ML17363A083

Duane Arnold Energy Center, Flooding Walkdown Report, NEE006-PR-001, Revision 0

ML17363A083
Person / Time
Site:	Duane Arnold
Issue date:	11/14/2012
From:	Kleinfeldt B NextEra Energy Duane Arnold
To:	Office of Nuclear Reactor Regulation
Shared Package
ML17363A067	List: ML17363A069 ML17363A071 ML17363A072 ML17363A074 ML17363A075 ML17363A076 ML17363A078 ML17363A079 ML17363A082 ML17363A083 ML17363A085 ML17363A086 ML17363A088 ML17363A098 NG-17-0235, Attachment 1: Duane Arnold Energy Center, License Amendment Request TSCR-166, Redline Markup of NEI 99-01, Revision 6. Part 1 of 2 NG-17-0235, Attachment 1: Duane Arnold Energy Center, License Amendment Request TSCR-166, Redline Markup of NEI 99-01, Revision 6. Part 2 of 2 NG-17-0235, Attachment 2: Duane Arnold Energy Center, License Amendment Request TSCR-166, Clean Copy of the Proposed DAEC EAL Scheme NG-17-0235, Duane Arnold Energy Center - Calc No. NEE-323-CALC-003, Documentation of the RU1 Emergency Action Levels NG-17-0235, Duane Arnold Energy Center EAL Classification Matrix Hot Conditions (Modes 1, 2, 3) NG-17-0235, Duane Arnold Energy Center, Calc No. NEE-323-CALC-001, Primary Containment Radiation EAL Threshold Determination NG-17-0235, Duane Arnold Energy Center, Calc No. NEE-323-CALC-002, Dose Rate Evaluation of Reactor Vessel Water Levels During Refueling for EAL Thresholds NG-17-0235, Duane Arnold Energy Center, Calc No. NEE-323-CALC-004, Revised Liquid Radiological EALs Per NEI 99-01 NG-17-0235, Duane Arnold Energy Center, Calc No. NEE-323-CALC-005, Revised Gaseous Radiological EALs Per NEI 99-01 Rev. 06 NG-17-0235, Duane Arnold Energy Center, Calc No. NEE-323-CALC-005, Revised Gaseous Radiological EALs Per NEI 99-01 Rev. 6 NG-17-0235, Duane Arnold Energy Center, Calc No. NEE-323-CALC-006, Correlation of Drywell Radiation Monitors for 300 Uci/Gm Dose Equivalent Iodine NG-17-0235, Duane Arnold Energy Center, License Amendment Request TSCR-166, Adoption of Emergency Action Level Scheme Pursuant to NEI 99-01, Revision 6, Development of Emergency Action Levels for Non-Passive Reactors. NG-17-0235, EAL Classification Matrix Cold Conditions (Modes 4,5, and Defueled)
References
NG-12-0461, NG-17-0235 NEE006-PR-001, Rev 0
Download: ML17363A083 (21)

Text

Enclosure to NG-12-0461 FLOODING W ALKDOWN 1tIBPORT NEE006-PR-001, Revision 0 IN RESPONSE TO THE 50.54(£) INFORMATION REQUEST REGARDING NEAR-TERM TASK FORCE RECOMMENDATION 2.3: FLOODING for the Duane Arnold Energy Center 20 Pages to Follow Preparer:

Reviewer:

Approver:

.FLOODING WALKDOWN JREPORT NEE006-PR-001, Revision 0 IN RESPONSE TO THJE 50.54(f) INFORMATION REQUEST REGARDING NEAR-TERM TASK FORCE RECOMMENDATION 2.3: FLOODING for the Duane Arnold Energy Center 3277 DAEC Road, Palo, IA 52324 Facility _Operating License No. DPR-49 NRC Docket No. 50-331 NeX:tEra Energy ~esources 700 Universe Boulevard Juno Beach, FL 33408 Prepa*re.d by: Enercon Services, Inc. 2056 Westings Avenue Suite 140 Naperville, IL 60563 Noveinber 14, 2012 Printed Name/Title Brian Kleinfeldt/

Engineer Majid Esfahani/

Sr. Engineer Joseph Bendel/ Project Manager Affiliation ENERCON ENERCON ENERCON Site Acceptance:

• li.._,.;fk Ll-tog-/p~.,4+ " t NTTF Recomniendation 2.3 (Walkdowns):

Flooding NextEra Energy Res0t1rces Duane Arnold Energy Center November 14, 2012 NEE006-PR-00 I, Revision 0 Contents I. EXECUTIVE

SUMMARY

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............................................... 2 2. PURPOSE ........ ,., ........... .-........ ; ........................

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4 a. Background

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...... 4 b. Site Description

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4 3. METHODOLOGY

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4 4 .. REQUESTED INFORMATION

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4 a. Reque~ted Information Item 2(a) -De s ign Basis Flood Hazards., .....................................

.... : .............. 5 b , Requ~sted Information Item 2(b) -CLB Protection and Mitigatio*n features ...... '.;, .................

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... 6 C. Requested Information Item 2(c)-Flood Warning Systems ............

..................................................... 8 d. R e quested Information Item 2(d)-Flood Prot~ction System/Barrier Effectiveness

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8 e. Requested Information liem 2(e)-Implementation of Walk.down Process .......................

................. 11 f. Requested Information Item 2(f) -Findings and Corrective Actions Taken/Planned

......................... 12 g. Requested lnforination Item 2(g) -Cliff -Edge Effects and Available: Physical Margin ................... 13 h. Requested Information Item 2(h)-Planned/Newly-Installed Flood Protection Enhancements

......... 14 5. CONCLUSIONS

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14 6. REFERENCJ:;S

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.. ... , ........................... , ............. , .....*...... .-........ 16 7. ATTACHMENTS

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17 Piige I of 19 NTTF Recommendation 2.3 (WalkdO\vns):

Flooding NextEra Energy Resources Duane Arnoid Energy Center November i 4, 20 l2 NEE006-PR-OO I, Revision 0 i. EXECUTIVE

$.UIYŽN.lY This report was developed to provide information requested by the United States Nuclear Regulatory Commission (NRC) pursuant to Title )0 of the Code of Federal Regul<1tions, Section 50.54 (f) on Marcb 12, 2012 for the Duane Arnold Energy Center {DAEC). In response to *the NRC request, Duane Arnold LLC 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 permanent structures, systems, components (SSCs), portable flood mitigation

• equipment, and the procedures needed to install and or operate the1n during : a flood are acceptable and c*apable of performing their design function as credited in the CLB. Walkdowns were performed in accordance with Nuclear Energy Institute (NE!) 12-07 (Rev. O~A), "Guidelines for Perfoi*111ing Verific.ation of Plant Flood Protection Features," dated May 2012 [Ref. l ). This docu1iient ,vas endorsed by the NRC on May 31, 2012. Dl.ia1,e Arno.lei Energy Center plant coilfigura\ions and procedures were compared to the flood protection features credited in the CLB documents for external flooding events. Site specific features credited for protection and mitigation against external flooding events were identified and ev~luated.

