CNL-13-125, Response to NRC Request for Additional Information Related to Overall Integrated Plan in Response to the Commission Order Modifying Licenses with Regard to Requirements for Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051)

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Response to NRC Request for Additional Information Related to Overall Integrated Plan in Response to the Commission Order Modifying Licenses with Regard to Requirements for Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051) (
ML13333B282
Person / Time
Site: Watts Bar  Tennessee Valley Authority icon.png
Issue date: 11/22/2013
From: James Shea
Tennessee Valley Authority
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
CNL-13-125, TAC MF0951, TAC MF1178
Download: ML13333B282 (23)
v • d • e


Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 CNL-13-125 November 22, 2013 10 CFR 2.202 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Watts Bar Nuclear Plant, Unit 1 Facility Operating License No. NPF-90 NRC Docket No. 50-390 Watts Bar Nuclear Plant, Unit 2 Construction Permit No. CPPR-92 NRC Docket No. 50-391

Subject:

Response to NRC Request for Additional Information Related to Overall Integrated Plan in Response to the Commission Order Modifying Licenses with. Regard to Requirements for Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051) (TAC Nos. MF0951 and MF1178)

References:

1. NRC Order Number EA-12-051, "Issuance of Order to Modify Licenses with Regard to Reliable Spent Fuel Instrumentation,"

dated March 12, 2012

2. Letter from TVA to NRC, "Tennessee Valley Authority (TVA) - Overall Integrated plan in response to the March 12, 2012, Commission Order Modifying Licenses with Regard to Requirements for Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051) for Watts Bar Nuclear Plant," dated February 28, 2013
3. Letter from TVA to NRC, "Watts Bar Nuclear Plant, Units 1 and 2 - Request for Additional Information Regarding Overall Integrated Plan in Response to the Commission Order Modifying Licenses with Regard to Requirements for Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051)

(TAC Nos. MF0951 and MF1 178)," dated August 2, 2013 Printedon recycledpaper K

U.S. Nuclear Regulatory Commission Page 2 November 22, 2013

4. Letter from TVA to NRC, "Response to NRC Request for Additional Information Related to Overall Integrated Plan in Response to the Commission Order Modifying Licenses with Regard to Requirements for Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051)

(TAC Nos. MF0951 and MF1178)," dated September 6, 2013

5. Letter from NRC to TVA, "Watts Bar Nuclear Station Units 1 and 2 - Interim Staff Evaluation and Request for Additional Information Regarding the Overall Integrated Plan for Implementation of Order EA-12-051, Reliable Spent Fuel Pool Instrumentation (TAC Nos. MF0951 and MF1 178)," dated October 24, 2013
6. Letter from TVA to NRC, "Change to Commitment Date Regarding Response to NRC Request for Additional Information Related to Overall Integrated Plant in Response to the Commission Order Modifying Licenses with Regard to Requirements for Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051) (TAC Nos. MF0951 and MF1178)," dated October 29, 2013 On March 12, 2012, the Nuclear Regulatory Commission (NRC) issued Order EA-12-051, which directed holders of operating licenses under Title 10 of the Code of Federal Regulations (CFR), Part 50, "Energy," to provide for reliable spent fuel pool indications and submit to the NRC for review an overall integrated plan (OIP), including a description of how compliance with the requirements described in Attachment 2 of the Order would be achieved, by February 28, 2013 (Reference 1). The Tennessee Valley Authority (TVA) submitted the OIP for Watts Bar Nuclear Plant (WBN), Units land 2, on February 28, 2013 (Reference 2).

On August 2, 2013, the NRC issued a Request for Additional Information (RAI) letter regarding the OIP submitted by TVA for WBN, Units 1 and 2 (Reference 3). TVA provided a response to a portion of the Reference 3 RAIs on September 6, 2013 (Reference 4). In Reference 4, TVA committed to provide a response for the remainder of the Reference 3 RAIs by October 31, 2013, after issuance of the design change package.

The NRC issued a second RAI letter on October 24, 2013 (Reference 5). Reference 5 repeated and included the Reference 4 RAIs which TVA committed to respond by October 31, 2013. The Reference 5 RAI requested a response be provided by November 22, 2013. To resolve the conflict between the Reference 4 and Reference 5 RAI response due dates, TVA submitted a letter to NRC on October 29, 2013 (Reference 6),

changing the Reference 4 commitment date to November 22, 2013, to provide one RAI response.

The purpose of this letter is to provide TVA's response to the Reference 5 RAI letter regarding WBN's OIP submitted to the NRC pursuant to Order EA-1 2-051, "Order Modifying Licenses with Regard to Reliable Spent Fuel Pool Instrumentation." Enclosure 1 of this letter provides TVA's response to the RAls submitted in Reference 5.

U.S. Nuclear Regulatory Commission Page 3 November 22, 2013 provides a list of commitments contained in Enclosure 1. If you have questions regarding this matter, please contact Kevin Casey at (423) 751-8523.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 22nd day of November 2013.

