ML102010678

OL - 7-16-10__Response to NRC RAI on WBN U2 Fire Protection Program

ML102010678
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Site:	Watts Bar
Issue date:	07/16/2010
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WBN2Public Resource From: Hamill, Carol L [clhamill@tva.gov]

Sent: Friday, July 16, 2010 12:14 PM To: Wiebe, Joel; Raghavan, Rags; Milano, Patrick; Campbell, Stephen Cc: Arent, Gordon; Crouch, William D; Knuettel, Edward Terry; Boyd, Desiree L

Subject:

7-16-10__Response to NRC RAI on WBN U2 Fire Protection Program Attachments: image001.png; 7-16-10__Response to NRC RAI on WBN U2 Fire Protection Program.pdf Please see attached letter that was submitted to NRC today.

Carol L. Hamill Licensing/Quality Assurance WBN Unit 2 Project, EQB 1B WBN 4233653177

4233653833 clhamill@tva.gov 1

Hearing Identifier: Watts_Bar_2_Operating_LA_Public Email Number: 46 Mail Envelope Properties (25547F570B005144A141ECCA95DA1AB20CEDA0E3)

Subject:

7-16-10__Response to NRC RAI on WBN U2 Fire Protection Program Sent Date: 7/16/2010 12:14:02 PM Received Date: 7/16/2010 12:14:36 PM From: Hamill, Carol L Created By: clhamill@tva.gov Recipients:

"Arent, Gordon" <garent@tva.gov>

Tracking Status: None "Crouch, William D" <wdcrouch@tva.gov>

Tracking Status: None "Knuettel, Edward Terry" <etknuettel@tva.gov>

Tracking Status: None "Boyd, Desiree L" <dlboyd@tva.gov>

Tracking Status: None "Wiebe, Joel" <Joel.Wiebe@nrc.gov>

Tracking Status: None "Raghavan, Rags" <Rags.Raghavan@nrc.gov>

Tracking Status: None "Milano, Patrick" <Patrick.Milano@nrc.gov>

Tracking Status: None "Campbell, Stephen" <Stephen.Campbell@nrc.gov>

Tracking Status: None Post Office: TVACOCXVS2.main.tva.gov Files Size Date & Time MESSAGE 225 7/16/2010 12:14:36 PM image001.png 6804 7-16-10__Response to NRC RAI on WBN U2 Fire Protection Program.pdf 173832 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received:

Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381-2000 July 16, 2010 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Stop: OWFN P1-35 Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 2 10 CFR 50.4 NRC Docket No. 50-391

Subject:

WATTS BAR NUCLEAR PLANT (WBN) UNIT 2 - REQUEST FOR ADDITIONAL INFORMATION REGARDING FIRE PROTECTION PROGRAM (TAC NO. ME0853)

Reference:

NRC letter dated June 11, 2010, Watts Bar Nuclear Plant, Unit 2 - Request for Additional Information Regarding Fire Protection Program (TAC NO. ME0853 The purpose of this letter is to provide additional information as requested by NRC (Reference) in support of its review of the Fire Protection Program for WBN Unit 2. The following provides TVA responses to NRC requests for additional information:

NRC Request:

The NRC staff requests that TVA submit the following information in order for the staff to complete its review of the fire protection system for WBN Unit 2:

1. WBN Fire Protection Report

a. The proposed revision of the WBN Unit 2 portion of the Fire Protection Report, with notation of all changes made after the last approval of the report by the NRC.

b. The proposed revision of the common portions of the WBN Fire Protection Report, with notation of all changes made after the last approval of the report by the NRC.

c. For each change that was previously approved by the NRC:

(i) Provide detail concerning the approval, (ii) A reference to the approving document, and (iii) An excerpt documenting the approval.

d. For each change that was not previously approved by the NRC:

(i) Provide a sumary description of the evaluation, and (ii) TVAs justification for the acceptability of the change.

U.S. Nuclear Regulatory Commission Page 2 July 16, 2010 TVA Response:

1. a. and b.

