ML102460015

Tornado Mitigation License Amendment Request - Response to Request for Additional Information

ML102460015
Person / Time
Site:	Oconee
Issue date:	08/31/2010
From:	Baxter D Duke Energy Carolinas, Duke Energy Corp
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML102460015 (28)

Text

Duke oDAVE BAXTER Duke Vice President

• Energy, Oconee Nuclear Station Duke Energy ON01 VP / 7800 Rochester Highway Seneca, SC 29672 864-873-4460 864-873-4208 fax August 31, 2010 dave. baxter@duke-energy. corn Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Subject:

Duke Energy Carolinas, LLC Oconee Nuclear Station, Units 1, 2, and 3 Docket Numbers 50-269, 50-270, and 50-287, Renewed Operating Licenses DPR-38, DPR-47, and DPR-55 Tornado Mitigation License Amendment Request - Response to Request for Additional Information

References:

1. Letter from Dave Baxter, Site Vice President, Oconee Nuclear Station, Duke Energy Carolinas, LLC, to the U. S. Nuclear Regulatory Commission, "License Amendment Request to Revise Portions of the Updated Final Safety Analysis Report Related to the Tornado Licensing Basis," dated June 26, 2008.

2. Letter from John Stang, Senior Project Manager, Office of Nuclear Reactor Regulation, Nuclear Regulatory Commission to Dave Baxter (Duke), "Request for Additional Information (RAI) Regarding the Licensee Amendment Request for Upgrading the Licensing Basis for Tornado Mitigation," dated May 25, 2010.

3. Letter from Dave Baxter, Site Vice President, Oconee Nuclear Station, Duke Energy Carolinas, LLC, to the U. S. Nuclear Regulatory Commission, "Tornado Mitigation License Amendment Request - Response to Request for Additional Information," dated June 10, 2010.

4. Letter from Dave Baxter, Site Vice President, Oconee Nuclear Station, Duke Energy Carolinas, LLC, to the U. S. Nuclear Regulatory Commission, "Tornado Mitigation License Amendment Request - Response to Request for Additional Information," dated June 24, 2010.

On June 26, 2008, Duke Energy Carolinas, LLC (Duke Energy) submitted a License Amendment Request (LAR) to revise certain sections of the Oconee Updated Final Safety Analysis Report (UFSAR) associated with the tornado licensing basis [Ref.: 1]. This LAR proposes a number of plant modifications to enhance the station's capability to withstand the effects of a damaging tornado, revises the UFSAR sections associated with the tornado licensing basis (LB), and incorporates a NRC-approved tornado missile probabilistic methodology called TORMIS.

On May 25, 2010, Duke Energy received its second Request for Additional Information (RAI) [Ref.: 2]. By letter dated June 10, 2010 [Ref.: 3], Duke Energy notified the NRC that additional time would be needed to respond to several of the items. This submittal contains Duke Energy's responses to these deferred RAI questions. The other RAI questions were submitted to the NRC on June 24, 2010 [Ref.: 4].

www.duke-energy.comr

Nuclear Regulatory Commission Tornado Mitigation Licensing Amendment Request - Response to Request for Additional Information August 31, 2010 Page 2 The engineering design for the modifications associated with the responses to RAI questions 2-27, 2-28, 2-29, 2-30, 2-32, 2-33, 2-34 and 2-36, have not been fully completed and the information contained in the Enclosure and provided on the SharePoint, represents the latest information available as of the date of this letter.

If you have any questions in regard to this letter, please contact Stephen C. Newman, Regulatory Compliance Lead Engineer, Oconee Nuclear Station, at (864) 873-4388.

I declare under penalty of perjury that theforegoing is true and correct. Executed on August 31, 2010.

Sincerely, Dave Baxter, Site Vice President, Oconee Nuclear Station

Enclosure:

Duke Energy RAI Responses

Nuclear Regulatory Commission Tornado Mitigation Licensing Amendment Request - Response to Request for Additional Information August 31, 2010 Page 3 cc: (w/enclosure)

Mr. J. F. Stang, Project Manager Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 8 G9A Washington, D. C. 20555 Mr. L. A. Reyes, Regional Administrator U. S. Nuclear Regulatory Commission - Region II Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, GA 30303-1257 Mr. Andy Sabisch NRC Senior Resident Inspector Oconee Nuclear Station Susan E. Jenkins, Manager Radioactive & Infectious Waste Management SC Dept. of Health and Environmental Control 2600 Bull St.

Columbia, SC 29201

Enclosure Duke Energy RAI Responses

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 2 RAI 2-27 Provide the following information for the new PSW transformer, switchgear, load center and the circuit breakers: 1) equipment design ratings, 2) a summary of the analyses performed to show the loading, short circuit values and the interrupting ratings, voltage drop, and protection and coordination, 3) the existing station ASW switchgear ratings, and 4) the periodic inspection and testing requirements for electrical equipment. Provide applicable schematic and single line diagrams.

Duke Energy Response

1. The PSW 13.8 kV/4.16 kV switchgear is a double ended unit substation. Each unit substation, denoted as B6T and B7T, consists of normal and alternate 13.8 kV power source breakers, a step-down transformer, a 4.16 kV main breaker connected to its respective 4.16 kV switchgear buss and 4.16 kV feeder breakers. The 4.16 kV switchgear busses B6T and B7T may be connected through a 4.16 kV tie breaker. The design ratings for the PSW switchgear are as follows:

Each switchgear step-down transformer is rated at 10 MVA 60 Hz 3-phase and is a solid cast dry type AA/FA rated at, 133% with cooling fans activated-by a temperature controller. The primary winding is 13.8 kV delta and a BIL rating of 110 kV. The secondary winding is 4.16 kV Wye and a BIL rating of 75 kV. The transformer windings are copper with an impedance of 5.5% +/- 7.5% tolerance with taps at 2-2.5% FCAN and 2-2.5% FCBN and an insulation class of 185'C.

The 13.8 kV switchgear is rated at 15 kV maximum voltage 1200 A with a BIL rating of 95 kV and short-circuit rating of 48 kA rms. The 13.8 kV breakers are rated at. 1000 MVA 1200 A with a 50 kA rms interrupting rating and a minimum close and latch rating of 130 kA rms.

The 4.16 kV switchgear is rated at 4.16 kV maximum voltage-2000 A with BIL rating of 60 kV and a short circuit rating of 49 kA rms. The 4.16 kV main circuit and tie breakers are rated at 4.76 maximum voltage 350 MVA 2000 A. The 4.16 kV feeder breakers are rated at 4.76 kV maximum voltage 350 MVA 1200 A. All 4.16 kV breakers have a maximum interrupting rating of 50 kA rms and a minimum close and latch rating of 130 kA rms.

The 600 VAC load center located in the PSW building consists of a step-down transformer and 600 V main and feeder breakers.

The load center transformer is rated at 5 MVA 60 Hz 3-phase. The primary winding is 4.16 kV delta and a BIL rating of. 75 kV. The secondary winding is 600 V and a BIL rating of 30 kV.

The transformer windings are copper with an impedance of 5.95 % +/- 7.5% tolerance with taps at 2-2.5% FCAN and 2-2.5% FCBN and an insulation class of/220°C.

The load center main breaker is rated at 5000 A with an interrupting rating of 85 kA. The feeder breaker ratings are 1600 A or 800 A. Both feeder breakers sizes have interrupting ratings of 65 kA.

2. The two main analyses for the PSW transformer, switchgear, load center and circuit breakers are contained in calculations OSC-9832 (Unit 1/2/3 PSW AC Power System - ETAP Model Base File), and OSC-9370 (UL 1/2/3 PSW AC Power System Voltage and Short Circuit Analyses).

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 3 OSC-9832 determines and documents equipment and system parameters required to model the PSW AC power system and associated loads. Input parameters are obtained from vendor documents, drawings, calculations and other sources as required. These results are then used as design input for OSC-9370. In addition to equipment electrical parameters, the alignment of the PSW AC system for different scenarios is documented by this calculation.

Calculation OSC-9370 performs a bounding analysis for the PSW AC power system by comparing the analysis results with the equipment ratings to ensure acceptable performance under the postulated scenarios. The electrical analyses performed by this calculation includes low voltage, high voltage and short circuit, which are summarized as follows:

The low voltage analysis is contained in Appendix C of OSC-9370. The worst case starting voltage is when the PSW or SSF (Standby Shutdown Facility) systems are heavily loaded with the PSW power source aligned to either Keowee or the Fant line. Both motor starting and steady-state analyses are performed.

The high voltage analysis in contained in Appendix D of OSC-9370 and evaluates the case where the PSW system is lightly loaded and aligned to a power source operating at the high-end of its voltage range.

The short circuit analysis is contained in Appendix F of OSC-9370. This analysis compares the calculated fault duty at the PSW equipment with the equipment ratings when aligned to the PSW power source with the highest fault duty.

For detailed information, refer to calculations OSC-9832 and OSC-9370 on the SharePoint.

Equipment protection and coordination studies are still under development and are not available for review. The anticipated completion date for the protection and coordination studies is December 2010.

3. The existing ASW switchgear consists of four (4) 4.16 kV breakers rated at 1200 A each, a 4.16 kV/600 V/347 V 500 kVA transformer and four (4) 600 V 600 A breakers. The ASW switchgear will be removed and the ASW functions will be replaced by the PSW system.

4. Periodic inspection and testing requirements have not been finalized and cannot be provided at this time. Inspection and testing requirements for the electrical equipment will be per applicable Technical Specifications and vendor, industry and Duke standards.

