ML100680520

Nine-Month Supplemental (Post-Outage) Response to NRC Generic Letter 2008-01

ML100680520
Person / Time
Site:	Palo Verde
Issue date:	03/02/2010
From:	Hesser J Arizona Public Service Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
102-06141-JHH/DAF, GL-08-001
Download: ML100680520 (21)

Text

10 CFR 50.54(f)

A subsidiary of Pinnacle West Capital Corporation John H. Hesser Mail Station 7605 Palo Verde Nuclear Vice President Nuclear Tel. 623-393-5553 P. 0. Box 52034 Generating Station Engineering Fax 623-393-6077 Phoenix, Arizona 85072-2034 102-06141-JHH/DAF March 2, 2010 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

References:

1. Arizona Public Service Company (APS) Letter No. 102-05910, dated October 14, 2008, Nine-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" (ADAMS Accession No. ML08294032)

2. NRC Letter dated July 25, 2008, Proposed Alternative Course of Action, Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" (ADAMS Accession No. ML081960078)

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Unit 2 Docket No. STN 50-529 Unit 2 Nine-Month Supplemental (Post-Outage) Response to NRC Generic Letter 2008-01 As requested in Reference 2, enclosed is the APS supplemental response to the nine-month response letter (Reference 1). This supplemental response is being submitted within 90 days of startup from the Unit 2 outage in which the deferred system walkdowns were completed. The Generic Letter (GL) activities that remain to be accomplished in Unit 2 as well as a. summary of all other unit findings are described in the enclosure.

In summary, APS has concluded that the subject systems in Unit 2 are operable and that Unit 2 is currently in compliance with the licensing basis documentation and applicable regulations, including 10 CFR 50, Appendix B, Criteria Ill, V, XI, XVI, and XVII, with respect to the concerns outlined in GL 2008-01 regarding managing gas accumulation in these. systems.

A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

• Comanche Peak - Diablo Canyon

• Palo Verde ° San Onofre

• South Texas - Wolf Creek

ATTN: Document Control Desk

Subject:

U. S. Nuclear Regulatory Commission Unit 2 Nine-Month Supplemental (Post-Outage) Response to NRC Generic Letter 2008-01 Page 2 There are three new commitments and one commitment extension made by APS in this letter as shown in the updated commitment table included in Section D of the enclosure.

Should you need further information regarding this submittal, please contact Russell A.

Stroud, Licensing Section Leader, at (623) 393-5111.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on.5/21o2O Sincerely, DCM/DAF/gat

Enclosure:

Unit 2 Nine-Month Supplemental (Post-Outage) Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings cc:

E. E. Collins Jr.

NRC Region IV Regional Administrator J. R. Hall NRC NRR Project Manager R. I. Treadway NRC Senior Resident Inspector for PVNGS

Enclosure Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings Nine-Month Supplemental (Post-Outage) Response to NRC Generic Letter 2008-01 As requested by the NRC, the following provides APS's nine-month supplemental (post-outage) response to GL 2008-01 for actions that were deferred until the next refueling outage for Unit 2.

The following information is provided in this enclosure:

A description of additional corrective actions determined to be necessary to assure system operability and compliance with the quality assurance criteria in Sections III, V, XI, XVI, and XVII of Appendix B to 10 CFR Part 50, the licensing basis, and the operating license with respect to the subject systems. For any additional corrective actions the information includes a schedule and a basis for that schedule (see Section B.1 of this enclosure).

" A summary description of changes or updates to previous corrective actions, including any schedule change and the basis for the change. (See Section D of this enclosure).

The original conclusions documented in the 9-month response with respect to the licensing basis evaluation, testing evaluations, and corrective action evaluations remain valid and have not changed.

A. EVALUATION RESULTS

1. Design Basis Documents Completion and evaluation of the Unit 2 design validation walkdowns performed prior to and during the Spring 2009 refueling outage in 2R15 did not result in any required changes to design basis documents.

