ML13101A183

Sequoyah, Units 1 & 2 - Response to NRC Request for Additional Information Regarding Revision of the Updated Final Safety Analysis Report to Adopt a Revised Hydrologic Analysis (TS-SQN-12-02)

ML13101A183
Person / Time
Site:	Sequoyah
Issue date:	04/05/2013
From:	Shea J W Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC ME9238, TAC ME9239, TS-SQN-12-02
Download: ML13101A183 (44)

Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402April 5, 201310 CFR 50.410 CFR 50.90ATTN: Document Control DeskU.S. Nuclear Regulatory CommissionWashington, D.C. 20555-0001Sequoyah Nuclear Plant, Units 1 and 2NRC Docket Nos. 50-327 and 50-328Facility License Nos. DPR-77 and DPR-79

Subject:

Response to NRC Request for Additional Information RegardingRevision of the Updated Final Safety Analysis Report to Adopt aRevised Hydrologic Analysis (TS-SQN-12-02) (TAC Nos. ME9238 andME9239)

References:

1. TVA Submittal to NRC Document Control Desk, "Application to ReviseSequoyah Nuclear Plant Units 1 and 2 Updated Final Safety AnalysisReport Regarding Changes to Hydrologic Analysis, (SQN-TS-12-02),"dated August 10, 2012 (ADAMS Accession No. ML122260684).2. Letter from NRC to TVA, "Sequoyah Nuclear Plant, Units 1 and 2 -Request for Additional Information Regarding Revision of the UpdatedFinal Safety Analysis Report to Adopt a Revised Hydrologic Analysis(TAC Nos. ME9238 and ME9239)," dated January 25, 2013 (ADAMSAccession No. ML13018A053).By letter dated August 10, 2012 (Reference 1), Tennessee Valley Authority (TVA)submitted a request for an amendment to the Facility Operating License Nos. DPR-77 andDPR-79 for the Sequoyah Nuclear Plant (SQN), Units 1 and 2. The license amendmentrequest (LAR) proposed to revise the SQN, Units 1 and 2, Updated Final Safety AnalysisReport (UFSAR) to reflect the results from new hydrologic analysis. These proposedchanges are consistent with the latest approved hydrology calculations.Printed on recycled paper U.S. Nuclear Regulatory CommissionPage 2April 5, 2013By letter dated January 25, 2013 (Reference 2), the Nuclear Regulatory Commission(NRC) forwarded a request for additional information (RAI) originating from the NRCHealth Physics and Human Performance Branch (AHPB), and Balance-of-Plant Branch(SBPB). The response to the RAI was due 45 days from its date of issuance, or March 11,2013. However, as discussed with the NRC staff on March 8, 2013 and March 26, 2013,TVA requested an extension of the due date for the response of 25 days, or April 5, 2013.Enclosures 1 and 2 to this letter provide TVA's responses to this RAI. There are nochanges required to the LAR as submitted in the Reference 1 letter as a result of thisadditional information. Consistent with the standards set forth in 10 CFR 50.92(c), TVAhas determined that the additional information as provided in this letter does not affect theno significant hazards considerations associated with the proposed amendment previouslyprovided in Reference 1. TVA has further determined that the proposed amendment stillqualifies for a categorical exclusion from environmental review pursuant to the provisionsof 10 CFR 51.22(c)(9). Additionally, in accordance with 10 CFR 50.91 (b)(1), TVA issending a copy of this letter, the enclosures, and the attachments to the TennesseeDepartment of Environment and Conservation.There are no new regulatory commitments included in this submittal. Please address anyquestions regarding this submittal to Ed Schrull at (423) 751-3850.I declare under penalty of perjury that the foregoing is true and correct. Executed on this5th day of April 2013.k~sully,ice resident, Nuclear Licensing

Enclosures:

1. Response to NRC Health Physics and Human Performance Branch (AHPB)Request for Additional Information (RAI)2. Response to NRC Balance-of-Plant Branch (SBPB) Request for AdditionalInformation (RAI)cc (Enclosures):NRC Regional Administrator -Region IINRC Senior Resident Inspector -Sequoyah Nuclear PlantDirector, Division of Radiological Health, Tennessee State Department of Environmentand Conservation ENCLOSURE1TENNESSEE VALLEY AUTHORITYSEQUOYAH NUCLEAR PLANTUNITS 1 AND 2RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)

Subject:

Application to Revise Sequoyah Nuclear Plant Units I and 2 Updated FinalSafety Analysis Report Regarding Changes to Hydrologic Analysis,(SQN-TS-12-02)1.0 AHPB RAI Question IWhat, if any, operator actions are being changed, added, or deleted besides thosesupporting the installation of the spent fuel pit cooling pump enclosure caps, the sandbagging of the diesel generator (DG) building, and the installation of temporary barriers onthe earthen embankments of the dams at the Cherokee, Fort Loudoun, Tellico, and WattsBar Reservoirs?1.1 TVA Response -AHPB RAI Question 1There are no other changes, additions, or deletions to Sequoyah Nuclear Plant Units 1and 2 (SQN) site flood mode preparation actions based on the revised probable maximumflood (PMF) and design basis flood (DBF) levels, or the reevaluation of flood warningtimes, in the updated hydrologic analysis.As described in the SQN license amendment request (LAR), the Stage I and Stage IIFlood Warning times remain at 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> and 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br />, respectively. The only change asa result of the reevaluation is the revised forecasted plant site water levels where Stage IFlood Warning actions are required to begin. The Stage I threshold levels will beaddressed in the TVA River Operations instructions that determine when the SQN siteshould be notified of a Stage I Flood Warning. These revised action levels do not change,add, or delete SQN site flood mode preparation actions, only the entry point criteria for theabnormal operating procedure (AOP) for external flooding. These revised action levels willbe incorporated in the TVA River Operations instructions prior to the implementation dateof the final NRC-approved license amendment.There are other flood mode preparation actions that have been revised as improvementswere identified as a result of simulations and validation of the AOP and instructionsperformed by TVA. These changes are not required as a result of the updated hydrologicanalysis, but rather as a result of improving implementation of flood mode preparation andoperation procedures and instructions to ensure the current licensing basis requirementsfor meeting flood warning times are met.Page 1 of 29 ENCLOSURE1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)2.0 AHPB RAI Question 2What kind of training is planned for actions supporting the proposed changes to the SQNUFSAR? How often will training on the flood procedure/plan be done? When will trainingbe complete? For example, will training be complete prior to issuance of the revisedUFSAR proposed in this LAR?2.1 TVA Response -AHPB RAI Question 2Changes to SQN site procedures and instructions are evaluated as part of the existing SiteTraining Program. These changes to the procedures and instructions to comply with theSQN UFSAR changes are required to be implemented prior to the implementation date ofthe final NRC-approved license amendment.The required changes to the procedures and instructions have been identified, and atraining needs analysis in accordance with the Site Training Program will determine thefinal content and schedule for training. Changes to abnormal operating procedures thatrequire training are communicated through the use of a standing order to brief operatorson the major changes, and classroom training is conducted during the next scheduledlicensed operator requalification cycle.3.0 AHPB RAI Question 3List the procedures affected by the proposed LAR along with a short summary of thechange. When will procedure changes, additions, and deletions associated with theproposed UFSAR changes be completed? For example, will procedures be revised andissued prior to initiation of training?3.1 TVA Response -AHPB RAI Question 3AOP-N.03, "External Flooding," controls the overall timing and sequence of implementingactions for flood mode preparations and operations, and utilizes implementing workorders, general operating instructions, emergency operating instructions, flood preparationmaintenance instructions, and other AOPs to complete the required actions by theapplicable SQN site organizations. As a result of the SQN LAR, AOP-N.03 will be revisedto address installation of permanent engineered flood barriers for the Diesel GeneratorBuilding during a Stage I Flood Warning and installation of the Spent Fuel Pit Cooling(SFPC) pump enclosure caps during a Stage II Flood Warning.Other changes to AOP-N.03 have been made that are not directly the result of the SQNLAR. These changes address the results of simulations performed to verify the capabilityto complete required flood mode preparations within the required Stage I and Stage IIFlood Warning times, and are not a result of the updated hydrologic analysis which doesnot revise these limiting times.As discussed in the response to AHPB RAI Question 2, required changes to theprocedures and instructions have been identified, and are required to be implementedprior to the implementation date of the final NRC-approved license amendment. InPage 2 of 29 ENCLOSURE1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)accordance with the Site Training Program, a training needs analysis will determine thefinal content and schedule for training.4.0 AHPB RAI Question 4Were any human performance lessons learned from operating experience, sister plants,the Fukushima incident? If yes, describe?4.1 TVA Response -AHPB RAI Question 4Changes to the procedures and instructions have been implemented to address humanperformance lessons learned from operating experience and the Fukushima incident. Inaddition, changes have been implemented based on informal reviews of procedures fromthe other TVA sites. For example, AOP-N.03 was recently revised to streamline theprocess for establishing flood mode core cooling during a Stage II Flood Warning basedupon insights gained from a review of the Watts Bar Nuclear Plant flood procedure.5.0 AHPB RAI Question 5Was at least one full complement of required personnel used in the verification andvalidation of the proposed flood plan? If not, what plans have been made to assure that arepresentative sample of personnel is included in verification and validation of the floodplan?5.1 TVA Response -AHPB RAI Question 5In response to the nuclear fuel damage at Fukushima Daiichi due to earthquake andsubsequent tsunami, the United States Nuclear Regulatory Commission (USNRC / NRC)requested information pursuant to Title 10 of the Code of Federal Regulations,Section 50.54(f) (NRC Letter to Licensees, dated March 12, 2012, RegardingRecommendations 2.1, 2.3, and 9.3 of the Near Term Task Force (NTTF) Review ofInsights from the Fukushima Dai-ichi Accident). As part of this request, a reasonablesimulation was performed of the flood response AOP in accordance with an approvedprocedure, CTP-FWD-100, "Flood Protection Walkdowns." The USNRC issued anEndorsement Letter on May 31, 2012 that endorsed the Nuclear Energy Institute(NEI) 12-07, "Guidelines for Performing Verification Walkdowns of Plant Flood ProtectionFeatures" document. The guidance followed for the reasonable simulation was consistentwith NEI 12-07.During the reasonable simulation, an active Senior Reactor Operator (SRO) steppedthrough the procedure and, with the assistance of Maintenance, Engineering, RadiationProtection, a retired Unit Supervisor SRO, and a retired Shift Manager, developed atimeline for the steps of the procedure. Personnel required for each step were alsodetermined in order to assess the adequacy of available resources, ensuring that a fullcomplement of required personnel would be available to perform the required flood modepreparation actions.Page 3 of 29 ENCLOSURE1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)The ability of the plant to complete flood mode preparations within the Current LicensingBasis (CLB), and consistent with the proposed licensing basis in the SQN LAR, wasevaluated during initial reasonable simulation results. Discussion and evaluation of theinstructions given in AOP-N.03 were made during the reasonable simulation. As eachstep of the procedure was discussed, estimates of time to perform the actions in theprocedure were made. The flood scenario identified as most critical in the Updated FinalSafety Analysis Report (UFSAR) was used as the basis for evaluating whether theinstructions could be implemented in the available time. The reasonable simulation alsoassessed implementation of any actions required for flood protection features. Anexample of a time dependent activity is the time to install the spool pieces to realign thesystems.The reasonable simulations occurred between September 10, 2012, and September 21,2012. SQN Units 1 and 2 were assumed to be at 100% power when the Stage I FloodWarning was received from the River Forecast Center staff. The reasonable simulationsincluded the following steps:1. Raw data tabulation was performed from individual procedure step and reasonablesimulation exercises required to complete flood mode preparations. No integration orresource loading had occurred.2. The raw data was integrated and resource loaded considering the flood mode AOPactions, maintenance instructions actions, and chemistry sampling. These activitieswere sequenced and the actions were evaluated to determine which can be performedin parallel versus in series.3. Stage I activities included the rapid shutdown of the plant using AOP-C.03, "RapidShutdown or Load Reduction," and plant communications with local media and stategovernment agencies. Stage I Flood Warning activities also included communicationsmade to acquire off-site plant personnel required to implement the flood protectionprocedures.4. Additional off-site personnel assumed to be available to implement the flood mitigatingpreparation procedures were determined in the following manner. The PMF event wasconservatively assumed to start on a holiday weekend night to minimize on-site staffand off-site staff availability for being phoned in for work. The assumptions for themanpower required are provided below:a. Maintenance available for call in during PMF flood response includes the following:* 93 total craft personnel plus foreman that includes Mechanical, Electrical andInstrument and Controls (I&C) per