The current Unit 1/2 Fire Protection Report addresses both units; however, it requires updating to address, among other things, the dual unit safe shutdown analysis, Unit 2 fire analysis volumes, and Unit 2 specific Operator Manual Actions (OMAs). The current version of the report will be updated by adding information to account for the current design of Unit 2. Portions of the report address programmatic aspects (e.g., fire brigades, fire watches, etc.) that are not affected by the operation of Unit 2. These parts will be submitted to the NRC by August 6, 2010. As discussed below, TVA is performing modifications related to fire protection. Additionally, TVA is issuing modifications to address other unrelated issues. Since there is a potential for these other modifications to impact the Fire Protection Report, TVA is conducting a fire protection review of the entire set of design changes issued for Unit 2. TVA is in the process of finalizing the Fire Protection Report to address both the fire protection-related modifications and the other modifications. This review will be completed in December, 2010. TVA will submit the complete Unit 1/2 Fire Protection Report by December 17, 2010.

1.c.

The Unit 1/2 Fire Protection Report, Revision 5, was approved by the NRC. NRC approval of the Fire Protection Report was documented in Supplemental Safety Evaluation Reports (SSERs) 18 and 19, Section 9.5.1 and Appendix FF. The report is currently at Revision 40.

The changes between Revision 5 and 40 have been evaluated under the License Condition and have not received explicit NRC approval.

1.d.

The changes to the Fire Protection Report between Revision 5 and Revision 40 are not marked explicitly in the current revision; therefore, TVA will provide a separate markup, description, and justification of the changes made since NRC approved the report. This information will be provided by August 30, 2010.

2. Multiple Spurious Actuations Regarding TVAs review of multiple spurious actuation scenarios that could affect post-fire safe shutdown, provide:

a. A description of the method TVA used to systematically identify possible multiple spurious actuation scenarios that could affect safe shutdown,

b. A description of each of the scenarios identified by the analysis, including how post-fire safe shutdown is ensured for each scenario.

U.S. Nuclear Regulatory Commission Page 3 July 16, 2010 TVA Response:

2 .a.

The WBN Fire Protection Report contains the programmatic requirements which apply to both Unit 1 and Unit 2 and the safe shutdown analysis results for Unit 1. The report will be enhanced to include the results of the Unit 2 safe shutdown analysis. Recently, WBN developed the Unit 1 Multiple Spurious Operation (MSO) list using the guidance of Regulatory Guide 1.189 Revision 2 and NEI-00-01 Revision 2. The WBN Unit 1 MSO scenario list was prepared using the expert panel review process described in NEI-00-01, Revision 2. The Unit 2 evaluation of MSOs will utilize the same methodology. Since WBN Unit 2 is essentially identical to WBN Unit 1 and very similar to its sister plant, Sequoyah Units 1 and 2, the plant specific list of MSO scenarios prepared for WBN Unit 1 is being used for developing the WBN Unit 2 MSO scenarios. Additionally the Sequoyah plant-specific MSO scenario list was reviewed for possible scenarios resulting from dual unit operation as opposed to the WBN Unit 1 single unit list. No additional scenarios were identified.

2.b.

The Table in Enclosure 1 to this letter provides a description of the dual unit MSO scenarios identified by the above described analysis. TVA will provide a description of how safe shutdown is ensured for each scenario by August 20, 2010.

3. Operator Manual Actions For all OMAs needed to assure post-fire safe shutdown when redundant trains are in the same fire area outside of primary containment, provide:

a. A description of the method that TVA used to evaluate OMAs,

b. A description of, and a schedule for, completing plant modifications that are being performed to reduce OMAs,

c. A list of OMAs that could not be resolved through modifications,

d. The plan and schedule for submitting a request for NRC approval of the OMAs that could not be resolved through modifications.

TVA Response:

3.a.

The WBN Unit 2 OMAs were developed starting with the Unit 1 post fire safe shutdown analysis and OMAs which were approved in NRC SSER 18. The OMAs were previously demonstrated for Unit 1 to be feasible and reliable. Unit 2 is performing modifications to reduce the number of time critical (<60 minutes) OMAs. The Unit 2 OMAs will either be the same as Unit 1 or slightly different (i.e., similar) due to the modifications being performed to reduce the number/complexity of OMAs. For example, in Unit 1 the action may involve tripping a breaker or removing fuses, whereas in Unit 2 the action may be to operate a local

U.S. Nuclear Regulatory Commission Page 4 July 16, 2010 switch. Either action will accomplish the same result and are thus similar. This is described as same/similar in the discussion below.