2. Confirmatory Walkdowns Prior to and during refueling outage 2R1 5, APS completed laser templating of horizontal sections of Safety Injection (SI) system piping inside and outside of the Unit 2 containment. An evaluation of the results was performed by Arizona Public Service Company (APS) engineers. Pipe slopes and local high points that deviate from the nominal horizontal or prescribed slope greater than approximately one-quarter inch (1/4") on suction piping, one-half inch (1/2") on the high pressure safety injection (HPSI) discharge and three-quarter inch (3/4") on low pressure safety injection (LPSI) and containment spray (CS) discharge piping were identified.

APS Engineering identified 16 examination points meeting the criteria described above. For these locations, confirmatory ultrasonic testing (UT) examinations will be 1

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings performed. Based on the similarities and results of the UT examinations in Units 1 and 3, all locations are expected to be confirmed to be full of water. (COM-23)

UT will not be performed at locations downstream of the normally closed containment isolation valves. As described in Section 2.2.c of the APS 9-month response to GL 2008-01 (Reference 1 of this enclosure), these valves are not subject to conditions that would result in waterhammer because of the slow-opening containment isolation valves and lack of downstream flow restrictions (Reference 2 of this Enclosure).

3. Vent Valves The evaluation of the laser templating in Unit 2 revealed two locations which require further evaluation. These locations are on the Emergency Core Cooling System (ECCS) suction lines from the Refueling Water Tank (RWT), one location on each train. In these locations, the slope is between one and one-half inches (11/2") and two and one-half inches (21/2") over extended lengths of pipe. If gas accumulation were to form at these locations it could not be removed by venting through existing vent valves and would require a dynamic vent or flush to remove. There are physical impediments in these two locations that may make installing vent valves unfeasible in which case programmatic controls will be developed to ensure that these two locations remain filled with water. (COM-24) (COM-25)

4. Procedures No procedure changes were determined to be necessary as a result of the laser templating performed in Unit 2 B. DESCRIPTION OF NECESSARY ADDITIONAL CORRECTIVE ACTIONS

1. Additional Corrective Actions The following additional corrective action will be performed:

APS will complete the evaluation of the two Unit 2 ECCS suction lines by September 30, 2010. If the evaluation demonstrates that the installation of vent valves is feasible and warranted, the installations will be completed no later than the completion of Unit 2's 1 7 th refueling outage, estimated to be November 30, 2012. If vent valve installation is not feasible or is not warranted, programmatic controls will be implemented by completion of the 2R17 refueling outage to ensure these locations remain filled with water. This timeframe allows for determination of feasibility and necessity of vent valve installation, and evaluation of the programmatic control option. These locations are not subject to any of the gas accumulation mechanisms identified during the original evaluations performed in response to the GL with the exception of an incomplete fill and vent. If drained, these locations will be verified full. This provides assurance that the SI piping 2

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings systems are sufficiently full to perform their intended safety functions pending completion of these actions. (COM-24) (COM-25)

C.

SUMMARY

OF DESIGN VALIDATION WALKDOWN FINDINGS Several locations were identified in each Unit during the design validation walkdowns where, if gas were to accumulate, it could not be removed directly by venting and/or easily removed by dynamic venting or flushing. These locations were the result of as-built pipe slopes and required further evaluation for installation of vent valves. Three locations were identified in Unit 1 and vent valves are scheduled to be installed in each location during the upcoming Spring 2010 Unit 1 refueling outage. (COM-20) Three locations in Unit 3 and the two locations discussed above in Unit 2 are being evaluated for feasibility. If vent valve installations are determined to not be feasible or warranted, appropriate programmatic controls to ensure these locations remain filled with water will be implemented. The Unit 3 evaluation, initially schedule for completion by March 31, 2010, will require additional time for completion. Therefore, both the Unit 2 and 3 evaluations are expected to be completed by September 30, 2010. (COM-21) (COM-24)

Vent valve installations or the implementation of programmatic controls for Units 2 and 3 are scheduled for May 30, 2012 and November 30, 2012, respectively. (COM-

22) (COM-25) 3

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings D. Corrective Action Updates The following table provides updates to the list of commitments provided in Reference 3 of this enclosure.

