ML13101A183

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:	James Shea 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 37402 April 5, 2013 10 CFR 50.4 10 CFR 50.90 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Sequoyah Nuclear Plant, Units 1 and 2 NRC Docket Nos. 50-327 and 50-328 Facility License Nos. DPR-77 and DPR-79

Subject:

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) (TAC Nos. ME9238 and ME9239)

References:

1. TVA Submittal to NRC Document Control Desk, "Application to Revise Sequoyah Nuclear Plant Units 1 and 2 Updated Final Safety Analysis Report 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 Updated Final Safety Analysis Report to Adopt a Revised Hydrologic Analysis (TAC Nos. ME9238 and ME9239)," dated January 25, 2013 (ADAMS Accession 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 and DPR-79 for the Sequoyah Nuclear Plant (SQN), Units 1 and 2. The license amendment request (LAR) proposed to revise the SQN, Units 1 and 2, Updated Final Safety Analysis Report (UFSAR) to reflect the results from new hydrologic analysis. These proposed changes are consistent with the latest approved hydrology calculations.

Printed on recycled paper

U.S. Nuclear Regulatory Commission Page 2 April 5, 2013 By letter dated January 25, 2013 (Reference 2), the Nuclear Regulatory Commission (NRC) forwarded a request for additional information (RAI) originating from the NRC Health 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 no changes required to the LAR as submitted in the Reference 1 letter as a result of this additional information. Consistent with the standards set forth in 10 CFR 50.92(c), TVA has determined that the additional information as provided in this letter does not affect the no significant hazards considerations associated with the proposed amendment previously provided in Reference 1. TVA has further determined that the proposed amendment still qualifies for a categorical exclusion from environmental review pursuant to the provisions of 10 CFR 51.22(c)(9). Additionally, in accordance with 10 CFR 50.91 (b)(1), TVA is sending a copy of this letter, the enclosures, and the attachments to the Tennessee Department of Environment and Conservation.

There are no new regulatory commitments included in this submittal. Please address any questions 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 this 5th 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 Additional Information (RAI) cc (Enclosures):

NRC Regional Administrator - Region II NRC Senior Resident Inspector - Sequoyah Nuclear Plant Director, Division of Radiological Health, Tennessee State Department of Environment and Conservation

ENCLOSURE1 TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 RESPONSE 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 Final Safety Analysis Report Regarding Changes to Hydrologic Analysis, (SQN-TS-12-02) 1.0 AHPB RAI Question I What, if any, operator actions are being changed, added, or deleted besides those supporting the installation of the spent fuel pit cooling pump enclosure caps, the sand bagging of the diesel generator (DG) building, and the installation of temporary barriers on the earthen embankments of the dams at the Cherokee, Fort Loudoun, Tellico, and Watts Bar Reservoirs?

1.1 TVA Response - AHPB RAI Question 1 There are no other changes, additions, or deletions to Sequoyah Nuclear Plant Units 1 and 2 (SQN) site flood mode preparation actions based on the revised probable maximum flood (PMF) and design basis flood (DBF) levels, or the reevaluation of flood warning times, in the updated hydrologic analysis.

As described in the SQN license amendment request (LAR), the Stage I and Stage II Flood 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 as a result of the reevaluation is the revised forecasted plant site water levels where Stage I Flood Warning actions are required to begin. The Stage I threshold levels will be addressed in the TVA River Operations instructions that determine when the SQN site should 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 the abnormal operating procedure (AOP) for external flooding. These revised action levels will be incorporated in the TVA River Operations instructions prior to the implementation date of the final NRC-approved license amendment.

There are other flood mode preparation actions that have been revised as improvements were identified as a result of simulations and validation of the AOP and instructions performed by TVA. These changes are not required as a result of the updated hydrologic analysis, but rather as a result of improving implementation of flood mode preparation and operation procedures and instructions to ensure the current licensing basis requirements for meeting flood warning times are met.

Page 1 of 29

ENCLOSURE1 RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)

REQUEST FOR ADDITIONAL INFORMATION (RAI) 2.0 AHPB RAI Question 2 What kind of training is planned for actions supporting the proposed changes to the SQN UFSAR? How often will training on the flood procedure/plan be done? When will training be complete? For example, will training be complete prior to issuance of the revised UFSAR proposed in this LAR?

2.1 TVA Response - AHPB RAI Question 2 Changes to SQN site procedures and instructions are evaluated as part of the existing Site Training Program. These changes to the procedures and instructions to comply with the SQN UFSAR changes are required to be implemented prior to the implementation date of the final NRC-approved license amendment.

The required changes to the procedures and instructions have been identified, and a training needs analysis in accordance with the Site Training Program will determine the final content and schedule for training. Changes to abnormal operating procedures that require training are communicated through the use of a standing order to brief operators on the major changes, and classroom training is conducted during the next scheduled licensed operator requalification cycle.

3.0 AHPB RAI Question 3 List the procedures affected by the proposed LAR along with a short summary of the change. When will procedure changes, additions, and deletions associated with the proposed UFSAR changes be completed? For example, will procedures be revised and issued prior to initiation of training?

3.1 TVA Response - AHPB RAI Question 3 AOP-N.03, "External Flooding," controls the overall timing and sequence of implementing actions for flood mode preparations and operations, and utilizes implementing work orders, general operating instructions, emergency operating instructions, flood preparation maintenance instructions, and other AOPs to complete the required actions by the applicable SQN site organizations. As a result of the SQN LAR, AOP-N.03 will be revised to address installation of permanent engineered flood barriers for the Diesel Generator Building 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 SQN LAR. These changes address the results of simulations performed to verify the capability to complete required flood mode preparations within the required Stage I and Stage II Flood Warning times, and are not a result of the updated hydrologic analysis which does not revise these limiting times.

As discussed in the response to AHPB RAI Question 2, required changes to the procedures and instructions have been identified, and are required to be implemented prior to the implementation date of the final NRC-approved license amendment. In Page 2 of 29

ENCLOSURE1 RESPONSE 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 the final content and schedule for training.

4.0 AHPB RAI Question 4 Were any human performance lessons learned from operating experience, sister plants, the Fukushima incident? If yes, describe?

4.1 TVA Response - AHPB RAI Question 4 Changes to the procedures and instructions have been implemented to address human performance lessons learned from operating experience and the Fukushima incident. In addition, changes have been implemented based on informal reviews of procedures from the other TVA sites. For example, AOP-N.03 was recently revised to streamline the process for establishing flood mode core cooling during a Stage II Flood Warning based upon insights gained from a review of the Watts Bar Nuclear Plant flood procedure.

5.0 AHPB RAI Question 5 Was at least one full complement of required personnel used in the verification and validation of the proposed flood plan? If not, what plans have been made to assure that a representative sample of personnel is included in verification and validation of the flood plan?

5.1 TVA Response - AHPB RAI Question 5 In response to the nuclear fuel damage at Fukushima Daiichi due to earthquake and subsequent 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, Regarding Recommendations 2.1, 2.3, and 9.3 of the Near Term Task Force (NTTF) Review of Insights from the Fukushima Dai-ichi Accident). As part of this request, a reasonable simulation was performed of the flood response AOP in accordance with an approved procedure, CTP-FWD-100, "Flood Protection Walkdowns." The USNRC issued an Endorsement Letter on May 31, 2012 that endorsed the Nuclear Energy Institute (NEI) 12-07, "Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features" document. The guidance followed for the reasonable simulation was consistent with NEI 12-07.

During the reasonable simulation, an active Senior Reactor Operator (SRO) stepped through the procedure and, with the assistance of Maintenance, Engineering, Radiation Protection, a retired Unit Supervisor SRO, and a retired Shift Manager, developed a timeline for the steps of the procedure. Personnel required for each step were also determined in order to assess the adequacy of available resources, ensuring that a full complement of required personnel would be available to perform the required flood mode preparation actions.

Page 3 of 29

ENCLOSURE1 RESPONSE 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 Licensing Basis (CLB), and consistent with the proposed licensing basis in the SQN LAR, was evaluated during initial reasonable simulation results. Discussion and evaluation of the instructions given in AOP-N.03 were made during the reasonable simulation. As each step of the procedure was discussed, estimates of time to perform the actions in the procedure were made. The flood scenario identified as most critical in the Updated Final Safety Analysis Report (UFSAR) was used as the basis for evaluating whether the instructions could be implemented in the available time. The reasonable simulation also assessed implementation of any actions required for flood protection features. An example of a time dependent activity is the time to install the spool pieces to realign the systems.

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 Flood Warning was received from the River Forecast Center staff. The reasonable simulations included the following steps:

1. Raw data tabulation was performed from individual procedure step and reasonable simulation exercises required to complete flood mode preparations. No integration or resource loading had occurred.

2. The raw data was integrated and resource loaded considering the flood mode AOP actions, maintenance instructions actions, and chemistry sampling. These activities were sequenced and the actions were evaluated to determine which can be performed in parallel versus in series.

3. Stage I activities included the rapid shutdown of the plant using AOP-C.03, "Rapid Shutdown or Load Reduction," and plant communications with local media and state government agencies. Stage I Flood Warning activities also included communications made to acquire off-site plant personnel required to implement the flood protection procedures.

4. Additional off-site personnel assumed to be available to implement the flood mitigating preparation procedures were determined in the following manner. The PMF event was conservatively assumed to start on a holiday weekend night to minimize on-site staff and off-site staff availability for being phoned in for work. The assumptions for the manpower 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 and Instrument and Controls (I&C) per shift 0 Normal Operating Crew (NOC) includes one Mechanical, one Electrical, one I&C, and a supervisor; the NOC is already on site 0 Four additional personnel per shift not on site but available for call in 0 Assumed 67% (approximately 60) of available personnel not on site to have Fitness for Duty (FFD) issues or other complications due to local flooding and unable to respond to site Page 4 of 29

ENCLOSURE1 RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)

REQUEST FOR ADDITIONAL INFORMATION (RAI)

• Total of 29 maintenance personnel expected to respond to the call

b. 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&C o 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 Work Contol SRO)

" Four Reactor Operators

• Eight Auxiliary Unit Operators

d. 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 CLB 10 hour1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> time period, which is the same as in the SQN LAR.

6. The critical path Stage II Flood Warning activities were determined by development of a timeline.

The reasonable simulation verified that the actual number of personnel required to implement the flood mode preparation activities were bounded by the assumption of available personnel described in item 4 above. Therefore, based on the reasonable simulation, it was determined that the required personnel are available and capable of implementing the Stage I and Stage II Flood Warning preparations within the overall flood mode 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 6 During the probable maximum flood (PMF), what communication methods will be likely to fail (fully or partially) and which will still be available for individuals to communicate with the control room, technical support center, and other plant areas? Will site-wide announcements be possible during all stages of the PMF?