The OMA fall into four categories:

1) Control Bay - The control building is an alternative shutdown area per Appendix R, III.G.3. OMAs the same/similar as Unit 1 will be utilized for Unit 2.

2) Hot Shutdown Greater Than 60 Minutes - OMAs that are the same/similar as Unit 1 will be utilized for Unit 2.

3) Hot Shutdown Less Than 60 Minutes - Modifications will be used to eliminate OMAs or reduce the number of fire zones which rely on the OMAs. Remaining OMAs will be the same/similar as Unit 1. See item 3c below for further information.

4) Cold Shutdown - OMAs the same/similar as Unit 1 will be utilized for Unit 2.

3.b.

OMA reduction modifications are integrated into system modification packages and are thus not tracked separately from other modifications. The modifications for each system will be completed prior to system turnover. The types of modifications performed to reduce reliance on OMAs include:

a. Cable rerouting to provide separation between redundant shutdown paths.

b. Circuit modifications to prevent spurious actuation of components.

c. Application of Electrical Raceway Fire Barrier Systems (ERFBS) to protect cables from fire damage.

3.c.

The baseline list of additional OMAs added for Unit 2 operation reflects the OMA reduction modifications described above but will be revised as described above to reflect the impact of other non-fire protection related modifications. The baseline list of OMAs is expected to require only very minor revisions due to the other non-fire protection related modifications.

TVA will provide the baseline list by August 6, 2010.

3.d.

As discussed above, TVA will finalize the Fire Protection Report to address both the fire protection related modifications and the other modifications in December, 2010. TVA will submit the complete Fire Protection Report containing a listing of the final OMAs by analysis volume for NRC approval by December 17, 2010.

U.S. Nuclear Regulatory Commission Page 6 July 16, 2010 bcc (Enclosures):

Lakshminarasimh Raghavan U.S. Nuclear Regulatory Commission MS 08H4A One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2738 Stephen Campbell U.S. Nuclear Regulatory Commission MS 08H4A One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2738 Patrick D. Milano, Senior Project Manager U.S. Nuclear Regulatory Commission MS 08H4 One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2738 Loren R. Plisco, Deputy Regional Administrator for Construction U. S. Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, Georgia 30303-1257

ENCLOSURE 1 Table Watts Bar Nuclear Plant Dual Unit Multiple Spurious Operation Scenarios PWROG Scenario Safety Function / Scenario Scenario Description Number 1 Primary Inventory Control - Loss of all Spurious isolation of RCPs seal injection reactor coolant pump (RCP) seal cooling header flow due to spurious closure of RCP seal injection header valve(s) concurrent with AND spurious isolation of component cooling water (CCW) to the thermal barrier heat Spurious isolation of CCW to the thermal exchanger barrier heat exchanger 2 Primary Inventory Control - Loss of all Spurious opening of charging injection RCP seal cooling due to charging flow valve(s) causing diversion flow away from diversion concurrent with spurious isolation seals of CCW to the thermal barrier heat exchanger AND Spurious isolation of CCW to the thermal barrier heat exchanger 3 Primary Inventory Control - Spurious re- Loss of all seal cooling to RCP(s) (see initiation of RCP seal injection/thermal Pressurizer Water Reactor Owners Group barrier cooling results in failure of the RCP [PWROG] scenarios #1 and #2) seals due to thermal shock AND Spurious re-initiation of seal injection OR spurious re-initiation of CCW to the thermal barrier heat exchanger 4 Primary Inventory Control - Catastrophic Loss of all seal cooling to RCP(s) (see RCP Seal Failure PWROG scenarios #1 and #2)

AND Fire prevents tripping the RCPs OR spurious start of an RCP(s)