No.

Commitments:

Due APS commits to perform physical design verification walkdowns of the ECCS, shutdown cooling COM-1 system (SCS) and containment spray system (CSS) to validate the as-built conditions for Unit 1 Complete for GL 2008-01 prior to startup from the Unit 1 R14 refueling outage expected by 11/30/08 COM-2 APS commits to perform physical design verification walkdowns of the ECCS, SCS and CSS to validate the as-built conditions for Unit 3 for GL 2008-01 prior to startup from the Unit 3 R14 Complete refueling outage expected by 05/31/09.

COM-3 APS commits to perform physical design verification walkdowns of the ECCS, SCS and CSS to validate the as-built conditions for Unit 2 for GL 2008-01 prior to startup from the Unit 2 R1 5 Complete refueling outage expected by 11/30/09.

COM-4 APS commits to submit to the NRC any required additional corrective actions resulting from performing the design validation walkdowns for Unit 1, 90 days after completion of the Unit 1 Complete R14 refueling outage. (Est. 2/28/09)

COM-5 APS commits to submit to the NRC any required additional corrective actions resulting from performing the design validation walkdowns for Unit 3, 90 days after completion of the Unit 3 Complete R14 refueling outage. (Est. 8/29/09)

COM-6 APS commits to submit to the NRC a final evaluation summarizing the findings and corrective Complete actions resulting from the design validation walkdowns performed in all three PVNGS Units, 90 with this days after completion of the Unit 2 R1 5 refueling outage. (Est. 2/28/10) submittal 4

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings The following table provides updates to the list of commitments last provided in Reference 4 of this enclosure and additional commitments from this Unit 3 Nine-Month Supplemental Response.

ý'No.

Commitments, Corrective Actions to be completed including the scope and basis for the Due

___!;:*~~ý schedule APS is continuing to support the industry and NEI Gas Accumulation Management Team One year activities regarding the resolution of generic TS changes via the TSTF traveler process. APS following will evaluate the resolution of TS issues with respect to the changes contained in the TSTF NRC COM-1 traveler, and submit a LAR based on this evaluation within one year following NRC approval of approval of the CLIIP Notice of Availability of the TSTF traveler. The basis changes associated with the TS the CLIIP changes will also be made.

Notice of 1

1 Availability 5

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings

..`ýNo.

Commitments - CorrectiveActions to be completed including the scope and basis for the.

Due schedule Design change SI-1 057 and associated design basis document changes will be developed to support a proposed TS amendment to preclude the possibility of air entrainment from the RWT into SI system suction piping during the transfer to recirculation. This change includes raising the RAS set point and associated design calculations and requires NRC approval of a LAR.

The LAR will include a revision to the UFSAR describing the required closure of the RWT outlet valves by control room operators within a prescribed condition. Associated Licensing Bases changes include a revision to reflect that proper initiation, of recirculation is required to preclude excessive air entrainment from either the RWT or the containment sump and to the UFSAR to describe the additional design requirements necessary to preclude the possibility of drawing air COM-2 from the RWT to the safeguard pump suction during recirculation. The LAR will be submitted by Complete 11/30/2009.

The time frame for completion of this corrective action is justified due to the time required to develop the design modification and corresponding LAR. The condition associated with this corrective action has been evaluated for Operability in accordance with RIS 2005-20. Detailed dynamic hydraulic evaluations have been performed which demonstrate that during the transfer to recirculation, sufficient air is not transported to either the CS or HPSI pumps to degrade their performance. This evaluation provides the technical justification for the acceptability of operation until the corrective actions are completed.

6

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings SNo:,

.Commitments*-

Corrective'Actions to be cbmpleted including the scope and basis for the Due Ischedule-The basis for TSR 3.5.202.4 and TRM Sections T3.6 and T3.5.201 will be revised to require the entire SI system suction piping to be verified full of water. This Corrective Action will be completed by January 15, 2009.

