NOC-AE-10002511, Month Supplemental Response to Generic Letter 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal and Containment Spray Systems.

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Month Supplemental Response to Generic Letter 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal and Containment Spray Systems.
ML100501160
Person / Time
Site: South Texas  STP Nuclear Operating Company icon.png
Issue date: 02/16/2010
From: Gerry Powell
South Texas
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
GL-08-001, NOC-AE-10002511, TAC MD7881, TAC MD7882
Download: ML100501160 (10)
v • d • e


Text

Nuclear Operating Company South Texas Project Electric Generabn$ Station PO Box 289 Wadsworth Texas 77483 A/vA/*

February 16, 2010 NOC-AE-10002511 10 CFR 50.54(f)

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk 11555 Rockville Pike Rockville, MD 20852 South Texas Project Units 1 and 2 Docket No. STN 50-498, STN 50-499 9-Month Supplemental Response to Generic Letter 2008-01 (TAC Nos. MD7881 and MD7882)

Reference:

1. NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems," dated January 11,2008
2. Letter from Mohan C.7Thadani to Edward D. Halpin dated September 22, 2008, "South Texas Project, Units 1 and 2 - Generic Letter 2008-01, "Managing Gas Accumulation in Emergency.Core Cooling, Decay Heat Removal, and Containment Spray Systems," Proposed Alternative Course of Action and Request for Additional Information (TAC Nos. MD7881 and MD7882).
3. Letter from G. T. Powell to NRC Document Control Desk dated October 13,:

2008, "Nine-Month Response to Generic Letter 2008-01". (NOC-AE-08002355)

(ML082960430)

4. Email from Mohan C. Thadani to Albon W. Harrison dated October 13, 2009,,

Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core.

Cooling, Decay Heat Removal, and Containment Spray Systems,"

(ML092860079)

The Nuclear Regulatory Commission (NRC) issued GenericLetter (GL) 2008-01 (Reference 1) to request that each licensee evaluate the emergency core cooling, (ECCS), decay heat removal (DHR), and containment spray systems to ensure that gas accumulation is maintained less than the amount that challenges operability of these systems, and that appropriate action is taken when conditions adverse to quality are identified.

As requested in Reference 2 and committed to in Reference 3, please find attached the South Texas Project (STP) supplemental response to the 9-month response letter (Reference 3).

In summary, STP Nuclear Operating Company (STPNOC) has concluded that based on the previous reviews of the current plant configuration, plant specific operating experience, and procedure reviews the subject systems/functions are in compliance with the current licensing and design bases and applicable regulatory requirements. System piping walkdowns and slope

.determinations performed to date have not yielded any information to alter this conclusion. All identified systems are capable of performing their design function.

STI: 32603566 A member of the STARS (Strategic.Teaming and Resource Sharing) Alliance IyI Callaway - Comanche Peak - Diablo Canyon - Palo Verde - San Onofre - South Texas Project - Wolf Creek

NOC-AE-10002511 Page 2 Enclosure 1 to this letter contains the STPNOC 9-month supplemental response to NRC GL 2008- 01.

Enclosure 2 to this letter contains the STPNOC response to the Request for Additional Information (Reference 4) on the 9 month response to NRC GL 2008-01 provided by STPNOC (Reference 3).

There are no new commitments in this letter.

If there are any questions or if additional information is needed, please contact Mr. Wayne Harrison at 361-972-7298.

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

Executed on -elorm.A It Z010.

G.T. Powell Vice President, Engineering Attachments:

'Enclosure 1 9-Month Supplemental Response to NRC Generic Letter 2008-01, "Managing

NOC-AE-1 0002511 Page 3 cc:

(paper copy) (electronic copy)

Regional Administrator, Region IV A. H. Gutterman, Esquire U. S. Nuclear Regulatory Commission Morgan, Lewis & Bockius LLP 612 East Lamar Blvd, Suite 400 Arlington, Texas 76011-4125 Mohan C. Thadani U. S. Nuclear Regulatory Commission Mohan C. Thadani Kevin Howell Senior Project Manager Catherine Callaway U.S. Nuclear Regulatory'Commission Jim von Suskil One White Flint North (MS 8B1A) NRG South Texas LP 11555 Rockville Pike Rockville, MD 20852 Ed Alarcon Senior Resident Inspector J. J. Nesrsta U. S. Nuclear Regulatory Commission R. K. Temple P.O. Box 289, Mail Code: MN116 Kevin Polio Wadsworth, TX 77483 City Public Service

