive motor near the 10 Jocassee spillway gates to serve as a second set of backup spillway operating Completed

___equipment.

Conduct 11__ to exerciseJocassee and improveDam failure response Table Top Exercise with Oconee participation procedures.Coped Coped 12 Instrument and alarm seepage monitoring locations for timely detection ofCoped 12_ 'degrading conditions.Coped 13Provide additional video monitoring of Jocassee Dam (e.g. dam toe 13__ abutments, and groin areas) for timely assessment of degrading conditions. Completed 14 Obtain and stage a second set of equipment (including a B.5.b-type pump) Completed 14__ for implementation of the external flood mitigation guidance. ________

15 Conduct Jocassee Dam/Oconee Emergency Response Organization Drill to Completed

___exercise and improve response .procedures._________

5.2 Flood Mitigating Features and Their Effectiveness The Current Licensing Basis (CLB), as defined by 10CFR 54.3, is the set of Nuclear Regulatory Commission (NRC) requirements applicable to a specific plant, plus a licensee's docketed and currently effective written commitments for erisuring compliance with, and operation within, applicable NRC requirements and the plant-specific design basis, including all modifications and additions to such commitments over the life of the facility operating license. It also includes the plant-specific design basis information, defined by 10CFR 50.2, as documented in the most recent UFSAR as required by 10OCFR 50.71.

The set of NRC requirements applicable to a specified plant CLB includes:

• NRC regulations in 10 CFR Parts 2, 19, 20, 21, 26, 30, 40, 50, 51, 54, 55, 70, 72, 73 and 100 and appendices thereto Page 9

Flood Walkdown Report - NRC 50.54 (f) NTTF RecOmmendation 2.3

• Commission Orders

• License Conditions

• Exemptions-

• Technical Specifications

• Plant-Specific design basis information defined in 10 CFR 50.2 and documented in the most recent UFSAR (as required by 10 CFR 50.71)

• Licensee Commitments remaining in effect that were made in docketed licensing correspondence (such as licensee responses to NRC bulletins, License Event Reports, Generic Letters and Enforcement Actions)

• Licensee Commitments documented in NRC safety eValuations Based on this description of the CLB and the above listed ONS specific CLB flooding initiators, a list of features has been compiled. Below is a description of thie different features and justification as to why they have been included based on CLB. Many of the features are actually groups of smaller features and for convenience has often :been paired together.

-5.2.1 PMP Protection Features The first group is features #1- #9.

These features are included because of the PMP initiating flood as described above. They are all either at yard elevation (--796 ft msl) or below grade and are listed below:

Flood Waikdown Feature

1. 1 - Auxiliary Building Exterior Subsurface Walls and Seals

1. 2 -* Radwaste trench covers and seals from Radwaste Facility to Turbine Building r*#3- Radwaste trench covers and seals from Radwaste Facility to Auxiliary Building

1. 4--Interim Radwaste trench covers and seals

1. 5- Manhole 7 Cover, Techni'cal Support Building vault and seals

1. 6- Borated Water Storage Tank (BWST) trench Covers

1. 7- Yard Drain system

1. 8- CT-5 trench covers :in Auxiliary Building

1. 9-, PMP rainfall event flood barriers sandbags and Gryffoiyn Early in 2012, an issue arose about the PMP analysis for the ONS yard. This led to a thorough investigation of current status of various structures on site and their ability to resist flood waters from a PMP event. A vendor is currently working on a new analysis of the ONS yard to gain more precise local flood heights around the yard. A walkdown was performed for all Class 1 structures and other structures deemed critical to safe shutdown using preliminary results from Page 10

Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 wirnnoIu iru.u puuua ul*.u. . 1......Cf 3.21_.I)')

an initial draft' version of the revised PMP analysis. 'That analysis is currently in final review and indicates thait the Versioni Used for the walkdowns was conservative.. The walkdown sueyed the building envelope to identify weaknesses in flood protection. It was determined that ONS is in nonconform~ance with the Licensing Basis as described in UFSAR Section 3.4.1.1 becauise water may exceed a 6 inch sill in a few areas surrounding the Class 1 structures. All other areas surrounding the structures were' determined to be acceptable. Compensatory measures were taken in the form of Flood Barrier Sandbags and Gryffolyn coverings. These barrier locations and heights are based on a preliminary analysis that was performed on local flood heights in the yard. This information is being v¢alidated by the vendor analysis. The~se compensatory measures temporarily protect some of the site, other places on site were either found to be acceptable or have been entered into PIP and resolutions have been made. ONS received a NRC finding on the UFSAR no~nconformarnce issue. The NRC finding is described in the Oconee NRC Inspection Findings Report 2012003. All issues are either currently being tracked or resolved in PIP or have been found toube acceptable. None of these features require a repeat walkdown based on NEI 12-07,. Section 5.5 guidelines. The comprehensive walkdowns performed early in 2012 as documented in PIP meet the intent and requirements of NEI 12-07.

The overall effectiveness of these features can be described as adequate to protect against historic rainfall events. A PIP that describes an issue with the RadwaSte facility trench that enters the Auxiliary' Building~was written in 2012. An open penetration was discovered in this trench. During normal rainfall events when it is possible to incur water build up against the 6" lip, water does not leak into the Auxiliary Building through below grade penetrations. Flood levels such'as those produced during the CLB PMP event have never been approached during a rainfall event at ONS. In the recent years, two significant rainfall events have occurred that would have challenged the integrity of the water tightness feature of the trench. One is tropical storm Jeanne, on September 28, 2004, that dropped 3.17 inches of rain in 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> on Seneca, South Carolina (SC). The other tropical storm being Cindy, on July 7, 2005, dropped 2.93 inches of rain in 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> on the Same location. If the water tightness of the subject trenches had been degraded and they were challenged on these dates, evidence would have likely been indicated by the level indications in the Low Activity Waste Tank (LAWT). PIP database:

research found no record of excessive filling of the LAWT on these days. In addition, Operations personnel indicate no noticeable correlation between LAWT levels and rainfall events, indicating that the subject trenches (and the Auxiliary Building as a whole) have not been subject to any unanticipated inflows. At the time the PIP was written, the trenches that enter the.

Auxiliary Building served as thle flood barrier and'the Au~xiliary Building* wall Was considered to be~functional but non-conforming. However, the functional expectations of ONS's Selected Licensee Commitment (SLC) are satisfied. To resolve the nonconformance, a modification installed an isolation valve and flow limiting device to ensure water fr~om these trenches could not enter the Auxiliary Building unimpeded.