6.1 TVA Response - AHPB RAI Question 6 During emergencies such as a PMF event, SQN site operations and Emergency Plan personnel have several communication methods available to communicate with the control room, technical support center, and other plant areas. As described in the SQN UFSAR Page 5 of 29

ENCLOSUREI RESPONSE 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 and plant paging are the sound powered telephone systems, inplant radio system, Electronic Private Branch Exchange (EPBX) telephone equipment, and loud speaker paging.

As described in SQN UFSAR Table 9.5.2-1, the communications equipment that is assured to be available for intraplant communications during a PMF event with and without a loss of offsite power includes portion of the sound powered telephone system and the inplant radio system, except for those components of the system that are submerged during 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 requires performance of flood preparation maintenance instruction FPMI-12.10, "Disconnection of Sound-Power Telephones Located Below Elevation 732," during Stage II Flood Warning preparations. The purpose of this instruction is to describe the procedure for disconnecting the sound powered telephones located below elevation 732 ft to prevent interruption in communications in other areas as a result of a PMF event. Portions of the sound powered telephone systems that remain above the flood levels are available during a PMF event. Therefore, wired voice communications above the DBF levels are assured throughout a PMF event.

The inplant radio system provides voice communications throughout the plant for plant personnel. This system consists of repeaters, remote control units and very high frequency (VHF) portable radios. A Radio/Cell Phone System provides a diverse communications system for voice, paging, and text messaging that is available both onsite and offsite. The system interfaces with the VHF inplant system in the turbine building to allow communications through the existing VHF Distributed Antenna System. Portions of the inplant radio system that remain above the flood levels are available during a PMF event, but only through direct radio-to-radio communications. Therefore, wireless voice, paging, and text messaging communications above the DBF levels are assured throughout a PMF event.

The EPBX is installed to provide primary 2-way communications throughout SQN as well as access to offsite circuits, and provides for loud speaker paging through the general plant public address system discussed below. The EPBX is powered from a 48V DC source. This source consists of a telephone battery charger, a spare battery charger, a regulating power board, and a battery. The telephone battery charger is fed from a non-i E source with an alternate feed from a Train A diesel-backed board. The spare battery charger is fed from a Train A diesel-backed board with an alternate feed from a Train B diesel-backed board. The 48V batteries and chargers which power this system are below the DBF level. Therefore, the EPBX may or may not be available during an external flood event with a loss of offsite power, depending on actual flood conditions, but is 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 control and the auxiliary control room. In addition to the paging handset locations, this equipment may be accessed from any EPBX telephone. The speaker-amplifiers are fed in parallel from an alternating current lighting source. The paging equipment is dispersed in the control building and powerhouse areas. Single or multiple open circuits or amplifier failure Page 6 of 29

ENCLOSURE1 RESPONSE 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 of the equipment will not impair the use of the paging equipment from the local paging stations located in the control room, or the auxiliary control room. The general plant public address system may or may or may not be available during an external flood event with a loss of offsite power, depending on actual flood conditions, but is not available once flooding reaches plant grade.

In response to the nuclear fuel damage at Fukushima Daiichi due to earthquake and subsequent 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, Regarding Recommendations 2.1, 2.3, and 9.3 of the Near Term Task Force (NTTF) Review of Insights from the Fukushima Dai-ichi Accident). As part of this request, TVA provided additional information requested regarding plans to enhance existing communications systems power supplies until the communications assessment in response to Recommendation 9.3 and the resulting actions are complete. As stated in the response provided by letter from TVA to the NRC, "Tennessee Valley Authority (TVA) Day Response to NRC Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendation 9.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident," dated June 11, 2012 (ADAMS Accession No. ML12164A678), TVA deployed seventeen (17) satellite phones at each licensed operating TVA nuclear facility. These phones replaced and upgraded older phones that were previously located at each site. An additional seventeen (17) satellite phones were deployed at TVA Nuclear Power Group (NPG) offices in the TVA Corporate headquarters located in Chattanooga, Tennessee. TVA also purchased twenty (20) portable generators. These 2000-Watt portable generators were obtained to keep the satellite phone batteries charged. Five (5) of these generators have been placed at each of the three TVA licensed operating nuclear facilities, and the remaining five (5) generators were sent to the Central Emergency Control Center (CECC), TVA's offsite emergency center, located in Chattanooga, Tennessee. These generators at each site are stored in a secured location on the site owner-controlled area. Radios and sound-powered phone systems are also available at TVA licensed operating facilities for onsite communications with operators in the field and the control room for safe shutdown and recovery. Jacks for the installed sound-powered phone systems are located in areas needed to support monitoring and operation of essential equipment. TVA nuclear facilities were previously provided 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 within the facility. Batteries for these radios may also be charged using the portable generators previously mentioned. TVA has developed documented guidance for deploying the portable generators described above during and after a Beyond Design Basis External Event.

Page 7 of 29

ENCLOSUREI RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)

REQUEST FOR ADDITIONAL INFORMATION (RAI) 7.0 AHPB RAI Question 7 Describe the changes to the simulator, if any, that are needed to support the proposed license amendment.

7.1 TVA Response - AHPB RAI Question 7 There are no changes to the simulator required as a result of the updated hydrologic analysis 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 other AOPs. The physical interim compensatory measures and the replacement permanent modifications made to the facility do not affect the physical layout and control or software requirements for the simulator.

8.0 AHPB RAI Question 8 Describe any credible errors that could affect the pre-staging or the actual placing of sandbags 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 the procedure 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 be needed, 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 8 The installation of permanent plant modifications to protect the Diesel Generator Building entrances from a DBF, including future installation of permanent engineered flood barriers, has replaced the use of sandbag berms. These plant modifications and the required actions for installation of permanent engineered flood barriers are described in the response to SBPB RAI Question 2 in Enclosure 2 of this submittal.

9.0 AHPB RAI Question 9 Describe any credible errors that could be made when installing the spent fuel pit cooling pump enclosure caps. Are the involved actions described in a controlled procedure? Will training be provided?

Page 8 of 29

ENCLOSUREI RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)

REQUEST FOR ADDITIONAL INFORMATION (RAI) 9.1 TVA Response - AHPB RAI Question 9 The Spent Fuel Pit Cooling (SFPC) pumps are located on a platform at elevation 721.0 ft in the Auxiliary Building. The SFPC pumps are protected from flooding by Auxiliary Building walls on two sides and the SFPC pump enclosure constructed of steel plating on the other two sides. The SFPC pump enclosure provides protection up to a flood elevation of 724.5 ft (top of the two sides constructed of steel plating), which is adequate to provide protection from the proposed DBF level in the Auxiliary Building in the SQN LAR (elevation 722.5 ft).

A design feature of the enclosure includes two 6-inch diameter drains located next to each other on the enclosure that are normally open during operation to allow any leakage from the SFPC pumps to drain to the normal Auxiliary Building drains as shown in Figure 1 below:

PLAN EL. 714 (2 ea)

Section B-B (48W1216-)

Figure 1 - SQN Spent Fuel Pit Cooling Pump Enclosure Caps Page 9 of 29

ENCLOSURE1 RESPONSE 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 Warning preparations in accordance with maintenance instruction 0-FP-MXX-000-01 1.0, "Flood Preparation SFPC Pump Enclosure Caps, SFPCS Heat Exchangers, RCP Thermal Barrier Booster Pumps, and RHR Heat Exchanger Spool Pieces." The drains are located at the bottom of the enclosure near the floor elevation of 714.0 ft, the caps are attached to the drains by chains, and the drains are readily accessible during Stage II Flood Warning preparations.

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 the location of the drains, and

2. 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 after installation during Stage II Flood Warning preparations. Based on the non-complex nature of the task, the instructional details including plan and sectional drawing, the staging of the caps at the drains using attached chains, and the visual check after installation, the probability of error in installing the caps is extremely low. In accordance with the Site Training Program, a training needs analysis of the AOP and maintenance instruction determines the final content and schedule for training.

10.0 AHPB RAI Question 10 On page 15 of 39 in Enclosure 1 of the LAR dated August 10, 2012, the licensee states that TVA's climatic monitoring, flood predicting systems and flood control facilities permit early identification of potentially critical flood producing conditions and reliable prediction of floods that may exceed plant grade well in advance of the event. Is this prediction done using a controlled procedure consistent with the assumptions of the current hydrology analysis? What actual margin is associated with the term "well in advance"? Describe in terms of approximate number of minutes, hours, or days.

10.1 TVA Response - AHPB RAI Question 10 TVA's climatic monitoring, flood predicting systems and flood control facilities are under the jurisdiction of TVA River Operations. This organization is responsible for balancing the competing demands of the Tennessee River and its tributaries with respect to flood-damage control, navigation, dam safety, hydroelectric power production, recreation, water supply, and water quality. Within the TVA River Operations organization, the staff of TVA River Scheduling is responsible for scheduling day-to-day operations of the TVA integrated 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 for developing, dispatching, and monitoring real-time multipurpose operating plans for the impoundment and releases of water from TVA-managed reservoirs. Operating plans are Page 10 of 29

ENCLOSURE1 RESPONSE 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 Forecast Center in Knoxville, Tennessee. The River Forecast Center balances operating plans in order to meet system demands for flood-risk reduction, navigation, hydroelectric generation, water quality, water supply, and recreation. The River Forecast Center also coordinates daily operating plans with the U. S. Army Corps of Engineers.

In developing forecasts, the River Forecast Center uses state-of-the-art equipment to monitor the river system and adjusts operations based on the continuously changing demand for water. Weather conditions, rain data, reservoir inflows and outflows, and reservoir elevations are monitored in real-time through satellite and hard-lined communication equipment. Continuous monitoring of reservoir information allows the River Forecast Center to quickly respond to system demands during critical periods. Once collected and validated, the data is used as input for modeling tools for simulating reservoir releases and developing strategies for multiple operating scenarios. The river forecasts are used to disseminate information regarding reservoir levels and scheduled water releases to internal and external stakeholders. Information from the forecasts can then be used in a wide variety of decision-support tools, including bulk electric system planning, evaluating thermal cooling needs at TVA coal fired and nuclear plants, emergency management, river-shipper planning, and recreational user scheduling. The River Forecast Center serves as the focal point of information for any issue related to operating the Tennessee River system.

TVA River Operations is responsible for notification and response in any type of emergency at one or more of its assets that has the potential to affect the health and safety of the TVA workforce or the general public, the environment, or TVA property.

River Operations is also responsible for agency-level support during large-scale emergencies that affect more than one strategic business unit or the whole agency. The Emergency Preparedness group in River Operations develops procedures guiding emergency response for such emergencies and maintains testing, training, and exercises to ensure effective emergency planning and readiness by emergency staff.