shift0 Normal Operating Crew (NOC) includes one Mechanical, one Electrical,one I&C, and a supervisor; the NOC is already on site0 Four additional personnel per shift not on site but available for call in0 Assumed 67% (approximately 60) of available personnel not on site to haveFitness for Duty (FFD) issues or other complications due to local flooding andunable to respond to sitePage 4 of 29 ENCLOSURE1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)* Total of 29 maintenance personnel expected to respond to the callb. Total craftsmen available after call in to mitigate flood event includes the following:* 29 expected to respond to the call* Four personnel (NOC) already on-site* Total 33 personnel available to mitigate flood event.o Assumes craft: 14 Mechanical, eight Electrical, and eight I&Co Assumes three supervisors* Utilizing 10 crews of three craft with three supervisors.c. NOC Operations includes the following:" One Shift Manager -SRO* Three Unit Managers -SROs (Unit SRO, Shift Technical Advisor, and WorkContol SRO)" Four Reactor Operators* Eight Auxiliary Unit Operatorsd. Additional Operations personnel available to be called in includes the following:* 94 Total (Expect 50% that can respond).5. The Stage I Flood Warning activities were successfully accomplished within the CLB10 hour time period, which is the same as in the SQN LAR.6. The critical path Stage II Flood Warning activities were determined by development ofa timeline.The reasonable simulation verified that the actual number of personnel required toimplement the flood mode preparation activities were bounded by the assumption ofavailable personnel described in item 4 above. Therefore, based on the reasonablesimulation, it was determined that the required personnel are available and capable ofimplementing the Stage I and Stage II Flood Warning preparations within the overall floodmode preparation completion time of 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br /> allowed by the updated hydrologic analysis.6.0 AHPB RAI Question 6During the probable maximum flood (PMF), what communication methods will be likely tofail (fully or partially) and which will still be available for individuals to communicate withthe control room, technical support center, and other plant areas? Will site-wideannouncements be possible during all stages of the PMF?6.1 TVA Response -AHPB RAI Question 6During emergencies such as a PMF event, SQN site operations and Emergency Planpersonnel have several communication methods available to communicate with the controlroom, technical support center, and other plant areas. As described in the SQN UFSARPage 5 of 29 ENCLOSUREIRESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)Subsection 9.5.2, the normal primary intraplant communications systems for voice andplant paging are the sound powered telephone systems, inplant radio system, ElectronicPrivate Branch Exchange (EPBX) telephone equipment, and loud speaker paging.As described in SQN UFSAR Table 9.5.2-1, the communications equipment that isassured to be available for intraplant communications during a PMF event with and withouta loss of offsite power includes portion of the sound powered telephone system and theinplant radio system, except for those components of the system that are submergedduring the event but not needed since the areas are inaccessible during the flood.To prevent loss of the sound powered phones during a PMF event, AOP-N.03 requiresperformance of flood preparation maintenance instruction FPMI-12.10, "Disconnection ofSound-Power Telephones Located Below Elevation 732," during Stage II Flood Warningpreparations. The purpose of this instruction is to describe the procedure fordisconnecting the sound powered telephones located below elevation 732 ft to preventinterruption in communications in other areas as a result of a PMF event. Portions of thesound powered telephone systems that remain above the flood levels are available duringa PMF event. Therefore, wired voice communications above the DBF levels are assuredthroughout a PMF event.The inplant radio system provides voice communications throughout the plant for plantpersonnel. This system consists of repeaters, remote control units and very highfrequency (VHF) portable radios. A Radio/Cell Phone System provides a diversecommunications system for voice, paging, and text messaging that is available both onsiteand offsite. The system interfaces with the VHF inplant system in the turbine building toallow communications through the existing VHF Distributed Antenna System. Portions ofthe inplant radio system that remain above the flood levels are available during a PMFevent, but only through direct radio-to-radio communications. Therefore, wireless voice,paging, and text messaging communications above the DBF levels are assuredthroughout a PMF event.The EPBX is installed to provide primary 2-way communications throughout SQN as wellas access to offsite circuits, and provides for loud speaker paging through the generalplant public address system discussed below. The EPBX is powered from a 48V DCsource. This source consists of a telephone battery charger, a spare battery charger, aregulating power board, and a battery. The telephone battery charger is fed from anon-i E source with an alternate feed from a Train A diesel-backed board. The sparebattery charger is fed from a Train A diesel-backed board with an alternate feed from aTrain B diesel-backed board. The 48V batteries and chargers which power this systemare below the DBF level. Therefore, the EPBX may or may not be available during anexternal flood event with a loss of offsite power, depending on actual flood conditions, butis not available once flooding reaches plant grade.Paging speakers for the general plant public address system are installed in the auxiliary,reactor, turbine, and control buildings. Paging handsets are provided in both unit controland the auxiliary control room. In addition to the paging handset locations, this equipmentmay be accessed from any EPBX telephone. The speaker-amplifiers are fed in parallelfrom an alternating current lighting source. The paging equipment is dispersed in thecontrol building and powerhouse areas. Single or multiple open circuits or amplifier failurePage 6 of 29 ENCLOSURE1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)in individual units will not prevent the remaining equipment from functioning. The failure ofthe equipment will not impair the use of the paging equipment from the local pagingstations located in the control room, or the auxiliary control room. The general plant publicaddress system may or may or may not be available during an external flood event with aloss of offsite power, depending on actual flood conditions, but is not available onceflooding reaches plant grade.In response to the nuclear fuel damage at Fukushima Daiichi due to earthquake andsubsequent tsunami, the United States Nuclear Regulatory Commission (USNRC / NRC)requested information pursuant to Title 10 of the Code of Federal Regulations,Section 50.54(f) (NRC Letter to Licensees, dated March 12, 2012, RegardingRecommendations 2.1, 2.3, and 9.3 of the Near Term Task Force (NTTF) Review ofInsights from the Fukushima Dai-ichi Accident). As part of this request, TVA providedadditional information requested regarding plans to enhance existing communicationssystems power supplies until the communications assessment in response toRecommendation 9.3 and the resulting actions are complete. As stated in the responseprovided by letter from TVA to the NRC, "Tennessee Valley Authority (TVA) -90-DayResponse to NRC Request for Information Pursuant to Title 10 of the Code of FederalRegulations 50.54(f) Regarding Recommendation 9.3 of the Near-Term Task ForceReview of Insights from the Fukushima Dai-ichi Accident," dated June 11, 2012 (ADAMSAccession No. ML12164A678), TVA deployed seventeen (17) satellite phones at eachlicensed operating TVA nuclear facility. These phones replaced and upgraded olderphones that were previously located at each site. An additional seventeen (17) satellitephones were deployed at TVA Nuclear Power Group (NPG) offices in the TVA Corporateheadquarters located in Chattanooga, Tennessee. TVA also purchased twenty (20)portable generators. These 2000-Watt portable generators were obtained to keep thesatellite phone batteries charged. Five (5) of these generators have been placed at eachof the three TVA licensed operating nuclear facilities, and the remaining five (5) generatorswere sent to the Central Emergency Control Center (CECC), TVA's offsite emergencycenter, located in Chattanooga, Tennessee. These generators at each site are stored in asecured location on the site owner-controlled area. Radios and sound-powered phonesystems are also available at TVA licensed operating facilities for onsite communicationswith operators in the field and the control room for safe shutdown and recovery. Jacks forthe installed sound-powered phone systems are located in areas needed to supportmonitoring and operation of essential equipment. TVA nuclear facilities were previouslyprovided with radios dedicated for response to postulated large area fires within the plant.Upon a loss of radio towers these radios can still be used in the radio-to-radio mode withinthe facility. Batteries for these radios may also be charged using the portable generatorspreviously mentioned. TVA has developed documented guidance for deploying theportable generators described above during and after a Beyond Design Basis ExternalEvent.Page 7 of 29 ENCLOSUREIRESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)7.0 AHPB RAI Question 7Describe the changes to the simulator, if any, that are needed to support the proposedlicense amendment.7.1 TVA Response -AHPB RAI Question 7There are no changes to the simulator required as a result of the updated hydrologicanalysis and the resulting minimal required changes to AOP-N.03, "External Flooding,"including associated changes to implementing work orders, general operating instructions,emergency operating instructions, flood preparation maintenance instructions, and otherAOPs. The physical interim compensatory measures and the replacement permanentmodifications made to the facility do not affect the physical layout and control or softwarerequirements for the simulator.8.0 AHPB RAI Question 8Describe any credible errors that could affect the pre-staging or the actual placing ofsandbags around the DG building entrance?a. Will the placement of the sandbags interfere with operation or corrective maintenance?Where are the sandbags pre-staged? If pre-staged at a distance from the DG building,how will they be moved and finally placed around the building?b. Are the sandbagging actions specified in a controlled procedure? If yes, provide theprocedure with markups showing any revisions necessary to support this LAR.c. How much do the sandbags weigh, how many are needed, how many people will beneeded, and how long will it take? Have validation walkthroughs been performed?d. Is training required? If yes, how often?8.1 TVA Response -AHPB RAI Question 8The installation of permanent plant modifications to protect the Diesel Generator Buildingentrances from a DBF, including future installation of permanent engineered flood barriers,has replaced the use of sandbag berms. These plant modifications and the requiredactions for installation of permanent engineered flood barriers are described in theresponse to SBPB RAI Question 2 in Enclosure 2 of this submittal.9.0 AHPB RAI Question 9Describe any credible errors that could be made when installing the spent fuel pit coolingpump enclosure caps. Are the involved actions described in a controlled procedure? Willtraining be provided?Page 8 of 29 ENCLOSUREIRESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)9.1 TVA Response -AHPB RAI Question 9The Spent Fuel Pit Cooling (SFPC) pumps are located on a platform at elevation 721.0 ftin the Auxiliary Building. The SFPC pumps are protected from flooding by AuxiliaryBuilding walls on two sides and the SFPC pump enclosure constructed of steel plating onthe other two sides. The SFPC pump enclosure provides protection up to a flood elevationof 724.5 ft (top of the two sides constructed of steel plating), which is adequate to provideprotection from the proposed DBF level in the Auxiliary Building in the SQN LAR (elevation722.5 ft).A design feature of the enclosure includes two 6-inch diameter drains located next to eachother on the enclosure that are normally open during operation to allow any leakage fromthe SFPC pumps to drain to the normal Auxiliary Building drains as shown in Figure 1below:PLAN EL. 714(2 ea)Section B-B(48W1216-)Figure 1 -SQN Spent Fuel Pit Cooling Pump Enclosure CapsPage 9 of 29 ENCLOSURE1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)These drains are capped as required by AOP-N.03 during Stage II Flood Warningpreparations in accordance with maintenance instruction 0-FP-MXX-000-01 1.0, "FloodPreparation SFPC Pump Enclosure Caps, SFPCS Heat Exchangers, RCP Thermal BarrierBooster Pumps, and RHR Heat Exchanger Spool Pieces." The drains are located at thebottom of the enclosure near the floor elevation of 714.0 ft, the caps are attached to thedrains by chains, and the drains are readily accessible during Stage II Flood Warningpreparations.The actions in maintenance instruction 0-FP-MXX-000-01 1.0 are to:1. Locate the drains based on the description provided in the maintenance instruction,and a drawing included in Appendix B of the maintenance instruction, showing thelocation of the drains, and2. Install both caps using thread sealant.In addition, Section 7.1 of 0-FP-MXX-000-01 1.0 requires a visual check of the caps afterinstallation during Stage II Flood Warning preparations. Based on the non-complex natureof the task, the instructional details including plan and sectional drawing, the staging of thecaps at the drains using attached chains, and the visual check after installation, theprobability of error in installing the caps is extremely low. In accordance with the SiteTraining Program, a training needs analysis of the AOP and maintenance instructiondetermines the final content and schedule for training.10.0 AHPB RAI Question 10On page 15 of 39 in Enclosure 1 of the LAR dated August 10, 2012, the licensee statesthat TVA's climatic monitoring, flood predicting systems and flood control facilities permitearly identification of