For calculations and drawings, refer to the following files on the SharePoint:

RAI 2-27 PSW Switchgear One Line Diagram.pdf RAI 2-27 PSW Loadcenter One Line Diagram.pdf RAI 2-27 ASW Switchgear One Line Diagram.pdf RAI 2-27 13.8 kV Switchgear Elementary Diagrams.pdf RAI 2-27 4.16 kV Switchgear B6T Elementary Diagrams.pdf RAI 2-27 4.16 kV Switchgear B7T Elementary Diagrams.pdf RAI 2-27 600 V Loadcenter Elementary Diagrams.pdf RAI 2-27 OSC-9370 Rev. 0 PSW AC Power System Analyses.pdf RAI 2-27 OSC-9832 Rev. 0 PSW AC Power System ETAP Model Base File.pdf

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 4 RAI 2-28 Provide the following information concerning the proposed PSW instrumentation and control (I&C) power and the interface with the existing plant vital I&C power: 1) design of the direct current (DC) system for the PSW system including how the DC control power for the new PSW load center, switchgear and the transformer will be provided, 2) the impact on existing DC vital system including loading on the existing battery and the battery charger, 3) describe the analysis performed to determine the capacity of the batteries and the battery charger, voltage requirements at the equipment terminals, electrical protection and co-ordination, and 4) the periodic inspection and testing requirements. Provide applicable schematic and single line diagrams.

Duke Energy Response

1. The PSW DC system includes two batteries, two battery chargers, one 125 VDC power distribution center, two 125 VDC power panelboards located in the PSW building and three

-125 VDC power panelboards located in Auxiliary Building, a DC ground detector system and battery test connection boxes.

Each battery consists of 60 C&D LCY-39 flooded lead-acid cells. One battery and one battery charger is aligned to the PSW DC system at a time and the other battery is isolated from the main PSW DC system and maintained on float voltage by the other battery charger.

The two 300 ADC battery chargers are manufactured by AMETEK. The PSW DC system design will allow either charger to be aligned to either battery.

The PSW DC system will provide DC control power to the PSW switchgear and load centers via the 125 VDC PSW power distribution center and power panelboards and also provides DC

.control power for additional PSW equipment located in the PSW building and Auxiliary building. At present, no transformer DC power is required.

2. Additional loading imposed by new PSW components on the existing plant Vital I&C DC system is within the design margin and consists of new main control room indication and power supplies. The remainder of the new DC PSW loads will be fed from the PSW DC system and there will be no direct electrical interconnection between the PSW DC and existing Vital I&C DC systems.

3. The analysis used for selecting the PSW battery size was performed by analysis using IEEE 485-1997 (R2003) methodology. The battery sizing analysis included as a design requirement the ability to jumper out up to two cells from the nominal 60 cell battery while still maintaining sufficient capacity to feed the design basis load. The IEEE 485 sizing resulted in a required cell size of LCY-37, which was increased to LCY-39 to provide additional design margin for the PSW DC system.

The battery charger size was selected using IEEE 946-2004 methodology and is based on a battery recharge time of eight (8) hours.

Battery terminal voltage is based on a minimum value of 105 VDC.

PSW DC system protection and coordination studies are under development are not ready for review.

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 5

4. The PSW DC system will be periodically inspected, maintained and tested per vendor and industry recommendations to maintain equipment reliability and qualification and satisfy Technical Specification surveillance requirements.

The PSW batteries will undergo weekly, monthly, quarterly and annual battery surveillances and inspection including voltage, specific gravity, electrolyte level and temperature, battery condition and service and performance discharge tests. Battery racks will also be subject to periodic inspection and maintenance.

The PSW Battery chargers will undergo periodic inspections and testing such as float and equalization voltage adjustment, circuit board calibration, cleaning and periodicparts replacement and load testing.

The PSW 125 VDC distribution center, panels and ground detection system will undergo periodic testing, calibration and cleaning.

For drawings, refer to the following files on the SharePoint:

RAI 2-28 PSW DC Distribution Center for PSW Building RAI 2-28 PSW DC Power Panelboards for PSW Building RAI 2-28 PSW DC Power Panelboards for Aux Building RAI 2-29 In Enclosure 2, Section 3.3.4 of the June 26, 2008, LAR the licensee states that the Keowee Hydroelectric Units (KHUs) will provide power supply to the PSW switchgear through underground cables. Provide analyses to show the kilo volt ampere (kVA) loading, new circuit breaker rating, short circuit values, and voltage drop. In addition, provide information on the electrical protection and coordination, and the periodic inspection and testing requirements. Further, explain how the redundancy and independence of the Class 1 E power system is maintained as a result of the proposed modification. Provide applicable schematic and single line diagrams.

Duke Energy Response The PSW system as presently designed imposes a KVA loading on the Keowee Hydroelectric Units of approximately 286 A or 6,836 kVA (see OSC-7729 Table B1).

The new Keowee circuit breaker ratings are 15 kV 3-phase 60 Hz 1200 amps rms with a peak withstand voltage of 95 kV, a fault duty of 63 kA rms symmetrical, and a peak close and latch rating of 173 kA. The symmetrical rms short circuit value seen at the new Keowee circuit breakers is 54.3 kA (see OSC-9370 Appendix F).

Voltage drop consists of the following three scenarios taken from OSC-9370 Appendix C:

1. Keowee as source voltage with PSW fully loaded and SSF house loads. For this case, the minimum Keowee generator terminal voltage is 101.55% on a 13.8 kV base.

2. Keowee as source voltage with PSW house loads and SSF fully loaded. For this case, the minimum Keowee generator terminal voltage is 100.91% on a 13.8 kV base.

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 6

3. Keowee as source voltage feeding a fully loaded PSW system and no SSF loads. For this case, the minimum Keowee generator terminal voltage is 98.64% on a 13.8 kV base.

Equipment protection and coordination studies are under development and are not ready for review. The anticipated completion date is December 2010.

Periodic inspection and testing requirements have not been finalized and cannot be provided at this time. Periodic inspection and testing requirements for the electrical equipment will be per applicable Technical Specifications and vendor, industry and Duke standards.

The redundancy of Keowee remains unchanged as a result of this modification. Independence of the Class 1E power system is maintained as previously described in Duke's June 24, 2010 response to RAI question 2-31.

Schematic and single line diagrams are under development and cannot be provided at this time.

The anticipated date when these documents can be provided is April 2011.

For analyses, refer to the following files on the-SharePoint:

RAI 2-29 OSC-9370 Rev. 0 PSW AC Power System Analyses.pdf RAI 2-29 OSC-7729 Rev. 3 KHU Underground Cable Replacement Calc.pdf RAI 2-30 The licensee states in the June 26, 2008, LAR that the PSW system will be fully operational from the respective unit's main control room and will be activated when existing redundant emergency systems are not available. Describe how the alarms, indications, and the electrical controls will be provided from the main control rooms of Units 1 and 2 to the proposed PSW switchgear. Explain how the controls are provided for Unit 3. Provide applicable electrical schematics and evaluations highlighting the design features.

Duke Energy Response Below is a summary of alarms, indications and controls in the Units 1, 2 and 3 main control rooms for the PSW switchgear. Also included are main control room alarms, indications and controls for other PSW-related equipment not associated with the PSW switchgear.

Unit 1:

1. Adds to alarm panel 1SA12 a loss of voltage alarm to window 1SA12-1 for MCC 1XPSW.

2. Adds to alarm panel 1 SA1 2 a loss of voltage alarm to window 1 SAl 2-11 for powerpanel 1 KPSW

3. Changes window 1 SA5-1 1 from EL DC System 1 CA Trouble to EL DC System 1 CA/PSW Trouble.

4. Adds seven (7) additional ionization smoke detectors at elevation 822' located above the suspended ceiling in the Main Control Room for Unit 1 within the' vicinity of the PSW cables.

5. A new PSW blocking valve control switch with position indication lamps in the Unit 1 Control Room to isolate the PSW flow to both Unit 1 Steam Generators (S/G 1A & 1 B).

6. Two (2) new PSW flow controllers with flow indication and position indication lamps, one for each of the Unit 1 Steam Generators in the Unit 1 Control Room to control the high flow to the individual Steam Generator PSW Main Flow control valves.

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 7

7. Two (2) new PSW signal isolators to provide PSW S/G 1A and 1B flow indication to the OAC.

8. Two (2) new throttle switches with position indication lamps, one for each of the Unit 1 Steam Generators in the Unit 1 Control Room to throttle the individual Steam Generator PSW control bypass valves.

9. Two (2) new Unit 1 HPI System power transfer switches with lamps in the Unit 1 Control Room to select power for the 1A and 1 B HPI Pumps. Two new white lamps to show which pump the field alignment switch is aligned to (HPI Pump 1A or 1 B). There will also be two (2) more new switches mounted directly on each HPI transfer switch panel in the Auxiliary Building. One will switch will select Local or Remote control. The other switch will select Normal or PSW power.

10.

One (1) new pump start switch with lamps to start HPI Pump 1A or lB.

11.

A new Unit 1 HPI power transfer switch with lamps in the Unit 1 Control Room to select power to valve 1 HP-24.

12.

A new Unit 1 HPI power transfer switch with lamps in the Unit 1 Control Room to select power to valve 1 HP-26.

13.

A new Unit 1 HPI switch with position indication lamps in the Unit 1 Control Room to control the new IHP-139, RCP Seal Supply blocking valve.

14.