E1-1

PWROG Scenario Safety Function / Scenario Scenario Description Number 5 Primary Inventory Control - Loss of all Loss of all seal cooling to RCP(s) (see RCP seal cooling concurrent with spurious PWROG scenarios #1 and #2) operation of the number 1 seal leakoff valve results in failure of RCP seal number 2 AND Spurious isolation of the number 1 seal leakoff valve 6 Primary Inventory Control - Failure to Spurious opening of (or failure to close) isolate / spurious opening of normal letdown isolation valve(s) letdown active isolation valves AND Spurious opening of (or failure to close) letdown orifice valve(s) 7 Primary Inventory Control - Normal Letdown fails to isolate (see scenario #6) letdown fails to isolate and inventory is lost to the pressurizer relief tank AND Spurious closure of downstream containment isolation valve 8 Primary Inventory Control - Excess Spurious opening of (or failure to close) letdown fails to isolate multiple in-series excess letdown isolation valves 9 Primary Inventory Control - Spurious Spurious isolation of RCP seal injection flow valve operation results in loss of all high path head reactor coolant system (RCS) makeup flow paths AND / OR Spurious isolation of normal charging flow path AND / OR Spurious isolation of charging injection flow path 10 Primary Inventory Control - Spurious Spurious isolation of suction from the isolation of Makeup Tank (MUT)/Volume MUT/VCT to running charging pump(s)

Control Tank (VCT) outlet valve(s) when the charging pump(s) is aligned to the concurrent with spurious isolation of suction VCT valves to the refueling water storage tank (RWST) results in damage to charging AND pump(s) when they are in normal operation (aligned to the MUT/VCT) Spurious isolation of (or failure to open) suction from the RWST to the running charging pump(s)

E1-2

PWROG Scenario Safety Function / Scenario Scenario Description Number 11 Primary Inventory Control - Spurious Initial condition is charging pump running isolation of two parallel RWST suction and drawing suction from the RWST.

valves results in failure of running charging pump(s) when the charging pump(s) is Spurious isolation of two parallel RWST aligned to the RWST outlet valves.

12 Primary Inventory Control - Spurious Spurious opening (or failure to close) of opening (or failure to close) of multiple multiple in-series VCT outlet valves series VCT outlet valves 13 Primary Inventory Control - Failure to Letdown fails to isolate (see PWROG isolate / spurious opening of normal scenario #66) letdown active isolation valves concurrent with spurious isolation of CCW to the AND letdown heat exchanger results in failure of charging pump(s) Spurious isolation of CCW to the letdown heat exchanger 13a Charging Pump Runout Scenario causes charging pump runout and failure. Pump(s) must be running when Note: PWROG Rev. 1 (6/5/09) Scenario RCS is at a depressurized condition.

No. 14 and 52 (partial) Unintentional RCS depressurization could occur due to spurious opening of pressurizer power-operated relief valve(s)

(PORV), for example. Charging pump(s) can spuriously start if they are not already running. Scenario may also require failure of other components (e.g., charging flow control valve, etc.).

14 Primary Inventory Control - Spurious Spurious opening of multiple in-series opening of Containment sump motor containment sump valves operated isolation valves (including residual heat removal [RHR] and CS suction valves) results in gravity draining of RWST/borated water storage tank (BWST) inventory to the Containment sump Note: PWROG Rev. 1 (6/5/09) Scenario No. 15 E1-3

PWROG Scenario Safety Function / Scenario Scenario Description Number 15 Primary Inventory Control - Spurious start Spurious starting of containment spray of containment spray pump(s) concurrent pump(s) with spurious opening of associated pump discharge valve results in transferring AND RWST/BWST inventory to the Containment sump Spurious opening of the associate pump discharge valve(s) AND/OR containment Note: PWROG Rev. 1 (6/5/09) Scenario spray header valve(s)

No. 16 15a Primary Inventory Control - Spurious start Spurious starting of RHR/SDC/LPSI of residual heat removal (RHR/shutdown pump(s) cooling (SDC)/low pressure safety injection (LPSI) pump(s) concurrent with spurious AND opening of containment spray header valve(s) results in transferring Spurious opening of the associate pump RWST/BWST inventory to the Containment discharge valve(s) sump AND/OR Note: PWROG Rev. 1 (6/5/09) Scenario No. 16 Containment spray header valve(s) 16 Primary Inventory Control - Spurious Spurious opening of multiple in-series RHR opening of shutdown cooling suction line suction valves from the RCS isolation valves (interfacing systems loss of coolant accident)