potentially critical flood producing conditions and reliable prediction offloods that may exceed plant grade well in advance of the event. Is this prediction doneusing a controlled procedure consistent with the assumptions of the current hydrologyanalysis? What actual margin is associated with the term "well in advance"? Describe interms of approximate number of minutes, hours, or days.10.1 TVA Response -AHPB RAI Question 10TVA's climatic monitoring, flood predicting systems and flood control facilities are underthe jurisdiction of TVA River Operations. This organization is responsible for balancing thecompeting demands of the Tennessee River and its tributaries with respect toflood-damage control, navigation, dam safety, hydroelectric power production, recreation,water supply, and water quality. Within the TVA River Operations organization, the staff ofTVA River Scheduling is responsible for scheduling day-to-day operations of the TVAintegrated river system, including flood-damage control, navigation, power production,water quality, water supply, and recreation.Within TVA River Scheduling, the River Forecast Center staff is responsible fordeveloping, dispatching, and monitoring real-time multipurpose operating plans for theimpoundment and releases of water from TVA-managed reservoirs. Operating plans arePage 10 of 29 ENCLOSURE1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)developed 365 days a year and monitored around-the-clock from the River ForecastCenter in Knoxville, Tennessee. The River Forecast Center balances operating plans inorder to meet system demands for flood-risk reduction, navigation, hydroelectricgeneration, water quality, water supply, and recreation. The River Forecast Center alsocoordinates daily operating plans with the U. S. Army Corps of Engineers.In developing forecasts, the River Forecast Center uses state-of-the-art equipment tomonitor the river system and adjusts operations based on the continuously changingdemand for water. Weather conditions, rain data, reservoir inflows and outflows, andreservoir elevations are monitored in real-time through satellite and hard-linedcommunication equipment. Continuous monitoring of reservoir information allows theRiver Forecast Center to quickly respond to system demands during critical periods. Oncecollected and validated, the data is used as input for modeling tools for simulatingreservoir releases and developing strategies for multiple operating scenarios. The riverforecasts are used to disseminate information regarding reservoir levels and scheduledwater releases to internal and external stakeholders. Information from the forecasts canthen be used in a wide variety of decision-support tools, including bulk electric systemplanning, evaluating thermal cooling needs at TVA coal fired and nuclear plants,emergency management, river-shipper planning, and recreational user scheduling. TheRiver Forecast Center serves as the focal point of information for any issue related tooperating the Tennessee River system.TVA River Operations is responsible for notification and response in any type ofemergency at one or more of its assets that has the potential to affect the health andsafety of the TVA workforce or the general public, the environment, or TVA property.River Operations is also responsible for agency-level support during large-scaleemergencies that affect more than one strategic business unit or the whole agency. TheEmergency Preparedness group in River Operations develops procedures guidingemergency response for such emergencies and maintains testing, training, and exercisesto ensure effective emergency planning and readiness by emergency staff.RO-SPP-35.1, "River Operations Emergency Response Plan," is the highest tieremergency response procedure in River Operations. It covers the overall emergencyresponse philosophy (based on the National Incident Management System (NIMS) andIncident Command System), and addresses the systematic approach to responding toemergencies. This procedure prescribes a consistent response process that applies toany emergency that may occur at a River Operations asset such as dam safety, fire,environmental releases, terrorist attack, etc. The response procedures contained withinRO-SPP-35.1 are consistent with Homeland Security Presidential Directive 5 (HSPD-5),Management of Domestic Incidents, which requires the use of NIMS by the FederalGovernment in domestic incident management and emergency prevention, preparedness,response, recovery, and mitigation activities.ROR-SPP-35.3, "Dam Safety Emergency Action Plans," describes the development andapproval of individual Emergency Action Plans for dam safety for each of the of RiverOperations 49 projects (i.e., dams and associated reservoirs). The procedure contains thegeneric language and process that apply for response to a dam safety emergency at anyof the River Operations projects. Each project-specific Emergency Action Plan contains ageneric response section detailing the purpose of the Emergency Action Plan, roles andPage 11 of 29 ENCLOSUREIRESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)responsibilities, response processes, and response aids such as a notification flow chartand checklists for primary users. Individual Emergency Action Plans also include alocation specific emergency notification directory, flood inundation maps unique for eachproject, and other specific dam safety resources appropriate for the project in question.Emergency Action Plans are controlled documents which are distributed within TVA and toexternal emergency response partners such as county emergency-management agencies,the National Weather Service, the U.S. Army Corps of Engineers, and other entities whichmay be affected by or engaged with TVA in the unlikely event of a dam breach or probablemaximum flooding. The top priority for River Operations during a dam safety emergencyis to maintain system integrity and ensure the safety of the public and TVA property, to thegreatest extent possible. The Emergency Action Plans are maintained and exercised inaccordance with procedures TVA-SPP-27.6, "Emergency Preparedness for Dams," andRO-SPP-27.6, "River Operations Emergency Preparedness for Dams," which draw on theFederal Guidelines for Dam Safety and the Federal Energy Regulatory CommissionEngineering Guidelines for the Evaluation of Hydropower Projects.RO-SPP-35.4, River Operations & Renewables Continuity of Operations (COOP) Plan isintended to ensure that River Operations remains capable of conducting its essentialfunctions under all threats and conditions in order to support the TVA Mission EssentialFunctions. The procedure provides plans for continuing to operate if one of RiverOperations primary operating locations (Knoxville, Tennessee or Chattanooga,Tennessee) is rendered unusable. The process provides for identification of essentialpersonnel and alternate operating locations for such personnel so that they may continueto perform their essential functions.In order to be able to implement the requirements of River Operations emergencyresponse procedures, the Emergency Preparedness program provides training to staff,coordinates with outside agencies to maintain working relationships, and manages theTVA River Operations Emergency Operations Center (REOC) located in Chattanooga,Tennessee. This facility provides a location for emergency staff to gather to supportresponse actions at the site of an emergency. The Emergency Preparedness staff is alsoresponsible for coordinating with the agency-level emergency entity, Crisis andEmergency Management, to ensure agency procedures and programs are beingsupported and incorporated effectively into River Operations processes.The River Forecast Center staff is responsible for forecasting inflows, scheduling outflows,running hydrothermal models; monitoring rainfall, stream flows, reservoir headwaters,tailwater elevations, reservoir releases, dissolved-oxygen levels, temperature monitoringstations; running forecast models for the integrated operations of the Tennessee River andreservoir system; making internal and external notifications as appropriate; and serving asthe point of contact for river system emergency actions. The River Forecast Center staffforecasts inflows into the Tennessee Valley watershed for a 14-day period, which involvesassessing rain on the ground and determining how much of that rain will end up in theTennessee River system as runoff, as well as considering the likelihood of future rain inweather forecasts.The River Forecast Center serves as the point of contact for river system emergencyactions within the Tennessee Valley and makes notifications of high flows, elevations andother system impacts to appropriate emergency management agencies and other internalPage 12 of 29 ENCLOSUREIRESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)and external entities, including notifications to the SQN control room supervision of Stage Iand Stage II Flood Warnings, as specified in the TVA River Scheduling NotificationDirectory, a desktop instruction that is maintained by TVA River Scheduling for use by theRiver Forecast Center staff during emergencies. Rainfall, stream flows, reservoirheadwaters, reservoir tailwaters and reservoir releases are monitored on a 24-hour basisfor compliance with planned operations. Reservoir elevations and discharge flow rates arealso forecast for the system for a 14-day period. A computer-based RiverWare model isused to simulate weather conditions, reservoir inflows, reservoir outflows, and reservoirelevations. RiverWare is a river-basin modeling software system developed by theUniversity of Colorado, under primary sponsorship by TVA and the U.S. Bureau ofReclamation. Optimization and simulation functions of this model have been used forseveral years by TVA to schedule the operation of the reservoir system.The formal Stage I and Stage II Flood Warning notifications from the River ForecastCenter staff, under the direction of the River Scheduling Lead Engineer, are made to SQNcontrol room supervision based on rainfall on the ground observed measurements, with noconsideration of forecasted rainfall. This is consistent with the assumptions of the currenthydrology analysis. However, the River Forecast Center maintains an ongoing forecast ofreservoir levels for a 14-day period. The forecast (prediction) is based on normalforecasting processes utilized by the River Forecast Center on a daily basis for forecastingreservoir flows and elevations for multiple purposes, including flood control, as describedabove and documented in TVA Standard Programs and Processes TVA-SPP-20.1,"Forecasting, Scheduling, and Monitoring the Tennessee River System."There are various postulated 9-day rain events which could result in potentially reachingthe Stage I and Stage II Flood Warning thresholds. The initial trigger point for activation ofthe REOC is based on predicted headwater elevations at each dam. Therefore, it wouldbe possible for the River Forecast Center to forecast the rain events and predict the triggerheadwater elevations several days in advance. Thus, early declaration of Stage I andStage II Flood Warnings are possible for these situations. For additional discussion of themethods and instructions used by the River Forecast Center to determine conditions forissuing Stage I and Stage II Flood Warnings, refer to the response to AHPB RAIQuestion 12.The discussion in the SQN LAR of climatic monitoring and early identification of potentiallycritical flood producing conditions is based on the use of predicted rainfall by the RiverForecast Center in addition to the rainfall which has already occurred. Within thelimitations of weather forecasting techniques, the predicted rainfall forecasts provideadditional guidance regarding the possible severity of future precipitation up to days inadvance. The River Forecast Center river forecasts routinely incorporate predictedrainfall, and can accurately predict river elevations that would occur if the rainfall eventhappened as forecast over the next 10 days. However, as defined in the SQN LAR, theformal Stage I and Stage II Flood Warning plans are based solely on observed rainfall,which is shown to provide the minimum time of 31 hours3.587963e-4 days <br />0.00861 hours <br />5.125661e-5 weeks <br />1.17955e-5 months <br /> from the critical rainfall occurringuntil elevation 703 ft is observed at SQN (10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> for Stage 1, 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> for Stage II, andfour hours for additional margin). Because of the extensive historical experience andknowledge of operations of the Tennessee River watershed by the River Forecast Center,the quality of climatic monitoring and early identification of potentially critical floodproducing conditions is assured.Page 13 of 29 ENCLOSURE 1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)11.0 AHPB RAI Question 11The licensee states on page 29 of 39 in Enclosure 1 of the LAR: "Flood warnings areissued in real-time by TVA RO [River Operations]." In what form are the flood warningsissued? How does the SQN control room receive the warning and how long does it take toget from TVA (RO) to the control room supervisors?11.1 TVA Response -AHPB RAI Question 11Flood notification from the River Forecast Center staff, under the direction of the RiverScheduling Lead Engineer, may occur in advance of the 27-hour preparation period.Refer to the response to AHPB RAI Question 12 for additional details on the forecast andnotification process. Surveillance instruction 0-SI-OPS-244-215.0, "Flood ProtectionCommunications," provides further assurance that the earliest possible notification offloods potentially exceeding plant grade can be provided. The River Forecast Center staffwill predict flood levels based on rainfall on the ground or potential failure problems withone or more dams combined with critical water-head elevations and flood producingrainfall. During these events communications are established directly between SQNcontrol room supervision and the River Forecast Center staff every three hours, until theRiver Forecast Center staff determines that the potential for flooding above plant grade nolonger exists. Once the River Forecast Center staff declares that a Stage I Warning Planthreshold has been reached, AOP-N.03 requires implementation of surveillance instructionO-SI-OPS-244-215.0. The surveillance instruction