Two shortcomings were identified during the walkdown process of these items. The first' shortcoming related to following the design control process and the second related to the PM program for the subsurface protective features. Because of this issue, PIP's have been Written to enhance the PM programs on the yard drain system, as well as the below grade pernetrations.

Page. 11

Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 C..T.I.. jrri" flD IpV, CU' MCN/ITIUVI INFnR MATION*

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J...13cr OI)1 Engineering Changes. have been initiated to control-labels for the ,below grade auxiliary penetrations identifi'ed" as-flood features, on site design drawings.

Features #1 through #9 are passive features that are very rarely affected by normal plant operations. All of these items, with the exception of the yard drain system, are listed 'as passive design features in an Oconee Site Directive.- The inclusion of features on the ,passive design feature list ensures that the items remain functional and in place. There is a controlled process for removing these features from service. If at any time there is a threat of external flood due to PMP, the Operations Shift Manager (OSM) is notified and the feature is immediately returned to service. A piP has been 'written to address the Yard Drain System with respect to passive design.

5.2.2 Keowee Reservoir Retention Features A second group consists of Features #10 - #16. These features are included because they are part of the Keowee Reservoir Retention items as described above. Listed below are the seven features:*

Flood Walkdown Feature :

1. 10- Keowee river dam

1. 11- Oconee Intake Canal Dike

1. 12- Little River Pam

1. 13- Little RiVer Dikes A, B, C, D

1. 14- Keowee Intake

1. 15- Keowee Powerhouse

1. 16- Keowee Spiliway This is the same list of dikes and dams listed in section 18.3.8 of the UFSALR. Each of ihese Keowee Reservoir retention items is well maintained and inspected on a regular basis. Section 18.3.8 of the UFSAR dictates that these items are to undergo 5 year FERC inspeetions.* The most recent FERC inspection was performed in, 2012. There are also yearly FERC and Duke Energy internal inspections of these same features. Additionally, Keowee personnel inspect the earthen structures every two weeks. This inspection data is collected and stored in a hard copy log book at Keowee Hydro Station. Any degradation or nonconforming items found in these inspections would be documented and included in PIP. The scope of the F*ERC'5* year inspections is sufficient in meeting the intent of the NEI 12-07 walkdowns. The personnel performing these inspections have enveloping qualifications as described in NEJ '12-07. ONS has elected to not perform rework for the features that have been inspected based on FERC inspections. The items listed above can be described as Very effective in performing their design functions. No PIP's or corrective actions were identified for these items on the basis of their ability to retain the Keowee Reservoir.

'Page 12

Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 CO,,N.tA

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5.2.3 SSF Flood Protection Features The third group consist of features #32- #34. These features are included because they are the exterior flood protection features for the SSF. Listed below are the three features:

Flood Walkdown Feature

1. 32- 5SF flood barriers including exterior walls

1. 33- SSF steel plate with CO2 refill access

1. 34- SSF External wall penetrations These features form the exterior flood protection wall that was installed as a risk reduction measure for PRA. Even though these items are not the design basis for the SSF, they have been included on this list because they are described in the UFSAR. All SSF external wall penetrations below elevation 803.5 ft msl were walked down in 2012 by a member of the Civil Design Basis team. This walkdown effort is recorded in PIP and any recommendations or degradation of items are also captured and being tracked in PIP. The SSF flood barriers, including all three features listed above, are also included in the Passive Design Features list..

These features ensure the SSF has flood protection up to an elevation of 803.5 ft msl. The three features listed above can be described as being effective at performing their intended function.

The exterior flood walls as well as the steel plate with Carbon Dioxide (CO2) refill access have never been challenged by flood waters. These are passive features and based on the acceptance criteria they are judged to be acceptable and are expected to survive a flood event.

5.2.4 CAL Interim Compensatory Measure (ICM) Features The fourth group consists of Features #17 - #31. Their purpose is to mitigate flood conditions based on a postulated sunny day failure of the Jocassee Dam, as described in Section 5.1.2.1 of this report. This list was derived from the fifteen CAL Compensatory Measures, as described above, and the actions taken by ONS in order to satisfy the CAL. These features include plant flood protection procedures, early flood detection warning equipment housed at Jocassee Hydro, and emergency equipment housed at Oconee and operated under emergency procedures. The list of features is provided below:

Flood Walkdown Feature

1. 17- EM 5.3 Procedure

1. 18- AP/0/A/1700/047 Procedure

1. 19- Jocassee Flood-mitigating plans and procedures

1. 20- Duke Energy Hydro generation guidance document

1. 21- Dam safety inspection program

1. 22- Maintained monitoring Program

1. 23- Keowee Spillway enhancements

1. 24- Jocassee Forebay and tailrace alarms Page 13

Flood Waikdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 CONT,.INJ JECUIUT'.' JENJTIVE*'F IF7r;',TI*N.

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1. 25- Jocassee storage building with backup spiliway operating equipment

1. 26- Portable generator and electric drive motor near the spiliway

1. 27- Documentation of Table top Exercises

1. 28- Instrumentation and alarm selected seepage monitoring locations

1. 29- Video monitoring of Jocassee Dam

1. 30- Second set of B.5.b like equipment

1. 31- Jocassee dam-ONS response drill documentation Some of the above listed items are simply historical documentation describing events that took place, or proving compliance with the Compensatory Measures. Others are early warning detection devices, such as the video monitoring equipment at the Jocassee dam. The items that were walked down at Jocassee were determined to be very effective in performing their intended design function. No issues were found with any of the equipment maintained at Jocassee.

A self assessment was recently performed at ONS for the items listed above. ONS has a NRC commitment to perform this assessment to ensure the Interim Compensatory Measures described in the CAL are maintained. The assessment report identified one deficiency and four recommendations. The deficiency and recommendations are pertinent to the Flood features

1. 17-31 and are discussed below.

Deficiency I. Generated a PIP in the Corrective Action Program on repair of Keowee spillway gate voltmeters. The inoperability of these instruments is a deficiency as noted in the NEI 12-07 walkdown of plant flood protection features.

Recommendations (enhancements)

1. Determine if Jocassee Emergency Communication Equipment should include a mobile satellite phone to address widespread loss of power concerns and secure equipment if warranted.