Res ully, J. .Shea(5 vic President, Nuclear Licensing

Enclosure:

1. Response to NRC Request for Additional Information Related to Overall Integrated Plan in Response to the Commission Order Modifying Licenses with Regard to Requirements for Reliable Spent Fuel Pool Instrumentation
2. List of Commitments cc (Enclosure):

NRC Regional Administrator - Region. II NRR Director - NRC Headquarters NRR Project Manager - Watts Bar Nuclear Plant, Unit 1 NRR Project Manager - Watts Bar Nuclear Plant, Unit 2 NRC Senior Resident Inspector - Watts Bar Nuclear Plant, Unit 1

ENCLOSURE1 TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT, UNITS I AND 2 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION RELATED TO OVERALL INTEGRATED PLAN IN RESPONSE TO THE COMMISSION ORDER MODIFYING LICENSES WITH REGARD TO REQUIREMENTS FOR RELIABLE SPENT FUEL POOL INSTRUMENTATIONRAI-1 Pleaseprovide the results of the calculation used to determine the water elevation necessary for the pump's requiredNPSH to confirm that Level I has been adequately identified.

TVA Response Watts Bar Nuclear Plant (WBN) calculation EPM-JPJ-07-192 documents adequate net positive suction head (NPSH) at elevation 749.125 feet (normal pool level) for Spent Fuel Pool (SFP) temperatures up to 190 degrees Fahrenheit (F). Refer to Sketch 1 on page E1-18. During a BDB-EE, as temperatures rise above 190 degrees F, WBN will control by procedure the throttling of pump discharge to ensure adequate NPSH. The calculation detailing this throttling requirement for BDB-EE has not been issued at this time. WBN has documented this action in the Corrective Action Program Problem Evaluation Report (PER) 770244 and the scheduled completion of calculation and procedure update is by February 21, 2014. Access to SFP pumps, heat exchangers, and valves can be achieved from the Shutdown Board Room, shown in sketch 1, on elevation 757 through the Auxiliary Building access point and down the central stairway to elevation 737 or from the Auxiliary Building access point on elevation 713 and up the north or central stairway to elevation 737. Valves that would require manipulation based on which train of SFP cooling being restored are located in the center south area of elevation 737.

RAI #2 Please provide additionalinformation regardingthe distance defined by the manufactureras the dead zone. Specifically, please provide the exact distance where there is the potential that level changes won't be detected, while accounting for instrument measurement uncertainty.

TVA Response The un-measurable zone at the bottom of the probe is approximately 4 inches (including the anchor weight). The total un-measurable zone of the level sensor probe will be finalized upon completion of factory testing by December 23, 2013. The overall measurement range, including the un-measurable zone and measurement uncertainty provided by the manufacturer, were considered in the determination of the calibrated range of the instrument channels to provide level indication at all 3 levels required by Order EA-1 2-051. The top of the un-measurable zone at the bottom of the probe is at elevation 724.79 feet. See Sketch 1 on page E1-18.

RAI #3 Pleaseprovide a clearly labeled sketch or marked-up plant drawing of the plan view of the SFP area, depicting the SFP inside dimensions, the planned locations/placementof the primary and back-up SFP level sensors, and the proposed routing of the cables that will extend from the sensors toward the location of the local electronics cabinets and read-out/displaydevices in the main control room or alternate accessible location.

(This information was previously requested as RAI-2 in NRC letter dated August 2, 2013)

TVA Response E1-1 of 19

See Sketch 2 on page El -19, for plan view of the SFP area, depicting the requested information.

RAI #4 Pleaseprovide additionalinformation describing how the proposed arrangementof the SFP Guided Wave radarsensing cables and routing of the instrumentationcabling between the SFP and final mounting location(s) of the monitoring read-outpanels meets the Orderrequirements with respect to arrangementof the SFP level instrument channels in a mannerthat provides reasonableprotection of the level indicationfunction against missiles that may result from damage to the structure over the SFP.

TVA Response Physical separation of the primary and backup instrument channel signal cables to the extent practicable is the primary method used to provide reasonable protection of the level indication function against missiles that may result from damage to the structure over the SFP. The primary instrument channel sensor is mounted near the northwest corner of the SFP on the wall separating the spent fuel pool and the fuel cask loading area. From the sensor, the primary signal cable is routed away from the SFP (west) to the adjacent wall. The backup instrument channel sensor is mounted in the opposite side of the SFP in the southeast corner. From the sensor, the backup signal cable is routed away from the SFP (east) to the adjacent wall. This arrangement results in a physical channel separation of a distance greater than the longest length of a side of the SFP.

Additional missile protection is accomplished by providing shielding of the signal cables within the SFP area. The cables are routed outward from the sensor brackets at the pool to the adjacent wall penetrations within trenches cut in the concrete floor. Within the trenches, the cables are protected by unistrut. Further protection is provided by plate steel trench covers, which are secured to the SFP floor using expansion anchor bolts. A 12" (approximate) portion of the primary signal cable which is not routed within a covered trench is routed within a tube steel enclosure to provide shielding. The SFP walls and corners provide inherent missile protection for the level sensor cable within the pool.

Physical separation of the primary and backup instrument channel signal cables and power cables is maintained using Class 1E type trained separation, i.e., the primary channel cables are routed as train A cables, while the backup channel cables are routed as train B cables.

Further channel separation is achieved by maintaining unit separation, i.e., primary channel equipment is mounted within the Unit 1 structures, while backup channel equipment is mounted within Unit 2 structures.

RAI #5 Please provide the following:

a) The design criteria that will be used to estimate the total loading on the mounting device(s), including static weight loads and dynamic loads. Describe the methodology that will be used to estimate the total loading, inclusive of design basis maximum seismic loads and the hydrodynamic loads that could result from pool sloshing or other effects that could accompany such seismic forces.

b) A description of the manner in which the level sensor (and stilling well, if appropriate) will be attached to the refueling floor and/or other support structures for each planned point of attachment of the probe assembly. Indicate in a schematic the portions of E1-2 of 19

the level sensor that will serve as points of attachment for mechanical/mounting or electrical connections.

c) A description of the manner by which the mechanical connections will attach the level instrument to permanent SFP structures so as to support the level sensor assembly.