ensures that these communications canbe established and maintained between the SQN control room operators and the RiverForecast Center staff in the REOC once every three hours.12.0 AHPB RAI Question 12On page 30 of 39 of the LAR, the licensee states, "... lower forecast threshold warningflood elevations are used in some situations to assure that the 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br /> pre-floodtransition interval is always available." Who makes this decision, on what basis? Will theemergency action level notifications move forward in concert with the warning(s)?12.1 TVA Response -AHPB RAI Question 12The River Forecast Center staff within the TVA River Operations organization, under thedirection of the River Scheduling Lead Engineer, is responsible for determining whenStage I and Stage II Flood Warnings are to be issued. Prior to declaring a Stage I orStage II Flood Warning at the SQN site, the River Forecast Center continuously monitorsrainfall and monitors the headwater elevation behind the upstream dams, and uponpredicting a critical headwater elevation for each dam based on observed rainfall the RiverForecast Center staff makes notification based on the River Operations EmergencyResponse Plan to the Asset Owner for River Operations non-power assets (the TVA RiverScheduling General Manager). This notification includes the time at which the criticalheadwater elevation is forecasted to occur. The Asset Owner (i.e., the responsible personfor operations of the affected dam) directs the REOC to activate in 'advisory' status. An'alert' status is initiated for the REOC at the request of the Incident Commander after thePage 14 of 29 ENCLOSURE1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)contractor is notified to mobilize equipment for closure of the public access (PA) gaps inthe HESCO modular flood barriers at Cherokee Dam, Fort Loudoun Dam, Tellico Dam,and Watts Bar Dam as described in TVA River Operations Cherokee Dam, FortLoudoun/Tellico Dams, and Watts Bar Dam Emergency Action Plans (EAPs). Theseactions take place at predicted flooding conditions below those required for a Stage I orStage II Flood Warning at the SQN site, which allow for early prediction of meeting Stage Iand Stage II Flood Warning threshold levels.If the River Forecast Center staff observes a specified critical headwater elevation behindthe dams, the Asset Owner (i.e., the responsible person for operations of the affecteddam) is notified of the flooding condition. The Asset Owner declares a dam safetyemergency -Condition YELLOW (based on TVA River Operations procedureRO-SPP-35.1) and notifies the REOC. The REOC goes to 'activation' status. The REOCIncident Support Staff supports site activities throughout activation of the REOC.The River Forecast Center maintains an ongoing forecast of reservoir levels for a 14-dayperiod. The forecast (prediction) is based on normal forecasting processes utilized by theRiver Forecast Center on a daily basis for forecasting reservoir flows and elevations formultiple purposes, including flood control, as described above and documented in TVAStandard Programs and Processes TVA-SPP-20.1, "Forecasting, Scheduling, andMonitoring the Tennessee River System." There are various postulated 9-day rain eventswhich could result in potentially reaching the Stage I and Stage II Flood Warningthresholds. The initial trigger point for activation of the REOC is based on predictedheadwater elevations at each dam. Therefore, it would be possible for the River ForecastCenter to forecast the rain events and predict the trigger headwater elevations up to daysin advance. Thus, early declaration of Stage I and Stage II Flood Warnings are possiblefor these situations.The requirements for the final Stage I and Stage II Flood Warning determinations areaddressed by the TVA River Scheduling Notification Directory, a desktop instruction that ismaintained by TVA River Scheduling for use by the River Forecast Center staff duringemergencies. For SQN, a primary number and an alternate number are provided toensure that the SQN control room supervision is notified regarding potential floodingevents. The TVA River Scheduling Notification Directory includes criteria for early warningas well as for Stage I and Stage II Flood Warning thresholds being reached. The earlywarnings include notification that the REOC is activated for either a flood condition, or for adam safety emergency involving a SQN-critical dam, which includes Cherokee, Douglas,Norris, Fontana, Hiwassee, and Blue Ridge Dams. Early warning will also be issued in theinterim if "Emergency Condition Red" (i.e., emergency classification that represents a veryserious situation where failure of a dam has already occurred or is imminent) exists for aSQN-critical dam prior to activating the REOC.A Stage I Flood Warning is issued when the specified SQN threshold flood warning levelfor the season of the year is predicted to be exceeded at SQN in 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br /> or more. AStage II Flood Warning is issued when the specified SQN threshold flood warning level ofelevation 703 ft (2 ft below plant grade elevation 705 ft) is predicted to be exceeded atSQN in 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> or more. There are three specific potential flood scenarios addressed inthe TVA River Scheduling Notification Directory, which includes the following:Page 15 of 29 ENCLOSURE1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)1. For potential seismic dam failure(s) or other dam safety emergencies, the RiverForecast Center staff would be required to take the following actions:a. An Early Warning is immediately issued to SQN control room supervision (at thespecified primary and alternate numbers) of a dam safety "Emergency ConditionRed" (i.e., dam failure has occurred or could occur in less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) involvinga SQN-critical dam, and interim communications are maintained using a specifiedinterim phone number prior to activating the REOC.b. An Early Warning is immediately issued to SQN control room supervision when theREOC is activated by River Forecast Center staff for flood conditions and/or for adam safety emergency involving a SQN-critical dam.c. Communications are maintained with SQN control room supervision on at leastthree-hour intervals (or more frequently, if needed).d. If a dam failure is confirmed, a Stage I Flood Warning is immediately declared.Dam failure outflow and resulting downstream river elevations are modeled. Ifanalyses show that elevation 703 ft would not be exceeded at SQN, the SQNcontrol room supervision is immediately notified that the potential for site floodingno longer exists. SQN control room supervision is directed by AOP-N.03 toimmediately proceed to a Stage I Flood Warning if communications are notestablished with the River Forecast Center staff within five hours of receiving anEarly Warning. SQN control room supervision is directed by AOP-N.03 to continueonto Stage II Flood Warning shutdown procedures within ten hours of beginningStage I Flood Warning preparations unless the River Forecast Center staff notifiesSQN control room supervision that the potential for site flooding no longer exists.e. If necessary, a Stage I Flood Warning is declared and communicated to SQNcontrol room supervision at least 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br /> before the flood elevation at the sitecould exceed elevation 703 ft.f. If necessary, a Stage II Flood Warning is declared and communicated to SQNcontrol room supervision at least 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> before the flood elevation at the sitecould exceed elevation 703 ft.g. SQN control room supervision is immediately notified and flood warnings arerescinded when the potential for site flooding no longer exists.2. For major flood producing storms (area average rainfall of six inches in 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> ormore above Chattanooga, Tennessee), with no critical dam failure or dam safetyemergencies, the River Forecast Center staff would be required to take the followingactions:a. The REOC is activated and operated until the condition no longer exists.b. An Early Warning is immediately issued to SQN control room supervision when theREOC is activated for flood conditions and/or for a dam safety emergency involvinga SQN-critical dam.Page 16 of 29 ENCLOSUREIRESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)c. Communications are maintained with SQN control room supervision on at leastthree-hour intervals (or more frequently, if needed).d. SQN control room supervision is notified of conditions (rainfall and floodpredictions) and that the REOC has been activated.e. If necessary, a Stage I Flood Warning is declared and communicated to SQNcontrol room supervision when flood level at the site, based on rainfall on theground, is forecast to reach the appropriate threshold flood warning levels for theseason of the year. SQN control room supervision is directed by AOP-N.03 toimmediately proceed to a Stage I Flood Warning if communications are notestablished with the River Forecast Center staff within five hours of receiving anEarly Warning. SQN control room supervision is directed by AOP-N.03 to continueonto Stage II Flood Warning shutdown procedures within ten hours of beginningStage I Flood Warning preparations unless the River Forecast Center staff notifiesSQN control room supervision that the potential for site flooding no longer exists.f. If necessary, a Stage II Flood Warning is declared and communicated to SQNcontrol room supervision 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> or more from the time when flood level at thesite, based on rainfall on the ground, is forecast to reach elevation 703 ft.g. The flooding is assessed on an on-going basis to ensure that a minimum 27 hournotice for Stage I Flood Warning and a minimum 17 hour1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> notice for Stage II FloodWarning are maintained.h. SQN control room supervision is immediately notified and flood warnings arerescinded when the potential for site flooding no longer exists.3. For times when either SQN unit is in Mode 5 (Cold Shutdown) or Mode 6 (Refueling)as defined in the plant Technical Specifications (usually during refueling or majormaintenance), SQN control room supervision requires extra warning regarding floodconditions. In Mode 5 or 6, extra time would be needed to establish open modecooling. To ensure sufficient awareness, SQN management and the River ForecastCenter staff discuss dates for refueling or major maintenance in advance of scheduledoutages, and communicate at least once per day during this condition to notify theRiver Forecast Center staff of plant outage configuration and expected time tocomplete outage. SQN management notifies the River Forecast Center staff when thisplant configuration is no longer applicable.During refueling or major maintenance, the River Forecast Center staff provides SQNcontrol room supervision with an assessment of forecasted river elevations based bothon rainfall on the ground and "maximum" rain forecast. As directed by the TVA RiverScheduling Notification Directory, the River Forecast Center forecast indicates whetheror not the expected river elevation will exceed elevation 703 ft within the next 99 hour0.00115 days <br />0.0275 hours <br />1.636905e-4 weeks <br />3.76695e-5 months <br />sto provide additional warning time regarding predicted flood conditions. If heavy raindevelops or is forecast, the River Forecast Center staff notifies SQN control roomsupervision of any decrease of the 99 hour0.00115 days <br />0.0275 hours <br />1.636905e-4 weeks <br />3.76695e-5 months <br /> flood warning time forecast if applicable.Page 17 of 29 ENCLOSURE1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)After the River Forecast Center staff has determined that a Stage I Flood Warning isrequired then the actions of AOP-N.03 are implemented. AOP-N.03 requires the SQNcontrol room supervisors to evaluate Emergency Plan Implementing Procedure EPIP-1,"Emergency Plan Classification Matrix," to determine the emergency action levelrequirements. EPIP-1 requires declaration of a Notification of Unusual Event wheneverriver reservoir level is at Stage I Flood Warning as reported by the River Forecast Centerstaff, and declaration of an Alert whenever river reservoir level is at Stage II Flood Warningas reported by the River Forecast Center staff. Therefore, the emergency action levelsreflect actual Stage I and Stage II Flood Warning declarations by the River ForecastCenter staff regardless of the actual flood elevations existing at the SQN site.13.0 AHPB RAI Question 13On page 32 of 39 in Enclosure 1 of the LAR, the assumptions for initial conditions in theflood plan include plants at 100 percent power. Are there any plant modes other than 100percent power that could complicate planned responses, demand additional staffing, or-extend response times? For example, would there be any effect on the flood plan if SQN,Unit 1 was in the middle of refueling and SQN, Unit 2 was at some intermediate powerlevel? Are the timing estimates for Stage I and Stage II actions the same regardless of theage of the core (i.e., rapid shutdown will take the same amount of time whether the plant'score is at end-of-life or is a fresh full-core refueling)?13.1 TVA Response -AHPB RAI Question 13In accordance with AOP-N.03, after initial flood mode preparation actions that are notdependent on the mode of operation for each of the two units, subsequent actions aretaken on a per unit basis depending on initial plant operating Mode as defined by the SQNTechnical Specifications. For operation in Modes 1 or 2 at any power level, upon issuanceof a Stage I Flood Warning, actions are taken to initiate plant shutdown to Mode 3 or 4 inaccordance with AOP-C.03, or general operating instruction 0-GO-6, "Power Reductionfrom 30% Reactor Power to Hot Standby." When the unit is in Mode 3, Reactor CoolantSystem (RCS) cooldown is completed to Mode 4 in accordance with general operatinginstruction 0-GO-7, "Unit Shutdown From Hot Standby to Cold Shutdown," or EmergencyOperating Procedure ES-0.2, "Natural Circulation Cooldown." The requirements forshutdown are described in SQN Technical Requirements Manual (TRM) Section 3.7.6,which requires the reactor to be in