ML14139A381

CALC-ANO2-CS-12-00002, Revision 1, Flooding Walkdown Report for Resolution of Fukushima Near Term Task Force Recommendation 2.3, Attachment 2 to 0CAN051402

ML14139A381
Person / Time
Site:	Arkansas Nuclear
Issue date:	05/14/2014
From:	Michael Lee Enercon Services, Entergy Nuclear Operations
To:	Office of Nuclear Reactor Regulation
Shared Package
ML14139A374	List: ML14139A379 ML14139A380 ML14139A381
References
OCAN051402 CALC-ANO2-CS-12-00002, Rev. 1
Download: ML14139A381 (21)

Text

Attachment 2 to OCAN051402 Arkansas Nuclear One, Unit 2 (ANO-2) Revised Flooding Walkdown Report

Engineering Report Number CALC-ANO2-CS-12-00002 Rev. I Page 1 of 20 a Entergy ENTERGY NUCLEAR Engineering Report Cover Sheet Engineering Report

Title:

Arkansas Nuclear One Unit 2 Flooding Walkdown Submittal Report for Resolution of Fukushima Near-Term Task Force Recommendation 2.3: Flooding Engineering Report Type:

New El Revision 0 Cancelled EL Superseded EL Applicable Site(s)

IPi EL IP2 Li IP3 EL JAF LI PNPS Li vY Li WPO Li AN01 E] ANO2 WF3 El PLP E:1 ECH Ei GGNS El RBS [:

EC Number 50803 Report Origin: EL Entergy Z Vendor Vendor Document Number: CALC-ANO2-CS-12-00002 Quality-Related: EL Yes Z No Prepared by: ENERCON/ Date:

Responsible Engineer (Print Name/Sign)

Design Verified/ N/A Date:

Design Verifier (if required) (Print Name/Sign)

Reviewed by: Chris Johnson / See Asset Suite Date: See AS Reviewer (Print Name/Sign)

Reviewed by: N/A Date:

ANII (if required) (Print Name/Sign)

Approved by: Ed Blackard / See Asset Suite Date: See AS Supervisor (Print Name/Sign)

is" CALC-ANO2-CS-1 2-00002 0 ENERCON 0 ENE CON mREV.

'*{Enteg y Page 21of 20 Revision,.. . . . . Record of ReWision Initial issue.

0 CALC-ANO2-CS-12-00002 is revised to report the results of the 2012, 2013, and 2014 flood protection walkdowns for Arkansas Nuclear One Unit 2 that were completed following the guidance of NEI 12-07, "Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features".

i

CALC-ANO2-CS-1 2-00002 0 ENERCON REV. 1 m,-m-%Entergy Page 3 of 20 ENGINEERING REPORT ARKANSAS NUCLEAR ONE UNIT 2 FLOODING WALKDOWN SUBMITTAL REPORT FOR RESOLUTION OF FUKUSHIMA NEAR TERM TASK FORCE RECOMMENDATION 2.3:

FLOODING Prepared By: Date: ___I_____0t_

Michael Lee (F;ercon Services, Inc.)

Reviewed By: Date: iAgg-ltvjito 4 "nic.,Crabtree Ene.r-6'n Services, Inc.)

Peer Reviewed By: _ Date: "-.'e/_

Wavel Justice (Enercon Services, Inc.)

Approved By: Date: /

-IL _

Atwood A. Browning (Enercon Services. ln-)

CALC-AN02-CS-1 2-00002 ENERCON REV. 1

.. *- . Page 4 of 20 TABLE OF CONTENTS Section Title Page 1.0 SCO PE AND O BJECTIVE .................................................................................. 5 2.0 DESIG N BASIS FLOO D HAZARD LEVEL ....................................................... 5 2.1 Flood Hazards Identified ......................................................................... 5 2.2 Assum ptions ........................................................................................... 6 2.3 Methodology ........................................................................................... 7 2.4 Non Conformance .................................................................................. 7 3.0 EXTERNAL FLOOD PROTECTION AND MITIGATION FEATURES ................ 7 3.1 Flooding Licensing Basis .......................................................................... 7 3.2 Flood Duration ......................................................................................... 8 3.3 Flood Protection Features ....................................................................... 8 3.4 Procedures ............................................................................................. 9 3.5 Adverse W eather .................................................................................... 9 4.0 INTERNAL W ARNING SYSTEMS .................................................................. 10 4.1 Room W ater Level W arning Systems ................................................... 10 5.0 EFFECTIVENESS OF FLOOD PROTECTION SYSTEMS ............................... 10 5.1 Acceptance Criteria ................................................................................ 10 5.2 Discussion ............................................................................................. 12 6.0 IMPLEM ENTATIO N O F WALKDOW NS ........................................................... 14 6.1 Flood Protection W alkdowns ................................................................. 14 6.2 NEI-12-07 Guidance ............................................................................. 14 6.3 Team O rganization ................................................................................ 15 6.4 Training Approach .................................................................................. 15 7.0 W ALKDOW N RESULTS ........................................... ........................................... 15 7.1 Deficiencies ........................................................................................... 16 7.2 O bservations ......................................................................................... 17 7.3 Corrective Actions .................................................................................. 17 7.4 Flood Protection Features Not Inspected ............................................. 17 8.0 AVAILABLE PHYSICAL MARG IN................................................................... 19 9.0 NEW FLOOD PROTECTION SYSTEMS ............................. 19

10.0 REFERENCES

.................................................................................................. 19 11.0 ATTACHM ENTS ............................................................................................... 20

"CALC-ANO2-CS-1 2-00002 ENERCON tREV. 1 Page 5 of 20 1.0 SCOPE AND OBJECTIVE This report was developed to provide information requested by the United States Nuclear Regulatory Commission (NRC) pursuant to Title 10 of the Code of Federal Regulations (CFR), Section 50.54(f) on March 12, 2012, for Arkansas Nuclear One (ANO) Unit 2 (Ref.