_Q. M. Canady Jon C. Wood "City of Austin Cox Smith Matthews Electric Utility Department 721 Barton Springs'Road C. Mele Austin, TX 78704 City of Austin Richard A. Ratliff Texas Department of State Health Services Alice Rogers Texas Department of State Health Services

Enclosure 1 NOC-AE-10002511 Page 1 of 2 9-Month Supplemental Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" This enclosure provides the 9-Month Supplemental (Post Outage) Response to Generic Letter 2008-01 for actions that were deferred until after the Unit 1 refueling outage as requested by the NRC in Reference 2 of the cover letter.

Provided in this enclosure is a description of the results of evaluations that were performed pursuant to Generic Letter 2008-01 on the previously incomplete activities, such as system piping walkdowns, at the South Texas Project (STP).

The original conclusions documented in the 9-month response with respect to the licensing basis evaluation, testing evaluations, and corrective action evaluations have not changed. This supplement will only discuss the results of design evaluation reviews conducted since the October 13, 2008 submittal (Reference 3).

A. EVALUATION RESULTS

1. Design Basis Documents No changes have been made to any STP design basis documents as a result of evaluations performed for this GL response.
2. Confirmatory Walkdowns In our 9-month response (Reference 3), STPNOC committed to complete the following:

Complete the slope survey of inaccessible piping in Unit 1 during the fall outage of 2009 and provide a report within 90 days after completion of the outage.

STP slope survey and evaluation of normally inaccessible piping in Unit 1 is complete.

This activity involved slope surveys of applicable GL 2008-01 systems piping in the Unit 1 Reactor Containment Building. Much of the piping required scaffolding to provide proper access to perform the slope surveys.

The piping slope surveys were performed using conventional surveying tools (laser level equipment). The activity involved both un-insulated inaccessible piping and insulated inaccessible piping. On insulated piping, the insulation was temporarily removed as necessary to gain access to the pipe surface. Additionally, ultrasonic examination of selected pump suction piping was performed.

Industry provided guidance was utilized to determine the applicable acceptance criteria and in the assessment of the data. For pump suction piping, industry guidance provided by the Nuclear Energy Institute (NEI) was utilized to perform the evaluations (Reference 8). For pump discharge piping evaluations, industry guidance provided by the Pressurized Water Reactor Owner's Group (PWROG) was utilized (Reference 9). A PWROG Position Paper providing guidance on the quantities of non-condensable gases that can enter the RCS from the ECCS piping was also utilized as required in the

Enclosure 1 NOC-AE-10002511 Page 2 of 2 9-Month Supplemental Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" evaluations (Reference 10). The results of the slope surveys, assessment of data and the evaluations performed on the subject piping were found to be acceptable.

3. Vent Valves No new vent locations or modifications to existing vent valves were identified as a result of the slope surveys or the evaluations performed.
4. Procedures No additional procedures or additional procedure revisions were identified as a result of the slope surveys or the evaluations performed.

B. DESCRIPTION OF NECESSARY ADDITIONAL CORRECTIVE ACTIONS

1. Additional Corrective Actions No additional corrective actions have been identified as a result of the slope surveys and evaluations performed.
2. Corrective Action Updates No updates or changes to previous corrective actions have been identified as a result of the slope surveys and evaluations performed.

Conclusion STP has completed the slope surveys and evaluations of the normally inaccessible portions of GL systems piping in Unit 1 and has concluded they are in compliance with the current licensing and design bases, applicable regulatory requirements and remain capable of performing their design function.

As committed to in Reference 3, the following items remain to be performed:

9 STPNOC will perform the remaining piping slope surveys of normally inaccessible piping inside containment for STP Unit 2 during 2RE1 4, currently scheduled to begin in March of 2010 and provide a report 90 days after completion of the outage.