at least Hot Standby (Mode 3) within six hours with aShutdown Margin of at least 5% delta k/k and Tavg less than or equal to 350°F (Mode 4)within the following four hours upon notification of a Stage I Flood Warning from the RiverForecast Center staff, under the direction of the River Scheduling Lead Engineer. If theunit is initially in Modes 1, 2, 3, or 4, AOP-N.03 directs completion of Stage I FloodWarning preparation including shutdown to Mode 4 within 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> of a Stage I FloodWarning. Stage II Flood Warning preparations then include actions to maintain the unit inMode 4 to preserve use of the steam generators for core cooling, and these actions canbe accomplished within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of receipt of the initial warning that a flood above plantgrade is possible. An additional three hours are available for contingency margin beforewave runup from the rising flood might enter the buildings.AOP-N.03 also provides separate unit-specific actions for any unit in Mode 5 (ColdShutdown), Mode 6 (Refueling), or if the core is empty. In Mode 5 or 6, extra time wouldPage 18 of 29 ENCLOSURE1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)be needed to establish open mode cooling. Therefore, Stage II Flood Warning preparationtimes are longer if the unit is initially in Mode 5 or 6, but the actions can be performedindependently regardless of initial plant mode of the other unit.Although there are different actions depending upon the initial plant operating condition,the instructions provided by AOP-N.03 ensure that the Stage I Flood Warning actions foreach unit independently can be completed within the required 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />. Under thespecific example for SQN Unit 1 being in the middle of refueling (Mode 6) and SQN Unit 2at some intermediate power level (i.e., in Modes 1 or 2), the time for Unit 1 to completeflood mode preparations would be longer than the time for Unit 2. This is the result of thelarger number of actions required by AOP-N.03 for a unit initially in Mode 6, because theRCS and core may be in various alternative configurations initially, and transition to openmode cooling or removing fuel from the core would be required. The actual time to reachMode 4 during a Stage I Flood Warning is greater for a unit at 100% power than at apower level less than 100%, because of the difference in the amount of time spent inprocedures 0-GO-7 or AOP-C.03. However, the required 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> for completing Stage Iflood mode preparations is met at any initial power level. The performance time forAOP-C.03 is the same regardless of the amount of time the unit has been at power.14.0 AHPB RAI Question 14On page 14 of 39 of the LAR, it is stated that low water levels at the plant intakes could beexperienced in as little as 51 hours5.902778e-4 days <br />0.0142 hours <br />8.43254e-5 weeks <br />1.94055e-5 months <br /> if the downstream dam fails during a drought. Is therea plan or procedure in place that addresses the loss of heat sink? What alerts areavailable to cue the operators that a loss of heat sink is underway? How long after thefailure of the dam would operators be aware that a loss of heat sink may be underway?14.1 TVA Response -AHPB RAI Question 14AOP-N.04, "Break of Downstream Dam," addresses the loss of the downstream dam.Because Chickamauga Dam flows and hydroelectric power production are controlled byTVA, notification of a failure of Chickamauga Dam is received from the TVA TransmissionOperator. SQN control room supervision verifies failure of Chickamauga Dam with eitherthe TVA Hydro Dispatch Center or TVA Transmission Operator using specified phonenumbers. In addition, requirements for River Forecast Center staff, under the direction ofthe River Scheduling Lead Engineer, to immediately notify SQN control room supervisionof the failure of Chickamauga Dam, are addressed by the TVA River SchedulingNotification Directory, a desktop instruction that is maintained by TVA River Scheduling foruse by the River Forecast Center staff during emergencies. For SQN, a primary numberand an alternate number are provided to ensure that the SQN control room supervision isnotified of predicted or actual failure of Chickamauga Dam. Therefore, because of thedifferent and independent methods of notification, and capability for SON control roomsupervision to verify failure of Chickamauga Dam from different and independent sources,awareness of the failure of the dam can be reasonably assured by the SQN control roomsupervision within minutes.In the event of loss of Chickamauga Dam, the TVA River Scheduling Notification Directoryrequires TVA River Scheduling to provide an instantaneous minimum flow (from theupstream Watts Bar Dam) of 14,000 cfs commencing no later than 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after damPage 19 of 29 ENCLOSURE 1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)failure for up to 100 days to maintain minimum intake elevation at SQN. This meets therequirements proposed in the SQN LAR for maintaining minimum water level at SQN andthe minimum flow requirement at the Essential Raw Cooling Water (ERCW) intake.15.0 AHPB RAI Question 15The Hydrologic Basis for Warning System section on page 17 of Enclosure 1 of the LARdiscusses Stage I and Stage II and the times associated with each stage. How was thetime determined for each stage (10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> for Stage I and 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> for Stage II)? Ifdetermined by the walkdown, was a full complement of required personnel involved?Clarify how this integrates with the emergency plan (e.g., whether the emergency plancall-in methods will provide enough people to implement the flood plan(s) in enough time).15.1 TVA Response -AHPB RAI Question 15The total preparation time for both Stage I and Stage II Flood Warning actions areevaluated in the updated hydrologic analysis to ensure margin exists for both the limitingrainfall-induced PMF event and for the limiting seismically-induced dam failure flood event.The steps needed to prepare the plant for flood mode operation can be accomplishedwithin 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of receipt of the initial warning that a flood above plant grade is possible.An additional three hours are available for contingency margin before wave runup from therising flood might enter the buildings. The total preparation time is divided into two stages:Stage I, a minimum of 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> long and Stage II, a minimum of 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> long (whichincludes a three hour additional margin), so that unnecessary economic consequencescan be avoided, while providing adequate time for preparing for operation in the floodmode. Stage I allows preparation steps causing minimal economic consequences to besustained but postpones major economic damage to the plant until a Stage II warning thatpredicts a likely forthcoming flood above plant grade. If the flood does not develop beyonda Stage I warning, major economic damage is avoided.As described in the SQN LAR, steps needed to prepare the plant for flood mode operationcan be accomplished within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of receipt of the initial warning that a flood aboveplant grade is possible. An additional three hours are available for contingency marginbefore wave runup from the rising flood might enter the buildings. For rainfall-inducedPMF events, an additional four hours is assumed for communication and forecastingcomputations by the River Forecast Center organization to translate rain on the ground toriver elevations at the plant. Hence, the warning time plan provides for a minimum of31 hours from arrival of rainfall on the ground until elevation 703.0 ft could be reached forrainfall-induced PMF events. In the updated hydrologic analysis, the minimum 31 hour3.587963e-4 days <br />0.00861 hours <br />5.125661e-5 weeks <br />1.17955e-5 months <br />sfor preparation time is assured to be available for rainfall-induced PMF events byestablishing revised threshold flood warning levels. These threshold flood warning levelsensure that the actual warning times will be at least 31 hours3.587963e-4 days <br />0.00861 hours <br />5.125661e-5 weeks <br />1.17955e-5 months <br /> total for the PMF level to bereached for the most-limiting rainfall-induced PMF event, and for any event with differentrainfall amounts or for different time periods the actual total warning time will be longer.For the most-limiting flood from a postulated seismic failure of upstream dams, the limitingtime interval for completing both Stage I and Stage II Flood Warning preparationsnon-concurrently is 32 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br />. The other postulated dam failure events will result in longerPage 20 of 29 ENCLOSURE1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)total warning times. Therefore, for seismically-induced dam failure flood events, anadditional hour of margin in the flood warning time exists for the limiting event.As previously discussed in the response to AHPB Question 12, once the River ForecastCenter staff has determined that a Stage I Flood Warning is required then the actions ofAOP-N.03 are implemented. AOP-N.03 requires the SQN control room supervisors toevaluate EPIP-1, "Emergency Plan Classification Matrix," to determine the emergencyaction level requirements. EPIP-1 requires declaration of a Notification of Unusual Eventwhenever river reservoir level is at Stage I Flood Warning as reported by the RiverForecast Center staff, and an Alert whenever river reservoir level is at Stage II FloodWarning as reported by the River Forecast Center staff. As previously discussed in theresponse to AHPB RAI Question 5, a reasonable simulation was performed of the floodresponse AOP-N.03. Based on the reasonable simulation, there is assurance that therequired personnel are available and capable of implementing the Stage I and Stage IIFlood Warning preparations within the required times.16.0 AHPB RAI Question 16The licensee states on page 27 of 39 of Enclosure 1 of the LAR, "As a part of TVA RO'sflood control responsibilities, forecast and warning procedures have been established thatreflect the updated hydrologic analyses." As part of the configuration control process forthese procedures, is the SQN site included in the review and approval of technicalchanges?16.1 TVA Response -AHPB RAI Question 16TVA Intergroup Agreement TVA-IGA-09.002, "TVA Intergroup Agreement (IGA) NuclearPower Group and River Operations," applies to personnel assigned to either TVA NuclearPower Group or TVA River Operations. TVA River Operations works directly under theTVA Nuclear Quality Assurance Plan for nuclear quality-related or safety-related work inlieu of developing and maintaining a Nuclear Quality Assurance program in compliancewith 10 CFR 50 Appendix B.As described in TVA-IGA-09.002, the TVA Nuclear Power Group performs evaluations ofthe effect to the existing nuclear plant design basis flood analysis as a result of potentialand existing river system operations and configuration changes. This is accomplished byrequiring WVA River Operations to complete Attachment 1, Tennessee River SystemConfiguration Change Checklist, at six month intervals (+/- 1 month). The purpose of thischecklist is to provide early identification of changes in the configuration or operation of theTennessee River Basin dam and river system that could potentially impact the TVANuclear Plants DBF analyses. This checklist applies to TVA dam projects at andupstream of Wilson Dam on the Tennessee River and upstream tributary dam projects.After completion, the Attachment 1 checklist is forwarded to the TVA Nuclear Power GroupVice President of Nuclear Engineering. The TVA Intergroup Agreement also requires TVARiver Operations to identify potential river system changes affecting the Attachment 1checklist attributes and river system scope as early as possible (conceptual design stageor earlier). These actions ensure an adequate configuration control process for changesunder the authority of TVA River Operations as they affect TVA Nuclear Power Groupdesign and operations activities.Page 21 of 29 ENCLOSUREIRESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)17.0 AHPB RAI Question 17The "shortest warning time" is discussed in several sections of the application, but notquantified. What were the shortest possible warning times analyzed for Stage I andStage II warnings? Begin at the time the operators in the SQN control rooms receive thewarning.17.1 TVA Response -AHPB RAI Question 17The updated hydrologic analysis ensures margin exists for completing both the Stage Iand Stage II Flood Warning preparations for both the limiting rainfall-induced PMF eventand for the limiting seismically-induced dam failure flood event as discussed in the SONLAR. The "shortest warning time" for the limiting rainfall-induced PMF event is 31 hour3.587963e-4 days <br />0.00861 hours <br />5.125661e-5 weeks <br />1.17955e-5 months <br />sfrom the critical rainfall occurring until elevation 703 ft is observed at SQN (10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> forStage 1, 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> for Stage II, and four hours for additional margin). The "shortest warningtime" for the limiting seismically-induced dam failure flood event is 32 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br /> from thefailure of the failure of the dams until the flood wave reaches elevation 703 ft at SON. Themethods used to evaluate these two scenarios are described in SON UFSARSubsection 2.4.14, and in Enclosure 1 of the SON LAR on pages 25 through 30 for largerainfall floods, and pages 30 through 32 for seismically-induced dam failure floods, asfurther described below.For large rainfall floods, the warning time is assured by declaring Stage I and Stage IIFlood Warnings based on rainfall on the ground, and not based upon actual riverelevations at SON. The analysis described in SON UFSAR Subsection 2.4.14 consists ofevaluating nine hypothetical storms ranging from slightly more than five inches (equivalentto the largest flood event since regulation of flood-control on the Tennessee River