10.1). In response to the NRC request, Entergy performed walkdowns to verify that plant features credited in the current licensing basis (CLB) for protection and mitigation from external flood events are available, functional, and properly maintained. The walkdowns were performed to verify that structures, systems, and components (SSCs), portable flood mitigation equipment, and the procedures needed to install and/or operate them during a flood are acceptable and capable of performing their design function as credited in the CLB.

This report presents the findings of the flooding walkdown inspections completed at ANO Unit 2 in 2012, 2013, and 2014, as discussed in Section 6.1 of this report. The walkdowns I were completed following the NRC endorsed guidance of Nuclear Energy Institute (NEI) 12-07, Rev. 0-A, Guidelines for Performing Verification Walkdown of Plant Flood Protection Features (Ref. 10.3) and Entergy Nuclear procedure EN-DC-170 (Ref. 10.4) that was developed to provide instructions for implementation of the NRC endorsed guidelines. In addition to verifying that site flood protection features are acceptable and capable of performing their design function, the walkdowns were also used to verify that plant modifications implemented since original construction, such as changes to topography, do not adversely affect flooding protection.

This report identifies the flooding hazards that comprise the CLB and the protection and mitigation features that are credited with preventing the ingress of external water into safety-related SSCs at ANO Unit 2. The effectiveness of the flood protection features is evaluated against a set of acceptance criteria. Results of the walkdowns, including key findings, available physical margin, and any identified degraded, or nonconforming conditions are addressed, and a description of the actions taken or planned to address these conditions is provided.

2.0 DESIGN BASIS FLOOD HAZARD LEVEL Sections 2.4 and 3.4 of the ANO Unit 2 Safety Analysis Report (SAR) (Ref. 10.5) describe the design basis an d flood protection features provided at ANO Unit 2 for protection against an external flood, respectively.

2.1 Flood Hazards Identified ANO Units 1 & 2 are adjacent nuclear plants located on a peninsula that extends into the Dardanelle Reservoir. The plant is centrally located on the peninsula with a grade elevation (near the center of the site) of 353' above Mean Sea Level (MSL). The peninsula is about two miles wide and two miles long. The plant is surrounded on three sides by the Dardanelle reservoir. The shortest stretch of land is approximately one mile in a southeast direction. The ground surface surrounding the plant is predominantly meadow.

CALC-ANO2-CS-1 2-00002 OENERCON REV. 1 E. ;e- Page 6 of 20 The Dardanelle Reservoir is part of the Arkansas River navigation project. The Dardanelle Dam impounds the Arkansas River, creating the Dardanelle Reservoir (also known as Lake Dardanelle). The dam is managed and controlled by the United States Army Corps of Engineers (USACE). The level of the reservoir I fluctuates between 336' (normal pool) and 338' (maximum controlled pool) above MSL. The upper end of the Dardanelle Reservoir lies beneath the Ozark Dam, which is approximately 51 miles upstream.

The safety-related structures, or Seismic Category 1 structures, at ANO Unit 2 are capable of withstanding the worst flooding caused by a combination of hypothetical events. The Probable Maximum Flood (PMF) level is 358' above MSL considering maximum probable flooding flows and a maximum flood level on the downstream side of the Ozark Dam. An instantaneous failure of the Ozark Dam coupled with the PMF results in a maximum potential flood level of 361' MSL. The effects of wind and wave action on a PMF event would add approximately 2.5' to the PMF of 358' MSL, or approximately an effective 360.5' MSL flood level. Therefore, the combined effects of wave action and PMF are bounded by the combination of a hypothetical Ozark Dam failure event and PMF event and thus the design flood elevation for ANO Unit 2 was determined to be 361' MSL. According to the ANO Unit 2 SAR, critical equipment and components are protected from splash effects up to 10' above the PMF level of 358' MSL (i.e. 368' MSL) as follows: "...critical equipment and components are either protected or are located above Elevation 369 feet".

Groundwater intrusion into safety-related structures is considered a potential source during flooding events. The design of the Seismic Category 1 structures considers the source as credible and provides protection against groundwater intrusion into these structures as low as the base grade level at elevation 317' MSL. Minor seepage into the Seismic Category 1 structures is anticipated and discussed in ANO Unit 2 SAR, Section 3.4.4.1.

The effects of local intense precipitation on the site are bounded by the effects of a PMF coupled with a hypothetical Ozark Dam failure event. The Auxiliary Building Roof is structurally designed to withstand roof ponding loads; the Auxiliary Building Roof drainage is sufficient to protect safety-related equipment; and the site drainage is not credited for flooding protection.

2.2 Assumptions No assumptions apply to establish a CLB thr eshold with respect to wind and waves. As discussed above the effect of wind and waves were considered but were bounded by the combination of a PMF and Ozark Dam failure events and thus do not apply.