Enclosure 2 NOC-AE-10002511 Page 1 of 5 Response to Request For Additional Information on 9-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" RAI No. 1:

"STP will evaluate the resolution of TS issues with respect to the changes containedin the Technical Specifications Task Force traveler to determine applicabilityand further assess any changes to the TS and TS Bases" (Reference 4). Clarify the schedule for evaluating the TSTF traveler,and submitting a license amendment, if it is necessary to submit a license amendment as a result of the evaluation of the TSTF traveler.

Response

Should a Technical Specification Task Force (TSTF) traveler be approved, within twelve months of approval STP will evaluate the TSTF position for applicability at STP. If STPNOC should determine that a license amendment request is necessary, a schedule for requesting the submittal will be provided at that time.

RAI No. 2:

In Reference 4 the licensee states that if "voids are found duringperiodic venting, the procedurerequires that the Shift Supervisorbe notified and a condition report would be written in accordancewith the CorrectiveAction program." Clarifyhow the condition is determined, includingany criteriaused. Discuss follow-up actions, such as quantifying the size of the void, and trending the volume of the void.

Response

Periodic venting of the ECCS is per OPSP03-SI-0014 'ECCS Valve Checklist' which, provides instructions for verifying the Emergency Core Cooling System (ECCS) piping is full of water as required by Technical Specification Surveillance Requirement 4.5.2.b.1.

During the performance of this procedure, each ECCS Train (A,B,C) is verified full of water at least once per 31 days by venting at the Safety Injection pump casings and at accessible piping high points. An acceptance criterion per this procedure is "NO air-observed during the venting process". If air is observed during the venting process, the procedure requires notification to the Shift Manager and initiation of a condition report.

The condition report would be evaluated in accordance with our station's Corrective Action Program. This evaluation would include (depending on void location) techniques to quantify the void including utilization of ultrasonic testing (UT) or the performance of a calculation to size the void. Industry guidance has been issued by the Nuclear Energy Institute (APC 09-20) and transmitted to the NRC regarding evaluation of unexpected voids or gas in the ECCS and other systems. Development of a plan of action including appropriate trending would be implemented as necessary for resolution of the condition.

Enclosure 2 NOC-AE-10002511 Page 2 of 5 Response to Request For Additional Information on 9-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" RAI No. 3:

Clarify the meaning of 'accessible'and 'normally inaccessible'as used in references 4 and 5. Include discussion of piping within containment;piping that requires scaffolding to reach; and piping in posted radiationareas.

Response

'Accessible' piping means piping outside of containment that does not require scaffold for access, and is not located in a high radiation area. This includes all of the Safety Injection System and Containment Spray System suction piping and the discharge piping for both systems up to the containment penetration. This was based on guidance from a Nuclear Energy Institute (NEI) Generic Letter 2008-01 response template dated 3/16/2008. As stated in Reference 5 dated January 22, 2009, STPNOC completed the piping surveys and the evaluations of the 'accessible' piping.

'Normally inaccessible' means piping inside containment, or requires scaffolding to access, and/or is located in a high radiation area and where an outage may be required in order to provide the proper access and sufficient planning time. This includes all of the Residual Heat Removal piping, a large portion of the Safety Injection System discharge piping and a large portion of the Containment Spray discharge piping. This was based on guidance from a Nuclear Energy Institute (NEI) Generic Letter 2008-01 response template dated 3/16/2008.

RAI No. 4:

"Water level setpointsalong with system design features are designed to prevent vortex effects that otherwise could potentiallyingest gas into the GL systems during design basis events" (Reference 4). Since flow rates under realistic accident conditions(non-degradedpumps, three trains running)may significantly exceed the design basis accident flow rates,clarify how the stated conclusions are applicableto actual expected accident conditionsin all modes of operation.

Response

It is recognized that in performing vortexing analyses, it is conservative to maximize the assumed flow rate being drawn from the suction source. It is also recognized that actual post-accident plant response can result in significantly higher flow rates being drawn from such a suction source than that assumed in certain design basis accident (DBA) analyses. This is because the DBA analyses assume that one of the ECCS trains could fail to operate as a result of single active failure (for example, failure of a standby diesel generator coincident with loss of offsite power). This would result in the pumps for the affected train not responding, and less than maximum flow rates for the systems.