valleyby the use of TVA dams) up to probable maximum precipitation (PMP) events, andenveloped potentially critical areal, seasonal variations and time distribution of rainfall.The warning time is based on those storm situations which resulted in the shortest timeinterval between watershed rainfall and reaching elevation 703.0 ft at SQN (2.0 ft belowplant grade). The shortest warning time scenario for the winter was determined to beproduced by the March 21,400 square mile downstream centered PMP with the heavyrainfall on the last day. The shortest warning time for the summer flood was produced bythe 7,980 square mile June Bulls Gap centered PMP with the heavy rainfall on the lastday. For each of these limiting scenarios, threshold flood warning levels were determinedin the analysis as shown in Table 2 of Enclosure 1 of the SQN LAR. The River ForecastCenter staff issues a Stage I Flood Warning to SQN control room supervision when floodlevel at the site, based on rainfall on the ground, is forecast to reach the appropriatethreshold flood warning levels for the season of the year (i.e., those levels shown inTable 2 of Enclosure 1 of the SQN LAR). For any storm that results in less rainfall on theground than the two shortest warning time storms, the actual time from start of the rainfallevent to reaching Stage I Flood Warning threshold warning level, between reachingStage I and Stage II Flood Warning threshold warning levels, and between reachingStage II Flood Warning threshold level and actually exceeding actual plant grade at thesite, would be greater. Therefore, the analysis verifies that margin exists for a significantincrease in forecasted river elevations based on actual rainfall on the ground before aStage I and Stage II Flood Warning would be required to be declared. This ensures thatPage 22 of 29 ENCLOSURE1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)the required flood warning time of 31 hours3.587963e-4 days <br />0.00861 hours <br />5.125661e-5 weeks <br />1.17955e-5 months <br /> (10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> for Stage 1, 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> for Stage II,and four hours for additional margin) is available for the limiting rainfall-induced PMFevent.For seismically-induced dam failure floods, the warning time is based upon an analysis ofpossible dam failure combinations resulting from a seismic event with initial river levelssignificantly above the maximum operating levels. This includes five possiblecombinations of dam failures and initial river level conditions as described in SQN UFSARSubsection 2.4.14. From this analysis, the flood wave travel times are determined toensure there is adequate time between the seismically-induced dam failures and declaringStage I Flood Warning, and between performing the 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br /> of Stage I and Stage IIFlood Warning preparations and actually exceeding elevation 703 ft at SQN. The resultsof this analysis are shown in Table 3 of Enclosure 1 of the SQN LAR, and demonstratethat the limiting combination results in a flood wave travel time of 32 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br /> between theseismic dam failures and exceeding elevation 703 ft at SQN. This provides sufficient timefor implementing the Stage I and Stage II Flood Warning preparations, ensuring that therequired flood warning time of 31 hours3.587963e-4 days <br />0.00861 hours <br />5.125661e-5 weeks <br />1.17955e-5 months <br /> (10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> for Stage I, 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> for Stage II, andfour hours for additional margin) is available for the limiting seismically-induced dam failureflood event.18.0 AHPB RAI Question 18In the UFSAR, Section 2.4.10, paragraph 3, it is stated, "Warning of seismic failure of keyupstream dams will be available at the plant approximately 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br /> before a resultingflood surge would reach plant grade." What is the basis for this statement?18.1 TVA Response -AHPB RAI Question 18As discussed in the response to AHPB RAI Question 17, the limiting possible dam failurecombination resulting from a seismic event with initial river levels significantly above themaximum operating levels results in a flood wave travel time of 32 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br /> between theseismic dam failure and exceeding elevation 703 ft at SQN. Therefore, the 27 hour3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br />srequired for implementing Stage I and Stage II Flood Warning preparations are assured.19.0 AHPB RAI Question 19If off-site power is lost early in Stage I, what are the effects on Stage I timing, staffing,personnel actions, action sequences, warnings, and emergency action level notifications?19.1 TVA Response -AHPB RAI Question 19As described in the response to AHPB RAI Question 12, once the River Forecast Centerstaff has determined that a Stage I Flood Warning is required then the actions ofAOP-N.03 are implemented. AOP-N.03 requires the SQN control room supervisors toevaluate EPIP-1, "Emergency Plan Classification Matrix," to determine the emergencyaction level requirements. EPIP-1 requires declaration of a Notification of Unusual Eventwhenever river reservoir level is at Stage I Flood Warning as reported by the RiverForecast Center, and an Alert whenever river reservoir level is at Stage II Flood Warningas reported by the River Forecast Center staff. Once entry is made into the actionsPage 23 of 29 ENCLOSURE 1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)required by the Emergency Plan, contingencies are provided in the Emergency PlanImplementing Procedures to address the possibility of the loss of offsite power concurrentwith design basis accidents and events, including external flooding. These proceduresensure that staffing, communications, and availability of required resources, are availablefor potential emergency situations.AOP-N.03 requires monitoring of off-site power availability during external flooding events.If off-site power is lost, then Emergency Operating Procedures exist to place the units in asafe shutdown condition that is required by AOP-N.03. If either unit has not been placedin safe shutdown prior to external flooding exceeding plant grade, and the requirements ofEmergency Operating Procedures for natural circulation cooldown (ES-0.2, ES-0.3, orES-0.4) are in progress as a result of loss of off-site power, the additional actions requiredbecause of an external flooding event are addressed in AOP-N.03. Therefore, thecombination of AOP-N.03 and the Emergency Operating Procedures ensure that the unitis maintained in a safe condition throughout the flooding event, even if off-site power islost.If offsite power has been lost, the Reactor Coolant System (RCS) cooldown would beperformed using natural circulation. The Emergency Operating Procedure for naturalcirculation cooldown (ES-0.2) directs limiting cooldown rate to 50°F/hour, rather than theTechnical Specification limit of 100°F/hr. Since RCS cooldown is required from normaloperating temperature (5470F) to approximately 3200F, the time to complete the cooldownwould be extended from 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> to approximately five hours. As previously discussed inthe response to AHPB RAI Question 5, a reasonable simulation was performed forAOP-N.03. The time assumed in the simulation (300 minutes) encompasses use ofnatural circulation. Additionally, a loss of off-site power would result in loss of normal plantlighting, requiring use of portable lighting for flooding actions outside the Main ControlRoom and shutdown board room area. However, this portable lighting is available duringemergency conditions.Based on the above, the loss of off-site power during Stage I or Stage II Flood Warningpreparations would not prevent completion of any required flood preparation actions withinthe required time limit.Page 24 of 29 ENCLOSURE 1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)20.0 AHPB RAI Question 20On page 9 of 14 of Enclosure 2 of the LAR, the licensee states, 'The updated DBF[design-basis flood] analysis for SQN indicated that some upstream dam earthembankments could be overtopped during the PMF. Four dams were identified as havingembankments that could be overtopped during the PMF: Cherokee; Fort Loudoun; Tellico;and Watts Bar." As a temporary measure, HESCO Concertainer units have been installedat each of the four dams. What organization was responsible for installing the HESCOConcertainers? Were they installed under an NRC-approved quality assurance programor equivalent, using controlled drawings, procedures, and documents? What barriers tohuman error were used (e.g., pre-job brief, independent verification, self-checking)?20.1 TVA Response -AHPB RAI Question 20The HESCO modular flood barriers were installed by the dam Asset Owner, which is TVARiver Operations, in accordance with processes and procedures controlled by thatorganization. These processes and procedures include design controls used by TVARiver Operations for configuration control of each of the dams for which TVA is the AssetOwner, and address implementation of design changes to the structural portions of thedams including the concrete dam sections and dam earthen embankments, including theHESCO modular flood barriers that are installed on top of the selected dam earthenembankments as discussed in the SQN LAR.The configuration control of these four dams is both controlled and regulated by TVA RiverOperations, and does not fall under any NRC regulation. Therefore, the TVA RiverOperations processes and procedures that were used in the engineering, construction,and maintenance of the HESCO modular flood barriers are in compliance with TVA RiverOperations quality standards. These processes and procedures are not required tocomply with 10 CFR 50 Appendix B Quality Assurance requirements, and the qualityrequirements met by the TVA River Operations processes and procedures are notNRC-approved, and do not require NRC approval. However, the quality standards usedrequire the use of controlled drawings, procedures, and documents for implementingdesign changes including the installation of the HESCO modular flood barriers. Inaddition, periodic inspections are conducted, and maintenance performed, in accordancewith TVA River Operations procedures to ensure the HESCO modular flood barriers wereproperly installed and remain in acceptable condition.To ensure that the HESCO modular flood barriers are being maintained in an acceptablecondition, the TVA Nuclear Power Group performs monthly inspections in accordance withprocedures prepared and approved in accordance with the NRC-approved TVA QualityAssurance Program. These inspections verify the following:a. Ensure the temporary HESCO flood barriers remain in place and are not structurallydegraded as specified by the manufacturer's written specifications andrecommendations;b. Verify the inventory and staging of the material required to fill the gaps that exist; andPage 25 of 29 ENCLOSURE IRESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)c. Ensure that adequate physical security (e.g., fences and locks) is provided for thestaged material against theft.These inspections will continue until the permanent modifications are implemented toprevent overtopping the Cherokee, Fort Loudoun, Tellico, and Watts Bar dams, previouslycommitted to be complete by October 2015. The commitments for the inspections andpermanent modifications were provided in the letter from TVA to the NRC, "CommitmentsRelated to Updated Hydrologic Analysis Results for Sequoyah Nuclear Plant, Units 1and 2, and Watts Bar Nuclear Plant, Unit 1,," dated June 13, 2012 (ADAMS AccessionNo. ML12171A053), and confirmed by the NRC in the letter to TVA, "Confirmatory ActionLetter -Watts Bar Nuclear Plant, Unit 1, and Sequoyah Nuclear Plant, Units 1 and 2,Commitments to Address External Flooding Concerns (TAC Nos. ME8805, ME8806, andME8807)," dated June 25, 2012 (ADAMS Accession No. ML12165A527).21.0 AHPB RAI Question 21On page 9 of 14 of Enclosure 2 of the LAR, the licensee states, "The maintenance of thetemporary flood barriers and closure of openings during emergency events is a RiverOperations (RO) -Asset Owner (AO) responsibility, as defined by Dam Safety procedureRO-SPP-27.0." What is the sequence-of-events regarding the RO's closure of openingsduring emergency events in relationship to the site flood plan? What alerts the RO toclose the openings and how long will it take? What credible errors are associated with theHESCO temporary barriers or their closure during a flood event?21.1 TVA Response -AHPB RAI Question 21Detailed plans for closure of the public access (PA) gaps in the HESCO modular floodbarriers at Cherokee Dam, Fort Loudoun Dam, Tellico Dam, and Watts Bar Dam (includingtriggering hydrologic conditions) are fully described in TVA River Operations CherokeeDam, Fort Loudoun/Tellico Dams, and Watts Bar Dam Emergency Action Plans (EAPs).As described in the EAPs, the dam Asset Owner (TVA River Operations for these fourdams) is notified by River Forecast Center staff when triggering headwater elevation isforecast for each dam (based on observed rainfall). Construction crews begin mobilizingto stage equipment and personnel at the sites to be prepared for closure of the PA gaps inthe HESCO modular flood barriers. The triggering headwater elevations are as follows:Dam Elevation (ft)Watts Bar 747Tellico 816Fort Loudoun 816Cherokee 1075Page 26 of 29 ENCLOSURE 1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)A second notification is made to the dam Asset Owner by the River Forecast Center staffwhen a second, higher triggering headwater elevation is forecast for each dam (based onobserved rainfall). The construction crews then proceed to close the PA gaps in theHESCO modular flood barriers in accordance with the EAPs. The second, highertriggering headwater elevations are as follows:Dam Elevation (ft)Watts Bar 748Tellico 817Fort Loudoun 817Cherokee 1076An evaluation of the ability to close the PA gaps in accordance with the EAPs is describedin TVA letter to NRC, "Potential for Breaches of HESCO Modular Flood Barriers andEarthen Embankments Affecting the Updated Hydrologic Analysis Results forSequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Unit 