A new Unit 1 HPI switch with position indication lamps in the Unit 1 Control Room to control the new 1HP-140, RCP Backup Seal Supply throttle valve.

15. Three (3) new Unit 1 RC power transfer switches with lamps in the Unit 1 Control Room to select power for the Unit 1 RV Head Vent Valves (RC-SV-1 59 & 160) and SG High Point Vent Valves (RC-SV-155, 156, 157 & 158).

16.

A new PSW 4KV power available lamp in the Unit 1 Control Room to indicate power is available from PSW.

17.

Replace the Reactor Coolant Pump Seal Injection flow indicator (1HPI P-0025) with a QA-1 indicator. A new QA-1 signal isolator, a new QA-1 signal conditioner and a new QA-1 power supply will also be added in the Control Room for this instrument loop. This modification will also replace the Reactor Coolant Pump Seal Injection flow transmitter (1 HPI FT-0075) in the field with a QA-1 transmitter and its associated cabling to maintain a complete QA-1 instrument loop.

18.

Removes and relocates the four (4) HP FDWPT Stop Valve indicator lamps to the vertical portion of the 1 UB1 board.

19.

Removes and relocates the four (4) LP FDWPT Stop Valve indicator lamps to the vertical portion of the 1 UB1 board.

20. Removes and relocates the SG SU Range Level indicator next to the SG Full Range Level indicator on the vertical portion of the 1 UB1 board.

21.

Removes the two FDWPT RPM indicators, replace them with a non QA-1 dual Dixson indicator and relocate the indicator on the vertical portion of the 1 UB1 board next to the SG Level Full Range and SG SU Level Indicators.

Unit 2:

Stat Alarms:

1.

Adds to alarm panel 2SA1 7 a loss of voltage alarm of 13.8 KV Fant Lines to window 2SA17-9.

2.

Adds to alarm panel 2SA1 7 a loss of voltage alarm of PSW 600V Load Center (PX1 3) or PSW 600V MCC (XPSW) to window 2SA17-21.

3.

Adds to alarm panel 2SA17 a PSW DC System Trouble alarm to window 2SA17-33.

4.

Adds to alarm panel 2SA1 2 a loss of voltage alarm to window 2SA1 2-11 for powerpanel 2KPSW.

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 8

5.

Adds to alarm panel 2SA12 a loss of voltage alarm to window 2SA12-1 for MCC 2XPSW.

6.

Changes window 2SA5-11 from EL DC System 2CA Trouble to EL DC System 2CAIPSW Trouble.

7.

Adds to alarm panel 2SA17 for KPF 9 and KPF 10 lockout alarm to window 2SA1 7-6.

8.

Adds to alarm panel 2SA1 7 for KPF 9 or KPF 10 in Local Control to window 2SA1 7-7.

9.

Adds to alarm panel 2SA1 7 for KPF 11 or KPF 12 Open to window 2SA1 7-18.

OAC Analog Points:

10.

02A1891 PSW BOOSTER PUMP SUCTION PRESSURE

11.

02A1892 PSW BOOSTER PUMP DISCHARGE PRESSURE

12.

02A1 893 PSW BOOSTER PUMP MOTOR STATOR TEMP

13.

02A1894 PSW PRIMARY PUMP SUCTION PRESSURE

14.

02A1895 PSW PRIMARY PUMP DISCHARGE PRESSURE

15.

02A1 896 PSW PRIMARY PUMP MOTOR STATOR TEMP

16.

02A1897 PSW BOOSTER PUMP MOTOR INBOARD BEARING TEMP

17.

02A1 898 PSW BOOSTER PUMP MOTOR OUTBRD BEARING TEMP

18.

02A1899 PSW BOOSTER PUMP INBOARD BEARING TEMP

19.

02A1900 PSW LINE TEMPERATURE

20.

02A1901 PSW BOOSTER PUMP OUTBOARD BEARING TEMP

21.

02A1902 PSW PRIMARY PUMP MOTOR INBOARD BEARING TEMP

22.

02A1903 PSW PRIMARY PUMP MOTOR OUTBRD BEARING TEMP

23.

02A1904 PSW PRIMARY PUMP INBOARD BEARING TEMP

24.

02A1 905 PSW PRIMARY PUMP OUTBOARD BEARING TEMP

25.

02A1918 PSW PRIMARY PUMP DISCHARGE FLOW

26.

02A1919 PSW TRANSFORMER CT6 WINDING TEMP

27.

02A1920 PSW TRANSFORMER CT7 WINDING TEMP

28.

02A1921 PSW 600V LC TRANSFORMER WINDING TEMP

29.

02A1 922 4.16 KV BUS B6T VOLTAGE

/

30.

02A1923 4.16 KV BUS B7T VOLTAGE

31.

02A1 924 PSW BATTERY ROOM 1 TEMP

32.

02A1925 PSW BATTERY ROOM 2 TEMP

33.

02A2131 PSW DC GROUND MAGNITUDE

34.

02A2132 PSW BUILDING TEMP

35.

02A2297 2A PSW FLOW

36.

02A2298 2B PSW FLOW OAC Digital Points:

37.

02D3222 HPI PUMP TRANSFER SWITCHES

38.

02D3230 2RC-155/156 POWER SOURCE

39.

02D3231 2RC-157/158 POWER SOURCE

40.

02D3232 2RC-159/160 POWER SOURCE

41.

02D3233 2A HPI PUMP POWER SOURCE

42.

02D3234 2B HPI PUMP POWER SOURCE

43.

02D3235 2HP-24 POWER SOURCE

44.

02D3236 2HP-26 POWER SOURCE

45.

02D3237 13.8 KV PSW BRKR A FROM KEOWEE STATUS

46.

02D3238 13.8 KV PSW BRKR B FROM FANT STATUS

47.

02D3239 13.8 KV PSW BRKR C FROM KEOWEE STATUS

48.

02D3240 13.8 KV PSW BRKR D FROM FANT STATUS

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 9

49.

02D3241 PSW 4.16KV B6T BRKR TROUBLE

50.

02D3242 PSW 4.16KV B7T BRKR TROUBLE

51.

02D3243 PSW LOADCENTER BREAKER TROUBLE

52.

02D3244 PSW RADWASTE POWER XPSW

53.

02D3245 PSW BATTERY CHARGER 1

54.

02D3246 PSW BATTERY CHARGER 2

55.

02D3247 PSW DC SYSTEM VOLTAGE

56.

02D3249 PSW DC GROUND SYSTEM TROUBLE

57.

02D3250 PSW FANT BREAKER B VOLTAGE

58.

02D3251 PSW FANT BREAKER B VOLTAGE AVAILABLE

59.

02D3252 PSW FANT BREAKER D VOLTAGE

60.

02D3253 PSW FANT BREAKER D VOLTAGE AVAILABLE

61.

A new PSW blocking valve control switch with position indication lamps in Unit 2 Control Room to isolate the PSW flow to both Unit 2 Steam Generators (S/G 2A & 2B).

62.

Two (2) new PSW flow controllers with flow indication and position indication lamps, one for each of the Unit 2 Steam Generators, in Unit 2 Control Room to control the high flow to individual Steam Generator PSW Main Flow control valves.

63.

Two (2) new PSW signal isolators to provide PSW S/G 2A and 2B flow indication to the OAC.

64.

Two (2) new throttle switches with position indication lamps, one for each of the Unit 2 Steam Generators, in Unit 2 Control Room to throttle individual Steam Generator PSW control bypass valves.

65.

Two (2) new Unit 2 HPI System power transfer switches with lamps in Unit 2 Control Room to select power for 2A and 2B HPI Pumps. Two new white lamps to show which pump the field alignment switch is aligned to (HPI pump 2A or 2B). Two (2) new switches will be mounted directly on each HPI transfer switch panel in the Aux Building. One switch will select Local or Remote control. The other switch will select Normal or PSW power.

66. One (1) new pump start switch with lamps to start HPI Pump 2A or 2B.

67.

A new Unit 2 HPI power transfer switch with position indication lamps in Unit 2 Control Room to select power to valve 2HP-24.

68.

A new Unit 2 HPI power transfer switch with position indication lamps in Unit 2 Control Room to select power to valve 2HP-26.

69.

A new Unit 2 HPI switch with position indication lamps in Unit 2 Control Room to control the new 2HP-139, RCP Seal Supply blocking valve.

70.

A new Unit 2 HPI switch with position indication lamps in Unit 2 Control Room to control the new 2HP-140, RCP Backup Seal Supply throttle valve.

71.

Three (3) new Unit 2 RC power transfer switches with position indication in Unit 2 Control Room to select power for the Unit 2 RV Head Vent Valves (SOV-RC-1.59 & 160) and SG High Point Vents Valves (SOV-RC-155, 156, 157 & 158).

72.

A new PSW 4KV power available lamp in Unit 2 Control Room to indicate power is available from PSW.

73.

A new PSW Pump switch with indication lamps in Unit 2 Control Room to start/stop the new PSW Booster Pump.

74.

A new PSW Pump switch with indication lamps in Unit 2 Control Room to start/stop the new PSW Primary Pump.

75.

Adds QA-1 component(s) one signal isolator, relay, position indication lamps, and non QA component(s) one flow indicator to provide flow control to the PSW Recirculation Flow valve and adds one switch for Manual/Auto position and another switch to open or close the valve when the valve is in Manual position.

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 10

76.

Two (2) new PSW switches with position indication-lamps for 100 KV Fant Line and Keowee power to open and close each breaker. They will be interlocked such that both sources cannot be closed simultaneously.

77.