RO-SPP-35.1, "River Operations Emergency Response Plan," is the highest tier emergency response procedure in River Operations. It covers the overall emergency response philosophy (based on the National Incident Management System (NIMS) and Incident Command System), and addresses the systematic approach to responding to emergencies. This procedure prescribes a consistent response process that applies to any emergency that may occur at a River Operations asset such as dam safety, fire, environmental releases, terrorist attack, etc. The response procedures contained within RO-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 Federal Government 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 and approval of individual Emergency Action Plans for dam safety for each of the of River Operations 49 projects (i.e., dams and associated reservoirs). The procedure contains the generic language and process that apply for response to a dam safety emergency at any of the River Operations projects. Each project-specific Emergency Action Plan contains a generic response section detailing the purpose of the Emergency Action Plan, roles and Page 11 of 29

ENCLOSUREI RESPONSE 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 chart and checklists for primary users. Individual Emergency Action Plans also include a location specific emergency notification directory, flood inundation maps unique for each project, and other specific dam safety resources appropriate for the project in question.

Emergency Action Plans are controlled documents which are distributed within TVA and to external emergency response partners such as county emergency-management agencies, the National Weather Service, the U.S. Army Corps of Engineers, and other entities which may be affected by or engaged with TVA in the unlikely event of a dam breach or probable maximum flooding. The top priority for River Operations during a dam safety emergency is to maintain system integrity and ensure the safety of the public and TVA property, to the greatest extent possible. The Emergency Action Plans are maintained and exercised in accordance with procedures TVA-SPP-27.6, "Emergency Preparedness for Dams," and RO-SPP-27.6, "River Operations Emergency Preparedness for Dams," which draw on the Federal Guidelines for Dam Safety and the FederalEnergy Regulatory Commission Engineering Guidelines for the Evaluation of Hydropower Projects.

RO-SPP-35.4, River Operations & Renewables Continuity of Operations (COOP) Plan is intended to ensure that River Operations remains capable of conducting its essential functions under all threats and conditions in order to support the TVA Mission Essential Functions. The procedure provides plans for continuing to operate if one of River Operations primary operating locations (Knoxville, Tennessee or Chattanooga, Tennessee) is rendered unusable. The process provides for identification of essential personnel and alternate operating locations for such personnel so that they may continue to perform their essential functions.

In order to be able to implement the requirements of River Operations emergency response procedures, the Emergency Preparedness program provides training to staff, coordinates with outside agencies to maintain working relationships, and manages the TVA River Operations Emergency Operations Center (REOC) located in Chattanooga, Tennessee. This facility provides a location for emergency staff to gather to support response actions at the site of an emergency. The Emergency Preparedness staff is also responsible for coordinating with the agency-level emergency entity, Crisis and Emergency Management, to ensure agency procedures and programs are being supported 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 monitoring stations; running forecast models for the integrated operations of the Tennessee River and reservoir system; making internal and external notifications as appropriate; and serving as the point of contact for river system emergency actions. The River Forecast Center staff forecasts inflows into the Tennessee Valley watershed for a 14-day period, which involves assessing rain on the ground and determining how much of that rain will end up in the Tennessee River system as runoff, as well as considering the likelihood of future rain in weather forecasts.

The River Forecast Center serves as the point of contact for river system emergency actions within the Tennessee Valley and makes notifications of high flows, elevations and other system impacts to appropriate emergency management agencies and other internal Page 12 of 29

ENCLOSUREI RESPONSE 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 I and Stage II Flood Warnings, as specified in the TVA River Scheduling Notification Directory, a desktop instruction that is maintained by TVA River Scheduling for use by the River Forecast Center staff during emergencies. Rainfall, stream flows, reservoir headwaters, reservoir tailwaters and reservoir releases are monitored on a 24-hour basis for compliance with planned operations. Reservoir elevations and discharge flow rates are also forecast for the system for a 14-day period. A computer-based RiverWare model is used to simulate weather conditions, reservoir inflows, reservoir outflows, and reservoir elevations. RiverWare is a river-basin modeling software system developed by the University of Colorado, under primary sponsorship by TVA and the U.S. Bureau of Reclamation. Optimization and simulation functions of this model have been used for several years by TVA to schedule the operation of the reservoir system.

The formal Stage I and Stage II Flood Warning notifications from the River Forecast Center staff, under the direction of the River Scheduling Lead Engineer, are made to SQN control room supervision based on rainfall on the ground observed measurements, with no consideration of forecasted rainfall. This is consistent with the assumptions of the current hydrology analysis. However, the River Forecast Center maintains an ongoing forecast of reservoir levels for a 14-day period. The forecast (prediction) is based on normal forecasting processes utilized by the River Forecast Center on a daily basis for forecasting reservoir flows and elevations for multiple purposes, including flood control, as described above 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 reaching the Stage I and Stage II Flood Warning thresholds. The initial trigger point for activation of the REOC is based on predicted headwater elevations at each dam. Therefore, it would be possible for the River Forecast Center to forecast the rain events and predict the trigger headwater elevations several days in advance. Thus, early declaration of Stage I and Stage II Flood Warnings are possible for these situations. For additional discussion of the methods and instructions used by the River Forecast Center to determine conditions for issuing Stage I and Stage II Flood Warnings, refer to the response to AHPB RAI Question 12.

The discussion in the SQN LAR of climatic monitoring and early identification of potentially critical flood producing conditions is based on the use of predicted rainfall by the River Forecast Center in addition to the rainfall which has already occurred. Within the limitations of weather forecasting techniques, the predicted rainfall forecasts provide additional guidance regarding the possible severity of future precipitation up to days in advance. The River Forecast Center river forecasts routinely incorporate predicted rainfall, and can accurately predict river elevations that would occur if the rainfall event happened as forecast over the next 10 days. However, as defined in the SQN LAR, the formal 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 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 /> 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). Because of the extensive historical experience and knowledge of operations of the Tennessee River watershed by the River Forecast Center, the quality of climatic monitoring and early identification of potentially critical flood producing conditions is assured.

Page 13 of 29

ENCLOSURE 1 RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)

REQUEST FOR ADDITIONAL INFORMATION (RAI) 11.0 AHPB RAI Question 11 The licensee states on page 29 of 39 in Enclosure 1 of the LAR: "Flood warnings are issued in real-time by TVA RO [River Operations]." In what form are the flood warnings issued? How does the SQN control room receive the warning and how long does it take to get from TVA (RO) to the control room supervisors?

11.1 TVA Response - AHPB RAI Question 11 Flood notification from the River Forecast Center staff, under the direction of the River Scheduling 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 and notification process. Surveillance instruction 0-SI-OPS-244-215.0, "Flood Protection Communications," provides further assurance that the earliest possible notification of floods potentially exceeding plant grade can be provided. The River Forecast Center staff will predict flood levels based on rainfall on the ground or potential failure problems with one or more dams combined with critical water-head elevations and flood producing rainfall. During these events communications are established directly between SQN control room supervision and the River Forecast Center staff every three hours, until the River Forecast Center staff determines that the potential for flooding above plant grade no longer exists. Once the River Forecast Center staff declares that a Stage I Warning Plan threshold has been reached, AOP-N.03 requires implementation of surveillance instruction O-SI-OPS-244-215.0. The surveillance instruction ensures that these communications can be established and maintained between the SQN control room operators and the River Forecast Center staff in the REOC once every three hours.

12.0 AHPB RAI Question 12 On page 30 of 39 of the LAR, the licensee states, "... lower forecast threshold warning flood 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-flood transition interval is always available." Who makes this decision, on what basis? Will the emergency action level notifications move forward in concert with the warning(s)?

12.1 TVA Response - AHPB RAI Question 12 The River Forecast Center staff within the TVA River Operations organization, under the direction of the River Scheduling Lead Engineer, is responsible for determining when Stage I and Stage II Flood Warnings are to be issued. Prior to declaring a Stage I or Stage II Flood Warning at the SQN site, the River Forecast Center continuously monitors rainfall and monitors the headwater elevation behind the upstream dams, and upon predicting a critical headwater elevation for each dam based on observed rainfall the River Forecast Center staff makes notification based on the River Operations Emergency Response Plan to the Asset Owner for River Operations non-power assets (the TVA River Scheduling General Manager). This notification includes the time at which the critical headwater elevation is forecasted to occur. The Asset Owner (i.e., the responsible person for 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 the Page 14 of 29

ENCLOSURE1 RESPONSE 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 in the HESCO modular flood barriers at Cherokee Dam, Fort Loudoun Dam, Tellico Dam, and Watts Bar Dam as described in TVA River Operations Cherokee Dam, Fort Loudoun/Tellico Dams, and Watts Bar Dam Emergency Action Plans (EAPs). These actions take place at predicted flooding conditions below those required for a Stage I or Stage II Flood Warning at the SQN site, which allow for early prediction of meeting Stage I and Stage II Flood Warning threshold levels.

If the River Forecast Center staff observes a specified critical headwater elevation behind the dams, the Asset Owner (i.e., the responsible person for operations of the affected dam) is notified of the flooding condition. The Asset Owner declares a dam safety emergency - Condition YELLOW (based on TVA River Operations procedure RO-SPP-35.1) and notifies the REOC. The REOC goes to 'activation' status. The REOC Incident Support Staff supports site activities throughout activation of the REOC.

The River Forecast Center maintains an ongoing forecast of reservoir levels for a 14-day period. The forecast (prediction) is based on normal forecasting processes utilized by the River Forecast Center on a daily basis for forecasting reservoir flows and elevations for multiple purposes, including flood control, as described above 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 reaching the Stage I and Stage II Flood Warning thresholds. The initial trigger point for activation of the REOC is based on predicted headwater elevations at each dam. Therefore, it would be possible for the River Forecast Center to forecast the rain events and predict the trigger headwater elevations up to days in advance. Thus, early declaration of Stage I and Stage II Flood Warnings are possible for these situations.

The requirements for the final Stage I and Stage II Flood Warning determinations are addressed by the TVA River Scheduling Notification Directory, a desktop instruction that is maintained by TVA River Scheduling for use by the River Forecast Center staff during emergencies. For SQN, a primary number and an alternate number are provided to ensure that the SQN control room supervision is notified regarding potential flooding events. The TVA River Scheduling Notification Directory includes criteria for early warning as well as for Stage I and Stage II Flood Warning thresholds being reached. The early warnings include notification that the REOC is activated for either a flood condition, or for a dam 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 the interim if "Emergency Condition Red" (i.e., emergency classification that represents a very serious situation where failure of a dam has already occurred or is imminent) exists for a SQN-critical dam prior to activating the REOC.