With the exception of watertight doors and hatches, the ANO Unit 2 SAR is silent with respect to non-piping penetrations being a credible flooding pathway.

Therefore, it is assumed that when the SAR refers to piping penetrations being sealed, it implicitly also includes conduit, HVAC, and other similar penetrations that pose a credible flooding pathway and that they should be similarly sealed.

CALC-ANO2-CS-1 2-00002

-E n te r g ENF_.RCON REV. 1 b~4A6-.'r rrrV~dy 'M Page 7of 20 2.3 Methodology The PMF for the Arkansas River is estimated based upon the projected flood defined by the USACE (Ref. 10.5). USACE has computed the maximum probable flood flow at the Dardanelle Dam as 1,500,000 cubic feet per second. At this flow, the water level at the Dardanelle Dam would be 353' MSL. The upper end of the Dardanelle Reservoir is at the Ozark Dam, about 51 miles upstream. During PMF conditions, the level of the Dardanelle Reservoir at the downstream side of Ozark Dam would be 389.5' MSL. No profile for t his condition is available, but it is reasonable to assume a straight-line variation. On this basis, the PMF level at the plant site is 358' MSL.

Wind and wave activity are considered but are bounded by the possibility of a coincidental Ozark dam failure with the PMF. For the pur pose of the estimate of wind and wave activity, the results indicate an approximately 2.5' increase in effective flood level and utilized a calculation input for wind speeds of 45 mph from the south west direction and a fetch of 18,000' (Ref. 10.5).

Evaluation of the instantaneous and coincidental Ozark dam failure with the PMF determines a theoretical water level rise of 6.8', but then describes this outcome as "so unlikely as to be practically impossible." The estimate uses a uniform river channel assumption which is considered very conservative. Furthermore, an additional 50 square miles of flood plain would be a consequence not accounted for in the original computations and it wo uld result in a "great amount of ext ra storage". Therefore, the calculation estimates a 3' rise in flood elevation over the PMF level of 358' MSL. Thus, t he overall design basis for t he ANO site was calculated to be 361' MSL.

2.4 Non Conformance No differences or contradictions in flood hazard levels were found in design or licensing basis documentation.

3.0 EXTERNAL FLOOD PROTECTION AND MITIGATION FEATURES 3.1 Flooding Licensing Basis The safety-related structures at ANO are designed to withstand the worst flooding I caused by a combination of hypothetical events. These events are the probable maximum flood of the Arkansas River coinciding with the Ozark Dam failure.

Based on the ANO CLB, the current maximum design basis flood level is 361' MSL. Critical components and equipment are protected by flood rated Seismic Category 1 structures or placed at elevations above 369' to protect against splash effects.

The following Seismic Category 1 structures are designed to withstand external flooding: Unit 2 Reactor Building, Unit 2 Auxiliary Building, Emergency Diesel Fuel Storage Vaults, and the Post Accident Sampling System (PASS) Building, and portions of the Unit 2 Intake Structure that house the Service Water System.

ENERCON dCALC-ANO2-CS-1 REV. 1 2-00002 Et Page 8 of 20 The Unit 2 Technical Specifications (Ref. 10.6) state that "Flood protection shall be I provided for all safety-related systems, components and structures when the water level of the Dardanelle Reservoir exceeds 350 feet Mean Sea Level USGS datum, at the intake structure". This statement imposes that closure of identified openings and penetrations is required to be initiated and complete within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of the water level at the Intake Structure reaching an elevation of 350' MSL. The Technical Specifications state that the water level at the Intake Structure shall be determined according to the level thresholds below:

a. Measurement at least once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> when the water level is below elevation 350 feet Mean Sea Level USGS datum, and

b. Measurement at least once per 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> when the water level is equal to or above elevation 350 feet Mean Sea Level USGS datum.

3.2 Flood Duration Section 9.5.4.1 of the ANO Unit 2 SAR (Ref. 10.5) states that "Based on conservative estimates for the Corps of Engineers it is expected that the probable maximum flood could be above plant grade (Elevation 353 feet) for a duration of two to five days".

3.3 Flood Protection Features Safety-related systems and components are flood protected either because of their location above the design basis flood level, or because they are enclosed in reinforced concrete Seismic Category 1 structures, per ANO Unit 2 SAR, Section 3.4.4 (Ref. 10.5).

Each of the Seismic Category 1 structures discussed in Section 3.1 of this report is protected by the following design criteria:

• Wall thicknesses below flood level are a minimum of two feet.

• Waterstops that are provided in construction joints below flood level.

• The number of openings in walls and slabs below flood level are kept to a minimum.

• Waterproof doors and equipment hatches are installed.

With respect to the Reactor Building, the Equipment Hatch, and the Building Escape Hatch are double sealed openings. The Tendon Gallery Access Hatch is protected using a water tight hatch cover.

With respect to the Auxiliary Building, door openings are protected utilizing watertight doors; floor openings are protected utilizing watertight hatch covers; roof openings over underground vaults are protected utilizing concrete plugs with neoprene seals; conduit and HVAC penetrations are ext ernally and internally sealed as necessary, and pipe penetrations are protected utilizing seals or closure I plates.

With respect to the Emer gency Diesel Fuel T ank Vaults, door o penings are protected utilizing watertight doors; roof openings are protected utilizing concrete

do ECALC-ANO2-CS-1 2-00002 OENERCON REV. 1

-tee a..J4d -- myEPage 9 of 20 plugs with neoprene seals; conduit penetrations are externally and internally sealed, and pipe penetration are protected utilizing seals or closure plates.