A new Fant line voltage available lamp in Unit 2 Control Room to indicate power available from the 100 KV Fant Line.

78.

Two (2) new switches in the Unit 2 Control Room. One switch to select power from Breaker B, D, or Both and the other switch to select power from Breaker A, C, or Both.

79.

Two (2) new Unit 2 switches with position indication lamps in Unit 2 Control Room to select breaker (KPF-9 or KPF-1 0) as the Keowee supply to PSW.

80.

Two (2) new indicators for the position of KPF-9 and KPF-1 0.

81.

Replace the Reactor Coolant Pump Seal Injection flow indicator (2HPI P-01 52) on the 2UB1 board with a QA-1 indicator. A new QA-1 signal isolator, a new QA-1 signal conditioner and a new QA-1 power supply will also be added in Unit 2 Control Room for this instrument loop. This modification will also replace the Reactor Coolant Pump Seal Injection flow transmitter (2HPI FT-0075) in the field with a QA-1 transmitter and its associated cabling to maintain a complete QA-1 instrument loop.

Unit 3:

OAC Analog Points

1.

O3A2297 3A PSW FLOW

2.

03A2298 3B PSW FLOW OAC Digital Points

3.

03D3222 HPI PUMP XFR SWITCHES

4.

03D3230 3RC-155/156 POWER SOURCE

5.

03D3231 3RC-157/158 POWER SOURCE

6.

03D3232 3RC-159/160 POWER SOURCE

7.

03D3233 3A HPI PUMP POWER SOURCE

8.

03D3234 3B HPI PUMP POWER SOURCE

9.

03D3235 3HP-24 POWER SOURCE

10.

03D3236 3HP-26 POWER SOURCE

11.

Installation of a new PSW blocking valve control switch with position indication lamps mounted on the 3AB3 board to isolate the PSW flow to both Unit-3 Steam Generators.

12.

Installation of two (2) new PSW controllers with flow indication and position indication lamps one for each of the individual Steam Generator PSW main flow control valves mounted on the 3UB1 board to control the high flow valves by setting the desired flow to each Steam Generator.

13.

Installation of two (2) new PSW throttle valve switches with position indication lamps, one for each of the individual Steam Generator PSW control bypass valves mounted on the 3UB1 board to throttle the low flow to each Steam Generator.

14.

Installation of two (2) new Unit-3 HPI System power transfer switches with lamps mounted on the 3AB3 board to select power for the 3A and 3B HPI Pumps. Installation of two new white lamps to show alignment to HPI pump 3A or 3B mounted above the two power transfer switches (3HPI CS-PUA and 3HPI CS-PUB) on the 3AB3 board.

15.

Installation of a new pump start switch with lamps on the bench board of the 3UB1 board to start HPI Pump 3A or 3B.

16.

Installation of a new HPI power transfer switch with lamps mounted on the 3AB3 board to select power for Unit-3 HPI valve 3HP-24.

17.

Installation of a new HPI power transfer switch with lamps mounted on the 3AB3 board to select power for Unit-3 HPI valve 3HP-26.

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 11

18.

Installation of a new HPI blocking valve control switch with position indication lamps on the 3UB1 board for the 3HP-1 39, RCP seal supply blocking valve.

19.

Installation of a new HPI throttle valve control switch with position indication lamps on the 3UB1 board for the 3HP-140, RCP backup seal supply throttle valve.,,

20.

Installation of three (3) new RC power transfer switches with lamps in the Unit-3 Control Room, to select power-for the Unit-3 RV Head Vent Valves (SOV-RC-159 & 160) and SG High Point Vents Valves (SOV-RC-155 thru 158).

21.

Installation of a new PSW 4KV power available lamp mounted on the 3AB3 board in the Unit-3 Control Room to indicate power is available from PSW.

22.

Reactor Coolant Pump Seal Injection flow indicator (3HPI P 0152) will be replaced with a QA-1 indicator. A new QA-1 signal isolator, a new QA-1 signal conditioner and a new QA-1 power supply will also be added in Unit 3 Control Room for this instrument loop.

23.

Reactor Coolant Pump Seal Injection flow transmitter (3HPI FT 0075) will be replaced with a QA-1 transmitter and itsassociated cabling to maintain a complete QA-1 instrument loop.

The above list was developed in accordance with Duke Design Criteria and input from Operations.

For drawings, refer to the following files on the SharePoint:

RAI 2-30 Unit 1 Outline Unit Control Board 1UB1 RAI 2-30 Unit 1 Component Index Unit Control Board 1 UB1 RAI 2-30 Unit 2 Outline Unit Control Board 2UB1 RAI 2-30 Unit 2 Component Index Unit Control Board 2UB1 RAI 2-30 Unit 3 Outline Unit Control Board 3UB1 RAI 2-30 Unit 3 Component Index Unit Control Board 3UB1 RAI 2-30 Unit 3 Outline Auxiliary Benchboard 3AB3 RAI 2-30 Unit 3 Component Index Auxiliary Benchboard 3AB3 RAI 2-32 The licensee states in the June 26, 2008, LAR that the new PSW system switchgear will receive power from the KHUs via a tornado-protected underground feeder path. Provide the following information:

1) the type of underground cable installation, i.e., direct burial or in duct banks, manholes etc., 2) how the licensee will ensure that the proposed new underground cables remain in an environment that they are qualified for, 3) periodic inspections and testing planned for cables to monitor their performance, and 4) details regarding cable size, type, maximum loading requirements, and cable protection devices.

Duke Energy Response

1. The underground cable route from Keowee Hydro to the PSW building will be a combination of precast concrete trench boxes, duct banks and manholes. This new route will be an extension of the existing underground path from Keowee to the CT-4 block house at the plant.

Spare cables in the existing underground path will be spliced to new cables in the underground path extension to the PSW building. None of the cables will be direct buried.

2. The Keowee underground path to the PSW switchgear will be designed to preclude water entry that could wet the cables. The concrete trenches will have drains. The new duct bank conduits will be sloped towards manholes where drains are provided. Periodic inspections will

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 12 be performed on the Keowee to PSW underground path to evaluate the condition of the trenches, duct banks, manholes and drainage system.

3. The cables will be evaluated for inclusion in the ONS Insulated Cables and Connections Aging Management Program. Since the underground path from Keowee to the PSW building is designed to prevent significant exposure to moisture and most of the path is inaccessible, it is expected that the cables won't meet the criteria for periodic diagnostic testing. If subsequent periodic inspection of the Keowee to PSW building underground path determines that these inaccessible cables are exposed to significant moisture, testing will be in accordance with the ONS Cable Aging Management Program.

4. The two (2) 13.8 kV circuits from Keowee to the PSW building consist of six single conductor cables. Each conductor is 750 kcmil copper with Class B compact round stranding. The conductor shield is a thermoset semi-conducting compound extruded over the conductor. The insulation is ethylene propylene rubber (EPR) that provides an insulation level of 173% above the 15 kV nominal insulation rating. The insulation is rated at 90 °C continuous and 130*C emergency overload. The insulation shield is a semi-conducting thermoset compound applied over the insulation. Two layers of non-magnetic bronze tape shield are applied over the insulation shield. A thermoset chlorosulfonated polyethylene (Hypalon) jacket is applied over the cable core.

Maximum allowable cable loading will not exceed the continuous conductor insulation temperature rating. Depending on the cable loading scenario, anticipated cable loading is expected to range from 193 A to 559 A.

Cable protection will be provided by Keowee and PSW switchgear breakers and protective devices, which includes time-overcurrent, instantaneous overcurrent and ground fault relays.

RAI 2-33 Provide information concerning the design details for the new 100/13.8 kV substation, the PSW transformer and switchgear building power feeds, its protection, controls and alarms features.

Provide applicable single line diagram and electrical schematics.

Duke Energy Response The new PSW substation is located adjacent to SC Hwy. 183 near the ONS owner controlled area and receives power via a tap off the Fant Black 100 kV overhead path from the Duke Lee Central switching station. The major components of the PSW substation consist of a 100 kV 600 A primary-side switch, a 100 kV circuit switcher, a 22.4 MVA 100/13.8 kV three-phase oil-filled fan cooled transformer, three single-phase automatic step-voltage regulators, a 13.8 kV secondary-side vacuum circuit breaker, a DC control power system including a battery and battery charger, protective relays, alarms and communications equipment.

From the PSW substation, PSW power is provided by a 13.8 kV overhead distribution line that enters the ONS owner controlled area. It then transitions to a short section of direct-buried cable and continues in an underground ductbank leading to the PSW building inside the protected area where the cables enter the PSW building and are terminated at the 13.8 kV switchgear.

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 13 PSW substation protection includes instantaneous ground fault overcurrent, instantaneous and time-overcurrent, bus differential and undervoltage. Actuation of these relays opens the transformer primary and secondary breakers.

Operation of the PSW substation is remotely monitored and controlled by the Duke Transmission Control Center (TCC).

PSW substation alarms include communication power supply, low battery and battery ground alarm, transformer pressure relief, liquid level, cooling fan undervoltage, bank coolers shutdown, top oil temperature and winding temperature.