A st:nnmary ofthe DAEC CLB, flood prott:ction features and the results of the inspections are provided belO\v. Current Licensing Basis

• The probable 1.na?(imum flood (PMF) for DAEC is 764.1 fe~t and is c.aused by prolonged rainfall over the Cedar River drainage basin. The site is Jirotecte<;J to 767 feet. to accormt for ~vave action and freeboard. Additional protection is provided at openings to safety related buildings up to 773.7 feet on the southerly side, 770.5 feet on the northerly side and 769 feet on the easterly and westerly sides per NRC requirements.

T_here exists a 6.4 clay time period between the beginning ofthe PMF _storm and the PMF per the CLB [Ref. 3]. Flood Protection Features

• The iicensing basis for DAEC specifies that approx.imately 6.4 days exist from the beginning of the PMF storm to tl1e : rMF. The flood will remain above grade for approximately j days during th~ design basis flood. The DAEC CLB does not state specific plant nicides (shutdown, refuel, startup, online) during a flood event. As a result, walkdowns took into consideration all modes of operation.

DAEC employs incorporated active and_ passive and temporary active and passive flood protection features to meet the CLB flood requirements. Temporary feat.ures include stoplogs augmenteQ with plastic sheeting and sanobags, stimp pmi1ps, sealing of hatches (welding/caulking), instaliing extensions for the diesel generator exhaust and installing a cover for the auxiliary boiler loi1ver. Incorporated features include the sump system, walls, floors, roofs, penetration seals, water stops and 111emb.ranes and a watertight door. Temporary featpres and incorporated acJivc feat~res are installed and/or implemented per the station flood protection procedure.

This pro~edure

• is implemented upon receipt of a flood advisory from the National Weather Service. Inspection Results

• Credited flood protection features in the CLB were inspected against the acceptance criteria found in the NEI 12-07 guidance [Ref. l ]. Reasonable assurance that the inac*cessib\e features can perf9n11 their CLB intended flood protection function are provided in this report. A tabletop simulation of the station flood protection procedure was also conducted.

It was confirmed that required actions can be completed in the credited time and this procedure is effective, however some enhancen1eilts to this procedure were also identified in order to streamline its implementation.

Reasonable simulations Page 2 <;>f i9 NTTF Recommendation 2.3 (W alkdow n s): Flooding NextEra Energy Resources Duane Arnold Energy Center November 14, 2012 NEE006-PR-OO I, Revision 0 were conducted on the temporary features/actions representative of the different types of flood protection features at DAEC to validate execution times and ensure features meet their CLB intended function. With the exception to item s listed below, all features were found to meet their CLB intended function without corrective action.

• The following describe s th e results of the walkdowns that identified degraded, non-conforming or unanalyzed conditions:

o The in s tallation of the steel stoplog for Door 805 was found to have fit up issues as plant personnel were not able to install the barrier per the design configuration.

A functional assessment with int e rim actions was implemented, with permanent corrective ac tions initiated and incorporated into the Corrective Action Process as compensatory action for this finding.

• o Two louv ers on the Intak e Structure westerly wall were found to extend below the specified flood protection height of 769 feet. A function a l assessment with interim actions was implemented, with permanent corrective actions initiated*

and incorporated into the Corrective Action Process as compensatory action for this finding.

• There were no features identified as restricted access during the walkdowns.

• The following describes features that were identified as inaccessible:

o Floor drains in the air plenums near louvers above the diesel generators were identified as inaccessible.

Reasonable 13ssurance that this feature will function as designed is based on visual inspection of the drain pipes below the plenum and the ~bsence of any signs of ingress. The louver in the plenum is also above the CLB wave and freeboard height of 773.7 feet. o Embedded water stops ai1d waterproof membranes were identified as inaccessible. Reasonable assurance that this feature will function as designed is based on visual inspe ction of joints between concrete s lab s, gaps between buildings and all penetrations for signs of ingress from ground water. Overall, DAEC employs a number of different flooding protection featur es credited in the CLB that are available, functional and properly maintained respective to th ei r CLB intended flood protection functions. The Duane Arnold Energy Center i s found to be in compliance with its flood protection requirements per the current site licensing basis based on the inspections of the NEI 12-07 walkdowns and corrective actions implemented as a result of the walkdowns.

Pag e 3 of 19 NTTF Recommendation 2.3 (Walkdowns):

Flooding NextEra Energy Resources Duane Arnold Energy Center November 14, 2012 NEE006-PR-OOJ, Revision 0 2. PURPOSE a*. Background In response to the nuclear fuel damage at the Fukushima-Dai-ichi power plant due to the March 11 , 2011 earthquake and subsequent t s unami , the United States Nuclear Regulatory Commission (NRC) established the Near Term Task Force (NTTF) to conduct a systematic review ofNRC processes and regulations, and to make recommendations to the Commission for its policy direction. The NTTF reported a set of recommendations that were int e nded to clarify and strengthen the regulatory framework for protection against natural phenomena.