(This information was previously requested as RAI-3 in NRC letter dated August 2, 2013)

TVA Response a) All SFPIS equipment mounting is analyzed to maintain a minimum seismic capacity of high confidence of low probability of failure (HCLPF) equal to or greater than a RLGM of two times (2x) the safe-shutdown earthquake (SSE). To achieve a minimum HCLPF of 2x SSE at WBN, SFPIS SSCs are designed in accordance with plant seismic category I design requirements.

Applicable TVA design criteria documents are referenced below. The vendor has performed calculations to evaluate the structural integrity of the mounting brackets at the SFP. The model considers load combinations for the dead load, live load and seismic load on the bracket, where seismic loading is for two-times the safe shutdown earthquake (SSE). These loads are then compared to the allowable values of the applicable welds, bolts and members to determine the acceptability of the design.

Seismic The seismic loads are obtained from response spectra curves and damping values for the application. The following methodology was used in determining the stresses developed for the model:

  • Frequency analysis is performed to obtain the natural frequencies of the structure in all three directions.

" SSE response spectra analysis is performed to obtain member stresses and support reactions due to the self weight of the bracket and associated components in a seismic event.

  • Response spectra analysis results in each direction using SRSS method are then combined. The seismic results in all three directions are combined using SRSS and then combined with the dead load results in absolute values. The combined results are compared with the allowable stress values.

Sloshinq Because of the size and complexity of the spent fuel pool, and practical limitations in preparing a physical scale model suitable for seismic testing, the effects of water sloshing on the SFP level measurement are assessed with analytical methods. As part of work underway to address NRC Order EA-1 2-049, calculations are being performed to determine plant-specific times for spent fuel pool boiling to begin. To establish initial post-seismic pool conditions, calculation methods from TID-7204, Nuclear Reactors and Earthquakes, 1963, by the US Atomic Energy Commission, are being used to estimate the amount of water sloshed out of the pool by seismic motion. Using this methodology, bounding results for the sloshing effect will be determined and supplemented with alternative analysis methods (e.g. finite-element modeling tools) to make a qualitative assessment of the effects of seismic-induced fluid motion on the cable probe. Because some water can be ejected from a pool, it is necessary to assume that the probe interconnecting cable will become wetted or submerged in borated water. Reliable operation of the level measurement sensor with a submerged interconnecting cable will be demonstrated by analysis of previous Westinghouse testing of the cable and vendor's E1-3 of 19

cable qualification. Boron build up analysis will be performed to determine how boron build up on the probe would affect the sensor. This will be finalized for inclusion in the overall test report. Final vendor testing and qualification documentation is ongoing, but is scheduled for completion by December 23, 2013. By January 10, 2014, TVA will notify the NRC final vendor testing and qualification documentation for RAI #5 is available for review.

b) The level sensor cable assembly is suspended from a support bracket, which is secured to the refueling floor and/or spent fuel pool curb using concrete anchor bolts. The level sensor cable suspended in the SFP is attached to a threaded coupling, which is secured to a support bracket. The cable leading to the transmitter is also attached to the threaded coupling. The generic illustrations below depict these attachments.

CTRANSMITTER SFPSF TOP CURB ANDOR REFULIN FLOOR

.......... PPORTT M

CABLEPROBE c) See response to b) above E1-4 of 19

RAI #6 For RAI 5(a) above, please provide the results of the analyses used to verify the design criteria and methodology for seismic testing of the SFP instrumentationand the electronics units, including, design basis maximum seismic loads and the hydrodynamic loads that could result from pool sloshing or other effects that could accompany such seismic forces.

TVA Response Seismic loads resulting from the analyses performed for the cable probe mounting brackets are documented in the referenced Westinghouse calculations. Seismic loads resulting from the analyses performed for mounting of the instrument enclosures and transmitters are documented in the referenced TVA calculations. Seismic loads resulting from the analyses performed for the instrument enclosure and transmitter mounting is documented in Appendix B of the referenced TVA calculation.

Results of the seismic testing for the vendor supplied equipment are documented in section 5.1 of the referenced Westinghouse report. No equipment failures were noted as a result of the seismic test runs. Per section 7.2.1 of the referenced Westinghouse test strategy, a preliminary sloshing analysis calculation was conducted by the vendor. Seismic test data will be documented in a seismic test report upon completion of qualification testing. Final vendor testing and qualification documentation is ongoing, but is scheduled for completion by December 23, 2013. By January 10, 2014, TVA will provide the results and notify the NRC final vendor testing and qualification documentation for RAI #6 is available for review.

References:

1. Westinghouse calculation CN-PEUS-1 3-20, Seismic Analysis of the SFP Primary-Mounting Bracket at WBN I & II, Rev. 0
2. Westinghouse calculation CN-PEUS-13-21, Seismic Analysis of the SFP Backup Mounting Bracket at WBN I & II, Rev. 0
3. TVA calculation 47A061026, Wall Mounted Instrument Panel Typical 47A061-26, Rev. 4
4. Westinghouse Report EQ-QR-264, Equipment Qualification Abbreviated Summary Report for the Spent Fuel Pool Instrumentation System, Rev. 0
5. Westinghouse document WNA-PT-00188-GEN, SFPIS Standard Product Test Strategy, Rev. A TVA will make these documents available for review upon request.