2. Inform Jocassee Dam Contact of any new Jocassee monitoring equipment issues that may arise in the future. The Jocassee Dam Contact should generate a tracking PIP to inform ONS Station management of status and resolution. -

3. Evaluate using non ethanol fuel or add a fuel stabilizer to the electric generator that

, powers backup spillway equipment.

4. Evaluate draining and replacing the fuel in the electric generator at some frequency (Hale pump has fuel changed every, 2 years)

These recommendations are captured as Corrective Actions in the PIP for the self assessment.

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Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 Two of the above items, Features #17 and #18, are procedures, Engineering procedure (E.M. 5.3) and Abnormal Procedure AP/0/A/1700/047 (AP-47). These are the only procedures identified as a Flood Feature that could reasonably be simulated. Both procedures have previously been exercised during Emergency Drills and OPS personnel are trained on them. A new revision was released in August 2012 and was simulated. Some aspects of the procedures, such as turning on equipment, making nozzle connections, and others, are not actually performed during the simulation but do not devalue the simulation since ONS has documentation that these activities have been performed and timed. All issues identified during the simulation, were captured in the PIP process. None of these issues were deemed to cause the procedures to be non-effective. All systems were found to be functional and all operator actions were found to be feasible. With minimum staffing available and the complex evolutions that take place in AP-47, the simulation confirmed that adequate staff resources were able to complete the tasks during the event.

Feature #20 corresponds with the CAL Interim Compensatory Measure #3 (1CM #3). Duke Energy Hydro Generation developed the "Keowee - Toxaway Project High, Water Operations Process" for managing the river management and storm management process. This process defines the operating plan for lake level management of the Keowee-Toxaway (K-T) project, which includes the Lake Toxaway, Lake Jocassee, Lake Keowee, as wvell as the Bad Creek reservoir, in consolidating river management and storm management in anticipation of significantly high precipitation and storm runoff events. Aspects of thifs high-water operations process are summarized below:

• Operations Issue - definition of the plan

• Risk Management Summary - A description of the risk to the public safety, mitigation strategy, and responsibility for ensuring execution of the plan.

• Operating Commitments - Defined commitments of each organization in the K-T Project, Hydro Generation Management and Staff, and Hydro Central Operating Center, for execution of the process for mitigating of significantly high precipitation and storm runoff events

• Compensatory Measures - A description of Hydro Central Operating Center staffing 24/7 to execute the process as well as contingency operating locations should it be needed.

• Contingency Operating Actions - A description of actions to be performed by Hydro Central including daily monitoring of weather forecasts and weather radar for potential abnormal rainfall amounts that could cause a rapid rise in the K-T Hydro projects, including monitoring of the K-T area lakes for rapid lake level rise (rapid rise defined for Jocassee as a 0.6 foot rise per hour).

This feature was found to be acceptable.

Feature #21 corresponds with the CAL 1CM #4. All aspects of maintaining a dam safety inspection program, as defined in this 1CM, were found to be met. No issues were identified during walk-downs of these systems/components or documents. The Jocassee dam safety Page 15

Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 inspection program is a very comprehensive program utilizing multiple resources and methods for inspection of the water retaining components of the Jocassee Project.

Feature #22 corresponds with the CAL ICM #5. All aspects of the Jocassee Dam monitoring program were found to be met. No issues were identified. The program is comprehensive and encompasses redundant means for identification of any issues associated with the Jocassee Dam and its supporting structures. Additionally, instrumentation is in place, operable, and is properly maintained to support the monitoring program.

Feature #23 is associated with the Keowee Spillway Enhancements. '[he Keowee Spillway enhancements are comprised of digital voltmeters and ammeters that were installed at all four spillway gates. These digital readouts allow operators controlling the spillway gates to quickly and easily see the voltage and amaperage during gate movement prevent damaging the gates, if the gates stick or bind during movement. Upon inspection, all four sets of ammeters were working properly but all four sets of the voltmeters were out of service. The voltmeters were previously discovered to be inoperable and entered in PIP. The PIP was closed to a work order, because the failure of the voltmeters did not prevent the gates from operating, and was not reportable to FERC. A new PIP was written to document the issues of the voltmeters and included their association to the procedural issues for operating the gates. The gate operating procedure does not provide instruction to the operators on the use of the voltmeters, or any back up methods for reading voltage during operation. The Keowee"spillway voltmeters are being described as a deficiency, as defined in NEI 12-07. This was the only identified deficiency from the walkdown this feature.

Feature #24 corresponds with the CAL 1CM #8. Jocassee Forebay and Tailrace instrumentation (alarms) were the subject of a walk-down at the Jocassee facility. The instrument systems were observed to be operable with no issues identified. Procedures are in-place at Jocassee and the Hydro Operations Center (HOC) to address these alarms should they be activated. No findings identified.

Feature #25 corresponds with the CAL ICM #9. A storage building which houses backup operating equipment for the spillway gate is located next to the Jocassee spillway and contains two independent sets of backup operating equipment for controlling the spillway gate.

• One means consists of a diesel powered air compressor and an air operated wrench (which is discussed in this 1CM 9).

• A separate means consists of a portable powered electrical generator and an electric wrench (which is discussed in 1CM 10)

This equipment is dedicated for use in providing a backup means of operating the Jocassee spiliway gates and has no other purpose. The storage building and backup equipment was in good physical condition. The air compressor and air wrench are tested monthly for proper operation. (This Work Order also checks the electric generator and electric wrench mentioned in 1CM 10). The startup instructions contain a check for sufficient fuel in the compressor.

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Feature operated#26 corresponds spiliwaywith the CAL ICM #10. alsoThe backup operating storagea separate building set which houses the air equipment contains of electrical backup operating equipment. The electrical set is comprised of a diesel generator and an electric powered wrench. The equipment was in good physical condition and a demonstration of powering the backup electric wrench from a generator was observed. The generator and air wrench are tested monthly for proper operation. Part of the startup instructions checks for sufficient fuel in the generator. An interview with Jocassee management confirmed that the equipment in the storage building is dedicated for providing backup operational control for the Jocassee spillway gates, and is not used for any other purpose.

Feature #27 corresponds with the CAL 1CM #1l 1, to implement table top exercises. A table top exercise to evaluate the use of AP/O/Ai1 700/047 and EM 5.3 was conducted on 6/28/2010 and documented in PIP. Enhancements have been incorporated into API0/A/1 700/047, the Oconee Emergency Plan and Hydro EmergencY Actions plans. Proposed actions related to EM 5.3 have been augmented with actions from the 12/15/2010 Oconee Emergency Drill 2010-02. The Jocassee Emergency Plan was revised to make the Oconee OSM the first contact for a dam failure event.