• On March 12, 20 12 , the NRC issued an information request pursu a nt to Title 10. of the Code of Federal Regulations , Section 50.54 (t) (10 CFR 50.54(t) or 50.54(t))

[Ref. 2]. In Enclosure 4 of this document, the NRC requested that lic ensees 'perform flood protection walkdowns to identify and address plant-specific degraded, nonconforming , or unanalyzed conditions and cliff-e dge effects (through the corrective action program) and verify th e adequacy of monitoring and maintenance procedures. The flooding walkdowhs have been completed and the results are described in this report. b. Site Description The DAEC is located on the west bank of the Cedar River, approximately 8 miles northwest of Cedar Rapids, IA and 133.5 miles above its confluence with the Iowa River. Finished grade at the site is 757.0 feet with the natural grade varying near 750 feet. The grade slopes downward to the Cedar River with the intake structure at 754 feet. Based on historical Cedar River water levels, the average river level falls in the range of 731 feet to 737 feet. The Cedar River flooding is the bounding case for external flooding at DAEC. Periodic floods have occurred at the site with the lar gest to date occurring in June 2008 reaching a peak stage of 751 feet. The 2008 flood was classified as a 500-yr flood by the United States Geological Survey (USGS). 3. METHODOLOGY The walkdowns were performed in accordance with NEI 12-07 (Rev. 0-A), "Guide line s for Performing Verification of Plant Flood Protection Features", dated May, 2012 [Ref. 1]. This document was endorsed by the NRC on May 31 , 2012 [Ref. 6]. 4. REQUESTED INFORMATION The information request ed in Reference 2, Enclosure 4, under paragraph 2 of the 'Re quested Information

' section, is provided below. The contents of each item were developed in accordance with Reference 1, Appendix D. On Jun e 8, 2012, the Duan e Arnold Energy Center submitted its 90 Day Response.Letter to the NRC Request for Information Pursuant to the 10 CFR 50.54(f) Jetter confirming its use of the NRC endorsed NEI 12-07 document as a basis for the plant flood protection features walkdowns.

Page 4 of 19 NTTF Recommendation 2.3 (Walkdowns):

Flooding NextEra Energy Resources Duane Arnold Energy Center November 14, 2012 NEE006-PR-001, Revision 0 a. Requested Information Item 2(a) -Design Basis Flood Ha~'.ards Describe the design basis flood ha z ard level(s) for all flood-causing mechanisms.

including groundwater ingress. The DAEC site flooding analy s is is based on field r e connaissance and mapping, collection and analysis of

• flood di s charge data from the USGS, a flood hydrograph analysis of previous floods on the Cedar River, rainfall lo s ses and retention rates and an application of the maximum probable storm documented in Appendi x H of the DAEC Preliminary Safety Analysis Report (PSAR) [Ref. 4]. This results in a probable ma x imum flood of *764.1 f e et mean sea fovel (msl) which corresponds to c1 flow rate of 316,000 cfs on the Cedar River. This flood is most likely to occur in spring or early summer based on previous flood history. In addition to the storm g e n e rated flood, wind generated waves and freeboard are taken into account. A wav e height of 2.8 feet is added to the PMF as a result of sustained wind of 45 mph over a 1.5 mile stretc lii resulting in the site being designed to protect against floods of 767 feet. Per additional request by the Atomic Energy Commission, additional flood protection is provided for the openings of safety related buildings up to 773.7 feet on the southerly sid e , 770.5 feet on the northerly side and 769 feet on the easterly and westerly sides using stoplogs augmented with plastic sheeting and sandbags.

Due to the gentle topography existing in the river valley, a landslide could not occur at a magnitude that would result in a water level at the site that would approach the PMF [Ref. 3). The probable maximum precipitation storm will not cause the failure of any safety related structures or equipment either because of local flooding or failure of roof structures and their appurtenances. In the event of rains as severe as those that could cause a local probable maximum flood , some local flooding could occur because of the fact that the site storm drainage system is designed to accommodate the runoff from a I 0-yr . storm, but this flooding will have no adverse effect on any safety-related structures or equipment.

A review of the DAEC Updated Final Safely Analysis Report (UFSAR) has shown that all safety-related structures are capable of supporting a water accumulation on their roofs to the depth of the parapet without failure. Above this depth, the water will spill over the parapet and down the side of the building.

All roof penetrations on all plant safety-related structures extend above the roof to a height greater than the height of the parapet, thus precluding any flooding of the interior of any building from excessive precipitation.

Therefore, it may be concluded that the probable maximum precipitation storm will not cause the failure of any safety-related structures or equipment

[Ref. 3]. Review of the site topography shows that the safety related structures are located at a higher elevation than most of the owner controlled area with the topography s*loping down toward the river to the east. Local intense precipitation described above could cause local flooding, but it would not affect safety related structures due to the site topography.

Dam failure has been screened out of the flooding hazards since the 12 low head upstream dams are submerged during the PMF. Ice effects have been screened out since the local topography does not lend itself to creating a flood wave approaching the PMF. Surges, seiches and tsunamis have been screened out as not applicable to DAEC per the UFSAR section 2.4 [Ref. 3]. Ground water ingress is not specifically mentioned in the CLB, but per the flood protection requirements of the UFSAR, walls of protected buildings are coated with a waterproofing material below grade. In addition . to this, the joints between concrete slabs and structures were provided with bulb and dumbbell waler stops*. NEI FAQ-007 [Ref. 8] also justifies the basis for inspecting building walls against the acceptance criteria if the buildings are to be maintained in a dry condition. Page5of19 NTTF Recommendation 2.3 (Walkdowns):

Flooding NextEra Energy Resources Duane Arnold Energy Center November 14, 2012 NEE006-PR-OOI, Revision 0 b. Requested Information Item 2(b) -CLB Protection and Mitigation Features Describe protection and mitigation features that are considered in the licensing basis evaluation to protect against externa l ingress of water into SSCs important to safety.

• The DAEC flooding licen s ing basis includes protecting the plant from flood waters up to 767 feet. Upon further revi ew of wave actions additional s pecifications are defined to protect the openings of safety related buildings up to 773.7 feet on the southerly side, 770.5 feel on the northerly side and 769 feet on the easte rly and wester ly si des using sloplogs augmented with plastic sheeting and sandbags.

The maximum river l e vel is reached 6.4 days after the beginning of the storm causing the PMF. The CLB does not de scr ibe any specific plant configuration during the flood; however, the l ead time of 6.4 days b e twe en the PMF s torm and ensuing PMF is large enough to allow for flood mitigating mea sures to be completed as outlined in the site nood protection procedure in all plant configurations.