A Stage I Flood Warning is issued when the specified SQN threshold flood warning level for 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. A Stage II Flood Warning is issued when the specified SQN threshold flood warning level of elevation 703 ft (2 ft below plant grade elevation 705 ft) is predicted to be exceeded at SQN 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 in the TVA River Scheduling Notification Directory, which includes the following:

Page 15 of 29

ENCLOSURE1 RESPONSE 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 River Forecast Center staff would be required to take the following actions:

a. An Early Warning is immediately issued to SQN control room supervision (at the specified primary and alternate numbers) of a dam safety "Emergency Condition Red" (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 />) involving a SQN-critical dam, and interim communications are maintained using a specified interim phone number prior to activating the REOC.

b. An Early Warning is immediately issued to SQN control room supervision when the REOC is activated by River Forecast Center staff for flood conditions and/or for a dam safety emergency involving a SQN-critical dam.

c. Communications are maintained with SQN control room supervision on at least three-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. If analyses show that elevation 703 ft would not be exceeded at SQN, the SQN control room supervision is immediately notified that the potential for site flooding no longer exists. SQN control room supervision is directed by AOP-N.03 to immediately proceed to a Stage I Flood Warning if communications are not established with the River Forecast Center staff within five hours of receiving an Early Warning. SQN control room supervision is directed by AOP-N.03 to continue onto Stage II Flood Warning shutdown procedures within ten hours of beginning Stage I Flood Warning preparations unless the River Forecast Center staff notifies SQN 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 SQN control 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 site could exceed elevation 703 ft.

f. If necessary, a Stage II Flood Warning is declared and communicated to SQN control 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 site could exceed elevation 703 ft.

g. SQN control room supervision is immediately notified and flood warnings are rescinded 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 /> or more above Chattanooga, Tennessee), with no critical dam failure or dam safety emergencies, the River Forecast Center staff would be required to take the following actions:

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 the REOC is activated for flood conditions and/or for a dam safety emergency involving a SQN-critical dam.

Page 16 of 29

ENCLOSUREI RESPONSE 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 least three-hour intervals (or more frequently, if needed).

d. SQN control room supervision is notified of conditions (rainfall and flood predictions) and that the REOC has been activated.

e. If necessary, a Stage I Flood Warning is declared and communicated to SQN control room supervision when flood level at the site, based on rainfall on the ground, is forecast to reach the appropriate threshold flood warning levels for the season of the year. SQN control room supervision is directed by AOP-N.03 to immediately proceed to a Stage I Flood Warning if communications are not established with the River Forecast Center staff within five hours of receiving an Early Warning. SQN control room supervision is directed by AOP-N.03 to continue onto Stage II Flood Warning shutdown procedures within ten hours of beginning Stage I Flood Warning preparations unless the River Forecast Center staff notifies SQN 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 SQN control 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 the site, 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 hour3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br /> notice 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 Flood Warning are maintained.

h. SQN control room supervision is immediately notified and flood warnings are rescinded 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 major maintenance), SQN control room supervision requires extra warning regarding flood conditions. In Mode 5 or 6, extra time would be needed to establish open mode cooling. To ensure sufficient awareness, SQN management and the River Forecast Center staff discuss dates for refueling or major maintenance in advance of scheduled outages, and communicate at least once per day during this condition to notify the River Forecast Center staff of plant outage configuration and expected time to complete outage. SQN management notifies the River Forecast Center staff when this plant configuration is no longer applicable.

During refueling or major maintenance, the River Forecast Center staff provides SQN control room supervision with an assessment of forecasted river elevations based both on rainfall on the ground and "maximum" rain forecast. As directed by the TVA River Scheduling Notification Directory, the River Forecast Center forecast indicates whether or not the expected river elevation will exceed elevation 703 ft within the next 99 hours0.00115 days <br />0.0275 hours <br />1.636905e-4 weeks <br />3.76695e-5 months <br /> to provide additional warning time regarding predicted flood conditions. If heavy rain develops or is forecast, the River Forecast Center staff notifies SQN control room supervision 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 ifapplicable.

Page 17 of 29

ENCLOSURE1 RESPONSE 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 is required then the actions of AOP-N.03 are implemented. AOP-N.03 requires the SQN control room supervisors to evaluate Emergency Plan Implementing Procedure EPIP-1, "Emergency Plan Classification Matrix," to determine the emergency action level requirements. EPIP-1 requires declaration of a Notification of Unusual Event whenever river reservoir level is at Stage I Flood Warning as reported by the River Forecast Center staff, and declaration of an Alert whenever river reservoir level is at Stage II Flood Warning as reported by the River Forecast Center staff. Therefore, the emergency action levels reflect actual Stage I and Stage II Flood Warning declarations by the River Forecast Center staff regardless of the actual flood elevations existing at the SQN site.

13.0 AHPB RAI Question 13 On page 32 of 39 in Enclosure 1 of the LAR, the assumptions for initial conditions in the flood plan include plants at 100 percent power. Are there any plant modes other than 100 percent 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 power level? Are the timing estimates for Stage I and Stage II actions the same regardless of the age of the core (i.e., rapid shutdown will take the same amount of time whether the plant's core is at end-of-life or is a fresh full-core refueling)?

13.1 TVA Response - AHPB RAI Question 13 In accordance with AOP-N.03, after initial flood mode preparation actions that are not dependent on the mode of operation for each of the two units, subsequent actions are taken on a per unit basis depending on initial plant operating Mode as defined by the SQN Technical Specifications. For operation in Modes 1 or 2 at any power level, upon issuance of a Stage I Flood Warning, actions are taken to initiate plant shutdown to Mode 3 or 4 in accordance with AOP-C.03, or general operating instruction 0-GO-6, "Power Reduction from 30% Reactor Power to Hot Standby." When the unit is in Mode 3, Reactor Coolant System (RCS) cooldown is completed to Mode 4 in accordance with general operating instruction 0-GO-7, "Unit Shutdown From Hot Standby to Cold Shutdown," or Emergency Operating Procedure ES-0.2, "Natural Circulation Cooldown." The requirements for shutdown 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 a Shutdown 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 River Forecast Center staff, under the direction of the River Scheduling Lead Engineer. If the unit is initially in Modes 1, 2, 3, or 4, AOP-N.03 directs completion of Stage I Flood Warning 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 Flood Warning. Stage II Flood Warning preparations then include actions to maintain the unit in Mode 4 to preserve use of the steam generators for core cooling, and these actions can 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 above plant grade is possible. An additional three hours are available for contingency margin before wave runup from the rising flood might enter the buildings.

AOP-N.03 also provides separate unit-specific actions for any unit in Mode 5 (Cold Shutdown), Mode 6 (Refueling), or if the core is empty. In Mode 5 or 6, extra time would Page 18 of 29

ENCLOSURE1 RESPONSE 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 preparation times are longer if the unit is initially in Mode 5 or 6, but the actions can be performed independently 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 for each 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 the specific example for SQN Unit 1 being in the middle of refueling (Mode 6) and SQN Unit 2 at some intermediate power level (i.e., in Modes 1 or 2), the time for Unit 1 to complete flood mode preparations would be longer than the time for Unit 2. This is the result of the larger number of actions required by AOP-N.03 for a unit initially in Mode 6, because the RCS and core may be in various alternative configurations initially, and transition to open mode cooling or removing fuel from the core would be required. The actual time to reach Mode 4 during a Stage I Flood Warning is greater for a unit at 100% power than at a power level less than 100%, because of the difference in the amount of time spent in procedures 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 I flood mode preparations is met at any initial power level. The performance time for AOP-C.03 is the same regardless of the amount of time the unit has been at power.

14.0 AHPB RAI Question 14 On page 14 of 39 of the LAR, it is stated that low water levels at the plant intakes could be experienced 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 there a plan or procedure in place that addresses the loss of heat sink? What alerts are available to cue the operators that a loss of heat sink is underway? How long after the failure of the dam would operators be aware that a loss of heat sink may be underway?

14.1 TVA Response - AHPB RAI Question 14 AOP-N.04, "Break of Downstream Dam," addresses the loss of the downstream dam.

Because Chickamauga Dam flows and hydroelectric power production are controlled by TVA, notification of a failure of Chickamauga Dam is received from the TVA Transmission Operator. SQN control room supervision verifies failure of Chickamauga Dam with either the TVA Hydro Dispatch Center or TVA Transmission Operator using specified phone numbers. In addition, requirements for River Forecast Center staff, under the direction of the River Scheduling Lead Engineer, to immediately notify SQN control room supervision of the failure of Chickamauga Dam, are addressed by the TVA River Scheduling Notification Directory, a desktop instruction that is maintained by TVA River Scheduling for use by the River Forecast Center staff during emergencies. For SQN, a primary number and an alternate number are provided to ensure that the SQN control room supervision is notified of predicted or actual failure of Chickamauga Dam. Therefore, because of the different and independent methods of notification, and capability for SON control room supervision 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 room supervision within minutes.

In the event of loss of Chickamauga Dam, the TVA River Scheduling Notification Directory requires TVA River Scheduling to provide an instantaneous minimum flow (from the upstream 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 dam Page 19 of 29

ENCLOSURE 1 RESPONSE 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 the requirements proposed in the SQN LAR for maintaining minimum water level at SQN and the minimum flow requirement at the Essential Raw Cooling Water (ERCW) intake.

15.0 AHPB RAI Question 15 The Hydrologic Basis for Warning System section on page 17 of Enclosure 1 of the LAR discusses Stage I and Stage II and the times associated with each stage. How was the time 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)? If determined by the walkdown, was a full complement of required personnel involved?

Clarify how this integrates with the emergency plan (e.g., whether the emergency plan call-in methods will provide enough people to implement the flood plan(s) in enough time).

15.1 TVA Response -AHPB RAI Question 15 The total preparation time for both Stage I and Stage II Flood Warning actions are evaluated in the updated hydrologic analysis to ensure margin exists for both the limiting rainfall-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 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 plant grade is possible.

An additional three hours are available for contingency margin before wave runup from the rising 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 (which includes a three hour additional margin), so that unnecessary economic consequences can be avoided, while providing adequate time for preparing for operation in the flood mode. Stage I allows preparation steps causing minimal economic consequences to be sustained but postpones major economic damage to the plant until a Stage II warning that predicts a likely forthcoming flood above plant grade. If the flood does not develop beyond a Stage I warning, major economic damage is avoided.