Feature #28 corresponds with the CAL 1CM #12, for seepage monitoring instruments.

Instruments at selected seepage monitoring points were verified by visual inspection with the Jocassee staff and Hydro Central staff. The instruments have a wireless feed to a repeater station located on the crest of the Jocassee dam which transmits instrument data to the Bad Creek Control Room and Hydro Central. The alarm logic is based on rate of level change and initiates procedure action for immediate operator response to verify conditions and initiate appropriate action level.

Feature #29 corresponds with the CAL IC* 3 for visual mopitng of Jocassee Dam. ]

cameras are located at the Jocassee intake;W~ 7 for security and (7)for monitoring.lake level.

• 7()additional cameras are located at the Jocassee discharge or security and* 7 for monitoring the Dam structure and discharge. No findings were 1 ntified. Ant exploration of the Jocassee site which included observations of the intake and discharge was conducted. We visually observed that thd*)l)F camera (used for monitoring) had been installed in addition to the normal securit (b)(7)(F) J. The Jocassee supervisor gave a tour of the Jocassee control room and demonstrated how the additional cameras could detect potential Dam failures. Cameras gave real time images of actual water level conditions and could monitor the Dam structure.

Feature #30 corresponds with the CAL 1CM #14 for the B.5.b like equipment. This feature was walked down at the same time as much of the AP-47 procedure simulation walkdowns. The "second set" of equipment, as referenced in the June 22, 2010 CAL, is comprised of a second Hale pump permanently located at Chemical Treatment Pond (CTP)-l and a External Flood Mitigation (EFM) trailer located at the base of the Oconee Office Building. The primary set of similar equipment is the actual B.5.b equipment located inside its shelter building at the Oconee Page 17

Flood Walkdown Report - NRC 50.54 (1) NTTF Recommendation 2.3

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Intake Canal. The overall effectiveness of this feature is determined to be functional. Minor issues were noted with this equipment.

The first issue was that a copy of an enclosure to AP-47 which directs how EFM trailer is to be used, and is stored inside the trailer, was found to be wet and damaged but still useable. This issue was immediately resolved.

Next, there were concerns about the mounting locations for the fire hoses throughout the yard.

Because these hoses will be deployed across the yard during the flood, there were questions if the hoses would be adequately secured. There were also concerns about the appearance of a small oil leak at the Hale pump. This issue was resolved. The suction source for the Hale pump, CTP-l1, had visible accumulations of algae floating in the pond. This raised a question regarding whether the strainer would become clogged. Weaknesses in the PM program for the suction pipes at the Hale pump were also discovered. Input from Site Chemistry regarding the algae supports the determination that the strainer would not clog and the Hale pump is designed to operate with algae in the water. This issue was entered into PIP and is being tracked. None of these issues keep the pump from performing its intended function.

Because this equipment is either permanently located above the flood plain or is procedurally moved to a higher elevation, the flooding event will not impact operator actions. It has been validated that ONS, at minimum required staffing, has enough operators to complete intended actions in the operating procedures.

Feature #31 corresponds with the CAL ICM # 15. The results of Oconee Drill 2010-02 are documented in PIP. Proposed changes to EM 5.3 are captured in PIP actions to revise EM 5.3 and remain open. The next External Flood Mitigation related drills are scheduled for the first quarter of 2013.

5.2.5 Other Features Feature #35 is the last feature on the Flood Walkdown list and corresponds to the Site Elevation and Topography. NEL 12-07,'Appendix A, provides guidance on this topic as follows:

• Compare the current site topography with the topography assumed in the current licensing basis flood evaluation

• Assess differences to determine if they could affect water flow or flood levels and create vulnerabilities in existing flood protection features

• The need for a land survey for elevations will depend upon the accuracy of the applicable drawings and site topographical documents ONS had already begun an effort to accomplish the tasks listed above prior to the release of NEI 12-07. This feature is included in order to remain in compliance with NEI 12-07 and to track the progress of the Site Elevation and Topography effort. To date, the topography has been found to Page 18

Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 CONTIAINS SiCURIlI V *iN~ ! ILv II*IUfUKAI~ I IUI'.

be consistent with drawings and elevations assumed in plant documentation associated with the flood features, with the exception of the 6" sills protecting some Class 1 structures.

The #35 Flood Feature Walkdown items only represent features that the ONS Current Licensing Basis credits for flood mitigation.

There are other features on site, such as the temporary Intake Dike Flood Barrier and the permanent swale wall located above CTP-1, that ONS does not take credit for in the CLB. These items have not been included. These two items decrease flooding levels from a postulated Sunny Day Failure of Jocassee. The swale wall, which is located north of CTP-1, keeps CTP-l from being damaged during the event. The intake dike wall significantly lowers the water level in the yard from the first peak of flood waters.

The 10CFR 50.54(f) request for information regarding External Flooding does not include any internal source of flooding. Therefore many internal flood features onsite have not been included because their design and licensing basis is based on an internal source of flood waters.

5.2.6 Flood Warning Systems Oconee has no warning systems credited for external flood by the CLB to detect the presence of water in rooms important to safety. Oconee, as it is licensed, is considered a dry site and no water was assumed to enter buildings due to external flooding events. The only warning system put in place is the equipment listed as features 19-29. These are pieces of equipment that were either implemented prior to the CAL or because of the CAL. This equipment is what Jocassee uses to make a declaration of Condition A or Condition B of the Jocassee Dam.(Condition A and Condition B are the triggering events which initiate the Jocassee Dam Break scenario. These are described in detail in Emergency Procedures.) This equipment is critical for the success of Oconee in mitigating the External Flood due to Jocassee Dam Break.

5.3 DESCRIPTION

OF WALKDOWN PROCESS AND ACCEPTANCE CRITERIA In order to satisfy the requirements of the requested information in part 1.h of the Fukushima 10CFR 50.54 (f) letter Sectioni 2.3, staff at Oconee implemented walkdown strategies as provided by NEI 12-07 and supplemental guidance that was created by the Exelon group.