With respect to the PASS building, door openings are protected utilizing watertight doors; conduit penetrations are externally and internally sealed; and pipe penetrations are protected utilizing seals or closure plates.

As stated in the ANO Unit 2 SAR, through-wall leakage will be controlled by sumps and sump pumps. However, through-wall leakage will be very small and the seepage into the Seismic Category 1 buildings would be of such minute quantity that the failure of the sump pumps would have no adverse effect on the flood protection of the buildings.

3.4 Procedures ANO Unit 2 operating procedure for natural emergencies describes the actions to be taken in the event of plant flooding caused by natural phenomena at the site.

This procedure provides actions to be taken based on different levels of the Dardanelle Reservoir as measured at the Unit 2 Intake Structure. In order to maintain offsite power to the plant, temporary jumper cables are installed from the 161 kV Pleasant Hill transmission line to Startup Transformer #2.

ANO's site preventative maintenance procedures address the required maintenance for components, such as doors and hatches, utilized in procedural actions in order to maintain flood protection. The inspection interval of the doors and seals is not associated with a specific water level or flood situation at ANO but is established as part of the maintenance work order planning system.

Entergy Corporate procedures associated with condition monitoring of maintenance rule structures, per 10 CFR 50.65, provide the programmatic instructions for preventative maintenance and surveillance for the Seismic Category 1 structures that are protected from flooding.

3.5 Adverse Weather In accordance with the ANO Unit 2 operating procedure for natural emergencies, flood protection measures are required to be installed, such as temporary flood barriers, for protection of safety-related systems and components during flooding conditions. Based on the CLB, Unit 2 watertight doors are assumed to remain closed or be verified as closed during a flooding event. The ANO Unit 2 natural emergencies procedure provides instructions to secure the doors as part of the response in accordance with anticipated and measured flood levels. Some doors I and hatches cannot be accessed without requiring personnel to travel outdoors.

However, these doors and hatches are maintained in a normally closed position, thus adverse weather impacts are not considered a credible hindrance to thie flooding response.

CALC-ANO2-CS-1 2-00002 OENERCON REV. 1

__c__'_,,__-__.*_-:__,__

E?..EIte'j Page l0of 20 4.0 INTERNAL WARNING SYSTEMS 4.1 Room Water Level Warning Systems No interior water level warning systems or alarms are credited for external flood protection in the plant's CLB.

5.0 EFFECTIVENESS OF FLOOD PROTECTION SYSTEMS 5.1 Acceptance Criteria The flood protection features credited in the CLB for Arkansas Nuclear One Unit 2 I are incorporated active and passive features and include watertight doors and door seals, exterior structural walls, penetration seals through exterior walls, neoprene sealed hatches, sumps, sump pumps, check valves, and Reactor Building, Auxiliary Building and Tendon Gallery equipment and escape hatches. The site topography, and existing drainage ditches and culverts are not licensing basis credited features for flood protection although natural drainage patterns and drainage designs are consistent with ensuring that flood waters drain away from protected areas and that critical equipment and systems are in elevated areas where applicable. These flood protection features were visually inspected following the acceptance criteria described in NEI 12-07, Section 6 (Ref. 10.3) document I and as discussed below.

ANO Unit 2 maintenance procedure for watertight doors was used as a reference to determine the acceptance criteria for the doors. Based on the instruction, the seals are to be installed between the door and t he frame, with the seal being slightly compressed and maintaining solid contact at all locations. Therefore, with the door closed, the seal was visually inspected to ensure no gaps are seen between the seal and the door. The door was then opened to inspect the seal and ensure that no visible cracks or deterioration was present. The sealing mechanisms and latches were inspected for functionality. The seal was determined to be acceptable ifthere appeared to be contact between the seal and door at all points, no degradation or deterioration on the seal was observed, and the seals on the doors were installed to an elevation that ensure the door was protected to the maximum elevation of 361' MSL.

Seismic Category 1 structures at ANO U nit 2 are protected from the effects of a design basis flood based on the hardened flood protection approach and include the following structures: the ANO Unit 2 Reactor Building, the ANO Unit 2 Auxiliary Building, the Emergency Diesel Fuel Vault, the PASS Building, and portions of the Intake Structure. The hardened approach requires structural provisions, such as watertight doors and penetrations to be incorporated into the plant design to protect safety-related structures, systems, and components from the effects of a flood. Based on the hardened approach the following walls, ceilings, and floors, including the associated penetrations, were required to be walked down as they were located on the exterior of the structure and were not shielded from potential flooding by ot her structures: the exposed Western portion of the ANO Unit 2 Reactor Building at elevations 335' and 354'; the North, South, East and West

CALC-AN02-CS-1 2-00002 ENERCON EI e REV. 1 JL'y Page 11 of 20 exterior walls of the ANO Unit 2 Auxiliary Building and Auxiliary Building Extension at elevations 317', 335', and 354'; the exterior North, South East, West Walls and associated ground level covers of the Emergency Diesel Fuel Vault; and the exterior PASS Building West wall at elevation 354' and East wall adjoining the ANO Unit 2 Auxiliary Building at elevation 354'. The walls and penetrations act as an external flood barrier and prevent water intrusion into the structures.

Groundwater may be present near the ground surface, therefore flooding sources from below the ground surface are considered. Exterior walls below grade were inaccessible from the outside; therefore, the walls were inspected from the interior.