As described in the SQN LAR, steps needed to prepare the plant for flood mode operation can 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 above plant grade is possible. An additional three hours are available for contingency margin before wave runup from the rising flood might enter the buildings. For rainfall-induced PMF events, an additional four hours is assumed for communication and forecasting computations by the River Forecast Center organization to translate rain on the ground to river elevations at the plant. Hence, the warning time plan provides for a minimum of 31 hours3.587963e-4 days <br />0.00861 hours <br />5.125661e-5 weeks <br />1.17955e-5 months <br /> from arrival of rainfall on the ground until elevation 703.0 ft could be reached for rainfall-induced PMF events. In the updated hydrologic analysis, the minimum 31 hours3.587963e-4 days <br />0.00861 hours <br />5.125661e-5 weeks <br />1.17955e-5 months <br /> for preparation time is assured to be available for rainfall-induced PMF events by establishing revised threshold flood warning levels. These threshold flood warning levels ensure 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 be reached for the most-limiting rainfall-induced PMF event, and for any event with different rainfall 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 limiting time interval for completing both Stage I and Stage II Flood Warning preparations non-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 longer Page 20 of 29

ENCLOSURE1 RESPONSE 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, an additional 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 Forecast Center staff has determined that a Stage I Flood Warning is required then the actions of AOP-N.03 are implemented. AOP-N.03 requires the SQN control room supervisors to evaluate EPIP-1, "Emergency Plan Classification Matrix," to determine the emergency action level requirements. EPIP-1 requires declaration of a Notification of Unusual Event whenever river reservoir level is at Stage I Flood Warning as reported by the River Forecast Center staff, and an Alert whenever river reservoir level is at Stage II Flood Warning as reported by the River Forecast Center staff. As previously discussed in the response to AHPB RAI Question 5, a reasonable simulation was performed of the flood response AOP-N.03. Based on the reasonable simulation, there is assurance that the required personnel are available and capable of implementing the Stage I and Stage II Flood Warning preparations within the required times.

16.0 AHPB RAI Question 16 The licensee states on page 27 of 39 of Enclosure 1 of the LAR, "As a part of TVA RO's flood control responsibilities, forecast and warning procedures have been established that reflect the updated hydrologic analyses." As part of the configuration control process for these procedures, is the SQN site included in the review and approval of technical changes?

16.1 TVA Response - AHPB RAI Question 16 TVA Intergroup Agreement TVA-IGA-09.002, "TVA Intergroup Agreement (IGA) Nuclear Power Group and River Operations," applies to personnel assigned to either TVA Nuclear Power Group or TVA River Operations. TVA River Operations works directly under the TVA Nuclear Quality Assurance Plan for nuclear quality-related or safety-related work in lieu of developing and maintaining a Nuclear Quality Assurance program in compliance with 10 CFR 50 Appendix B.

As described in TVA-IGA-09.002, the TVA Nuclear Power Group performs evaluations of the effect to the existing nuclear plant design basis flood analysis as a result of potential and existing river system operations and configuration changes. This is accomplished by requiring WVA River Operations to complete Attachment 1, Tennessee River System Configuration Change Checklist, at six month intervals (+/- 1 month). The purpose of this checklist is to provide early identification of changes in the configuration or operation of the Tennessee River Basin dam and river system that could potentially impact the TVA Nuclear Plants DBF analyses. This checklist applies to TVA dam projects at and upstream 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 Group Vice President of Nuclear Engineering. The TVA Intergroup Agreement also requires TVA River Operations to identify potential river system changes affecting the Attachment 1 checklist attributes and river system scope as early as possible (conceptual design stage or earlier). These actions ensure an adequate configuration control process for changes under the authority of TVA River Operations as they affect TVA Nuclear Power Group design and operations activities.

Page 21 of 29

ENCLOSUREI RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)

REQUEST FOR ADDITIONAL INFORMATION (RAI) 17.0 AHPB RAI Question 17 The "shortest warning time" is discussed in several sections of the application, but not quantified. What were the shortest possible warning times analyzed for Stage I and Stage II warnings? Begin at the time the operators in the SQN control rooms receive the warning.

17.1 TVA Response - AHPB RAI Question 17 The updated hydrologic analysis ensures margin exists for completing both the Stage I and Stage II Flood Warning preparations for both the limiting rainfall-induced PMF event and for the limiting seismically-induced dam failure flood event as discussed in the SON LAR. The "shortest warning time" for the limiting rainfall-induced PMF event is 31 hours3.587963e-4 days <br />0.00861 hours <br />5.125661e-5 weeks <br />1.17955e-5 months <br /> from 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 /> 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). The "shortest warning time" 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 the failure of the failure of the dams until the flood wave reaches elevation 703 ft at SON. The methods used to evaluate these two scenarios are described in SON UFSAR Subsection 2.4.14, and in Enclosure 1 of the SON LAR on pages 25 through 30 for large rainfall floods, and pages 30 through 32 for seismically-induced dam failure floods, as further described below.

For large rainfall floods, the warning time is assured by declaring Stage I and Stage II Flood Warnings based on rainfall on the ground, and not based upon actual river elevations at SON. The analysis described in SON UFSAR Subsection 2.4.14 consists of evaluating nine hypothetical storms ranging from slightly more than five inches (equivalent to the largest flood event since regulation of flood-control on the Tennessee River valley by the use of TVA dams) up to probable maximum precipitation (PMP) events, and enveloped potentially critical areal, seasonal variations and time distribution of rainfall.

The warning time is based on those storm situations which resulted in the shortest time interval between watershed rainfall and reaching elevation 703.0 ft at SQN (2.0 ft below plant grade). The shortest warning time scenario for the winter was determined to be produced by the March 21,400 square mile downstream centered PMP with the heavy rainfall on the last day. The shortest warning time for the summer flood was produced by the 7,980 square mile June Bulls Gap centered PMP with the heavy rainfall on the last day. For each of these limiting scenarios, threshold flood warning levels were determined in the analysis as shown in Table 2 of Enclosure 1 of the SQN LAR. The River Forecast Center staff issues a Stage I Flood Warning to SQN control room supervision when flood level at the site, based on rainfall on the ground, is forecast to reach the appropriate threshold flood warning levels for the season of the year (i.e., those levels shown in Table 2 of Enclosure 1 of the SQN LAR). For any storm that results in less rainfall on the ground than the two shortest warning time storms, the actual time from start of the rainfall event to reaching Stage I Flood Warning threshold warning level, between reaching Stage I and Stage II Flood Warning threshold warning levels, and between reaching Stage II Flood Warning threshold level and actually exceeding actual plant grade at the site, would be greater. Therefore, the analysis verifies that margin exists for a significant increase in forecasted river elevations based on actual rainfall on the ground before a Stage I and Stage II Flood Warning would be required to be declared. This ensures that Page 22 of 29

ENCLOSURE1 RESPONSE 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 PMF event.

For seismically-induced dam failure floods, the warning time is based upon an analysis of possible dam failure combinations resulting from a seismic event with initial river levels significantly above the maximum operating levels. This includes five possible combinations of dam failures and initial river level conditions as described in SQN UFSAR Subsection 2.4.14. From this analysis, the flood wave travel times are determined to ensure there is adequate time between the seismically-induced dam failures and declaring Stage 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 II Flood Warning preparations and actually exceeding elevation 703 ft at SQN. The results of this analysis are shown in Table 3 of Enclosure 1 of the SQN LAR, and demonstrate that 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 the seismic dam failures and exceeding elevation 703 ft at SQN. This provides sufficient time for implementing the Stage I and Stage II Flood Warning preparations, ensuring that 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 I, 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 seismically-induced dam failure flood event.

18.0 AHPB RAI Question 18 In the UFSAR, Section 2.4.10, paragraph 3, it is stated, "Warning of seismic failure of key upstream 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 resulting flood surge would reach plant grade." What is the basis for this statement?

18.1 TVA Response - AHPB RAI Question 18 As discussed in the response to AHPB RAI Question 17, the limiting possible dam failure combination resulting from a seismic event with initial river levels significantly above the maximum 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 the seismic dam failure and exceeding elevation 703 ft at SQN. Therefore, the 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br /> required for implementing Stage I and Stage II Flood Warning preparations are assured.

19.0 AHPB RAI Question 19 If 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 19 As described in the response to AHPB RAI Question 12, once the River Forecast Center staff has determined that a Stage I Flood Warning is required then the actions of AOP-N.03 are implemented. AOP-N.03 requires the SQN control room supervisors to evaluate EPIP-1, "Emergency Plan Classification Matrix," to determine the emergency action level requirements. EPIP-1 requires declaration of a Notification of Unusual Event whenever river reservoir level is at Stage I Flood Warning as reported by the River Forecast Center, and an Alert whenever river reservoir level is at Stage II Flood Warning as reported by the River Forecast Center staff. Once entry is made into the actions Page 23 of 29

ENCLOSURE 1 RESPONSE 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 Plan Implementing Procedures to address the possibility of the loss of offsite power concurrent with design basis accidents and events, including external flooding. These procedures ensure that staffing, communications, and availability of required resources, are available for 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 a safe shutdown condition that is required by AOP-N.03. If either unit has not been placed in safe shutdown prior to external flooding exceeding plant grade, and the requirements of Emergency Operating Procedures for natural circulation cooldown (ES-0.2, ES-0.3, or ES-0.4) are in progress as a result of loss of off-site power, the additional actions required because of an external flooding event are addressed in AOP-N.03. Therefore, the combination of AOP-N.03 and the Emergency Operating Procedures ensure that the unit is maintained in a safe condition throughout the flooding event, even if off-site power is lost.

If offsite power has been lost, the Reactor Coolant System (RCS) cooldown would be performed using natural circulation. The Emergency Operating Procedure for natural circulation cooldown (ES-0.2) directs limiting cooldown rate to 50°F/hour, rather than the Technical Specification limit of 100°F/hr. Since RCS cooldown is required from normal operating temperature (547 0 F) to approximately 320 0 F, the time to complete the cooldown would 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 in the response to AHPB RAI Question 5, a reasonable simulation was performed for AOP-N.03. The time assumed in the simulation (300 minutes) encompasses use of natural circulation. Additionally, a loss of off-site power would result in loss of normal plant lighting, requiring use of portable lighting for flooding actions outside the Main Control Room and shutdown board room area. However, this portable lighting is available during emergency conditions.

Based on the above, the loss of off-site power during Stage I or Stage II Flood Warning preparations would not prevent completion of any required flood preparation actions within the required time limit.

Page 24 of 29

ENCLOSURE 1 RESPONSE TO NRC HEALTH PHYSICS AND HUMAN PERFORMANCE BRANCH (AHPB)

REQUEST FOR ADDITIONAL INFORMATION (RAI) 20.0 AHPB RAI Question 20 On 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 earth embankments could be overtopped during the PMF. Four dams were identified as having embankments that could be overtopped during the PMF: Cherokee; Fort Loudoun; Tellico; and Watts Bar." As a temporary measure, HESCO Concertainer units have been installed at each of the four dams. What organization was responsible for installing the HESCO Concertainers? Were they installed under an NRC-approved quality assurance program or equivalent, using controlled drawings, procedures, and documents? What barriers to human error were used (e.g., pre-job brief, independent verification, self-checking)?

20.1 TVA Response - AHPB RAI Question 20 The HESCO modular flood barriers were installed by the dam Asset Owner, which is TVA River Operations, in accordance with processes and procedures controlled by that organization. These processes and procedures include design controls used by TVA River Operations for configuration control of each of the dams for which TVA is the Asset Owner, and address implementation of design changes to the structural portions of the dams including the concrete dam sections and dam earthen embankments, including the HESCO modular flood barriers that are installed on top of the selected dam earthen embankments as discussed in the SQN LAR.