E1-5 of 19

RAI #7 Foreach of the mounting attachments requiredto attach SFP Level equipment to plant structures,please describe the design inputs, and the methodology that was used to qualify the structuralintegrity of the affected structures/equipment."

TVA Response The design input and qualification methodology is consistent with TVA's current safety related seismic design. The design input and qualification methodology used for the mounting attachment of the instrument enclosures and transmitter are documented in the referenced TVA ESQ calculation. The design input and qualification methodology used for the mounting attachment of the cable probe mounting brackets are documented in the referenced TVA Civil design standard specification and specification exception.

References:

1. TVA ESQ calculation 47A061026, Wall Mounted Instrument Panel Typical 47A061-26, Rev. 4
2. WVA Civil calculation CSG90CA01, Evaluation of HILTI KWIK-Bolt Wedge Bolt Concrete Anchors, Rev 5.
3. TVA General Specification Exception G-32-WBN-14, G-Spec Exception, Rev. 0
4. TVA General Engineering Specification G-32, Bolt Anchors Set in Hardened Concrete, Rev 23
5. TVA Design Standard DS-C1.7.1, General Anchorage to Concrete, Rev 11 TVA will make these documents available for review upon request.

RAI #8 Please provide analysis of the maximum expected radiologicalconditions (dose rate and total integrateddose) to which the associatedtransmitter(electronicspackage) will be exposed at the design location.

TVA Response The transmitters will be located in the upper containment access room on each unit which is shielded from the fuel in the SFP by concrete around the SFP and the concrete wall of the access room. The combined concrete thickness and angle that the radiation would travel through the concrete are expected to significantly limit the dose to the transmitter. WBN will prepare a calculation to confirm the total integrated dose to the transmitter during a BDB-EE event is acceptable. The calculation is scheduled to be complete by February 28, 2014. By March 1, 2014, TVA will notify the NRC that the calculation for RAI #8 is available for review.

RAI #9 Pleaseprovide information indicating what will be the maximum expected ambient temperature in the room in which the associatedtransmitter(electronicspackage) will be located under BDB conditions in which there is no ac power available to run Heating Ventilation and Air Conditioning (HVAC) systems.

TVA Response The transmitters will be located in the upper containment access room on each unit which is a separate environmental area than the SFP. The upper containment access room is a Harsh E1-6 of 19

Environment for design basis events, but this area will be a mild environment for ELAP. WBN will document the maximum expected ambient temperature in the upper containment access room during a BDB-EE and confirm that it is an acceptable environment for the transmitter. The evaluation is scheduled to be complete by February 28, 2014. By March 1, 2014, TVA will provide the results and notify the NRC that the evaluation for RAI #9 is available for review.

RAI #10 Please provide information confirming underBDB conditions, in which there is no ac power available to run HVAC systems, whether the sensor electronics is capable of continuously performing its requiredfunctions under this expected post humidity condition.

TVA Response The transmitter electronics are qualified for a maximum relative humidity of 0-100% . This bounds all environmental humidity conditions that might exist in the area of the transmitter.

RAI #11 Please provide the following:

a) A description of the specific method or combination of methods you intend to apply to demonstrate the reliabilityof the permanently installed equipment under BDB ambient temperature,humidity, shock, vibration, and radiationconditions.

b) A description of the testing and/oranalyses that will be conducted to provide assurance that the equipment will perform reliably under the worst-case credible design basis loading at the location where the equipment will be mounted. Include a discussion of this seismic reliabilitydemonstration as it applies to a) the level sensor mounted in the SFP area, and b) any control boxes, electronics, or read-out and retransmittingdevices that will be employed to convey the level information from the level sensor to the plant operatorsor emergency responders.

c) A description of the specific method or combination of methods that will be used to confirm the reliabilityof the permanently installedequipment such that following a seismic event the instrument will maintain its requiredaccuracy.

TVA Response a) Harsh Environment: The nonmetallic materials of the SFPIS located in the SFP area will be evaluated to confirm their behavior with respect to radiation aging mechanisms. Any materials for which radiation degradation effects cannot be determined will be tested to demonstrate suitable resistance to radiation. Non-metallic components are rated for use in temperatures higher than 212 degrees F, which corresponds to the saturated steam environment of extended boiling in the spent fuel pool. The ability of the SFPIS to function properly at the expected temperature and steam environmental conditions is demonstrated by test.

Shock and Vibration: Components of both the primary and backup measurement channels will be permanently installed and fixed to rigid, structural walls or floors of seismic category 1 structures, and will not be subject to anticipated shock or vibration inputs. The level sensor electronics are enclosed in a NEMA-4X housing. The electronics panel utilizes a NEMA-4X rated stainless steel housing. These housings will be mounted to a seismically qualified wall and aid in protecting the internal components from vibration induced damage. No additional vibration and shock testing is required. As provided by the NRC order and the NEI guidance as clarified by the interim staff E1-7 of 19

guidance, the probe, coaxial cable, and the mounting brackets are "inherently resistant to shock and vibration loadings".

Mild Environment: For equipment located in the mild environment, an assessment of equipment aging-related effects was performed to determine if aging has a significant effect on the ability of the equipment to perform following a plant design basis earthquake. Significant age-sensitive effects will be identified for incorporation into technical manual recommendations for routine preventive maintenance. No beyond design basis conditions have been defined for mild-environment equipment.