1," datedJanuary 18, 2013 (ADAMS Accession No. ML13025A262). Additional details can befound in this previous submittal, and the following discussions are based on thisevaluation.Reasonable simulations were performed to validate representative portions of the TVARiver Operations Cherokee Dam, Fort Loudoun/Tellico Dams, and Watts Bar Dam EAPson December 11, 2012. During these simulations, required personnel were mobilized,reported, and closed selected representative PA gaps in the HESCO modular floodbarriers prior to the calculated time that headwater elevations would reach the base of theHESCO modular flood barriers at each site during an actual PMF event. Additionally, EAPspecified equipment was mobilized, delivered, and utilized in the required time.Following the guidance provided in the EAPs, a timed reasonable simulation wasperformed in order to verify that time dependent activities were achievable and requiredresources were available. This reasonable simulation included prediction of criticalheadwater elevations by River Forecast Center staff, notification of required personnel,mobilization of required personnel and equipment at the affected dams, and constructionof HESCO modular flood barriers for selected PA gap closures (Watts Bar Dam PA-3 andportion of Fort Loudoun Dam PA-2).The specific steps of the respective EAPs simulated, including initial and followupnotifications and communications between TVA and contractor organizations and actualconstruction of the HESCO modular flood barriers by the contractor, are discussed in theprevious submittal. The observations and conclusions from these reasonable simulationsinclude the following:Required resources (personnel, equipment, and material) as described in each site'sEAP are available, and were determined to be sufficient to close the PA gaps. Theseresources were verified through the reasonable simulations and previous inventory ofmaterials. Additionally, the ability of the EAPs to be effectively implemented by TVAand contractors was validated for the specific simulations performed.Page 27 of 29 ENCLOSURE 1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)* The PA gaps are accessible to varying degrees to perform the required actions, andaccessibility was deemed acceptable. It should be noted that some gap locationsprovide the opportunity to use multiple pieces of equipment to close a single gap.* High winds, heavy rains, and lightning could delay closure of the PA gaps in theHESCO modular flood barriers. However, the simulation verified that there is sufficientmargin available to account for these delays.* The River Forecast Center river forecasts routinely incorporate predicted rainfall, andcan accurately predict river elevations that would occur if the rainfall event happenedas forecast over the next 10 days. There are various postulated 9-day rain eventswhich result in the need for the HESCO modular flood barriers to prevent damembankment overtopping. The trigger point for notification of HESCO modular floodbarrier construction crews and equipment is based on predicted headwater elevationsat each dam. Therefore, it would be possible for the River Forecast Center staff toforecast the rain events and predict the trigger headwater elevations up to days inadvance. Thus, prior to routes becoming impassible, notifications could be made tomobilize required equipment and personnel. Additionally, there are multiple roadwaysbetween major metropolitan areas and respective sites to transport personnel andequipment. This provides redundant roadways to access each site if one roadwaywere to become impassible. Therefore, it is concluded that mobilization of personneland equipment would not be adversely restricted.Based on the above discussion, it is concluded that any credible errors that could beencountered in closing the PA gaps in the HESCO modular flood barriers are adequatelyaddressed in the EAPs and by the availability of resources including personnel,equipment, and material. The ability to implement procedures to close the gaps left forpublic access through the HESCO modular flood barriers (PA gaps) ensures theeffectiveness of the modular flood barriers during a PMF event. A reasonable simulationverified that the required resources (personnel, equipment, and material) as described ineach site's EAP are available, and were determined to be sufficient to close the PA gaps.These resources were verified through the reasonable simulations and previous inventoryof materials. Additionally, the ability of the EAPs to be effectively implemented by TVAand contractors was validated for the specific simulations performed.22.0 AHPB RAI Question 22Will site personnel need to know the actual flood levels to perform any required actions inthe flood plan or shutdown procedures? If yes, how will flood level be determined?22.1 TVA Response -AHPB RAI Question 22AOP-N.03 controls the overall timing and sequence of implementing actions for floodmode preparations and operations, and utilizes implementing work orders, generaloperating instructions, emergency operating instructions, flood preparation maintenanceinstructions, and other AOPs to complete the required actions by the applicable SQN siteorganizations. These procedures do not require the SQN control room supervision toknow the actual flood levels in order to be successfully performed. In AOP-N.03, there isPage 28 of 29I ENCLOSURE1RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)one action during Stage II Flood Warning preparations that directs breaching open variousdoors to allow free flooding of lower elevations of the Control Building and AuxiliaryBuilding when the water level rises above elevation 705 ft. This elevation is approximatelyequal to plant grade, so operators could reasonably determine when this action is neededwithout instrumentation or other accurate methods of measuring elevation. However,there is detailed flood level information including forecast levels from the River ForecastCenter that can be made available to the SQN control room supervision upon request.Page 29 of 29 ENCLOSURE2TENNESSEE VALLEY AUTHORITYSEQUOYAH NUCLEAR PLANTUNITS I AND 2RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)

Subject:

Application to Revise Sequoyah Nuclear Plant Units I and 2 Updated FinalSafety Analysis Report Regarding Changes to Hydrologic Analysis,(SQN-TS-12-02)1.0 SBPB RAI Question 1The revised DBF level at the DG building exceeds the elevation of the DG building floor.As a temporary measure, a berm of sandbags will be constructed around the DG buildingentrances. The application states that these sandbags are staged on-site.Describe how the availability of sandbags in sufficient quantity will be ensured whenrequired (i.e., inclusion in station procedures, etc.).1.1 TVA Response -SBPB RAI Question 1The installation of permanent plant modifications to protect the Diesel Generator Buildingentrances from a DBF, including future installation of permanent engineered flood barriers,has replaced the use of sandbag berms. These plant modifications and the requiredactions for installation of permanent engineered flood barriers are described in theresponse to SBPB RAI Question 2.2.0 SBPB RAI Question 2The LAR states that the licensee will install permanent plant modifications to provideadequate flooding protection with respect to the DBF level for the DG building, byMarch 31, 2013. This is earlier than the requested review date of this LAR(August 10, 2013), but information on the permanent modification to the DG building is notprovided.Describe the design of these permanent plant modifications and how they will provideadequate flooding protection for the DG building. The response should include anyproposed UFSAR text changes reflecting flooding protection of the DG building.2.1 TVA Response -SBPB RAI Question 2As stated in the SQN LAR, the DBF including wind wave run up during the PMF event iselevation 723.2 ft, which is 1.2 ft above the Diesel Generator Building operating floorelevation of 722.0 ft. Therefore, TVA has installed plant modifications to provide floodprotection with respect to this DBF level for the SQN Diesel Generator Building at severallocations. Modifications include installation of flood protection barriers in the DieselGenerator Building at elevation 722 ft for equipment doors (D1-D4), personnel accessPage 1 of 13 ENCLOSURE2RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)door (D5) and emergency doors (D15-D18), capping of the 3/4-inch waste line from theToilet Room, and extension to the four external fuel fill ports for the seven day oil storagetanks.The flood protection barriers for the equipment doors (D1-D4) are fabricated on-site, andconsist of a steel plate attached to a framing angle that is welded to the inside of the doorframes, as shown in Attachment 1. The equipment numbers for these flood protectionbarriers are SQN BRR-634-DO01 through SQN BRR-634-D004, respectively. Thesebarriers ensure flood protection up to two feet above the DBF level. These flood barriersare installed at all times, except when access is needed for major maintenance.Therefore, no action is necessary during a flood event to install these barriers. Thebarriers may be removed as needed when access is required to perform majormaintenance. In such instances where the barrier might be temporarily removed, the floodbarrier is placed in a storage location. During flood mode preparations, an action isrequired to retrieve the barrier and remount it to the framing angle. Lifting lugs mounted tothe concrete around the door frames are provided to assist in installation and removal.The flood protection barrier for the personnel access door (D5) consists of an L-shapedreinforced concrete berm that is an extension of the permanent structure, and is locatedinside the building between doors D5 and D6. The flood protection barriers for theemergency doors (D1 5-D18) consist of reinforced concrete berms that are extensions ofthe permanent structure, and are located in the corridors outside of the emergency doors.These barriers are shown in Attachment 2. These barriers ensure flood protection up tothe DBF level.Capping of the 3/4-inch waste line from the Toilet Room was previously not required,because the plumbing drains were located above the previous DBF level. Capping theline provides flood protection above the DBF level, as shown in Attachment 3.Extension to the four external fuel fill ports for the seven day oil storage tanks waspreviously not required, because the ports although capped were located above theprevious DBF level. Extension to the four external fuel fill ports to elevation 725.25 ftprovides flood protection up to two feet above the DBF level allowing sufficient margin toremove the cap and refill the tanks during a PMF event, as shown in Attachment 4.SQN UFSAR Subsection 2.4.2.2, was revised in the SQN LAR to include the followingdiscussion:"Wind wave run up during the PMF at the Diesel Generator Building would reachelevation 723.2 ft which is 1.2 ft above the operating floor. Consequently, windwave run up will impair the safety functions of the Diesel Generator Building. Theaccesses and penetrations below this elevation in the Diesel Generator Buildingare designed and constructed to minimize leakage into the building. Redundantsump pumps are provided within the building to remove minor leakage."Because of the level of detail required in the SQN UFSAR, and because thesemodifications meet the flooding protection basic design requirement in the SQN UFSARfor the Diesel Generator Building as stated above, there are no other changes to the SQNUFSAR required.Page 2 of 13 ENCLOSURE2RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)The above described plant modifications were complete on March 29, 2013. Additionalplant modifications are planned to replace the flood protection barriers (reinforcedconcrete berms) for the personnel access door (D5) and emergency doors (D1 5-D1 8) withengineered flood barriers, as shown in Attachment 5. This will allow easier personnel andequipment access through these doors while ensuring adequate flood protection. Theseengineered flood barriers will ensure flood protection up to two feet above the DBF level.The flood barriers that are being identified for installation at doors D5, D15, D16, D17, andD18, are manufactured and qualified by Presray Corporation. The products are theFastlogs System and the FB33 System, although equal products from anothermanufacturer may be used in the place of Presray products. Door D5 will use the FastlogsSystem, and Doors D15, D16, D17, and D18 will use the FB33 System. A door rack willbe supplied at each location, and a storage rack will be provided as needed for thePresray products. The equipment numbers for these flood protection barriers areSQN BRR-634-D005, and SQN BRR-634-DO15 through SQN BRR-634-DO18,respectively. During flood mode preparations, an action is required to retrieve the barriersand install them in accordance with the manufacturer's instructions.3.0 SBPB RAI Question 3The SQN UFSAR Section 2.4A.2.1, "Flooding of Structures," states that the DG buildinghas redundant sump pumps to remove minor leakage.Do the sump pumps discharge leakage from the DG building at a point higher than therevised DBF level? If not, provide information on how backflow through the dischargepiping is prevented.3.1 TVA Response -SBPB RAI Question 3The Diesel Generator Building has two sump pumps (SQN PMP-040-0079 andSQN PMP-040-0080) installed in order to remove minor leakage. These pumpsdischarge leakage from the building through independent 2-inch lines with a centerlineelevation of 732 ft, 8 inches at the highest point, as shown in Figure 1 below. As seen inFigure 1, the sump also includes an emergency 24-inch drain. AOP-N.03 includes stepsto plug this 24-inch drain path.Page 3 of 13 ENCLOSURE2RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)B2-92Figure 1 -SQN Diesel Generator Sump Pump Discharge Line ElevationsAs stated in the SQN LAR, the DBF including wind wave run up during the PMF event iselevation 723.2 ft, which is 1.2 ft above the Diesel Generator Building operating floorelevation of 722.0 ft. Therefore, the discharge piping is approximately 9.4 ft above theDBF level.4.0 SBPB RAI Question 4The LAR states that heat removal from the steam generators will be accomplished usingthe high pressure fire protection system following a Stage II flood warning.Where