Section 1.h requests the following information:

1. h Verify that flood protection systems are available, functional, and implementable under a variety of site conditions by reviewing the following:

i. Operator availability, operator training, timeliness of response, equipment maintenance and operability, back-up availability, operator access under adverse site conditions ii. Methods and acceptance criteria to evaluate exterior barrier iii. Methods and acceptance criteria to evaluate incorporated barriers*

iv. Methods and acceptance criteria to evaluate temporary flood barriers

v. Preparations in advance of adverse weather conditions Page. 19

Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 Wlminoia 1rom pUwll Ui~ciUSUr¢ IJmuuuv zIj *.xx I..J..u/*

Oconee primarily implemented the methods that were recommended by NEI 12-07 for completing the walkdowns. Most of this information is found in Section 6 of NEI 12-07 which fully satisfies the requested information from Section 1l.h above.

Oconee used the NRC endorsed NEI 12-07 document for the walkdown procedure. No exceptions to the NEI 12-07 walkdown process were taken by Oconee. Accordingly, Oconee used the Walkdown forms presented in Appendix 1B of NEI 12-07 to perform the walkdowns. As a part of these forms, a peer review system is built in.

Oconee applied the provision in NEI 12-07 which allows other comprehensive walkdowns conducted within 2011 and 2012 to be credited for validation of flood protection features. These other walkdowns may be credited if the walkdown was performed and documented such that met the expectations in this guideline.' Many of the items on the Flood Feature list were walked down within the past year. In order to ensure that the scope of these previously performed walkdowns met the intent of NEI 12-07's guidance, a gap analysis was performed.

Features that were not walked down went through an intensive review of their PM programs, testing programs, and surveillance programs. None of these items were categorized as restricted or inaccessible. Features that were subject to controlled PM programs were evaluated to ensure that there was reasonable assurance of continued functionality. This information was documented in the walkdown records and has been summarized in this report. Even though some of the features were not walked down specifically for this exercise, the following activities were performed for each feature on the list:

• Ensured that the feature is included in a periodic test, monitoring, or inspection program

• Verified that the testing, monitoring, or inspection is being performed

• Determined if the scope of the test, monitoring, or inspection is adequate to confirm the credited flood protection function of the feature.

Any questionable observations were entered into PIP for disposition or were already in PIP and those PIP's were referenced. Additionally, all features on the list have been walked down this year, although not necessarily for this specific exercise. All walkdowns, were performed by Subject Matter Experts (SME's) either in CiVil or Mechanical design groups. These walkdowns were comprehensive in scope, looking specifically for degradation of features and signs of leakage. After reviewing the scope of each walkdown, all have been found to be acceptable in meeting the intent of NEL 12-07. Therefore it was determined that the provisions of Section 5.5 of NEI 1.2-07 were satisfied, and a re-performing a walkdown of these features would not be conducted.

Since Oconee's walkdown scope was relatively limited, it was decided that the minimum required participants could implement the task.

• Adam Johnson was chosen to be the lead engineer on the Flood Walkdowns. His background is based in the Civil Design Basis group. He was selected due to his prior Page 20

Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 WitbhIOlo from puD~lC uI(Isiill- U llUr = Juma ~F

,,-AU.. ... O~J1/41 knowledge of ONS licensing basis for flooding, and walkdown experience of current site features.

• Jim Weir was selected as the second walkdown team member. His background includes owning many different systems on site, as well as being a part of investigation teams in the past. He was selected based on his wealth of experience on site at ONS and his mechanical engineering background. This provided diversity to the walkdown team to protect against "group think" pitfalls.

This team satisfied the requirements of Section 5.3 of NEI 12-07, which includes requirements for knowledge of site current licensing basis, and experience with visual inspections of plant.

SSC's. The guidance outlined inl Table 1 of Appendix C to NEI 12-07 was fully met and was documented in the training portion of the Walkdown package. The walkdowns were specifically scheduled to avoid being performed simultaneously with other routine activities.

Some additional personnel accompanied the walkdown team, but their scope was limited to regular maintenance activities, such as opening cabinets. An OPS trained expert contributed to the Abnormal Procedure walkthr'ough and External Flood Mitigating Guidance Document walkthrough. A primary system engineer who authored the External Flood Mitigation Document also participated in the External Flood Mitigating Guidance Document walkthrough.

Section 7 of NEI 12-07 describes the peer review process for the flood walkdowns. Instead of obtaining a completely independent peer review, the walkdown forms have sign offs that constitute a peer review. Completion of the review signatures on the walkdown forms ensures the intent of the peer review, as described in NEI 12-07, was met. The walkdown forms with peer review signatures are retained as an attachment to the calculation that documents the walkdown results. ONS has not taken exception to the NEI 12-07 process and no actions resulted in a change to the walkdown process or methodology.

5.4 RESULTS OF WALK.DOWNS Based on the guidance of NEI 12-07, the walkdown process Was implemented for 11l flood features. The other flood features were accessed based on prior work and walkdowns completed within 2011 and 2012. The flood walkdowns, as directed and defined by NEI 12-07, only resulted in the finding of one deficiency. This deficiency is the out of service voltmeters located at the Keowee Spillway gates. By being out of service they cannot meet their intended design function, which is to monitor the voltage being used by the gate motors. This deficiency does not affect that actual operation of the spillway gate, but since the voltmeters are a NRC committed item and a FERC requirement, they are being described as a deficiency. There are no operability concerns due to this deficiency. This deficiency is documented in PIP. Operators still have the ability to manually connect volt meters to read voltage during gate operation. The volt meters are scheduled to be returned to service by the end of 2012. This deficiency was the only item requiring a reportability review in accordance with Regulatory Issues Summary 2005-20, R~ev 1, Revision to NRC Inspection Manual Part 9900 Technical Guidance, "Operability Conditions Adverse to Quality or Safety," to ensure that ONS was in compliance with our reportability process.

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Other PIP's were written in conjunction with the walkdowns. The scope of these PIP's range from missing Foreign Material Exclusion (FME) covers to PM program weaknesses. A brief description of each of the PIP's written is shown below for completeness.

1. During Flood procedure walkdown (AP-47) an obstruction was noted at one of the EFM Fire Hose Anchor Points.

2. AP/0/A/1 700/047 needs enhancement in description of site personnel evacuation of low lying areas due to External Flood.

3. AP/0/A/1700/047 needs enhancement on instruction to SSF operators to safely evacuate to higher ground as the flood waters over top the SSF exterior flood walls. Current process may put operators in an unnecessary personal safety risk.