Environmental testing of the electronics cabinet will be in accordance with the following standards:

" IEEE-323-1974, Standard for Qualifying Class 1 E Equipment for Nuclear Power Generating Stations

" NA 11.2, In-house Environmental Testing, Rev. 1 b) The SFPIS's seismic adequacy shall be demonstrated using the methodology defined in IEEE 344-2004 for seismic category 1, which allows for a combination of test and analysis. Seismic frequency and acceleration test parameters will reflect an envelope of 2X design basis safe shutdown earthquake test response spectra with 5% critical damping used to qualify safety related instrumentation for Westinghouse-supplied-NSSS operating plants. This equipment shall maintain functionality and physical integrity before and after five operating basis earthquakes and one safe shutdown earthquake.

The seismic adequacy of the level sensor assembly in the SFP area, transmitter, transmitter bracket, electronics cabinets with indicators, and coaxial cable was demonstrated by vendor testing in accordance with the standards listed below.

The seismic adequacy of the sensor probe supporting bracket within the SFP area was demonstrated by analysis as discussed in the response to RAI-5a.

  • IEEE 344-2004, IEEE Recommended Practice for Seismic Qualification of Class 1 E Electrical Equipment for Nuclear Power Generating Stations
  • IEEE-323-1974, Standard for Qualifying Class 1E Equipment for Nuclear Power Generating Stations
  • NA 11.1, In-house Seismic Testing, Rev. 1 c) The methods described in the response to RAI-1 lb apply to RAI-1 1c. The acceptance criteria for these methods states that no degradation or loss of function below a performance level specified by the manufacturer is allowed, and that the system must provide reliable SFP level indication.

E1-8 of 19

RAI #12 For RAI #11 above, please provide the results for the selected methods, tests and analyses utilized to demonstrate the qualification and reliabilityof the installed equipment in accordance with the Orderrequirements.

TVA Response A summary of the test conditions for which the equipment is to be qualified are summarized below as reported by the vendor. Current results of vendor tests and analysis demonstrating the qualification of the installed equipment have been provided by the vendor. Final vendor testing and qualification documentation is ongoing, but is scheduled for completion by December 23, 2013. By January 10, 2014, TVA will provide the results and notify the NRC that testing and qualification documentation for RAI #12 is available for review.

Environmental Conditions for SFPIS Components in the Spent Fuel Pool Area The coaxial cable, the coupler, the pool-side bracket and the probe in the spent fuel pool area are required to operate reliably in the service environmental conditions specified for the environmental conditions in the table below.

Parameter Normal BDB Temperature 50-140°F 212°F Pressure Atmospheric Atmospheric Humidity 0-95% HR 100% HR (saturated steam)

Radiation TID 1E03 Rads y 1E07 Rads y (above pool)

Radiation TID 1 E07 Rads y (12" above top of fuel rack) (probe and weight only) 1E07 Rads y Environmental Conditions Outside of the Spent Fuel Pool Area The level sensor electronics, sensor electronics bracket, indicators and the electronics enclosures outside of the spent fuel pool area are required to operate reliably in the service environmental conditions specified for the environmental conditions in the table below.

Parameter Normal BDB BDB (Level Sensor Electronics Only)

Temperature 50-120°F 140°F 170°F Pressure Atmospheric Atmospheric Atmospheric Humidity 0-95% HR 0-95% HR 0-100% HR (non-condensing) (non-condensing)

Duration 4 days 4 days 4 days Radiation < 1E03 R y < 1E03 R y < 1E03 R y TID E1-9 of 19

Thermal Aging The SFPIS thermal aging process performed on the interconnecting cable and cable coupler inside the spent fuel pool area, followed by successful radiation aging and seismic testing of the components, has demonstrated a 2.5 year life for the level sensor after a beyond-design-basis event; however, further vendor investigation of the test results is pending and confirmation of acceptable test data will be documented by the vendor upon completion. Any age-sensitive effects will be incorporated into the technical manual recommendations for routine preventive maintenance.

Seismic Cat-1 Testing/Analysis The SFPIS Cat-1 seismic testing performed by the vendor and manufacturer, together with the technical evaluations performed by the vendor, confirm that the SFPIS is seismically acceptable for plant use and meets the seismic requirements of the vendor's design specification, which states that the SFPIS's seismic adequacy shall be demonstrated using the methodology defined in IEEE 344-2004 for seismic category I, and that the equipment shall maintain functionality and physical integrity before and after five Operating Basis Earthquakes (OBEs) and one Safe Shutdown Earthquake (SSE).

Vendor seismic testing profile exceeds 2x SSE for WBN.

Vibration Justification Refer to RAI-1 1a response.

Sloshing Justification (with exception of Boron/Boric Acid)

During the SFPIS product development, a sloshing calculation was performed by the vendor to demonstrate that the probe would not be "sloshed" out of the spent fuel pool during a seismic event. This calculation concluded that, regardless of the construction, the probe will not be thrown out of the pool during a seismic event.

RAI #13 Pleaseprovide the NRC staff with the final configurationof the power supply source for each channel, as well as cable and conduit separation,so that the staff may conclude that the two channels are independent from a power supply assignment perspective.