are the required components of the high pressure fire protection system located?Is this system protected from the revised DBF levels?4.1 TVA Response -SBPB RAI Question 4As described in SQN UFSAR Subsection 2.4.11.5.1, the fire/flood mode pumps aresubmersible pumps located in the Condenser Cooling Water Pumping Station. ThePage 4 of 13 ENCLOSURE2RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)Condenser Cooling Water Pumping Station sump is at elevation 648 ft. The entrances tothe suction pipes for the fire/flood mode pumps are at elevation 651 ft which is 32 ft and24 ft, respectively, below the maximum normal water elevation of 683.0 ft and the normalminimum elevation of 675.0 ft for the reservoir. The fire/flood mode pumps and electricalcomponents are designed to operate submerged at DBF levels, and are started fromhandswitches located in the main control room located above DBF levels. The control andpump motor power for the fire/flood mode pumps is located at elevation 734 ft in theAuxiliary Building, which is adequate to provide protection from the proposed DBF level inthe Auxiliary Building in the SQN LAR (elevation 722.5 ft). Therefore, requiredcomponents of the high pressure fire protection system are protected from the DBF levels.5.0 SBPB RAI Question 5The LAR states that the spent fuel pool cooling pump motors platform is located in anenclosure that provides flooding protection up to elevation 724.5 feet. The spent fuel poolcooling pump enclosure caps are required to be installed in order to provide floodingprotection to this elevation.Describe the physical design of the enclosure and how installing the caps will ensureflooding protection up to the 724.5 feet elevation. Will installing the caps impact theperformance of the spent fuel pool cooling pumps? With the caps installed, can the spentfuel pool cooling pumps still be aligned for open reactor cooling as described in UFSARSection 2.4A.2.2, "Fuel Cooling"?5.1 TVA Response -SBPB RAI Question 5The Spent Fuel Pit Cooling (SFPC) pumps are located on a platform at elevation 721.0 ftin the Auxiliary Building. The SFPC pumps are protected from flooding by AuxiliaryBuilding walls on two sides and the SFPC pump enclosure constructed of steel plating onthe other two sides. The SFPC pump enclosure provides protection up to a flood elevationof 724.5 ft (top of the two sides constructed of steel plating), which is adequate to provideprotection from the proposed DBF level in the Auxiliary Building in the SQN LAR (elevation722.5 ft). In addition, the SFPC pump enclosure contains redundant sump pumpsconnected to vital power (SQN PMP-040-0077 and SQN PMP-040-0078). The sumppumps are part of the original plant design, provide secondary protection from floodleakage into the enclosure, and provide additional protection from piping and pumpaccumulated leakage.A design feature of the enclosure includes two 6-inch diameter drains located next to eachother on the enclosure that are normally open during operation to allow any leakage fromthe SFPC pumps to drain to the normal Auxiliary Building drains as shown in Figure 2below:Page 5 of 13 ENCLOSURE 2RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)4" x 150# RF blind flangesRemove flanges and Install Spool PiecePLAN EL. 7146" Cap with Chain (2 ea)Section B-B(48W1216-6)Figure 2 -SQN Spent Fuel Pit Cooling Pump Enclosure CapsThese drains are capped as required by AOP-N.03 during Stage II Flood Warningpreparations in accordance with maintenance instruction 0-FP-MXX-000-01 1.0, "FloodPreparation SFPC Pump Enclosure Caps, SFPCS Heat Exchangers, RCP Thermal BarrierBooster Pumps, and RHR Heat Exchanger Spool Pieces." The drains are located at thebottom of the enclosure near the floor elevation of 714.0 ft, the caps are attached to thedrains by chains, and the drains are readily accessible during Stage II Flood Warningpreparations. Installation of the caps does not affect the operation of the SFPC pumps inPage 6 of 13 ENCLOSURE2RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)any way, including aligning and operating the pumps for open reactor cooling as describedin the SQN UFSAR.6.0 SBPB RAI Question 6The Sequoyah UFSAR flooding protection plan states that the penetrations of the reactorbuilding, DG building, and essential raw cooling water intake station are designed towithstand the static and dynamic forces imposed by the DBF.Do the penetrations of these structures continue to withstand the forces associated withthe revised DBF and prevent leakage? Describe how the penetrations were evaluated forthe revised DBF.6.1 TVA Response -SBPB RAI Question 6The SQN protection and mitigation features that are considered in the licensing basisevaluation to protect against external ingress of water into SSCs important to safety aredescribed in SQN UFSAR Subsection 2.4.14, and assurance that SQN can be safely shutdown and maintained in these extreme flood conditions is provided by the discussionsgiven in SQN UFSAR Subsections 3.4, 3.8.1, 3.8.2, and 3.8.4. Based on the updatedhydrologic analysis as described in the SQN LAR, the requirements described inSQN UFSAR Subsections 3.4, 3.8.1, 3.8.2, and 3.8.4 were verified to remain valid.SQN UFSAR Subsection 3.8.4.1.7 describes the structural design of the Essential RawCooling Water (ERCW) Building. On December 12, 2012, TVA determined that theERCW Building may flood at the proposed DBF level due to conduit penetrations not beingsealed with material capable of making the building watertight. The lack of a barrier wouldallow flood waters to enter the ERCW Building at a rate greater than the sump pumps canremove creating a condition that could result in the ERCW Pumps being unavailable toperform their design function during a flood event above plant grade. Corrective actionshave been completed to replace the existing moisture barriers installed on the conduits inmanhole 33 with a sealant that is designed and has been tested to withstand a largeramount of pressure.As described in SQN UFSAR Subsection 3.8.1.3, the Shield Building cylinder wall issubjected to uplift forces and lateral static pressure computed using the full hydrostatichead measured from the water surface. The DBF elevations were used in determininghydrostatic heads. Due to water seals between the Shield Building and adjacentstructures, the lateral hydrostatic pressure was applied only to one-half of thecircumference for the design flood and maximum probable flood. For the PMF, theadjacent structures are allowed to flood, and lateral hydrostatic pressure was appliedaround the full circumference. Penetrations below the revised DBF level wereassessed as the result of the extent of condition for the deficiency associated with theERCW Building above. As a result of this review, it was determined that penetrationseals below the DBF level may not be qualified as watertight seals. The evaluation ofthis condition is being tracked in the TVA Corrective Action Program.As described in SQN UFSAR Subsection 3.8.4.1.1, pressure confining personnelaccess control doors located in the Auxiliary Control Building are required. ThePage 7 of 13 ENCLOSURE2RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)Auxiliary Control Building is allowed to flood during a PMF event. Therefore, the watertight annulus access doors (one per unit, doors A65 and A78), are secured duringexternal flood warnings to prevent water intrusion into the annulus area.SQN UFSAR Subsection 3.8.4.1.3 describes the structural design of the DieselGenerator building. See the response to SBPB RAI Question 2 for details of the plantmodifications implemented to ensure adequate flood protection for the Diesel GeneratorBuilding.Based on the above discussion, the structures, including penetrations, required towithstand the structural impacts of an external flood have been assessed, and areacceptable for the revised DBF levels with the exception of the conduit penetrations for theERCW and Shield Building as described above.Page 8 of 13 ENCLOSURE 2RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)ATTACHMENT 1DIESEL GENERATOR BUILDING EQUIPMENT DOORS (D1-D4) FLOOD PROTECTION BARRIERSSEQUOYAH NUCLEAR PLANTDRAWING CHANGE AUTHORIZATIONPI1C L3- i DCN--,iZfliOPAGE- _136 PAGE W.1RO.DELETEDSEE CONST NOTE Iff E-41M- eY,' EllITS *t -- 540 aLtAIrIIOBe fl-O-41T-B0OI COJIAENI Attn L LI 'LOS SnAIL*~ S Si-Sn.LLOJ CAINIIIT LL(SS 55 04 ItOS MUlti* 04 W.L.SB-E34.LOSL ESISAWY ALLIS LOS LI FOAL BALLOtS* a, n-*PB.Bfl-aOo, IOJIVENT 01105, LI nfl PULLRO. ADD000A-,Z 0-,1zvp C..-D AD RO, D ADDb RO, ADDRO, ADDd.AF I NC NOTES (DOT TO BE INCORPORATED),-FLOOD NARRIER UNIT S0N-0O-9RP-634-0DGI, -002. -00J AND -004 DELETEDFROM STAGCE I AND ADDED ON STACE 4 Of' THIS OCN (SEE OCA 22404-1302)NXiS (NOT ID W E 1INCORPORATED)-., ERlN ID rO RE qF0OVED AND PIPES CAPPED SEE OCAS 22404-1304 Ti-/RU !506F~04 ~'OOOS221~ -~A.-R20 ~ i-t(i...- V2/i2 DCN 22404 /PIC 23179RtEV ,LNDO Chs..kO.d/U.t. C-HANCE REFERENCECONLTRACT NO N/OCA PRERECUISITES NONE$1/ CCO TNO N/A01siftlFOLt N/ASTAGE 4CAT __N/A16W418-2 REV EDCA NO 22404-4806JN1I 2Page 9 of 13 ENCLOSURE 2RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)ATTACHMENT 2DIESEL GENERATOR BUILDING PERSONNEL ACCESS DOOR (D5) AND EMERGENCY DOORS (D15-D18)CONCRETE BERM FLOOD PROTECTION BARRIERSSEQUOYAH NUCLEAR PLANTDRAWING CHANGE AUTHORIZATIONI PIC_ 23179 DCN 22404_A _._' , PAGE I_ ODETAIL A14\-SEE DETAIL A14PARTIAL PLAN -EL 722'-0"NOTES:I ALL CONCRETE MATERIALS AND WORKMANSHIP SHALL BEIN ACCORDANCE WITH THE LATEST EDITIONS OF ACI 318AND ACT 301.2 ALL CONCRETE SHALL BE CLASS 300.75 AFW MIN. (3000 PSI)AND SHALL BE PLACED IN ACCORDANCE WITH GENERALENGINEERING SPECIFICATION C-2.5 ALL EMBEDDED METALS TO CONFORM TO ASTM A36. UNLESSOTHERWISE NOTED ON DRAWINGS. ALUMINUM SHALL NOT BEEMBEDDED IN CONCRETE UNLESS SPECIFICALLY APPROVED.ALL UNFORMED CONCRETE SURFACES SHALL BE STEEL TROWELLED,ALL MATERIALS SHALL BE OA LEVEL I UNLESS OTHERWISE NOTED.CONCRETE SLAB & WALL IN CONTACT WITH CONCRETEWATER BARRIER SHALL BE SCARIFIED TO A DEPTH Y4 ID A"AND COATED WITH AN APPROVED BONDING AGENT PER GENERALENGINEERING SPECIFICATION C-34.I REINFORCING STEEL SHALL BE ASTM A615 GR, 603 CHAMFER ALL EXPOSED CONCRETE EDGES -",DIMENSIONAL TOLERANCE FOR REINFORCEMENT PLACEMENT IS */- )",UNLESS NOTED13 (I DENOTES IN PLACE CONCRETE.C(CUTTING REINFORCEMENT FOR GROUTED HOLES IS NOT ALLOWEDADDITIONAL VERTICAL REINFORCEMENT MAY BE INSTALLED TO MAINTAIN2- MAXIMUM, 3' MINIMUM BAR SPACING.SHOLES FOR GROUTED REINFORCEMENT TO BE I 5- DIAMETER & DRILLEDTO A DEPTH 0 5- GREATER THAN BAR DEPTH1. ALL GROUT TO BE NON-SHRINK WITH A MINIMUM STRENGTH = 3000 PSII- CONCRETE SHALL CONTAIN FIBER REINFORCEMENT MEETING THEREOUIREMENTS OF ASTM C1116. SECTION 4 1.3 TYPE Ill. AND NOTE 2DOSAGE SHALL BE 2.5-3 LB/CU.YDMASTERFIBER FlOG ENHANCED FIBRILLATED POLYPROPYLENE FIBERTANUFACTURED BY BASE IS ACCEPTAB! [ TO US ANT FIBERREINFORCEMENTNOTES: (CONTI16. TESTING SHALL COMPLY WITH SECTION B.8.4 OF GENERAL ENGINEERINGSPECIFICATION G-2 EXCEPT THAT ALL TESTING IS WAIVED INACCORDANCE WITH SECTION B.8.8.17. CONCRETE MAY BE PURCHASED AUGMENTED DUALITY D10 SEISMICCATEGORY I(L).18. NO ATTACHMENTS ARE PERMITTED TO DETAIL A14 AND/OR B14.CALCULATION BRANCH/PROJECTREFERENCE DRAWINGS: IDENTIFIERS: CDO0009992013000045ION320-1ION321-216W418-2CONSTRUCTION NOTES: (NOT TO BE INCORPORATED)1. WORK THIES DCA WITH DCA 22404-4807. -4810 AND -4311,DIESEL GENERATOR BUILDINGUNIT 0CONCRETE FLOOD BARRIERSDIESEL CEN -EL. 722.0'PLAN, SECTIONS & DETAILS0 OC~... /~/) DN 22404 /PIC 23179REY P.o.4T)d Cch4.4d/0t CH'ANCE REFERENCECONTRACT NO:.Dc,' PWTntouJiTsms NONEANT CCD NO 0iON321-140IYCIPLOI. ,_ CIVILSTAGECAI 4AFFECTED BATE DRAWING NO ADM REVNEW DRAWING (ANT)OCA NO 22404-480 UNII:T .D_____________________________________________________ L LPage 10 of 13 ENCLOSURE 2RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)ATTACHMENT 3DIESEL GENERATOR BUILDING WASTE LINE MODIFICATION FOR FLOOD PROTECTIONDCN 22404SEQUOYAH NUCLEAR PLANT DRAWING CHANGE AUTHORIZATION PAGE SkADDSEE GONS'T NOTESF1 -Fl0 4 jCN2404REV P~p~./o.Ch..k. d/D. t. CHANGE REFERENCE00,CONSTRUCTION NOTES: (NOT TO BE INCORPORATED)1. REMOVE URINAL AND CAP DRAIN LINE WITH 2"THREADED CAP MARK NO. A270.2. WORK THIS DCA WITH DCA 22404-1501 & -1502CONTRACT NO: N/A STAGE 1DCA PREREOUISITES: NONEANT cco NO: N/A CAT. N/.DISCIPLINE N/AAFFECTED BASE DRAWING NO. AND REV17W710-1 REV ADCA NO. 22404-1503 UNIT: IPage 11 of 13 ENCLOSURE 2RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)ATTACHMENT 4BUILDING FUEL FILL PORTS MODIFICATION FORDIESEL GENERATORFLOOD PROTECTIONDCN 22404SEQUOYAH NUCLEAR PLANT DRAWING CHANGE AUTHORIZATION IPAGE__lCONSTRUCTION NOTES: (NOT TO BE INCORPORATED)1 .REMOVE COVER AND INTERNAL PLUG OF FILL PORT MARK #2+52. THREAD IN PIPE MARK #166.3. ATTACH REMAINING ITEMS AS SHOWN.NOTESADDI NTSPIPE TO THREAD INTO FILL PORT (MARK #245) INTERNAL PLUGTHREADED CONNECTION, THREADED CONNECTION TO HAVE AN APPROVEDTHREAD SEALANT. FILL PORT COVER & INTERNAL PLUG TO BEo ...~.. $DCN 22404REV Pr-P-rd/Oot. Chk..A o .Oq CHANCE REFERENCE00A)CONTRACT NO: N/A STAGE 1OCA PREREOUISITES: NONEANT CCD NOt N/A CAT, N/ADISCIPLINE N/AAFFECTED BASE DRAWING NO. AND REV1,2-17W585-3 REV 0OCA NO. 22404-1500 UNIT: 0Page 12 of 13 ENCLOSURE 2RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)REQUEST FOR ADDITIONAL INFORMATION (RAI)ATTACHMENT 5DIESEL GENERATOR BUILDING PERSONNEL ACCESS DOOR (D5) AND EMERGENCY DOORS (D15-D18)ENGINEERED FLOOD PROTECTION BARRIERSSEQUOYAH NUCLEAR PLANT DRAWING CHANGE AUTHORIZATION PAEN zRO, DELETED--.SEE CONST NOTE 3 -L'jASOAD----lRO, AD!.1.FQR gl(10t.)jF~U-0flQ-0,. 722 4.47 RIP lT--A-AT EE AS (LATER)W tA ESC-S OA 5)2 sAR -LTIR*I MA 30 EO .S A RM(ATREIasA flOf-t1-tS( PSR4 PARC ImSwm .P (LATERI* ITAn..n)EET MC rw Al (LATE)4 EISA 00-A-KE -.VAlt MEC P MR (UtERIP5 1117 EMS l F-7TERRERRR4.00Ao0VO2 _________________________1 1________________0 Z.; L OCN 22404REV P-p-d/S8DEIR CIIS.k~iACEI I KANGE REFERENCECONSTRUCTION NOTES (NOT TO BE INCORPORA TED):1. FIELD TO LOCATE STORAGE RACKS AS SHOWN. SOME LOCATIONS REoUIREEXISTING ComDITIES TO BE RELOCATED.2. STORAGE RACK FOR FBJ3 PANELS ARE AN ADDITIONAL SET OF JAMBBRACKETS AMOUNTED TO WALL.3. URINAL TO BE REMOVED AND PIPES CAPPED SEE OCAS 22404-1501 THRU 150J.4. STORAGE RACK IN THIS LOCATION TO BE PLACED BELOW STAIR PLATFORM.CONTRACT NO: N/A STAGE 1DCA PREREQUISITES: NONEANT CCo NO: N/A CAT. NDISCIPLINE N/AAFFECTED BASE DRAWING NO. AND REV16W418-2 REV DDCA NO. 22404-1801UNIT: 1a aPage 13 of 13