This timeframe allows for the development of suction side acceptance criteria and the revision of COM-3 surveillance test procedures. Operating procedures already contain requirements to vent the Complete shutdown cooling suction piping and provide assurance these piping sections are full upon completion of this action. This Licensing Basis change will not require any additional suction piping needing to be verified full for ECCS or CS, since current surveillance test procedures already contain provisions for verifying the suction piping is full for these two systems.

UFSAR Table 3.9-10 will be revised to reflect the appropriate combination of the water hammer loads associated with gas accumulation in SI piping and seismic loads for design of piping and COM-4 pipe supports. The corrective action will be completed March 31, 2009.

Complete This timeframe allows for completion of UFSAR change documentation.

Complete the PVNGS-specific evaluations to develop gas volume acceptance criteria for SI suction piping. This corrective action will be completed by October 30, 2008.

COM-5 Current acceptance criteria and surveillance test procedures are adequate to ensure the SI Complete piping systems are sufficiently full to reliably perform the intended safety functions pending completion of these evaluations.

7

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings No.

-Commitments --Corrective Actions to be completed including the scope and basis for the Due schedule Complete PVNGS-specific evaluations to develop gas volume acceptance criteria for each segment of SI discharge piping upstream of the normally closed containment isolation valves.

This Corrective Action is scheduled to be completed by March 31, 2009.

This timeframe allows for completion of detailed water hammer calculations of potential gas COM-6 accumulations at all discharge piping high point locations, including resolution of the UFSAR Complete Table 3.9-10 Loading Combinations, and subsequent revision to surveillance test procedures.

Current surveillance test procedures that require opening of all pump discharge vent valves at the specified 31-day interval are adequate to ensure unacceptable gas accumulation does not occur pending completion of this corrective action.

8

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings No.

Commitments -.Correctiveb-Actions to be.completed including the scope and basis for the Due schedule Complete PVNGS specific evaluations to develop gas volume acceptance criteria for each segment of SI discharge piping downstream of the normally closed isolation valves. The downstream piping includes the CS piping downstream of the isolation valve that is normally closed during power operation and opens on receipt of a Containment Spray Actuation Signal (CSAS), the hot leg injection piping downstream of the isolation valve that is normally closed during power operation and opened following switchover to this injection location, and cold leg injection piping downstream of the isolation valves that are normally closed and open upon receipt of a SIAS or CSAS. This Corrective Action is scheduled to be completed by March 31, 2009. Acceptance criteria for the hot leg injection piping may have an associated change to applicable Emergency Operating procedures to specify a different valve alignment sequence than currently prescribed.

COM-7 The completion date for development of acceptance criteria for the hot leg injection piping only Complete is revised to June 30, 2009.This timeframe allows for completion of evaluation of options regarding changes to valve alignment sequence and completion of waterhammer calculations for this specific piping. Development of all other acceptance criteria will be completed by the original March 31, 2009 scheduled completion date.

Current practices to fill and vent the piping inside containment, the low consequences associated with gas accumulation in piping inside containment, and the lack of current indication of on-going gas accumulation mechanisms such as SIT leakage past the containment isolation valves make the schedule for this action acceptable.

9

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings No.-

Commitments.- Corrective Actions, to be completed including the scope and basis for the

'Due

ýschedlule Design modification SI-1057 will be implemented in each Unit's refueling outage that starts no During sooner than one year following NRC approval of the associated LAR.

scheduled refueling The time frame for completion of this corrective action is justified due to the time required to outages develop the design modification. The condition associated with this corrective action has been beginning evaluated for Operability in accordance with RIS 2005-20.

with the first unit at CM-8 Detailed dynamic hydraulic evaluations have been performed which demonstrate that during the least one transfer to recirculation, sufficient air is not transported to either the CS or HPSI pumps to year after degrade their performance. This evaluation provides the technical justification for the NRC acceptability of operation until the corrective actions are completed.

approval of the associated LAR Develop a procedure or written instruction that will specify requirements for performance of confirmatory ultrasonic measurements that monitor or confirm the adequacy of system fill and vent. This corrective action is scheduled to be completed by March 31, 2009.