The configuration control of these four dams is both controlled and regulated by TVA River Operations, and does not fall under any NRC regulation. Therefore, the TVA River Operations processes and procedures that were used in the engineering, construction, and maintenance of the HESCO modular flood barriers are in compliance with TVA River Operations quality standards. These processes and procedures are not required to comply with 10 CFR 50 Appendix B Quality Assurance requirements, and the quality requirements met by the TVA River Operations processes and procedures are not NRC-approved, and do not require NRC approval. However, the quality standards used require the use of controlled drawings, procedures, and documents for implementing design changes including the installation of the HESCO modular flood barriers. In addition, periodic inspections are conducted, and maintenance performed, in accordance with TVA River Operations procedures to ensure the HESCO modular flood barriers were properly installed and remain in acceptable condition.

To ensure that the HESCO modular flood barriers are being maintained in an acceptable condition, the TVA Nuclear Power Group performs monthly inspections in accordance with procedures prepared and approved in accordance with the NRC-approved TVA Quality Assurance Program. These inspections verify the following:

a. Ensure the temporary HESCO flood barriers remain in place and are not structurally degraded as specified by the manufacturer's written specifications and recommendations;

b. Verify the inventory and staging of the material required to fill the gaps that exist; and Page 25 of 29

ENCLOSURE I RESPONSE 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 the staged material against theft.

These inspections will continue until the permanent modifications are implemented to prevent overtopping the Cherokee, Fort Loudoun, Tellico, and Watts Bar dams, previously committed to be complete by October 2015. The commitments for the inspections and permanent modifications were provided in the letter from TVA to the NRC, "Commitments Related to Updated Hydrologic Analysis Results for Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Unit 1,," dated June 13, 2012 (ADAMS Accession No. ML12171A053), and confirmed by the NRC in the letter to TVA, "Confirmatory Action Letter - Watts Bar Nuclear Plant, Unit 1, and Sequoyah Nuclear Plant, Units 1 and 2, Commitments to Address External Flooding Concerns (TAC Nos. ME8805, ME8806, and ME8807)," dated June 25, 2012 (ADAMS Accession No. ML12165A527).

21.0 AHPB RAI Question 21 On page 9 of 14 of Enclosure 2 of the LAR, the licensee states, "The maintenance of the temporary flood barriers and closure of openings during emergency events is a River Operations (RO) - Asset Owner (AO) responsibility, as defined by Dam Safety procedure RO-SPP-27.0." What is the sequence-of-events regarding the RO's closure of openings during emergency events in relationship to the site flood plan? What alerts the RO to close the openings and how long will it take? What credible errors are associated with the HESCO temporary barriers or their closure during a flood event?

21.1 TVA Response - AHPB RAI Question 21 Detailed plans for closure of the public access (PA) gaps in the HESCO modular flood barriers at Cherokee Dam, Fort Loudoun Dam, Tellico Dam, and Watts Bar Dam (including triggering hydrologic conditions) are fully described in TVA River Operations Cherokee Dam, 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 four dams) is notified by River Forecast Center staff when triggering headwater elevation is forecast for each dam (based on observed rainfall). Construction crews begin mobilizing to stage equipment and personnel at the sites to be prepared for closure of the PA gaps in the HESCO modular flood barriers. The triggering headwater elevations are as follows:

Dam Elevation (ft)

Watts Bar 747 Tellico 816 Fort Loudoun 816 Cherokee 1075 Page 26 of 29

ENCLOSURE 1 RESPONSE 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 staff when a second, higher triggering headwater elevation is forecast for each dam (based on observed rainfall). The construction crews then proceed to close the PA gaps in the HESCO modular flood barriers in accordance with the EAPs. The second, higher triggering headwater elevations are as follows:

Dam Elevation (ft)

Watts Bar 748 Tellico 817 Fort Loudoun 817 Cherokee 1076 An evaluation of the ability to close the PA gaps in accordance with the EAPs is described in TVA letter to NRC, "Potential for Breaches of HESCO Modular Flood Barriers and Earthen Embankments Affecting the Updated Hydrologic Analysis Results for Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Unit 1," dated January 18, 2013 (ADAMS Accession No. ML13025A262). Additional details can be found in this previous submittal, and the following discussions are based on this evaluation.

Reasonable simulations were performed to validate representative portions of the TVA River Operations Cherokee Dam, Fort Loudoun/Tellico Dams, and Watts Bar Dam EAPs on December 11, 2012. During these simulations, required personnel were mobilized, reported, and closed selected representative PA gaps in the HESCO modular flood barriers prior to the calculated time that headwater elevations would reach the base of the HESCO modular flood barriers at each site during an actual PMF event. Additionally, EAP specified equipment was mobilized, delivered, and utilized in the required time.

Following the guidance provided in the EAPs, a timed reasonable simulation was performed in order to verify that time dependent activities were achievable and required resources were available. This reasonable simulation included prediction of critical headwater elevations by River Forecast Center staff, notification of required personnel, mobilization of required personnel and equipment at the affected dams, and construction of HESCO modular flood barriers for selected PA gap closures (Watts Bar Dam PA-3 and portion of Fort Loudoun Dam PA-2).

The specific steps of the respective EAPs simulated, including initial and followup notifications and communications between TVA and contractor organizations and actual construction of the HESCO modular flood barriers by the contractor, are discussed in the previous submittal. The observations and conclusions from these reasonable simulations include the following:

Required resources (personnel, equipment, and material) as described in each 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 inventory of materials. Additionally, the ability of the EAPs to be effectively implemented by TVA and contractors was validated for the specific simulations performed.

Page 27 of 29

ENCLOSURE 1 RESPONSE 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, and accessibility was deemed acceptable. It should be noted that some gap locations provide 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 the HESCO modular flood barriers. However, the simulation verified that there is sufficient margin available to account for these delays.

• The River Forecast Center river forecasts routinely incorporate predicted rainfall, and can accurately predict river elevations that would occur ifthe rainfall event happened as forecast over the next 10 days. There are various postulated 9-day rain events which result in the need for the HESCO modular flood barriers to prevent dam embankment overtopping. The trigger point for notification of HESCO modular flood barrier construction crews and equipment is based on predicted headwater elevations at each dam. Therefore, it would be possible for the River Forecast Center staff to forecast the rain events and predict the trigger headwater elevations up to days in advance. Thus, prior to routes becoming impassible, notifications could be made to mobilize required equipment and personnel. Additionally, there are multiple roadways between major metropolitan areas and respective sites to transport personnel and equipment. This provides redundant roadways to access each site if one roadway were to become impassible. Therefore, it is concluded that mobilization of personnel and equipment would not be adversely restricted.

Based on the above discussion, it is concluded that any credible errors that could be encountered in closing the PA gaps in the HESCO modular flood barriers are adequately addressed in the EAPs and by the availability of resources including personnel, equipment, and material. The ability to implement procedures to close the gaps left for public access through the HESCO modular flood barriers (PA gaps) ensures the effectiveness of the modular flood barriers during a PMF event. A reasonable simulation verified that the required resources (personnel, equipment, and material) as described in each 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 inventory of materials. Additionally, the ability of the EAPs to be effectively implemented by TVA and contractors was validated for the specific simulations performed.

22.0 AHPB RAI Question 22 Will site personnel need to know the actual flood levels to perform any required actions in the flood plan or shutdown procedures? If yes, how will flood level be determined?

22.1 TVA Response - AHPB RAI Question 22 AOP-N.03 controls the overall timing and sequence of implementing actions for flood mode preparations and operations, and utilizes implementing work orders, general operating instructions, emergency operating instructions, flood preparation maintenance instructions, and other AOPs to complete the required actions by the applicable SQN site organizations. These procedures do not require the SQN control room supervision to know the actual flood levels in order to be successfully performed. In AOP-N.03, there is Page 28 of 29 I

ENCLOSURE1 RESPONSE 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 various doors to allow free flooding of lower elevations of the Control Building and Auxiliary Building when the water level rises above elevation 705 ft. This elevation is approximately equal to plant grade, so operators could reasonably determine when this action is needed without instrumentation or other accurate methods of measuring elevation. However, there is detailed flood level information including forecast levels from the River Forecast Center that can be made available to the SQN control room supervision upon request.

Page 29 of 29

ENCLOSURE2 TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT UNITS I AND 2 RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)

REQUEST FOR ADDITIONAL INFORMATION (RAI)

Subject:

Application to Revise Sequoyah Nuclear Plant Units I and 2 Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis, (SQN-TS-12-02) 1.0 SBPB RAI Question 1 The 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 building entrances. The application states that these sandbags are staged on-site.

Describe how the availability of sandbags in sufficient quantity will be ensured when required (i.e., inclusion in station procedures, etc.).

1.1 TVA Response - SBPB RAI Question 1 The installation of permanent plant modifications to protect the Diesel Generator Building entrances from a DBF, including future installation of permanent engineered flood barriers, has replaced the use of sandbag berms. These plant modifications and the required actions for installation of permanent engineered flood barriers are described in the response to SBPB RAI Question 2.

2.0 SBPB RAI Question 2 The LAR states that the licensee will install permanent plant modifications to provide adequate flooding protection with respect to the DBF level for the DG building, by March 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 not provided.

Describe the design of these permanent plant modifications and how they will provide adequate flooding protection for the DG building. The response should include any proposed UFSAR text changes reflecting flooding protection of the DG building.

2.1 TVA Response - SBPB RAI Question 2 As stated in the SQN LAR, the DBF including wind wave run up during the PMF event is elevation 723.2 ft, which is 1.2 ft above the Diesel Generator Building operating floor elevation of 722.0 ft. Therefore, TVA has installed plant modifications to provide flood protection with respect to this DBF level for the SQN Diesel Generator Building at several locations. Modifications include installation of flood protection barriers in the Diesel Generator Building at elevation 722 ft for equipment doors (D1-D4), personnel access Page 1 of 13

ENCLOSURE2 RESPONSE 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 the Toilet Room, and extension to the four external fuel fill ports for the seven day oil storage tanks.