Note: PWROG Rev. 1 (6/5/09) Scenario No. 17 17 Primary Inventory Control - Spurious Spurious opening of multiple (two or three) operation of pressurizer PORV(s)/PORV pressurizer PORVs with corresponding block valve(s) given that the associated block valves in their normal, open position PORV block valve is open Note: PWROG Rev. 1 (6/5/09) Scenario No. 18 18 Primary Inventory Control - Spurious Spurious opening of pressurizer PORV(s) operation of pressurizer PORV(s) / PORV block valve(s) given that the associated AND PORV block valve is closed Spurious opening of pressurizer PORV Note: PWROG Rev. 1 (6/5/09) Scenario block valve(s) after the block valve(s) has No. 19 been closed E1-4

PWROG Scenario Safety Function / Scenario Scenario Description Number 19 Primary Inventory Control - Spurious Spurious opening of multiple reactor head operation of reactor vessel head vent vent valves valves Note: PWROG Rev. 1 (6/5/09) Scenario No.

Note: PWROG Rev. 1 (6/5/09) Scenario 20 No. 20 19a Primary Inventory Control - Spurious Spurious opening of hot leg high point vent operation of hot leg high point vent valves valves (B&W plants)

Note: PWROG Rev. 1 (6/5/09) Scenario No. 20 20 Primary Inventory Control - Spurious Spurious starting of additional high head operation of high head charging pumps charging pump(s) challenges pressurizer safety valves AND Note: PWROG Rev. 1 (6/5/09) Scenario No. 21 Spurious opening of additional RCS makeup flow paths (i.e., charging injection) 21 Primary Inventory Control - Spurious Spurious opening of RCS sample valve(s) opening of active valves in primary sample (i.e., hot leg, pressurizer liquid space, lines pressurizer steam space, etc.)

Note: PWROG Rev. 1 (6/5/09) Scenario AND No. 22 Spurious opening of inside containment isolation valve AND Spurious opening of outside containment isolation valve AND Spurious opening of downstream sample valve(s) 22 Decay Heat Removal - Spurious opening Spurious opening of atmospheric relief of atmospheric relief valve(s) upstream of valve(s) (also sometimes called atmospheric the main steam isolation valves (MSIVs) dump valves) upstream of the MSIVs Note: PWROG Rev. 1 (6/5/09) Scenario No. 23 E1-5

PWROG Scenario Safety Function / Scenario Scenario Description Number 23 Decay Heat Removal - Failure to close or MSIV(s) spuriously open OR fail to close spurious opening of MSIVs with concurrent failure of downstream steam relief valve(s) AND to close Valve(s) for downstream steam load(s)

Note: PWROG Rev. 1 (6/5/09) Scenario (e.g., condenser steam dumps, turbine inlet No. 24 valves, some atmospheric relief/dump valves, etc.) spuriously open OR fail to close 24 Decay Heat Removal - Failure to close or MSIV(s) bypass valves spuriously open OR spurious opening of MSIVs bypass valves fail to close with concurrent failure of downstream steam relief valve(s) to close AND Note: PWROG Rev. 1 (6/5/09) Scenario Valve(s) for downstream steam load(s)

No. 25 (e.g., condenser steam dumps, turbine inlet valves, some atmospheric relief/dump valves, etc.) spuriously open OR fail to close 25 Decay Heat Removal - Spurious operation Spurious operation of main steam header of main steam header drain valve(s) drain valve(s)

Note: PWROG Rev. 1 (6/5/09) Scenario No. 26 26 Decay Heat Removal - Spurious Spurious isolation of redundant steam operation/failure to operate of active steam supply valves to turbine-driven AFW pump supply valves fails the turbine-driven auxiliary (emergency) feedwater (AFW/EFW) pump Note: PWROG Rev. 1 (6/5/09) Scenario No. 27 26a Decay Heat Removal - Spurious operation/failure to isolate steam to non-credited turbine-driven AFW pump Note: PWROG Rev. 1 (6/5/09) Scenario No. 26 (partial) 27 Decay Heat Removal - Spurious closure of Spurious closure of multiple valves in AFW (AFW/EFW) pump active discharge pump discharge flow path(s) valve(s)

Note: PWROG Rev. 1 (6/5/09) Scenario No. 28 E1-6

PWROG Scenario Safety Function / Scenario Scenario Description Number 28 Decay Heat Removal - Spurious Spurious closure of steam supply valve(s) to operation/failure to operate of active steam turbine-driven AFW/EFW pump supply valves fails the turbine-driven AFW/EFW concurrent with spurious AND isolation of the AFW/EFW discharge flow path Spurious isolation of AFW/EFW pump discharge flow path(s)