• The li ce nsing basis for DAEC specifies th a t approximately 6.4 days exist from the beginning of the PMF storm to the PMF. The flood will remain above grade for approximately 3 days after the peak discharge is reached [Ref. 9).

• The DAEC CLB ident ifi es actions taken in response to rising flood waters and describes temporary and incorporated, active and passive flood protection features.

The flood protection procedure is entered when the national weather service issues a flood advisory.

This procedure has follow up actions corresponding to various river water level heights which are coordinated by th e control room supervisor.

This procedure is a reference use procedure with no automatic act ions. This procedure calls for the installa tion and implementation of both active and pas sive temporary and incorporated flooding protection features. Temporary active features:

• Temporary sump pumps are placed in sump pits and catch basins behind specified exterior doors in the plant to control in-l eakage per the station nood protection procedure.

Temporary passive features:

• Stoplogs are provided for entry doors to the plant flood proi:ected areas to resist CLB flood waters.

• Sandbags and plastic sheet ing are u se d to augment the stop logs. Sandbags are also used to create catch basins on the interior side of flood protection doors/stoplogs to control leakage.

• Ex tension s are we lded to the exhaust ports for the two standby diesel generators to raise th e height of the exhaust ports to the CLB flood l evel in cluding specified wave and run-up.

• A s teel cover is bolted and caulked over the auxiliary boiler louver since the low est point of the louv er is below the CLB flood height including specified wave and run-up heights.

• Bracing is installed in the seism i c gaps at entry ways between seismically qualified buildings.

This is to prevent any ingress sho uld the embedded waler stops and sealing material between the buildings fail.

• Hatch covers in the pump hou se to the Emergency Service Water (ESW) and Residual Heat Removal (RHR) pits are welded, sealed and braced shut. Hatch covers to (High Pressure Coolant Injection (HPCI) and Reactor Core Isolation Cooling (RCIC) are also sealed shut. Page 6 of 19 NTTF Recommendation 2.3 (Walkdowns):

Flooding NextEra Energy Resources Duane Arnold Energy Center November 14 , 2012 NEE006-PR-OOI*, Revision 0 Incorporated active features:

• Sump pumps are credited for pumping out water from sump pits resulting from seepage of flood protection features.

• A watertight door is pr esen t in the pump house to protect the ESW and RHR pumps. Incorporated passive features:

• Floor drains and s ump s are credited to provide flow paths for seepage from penetration seals and doors/stoplogs.

• Building walls, floors, roofs and associated penetrations are credited to resist the effects of th e CLB flood including hydrostatic pressure and uplift. All penetrations below the flood height , including below grade are sealed against water ingr e ss. All roof penetrations on all plant safety related structures extend above the roof to a height greater than the height of the parapet, thus precludin g any flooding of the interior of these structures.

• Bulb typ e water-stops and waterproofing membrane s are embedded in the concrete slabs at joints to prevent ingress between wall panels and the seismic gaps between buildings.

Waterproof membr a nes are applied on the exterior of all below grade concrete walls for credited buildings. The UFSAR credits that all flood mitigating actions can be completed in the required time .of 6.4 days, which is the time from the beginning of the PMF storm to the PMF level. Seismic Category I structures are credited as being able to withstand the effects of the CLB flood including the effects of hydrostatic loading and uplift. The following buildings were reviewed in the UFSAR for the PMF of767 feet: o Reactor Building including the HPCI Structure o Turbine Building o Intake Structure o Control Building o Radwaste Building o Pump House o Recombiner Room o Low Level Radwaste Processing and Storage Facility (LLRPSF)-Storage Portion Safety buildings are provided with additional prote.ction at building openings to CLB heights as stated in section 4a. The Intake Structure is not maintained in a dry condition as the other buildings mentioned above. Seismic Category I equipment in the intake structure is located above the peak stage of the flood at elevation 767 feet. Below* this elevation the structure is allowed to flood resulting in no uplift and above this elevation the walls prevent ingress from waves and run-up.

• The flood protection procedure is a reference use procedure with no automatic actions that is coordinated by the control room supervisor (CRS). This procedure is entered upon receiving a flash flood advisory from the national *weather service. Per the technical requirements manual, if the river level reaches 7)'3 feet the river level must be monitored and if the river reaches 757 feet the unit must be in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Mode 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. Page 7 of 19 NTTF Recommendation 2.3 (Walkdowns):

Flooding NextEra Energy Resources Duane Arnold Energy Center November 14, 2012 N EE006-PR-OO I, Revision 0

• The licensing basis does not s tate any weather conditions present during its description of flood mitigating featur es. Reasonable simulations completed as a part of this effort considered adverse weather conditions likely to occur with the PMF causing m ec hanisms, i.e. wind, rain, mud , ~tc. c. Requested Information Item 2(c) -Flood Warning Systems Describe any warning systems to det ec t the presence of water in rooms important lo sa fety.

• There are no credited room water level warning systems for external flooding at DAEC. The flood mitigation strategy is to keep all areas important to safety in a dry condition through the use of temporary and incorporated flood protection features.

There are room water level indicators in the HPCJ, RCIC, "A" RHR, "B" RHR and TORUS areas for int erna l flooding. These provide defense in depth and a secondary notification ofa flood condition at the site if the external flood barriers should fail. d. Requested Information Item 2(d) -Flood Protection System/Barrier Effectiveness Discuss the effectiveness of flood 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 I .h [in Enclosure 4 of the March 12, 2012. 50.54{D letter] Visual inspections of the external flood protection features identified in the CLB were performed with the objective of comparing the observed condition of the feature to the acceptance criteria as defined in Section 6 of NEI 12-07. This approach provided the basis for assessing the feature's ability to perform its intended external flood protection function and identifying conditions warranting entry into the corrective action program. Observations entered into the corrective action program and dispositioned as deficient are discussed later in this report. With the exception of features entered into the corrective action program which were determined to be deficient as discussed later in this report, the walkdowns found that the flood protection features meet the acceptance criteria.