TVA Response Power to the primary channel is supplied from 120 volt AC vital instrument power board 2-111, which is train A. Power to the backup channel is supplied from 120 volt AC vital instrument power board 2-IV, which is train b. The vital boards are supplied by the vital batteries and vital inverters, and will be backed up by the FLEX diesel generators. WBN FLEX diesel generator strategy provides two 225kva diesel generators on the roof of the Auxiliary Building to provide a direct connection to vital battery chargers and two 3MW diesel generators that provide an alternate approach to energize the battery chargers utilizing safety related shutdown power distribution. This approach is described in detail in response to order EA-12-049.

Cable and conduit for each channel maintain trained separation from the power source to their respective instrument enclosures, which are mounted in separated areas of the plant.

El-10 of 19

RAI #14 Please provide the results of the calculation depicting the battery backup duty cycle requirements demonstratingthat its capacity is sufficient to maintain the level indication function until offsite resource availabilityis reasonably assured.

TVA Response The calculation concludes that the backup battery life is 96.24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> at full charge after loss of onsite ac power based on maximum power consumption throughout the duration of the battery life.

RAI #15 Pleaseprovide the following:

a) An estimate of the expected instrument channel accuracy performance (e.g., in percentage of span) under both a) normal spent fuel pool level conditions (approximately Level 1 or higher)and b) at the BDB conditions (i.e., radiation,temperature, humidity, post-seismic and post-shock conditions) that would be present if the SFP level were at the Level 2 and Level 3 datum points.

b) A descriptionof the methodology that will be used for determining the maximum allowed deviation from the instrument channel design accuracy that will be employed under normal operating conditions as an acceptance criterion for a calibrationprocedure to flag to operatorsand to technicians that the channel requires adjustmentto within the normal condition design accuracy.

(This information was previously requested as RAI-6 in NRC letter dated August 2, 2013)

TVA Response a) Each instrument channel is expected to be accurate to within an estimated +/-1% of calibrated span during normal spent fuel pool level conditions. The instrument channels are expected to retain this estimated accuracy after being subjected to BDB conditions.

This estimate is based on the vendor's specification documentation. Instrument qualification and test results for this system have not yet been provided by the vendor.

Receipt of Instrument accuracy calculations performed by the vendor is scheduled for December 13, 2013. By January 10, 2014, TVA will notify the NRC that testing and qualification documentation for RAI #15 is available for review.

b) Technicians will be required to perform an instrument channel calibration in the event that the instrument channel output lies outside the acceptance band established in the setpoint and scaling documents. The acceptance band or "as-left tolerance" is defined as the acceptable parameter variation limit above or below the desired output for a given input standard associated with the calibration of the instrument channel.

The instrument channel acceptance band, which may or may not be symmetrical, is calculated using the square root of the sum of the squares (SRSS) combination of the as-left tolerance for each component comprising the instrument loop. The as-left tolerance of each component is equal to or greater than the reference accuracy of the device being calibrated, but is not so large that it could prevent or mask detection of instrument degradation or failure. Note that the SRSS method is only used for uncertainty terms that are random, independent, and posses a normal (bell-shaped) distribution; otherwise, the uncertainty term is combined through summation, either El-11 of 19

within the SRSS (for dependent terms) or outside of the SRSS (for bias and non-normally distributed terms).

RAI #16 Please provide analysis verifying the instrumentationaccuracy and that the proposed instrument performance is consistent with the estimated accuracy normal and BDB values. Please demonstrate that the channels will retain these accuracyperformance values following a loss of power and subsequent restorationof power.

TVA Response The Guided Wave transmitter is a microprocessor based transmitter with its operating system in firmware and adjustable parameters stored in non-volatile memory. If power is lost and later restored, the transmitter remains calibrated to its original parameters and will restore indication to actual pool level within the stated loop accuracies. The vendor is developing a channel accuracy calculation. The calculation is scheduled to be complete by December 13, 2013. By January 10, 2014, TVA will notify the NRC that the calculation for RAI #16 is available for review.

RAI #17 Provide the SFP level instrumentationaccuracy analysis results that confirm that level instrument accuracyis sufficient to read Level 3 with sufficient conservatism that ensures the fuel remains covered.

TVA Response The vendor is developing a channel accuracy calculation. The calculation is scheduled to be complete by December 13, 2013. By January 10, 2014, TVA will provide the channel accuracy calculation results and notify the NRC that the calculation for RAI #17 is available for review.

RAI #18 Please provide the following:

a) A description of the capabilityand provisions the proposed level sensing equipment will have to enable periodic testing and calibration,including how this capabilityenables the equipment to be tested in-situ.

b) A description of how such testing and calibration will enable the conduct of regularchannel checks of each independent channel against the other, and against any otherpermanently installed spent fuel pool level instrumentation.

c) A description of how calibrationtests and functional checks will be performed and the frequency at which they will be conducted. Discuss how these surveillances will be incorporatedinto the plant surveillance program.

d) A description of what preventive maintenance tasks are required to be performed during normal operation,and the planned maximum surveillance interval that is necessary to ensure that the channels are fully conditioned to accuratelyand reliably perform theirfunctions when needed.

(This information was previously requested as RAI-7 in NRC letter dated August 2, 2013)

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TVA Response a) The support bracket for the level sensor cable has been designed and manufactured with a sliding section. This sliding section provides a fixed distance that the sensor cable can be raised for calibration verification (12 inches). The manufacturer has documented that the calibration is based on a linear time delay from transmission of the radar pulse to return of reflection on the surface of the water. Manufacturer documentation provides certification that raising the sensor a fixed distance and verifying that the indicator changes by this fixed amount confirms that the transmitter is in calibration. The system is designed to enable the removal of the sensor cable from the transmitter and attach a previously certified sensor cable with an adjustable metal target to allow a detailed multipoint calibration by mounting the target at different points along the cable for troubleshooting, if necessary. Each component in the instrument channel can be replaced (transmitter included) to restore the instrument loop to service in the event a component failure occurs.