Note: PWROG Rev. 1 (6/5/09) Scenario No. 29 29 Decay Heat Removal - AFW/EFW flow Combination of spurious valve operations in diversion to non-credited steam the AFW/EFW pump discharge flowpaths to generator(s) the steam generators Note: PWROG Rev. 1 (6/5/09) Scenario No. 30 30 Decay Heat Removal - AFW/EFW pump Spurious full opening of multiple EFW/AFW failure due to runout following spurious full flow control and/or isolation valves opening of multiple AFW / EFW flow control and / or isolation valves Note: PWROG Rev. 1 (6/5/09) Scenario No. 31 31 Decay Heat Removal - Spurious opening Spurious opening of valves between the of condenser hotwell makeup control valve CST and condenser hotwell results in gravity draining condensate storage tank (CST) inventory to the hotwell Note: PWROG Rev. 1 (6/5/09) Scenario No. 32 32 Decay Heat Removal - Spurious pump(s) Scenario can occur due to various operation/failure to trip pump(s) results in combinations of spurious AFW/EFW pump steam generator(s) overfill/overcooling starts, spurious opening (or failure to close) of valves in AFW/EFW pump discharge Note: PWROG Rev. 1 (6/5/09) Scenario flowpaths and spurious opening of main No. 33 feedwater (MFW) isolation valves with MFW pump(s) running.

E1-7

PWROG Scenario Safety Function / Scenario Scenario Description Number 33 Decay Heat Removal - Spurious operation Spurious opening of, or failure to close, of steam generator blowdown valves with multiple series steam generator blowdown subsequent loss of steam generator(s) valves inventory Note: PWROG Rev. 1 (6/5/09) Scenario No. 34 34 Decay Heat Removal - Spurious opening Spurious opening of steam generator of active valves in secondary sampling sample valve(s) inside containment system(s) causes loss of steam generator(s) inventory AND Note: PWROG Rev. 1 (6/5/09) Scenario Spurious opening of isolation valve(s)

No. 35 outside containment AND Spurious opening of downstream sample valve(s) 35 Primary Pressure Control - Spurious Spurious opening of normal pressurizer operation of active normal pressurizer spray valve(s) spray valves concurrent with inability to trip operating RCPs from the Control Room AND Note: PWROG Rev. 1 (6/5/09) Scenario Inability to trip/failure to trip, or spurious No. 36 operation of, RCP(s)

AND Inoperability of pressurizer heater(s) 35a Primary Pressure Control - Spurious Spurious opening of auxiliary pressurizer operation of auxiliary pressurizer spray spray valve(s) valves with charging pumps in operations AND Note: PWROG Rev. 1 (6/5/09) Scenario No. 36 Inoperability of pressurizer heater(s) 36 Primary Pressure Control - Spurious Spurious operation of multiple pressurizer operation of multiple pressurizer heater heaters banks AND Note: PWROG Rev. 1 (6/5/09) Scenario No. 37 Inoperability of pressurizer spray and auxiliary spray E1-8

PWROG Scenario Safety Function / Scenario Scenario Description Number 37 Reactivity Control - Inadvertent injection Unborated water supply to the RCS can of undiluted makeup water/inadvertent occur due to combinations of the following:

injection of makeup water with very low boron concentration - Spurious start of reactor makeup pump(s)

(supplies unborated water to the VCT),

Note: PWROG Rev. 1 (6/5/09) Scenario No. 38 - Spurious opening of valves between reactor makeup pump(s) and VCT,

- Spurious full opening of the reactor makeup flow control valve,

- Spurious closure of the boric acid flow control valve 38 Reactivity Control - Fire prevents reactor Fire damage to the reactor protection trip system (RPS) may prevent reactor trip. For example, hot shorts may prevent tripping of Note: PWROG Rev. 1 (6/5/09) Scenario the RPS motor generator sets.

No. 39 39 Support Systems - Spurious loss of CCW CCW flow can be isolated via several either as an entire system or to individual combinations of spurious valve closures.

headers (including potential water hammer events) Pertinent valves include:

-CCW pump discharge valves, Note: PWROG Rev. 1 (6/5/09) Scenario -CCW pump crosstie valves, No. 40 -CCW heat exchanger inlet valves,

-CCW heat exchanger outlet valves,

-CCW heat exchanger crosstie valves,

-etc.