For drawings, refer to the following files on the SharePoint RAI 2-33 One-Line Diagram Main PSW Switchgear.pdf RAI 2-33 PSW Substation 1 Line.pdf RAI 2-33 PSW Substation 3 Line.pdf RAI 2-33 PSW Substation Battery & Charger.pdf RAI 2-33 PSW Substation Comm & Alarm.pdf RAI 2-33 PSW Substation Elementaries.pdf RAI 2-33 PSW Substation Relay Instr & Cntrls.pdf RAI 2-34 The licensee states in Enclosure 2, Figure 1 of the June 26, 2008, LAR, that two new power feeds will be installed to the auxiliary building (AB) with one power supply to the Unit 1, 2, and 3 AB

.equipment high pressure injection (HPI) pumps and vital I&C normal battery chargers and other power supply to the backup power to the Units 1, 2, and 3 pressurizer heaters. Provide the following information concerning this installation: 1) compare and contrast the existing power supply requirements for the above loads, 2) how the electrical separation, independence, and redundancy requirements are maintained, 3) summary of the voltage analyses for the equipment/components affected by this modification, 4) design details for the new power feeds to AB, 5) periodic inspections and testing schedule for the these cables to monitor their performance, and 6) provide the electrical schematics and one-line drawings for these power feeds.

Duke Energy Response

1) The existing HPI feeds are QA-1, 1200 Amp breakers at 4160V. The 1A HPI pump is fed from 1TC Breaker 9 and the 1B HPI pump is fed from 1TE Breaker 9 (see dwg 0-702). The alternate feed will be from PSW 4160V Switchgear B6T Breaker 3, and will feed the manual alignment switch that will select either the 1A or 1 B HPI pump (see dwg 0-6700). Selection of the 1 B HPI pump requires manual operation of the alignment switch in the Auxiliary Building.

The PSW supply will also be a QA-1, 1200 Amp breaker. The selection of the supply from the normal plant source or PSW will be performed in the control room using the pump's respective motor operated transfer switch. The arrangement is the same for all three units (see dwgs 0-1702 and 0-2702 for Units 2 and 3).

The existing supplies to the vital I &C battery chargers are QA-1, 200 Amp 600V breakers.

The 1CA Battery Charger is fed from 1XS1 F4A (see O-703-G, 0-705). The 1CB Battery Charger is fed from 1XS2 F4D (see O-703-G, 0-705). The supplies from PSW MCC 1XPSW breakers 4A and 4B will also be QA-1, 200 Amp 600V breakers. Automatic transfer switches

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 14 will perform the power swap upon loss of normal power (see 0-6701 and 0-703-G). The arrangement is the same for all three units (see dwgs O-1703-G and O-2703-G for Units 2 and 3).

The existing pressurizer heater feeds are non-QA, and the breaker trip settings vary from load to load due to the available kW of the.heater banks. The feeds are 1600 Amp frames with electronic trip units set for the MCC loads (lXI - 600 Amps, 1XK - 200 Amps) (2XH - 600 Amps, 2Xl - 600'Amps, 2XK - 200 Amps) (3XH - 600 Amps, 3Xl - 600 Amps, 3XK - 200 Amps) (see drawings O-703-D, O-703-E, 0-1703-C, O-1703-D, 0-2703-C, O-2703-D). The PSW feeds will be from Load Center PX1 3 breakers 2B and 3B and are QA-1. Manual transfer switches will be used to select between normal and PSW power (see drawing 0-6707).

2) The redundancy of Keowee remains unchanged as a result of this modification.

Independence and separation of the Class 1 E power system is maintained as previously described in Duke's June 24, 2010, response to RAI question 2-31.

3) The system voltages have been calculated and were compared to the acceptance criteria in OSC-9370, "Ul/2/3, PSW AC Power System Voltage and Short Circuit Analyses" Appendix C.

The calculation shows that adequate voltage is provided in both the high and low voltage scenarios. The PSW system duct banks are designed to handle the system loading. The cables that run through the duct bank have sufficient ampacity for the loads to which they are connected. The calculation also shows that all equipment device capabilities surpass the fault duty. See OSC-9370 for detailed analysis.

4) Design details for the new power feeds to the HPI pump motors, battery chargers, and pressurizer heaters are as follows:

, HPI Feeds - 3/C #4/0, Vital I&C Battery Charger Feeds -.3/C 250kcmil, Pressurizer Heater MCCs - 2 3/C 500kcmil (lXI, 2XH, 2Xl, 3XH, 3Xl), 1 3/C 500kcmil (1XK; 3XK), 1 3/C 350kcmil (2XK).

5) The new cables will be evaluated for inclusion in the Oconee Nuclear Station (ONS) Insulated.

Cables and Connections Aging Management Program where periodic inspections and testing schedule for these cables will be established to monitor their performance.

6) Electrical schematics and one-line drawings for these power feeds are:

0-702 - Unit 1 One-Line Diagram 6900V & 4160V Station Auxiliary System 0-1702 - Unit 2 One-Line Diagram 6900V & 4160V Station Auxiliary System 0-2702 - Unit 3 One-Line Diagram 6900V & 4160V Station Auxiliary System 0-6700 - One-Line Diagram Main PSW Switchgear 13.8/4.16kV System 0-6701 - One-Line Diagram Station Auxiliary Circuits 600V MCC 1XPSW 0-6702 - One-Line Diagram Station Auxiliary Circuits 600V MCC 2XPSW 0-6703 - One-Line Diagram Station Auxiliary Circuits 600V MCC 3XPSW 0-6707 - One-Line Diagram 600VAC Load Center PSWLXPX13 O-703-D - Unit 1 One-Line Diagram Station Auxiliary Circuits 600V O-703-E - Unit 1 One-Line Diagram Station Auxiliary Circuits 600V O-703-G - One-Line Diagram Station Auxiliary Circuits 600/208V/480

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 15 0-705 - One-Line Diagram 120VAC & 125VDC Station Aux Circuits Instrumentation Vital Buses OEE-117 Elementary Diagram 4160V Switchgear #1TC Unit #9 HP Injection Pump Motor No. 1A 0

OEE-1 17 Elementary Diagram 4160V Switchgear #1TE Unit #9 HP Injection Pump Motor No. 1B a OEE-217 Elementary Diagram 4160V Switchgear #2TC Unit #8 HP Injection Pump Motor No. 2A 0

OEE-217 Elementary Diagram 4160V Switchgear #2TE Unit #9 HP Injection Pump Motor No. 2B OEE-317 Elementary Diagram 4160V Switchgear #3TC Unit #8 HP Injection Pump Motor No. 3A OEE-317 Elementary Diagram 4160V Switchgear #3TE Unit #9 HP Injection Pump Motor No. 3B OEE-165 Elementary Diagram PSW 600V Load Ctr. PSWLXPX13 (2B) Feed To Manual Transfer Switch For MCC lXi OEE-165-08 Elementary Diagram PSW 600V Load Ctr. PSWLXPX13 (2B) Feed To Manual Transfer Switch For MCC lXi OEE-1 65 Elementary Diagram PSW 600V Load Ctr. PSWLXPX1 3 (3B) Feed To Manual Transfer Switch For MCC 1XK OEE-165-09 Elementary Diagram PSW 600V Load Ctr. PSWLXPX13 (3B) Feed To Manual Transfer Switch For MCC 1XK OEE-265 Elementary Diagram PSW Load Center PSWLXPX13 (4B) Feed To Manual Transfer Switch For MCC 2Xl OEE-265-08 Elementary Diagram PSW 600V Load Ctr. PSWLXPX1 3 (4B) Feed To Manual Transfer Switch For MCC 2Xl 0 OEE-265 Elementary Diagram PSW Load Center PSWLXPX1 3 (2D) Feed To Manual Transfer Switch For MCC 2XK OEE-265-09 Elementary Diagram 600V Load Ctr. PSWLXPX13 (2D) Feed To Manual Transfer Switch For MCC 2XK OEE-265 Elementary Diagram PSW Load Center PSWLXPX13 (2C) Feed To Manual Transfer Switch For MCC 2XH OEE-265-10 Elementary Diagram 600V Load Ctr. PSWLXPX13 (2C) Feed To Manual Transfer Switch For MCC 2XH OEE-365 Elementary Diagram PSW Load Center PSWLXPX13 (1 D) Feed To Manual Transfer Switch For MCC 3Xl OEE-365-08 Elementary Diagram PSW 600V Load Ctr. PSWLXPX13 (1D) Feed To Manual Transfer Switch For MCC 3Xl OEE-365 Elementary Diagram PSW Load Center PSWLXPX13 (2A) Feed To Manual Transfer Switch For MCC 3XK OEE-365-09 Elementary Diagram PSW 600V Load Ctr. PSWLXPX13 (2A) Feed To Manual Transfer Switch For MCC 3XK OEE-365 Elementary Diagram PSW Load Center PSWLXPX13 (1 B) Feed To Manual Transfer Switch For MCC 3XH OEE-365-10 Elementary Diagram PSW 600V Load Ctr. PSWLXPX13 (1B) Feed To Manual Transfer Switch For MCC 3XH OEE-609 - Elementary Diagram 4160V PSW Switchgear B6T Unit #3 Feeder To Manual Transfer Switch For HPI Pumps 1A & 1 B

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 16 OEE-609 Elementary Diagram 4160V PSW Switchgear B6T Unit #3 Feeder To Manual Transfer Switch For HPI Pumps 1A & 1B

" OEE-610 - Elementary Diagram Transfer Switch Arrangement, HP Injection Pump Motor 1A