The flood protection barriers for the equipment doors (D1-D4) are fabricated on-site, and consist of a steel plate attached to a framing angle that is welded to the inside of the door frames, as shown in Attachment 1. The equipment numbers for these flood protection barriers are SQN-0-BRR-634-DO01 through SQN-0-BRR-634-D004, respectively. These barriers ensure flood protection up to two feet above the DBF level. These flood barriers are 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. The barriers may be removed as needed when access is required to perform major maintenance. In such instances where the barrier might be temporarily removed, the flood barrier is placed in a storage location. During flood mode preparations, an action is required to retrieve the barrier and remount it to the framing angle. Lifting lugs mounted to the 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-shaped reinforced concrete berm that is an extension of the permanent structure, and is located inside the building between doors D5 and D6. The flood protection barriers for the emergency doors (D1 5-D18) consist of reinforced concrete berms that are extensions of the 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 to the 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 the line 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 was previously not required, because the ports although capped were located above the previous DBF level. Extension to the four external fuel fill ports to elevation 725.25 ft provides flood protection up to two feet above the DBF level allowing sufficient margin to remove 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 following discussion:

"Wind wave run up during the PMF at the Diesel Generator Building would reach elevation 723.2 ft which is 1.2 ft above the operating floor. Consequently, wind wave run up will impair the safety functions of the Diesel Generator Building. The accesses and penetrations below this elevation in the Diesel Generator Building are designed and constructed to minimize leakage into the building. Redundant sump pumps are provided within the building to remove minor leakage."

Because of the level of detail required in the SQN UFSAR, and because these modifications meet the flooding protection basic design requirement in the SQN UFSAR for the Diesel Generator Building as stated above, there are no other changes to the SQN UFSAR required.

Page 2 of 13

ENCLOSURE2 RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)

REQUEST FOR ADDITIONAL INFORMATION (RAI)

The above described plant modifications were complete on March 29, 2013. Additional plant modifications are planned to replace the flood protection barriers (reinforced concrete berms) for the personnel access door (D5) and emergency doors (D1 5-D1 8) with engineered flood barriers, as shown in Attachment 5. This will allow easier personnel and equipment access through these doors while ensuring adequate flood protection. These engineered 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, and D18, are manufactured and qualified by Presray Corporation. The products are the Fastlogs System and the FB33 System, although equal products from another manufacturer may be used in the place of Presray products. Door D5 will use the Fastlogs System, and Doors D15, D16, D17, and D18 will use the FB33 System. A door rack will be supplied at each location, and a storage rack will be provided as needed for the Presray products. The equipment numbers for these flood protection barriers are SQN-0-BRR-634-D005, and SQN-0-BRR-634-DO15 through SQN-0-BRR-634-DO18, respectively. During flood mode preparations, an action is required to retrieve the barriers and install them in accordance with the manufacturer's instructions.

3.0 SBPB RAI Question 3 The SQN UFSAR Section 2.4A.2.1, "Flooding of Structures," states that the DG building has redundant sump pumps to remove minor leakage.

Do the sump pumps discharge leakage from the DG building at a point higher than the revised DBF level? If not, provide information on how backflow through the discharge piping is prevented.

3.1 TVA Response - SBPB RAI Question 3 The Diesel Generator Building has two sump pumps (SQN-0-PMP-040-0079 and SQN-0-PMP-040-0080) installed in order to remove minor leakage. These pumps discharge leakage from the building through independent 2-inch lines with a centerline elevation of 732 ft, 8 inches at the highest point, as shown in Figure 1 below. As seen in Figure 1, the sump also includes an emergency 24-inch drain. AOP-N.03 includes steps to plug this 24-inch drain path.

Page 3 of 13

ENCLOSURE2 RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)

REQUEST FOR ADDITIONAL INFORMATION (RAI)

B2-92 Figure 1 - SQN Diesel Generator Sump Pump Discharge Line Elevations As stated in the SQN LAR, the DBF including wind wave run up during the PMF event is elevation 723.2 ft, which is 1.2 ft above the Diesel Generator Building operating floor elevation of 722.0 ft. Therefore, the discharge piping is approximately 9.4 ft above the DBF level.

4.0 SBPB RAI Question 4 The LAR states that heat removal from the steam generators will be accomplished using the 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 4 As described in SQN UFSAR Subsection 2.4.11.5.1, the fire/flood mode pumps are submersible pumps located in the Condenser Cooling Water Pumping Station. The Page 4 of 13

ENCLOSURE2 RESPONSE 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 to the suction pipes for the fire/flood mode pumps are at elevation 651 ft which is 32 ft and 24 ft, respectively, below the maximum normal water elevation of 683.0 ft and the normal minimum elevation of 675.0 ft for the reservoir. The fire/flood mode pumps and electrical components are designed to operate submerged at DBF levels, and are started from handswitches located in the main control room located above DBF levels. The control and pump motor power for the fire/flood mode pumps is located at elevation 734 ft in the Auxiliary Building, which is adequate to provide protection from the proposed DBF level in the Auxiliary Building in the SQN LAR (elevation 722.5 ft). Therefore, required components of the high pressure fire protection system are protected from the DBF levels.

5.0 SBPB RAI Question 5 The LAR states that the spent fuel pool cooling pump motors platform is located in an enclosure that provides flooding protection up to elevation 724.5 feet. The spent fuel pool cooling pump enclosure caps are required to be installed in order to provide flooding protection to this elevation.

Describe the physical design of the enclosure and how installing the caps will ensure flooding protection up to the 724.5 feet elevation. Will installing the caps impact the performance of the spent fuel pool cooling pumps? With the caps installed, can the spent fuel pool cooling pumps still be aligned for open reactor cooling as described in UFSAR Section 2.4A.2.2, "Fuel Cooling"?

5.1 TVA Response - SBPB RAI Question 5 The Spent Fuel Pit Cooling (SFPC) pumps are located on a platform at elevation 721.0 ft in the Auxiliary Building. The SFPC pumps are protected from flooding by Auxiliary Building walls on two sides and the SFPC pump enclosure constructed of steel plating on the other two sides. The SFPC pump enclosure provides protection up to a flood elevation of 724.5 ft (top of the two sides constructed of steel plating), which is adequate to provide protection from the proposed DBF level in the Auxiliary Building in the SQN LAR (elevation 722.5 ft). In addition, the SFPC pump enclosure contains redundant sump pumps connected to vital power (SQN-0-PMP-040-0077 and SQN-0-PMP-040-0078). The sump pumps are part of the original plant design, provide secondary protection from flood leakage into the enclosure, and provide additional protection from piping and pump accumulated leakage.

A design feature of the enclosure includes two 6-inch diameter drains located next to each other on the enclosure that are normally open during operation to allow any leakage from the SFPC pumps to drain to the normal Auxiliary Building drains as shown in Figure 2 below:

Page 5 of 13

ENCLOSURE 2 RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)

REQUEST FOR ADDITIONAL INFORMATION (RAI) 4" x 150# RF blind flanges Remove flanges and Install Spool Piece PLAN EL. 714 6" Cap with Chain (2 ea)

Section B-B (48W1216-6)

Figure 2 - SQN Spent Fuel Pit Cooling Pump Enclosure Caps These drains are capped as required by AOP-N.03 during Stage II Flood Warning preparations in accordance with maintenance instruction 0-FP-MXX-000-01 1.0, "Flood Preparation SFPC Pump Enclosure Caps, SFPCS Heat Exchangers, RCP Thermal Barrier Booster Pumps, and RHR Heat Exchanger Spool Pieces." The drains are located at the bottom of the enclosure near the floor elevation of 714.0 ft, the caps are attached to the drains by chains, and the drains are readily accessible during Stage II Flood Warning preparations. Installation of the caps does not affect the operation of the SFPC pumps in Page 6 of 13

ENCLOSURE2 RESPONSE 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 described in the SQN UFSAR.

6.0 SBPB RAI Question 6 The Sequoyah UFSAR flooding protection plan states that the penetrations of the reactor building, DG building, and essential raw cooling water intake station are designed to withstand the static and dynamic forces imposed by the DBF.

Do the penetrations of these structures continue to withstand the forces associated with the revised DBF and prevent leakage? Describe how the penetrations were evaluated for the revised DBF.

6.1 TVA Response - SBPB RAI Question 6 The SQN protection and mitigation features that are considered in the licensing basis evaluation to protect against external ingress of water into SSCs important to safety are described in SQN UFSAR Subsection 2.4.14, and assurance that SQN can be safely shut down and maintained in these extreme flood conditions is provided by the discussions given in SQN UFSAR Subsections 3.4, 3.8.1, 3.8.2, and 3.8.4. Based on the updated hydrologic analysis as described in the SQN LAR, the requirements described in SQN 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 Raw Cooling Water (ERCW) Building. On December 12, 2012, TVA determined that the ERCW Building may flood at the proposed DBF level due to conduit penetrations not being sealed with material capable of making the building watertight. The lack of a barrier would allow flood waters to enter the ERCW Building at a rate greater than the sump pumps can remove creating a condition that could result in the ERCW Pumps being unavailable to perform their design function during a flood event above plant grade. Corrective actions have been completed to replace the existing moisture barriers installed on the conduits in manhole 33 with a sealant that is designed and has been tested to withstand a larger amount of pressure.

As described in SQN UFSAR Subsection 3.8.1.3, the Shield Building cylinder wall is subjected to uplift forces and lateral static pressure computed using the full hydrostatic head measured from the water surface. The DBF elevations were used in determining hydrostatic heads. Due to water seals between the Shield Building and adjacent structures, the lateral hydrostatic pressure was applied only to one-half of the circumference for the design flood and maximum probable flood. For the PMF, the adjacent structures are allowed to flood, and lateral hydrostatic pressure was applied around the full circumference. Penetrations below the revised DBF level were assessed as the result of the extent of condition for the deficiency associated with the ERCW Building above. As a result of this review, it was determined that penetration seals below the DBF level may not be qualified as watertight seals. The evaluation of this condition is being tracked in the TVA Corrective Action Program.

As described in SQN UFSAR Subsection 3.8.4.1.1, pressure confining personnel access control doors located in the Auxiliary Control Building are required. The Page 7 of 13

ENCLOSURE2 RESPONSE 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 water tight annulus access doors (one per unit, doors A65 and A78), are secured during external flood warnings to prevent water intrusion into the annulus area.

SQN UFSAR Subsection 3.8.4.1.3 describes the structural design of the Diesel Generator building. See the response to SBPB RAI Question 2 for details of the plant modifications implemented to ensure adequate flood protection for the Diesel Generator Building.

Based on the above discussion, the structures, including penetrations, required to withstand the structural impacts of an external flood have been assessed, and are acceptable for the revised DBF levels with the exception of the conduit penetrations for the ERCW and Shield Building as described above.