Scheduled completion is revised to August 31, 2009. This schedule revision allows for COM-9' evaluation of laser templating results and lessons learned from the upcoming 3R14 refueling Complete outage (Spring 2009)

This is currently a routine Engineering activity performed every refueling outage that is adequate pending incorporation into a procedure.

10

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings No.

C**ommitments.

Corrective Actions to be completed including the scope and basis for the Due Schedule Develop a procedure or process that controls the performance of system and pump performance tests or other high velocity flushes to ensure these routine activities are performed as necessary to preclude gas accumulation potentially resulting from an incomplete initial system fill. This corrective action is scheduled to be completed by August 1, 2009.

COM-10 Complete These pump and system performance tests are performed every refueling outage and current outage scheduling is adequate pending completion of this action.

Applicable surveillance test procedures will be revised to include periodic ultrasonic inspection of the piping to identify and if necessary quantify the size of the voids in the piping. Acceptance criteria for each high point location will be specified. The procedures will require entry into the CAP when the acceptance criteria are exceeded. The need for sampling and analysis of gas will be determined through the CAP when abnormal conditions are detected. This corrective action will be phased in as acceptance criteria for each sub-system is developed. Full implementation of this corrective action is scheduled to be completed by April 30, 2009.

COM-1 1 The schedule for full implementation of this action is revised to June 30, 2009. This timeframe Complete allows for completion of acceptance criteria evaluations and revisions and subsequent revision to surveillance test procedures.

Current surveillance tests and the current acceptance criteria of a clear stream of water from accessible high point vent valves are adequate to ensure unacceptable gas accumulation does not occur pending completion of this corrective action.

11

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings

_No.

Commitments-Corrective Actions to be completed including the scope and basis for the :.,,Due schedule Surveillance test procedures will be revised to redefine accessibility of piping inside containment based on actual expected radiation exposure and scaffolding requirements. This corrective action is scheduled to be completed by March 31, 2009.

All piping inside containment except for that located within the bio-shield wall is considered to be accessible for the purpose of the surveillance tests. The revised timeframe allows for the extensive surveillance test procedure revisions necessitated by this redefinition.

Evaluations of the consequences of gas accumulation in discharge side piping inside containment have been completed by a PWROG program and by Westinghouse for certain CE-COM-12 designed plants, which demonstrate that voids in this piping will typically not cause a water Commitment hammer effect because of the slow-opening containment isolation valves and lack of cancelled.

downstream flow restrictions. In addition, delays in injecting flow to the RCS due to voids in the discharge piping have been determined in the PWROG program to be inconsequential. The only gas accumulation mechanism identified following successful initial fill and vent following maintenance is leakage from either the SI Tanks or the RCS into the low pressure upstream SI piping. This mechanism can be monitored with installed plant instrumentation and verified by surveillance of upstream piping. Considering the reduced consequences associated with gas accumulation in piping inside containment, and the ability to detect and verify the conditions necessary to promote gas accumulation in these piping sections, current practices are considered adequate pending completion of this action.

12

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings No-Commitments -Corrective Actions to be completed including the-scope and basis for the Due schedule Procedure 40DP-90P06 will be revised to provide guidance on the amount of SIT level change that should be considered abnormal and require entry into the CAP to assess the cause of the leak and the potential for void formation when the threshold is exceeded. This corrective action is scheduled to be completed by January 15, 2009.

COM-13 ~This time frame allows for determination of the appropriate threshold and specification of the Complete appropriate response. The current procedure and practices at PVNGS have been adequate to ensure unacceptable gas accumulation does not occur pending completion of this corrective action.

Revise surveillance test procedure 40ST-9SI 13 to include verification that the SDC suction piping is sufficiently full of water. This corrective action is scheduled to be completed by January 15, 2009.