" OEE-610 Elementary Diagram Transfer Switch Arrangement HP Injection Pump Motor 1B OEE-611 - Elementary Diagram 4160V PSW Switchgear B6T Unit #4 Feed To Alignment SW 2HPISXALGN001 For HP Injection Pumps 2A & 2B OEE-61 1 Elementary Diagram 4160V PSW Switchgear B6T Unit #4 Feed To Alignment SW 2HPISXALGN001 For HP Injection Pumps 2A & 2B OEE-612 - Elementary Diagram 2A HPI Pump Transfer Switch 2HPISXTRN002 HP Injection Pump Motor 2A OEE-612 Elementary Diagram 2B HPI Pump Transfer Switch 2HPISXTRN002 HP Injection Pump Motor 2B OEE-613 - Elementary Diagram 4160V PSW Switchgear B6T Unit #5 Feeder To Alignment SW 3HPISXALGN001 For HP Injection Pumps 3A & 3B OEE-613 Elementary Diagram 4160V PSW Switchgear B6T Unit #5 Feeder To Alignment SW 3HPISXALGN001 For HP Injection Pumps 3A & 3B OEE-614 - Elementary Diagram 3A HPI Pump Transfer Switch 3HPISXTRN001 HP Injection Pump Motor 3A 0

OEE-614 Elementary Diagram 3BA HPI Pump Transfer Switch 3HPISXTRN002 HP Injection Pump Motor 3B 0-1703-C - Unit 2 One-Line Diagram Station Auxiliary Circuits 600V O-1703-D - Unit 2 One-Line Diagram Station Auxiliary Circuits 600V O-1703-G - Unit 2 One-Line Diagram Station Auxiliary Circuits 600V 0-1705 - One-Line Diagram 120VAC & 125VDC Station Aux Circuits Instrumentation Vital Buses 0 0-2703-C - Unit 3 One-Line Diagram Station Auxiliary Circuits 600V O-2703-D - Unit 3 One-Line Diagram Station Auxiliary Circuits 600V O-2703-G - Unit 3 One-Line Diagram Station Auxiliary Circuits 600/208V 0-2705 - One-Line Diagram 120VAC & 125VDC Station Auxiliary Circuits Instrumentation Vital Buses.

RAI 2-36 Describe in detail how the 125 vdc vital I &C primary and backup power cables and the KHU emergency start circuitry will be rerouted from the turbine building (TB) to the AB.

Duke Energy Response The existing routing of the 125 VDC Vital IC& primary and backup power cables and Keowee emergency start cables are vulnerable to the affects of HELB or tornado induced damage in the Turbine Building and will be rerouted out of the Turbine Building as part of the Protected Service Water Project.

Units 1, 2, and 3 125 VDC Vital I&C Battery System primary and backup cables that are susceptible to the affects of tornado/HELB damage will be replaced by new cables routed through the Auxiliary Building and therefore protected from the affects of HELB or tornado damage in the Turbine Building.

Enclosure - Duke Energy RAI Re'sponses August 31, 2010 Page 17 The new Keowee emergency start cable route starts at the Keowee main control room and travels to existing Keowee termination cabinets KHU-1 and KHU-2. From KHU-1 and KHU-2, existing spare cables in the Keowee underground path will be used which end at the Oconee Unit 1 blockhouse in existing Oconee termination cabinets KHU-1A and KHU-2A.

New cables will be routed from KHU-1A and KHU-2A through an extension of the existing Keowee underground path to the PSW building and from there to new cabinets KHU-1B and KHU-2B located in the Auxiliary Building. Additional emergency start cables will also be rerouted from the 230 kV switchyard relay house through the new underground path extension to new cabinets KHU-1 B and KHU-2B. From cabinets KHU-1 B and KHU-2B, new cables will be installed to the cable rooms where they will be connected to existing emergency start cables that come from the control rooms.

RAI 2-40 To ensure licensing-basis clarity and component operability, Technical Specifications (TSs) need to properly address the tornado mitigation systems (e.g., protected service water/ standby shutdown facility, etc.) in a manner that is consistent with the Standard TS requirements that have been established for the functions that are being performed by these systems. For example, the minimum required mission time should be 7 days and the Completion Times should be limited to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> in most cases for the SSF and the PSW including maintenance. Justify the existing limiting condition for operation (LCO) (e.g. the SSF can be maintained out of service for 45 days for all 3 units while maintenance is being performed on the system) times for the SSF in the current TSs and the proposed LCO for the PSW system. The proposed tornado mitigation strategy relies solely on the SSF and the repair of the PSW system to achieve and maintain hot standby and entry into cold shutdown following a design basis tornado.

Duke Energy Response The original 1973 Final Safety Analysis Report contained a description of tornado protection design requirements which relied on:

Physical protection of Class 1 structures, such as the Reactor Building (RB) and selected portions of the Auxiliary Building (AB),

Sufficient supply of secondary side cooling water for safe shutdown (SSD),

Diverse sources of emergency power and, Physical separation of systems as defense against tornado missiles. The application of physical separation was applied to the 'A' and 'B' steam generator (SG) paths of the station Auxiliary Service Water (ASW) system since either path was considered capable of providing the necessary flow to restore secondary side decay heat removal ((SSDHR) and was physically separated by the RBs. Additionally, physical separation was applied to the Keowee Hydro Units (KHU) and the station. The NRC acknowledged the use of physical separation as a viable means of defending against missiles in the original Safety Evaluation Report (SER), stating, "With regard to Class I (seismic) components in the AB [such components] will be protected by concrete walls and roofs to prevent potential missile penetration, or be separated to prevent failures in redundant systems from such missiles."

The current tornado licensing basis (CLB) credits the redundant and diverse sources of secondary side decay heat removal (SSDHR) and reactor coolant makeup/seal cooling (RCMU).

Specifically, a damaged unit's SSDHR will be supplied by either its own' or from another units'

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 18 emergency feedwater, the tornado-protected, low-head, station auxiliary service water (ASW) pump, or the high-head Standby Shutdown Facility (SSF) Auxiliary Service Water (ASVV) pump.

The station ASW system is considered to be the "tornado-protected" means of accomplishing the SSDHR function because it was able to provide water to the steam generators' (SGs) through protected or physically separated lines, it could be powered from an emergency bus, and it had approximately 37 days worth of water stored in the buried CCW piping that was available for feeding the SGs. The need to adopt this approach was necessary since the EFW system of the affected unit is not tornado-protected and cannot be relied upon following a tornado. The SSF ASW system was specifically recognized and credited for accomplishing the SSDHR function in the event that a tornado disables the Keowee Hydro Units (KHUs), the plant's emergency power source, resulting in a station blackout situation since off-site power is assumed to be lost due to the tornado.

For RCMU, either a SSF RCMU pump or HPI pump is used. The borated water storage tank (BWST) is the water source for the HPI pump or alternatively, the pump can be manually aligned to the spent fuel pool (SFP) should the BWST be unavailable. For the SSF RCMU pump, water from the SFPs is used and reactor coolant system (RCS) inventory is managed from the SSF control room (CR).

The current mitigation strategy contains several time-critical operator actions which are needed to align and power both the station ASW pump and one High Pressure Injection (HPI) pump to the tornado-protected ASW switchgear located in the auxiliary building.

The proposed tornado mitigation strategy significantly improves on the current strategy that is based solely on probabilistic insights, to one that contains a deterministic solution which relies on the tornado-protected SSF systems for SSDHR and reactor coolant makeup/seal injection. The objective of this strategy will maintain the plant in MODE 3 (Hot Standby) until damage control measures are implemented to cool the units to -250 degrees F. 'Either the tornado-protected SSF system or the Protected Service Water (PSW) system (including one HPI pump), has the capability to satisfy the maintained Mode 3 objective. The proposed tornado modifications will significantly reduce the station's risk profile while enhancing the ability to mitigate a tornado, including a reduction in the number of time-critical operator actions. Specifically, the proposed mitigation strategy replaces the current station ASW pump, which requires manual alignment to the ASW switchgear in addition to having to manually depressurize the intact SG, with a more reliable SSF system that can be started much sooner and requires much less operator intervention. The SSF is also regulated by a TS as opposed to a SLC for the station ASW pump.

Technical Specification discussion The regulatory basis for tornado protectionof equipment originates from principal design criteria 2 (pre-GDC) as described in UFSAR 3.1.2 and since a tornado is a design criterion, it does not constitute a design basis accident or transient as described in 10 CFR 50.36(c)(2)(ii). In addition, Duke Energy could find no historical correspondence that commits Oconee to comply with the tornado design requirements contained in other regulatory documents including the Standard Review Plan.

During initial discussions with the Staff regarding the proposed PSW system; Duke Energy was unable to establish a firm regulatory basis that would require a PSW TS. A PSW TS was proposed primarily because PSW is a functional backup to the single-train SSF systems that are already in the ONS TSs. Since both the SSF and PSW systems perform similar functions, the PSW TS limiting conditions for operation (LCO) and allowed outage times (AOTs) submitted, closely mimic those that are already described in the current SSF TS.

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 19 The SSF and PSW systems do not mitigate design basis accidents (DBAs). Neither SSF nor PSW operability requirements readily fit into the standardization process established by NUREG 1430 [Standard Technical Specifications], i.e., the document does not contain any criteria for a protected service water system. The system in the NUREG with the closest fit is EFW, but EFW requirements are tied to mitigation of DBAs.

The existing limiting conditions for operation (LCOs) for the SSF systems and the proposed LCOs for the PSW systems are justified based on the overall risk improvement that is achieved by the installation of the PSW system. The current ONS tornado licensing basis relies on redundant and diverse SSDHR sources and primarily on the tornado-protected SSF Auxiliary Service Water system for acceptability. In order to simplify the licensing basis, the requested tornado licensing amendment credits only the SSF for mitigation of tornado-related damage to the station. The redundancy and diversity of SSDHR sources remains unchanged and is in fact improved by the addition of the PSW system. The availability of the redundant, diverse SSDHR sources (including PSW) are (or will be) in the station's PRA. As a result, the SSF system's-risk worth is expected to decrease with the completion of the PSW project. A decrease in risk worth of the SSF systems justifies the continued acceptability of the exiting SSF LCOs.