40 Support Systems - Spurious loss of CCW Spurious isolation of CCW cooling to to individual critical loads (including individual redundant loads including lube oil potential water hammer events) coolers, RHR heat exchangers, etc.

Note: PWROG Rev. 1 (6/5/09) Scenario No. 41 E1-9

PWROG Scenario Safety Function / Scenario Scenario Description Number 41 Support Systems - CCW flow diversion to Flow diversion can occur via several non-credited loop(s) combinations of spurious valve operations in the CCW pump discharge and CCW loop Note: PWROG Rev. 1 (6/5/09) Scenario crosstie flowpaths. Review piping and No. 42 instrumentation diagrams (P&IDs) to identify relevant combinations.

42 Support Systems - Spurious loss of Safety-related SW (sometimes called safety-related service water (SW) either as "essential" SW) flow to credited loads can an entire system or to individual headers be isolated via several combinations of (including potential water hammer events) spurious valve closures.

Note: PWROG Rev. 1 (6/5/09) Scenario Pertinent valves include:

No. 43 -SW pump discharge valves,

-SW pump crosstie valves,

-SW heat exchanger inlet valves,

-SW heat exchanger outlet valves,

-SW heat exchanger crosstie valves,

-etc.

Review P&IDs to identify relevant combinations.

43 Support Systems - Spurious loss of Spurious isolation of safety-related SW safety-related SW to individual critical loads cooling to redundant loads including CCW (including potential water hammer events) heat exchangers and emergency diesel generator (EDG) cooling Note: PWROG Rev. 1 (6/5/09) Scenario No. 44 44 Support Systems - Safety-related SW flow Flow diversion can occur via several diversion to non-credited loops/loads combinations of spurious valve operations in the SW pump discharge and loop crosstie Note: PWROG Rev. 1 (6/5/09) Scenario flowpaths. Review P&IDs to identify No. 45 relevant combinations.

45 Support Systems - Non-critical Additional components load onto credited components inadvertently loaded onto diesel generator credited EDGs Note: PWROG Rev. 1 (6/5/09) Scenario No. 46 E1-10

PWROG Scenario Safety Function / Scenario Scenario Description Number 46 Support Systems - EDGs overloading EDG overloading Note: PWROG Rev. 1 (6/5/09) Scenario No. 47 47 Support Systems - Spurious start of an Fire spuriously starts an EDG(s)

EDG(s) with concurrent failure to provide required cooling AND Note: PWROG Rev. 1 (6/5/09) Scenario Motor-operated valves (MOVs) providing No. 48 required cooling water to the EDG(s) either fail to open or spuriously close 48 Support Systems - Non-synchronous Non-synchronous paralleling of EDGs with paralleling of EDGs with on-site and off-site on-site and off-site sources through sources through spurious circuit breaker spurious circuit breaker operations operations Note: PWROG Rev. 1 (6/5/09) Scenario No. 49 49 Other Scenarios - Spurious isolation of Note: Spurious operation of powered (i.e.,

various combinations of pump(s) suction MOVs, air-operated valves [AOVs],

valve(s) solenoid-operated valves [SOVs]) pump(s) suction valve(s) is most likely already Note: PWROG Rev. 1 (6/5/09) Scenario included in the probabilistic risk assessment No. 50 (PRA) logic and the safe shutdown cable analysis.

50 Other Scenarios - Spurious isolation of Note: Spurious operation of powered (i.e.,

various combinations of pump(s) discharge MOVs, AOVs, SOVs) pump(s) discharge valve(s) valve(s) are most likely already included in the PRA logic and the safe shutdown cable Note: PWROG Rev. 1 (6/5/09) Scenario analysis.