Drainage characteristics associated with site topography are not a credited CLB feature. However topography was visually inspected against the ANO site drainage drawings. The walkdowns visually verified that the topography of the site allowed water to drain as depicted in the drawings. Engineering changes including those completed for security reasons were reviewed to ensure that any obstructions or changes made to the site did not adversely impact site flooding protection.

The site is required to provide drain and scupper inspection on the Unit 2 Auxiliary Building roof to ensure the drains and scuppers are not blocked in order to provide adequate drainage and limit roof ponding, which is not to exceed structural design limits in the event of local intense precipitation. The Unit 2 Auxiliary Building roof scuppers and roof drains are maintained free from debris and blockage.

Walkdowns were completed to confirm the Unit 2 Auxiliary Building roofs were free of any potential blockage or debris that could impede roof drainage.

Portions of the ANO Unit 2 Intake Structure are Seismic Category 1 structures.

Walkdowns were completed in these areas to determine if Seismic Class 1 equipment in these areas was adequately protected against flooding. Equipment inspected includes control boards, switchgear, load centers, batteries, transformers and cable runs serving Seismic Class 1 equipment. The Seismic Class I equipment is namely the Service Water System, which includes service water pumps, valves, connecting piping, and intake structure sluice gates. Equipment likely to be rendered inoperable due to flooding was walked down to determine if the equipment was protected by a Seis mic Category 1 structure or whether the equipment was above the 369' elevation.

The ANO Emergency Cooling Pond Intake and Discharge Structures are Seismic Category 1 structures, but are not specifically discussed in the CLB as providing flooding protection. These areas were walked down to ensure that protection was evident in the event flooding was to occur that might transport debris and render these systems inoperable due to blockage. The acceptance criteria for these features were to verify the presence of trash racks and debris blocking features.

Unit 2 Auxiliary Building sumps and sump pumps are a credited licensing basis flood protection measure. Therefore sumps, sump pumps, and level instrumentation were visually inspected following the acceptance criteria described in NEI 12-07 and EN-DC-170 (Ref. 10.4).

] CALC-ANO2-CS-1 2-00002 ENERCON REV. 1

• '*.e,*+.,p~oEn. t, Page 12 of 20 ANO Unit 2 operating procedure for natural emergencies provides instructions for site responses to flooding events. This procedure also provides the instructions to contact a third party to install jumpers from the Pleasant Hill 161 kV transmission line to the Startup Transformer #2.

The ANO Unit 2 operating procedure for natural emergencies was tested, via a Reasonable Simulation, in a step-by-step manner through posing questions to address the guidance found in NEI 12-07, Section 5.5.6. Namely:

1. Can the procedural step be executed as written?

2. Can any time dependent activities be completed in the time frame required?

3. Are specified equipment or tools properly staged and in good working order?

4. Will completion of the activity not be impeded by the flood event?

5. Is it certain that there is no over reliance on the staff and that the staff can complete the necessary steps?

The acceptance criteria are positive answers to the above questions against each procedural step.

Observations which were not immediately able to be judged as acceptable on the walkdowns were entered into the ANO Corrective Action Program (CAP) to allow for a more detailed evaluation to be completed (See Section 7.1 for deficiencies).

5.2 Discussion 5.2.1 Overall Effectiveness The ANO Unit 2 flood protection and mitigation features were either determined to be operable as found, promptly repaired to restore operability, or addressed with compensatory measures to maintain operability. These determinations are based on results of the operability determinations associated with the observations that were entered into the site CAP system.

Except as noted in Sections 7.1 and 7.2; Walls, ceilings, floors, and penetrations located below 362', 1' above the CLB flood level of 361', were walked down to ensure no credible flood pathways exist and to support available physical margin (APM) determination (Ref. Section 8.0 of this report).

Doors and door seals were observed to ensure the proper operation of water tight doors, and were found to be in working order with proper seals, and that their function would not allow flooding of structures.

Site topography, although not a credited flood protection feature, was verified against site drainage drawings and was determined to not direct flood waters towards protected features.

Critical water-sensitive equipment and components installed in the Unit 2 Intake Structure Building were observed to be above CLB 361' MSL.

Furthermore, they were confirmed to be splash protected.

CALC-ANO2-CS-1 2-00002 O ENERCON REV. 1 E--o ty *Page 13 of 20 The Emergency Cooling Pond Intake and Discharge structures were confirmed to have debris blocking features.

Unit 2 Auxiliary Building Roof Drains and Scuppers were observed to be free from debris and able to provide the required drainage.

The Unit 2 Auxiliary Building sump pumps and level instrumentation were observed to be in working order and were verified as being maintained.

The reasonable simulations applied to the ANO Unit 2 operating procedure for natural emergencies posed 5 guidance questions, per NEI 12-07, Section 5.5.6 (Ref. 10.3). These questions were to be answered in the affirmative for each of the procedural steps in order for the simulation of each step to be acceptable.