COM-14 This time frame allows for completion of acceptance criteria and subsequent procedure revision.

Complete Current procedures for restoring from SDC operations to standby SI alignment have been adequate to prevent unacceptable gas accumulation or formation. Operating procedures already contain requirements to vent the SDC suction piping and provide assurance these piping sections are full pending completion of this action.

A formalized trending process (or procedure) will be developed to document the results of the monthly surveillance tests and ensure Operability to the next surveillance test. This action is scheduled to be completed by April 15, 2009.

The schedule to complete this action is revised to complete by July 31, 2009. The revised Complete timeframe allows for completion of all related surveillance test procedures (see revised scheduled completion date for COM-1 2).

This action proceduralizes trending activities recommended by the GL and industry practices, but does not have a direct impact on Operability.

13

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings Revise the PVNGS-specific evaluation of allowable gas volume acceptance criteria for SI suction piping to determine criteria specific to the Unit 1 A train to account for the actual measured pipe slope of the common suction header. This action is scheduled to be completed COM-1 6 by June 30, 2009.

Complete The timeframe allows for completion of the evaluation revision. The common suction header has been shown to be full of water by UT such that reliable performance of the intended safety function remains assured pending completion of these actions.

Revise the applicable surveillance test procedure to account for reduced allowable gas accumulation acceptance criteria specific to the Unit 1 A train suction piping. The surveillance test procedures will be revised to add verification that the pipe is full at the two locations which may have an inherent vulnerability to air/gas accumulation due to the identified pipe slope on the A train common suction header and the B train shutdown cooling line. This action is COM-1 7 scheduled to be completed by September 30, 2009.

Complete The timeframe allows for completion of the evaluation revision and revision to the test procedures. The common suction header has been shown to be full of water by UT such that reliable performance of the intended safety function remains assured pending completion of these actions.

Complete UT examination of all remaining Priority 2, 3, and 4 locations identified by laser templating as deviating by more than one quarter inch (1/4") from horizontal. This action will be completed by April 30, 2009.

This timeframe allows for completion of the activity including scheduling of insulation removal COM-18 within the Palo Verde work management system and associated risk evaluations. The location Complete and potential gas accumulation volumes are such that there is minimal risk that an actual gas accumulation that would challenge system operability exists at these locations. The current acceptance criteria, surveillance test procedures and operating procedures are adequate to ensure the SI piping systems are sufficiently full to reliably perform the intended safety functions I pending completion of the confirmatory UTs.

14

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings Complete evaluation of installing or relocating vent valves at two locations in Unit 1 identified by laser templating as being vulnerable to gas accumulation that cannot currently be easily vented or flushed. This action will be completed by June 30, 2009.

COM-1 9 Complete This timeframe allows for determination of feasibility and necessity of vent valve installation, and evaluation of programmatic control options. These locations have been confirmed by UT to be full of water and appear not to be subject to any of the gas accumulation mechanisms identified during the original evaluations performed in response to the Generic Letter.

If evaluation concludes that the installation of a vent valve is feasible and warranted, the vent valve installation will be completed no later than the completion of the next refueling outage (1 R15 scheduled for the Spring of 2010). If vent valve installation is not feasible or is not warranted, an appropriate programmatic control to ensure these locations remain filled with water will be implemented by completion of the next refueling outage. This commitment applies COM-20 to both locations identified in COM-19.

5/30/2010 This timeframe allows for determination of feasibility and necessity of vent valve installation, and evaluation of programmatic control options. These locations have been confirmed by UT to be full of water and not subject to any of the gas accumulation mechanisms identified during the original evaluations performed in response to the Generic Letter.

Complete evaluation of installing vent valves at three locations in Unit 3 identified by laser templating as being vulnerable to. gas accumulation that cannot be easily vented or flushed.

This action will be completed by March 31, 2010. September 30, 2010.