RAI 2-41 Portions of the reactor coolant system (RSC) and other high energy lines in the plants could possibly be damaged by tornado-generated missiles, resulting in a significant loss-of-coolant accident or high energy line break. Discuss how this vulnerability is being addressed in the new tornado mitigating strategies.

Duke Energy Response Aloss of coolant accident (LOCA) is not postulated to occur as a result of a tornado. The Reactor Coolant System (RCS), by virtue of its location within the Reactor Building (RB), is protected from tornado damage. The RCS has two containment penetrations with piping routed outside the RB.

Both of these penetrations involve sample lines for the RCS. One of the lines provides for normal sampling, while the other provides for post-accident sampling capability for the RCS. Both sample lines are normally isolated by closed valves located inside the RB. Therefore, both sample lines were excluded from the scope of targets to be considered in the TORMIS analysis.

The High Pressure Injection (HPI) system has interconnections with the RCS. The letdown line connects the RCS to the HPI system. The letdown line penetrates the RB in the East Penetration Room (EPR). A rupture in the letdown line outside the RB would result in a loss of reactor coolant.

The letdown line is equipped with an isolation valve inside the EPR. The isolation valve is pneumatically operated and designed to fail closed on a loss of air or power. The section of letdown piping between the reactor building and the isolation valve was evaluated as a target in the TORMIS analysis.The HPI system also has connections to the RCS for Reactor Coolant Pump (RCP) seal injection and RCS makeup lines (Trains A and B) to the RCS cold legs.

Ruptures in the piping outside the RB will not result in a LOCA. Each of the HPI lines located outside the RB are isolated from the RCS by check valves located inside the RB.

The Low Pressure Injection (LPI) system has interconnections with the RCS. The decay heat drop line for Unit 1 penetrates the RB in the West Penetration Room (WPR) and is routed through the Cask Decontamination Tank Room (CDTR) (located below the WPR) before going below grade elevation. The decay heat drop lines for Units 2 and 3 penetrate the RB inside the Auxiliary Building (AB) below grade elevation. The LPI system discharges water via two different lines back to the RCS. One line penetrates the RB in the EPR, while the other line penetrates theRB in the

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 19 The SSF and PSW systems do not mitigate design basis accidents (DBAs). Neither SSF nor PSW operability requirements readily fit into the standardization process established by NUREG 1430 [Standard Technical Specifications], i.e., the document does not contain any criteria for a protected service water system. The system in the NUREG with the closest fit is EFW, but EFW requirements are tied to mitigation of DBAs.

The existing limiting condition for operation (LCOs) for the SSF systems and the proposed LCOs for the PSW systems are justified based on the overall risk improvement that is achieved by the installation of the PSW system. The current ONS tornado licensing basis relies on redundant and diverse SSDHR sources and primarily on the tornado-protected SSF Auxiliary Service Water system for acceptability. In order to simplify the licensing basis, the requested tornado licensing amendment credits only the SSF for mitigation of tornado-related damage to the station. The diversity of SSDHR sources remains unchanged and is in fact improved by the addition of the PSW system. The availability of the diverse SSDHR sources are in the station's PRA. As a result, the SSF system's risk worth is expected to decrease with the completion of the PSW project. A decrease in risk worth of the SSF systems justifies the continued acceptability of the*

exiting SSF LCOs.

RAI 2-41 Portions of the reactor coolant system (RSC) and other high energy lines in the plants could possibly be damaged by tornado-generated missiles, resulting in a significant loss-of-coolant accident or high energy line break. Discuss how this vulnerability is being addressed in the new tornado mitigating strategies.

Duke Enerqy Response A loss of coolant accident (LOCA) is not postulated to occur as a result of a tornado. The Reactor Coolant System (RCS), by virtue of its location within the Reactor Building (RB), is protected from tornado damage. The RCS has two containment penetrations with piping routed outside the RB.

Both of these penetrations involve sample lines for the RCS. One of the lines provides for normal sampling, while the other provides for post-accident sampling capability for the RCS. Both sample lines are normally isolated by closed valves located inside the RB. Therefore, both sample lines were excluded from the scope of targets to be considered in the TORMIS analysis.

The High Pressure Injection (HPI) system has interconnections with the RCS. The letdown line connects the RCS to the HPI system. The letdown line penetrates the RB in the East Penetration Room (EPR). A rupture in the letdown line outside the RB would result in a loss of reactor coolant.

The letdown line is equipped with an isolation valve inside the EPR. The isolation valve is pneumatically operated and designed to fail closed on a loss of air or power. The section of letdown piping between the reactor building and the isolation valve was evaluated as a target in the TORMIS analysis. The HPI system also has connections to the RCS for Reactor Coolant Pump (RCP) seal injection and RCS makeup lines (Trains A and B) to the RCS cold legs.

Ruptures in the piping outside the RB will not result in a LOCA. Each of the HPI lines located outside the RB are isolated from the RCS by check valves located inside the RB.

The Low Pressure Injection (LPI) system has interconnections with the RCS. The decay heat drop line for Unit 1 penetrates the RB in the West Penetration Room (WPR) and is routed through the Cask Decontamination Tank Room (CDTR) (located below the WPR) before going below grade elevation. The decay heat drop lines for Units 2 and 3 penetrate the RB inside the Auxiliary Building (AB) below grade elevation. The LPI system discharges water via two different lines back to the RCS. One line penetrates the RB in the EPR, while the other line penetrates the RB in the

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 20 WPR. The decay heat drop line (for all three units) is normally isolated from the RCS by two closed motor-operated valves located inside the RB. The LPI return lines are isolated from the RCS by check valves located inside the RB. Since the LPI system is normally isolated from the RCS, failures in the LPI piping outside the RB would not result in a LOCA.

The postulation of high energy line breaks was not generically evaluated as part of the requested amendment to the tornado licensing basis. The license amendment request establishes the SSF as the credited means for establishing safe shutdown for the Oconee units. Since the SSF Reactor Coolant Makeup (RCM) system does not have sufficient capacity necessary to accommodate the RCS shrinkage associated with a loss of main steam pressure boundary or the loss of RCS inventory resulting from a loss of reactor coolant pressure boundary, the main steam and reactor coolant pressure boundaries are considered to be part of the tornado-protected means for establishing safe shutdown. As described in Attachment 4 of the LAR, the unprotected and unisolated main steam piping and reactor coolant piping that could jeopardize mitigation using the SSF have been included as potential missile targets in the TORMIS analysis. The scope of the main steam pressure boundary and reactor coolant pressure boundary was provided in section 5.2 of Attachment 4 to the LAR.

RAI 2-44 Discuss how cold shutdown will be achieved following a design basis tornado including, a.) Define a time for achieving cold shutdown based on the worst case repairs that will need to be made following a tornado; b.) recognition of the strategy/systems to be used (e.g., residual heat removal (RHR), low-pressure service water, high-pressure injection (HPI), pressurizer heaters, atmospheric dump valves, instruments, etc.;.) identification of specific vulnerabilities that need to be addressed, equipment to be staged (e.g., cable); and, c.) a human factors assessment of effort/repair that is consistent with the NRC review standards/guidance.

Duke Energy Response a) ONS can find no evidence within the UFSAR or licensing correspondence with the NRC that would indicate that ONS has committed to achieve cold shutdown within specific time for tornado mitigation. Irrespective of this fact, prudency would dictate that after a damaging tornado event, Duke Energy would expeditiously transition from the SSF maintaining the unit(s) in a hot standby condition to restoring plant equipment needed to establish a RCS cool down in a safe and controlled manner. However, the post-tornado recovery strategy describes a cooldown of the RCS to approximately 250 0F, not cold shutdown. Long term decay heat removal is provided by supplying lake water to the steam generators and steaming to atmosphere.

b) Within the established SSF mission time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, damage assessments and repairs (i.e.,

damage control measures) would be performed to restore vulnerable equipment needed for a unit cooldown to approximately 250'F. Provided below is a summary of assessment and recovery actions.

1. Assess and restore power to the PSW Electrical Distribution System In the unlikely event that both of the PSW electrical power sources are lost (13.8 kV overhead line and the KHUs), Duke will utilize damage repair procedures as well as local and Duke's extensive company resources and materials, to restore one of PSW's power sources within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. For this scenario, depending on the extent of damage to each

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 21 source, the primary focus of Duke's restoration plans will be the expedited recovery of emergency power from the system with the shortest return to service time.

2. Assess and restore power to the 125VDC/120VAC Vital Instrumentation and Control System The 125VDC Vital I&C Control Batteries are located in three different rooms (one for each unit) inside the Auxiliary Building. The battery rooms are located at elevation 809'-3" (above grade elevation). Each of the rooms has one exterior wall. The exterior walls were analyzed for tornado wind and differential pressure effects. The exterior walls were found to be adequate using median material properties and allowable stresses. A maximum tornado wind speed of 300 mph was used in the analysis. Each unit's control batteries are physically separated from the batteries of another unit to minimize the risk of failure to the 125VDC Vital I&C system due to tornado missile damage. If the Unit 1 control batteries were damaged, the Unit 1 125VDC Vital I&C would continue to be powered from the Unit 2 control batteries. Similarly, Unit 2 is backed up by Unit 3 and Unit 3 is backed up by Unit 1.