During the walkdowns, conditions that did not meet the acceptance criteria discussed in Section 5.1 of this report were entered into the CAP at ANO. I 5.2.2 Other SSCs and Procedures Entergy Corporate procedures associated with the Maintenance Rule Program provide the guidance and requirements for conducting a structural condition monitoring program to meet the requirements of 10 CFR 50.65. At ANO Unit 2, Maintenance Rule walkdowns are conducted a minimum of every five (5) years and are completed in accordance with the procedures. This program provides a systematic approach for evaluation of plant systems/structure which will provide a reasonable assurance that the structures are capable of fulfilling their design basis functions. The program consists of periodic reviews of the condition of the plant structures via periodic inspections, routine walkdowns, surveillance tests, and ongoing review of the effect of the condition of plant structures on significant plant equipment. The program consists of defining and performing periodic structural evaluation which will ensure the timely identification, assessment, and repair of degraded structural elements. Concrete structures and penetration seals are inspected for cracking, spalling, erosion, corrosion of reinforcing bars, settlement, deformation, leaching, discoloration, groundwater leakage, rust stains, exposed rebar, rust bleeding, and other surface irregularities. Flood barriers and seals, watertight doors, hatches, and internal conduit seals, were determined to be within the scope of the Maintenance Rule procedure and are, therefore, examined in accordance with this procedure. Maintaining the structures and materials monitored under this procedure provides a reasonable assurance that those structures, that fall under the program, will be able to per form their intended function.

The Auxiliary Building and Emergency Diesel Fuel Vault are equipped with floor drainage systems. Water entering these structures would flow across sloped floors and enter the floor drainage systems to be collected in sumps at the bottom floor elevations. The CLB takes credit for the control of local seepage through walls via sumps and sump pumps.

CALC-ANO2-CS-1 2-00002 AJ ENE RC O N REV. 1 EPage 14 of 20 6.0 IMPLEMENTATION OF WALKDOWNS 6.1 Flood Protection Walkdowns Walkdowns were organized for ANO Unit 2 in 2012 using the NEI 12-07 guidance (Ref. 10.3). The walkdowns performed in 2012 inspected flood protection features and attributes. Discrepant conditions were identified and entered into the CAP.

Summary reports were submitted to the NRC to document the performance of the flood protection walkdowns in accordance with NRC Letter to Licensees (Ref.

10.1), which included a list of restricted access features requiring inspection by September 30, 2013 (Refs. 10.7 and 10.8). In 2013, the restricted access features were inspected. However, following review of the 2012 flood protection walkdown report and observations during the 2013 walkdowns, it was discovered that discrepancies existed in the 2012 walkdown report that required additional walkdowns to resolve (Ref. 10.9). These discrepancies were entered into the CAP.

Based on an assessment of the 2012 flood protection walkdown report for ANO Unit 2, walkdowns were performed in 2014 to address discrepancies. A majority of the 2012 walkdowns were re-performed. Examples of these discrepancies were associated with ductwork, ceiling/floor areas, and embedded features such as floor drain connectivity and embedded conduit routing. Potentially deficient conditions were entered into the CAP.

6.2 NEI-12-07 Guidance The verification walkdowns were performed following the NRC endorsed guidance of NEI 12-07 (Ref. 10.3) and Entergy Nuclear procedure EN-DC-170 (Ref. 10.4) that was developed to provide instructions for implementation of the NRC endorsed guidelines. Additional guidance for implementation was also obtained from the NEI 12-07 Frequently Asked Questions (FAQs) and the N RC Request for Additional Information (RAI) (Ref. 10.2).

The basis for establishing the walk down scope and the flood protection and mitigation features included the preparation of a walkdown list following the guidance provided in NEI 12-07, Section 4. As part of this preparation, the CLB was reviewed to determine the flood protection and mitigation features and actions that are necessary to prevent an external flooding event at the site from adversely impacting safety-related SSCs. In addition to the identification of passive and active flood protection and mitigation features, existing site and Entergy Corporate procedures were reviewed to determine if any procedures were necessary to ensure existing flood protection and mitigation features would be functional in the event of a flood at the site.

Walkdown packages were prepared following the guidance provided in NEI 12-07, Section 5.2 and walkdown team personnel were selected based on the requirements provided in NEI 12-07, Section 5.3.

Prior to each walkdown, a pre-job brief was conducted. Walkdown results were documented in accordance with the recommendations of NEI 12-07, Section 7 on the Flooding Walkdown Record Form provided in Attachment 9.3 of EN-DC-170.

dCALC-ANO2-CS-1 2-00002 SENERCtON REV. 1 LJa nPage E 15 of 20 The walkdown record form provided in Attachment 9.3 is consistent with the record form template provided in Appendix B of NEI 12-07.

6.3 Team Organization Consistent with NEI 12-07, Section 5.3 (Ref. 10.3), the walkdown team consisted I of two trained individuals with a complementary set of skills. The walkdown team consisted of two degreed engineers (or equivalent), who had familiarity with the site. During the 2012 walkdowns, the walkdown team was su pplemented, as required, by plant maintenance and/or operations personnel. For the 2014 walkdowns, Entergy provided qualified engineering personnel to provide oversight of the inspections and review of the findings.

6.4 Training Approach Consistent with Section 5.3 of NEI 12-07 (Ref. 10.3) and Section 4.1 of EN-DC-170 (Ref. 10.4), personnel selected to perform walkdown inspection activities were experienced and knowledgeable of the site CLB. Personnel were also trained to perform the visual inspections and met the knowledge requirements specified in EN-DC-1 70 and Appendix C of NEI 12-07. Team members associated with the flooding walkdowns also satisfactorily completed the INPO's NANTEL Generic Verification Walkdowns of Plant Flood Protection Features lesson and were knowledgeable of the 10 CFR 50.54(f) letter dated March 12, 2012 (Ref. 10.1) and the NRC RAI (Ref. 10.2).