This timeframe allows for determination of feasibility and necessity of vent valve installation, and

-/-1/2010 COM-21 evaluation of programmatic control options. These locations have been confirmed by UT to be 9/30/2010 full of water and not subject to any of the gas accumulation mechanisms identified during the original evaluations performed in response to the GL with the exception of an incomplete fill and vent. These locations will be verified to be full if drained and re-filled prior to completion of this corrective action. This provides assurance that the Sl piping systems are sufficiently full to perform their intended safety functions pending completion of these actions.

15

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings If the evaluation concludes that the installation of a vent valve is feasible and warranted, the vent valve installation will be completed no later than the completion of the 3R1 6 refueling outage scheduled for Spring 2012. If vent valve installation is not feasible or is not warranted, an appropriate programmatic control to ensure these locations remain filled with water will be implemented by completion of the 3R16 refueling outage.

COM-225/021 This timeframe allows for determination of feasibility and necessity of vent valve installation, and 5/30/2012 evaluation of programmatic control options. These locations have been confirmed by UT to be full of water and not subject to any of the gas accumulation mechanisms identified during the original evaluations performed in response to the GL with the exception of an incomplete fill and vent. These locations will be verified to be full if drained and re-filled prior to completion of this corrective action. This provides assurance that the SI piping systems are sufficiently full to perform their intended safety functions pendinq completion of these actions.

APS Engineering identified 16 Unit 2 examination points meeting the criteria described. For these locations, confirmatory UT examinations will be performed. Based on the similarities and COM-23 results of the UT examinations in Units 1 and 3, all locations are expected to be confirmed to be 6/30/2010 full of water.

16

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings Complete evaluation of installing or relocating vent valves at two locations in Unit 2 identified by laser templating as being vulnerable to gas accumulation that cannot be easily vented for flushed. This action will be completed by September 30, 2010.

This timeframe allows for determination of feasibility and necessity of vent valve installation, and evaluation of programmatic control options. These locations are not subiect to any of the gas accumulation mechanisms identified during the original evaluations performed in response to COM-24 the GL with the exception of an incomplete fill and vent. These locations will be verified to be 9/30/2010 full if drained and re-filled prior to completion of this corrective action. This provides assurance that the SI piping systems are sufficiently full to perform their intended safety functions pending completion of these actions.

If the evaluation demonstrates that the installation of vent valves is feasible and warranted, the installations will be completed no later than the completion of Unit 2's 17th refueling outage, estimated to be November 30, 2012. If vent valve installation is not feasible or is not warranted, programmatic controls will be implemented by completion of the 2R17 refueling outage to ensure these locations remain filled with water.

COM-25 1 1/30/2012 This timeframeallows for determination of feasibility and necessity of vent valve installation, and evaluation of programmatic control options. These locations are not subiect to any of the gas accumulation mechanisms identified during the original evaluations performed in response to the GL with the exception of an incomplete fill and vent. These locations will be verified to be full if drained and re-filled prior to completion of this corrective action. This provides assurance that the SI piping systems are sufficiently full to perform their intended safety functions pending comnletion of these actions.

I Ný 17

Unit 2 Nine-Month Supplemental (Post-Outage)

Response to NRC Generic Letter 2008-01 and Summary of Design Validation Walkdown Findings Conclusion APS has concluded that the subject systems at the PVNGS Unit 2 remain in compliance with the Technical Specification definition of operability, i.e., they are capable of performing their intended safety functions.

References

1. APS Letter No. 102-05910, dated October 14, 2008, Nine-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems." (ADAMS Accession No. ML08294032)

2. Westinghouse/Fauske & Associates Calculation Note Number FAI/08-189, Rev.

0 "Evaluation of the Potential for Gas-Water Waterhammer During Cold Leg Injection for Palo Verde."

3. APS Letter No. 102-05857, dated May 09, 2008, Three-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems." (ADAMS Accession No. ML08120363)

4. APS Letter No. 102-06052, dated August 26, 2009, Unit 3 Nine-Month Supplemental (Post-Outage) Response to NRC Generic Letter 2008-01, and Update on Unit 1 Open Issues. (ADAMS Accession No. ML092580379) 18