No. 51 51 Other Scenarios - Pump failure due to -

spurious closure of discharge valve(s) concurrent with failure to open or spurious closure of required minimum recirculation flow path(s)

Note: PWROG Rev. 1 (6/5/09) Scenario No. 51 E1-11

PWROG Scenario Safety Function / Scenario Scenario Description Number 51a Other Scenarios - Spurious start of high High head charging pump(s) spuriously head charging pump(s) concurrent with starts closing of required minimum flow path valve(s) results in failure of the pump(s) AND Recirculation flow path valve(s) fails to open OR transfers closed 51b Other Scenarios - Spurious start of high High pressure safety injection pump(s) pressure safety injection pump(s) spuriously starts concurrent with closing of required minimum flow path valve(s) results in failure AND of the pump(s)

Recirculation flow path valve(s) fails to open OR transfers closed 51c Other Scenarios - Spurious operation of RHR/SDC/low pressure safety injection RHR shutdown cooling (SDC)/low pressure pump(s) spuriously starts safety injection pump(s) concurrent with failure of associated minimum flow path AND valve(s) to open results in failure of the pump(s) Recirculation flow path valve(s) fails to open OR transfers closed 52 Other Scenarios - Loss of credited Spurious isolation of HVAC to credited loads heating, ventilation and air conditioning (HVAC) to component(s)

Note: PWROG Rev. 1 (6/5/09) Scenario No. 54 53 Other Scenarios - Spurious MOV Spurious MOV operation operation concurrent with fire-induced failure of torque and/or limit switches AND Note: PWROG Rev. 1 (6/5/09) Scenario Wire-to-wire short(s) bypass torque and limit No. 55 switches 54 Other Scenarios - Spurious engineered Fire induced spurious ESFAS signal safeguards actuation signal (ESFAS)

Note: PWROG Rev. 1 (6/5/09) Scenario No. 56 E1-12

PWROG Scenario Safety Function / Scenario Scenario Description Number 54a Other Scenarios - Spurious start of Spurious safety injection signal makeup/injection pump(s) due to a spurious safety injection signal with concurrent AND spurious isolation of pump suction valve(s)

Spurious isolation of makeup pump suction Note: PWROG Rev. 1 (6/5/09) Scenario No. 56a 54b Other Scenarios - Spurious isolation of Spurious containment isolation signal RCP(s) thermal barrier cooling due to a isolates CCW to the thermal barrier heat spurious containment isolation signal with a exchangers for all RCPs concurrent isolation of seal injection AND Note: PWROG Rev. 1 (6/5/09) Scenario No. 56c (similar) Spurious isolation of seal injection header flow 54c Other Scenarios - Spurious isolation of Spurious containment isolation signal RCP(s) thermal barrier cooling due to a isolates CCW to the thermal barrier heat spurious containment isolation signal with a exchangers for all RCPs concurrent isolation of charging AND Note: PWROG Rev. 1 (6/5/09) Scenario No. 56c Spurious opening of charging injection valve(s) causing insufficient flow to seals 54d Other Scenarios - Spurious start of Spurious high containment pressure on containment spray pump(s) due to a multiple channels causing spurious spurious containment spray signal containment spray signal Note: PWROG Rev. 1 (6/5/09) Scenario No. 56d 54e Other Scenarios - Spurious opening of Spurious high pressurizer pressure on PORV(s) due to spurious high pressurizer multiple channels causes high pressurizer pressure signals on multiple channels pressure signal Note: PWROG Rev. 1 (6/5/09) Scenario No. 56e 54f Other Scenarios - Spurious Recirculation Spurious RAS starting and aligning pumps Actuation Signal (RAS) starting and to a dry containment sump.

aligning pumps to a dry containment sump.

Added on 6/5/09 NEI 00-01 Rev 2 list (Item 56f)

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ENCLOSURE 2 List of Commitments

1. TVA is in the process of finalizing the Fire Protection Report to address both the fire protection related modifications and the other modifications. This review will be completed in December, 2010. TVA will submit the complete Unit 1/2 Fire Protection Report by December 17, 2010.

2. TVA will provide a separate markup, description, and justification of the changes made since NRC approved the report. This information will be provided by August 30, 2010.

3. Portions of the report address programmatic aspects (e.g., fire brigades, fire watches, etc.)

that are not affected by the operation of Unit 2. These parts will be submitted to the NRC by August 6, 2010.

4. Table 1 provides a description of the dual unit MSO scenarios identified by the above described analysis. TVA will provide a description of how safe shutdown is ensured for each scenario by August 20, 2010.

5. The baseline list of OMAs is expected to require only very minor revisions due to the other non-fire protection related modifications. TVA will provide the baseline list by August 6, 2010.

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