Entergy personnel who provided walkdown oversight were trained to perform the visual inspections and were qualified to the requirements specified in EN-DC-170 and NEI 12-07.

7.0 WALKDOWN RESULTS A total of 180 walkdown packages were associated with the walkdowns completed for ANO Unit 2. This set includes 80 packages for the 2012 walkdowns, with each package containing a single feature. The features and attributes walked down as part of this package are categorized by flood protection type (incorporated passive, temporary passive, incorporated active, and temporary active) as shown in Table 1 below:

Table.1: Summary.- Features Included in the WailkdownScope. ...

Flood Protection Type Total Number of Features Total Number of Attributes Passive - Incorporated 79 988 Passive - Temporary 0 0 Active - Incorporated 1 18 Active - Temporary 0 0

CALC-ANo2-CS-1 2-00002 ENERCON --- t-REV.1 Page 16 of 20 The total set of walkdown packages also includes 7 packages for the 2013 walkdowns and 93 walkdown packages for the 2014 walkdowns. The features that were inspected are listed below:

" Unit 2 Auxiliary Building, EL. 317' - Reinforced Concrete Walls and Floors

• Unit 2 Auxiliary Building, EL. 335' - Reinforced Concrete Walls, Floors, and Ceilings

" Unit 2 Auxiliary Building, EL. 354' - Reinforced Concrete Walls and Floors

• Unit 2 Auxiliary Building - Floor Drains and Check Valves

" Unit 2 Auxiliary Building - Sumps and Sump Pumps

• Unit 2 Auxiliary Building - Roof Drains

" Unit 2 Intake Structure Building

• Unit 2 Reactor Building Tendon Gallery, EL. 317' - Reinforced Concrete Walls and Floors

• Unit 2 Reactor Building, EL. 336'-6" - Reinforced Concrete Walls

• Unit 2 Reactor Building, EL. 357' - Reinforced Concrete Walls

• ANO Emergency Diesel Fuel Tank Vault - Reinforced Concrete Walls, Floors, and Ceilings

• ANO PASS Building - Reinforced Concrete Walls

" ANO Emergency Cooling Pond Intake Structure

• ANO Emergency Cooling Pond Discharge Structure

• ANO Site Yard Drainage

• ANO Site Yard Manway

• ANO Start-up Transformer #2 Bus Duct Attributes associated with the features are detailed in the walkdown packages. Also, a reasonable simulation was performed for the Flooding section of the ANO Unit 2 operating procedure for natural emergencies.

7.1 Deficiencies As stated in NEI 12-07 (Ref. 10.3), a deficiency exists when a flood protection feature is unable to perform its intended flood protection function when subject to a design basis flooding hazard. During the flooding walkdowns for ANO Unit 2, there were several conditions of features that did not meet the NEI 12-07 acceptance criteria and, therefore, entered into the CAP. The follow ing are examples of deficient or potentially deficient conditions that were observed in the flood protection features; the majority of which were related to penetration seals:

" Degraded or missing seals at piping penetrations

• Degraded or missing internal and external seals for conduits

" Degraded or missing seals at HVAC penetrations

" Degraded hatch gaskets

" Missing removable flood closure plate for HVAC duct

• Floor drain system that cross-connects between flood protected areas and non-flood protected areas

CALC-ANO2-CS-1 2-00002 ENERCON E 0

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• Flood pathways through abandoned-in-place systems

" Ground water intrusion through building joints and penetrations 7.2 Observations Condition reports that were written due to a potential deficiency for a flood protection and mitigation feature were input into the CAP. Based on the operability determinations associated with the condition reports, features were either determined to be operable as found, promptly repaired to restore operability, or addressed with compensatory measures to maintain operability.

7.3 Corrective Actions In 2012 there were no observations identified that required actions to address a deficiency. The CAP did initiate a work order to repair a watertight door in order to restore available flood margin back to design conditions. The watertight door was observed to be in a degraded condition with evident gaps between the door and door seal at the top of the door. This observation was not a deficiency as the gap was above the CLB flood level of 361'.

In 2013, based on deficiencies observed in the Auxiliary Building Extension, water would potentially enter the Auxiliary Building Extension during a design basis flood.

The Auxiliary Building Extension does not house any safety-related equipment, but it is adjacent to the Unit 2 Auxiliary Building which does contain safety-related equipment. In order to mitigate impact to the safety-related equipment in the Unit 2 Auxiliary Building, a flood barrier is installed at Door 381, which connects the Unit 2 Auxiliary Building and Auxiliary Building Extension below elevation 361'.

In 2014 deficient conditions that were observed in the flood protection features were either promptly repaired or addressed with compensatory measures. Repairs included installing or replacing flood seals and isolating abandoned-in-place equipment. The compensatory measures included fabricating and properly staging temporary flood barriers and staging seal material to be installed in the event of extemal flooding.

7.4 Flood Protection Features Not Inspected Flood protection features that were determined to be inaccessible could not be visually inspected. These features included wall areas behind installed equipment and rooms with high dose rates as determined by Radiation Protection (RP).

Inaccessible features were evaluated by document reviews and/or by comparison with the material condition of surrounding or similar features. These evaluations established reasonable assurance that the inaccessible features can perform their design basis function during an external flood.