Topographic observations found no new features adverse to site drainage during a PMF. Credited walls and floors and their associated penetrations were visually inspected per the acceptance criteria up to the CLB flood and wave height. Conduit penetra tio n seals were visually inspected. Concrete structures were inspected for signs of material degradation and penetration seals were inspected for evidence of seal failure per the acceptance criteria. The DAEC Structures Monitoring program also provides periodic inspection of these features. Credited floor drains and sumps to control seepage from penetrations and doors/stoplogs were inspected to the acceptance criteria to make sure no adverse conditions were present and the flow paths were clear. Credited sump pumps were included in visual inspections per the acceptance criteria and preventative maintenance activities and procedures were reviewed for adequacy. Credited doors were inspected per the acceptance criteria to ensure inst a llation points (stoplog frames, anchor bolts) for stoplogs were functional.

The watertight door in the Pump House was opened and inspected for satisfactory condition of the sealing material and latches. The roofs of safety related structures are credited as being able to withstand the loading effects of a storm that could cause a local probable maximum flood. Annual roof inspections are conducted to identify and repair any conditions that do not meet the work order inspection criteria.

The inspection did not find any Page8of 19 NTTF Recommendation 2.3 (Walkdowns):

Flooding NextEra Energy Resources Duane Arnold Energy Center November 14, 2012 NEE006-PR-OO I, Revision 0 degradation or deterioration of roofs and roof drains per the acceptance criteria used in the yearly inspection.

The acceptance criteria used by these work orders were reviewed for alignment with the NE! 12-07 acceptance criteria and were found to meet and exceed the criteria used by the NEI 12-07. The inspections were conducted during the months of August and September of 2012 and the results were reviewed by walkdown personnel and found to be acceptable.

These work orders are attached to the record forms for the credited roof structures.

Temporary features described in section 4b were inspected in the areas where they are staged per the acceptance criteria. This inspection was further augmented by reasonable simulations.

Reasonable simulations were performed to demonstrate that credited procedures/actions are feasible and can be completed effectively in the credited time. The reasonable simulations were conducted as a part of the walkdowns to verify execution times and identify any hindrances in installation of the features.

Simulations performed align with their estimated times , provided in the flood protection procedure, with the exception of Door 805 described below. Simulations:

• Door 154 This is a personnel door on the north side of the turbine building.

This door includes the installation of wooden stoplogs augmented with plastic sheeting and sandbags.

Workers retrieved and installed stoplogs and installed this barrier per station drawings with no observed difficulties.

Based on the simulatio_n, the completion time of this type of feature is 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> with 3 craft personnel.

• Door 805 This is an equipment/loading door in the Low Level Radwasle Processing and Storage Facility (LLRPSF) that includes the installation of one steel stoplog over the door frame. Workers retrieved and attempted to install this feature per station calculations. Difficulties in installation were encountered as workers were not able to install the door per its design configuration.

A functionality assessment and compensatory actions were implemented for the installation.

This is further discussed later. Due to the alternate configuration requiring welding, an additional 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> is added to the installation of this feature for the purpose of verifying the feature can be installed within the available time.

• Auxiliary Boiler Louver Cover This cover is designed to seal the auxiliary boiler louver during the CLB flood. Workers retrieved and demonstrated the ability to install this feature. The cover was rigged and lifted against a wall of similar design to that of lhe louver. All necessary tools and equipment were brought to the demonstration area to show that the feature could be properly installed.

Simulation per station drawings was performed with no observed difficulties.

• Standby Diesel Generator Exhaust Extension Two L-shaped diesel exhaust extensions are welded to the exhaust ports of the SBDOs to extend the exhausl port height lo the CLB level of 773. 7 feet for waves and freeboard on the south side of the turbine building. This simulation demonstrated the ability to retrieve and rig the extension for lifting. All necessary tools and equipment to weld the extension to the existing exhaust port were brought to the demonstration area to show that the feature could be properly installed.

Some enhancements to this feature were identified and are documented later in this report, but this feature is fully capable of being installed in its current state. Page 9 of 19 NTTF Recommendation 2.3 (Walkdowns):

Flooding NextEra Energy Resources Duane Arnold Energy Cente r November 14, 2012 NEE006-PR-001 , Revision 0

• LLRPSF Temporary Sump Pumps Temporary sump pumps powered by essential power are utilized in th e flood protected building s to suppl e ment the incorporated sump pump system and m a nage s e epa ge a t doors/stoplogs

The simulation for t~e LLRPSF included verifying all necessary m a terials to implement the pump arrangement were available on site. This was completed by walking down the LLRPSF and measuring required amounts of cable and ho s e and validating the required amounts were available.

Interviews of maintenance personnel were also conducted to valida t e comp le t i on time for preparing , staging and la y ing down these required materials. A tabletop simulation of the flood protection procedure was conducted with op e rations, .maintenance and systems engineering to verify execution times and identify hindrances tci the procedur e's execution. This simulation determined that the estimated time to complete all required flood mitigating actions is 3.67 days, which meets the 6.4 day requirement in the UFSAR. The walkdown records contain the specific times and dependent and parallel actions to determine this number. Overall , DAEC employs a number of different flooding protection features that are a vailable, func t ional and implementable respective to their credited flood protection functions with consideration taken to the items discussed later in this report and their resulting compensatory actions. The DAEC also employs the following structures, systems, components and procedures that aid in flood mitigation on site, but are not credited in the CLB for external flood mitigation.

• A step in flood protection procedure initiates the implementation of a temporary diesel generator* to the intake structure and the River Water Supply (R WS} system. Since this temporary diesel generator does not meet safety related power supply requirements it is no t credited a s a flood protection feature in the CLB. However, in the case of a loss of power to the intake structure, this generator can provide temporary power ifno further design basis accidents occur that would result in the fa i lure of the non safety qualified generator.

• Water level indication systems for the HPCJ, RCIC, "A" RHR, " B" RHR and TORUS areas are installed for internal flooding detection. These provide defense in depth and a secondary notification of a flood condition at the site if the external flood barriers should fail.

• DAEC employs a Structures Monitoring program [Ref. 5] that adheres lo 10 CFR 50.65. Per Attachment I o f this document, the inspection criteria include an inspection of cracks in concrete walls and identification of any external water ingress. This program also includes inspections of stoplogs and elastomer sealing materials on walls and roofs. These periodic inspections aid in detection of any adverse conditions in these flood protection features.