In-situ testing will be performed by loosening the hold down bolts and raising the sensor assembly until it hits the top stop (12 inches) and verifying that the indicator responds with a corresponding 12 inch change (allowed inaccuracy of change will be documented in the scaling analysis). Upon completion of measurement, the technician will lower the mounting bracket and re-torque the slide assembly hold down bolts.

b) Channel Check is not a specified requirement in NEI 12-02. Channel Check is specified in IEEE 338-1987 for Safety Systems. SFP level instrument channels are not safety related and are not subject to testing requirements of safety related instrumentation. If the plant staff determined a need to confirm that the two channels are performing as expected, the two channels may be read in the shutdown board room. While the SFP is operating within design basis and at normal level, the indicators may be compared to fixed marks within the SFP by visual observation to confirm indicated level.

c) A description of channel calibration or functional test is shown in the response for RAI-7a. TVA will perform periodic calibration verification using a periodic maintenance procedure. The periodic calibration verification will be performed within 60 days of a refueling outage considering normal testing scheduling allowances (e.g., 25%).

Calibration verification will not be required to be performed more than once per 12 months. These calibration requirements are consistent with the guidance provided in NEI 12-02 section 4.3.

d) Preventive Maintenance procedures will be in place for periodic replacement of the backup batteries based on manufacturer recommendations and for calibration verification as identified in RAI 18c.

RAI #19 a) Pleaseprovide the specific location for the backup instrument channel display.

b) Please describe the evaluation used to validate that the display location can be accessed without unreasonabledelay following a BDB event. Include the time available for personnel to access the display as well as the actualtime (e.g., based on walk-throughs) it will take for personnel to access the display. Additionally, please include a description of the radiologicaland environmental conditions on the paths personnel might take. Describe whether the display location remains habitable for radiological,heat and humidity, and other environmentalconditions following a BDB event. Describe whether personnel are continuously stationed at the display or monitor the display periodically.

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TVA Response a) WBN had proposed locating an indicator for the backup channel in the main control room. The backup channel has an indicator in the Electric Board Room (EBR) which is in close proximity to the Auxiliary Control Room. See Sketch 3 on page E1-15. WBN has eliminated the main control room indicator because full compliance is achieved by having two independent channels of indication, physically separated and both located in the EBR area.

The EBR and path to the EBR from the MCR is a mild environment during ELAP, is promptly accessible (2 minute walk) by main control room personnel and is not subject to the environmental conditions associated with boiling in the SFP. Communication by radio or telephone is available if needed. The route to the Electric Board Room/Auxiliary Control Room area from the Main Control Room will be the same route that is utilized during design basis events because the route is within a safety related, seismic structures (Control Building and Auxiliary Building). The pathway is expected to remain intact following a seismic event. See Sketch 3 on page E1-15 that is an update to the sketch previously provided in Reference 4 for access pathway.

b) The following response is an update to what was submitted to RAI 8a and 8b in Reference 4 of the cover letter:

8a) WBN SFP is shared between both units and will have a total of two level instrument channels. Both instrument channel displays will be located in the Electric Board Room (EBR) which is in close proximity to the Auxiliary Control Room. See Sketch 3 page E1-15. The displays will be physically separated utilizing Class 1 E train separation criteria to maintain channel independence. The EBR and path from MCR to EBR is a mild environment during ELAP, is promptly accessible (2 minute walk) by main control room personnel and is not subject to the environmental conditions associated with boiling in the SFP. Communication by radio or telephone is available if needed. The route to the EBR from the MCR will be the same route that is utilized during design basis events because the route is within a safety related, seismic structure. The pathway is expected to remain intact following a seismic event. See Sketch 3 on page E1-15 for the route from the MCR to the EBR.

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I l I ii r(~r'EL765~I -

Sketch 3 Route from Main Control Room to Electric Board Room 8b) The Electric Board Room is in a mild environment is promptly accessible (2 minute walk) by main control room personnel. The environment is not affected by the environmental conditions associated with any SFP drain down scenario.

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RAI #20 Pleaseprovide a list of the procedures addressingoperation (both normal and abnormal response), calibration,test, maintenance, and inspection procedures that will be developed for use of the spent SFP instrumentation. The licensee is requested to include a brief description of the specific technical objectives to be achieved within each procedure.

(This information was previously requested as RAI-7 in NRC letter dated August 2, 2013)

TVA Response The following list of procedures is provided:

  • O-SOI-78.01, "Spent Fuel Pool Level Indication System,"

This system operating instruction describes the SFPLIS and its operation.

  • 0-FSI-1 1, "Alternate SFP Makeup,"

This Flex Support Instruction provides actions to make up to the Spent Fuel Pit from alternate sources.

0O-FSI-13, "Transition from FLEX Equipment,"

This Flex Support Instruction provides actions to transition to normal plant equipment when available.

  • Calibration and test procedures are still to be developed.