During the 2012 walkdowns, a number of features were considered restricted access and were unavailable for inspection. These features were documented in the site CAP in 2012 and were inspected at later date (Ref. 10.8), as shown in Table 2 below:

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1 Page 18 of 20 Table 2: 2012 Summary - Restricted Access Features Unable to be Inspected Unit 2 Restricted Access Listing Restricted Access Area & Reason Means to Address Features Unit 2 Aux Building Room 2009 No readily available means Walkdown performed on (elevator Shaft) EL 317 - Required to of egress. Entry requires September 12, 2013 verify Walls and Penetrations coordinated efforts with safety, radiation protection and electrical craft.

Unit 2 Aux Building Room 2001 & Locked High Radiation Walkdown performed on 2002 El 317 - Required to verify Areas September 23, 2013 Walls and Penetrations Penetrations - 2019-03-0007, 0008, Junction boxes are to be Walkdown performed on 0009, 0010 (Located on Turbine opened and are above floor September 26, 2013 Building wall - El 352' above the 335 level 16-18 feet. Craft was deck) Room 2019 - Need to evaluate unable to open within the conduit internal seals time frame of the walkdowns. Scaffolding is required to complete inspections.

Unit 2 Aux Building Tank Vaults Restricted hatch access Walkdown performed on Rooms 2020A, 2020B, 2020C, and High Radiation Area. September 5, 2013 2020D El 335 - Required to verify This requires coordination Walls and Penetrations with safety, radiation protection and mechanical craft.

Unit 2 Aux Building Pens 2279-0021 Craft was unable to open Walkdown performed on and 0022 EL 354 - Junction Boxes within the time frame of the September 26, 2013 are to be opened to look at internal walkdowns conduit seals Unit 2 Aux Building EL 335' Room Observation of these Walkdown performed on 2055 - Penetration #'s 2055-07-, penetrations was impeded September 25, 2013 0303 and 0304. by ability to gain viewpoint due to contaminated equipment interferences.

Penetrations require scaffolding to inspect.

Unit 2 Manhole 2MH03 (Yard) - Craft was unable to open Walkdown performed on Required to verify conduit internal within the time frame of the September 26, 2013 seals walkdowns. Inspections will requires safety coordination due to 4160 V cable runs.

¢CALC-AN02-CS-1 2-00002 ENRO te Y REV. 1 L-'; I Page 19 of 20 8.0 AVAILABLE PHYSICAL MARGIN As indicated in NEI 12-07, Section 3.12 (Ref. 10.3), the NRC is no longer expecting the Recommendation 2.3: Flooding Walkdowns to include an evaluation of the cliff-edge effects at the site. The APM has been determined and documented on the walkdown record forms (Ref. 10.10). The APMs provided on the walkdown record forms will allow flood hazard reevaluations to be completed in response to the NRC's Recommendation 2.1: Flooding.

No APMs documented in the walkdown record forms were considered to be "small".

9.0 NEW FLOOD PROTECTION SYSTEMS In 2013, the procedure for natural emergencies was revised to require the installation of a temporary barrier at Door 381 during a flooding event to isolate the ANO Unit 2 Auxiliary Building from the Unit Auxiliary Building Extension.

10.0 REFERENCES

10.1. NRC Letter to Licensees, dated March 12, 2012, "Request for Information Pursuant to Title10 of the Code of Federal Regulations 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3 of the Near Term Task Force Review of Insights from the Fukushima Dai-ichi Accident" 10.2. NRC Letter, dated December 23, 2013, Request for Additional Information Associated with Near-Term Task Force Recommendation 2.3, Flooding Walkdowns; Accession No. ML13325A891 10.3. NEI 12-07, Rev. 0-A, "Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features" 10.4. EN-DC-1 70, Rev. 000, "Fukushima Near Term Task Force Recommendation 2.3 Flooding Walkdown Procedure" 10.5. SAR-U2, "Unit 2 Safety Analysis Report", SAR Amendment 25 10.6. TS-U2, Rev. 296-B53, "Technical Specifications (Unit 2)"

10.7. OCAN 111302, dated November 26, 2012, "Supplemental Response to NRC Request for Information Pursuant to 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 Dai-ichi Accident" 10.8. 2CAN 111202, dated November 27, 2012, "Flooding Walkdown Report - Entergy's Response to NRC Request for Information (RFI) Pursuant to 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 Dai-ichi Accident", Arkansas Nuclear One - Unit 2, Docket No. 50-368, License No. NPF-6 10.9. OCAN01 1404, dated January 31, 2014, "Update to Response to NRC 10 CFR 50.54(f) Request for Information Regarding Near-Term Task Force (NTTF)

is CALC-AN02-CS-1 2-00002 0 ENERCON Entezga REV. 1 EW "o'i"°*'fvr'i.

oceienc"ý- Vvy Page 20 of 20 Recommendation 2.3, Flooding - Review of Available Physical Margin (APM)

Assessments", Arkansas Nuclear One - Units 1 and 2, Docket Nos. 50-313 and 50-368, License Nos. DPR-51 and NPF-6 10.10. OCAN041410, dated April 30, 2014, "Revised Response to NRC 10 CFR 50.54(f)

Request for Information Regarding Near-Term Task Force (NTTF)

Recommendation 2.3, Flooding", Arkansas Nuclear One - Units 1 and 2, Docket Nos. 50-313 and 50-368, License Nos. DPR-51 and NPF-6 11.0 ATTACHMENTS None