4. The hard copy of Enclosure 5.5 of AP/0/A/1 700/047 that is "procedure staged" in the EFM trailer was found wet in its protective covering.

5. AP-47 reasonable simulation exercise associated with NRC 50.54(f) Flood Walkdown activities raised questions regarding Nuclear Equipment Operator (NEO) activities vs.

NEOs on minimum staff.

6. The EFM Hale Pump located at CTP-1 (based on oil in the Oil catchment) had a small oil leak. Also suction and discharge hoses need FME covers.

7. Cosmetic degradation of the concrete construction joint at the East wall and Floor Slab of SSF. Minor hairline cracking noticed in the grout pad of Exterior Flood Wall Support in Patio area.

8. Weaknesses discovered with EFM/Extensive Damage Mitigation (EDM) Hale Pump Fire Hose inspection and testing PMs.

9. During AP-47 field walkdowns at CTP-1, Precautions and Enhancements regarding the Pump Suction Pipe were identified.

10. Observation during AP-47 walkdowns regarding the potential impact of debris floating in CTP-1 water on the Hale Pump Suction Strainer.

11. A deficiency has been identified during the flood walkdowns. The Voltmeters at the Keowee Spillway were found out of service and had inadequate procedural direction.

A list of the features that were walked down for this report are listed below:

Feature #17: reasonable simulation. Some issues were found while performing this simulation.

Feature #18: reasonable simulation. Some issues were found while performing this simulation. None of these issues were deemed to cause the procedures to be non-effective.

Feature #23: inspected. A deficiency was discovered.

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Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 CO.'lTAi.!.fl fECUI.I'IT'. 2ErJ2TTr:r. Ir,.r2IT.IA7:*r.

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1. 2: nspctd.ItJ~ was found toUEI beLI~U copetl UIacceptable Feature #24: inspected. It was found to be completely acceptable.

Feature #25: inspected. It was found to be completely acceptable.

Feature #26: inspected. It was found to be completely acceptable.

Feature #28: inspected. It was found to be completely acceptable.

Feature #30: inspected. Issues were found with this item but these were not deficiencies.

Feature #32: inspected. It was found to be completely acceptable. PIP's were written to discuss issues found during this walkdown. These were either cosmetic of housekeeping issues and did not directly relate to the features ability to perform its function.

Feature #33: inspected. It was found to be completely acceptable.

Other PIP's were referenced in the walkdown forms for the items not walked down. Many of the features had previously been walked down within 2012 and ONS elected to not perform rework by re-walking these features down. Some issues exist with these features. Listed below are the flood features that were not re-inspected.

Feature # 1 was not reinspected, but also not completely acceptable. Issues currently exist with the Aux building below grade penetrations. PIP' s have been written to track the issues with Feature #1.

Feature #2 was not reinspected, but also not completely acceptable. Issues currently exist with the Radwaste trench covers to the turbine building. PIP's have been written to track the issues with this feature.

Feature #3 was not reinspected, but, also not completely acceptable. Issues currently exist with the Radwaste trench covers to the auxiliary building. PIP's have been written to track the issues with this feature.

Feature #4 was not reinspected, but also not completely acceptable. Issues currently exist with the Interim Radwaste trench covers to the auxiliary building. PIP's have been written to track the issues with this feature.

Feature #5 was not reinspected, but also not completely acceptable. Issues currently exist With Manhole 7. PIP's have been written to track the issues associated with this feature.

Feature #6 was not reinspected, and was found completely acceptable.

Feature #7 was not reinspected, but also not completely acceptable. Issues currently exist with the yard drain system. PIP's have been written to track the issues associated with the yard drain system.

Page 23

Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 Features #8 thrul 6, #1 9 thru 22, #27, and #31 were not re-inspected, and were found completely acceptable.

Feature #34 was not reinspected, but also not completely acceptable. Issues currently exist with the below grade SSF penetrations. PIP's have been written to track the issues with this feature.

Feature #35 was not reinspected, but also not completely acceptable. Issues currently exist with the Site Elevation and Topography. PIP's have been written to track the issues with this feature.

There were no flood features identified as restricted access or inaccessible feature. All features that were originally identified as CLB flood features were successfully walked down.

There were no Cliff Edge Effects entered into PIP. Cliff Edge Effects as defined by NEI 12-07 and the NRC's Near Term Task Force (NTTF) Report are: issues with the plant where "the safety consequences of a flooding event may increase sharply with a small increase in the flooding level." At ONS there is a postulated flood elevation of 815' ft msl. This is a flood of approximately 19' in the yard at some areas. Many structures are assumed to be completely flooded and fail. Cliff Edge Effects differ from Available Physical Margin (APM). The APM for each applicable flood protection feature is the difference between licensing basis flood height and the flood height at which water could affect an SSC important to safety. Determination of APM for local intense precipitation may not be possible. The APM information for the features listed above has been collected and can be found on the Walkdown Forms. This information will be used in the flood hazard reevaluations performed in response to Item 2.1: Flooding in the 50.54(f) letter.

Prior to starting the NTTF 2.3 Flood walkdowns, ONS had initiated detailed research for both the Jocassee Dam Break scenario as well as the PMP flooding scenario. Since the release of the NRC 50.54(f) letter ONS has had to reprioritize the design scope and schedule for its planned modifications to the plant to mitigate these different flooding scenarios. In accordance with the direction from Recommendation 2.1 Flooding from the NRC 50.54(f) letter, the ONS site flood hazards are currently being reanalyzed. Based on the results of this effort, new flood mitigating features will be designed and installed. However, based on the results of the 2.3 flood walkdowns, no immediate changes, other than those described above in the PIP system, will be made to ONS.

6.0 Compliance with NEI! 12-07, Appendix D The outline below was created to ensure the report above accommodates recommendations from, and is in full compliance with, NEI 12-07 appendix D. Each section of NEI 12-07 Appendix D is presented below with a page and section reference from the report above that fulfills its intent.

The items in italics are excerpts from NET 12-07.

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Flood Waikdown Report - NRC 50.54 (f) NTTF RecOmmendation 2.3

a. Describe the design basis flood hazard level (s) for allflood-causing mechanisms, including groundwater ingress.

• Identify all flood hazards that were evaluated in the site 's design basis and the flood level resultingfrom each. Identify hazards that were screened out.

i. Note that some flood hazards may be limitingfor flood level and some for other considerationssuch as warning time and dynamic loading.