• The site drainage system is designed to withstand a IO year s t orm , which does not cause the PMF , and includes storm drains and drainage ditches throughout the site. In addit i on to this , a number of security ditches were observed on topographic walkdowns that could aid in managing runoff water during local intense precipitation events. Page 10 of 19 NTTF Recommendation 2.3 (Walkdowns)

Flooding NextEra Energy Resources Duane Arnold Energy Center November 14, 2012 NEE006-PR-OO 1, Revision 0 *e. Requested Information Item 2(e)-Implementation of Wa l lkdown Process Present information related to the implementation of the walkdown process (e.g., details of selection of the walkdown team and procedures) using the documentation template discuss ,~d in Requested Jnfonnation Item 1.j (in Enclosure 4 of the March 12, 2012, 50.54{f) letter], including actions taken in* response to the pee r review. On June 8 , 2012, the Duane Arnold Energy Center submitted its 90 Day Response Letter to the NRC Request for Information Pursuant to the 10 CFR 50.54(f) letter confirming its use of the NRC endorsed NEI 12-07 document as a basis for the plant flood protection features walkdowns. Consistent with Section 5.3 ofNEI 12-07, walkdown teams consisted ofat least two trained individuals with a complementary set of skills. The walkdown team consisted of two ENERCON engineers with backgrounds in nuclear, electrical, mechanical and materials science engineering. Both engineers hold Master's of Science degrees in the above fields and have previous experience with plant modifications and walkdowns.

Per Section 5.3 of NE! 12-07, personnel selected to perform walkdown inspection activities were experienced and knowledgeable of the site current licensing basis. Personnel were experienced or trained to perform visual inspections SSCs and met the knowledge requirements of Appendix C of NEI 12-07. All team members that performed the visual inspections were trained to and knowledgeable of the below information:

• NANTEL lesson on Generic Flood Protection Walkdowns

• Duane Arnold Energy Center Combined Licensing Basis

• NITF recommendation 2.3-Flooding and the NRC letter dated March 12, 2012

• NEI 12-07, Revision 0-A ENERCON personnel were supported by site and craft personnel during the walkdown who were not required to meet the above requirements.

These personnel were used because of their familiarity with plant SSCs and protective measures.

Generally , these personnel met the knowledge requirements but did not undergo the required training. A pre-job brief was performed prior to conducting the walkdowns using plant human performance procedures and was tailored to the walkdown task. Each walkdown performed a specified inspection to assess the capability of the item to perform its required function.

All walkdown results were documented in accordance with the recommendations of Section 7 of NEI 12-07 and using the walkdown record template in Appendix B ofNEI 12-07 [Ref. l ]. Page 11 of 19 NlTF Recommendation 2.3 (Walkdowns):

Flooding NextEra Energy Resources . Duane Arnold Energy Center November 14, 2012 NEE006-PR-OO I, Revision 0 f. Requested Information Item 2(f)-Findings and Corrective Actions Taken/Planned Results of the walkdown including key findings and identified degraded, non-conforming, or unanalyzed conditions. Include a detailed description of the actions taken or planned to address these conditions using the guidance in Regulatory Issues Summary 2005-20. Rev I, Revision to NRC Inspection Manual Part 9900 Technical Guidance, "Operability Conditions Adverse to Quality or Safety," including entering the condition in the corrective action program. The following list of items identifies features identified during NEI 12-07 flooding walkdowns as degraded, non-conforming or un analyzed.

Description of Deficiency The intake structure houses safety related equipment for the River Water Supply (R WS) system. Per the UFSAR , the western wall is required to resist flood waters of 764.1 feet and waves and freeboard of 769 feet. Two louvers on this wall are open to the floor elevation of 767 feet, which is below the required 769 feet for waves and freeboard.

Feature Category Disposition Incorporated or This non-conformance was entered into Exterior Passive the DAEC cor_rect i ve action program. This included a functionality assessment providing guidance within the station flood protection procedure to provide flood protection for the Intake Structure. A procedure change request was completed to incorporate the guidance into the station flood protection procedure for direction on how to protect the Intake Structure in the event of a flood. A permanent solution is being evaluated in the corrective action program. During the reasonable Temporary This non-conformance was entered into the DAEC correct i ve action program. This included a functionality assessment to ensure guidance is in place to allow installation of the stoplog in the event of a flood. A procedure change request was completed to incorporate the guidance into the station flood protection procedure for direction on how to install this feature. The current -estimate for completing the installation of all flood protection features of 3.67 days includes 12 additional hours for installing this feature in this configuration.

A permanent solution is being evaluated in the corrective action program. simulation, the steel Passive stoplog for door 805 was found to have fit up issues. Workers were not able to install the stoplog on the installed bolts around the door frame. Status Being tracked under corrective action program. Procedure change request completed. Being tracked under corrective action program. Procedure change request completed.

Page 12 of 19 NTTF Recommendation 2.3 (Walkdowns):

Flooding NextEra Energy Resources Duane Arnold Energy Center November 14, 2012 NEE006-PR-OO I, Revision 0 There were no items identified as restricted access during the NEI 12-07 flooding walkdowns.

The following list of items identifies features that were classified as inaccessible during the NEI 12-07 flooding walkdowns and provides d i scussion of reasonable assurance that the feature can perform as designed.

Inaccessible Feature Description Turbine Building Louver Platform Floor Drains Water Stops and Membranes Basis for Acceptance In each of the standby diesel generator rooms there is a louver and air plenum platform.

The bottoms of the louvers are located at 773.7 feet and are located on the south wall of the turbine building.

Inside each of the louver plenums are two drains located at 772 feet. Visual inspection was not possible as there is no reasonable means to access this plenum platform.

Reasonable assurance exists that these drains are functioning properly since the drain piping can be seen from below the platform, which confirms the drains are installed.

There are no signs of water ingress from this louver based on visual inspections. Also, the louver openings are above the CLB flood of 764.1 feet and meet the wave and freeboard height of 773.7 feet so water entry to these plenums from flood waters is unlike l y. Water stops are installed in concrete below grade to prevent water ingress. Water stops are installed per design drawings between concrete slabs and between adjacent buildings during construction.

There is no reasonable means to access this feature as it is embedded between concrete slabs. Reasonable assurance that this feature is installed and functioning exists since visual inspections of floors, walls and seismic gaps did not show signs of water ingress at joints between slabs or gaps between buildings.