Page 8 of 13

ENCLOSURE 2 RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)

REQUEST FOR ADDITIONAL INFORMATION (RAI)

ATTACHMENT 1 DIESEL GENERATOR BUILDING EQUIPMENT DOORS (D1-D4) FLOOD PROTECTION BARRIERS PI1C L3- i DCN--,iZfliO SEQUOYAH NUCLEAR PLANT DRAWING CHANGE AUTHORIZATION PAGE- _136 PAGE W*.1 RO.DELETED SEE CONST NOTE I ITS *t -- 540 aLtAIrIIO Be fl-O-41T-B0OI COJIAENI Attn L LI 'LOS SnAIL

• ~ S Si-Sn.LLOJ CAINIIIT LL(SS55 04 ItOS MUlti

• 04 W.L.SB-E34.LOSL ESISAWY ALLISLOSLI FOALBALLOtS ff E-41M- e

• a, n-*PB.Bfl-aOo, IOJIVENT01105, LI nfl PULL Y,'Ell RO. ADD 000 1zvp C..-

0-,

A-,Z

~04 ~'OOOS F

221~ -~

A.-

RD AD D RO, ADDb RO, ADD RO, ADD 2

d.*AF I NC NOTES (DOT TO BE INCORPORATED),

- FLOOD NARRIER UNIT S0N-0O-9RP-634-0DGI, -002. -00J AND -004 DELETED 0 ~ i-t(i...- V2/i2 DCN 22404 /PIC 23179 RtEV ,LNDO Chs..kO.d/U.t. C-HANCEREFERENCE FROM STAGCEI AND ADDED ON STACE 4 Of' THIS OCN (SEE OCA 22404-1302)

CONLTRACT NO N/ STAGE 4 J*3NSITRUCi/ONNXiS (NOT IDW E 1INCORPORATED)-

OCAPRERECUISITES NONE 16W418-2 REVE

., ID rO RE qF0OVED AND PIPES CAPPED SEE OCAS 22404-1304 Ti-/RU ERlN !506

$1/ CCOTNO N/A CAT __N/A DCA NO 22404-4806 JN1I 2 01siftlFOLt N/A Page 9 of 13

ENCLOSURE 2 RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)

REQUEST FOR ADDITIONAL INFORMATION (RAI)

ATTACHMENT 2 DIESEL GENERATOR BUILDING PERSONNEL ACCESS DOOR (D5) AND EMERGENCY DOORS (D15-D18)

CONCRETE BERM FLOOD PROTECTION BARRIERS I PIC_ 23179 DCN 22404 SEQUOYAH NUCLEAR PLANT DRAWING CHANGE AUTHORIZATION _A _._', PAGE I_O DETAIL A14 \-SEE DETAIL A14 PARTIAL PLAN - EL 722'-0" NOTES: NOTES: (CONTI I ALL CONCRETE MATERIALS AND WORKMANSHIP SHALL BE 16. TESTING SHALL COMPLY WITH SECTION B.8.4 OF GENERAL ENGINEERING IN ACCORDANCE WITH THE LATEST EDITIONS OF ACI 318 SPECIFICATION G-2 EXCEPT THAT ALL TESTING IS WAIVED IN AND ACT 301. ACCORDANCE WITH SECTION B.8.8.

2 ALL CONCRETE SHALL BE CLASS 300.75 AFW MIN. (3000 PSI) 17. CONCRETE MAY BE PURCHASED AUGMENTED DUALITY D10SEISMIC AND SHALL BE PLACED IN ACCORDANCE WITH GENERAL CATEGORY I(L).

ENGINEERING SPECIFICATION C-2. 18. NO ATTACHMENTS ARE PERMITTED TO DETAIL A14 AND/OR B14.

5 ALL EMBEDDED METALS TO CONFORM TO ASTM A36. UNLESS CALCULATION BRANCH/PROJECT OTHERWISE NOTED ON DRAWINGS. ALUMINUM SHALL NOT BE EMBEDDED IN CONCRETE UNLESS SPECIFICALLY APPROVED. REFERENCE DRAWINGS: IDENTIFIERS: CDO0009992013000045 ALL UNFORMED CONCRETE SURFACES SHALL BE STEEL TROWELLED, ION320-1 DIESEL GENERATOR BUILDING ALL MATERIALS SHALL BE OA LEVEL I UNLESS OTHERWISE NOTED. ION321-2 CONCRETE SLAB & WALL IN CONTACT WITH CONCRETE 16W418-2 UNIT 0 WATER BARRIER SHALL BE SCARIFIED TO A DEPTH Y4 ID A" AND COATED WITH AN APPROVED BONDING AGENT PER GENERAL CONSTRUCTION NOTES: (NOT TO BE INCORPORATED)

ENGINEERING SPECIFICATION C-34. 1. WORK THIESDCA WITH DCA 22404-4807. -4810 AND -4311, CONCRETE FLOOD BARRIERS I REINFORCING STEEL SHALL BE ASTM A615 GR, 60 DIESEL CEN - EL. 722.0' 3 CHAMFER ALL EXPOSED CONCRETE EDGES -", PLAN, SECTIONS & DETAILS DIMENSIONAL TOLERANCE FOR REINFORCEMENT PLACEMENT IS */- )",

UNLESS NOTED 13 (I DENOTES IN PLACE CONCRETE.

C(CUTTING REINFORCEMENT FOR GROUTED HOLES IS NOT ALLOWED ADDITIONAL VERTICAL REINFORCEMENT MAY BE INSTALLED TO MAINTAIN 2- MAXIMUM, 3' MINIMUM BAR SPACING.

SHOLESFOR GROUTED REINFORCEMENT TO BE I 5- DIAMETER & DRILLED 0 /~/) OC~...22404 DN /PIC 23179 TO A DEPTH 0 5- GREATER THAN BAR DEPTH REY P.o.4T)d Cch4.4d/0t CH'ANCE REFERENCE

1. ALL GROUT TO BE NON-SHRINK WITH A MINIMUM STRENGTH = 3000 PSI I- CONCRETE SHALL CONTAIN FIBER REINFORCEMENT MEETING THE CONTRACT NO:. STAGE AFFECTEDBATEDRAWINGNO ADMREV REOUIREMENTS OF ASTM C1116. SECTION 4 1.3 TYPE Ill. AND NOTE 2 NEW DRAWING (ANT)

DOSAGE SHALL BE 2.5-3 LB/CU.YD Dc,' PWTntouJiTsms NONE MASTERFIBER FlOG ENHANCED FIBRILLATED POLYPROPYLENE FIBER CCDNO ANT 0iON321-14 CAI 4 TANUFACTURED BY BASE IS ACCEPTAB! [ TO US ANTFIBER REINFORCEMENT CIVIL OCA NO 22404-480 UNII:T

. D 0IYCIPLOI. ,_

_____________________________________________________ L L Page 10 of 13

ENCLOSURE 2 RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)

REQUEST FOR ADDITIONAL INFORMATION (RAI)

ATTACHMENT 3 DIESEL GENERATOR BUILDING WASTE LINE MODIFICATION FOR FLOOD PROTECTION SEQUOYAH NUCLEAR PLANT DRAWING CHANGE AUTHORIZATION PAGE DCN 22404 Sk ADD SEEGONS'T NOTES F1 -Fl stl,*J-o 0 4 jCN2404 REV P~p~./o.Ch..k. d/D. t. CHANGE REFERENCE CONTRACT NO: N/A STAGE 1 AFFECTEDBASEDRAWINGNO. AND REV 0 CONSTRUCTION NOTES: (NOT TO BE INCORPORATED)

1. REMOVE URINAL AND CAP DRAIN LINE WITH 2" DCA PREREOUISITES: NONE 17W710-1 REV A THREADED CAP MARK NO. A270.

2. WORK THIS DCA WITH DCA 22404-1501 & -1502 ANTccoNO: N/A CAT. N/.

0, DISCIPLINE N/A DCA NO. 22404-1503 UNIT: I Page 11 of 13

ENCLOSURE 2 RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)

REQUEST FOR ADDITIONAL INFORMATION (RAI)

ATTACHMENT 4 DIESEL GENERATOR BUILDING FUEL FILL PORTS MODIFICATION FOR FLOOD PROTECTION DCN 22404 SEQUOYAH NUCLEAR PLANT DRAWING CHANGE AUTHORIZATION IPAGE__l CONSTRUCTION NOTES: (NOT TO BE INCORPORATED) 1 . REMOVE COVER AND INTERNAL PLUG OF FILL PORT MARK #2+5

2. THREAD IN PIPE MARK #166.

3. ATTACH REMAINING ITEMS AS SHOWN.

NOTESADD o . .. ~.. $DCN 22404 REV Pr-P-rd/Oot. Chk..A o . Oq CHANCE REFERENCE A) 0 0 PLUG CONTRACTNO: N/A STAGE 1 AFFECTEDBASE DRAWINGNO. AND REV THREADED CONNECTION, THREADED (MARK #245) TOINTERNAL PORT CONNECTION HAVE AN APPROVED 0* THREAD INTO FILL OCA PREREOUISITES: NONE 1,2-17W585-3 REV 0 THREADTOSEALANT. FILL PORT COVER & INTERNAL PLUG TO BE INTSPIPE ANT CCD NOt N/A CAT, N/A DISCIPLINE N/A OCA NO. 22404-1500 UNIT: 0 Page 12 of 13

ENCLOSURE 2 RESPONSE TO NRC BALANCE-OF-PLANT BRANCH (SBPB)

REQUEST FOR ADDITIONAL INFORMATION (RAI)

ATTACHMENT 5 DIESEL GENERATOR BUILDING PERSONNEL ACCESS DOOR (D5) AND EMERGENCY DOORS (D15-D18)

ENGINEERED FLOOD PROTECTION BARRIERS SEQUOYAH NUCLEAR PLANT DRAWING CHANGE AUTHORIZATION PAEN z RO, DELETED--.

SEE CONST NOTE 3 -

L'jASOA RO, AD! D----l

.1. EI*4-O*IOt-g*I-EOtHA

• FQRgl (10t.)

0*,r0flQ-0,. 722 4.4 jF~ 7 RIP lT--A-AT EE AS (LATER)

U- tA W ESC-S OA5)2 -sAR LTIR

• I MA 30 EO .S A RM(ATR EIasA flOf-t1-tS( PSR4 PARC ImSwm .P (LATERI

• ITAn..n)EET MC rw Al (LATE) 4 EISA 00-A-KE - .VAlt P MEC MR (UtERI P51117 EMS l F-7TERRERRR 4

2 _________________________

.0 1 1________________

Ao CONSTRUCTION NOTES (NOT TO BE INCORPORA TED): 0 Z.; L OCN 22404 0 1. FIELD TO LOCATE STORAGE RACKS AS SHOWN. SOME LOCATIONS REoUIRE REV P-p-d/S8DEIR CIIS.k~iACEI I KANGEREFERENCE EXISTING ComDITIES TO BE RELOCATED.

CONTRACTNO: N/A STAGE 1 AFFECTEDBASE DRAWINGNO. AND REV 0 2. STORAGE RACK FOR FBJ3 PANELS ARE AN ADDITIONAL SET OF JAMB BRACKETS AMOUNTEDTO WALL. DCA PREREQUISITES: NONE 16W418-2 REV D VO 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. ANT CCo NO: N/A CAT. N DISCIPLINE N/A DCA NO. 22404-1801 UNIT: 1 a a Page 13 of 13