In the STP Refueling Water Storage Tank vortex breaker evaluation, the above factors are addressed appropriately. The evaluation utilizes conservative, bounding system flow rates assuming a maximum flow scenario in which all three trains of the Safety Injection' System (SIS) and the Containment Spray System (CSS) respond with the corresponding three High Head Safety Injection (HHSI), three Low Head Safety Injection (LHSI) and '

Enclosure 2 NOC-AE-10002511 Page 3 of 5 Response to Request For Additional Information on 9-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" three CSS pumps taking suction from the RWST concurrently. The evaluation is also performed assuming a bounding RWST water level as low as at the top of the installed vortex breaker. The evaluation results are that the RWST vortex breaker will prevent excessive air entrainment over the full range of flows and water levels in the RWST.

The RWST vortex breaker conclusions are therefore applicable to actual expected accident conditions.

In the evaluation of containment emergency sump vortex breakers (one per ECCS train) bounding considerations similar to those used in the RWST evaluation, maximum flow rates at minimum submergence were used. The emergency sump vortex breaker conclusions are applicable to actual expected accident conditions.

RAI No. 5:

The licensee states in Reference 4 that "time delays estimated for delivery of flow for the variousECCS functions are based on pump start times and valve opening times. No additionalallowance for the effects of gas accumulation is included in the calculations." Justify that the use of conservative delays due to pump start and valve actuationis enough to bound the effect of gas accumulation in the subject systems.

Response

STPNOC participates in the NEI Gas Accumulation Team and the respective PWR Owners' Group activities focused on developing suitable guidance for licensees in the evaluation of voids in ECCS piping and responses to various issues relating to GL 2008-

01. In the STPNOC 9-month response to NRC Generic Letter 2008-01 (Reference 4) page 9, reference is made to a PWROG Position Paper (Reference 10) on non-condensable gas voids in ECCS piping entering the RCS. The PWROG Position Paper qualitatively assesses potential effects on RCS Transients including Chapter 15 Events and post accident core cooling. This qualitative evaluation assumes that an equivalent of 5 cubic feet of non-condensable gas at 400 psi is present in the HHSI discharge piping concurrent with 5 cubic feet at 100 psi in the LHSI discharge piping. The PWROG Position Paper also assumed that postulated gas voiding would not delay or reduce ECCS flow beyond the point assumed in the safety analysis of record. The PWROG Position Paper conclusion is that LOCA and Non-LOCA analyses are not impacted and that there would be no impact on post accident core cooling functions due to these assumed quantities of gas, thereby bounding the potential effects of gas accumulation in these systems.

As stated in Reference 4 (page 9) STPNOC has reviewed the PWROG Position Paper and determined the results of the evaluation are applicable to STP. The results of slope surveys and evaluations which have been performed indicate potential for gas voiding is less than the equivalents assumed in the PWROG Position Paper. The generic assumption made in the evaluation that ECCS flow would not be delayed orreduced beyond the point assumed in the safety analysis is applicable for STP. The results of slope survey evaluations indicate the potential for gas voiding is small and would not delay or reduce ECCS flow beyond the point assumed in the safety analysis of record.

Enclosure 2 NOC-AE-10002511 Page 4 of 5 Response to Request For Additional Information on 9-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" Therefore, the pump start times and valve actuation times assumed in the safety analysis bound the effect of gas accumulation.

RAI No. 6:

Training was not identified in the GL (Reference 3) but is considered to be a necessary partof applying procedures and other activities when addressingthe issues identified in the GL as the licensee has recognized. Providea brief descriptionof training.

Response

STPNOC has evaluated gas intrusion in response to SOER 97-1 and SER 02-05. As.a result of our evaluation of these events, STPNOC has revised our initial Licensed Operator Training lesson materials. Specifically, discussions on gas intrusion and our standards for monitoring gas binding have been added to course LOT 201.06, Chemical and Volume Control Systems; and, course LOT 201.10, Emergency Core Cooling Systems. Additionally, continuing training has been developed and implemented for our Instrumentation and Controls Technicians. Specifically, ICCO61.04, Valve Lineups, Filling & Venting, and Operating Experience includes detailed review of the precautions to be used to eliminate gas intrusion when conducting work on various instruments and other plant components. Continuing training has been presented to operations personnel on a biennial basis since the issuance of SOER 97-1. This training covers not only details from the SOER, but recent industry and STP operating experience related to gas accumulation.