Waterproof membranes are applie d to concrete structures and penetrations below grade per design specifications

[Ref. 3]. There is no reasonable means to access this feature as it is installed below grade on the exterior side of concrete walls. Reasonable assurance that this feature is installed and functioning exists because there is no evidence of water ingress at joints between slabs. g. Requested Information Item 2(g) -Cliff -Edge Effects and Available Physical Margin In accordance with NE! 12-07, Available Physical Margins have been collected and documented in the Walkdown Record form (NEI 12-07 Appendix B). The guidance provided in NEI F AQ-006 was also followed [Ref. 7). This information will be used in the flood hazard reevaluations performed in response to Item 2.1: Flooding in the 50.54(t) letter [Ref. 2). Page 13 of 19 NlTF Recominendation 2.3 (Walkdowns):

Flooding NextEra Energy Resources Duane Arnold Energy Center November 14, 2012 N EE006-PR-OO I , Revision 0 h. Requested Information Item 2(h) -Planned/Newly-Installed Flood Protection Enhancements Describe any other planned or newly installed flood protection syste1ns or flood mitigatioi1 measures including flood barriers that further enhance the flood protection.

Identify results and any subsequent actions taken in response to the peer review. Throughout the walkdown process, several items were recommended to site procedures io further enhance the efficie(lcy and effectiveness of the implementation of flood protectioi1 features.

These are discussed below:

• Enhance human factors for the station flood protection procedure to streamline its implementation.

• Enhance rigging capability for diesel generator exhaust extensjons by designing arid installing lifting lugs. There were no changes to the walkdown process or methodology as described in Seciion 7. No changes were made to the form used in Appendix B of NEI 12-07. 5. CONCLUSIONS Walkdowns were performed in accordance with NE! 12-07 (Rev. 0-A), "Guidelines for Performing Verification of Plant Flood Protection Features", dated May, 2012 [Ref. I]. This document was endorsed by the* NRC on May 31, 2012. Configuration a.nd procedures were compared to the flood protection features credited in the current licensing basis documents

[Ref. 3] for external flopding events. Site 0 specific featµres credited for protection and mitigation against external flooding events were identified and evaluated.

The results of the inspections are summarized below. Reasonable Simulations The capability to e_xecute credited flood protection procedures within the availabl e time was verified using the reasonable simulation process on five of the temporary features/actions representative of the different types of flood protection features at DAEC. Staffing levels were verified to be adequate , material condition was acceptable, and the flooding protection procedure could be implemented as written for performance of these activities prior to storin arrival. A tabletop simulation of the flood protection proced~tre was also conducted t o validate the activity/procedure can be executed as specified/written.

It was demonstrated that required actions can be completed effectively in the credited time; however, some enhancements to this procedure were also identified in order to streamline the procedure's implementation. Inspection Deficiencies The flooding walkdowns verified that permanent SSCs, po1table flood mitigation equipt'nent, 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 with these exceptions.

• The installation ofihe steel stoplog for Door 805 was found to have fit up issues as plant personnel were not able to install the barrier per the design configuration.

• Two louvers 011 the Intake Structure westerly wall were fomid to t:xtend below the specified flood protection height, including free board, of769 feet. Page 14 of I?

NTTF Recommendation 2.3 (Walkdowns):

Flooding NextEra Energy Resources Duane Arnold Energy Center November 14, 2012 NEE006-PR-OO 1, Revision 0 Corrective Actions The following corrective actions were taken in response to the above ide nt ified deficiencies:

• Functionality assessments and compensatory ac tions or procedure changes for *the se findings have been implemented by DAEC.

• The station flood procedure was llpdated to protect the Intake Structure Louvers with sandbags and plastic sheeting.

• The stoplog for door 805 was provided with alternative methods for installing the barrier. Newly installed and planned flood protection enhancements There are no planned flood protection enhal')cements at DAEC. Overall, DAEC employs a number of different flooding protection features credited in the CLB that are available, functional and properly maintained respective to their CLB intended flood protection functions.

The DAEC is found to be in compliance with its flood protection requirements per the current site licensing basis based on the inspections of the NE! 12-07 walkdowns and corrective actions implemented as a result of the walkdowns.

• Page 15 of 19 NTTF Recommendation 2.3 (Walkdowns):

Flooding NextEra Energy Resources Duane Arnold Energy Center November 14, 2012 NEE006-PR-001, Revision 0 6. REFERENCES I. Nuclear Energy Institute (NEI), Report 12-07 [Rev 0-A]. Guidelines for Performing Verification Walkdowns of Plant Protection Features.

May 2012 [NRC endo rsed May 31, 2012; updated and is sued June 18, 2012]. 2. U.S. Nuclear Regulatory Commission.

Letter to Licensees.

Request/or Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(/) Regarding Recommendations 2.1, 2.3, and 9.3 of the Near Term Task Force Review of Insights from the Fukushima Dai-ic hi Accident.

March 12, 2012. 3. DAEC UFSAR, Rev. 21, Sections 2.4 and 3.4 4. DAEC PSAR Appendix H 5. DAEC Maintenance Rule Program Module 6 "M onito ring of Structures" Revision 6 6. Endorsement of Nuclear Energy Institute (NEI) 12-07, "Guidel i nes for Performing Verification Walkdowns of Plant Flood Protection Features" May 31, 2012 7. FAQ-006, Inquiry Form-NRC Submittal, Revision 4, Applicable Features for Quantifying APM, September 13, 2012. 8. FAQ-007, Inquiry Form-NRC Submittal, Revision 0, Inspection of Exterior Walls, August 1, 2012. 9. Commonwealth Associates

" Exhibit 14 Maximum Probable Flood" Page 16 of 19 NTTF Recommendation 2.3 (Walkdowns):

Flooding NextEra Energy Resources Duane Arnold Energy Center November 14, 2012 NEE006-PR-001 , Revision 0 7. ATTACHMENTS Attachment 1: FAQ-006 A. TOPIC: Applicable Features for Quantifying APM Source document:

NEI 12-07 B. DESCRIPTION:

Section:3.13

& 5.8 Sections 3.13 and 5.8 provide a definition, description, and examples for Available Physical Margin (APM). In Section 3.13, APM is defined as "the difference between licensing basis flood height and the flood height at which water could affect an SSC important to safety". This inquiry is intended to clarify the latter part of this definition, considering that that some features will not have a clearly defined exceedance height. D. RESOLUTION: (Include additional pages if necessary.