Two flood hazards were identified. These hazards are the PMP flood event described in Section 5.1.1.1 and the Sunny Day Failure of Jocassee Dam described in Section 5.1.2.

No hazards were screened out because Oconee's only external flooding events are the PMiP and Jocassee Dam Break. Groundwater ingress is not a design or licensing basis flood hazard at Oconee, therefore this hazard was screened out.

• Describe any key assumptions (e.g., all culverts were assumed blocked)

No assumptions were made in this report. This is described in Section 4.

• Include information on the methodology used in developing the design basisflooding hazard No specific methodologies are described for the ONS PMP flood hazard as originally described in the UFSAR. Currently, HEC-RAS based models are being performed to address the PMP flood hazard reanalysis. Methodologies for determining the Jocassee Dam Break hazard are described in Section 5.1.2.

• If differences or"contradictionsinflood hazardlevels were found in design or licensing basis documentation, include a description of the basisfor flood level used As flood models develop further for the Jocassee Dam Break and the PMIP flood event, new flood levels are obtained. The flood levels described in the Safety Evaluation provided by the NRC for the Jocassee Dam Break scenario represent current design basis for the Jocassee Dam Break. The original PMP flood hazard as described in the UFSAR represents the current design basis for PMP flood.

b. Describe protection and mitigation features that are considered in the licensing basis evaluation to protect against external ingress of water into SSCs important to safety.

• Describe the flooding licensing basis including what plant configurations(modes of operation;for example. full power operations,startup, shutdown, and refueling) were considered This descriptionshould be consistent with the scope of the flooding walkdowns.

Oconee's flooding licensing basis includes two flooding events previously described: the PMP flood and the Jocassee Dam Break. Neither event takes into consideration modes of operation. These events are assumed to occur with minimurn required operating staff..

Page 25

Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3

- .T?_IBJ ir*"LttTV LYNETINFORMATION.

Document the flood duration assumed in the CLB. If the CLB does not provide information on the flood duration, this lack of information should be documented in the walkdlown report.

The PMP flood event is a 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> event as described in section 5.1.1.1. The Jocassee Dam Break event produces modeled flood levels in the Oconee yard f[or approximately 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, as described in Section 5.1.2.

• Describe the flood protection features that are credited in the CLB, such as incorporated, exterior and temporar~y barriers,time requiredfor creditedactions underflood conditions, active flood protectionfeatures, procedures, warnings creditedfor externalfloods, site drainageplan, etc..

The descriptions of the flood protection features that are credited in the CLB are located in Section 5.2. These descriptions make up a large portion of the report.

• Describe weather conditions orflood levels that triggerprocedures and associated actionsforproviding flood protection and mitigation.

The weather conditions that initiate the PMP flooding event are described in the Oconee Severe Weather Preparations procedure. Specifically these conditions include a rainfall in excess of 4 inches of rain in any 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> period. This procedure dictates actions to be taken prior to the weather event arriving. This is described in Section 5.1.I.1.

• Describe the adverse weather conditions that were assumed concurrent withflood protectionfeatures and associatedactions.

No other adverse weather conditions are assumed to occur concurrently with the flood protection features are associated actions. This is described in Sections 5.1.I. 1 and 5.1.2.

c. Describe any warning systems to detect the presence of wafer in rooms important to safety.

• Describe the room water level warning systems (e.g., alarms) credited for their flood protection function in the plant 's externaliflooding licensing basis No room water level warning systems are credited for flood protection in the plants external flooding licensing basis. This is described in Section 5.2.6.

• Note that systems that detect internalflooding sources are not part of the scope of the walkdown

d. Discuss the effectiveness offlood protection systems and exterior, incorporated, and temporary flood barriers. Discuss how these systems and barriers were evaluated using the acceptance criteria developed as part of Requested Information Item J.h.

Page 26

Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 vvZNTAIu,* " C C,, fl,, .IT ......... .I,* r1n.F i*P*MAT *Ip

• The purpose of the 2.3 walkdowns is to verif the conformance with the CLB; the adequacy of the CLB will be addressedas part of the 2. 1flood reevaluations if an integratedassessment is required All flood protection features were analyzed based on their licensing basis function. This is described in Section 5.2.

• The acceptance criteriafor the walkdowns are described in section 6 of the guideline.

This approach is consistent with requested information item 1. h of the 50.54(f) letter.

Discuss how the plant implemented this approach.

Oconee implemented the acceptance criteria as described in Section 6 of the NEI 12-07 guideline. Section 5.3 describes Oconee's walkdown process and the implementation of the NEI 12-07 guidelines.

• This discussion should include an evaluation of the overall effectiveness of the plant 's flood protectionfeatures to perform their creditedfunctions duringa variety of site conditions (as definedpreviously,), as determinedby the results of the walkdowns (the features are available,functional, and implementable). The CAP process will determine which of the walkdown observationsare deficiencies and what actions were taken or planned to address them. Questions such as the jollowing should be evaluatedfor a variety of site conditions:

The overall effectiveness of the features is described in Section 5.2.

i. ls the barriersystem functional?

All features were either deemed acceptable (functional) or the issues were identified as deficiencies.

ii. Are operatoractionsfeasible?

The reasonable simulations that were performed are described in Section 5.2.4. Operator actions were deemed feasible.

• Describe how other existingplant equipment, structures, andprocedures might mitigate the effects of fan externalflood under a variety ofplant configurations.

Oconee has specific mitigating plans for the licensing basis hazards.

i.Clearly describe what additionalexisting, if any, plant structures, systems, components, andprocedures that are not part of the flooding CLB and that could be used to mitigate an externalflood. Note that the Walkdown Report should include a description of existing plant capability, not an assessment ofplant vulnerabilitiesto flooding that might exist under all susceptible plant configurations. The assessment ofplant vulnerabilitiesto all.susceptible plant configurationswill be completed, if applicable, as part of an Integrated Assessment peiformed in response to Enclosure 2 of Reference 1 Page 27

Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3

- .ijL * -

i..... .L i.. ,it.., . .....J 10* C*.l2,2l i0 )()l.ri*~l*

There are a few features onsite that could be used to mitigate an external flood and are not part of the ONS CLB. These features are described in Section 5.2.5.

ii. Note: NUMARC 93-01, Rev 4A provides guidance on implementation of the maintenance rule. Section 11.3.4.2 of this document recommends an assessment of maintenance activities that expose SSCs to flood hazards in a mlanner that degrazdes their capability to perform key safety functions. Creditfor this activity could be included in this discussion.