RAI #21 Please provide the following:

a) Furtherinformation describing the maintenance and testing program the licensee will establish and implement to ensure that regulartesting and calibrationis performed and verified by inspection and audit to demonstrate conformance with design and system readiness requirements.Include a description of your plans for ensuring that necessary channel checks, functional tests, periodic calibration,and maintenance will be conducted for the level measurement system and its supporting equipment.

b) A description of how the guidance in NEI12-02 Section 4.3 regardingcompensatory actions for one or both non-functioning channels will be addressed.

c) A description of the compensatory actions to be taken in the event that one of the instrument channels cannot be restoredto functional status within 90 days.

TVA Response a) The maintenance, testing and calibration program will be proceduralized and will contain the elements listed below. The procedure(s) controlling maintenance, testing, and calibration of the SPLIS will be available for inspection.

  • Westinghouse will provide instruction manuals and calibration procedures that will be used to develop calibration procedures for the equipment.

" Nuclear Engineering Setpoint and Scaling Documents NE-SSD-0-L-78-42 and 43, included in DCN 59683-A will be used in the development of the required calibration procedures.

  • Instrument loop calibration verification will be performed by a 2 point test using the adjustable mounting bracket to confirm the transmitter zero point has not drifted and the indicator correctly repeats the elevation change from the adjustable mounting bracket. Required loop accuracy from NE-SSD O-L-78-42 and -43 will be used in the E1-16 of 19

calibration verification. The NE-SSDs will be revised to include the BDB-EE instrument loop accuracies.

  • Westinghouse and K-Tek are also developing an in-situ detailed calibration method which will disconnect the probe cable assemblies and test the transmitter with using a test cable probe assembly if calibration errors are identified during operation or testing.

" The procurement specification contains adequate testing requirements in accordance with EA-12-051 and NEI-12-02, and requires that Westinghouse provide analysis certifying that a 2-point channel check is sufficient to maintain calibration of the full instrument range.

  • Calibration to validate the functionality of the installed instrument channels is required within 60 days of a planned refueling outage, considering normal testing scheduling allowances (e.g. +/- 25%), provided that the calibration has not been performed within the last 12 months.

" Existing work control processes such as Surveillance Instructions (SI), Preventative Maintenance procedures and Work Orders will be utilized to perform testing and maintenance on the instrument channels.

  • Allowable channel out of service times and associated actions will be consistent with the guidance provided in NEI 12-02.

b) NEI 12-02, Section 4.3 states "The primary or back-up instrument channel can be out of service for testing, maintenance and/or calibrationfor up to 90 days provided the other channel is functional. Additionally, compensatory actions must be taken if the instrumentationchannel is not expected to be restored or is not restored within 90 days.

If both channels become nonfunctioning then initiate actions within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to restore one of the channels of instrumentation and implement compensatory actions (e.g., use of alternatesuitable equipment or supplemental personnel) within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />."

WBN will implement a critical spare parts program for the system, taking into account the lead time and availability of spare part to provide assurance that a channel can be restored to service within 90 days. If one or both channels cannot be restored to service within 90 days, or if both channels become non-functioning, as a compensatory measure WBN will utilize 0-AOI-45, "Loss of Spent Fuel Pool Level or Cooling" during any loss of spent fuel pool level or cooling event. This instruction requires the dispatch of operators to determine the spent fuel pool level and cooling system status and investigate for the cause of leakage and to take appropriate actions to restore the spent fuel pool level and cooling.

c) See response to 21b) above.

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Sketch 1 POOL LEVELS AND REFERENCES ELEVATION REFERENCE Mounting Bracket OPERATING FLOOR LEVEL

[757.0' 47W200-3 II 749.21' water level Ref 47W855-1 R32 1High 100% Level

- - - 749.125' Normal Water Level Ref 47W855-1 Calculation EPM-JP-070192 WBN-78-D053 MEB-WBN-78 pg 23a 745.125' SFP suction strainer 47W454-3

- - - 734.29' NEI 12-02 section 2.3.2 (Top of Rack + 10 Feet) 724.79' Un-measurable zone.

Top of un-measurable zone is 0% Level

....- 724.29' Top of Active Drawing DCA 38623-01-6 Fuel 722.78' L36 130208 801

-. -.. 709.23' 47W855-1 El-18 of 19

Sketch 2 SPENT FUEL POOL LEVEL MONITORING SYSTEM PLAN VIEW C aT

.... 1

-~ S SCA8IETAMDOISMAY

.... ... iMBOR BACKUP CONTROL ROOVM)

NOTE DMWUC 13ITM WPENT RFUL POL WM0E DWENS1M.

.... PjjpO~m CAJLE RAYuTME 0 PRPOS5OM EQUIPMENT LOCATM5W E1-19 of 19

ENCLOSURE2 TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT, UNITS I AND 2 LIST OF COMMITMENTS

1. By January 10, 2014, TVA will:
a. notify the NRC that final vendor testing and qualification documentation for RAI
  1. 5 is available for review;
b. provide the results and notify the NRC that final vendor testing and qualification documentation for RAI #6 is available for review;
c. provide the results and notify the NRC that testing and qualification documentation for RAI #12 is available for review;
d. notify the NRC that testing and qualification documentation for RAI #15 is available for review;
e. notify the NRC that the calculation for RAI #16 is available for review; and,
f. provide the channel accuracy calculation results and notify the NRC that the calculation for RAI #17 is available for review.
2. By March 1, 2014, TVA will:
a. notify the NRC that the calculation for RAI #8 is available for review; and,
b. provide the results and notify the NRC that the evaluation for RAI #9 is available for review.

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