Total pages: __ 2 ___ ) Inquiry nu m ber: __ __,O""'Oc-=6

__ Priority:"""H

__ Sections 3.13 and 5.8 provide a definition, description, and examples for Available Physical Margin (APM). In Section 3.13, APM is defined as "th*e difference between licensing basis flood height and the flood height at which water could affect an SSC important to safety". The latter (underlined) part of the definition can be interpreted as the height at which the flood protection capability of a feature is exceeded.

For some features, the exceedance height can be clearly defined (e.g. flood walls, levees, dikes, cofferdams, flood gates, the elevation of unsealed penetrations or other openings, etc.). For other features (e.g. seal, plug, or water-tight door pressure ratings, pump flow rates, etc.), the exceedance height cannot be clearly defined without performing an engineering analysis that is beyond the scope of the flooding walkdowns.

As a result, it is appropriate to record APM as a simple measurement of height difference, however additional considerations apply. There is a concern that recording a large APM on the Walkdown Record Form could be misleading if the APM is interpreted as margin that is available for additional flood protection without further evaluation. For example, for a flood protection wall that is 10-ft high and the CLB water height is 9.5-ft., it is reasonable to state that the APM is 6-inches for the wall. However, if the previous wall is now 20-ft high and CLB water height is still 9.5-ft, it cannot be stated that the wall's APM is 10.5-ft based on engineering judgment alone. In order to verify a large APM that is not already defined in the existing design documents, an analysis would have to be performed to evaluate the effect of the additional flood height on wall loads and pressure retention capability for any associated penetration seals. As a result, the manner in which an APM should be recorded on the Walkdown Record form depends upon whether the APl\'.I is considered large (an interpretation of what constitutes a "large" APM is at the discretion of the utility).

The following guidance applies. For walkdowns that have not yet been performed and/or documented:

Recording APMs on the Walkdown Record Sheet as a difference in height is a reasonable statement of the available margin based on engineering judgment unless the APM is large. For large APMs, three options are available:

(1) record a smaller, but defensible, APM value based Page 17 of 19 NTTF Recommendation 2.3 (Walkdowns):

Flooding NextEra Energy Resource s Duane Arnold Energy Ce n ter November 14 , 2012 NEE006-PR-001, Revisio n 0 on engineering judgment with a corresponding note in the "comments" section; (2) record no* value for the APM with a corresponding note in the "comments" section that an engineering analysis is necessary to determine the maximum APM the wall can withsta*nd before a functional . failure; or (3) reference the existing FSAR section or design document that supports the APM. Note that this notation should be made in the response to Qll, 023, or Q27 of the Walkdown Record Form, as applicable. For walkdowns that have been completed:

Recognizing that it is not resource effective to revise completed paperwork, it is not necessary to change the way the APM was recorded in completed portions of the Walkdown Record Form. In these cases, APMs that have been recorded as simple measurements of height differences are acceptable as long as the APM determination process did not result in overlooking some potential small margins, as defined by the site per Section 5.8 of NEI 12-07. For Walkdown Reports: Indicate in the walkdown report if any APM information was recorded before the large APM approach described in this FAQ was developed.

Notes: 1. Typically, the CLB for the site will indicate what the probable maximum flood level is and the level to which the SSC important to safety is protected.

If the recorded APM exceeds the difference between these two values and the margin is to be credited for additional flood protection, the margin must be justified by one of the following methods: a. Documented application of reasonable and indepe_ndently verified engineering judgment b. Performance of new engineering analysis c. Reference to an existing document or analysis that support:;

the higher protection level Revision:

4 Date: 9/13/12 E. NRC Review: Not Necessary

___ _ Necessa ry ____ X~--Explanation:

F. Industry Approval:

Documentation Met hod : _____ -=Se=p=t:..:1=3:...,-=2=0=1=-2-'-'m"'"'e=e'--"t~in=g.._

_____ _ Date:. ___ _ G. NRC Acceptance:

lnterpretation

___ ~X~--Agency Position __ _ . Documentation Method: Sept 13, 2012 meeting Date: Page 18 of 19 NTTF Recommendation 2.3 (Walkdowns)

Floodin g NextEra E n e rgy Resou rce s Duane Arnold Energy Center November 14, 2012 NEE006-PR-00 I, Revisi o n 0 Attachment 2: FAQ-007 A. T O PIC: lnsr1ection of exterior walls Source document:

NEI 12-07 Section:5.5.2 B. DESCRIPTION:

We have a wet site where the SSCs are licensed to flood and the core is protected using mitigating actions. Some of the buildings have safety-related equipment below grade and below groundwater levels. The building's concrete walls keep groundwater from entering the structure but there is no me n tion of the walls be i ng credited flood or groundwater protection features in the CLB. I f the walls and any associated penetration seals are not credited in the CLB as providing protection (against surface water or groundwater flooding), do they need to be included in the walkdown scope? On the other hand, if the walls and assoc i ated seals are performing a flood protection function, specifically for groundwater ingress, even though the CLB for flooding i s silent on it, should a visual observation of the walls be performed?

C. Initiator:

Name: J Bellini Phone: (610} 877-6022 Date: 7/31/12 E-Mail: joe.bellini@amec.com D. RESOLUTION:

(Include additional pages if necessary. Total pages: __ 1 ___ ) Inquiry number: 007 Priority: H Any exterior wall (above or below grade) protecting space c r edited as dry in the CLB from groundwater or surface water flooding should be included i n the walkdown scope , even if the exterior walls are not explic i tly mentioned in the CLB. The inspection of the walls should al s o note degrading or nonconforming conditions for associated penetrations , seals , etc., although the penetrations/seals themselves do not need to be listed as separate features, with separate walkdown record forms , unless individually credited in the CLB. The inspection appl i es to portions of the walls below design basis flood and/or groundwater levels. Note that Available Physical Margin should be obta in ed to the lowest unsealed, unqualified and or inspected sealed penetration above the design basis water level. Revision:

0 Date: BL1L2012 E. NRC R~vl~w: Not Necessary X Necessary_

Explanation

F. lndust!l'.

A1rnroval:

Documentation Method: Dat e: Pag e 19 of 19