The battery chargers, associated DC buses, and inverters (for the 120VAC Vital I&C) for each unit are physically located in the associated unit's electrical equipment room. The tornado protection afforded to the electrical equipment room was discussed in the LAR and therefore, the equipment located inside these rooms is assumed to remain available.

However, the normal power supplies for the battery chargers (located in the Turbine Building) are vulnerable to tornado damage and are assumed to be lost. This vulnerability was eliminated by providing an alternate power supply from the PSW electrical distribution system to each unit's battery chargers. Once power has been established to the PSW electrical distribution system, the 125 VDC Vital I&C system can be restored.

3. Assess and restore power to the Pressurizer Heaters Pressurizer heaters are not required for plant cooldown. However, once the cooldown has been completed and it is desired to maintain the RCS in a natural circulation condition with decay heat removal via the steam generators, the pressurizer heaters would be energized to maintain a steam bubble in the pressurizer. The pressurizer heaters not powered from the SSF are vulnerable. The motor control centers (MCCs) that provide power to the heaters are located inside the East Penetration room. Damage to MCCs or associated cabling would need to be assessed and repaired. If the damage is too extensive for timely repair, pressurizer heaters could be reenergized from the MCCs located inside the SSF.

The SSF can be powered from the PSW electrical system should the SSF diesel generator become unavailable.

4. Assess and restore power to electrically operated valves located inside the Reactor Building The electrically operated valves needed for plant cooldown include:

Pressurizer Power Operated Relief Valve (PORV) for RCS depressurization RV Head Vents to support a natural circulation cooldown Post Accident Liquid Sampling (PALS) system for boron sampling of the RCS The Pressurizer PORV and the PALS valves are powered from the plant 120VAC Vital I&C Power Panelboards (located inside the cable spreading room). However, the cabling to the valves pass through the penetration rooms. Damaged cabling would needlto be assessed and replaced (as necessary). If cabling from the 120VAC Vital I&C Power Panelboards cannot be replaced, a portable valve control panel with associated cabling could be installed to allow operation of these valves. The portable valve control panel

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 22 would be energized from the SSF with SSF power being provided by the PSW electrical system if the SSF diesel generator becomes unavailable.

The RV Head Vents are powered from 120VAC power panelboards located in the cable spreading room. The normal source of power to the panelboards could be lost, but the PSW electrical system can be aligned to power the valves. However, the cabling to the valves pass through the penetration rooms. Damaged cabling would need to be assessed and replaced (as necessary). If cabling. cannot be replaced, a portable valve control panel with associated cabling could be installed to allow operation of these valves. The portable valve control panel would be energized from the SSF with SSF power being provided by the PSW electrical system if the SSF diesel generator becomes unavailable During plant cooldown, it is desired to isolate the core flood tanks (CFT) from the RCS by closing the CFT discharge valves. The power supply and the cabling to these valves are vulnerable to tornado damage. A portable valve control panel with associated cabling would need to be installed to allow operation of these valves. The portable valve control panel would be energized from the SSF with SSF power being provided by the PSW electrical system if the SSF diesel generator becomes unavailable.

5. Assess and restore Main Control Room instrumentation and display The following indications would be desired in the main control room to support a plant cooldown:

RCS Pressure and Temperature RCS Water Level SG Water Level PSW Flow to the SGs HPI Flow The above indications provided by instruments and displays are powered from the unit's 125VDC/120VAC Vital I&C Power system, with the exception of the PSW flow to the SGs.

The unit's vital I&C power systems are provided an alternate power source from the PSW electrical distribution system. The PSW flow to the SGs is powered from the PSW 120VAC power system.

The transmitters for RCS temperature, Pressurizer water level and SG water level are located inside the Reactor Building. The cabling for these transmitters pass through the penetration rooms. Damaged cabling would need to be assessed and repaired (as necessary). The tubing used to provide RCS pressure, RCS Hot Leg and Reactor Vessel water levels is routed through the east penetration rooms. The tubing would need to be assessed and repaired to restore the indications. If the RCS and SG instrumentation cannot be restored within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, instrumentation at the SSF would be relied upon for plant cooldown. Power to the SSF can be supplied from the PSW electrical system if the SSF diesel generator becomes unavailable.

HPI flow is monitored by three different transmitters, the "A" and "B" Header flow and the RCP seal injection flow transmitters. The "A" and "B" header flow and the RCP seal injection flow transmitters are located below grade in the Auxiliary Building. The cabling for the transmitters are not routed through tornado vulnerable areas.

6

6. Assess and repair the HPI Lines

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 23 The HPI system must be restored to provide RCP seal cooling and RCS makeup for plant cooldown. The suction piping from the BWST to the HPI pumps is protected. However the HPI pump discharge piping above grade elevation is vulnerable to damage.

The "A" HPI line is routed on the east side of the Reactor Building from grade elevation up to the East Penetration Room. If this line is damaged by a tornado missile, the line can be isolated by a manual isolation valve below grade elevation. The HPI pump discharge can be aligned to the "B" HPI line for RCS makeup.

The "B" HPI line is routed on the west side of the Reactor Building from grade elevation up to the West Penetration Room. If this line is damaged by a tornado missile there is no impact to the RCS makeup path via the "A" HPI line.

The HPI header cross-connect line and the RCP seal injection lines are initially routed from grade elevation up to the East Penetration Room. Two of the RCP seal injection lines are then routed to the West Penetration Room. The HPI header cross-connect line branches to "A" HPI line and the "B" HPI line. Damage to the HPI header cross-connect line and the RCP seal injection lines would need to be assessed and repaired prior to transfer from the SSF RCMU system to the HPI system for RCP seal cooling.

7. Assess and restore both PSW flow paths to the SGs Transition from the SSF ASW system to PSW relies upon restoration of PSW to both SGs.

The majority of the PSW piping will be located below grade elevation. However, the PSW supply headers to the SGs will be routed above grade elevation. The "A" SG supply will be routed on the east side of the reactor building above grade to the East Penetration Room, while the "B" SG supply will be routed on the west side of the reactor building above grade to the West Penetration Room. Damage to either SG supply headers from PSW would need to be assessed and repaired. If repairs cannot be completed within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, the SSF ASW system could be utilized to enable a plant cooldown until the PSW headers are repaired. The SSF can be powered from the PSW electrical system if the SSF diesel generator becomes unavailable.

8. Assess and restore atmospheric vent flow path for each SG For each SG, no repairs to the main steam atmospheric vent flow path are expected to be required. The main steam pressure boundary is being protected by the installation of the MSIVs. The modification that installs the MSIV will also provide a tornado protected means of venting steam to the atmosphere for each steam generator.

Recovery of the above equipment would enable a natural circulation cooldown of the unit(s).

No minimum cooldown rate has been established in the LAR. Therefore, no commitment has been established for achieving an RCS temperature of -250°F within a prescribed time interval.

c) The damage assessments and repairs described above to restore vulnerable equipment needed for a unit cooldown to approximately 250°F would be accomplished utilizing station procedures. The preparation, review and approval of station procedures are performed in accordance with section 17.3.2.14 of the Duke QA Topical Report. The damage assessment and repair procedures are classified as permanent technical procedures that would be utilized after the plant has been brought to a safe shutdown condition using the existing emergency procedure for the SSF. The purpose of the damage assessment procedures is to determine the availability of unprotected systems and components utilized during a plant cooldown. The repair procedures are employed to restore any damaged equipment discovered during the

Enclosure - Duke Energy RAI Responses August 31, 2010 Page 24 assessment. The assessment and repair procedures would be initiated after the Emergency Response Organization (ERO) has been staffed. These procedures are designated as the following types:

Emergency Response Procedures (RP)

Operating Procedures (OP)

Instrument and Electrical Procedures (IP)

Mechanical Maintenance Procedures (MP)

" Abnormal Maintenance Procedures (AM)

Emergency Maintenance Procedures (EM)

A validation and verification process is in-place to address the adequacy of technical procedures.

RAI 2-46 Justify the proposed tornado mitigation strategy conclusion that equipment in-the plant necessary to achieve and maintain hot standby is protected by adjacent structures and is not hardened to prevent a tornado missile strike [i.e., EPR].

Duke Energy Response In the proposed tornado mitigation strategy, the SSF system is the only assured system to survive after a severe tornado event and is credited to be able to achieve and maintain hot standby (Mode

3) for the three Oconee units for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. This survival assurance is verified by a combination of structural protection and from the results of a TORMIS evaluation. The use of the NRC-approved TORMIS methodology confirmed that the risk from missile damage was acceptably low to tornado missile vulnerable areas of the SSF structure as well as other SSCs required for safe shutdown. As a result, there is reasonable assurance that a tornado missile will not prevent the SSF system from fulfilling its design function.

The SSF is a seismic Category I structure housing subsystems that provide adequate secondary side decay heat removal (SSDHR) and reactor coolant makeup/seal injection (RCMU) to all three units. The portions of the SSF piping and control cables that traverse from the tornado-protected SSF structure up through the auxiliary building (via the west penetration and cask decontamination rooms) and ending in the reactor building are protected from the direct effects of a tornado. The west penetration and cask decontamination room walls have been both physically upgraded to resist the effects of tornado loads and certain critical equipment located within these rooms has been evaluated using TORMIS. Other than being adjacent to-the tornado-protected reactor building, the East Penetration room (EPR) is not physically protected from the effects of a tornado, i.e., the room contains a HELB blowout panel. However, there is no SSF equipment in the EPR.