All flood mitigating features that might be affected by maintenance activities are listed as Oconee PasSive Design Features. Items included on the Passive Design Feature list receive an extra level of oversight to ensure we do not degrade their capability to perform key safety functions. This is described in Section 5.2.1 .

e. Presentinformation related to the implementation of the walkdown process.(e.g., details of selection of the walkdown team andprocedures,) using the documentation temnplate discussed in Requested Information Item 1.j, including actions taken in response to the peer review.

Confirm that guidance wasfollowed (and options selected when availablewithin the guidance) and any exceptions taken to the guidance. See sections 5.3 7, Appendix B.

NEt 12-07 was followed and no exceptions were taken to the guidance. This is described in Section 5.3.

• Describe how the walkdlown teams were organized (e.g., number of members, general background, etc.). See sections 5.3 and 7.

There was only one walkdown team consisting of two members. The walkdown members and their backgrounds are described in Section 5.3.

• Describe the approach used to comply with section 5.3 guidance on Walkdown team selection and training.

The waikdown team was in full compliance with the training requirements set forth by NEt 12-07. This is described in Section 5.3.

f. Results of the ,walkdown including key findings and identijfieddegraded, non-conforming, or unanalyzed conditions. Include a detaileddescription Of the actions taken or planned to addressthese conditions using the guidance in Regulatory Issues Summary 2005-20, Rev 1, Revision to NRC Inspection ManualPart 9900 Technical Guidance, "OperabilityConditions Adverse to Quality or Safety," including entering the condition in the corrective action program.

Include the following items

• Descriptionof all deficiencies-as determinedby the CAP. Observationsthat are entered into the CAP and not dispositionedas deficiencies do not need to be. reporte~d Page 28

Flood Walkdown Report.-NRC 50.54 (f) NTTF Recommendation 2.3

~NTA1N3 JE2UflITY fTNfiITI"E VN!~f~W~ l~AA wflnnppu ii ujip p.uuii~ .IL~i. ....J.. 10 --,flr ,,2 n.1 ,.,d1I .

One deficiency was identified and was entered into PIP. This is described in Section 5.4.

• Descriptionof any observations reportedin the CAP that were not dispositionedat the time of the report "

All observations that were entered into the Corrective Action program were dispositioned at the time of the report.

• Describe actions that were taken or are plannedto address the deficiencies using the guidance in RegUlatory Issues Summary 2005-20 Revision 1.

The guidance in RegulatorY issues Summary 2005-20, Revision ! was taken into consideration for the deficiency that was discovered. This is described in Section 5.4.

• Flood protectionfeatures that could not be inspected, including All flood features were inspected. No items were Categorized as restricted access or inaccessible. This is described in section 5.4. The sub-items below are not applicable o Featuresaffected by restrictedaccess (see section 5.1):

- Justi~ficationfor delay

- Schedule

- Any necessary specialprocedures o Inaccessiblefeatures (see section 5.1J%"

- Basis for reasonable assurance that the feature is availableand will perform its creditedfunction or an assessment of the impact of non-peiformance of the function lf more than one "'inaccessible"flood protectionfeature wvith potential loss of function is reported, then an evaluation of the aggr'egate effect flood protectionfeatures must be provided.

• Walkdown recordforms are not submitted to the NRC, but as discussed in Section 7 are retainedonsite for NRC inspection The walkdown forms have been retained onsite and can be accessed for NRC inspection as described in Section 1.0.

g. Document any cliff-edge effects identified and the associated basis. Indicate those that were entered into the correctiveaction program. Also include a detailed description of the actions taken or planned to address these effects.

• Cliff edge effects andphysical margins do not need to be rePortedto the NRC as part of the Walkdown Report. However, the Alppendix B walkdown records, which include.

the collected 4PM information, need to be retainedand caailablefor NRC audits and inspections.

page 29

Flood Walkdown Report - NRC 50.54 (f) NTTF Recommendation 2.3 WIlfnfloIu iruuz puwlIt uul:.auiuuul uniit.~ .. . -,u ' ,.

The walkdown forms have been retained onsite and can be accessed for NRC inspection as described in Secti6rn 1.0.. ..

• . While the NRC used the same term :as the NTTF Report in its 50.54(0) information request (Reference 8.1) related to FloodingRecommendation 2. 3, the information that the NRC expects Utilities tO obtain duringthe Recommendation 2.3 walkdowns is /

different. To clarify, the NRC is now differentiatingbetween cliff-edgel effects (which are dealt with in Recommendattion 2.1) and a new term, Available Physical Margin (APM). APM information will be collected during the walkdowns, but will not be reported in the response to Reference 8.1, Enclosure 4. The APMs determinedby the Recommendation 2.3 walkdowns do not involve calculatingthe cliff-edge effects (i. e.,

the safety consequences). Duringthe Recommendation 2.1i integratedassessment, the cliff-edge effects and the associatedsafety risks will be determined using the APMs as well as other information, such as the specific SSCs that are subjected to flooding and the potential availabilityof other systems to mitigate the risk APM information has been collected. This is described in Section 5.4.

l nstead of submitting cli4ff-edge effects report thatAvailable PhysicalMarginsihave been collected and documented in the Walkdown Recordfi~rm (Appendix B). This information will be used in the flood hazardreevaluationsperformed in response to Itemn 2.1: Floodingin the 50.54(1) letter (Reference 8.1!).

Cliff edge effects are not being submitted. Available Physical Margins have been collected and documented. This is described in Section 5.4.

h. Describe any other planned or newly installed flood protection systems or flood mitigation measures including flood barriers thatfurther enhance the flood protecetion.

Identify results and any subsequent actions taken in response to the peer review.

• Describe changes determined to be necessary by the flood walkdowns and whether they have been completed or their schedulefor completion No other changes, other than those already initiated in the ONS CAP, will be made. This is described in Section 5.4.

• For the purposes of the flooding design basis walkdown verification, the peer review is the process describedin section 7. The only actions and results that should be

reportedare those that r'esulted in a change to the iwalkdown process or methodology.

Correctionsand resolution of differences resultingfrom the normalprocess of performer/ reviewer interactionare not repoQrted The peer review process as described in Section 7 of NEi 12-07 has been followed.. No changes have been made and therefore there are no reportable actions. This :is described in Section 5.3.

Page 30