Additionally, when station procedures are revised, an assessment for training needs and change management is required in accordance with STPNOC procedure OPAP01ZA0102 'Plant Procedures'. The determination is typically a function of the nature of the change and the perceived impact on the organization. If required, the training is generally accomplished prior to, or in parallel with the issuance of, the procedure. As examples, for the fill and vent and the surveillance procedures revised as a result of this GL, the changes have generally been minor, and have been considered enhancements. For these revisions, the training method or type selected was an e-mail or bulletin communication, issued prior to or in conjunction with the effective date of the procedure revision.

STPNOC is an active participant in the NEI Gas Accumulation Team, which is currently coordinating with the Institute of Nuclear Power Operations (INPO) in the development of generic training modules for gas accumulation and management. These training modules target the Engineering, Operations and Maintenance disciplines. When these training modules are completed STPNOC will evaluate them for applicability, and may implement a version tailored to meet station needs.

REFERENCES

1. "Preliminary Assessment of Responses to Generic Letter 2008-01, 'Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems,' and Future NRC Staff Review Plans." Letter from

Enclosure 2 NOC-AE-10002511 Page 5 of 5 Response to Request For Additional Information on 9-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" Ruland, William H., Nuclear Regulatory Commission to James H. Riley, Nuclear Energy Institute, ML091390637, dated May 28, 2009.

2. "Generic Letter 2008-01 Response Guidance Generic Letter (GL) 2008-01,

'Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Contain Spray Systems.' Evaluation and 3 Month Response Template," Enclosure 2, Generic Letter 2008-01 Response Guidance. Letter from James H. Riley, Director of Engineering, Nuclear Generation Division, Nuclear Energy Institute, to Administrative Points of Contact." ML093070575, dated March 20, 2008.

3. "NRC Generic Letter 2008-01: Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems," Letter from Michael J. Case, Director, Division of Policy and Rulemaking, Office of Nuclear.

Reactor Regulation, Nuclear Regulatory Commission, ML072910759, January 11,2008.

4. "South Texas Project, Units 1 and 2, Docket No. STN 50-498, STN 50-499, Nine-Month Response to NRC Generic Letter 2008-01 ," Letter from G.T.

Powell, Vice President, Engineering, STP Nuclear Operating Company, to Document Control Desk, Nuclear Regulatory Commission, ML082960430, dated October 13, 2008.

5. "South Texas Project, Units 1 and 2, Docket No. STN 50-498, STN 50-499, Nine-Month Supplemental Response to Generic Letter 2008-01 ," Letter to Document Control Desk, NRC, from Vice President, Engineering, STP Nuclear Operating Company, ML090330142, dated January 22, 2009.
6. Warren C. Lyon, U.S. Nuclear Regulatory Commission, "Draft Revision 2 to NRC Staff Criteria for Gas Movement in Suction Lines and Pump Response to Gas," ML090900136, dated March 26, 2009.
7. Letter from W.H. Ruland, U.S. Nuclear Regulatory Commission, to J.H. Riley, NEI, ML081830557, dated July 8, 2008.
8. NEI APC 09-20 from J. H. Riley, NEI, dated May 18, 2009.
9. Letter from PWR Owner's Group, "Transmittal of Revision 1 of Letter Report for "Gas Voids Pressure Pulsations (PA-SEE-0451)" dated September 08, 2008.
10. Letter from Westinghouse, "PWROG Position Paper on Non-condensable Gas Voids in ECCS Piping; Qualitative Engineering Judgment of Potential Effects on Reactor Coolant System Transients Including Chapter 15 Events", dated September 4, 2008.

Text

Nuclear Operating Company South Texas Project Electric Generabn$ Station PO Box 289 Wadsworth Texas 77483 A/vA/*

February 16, 2010 NOC-AE-10002511 10 CFR 50.54(f)

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk 11555 Rockville Pike Rockville, MD 20852 South Texas Project Units 1 and 2 Docket No. STN 50-498, STN 50-499 9-Month Supplemental Response to Generic Letter 2008-01 (TAC Nos. MD7881 and MD7882)

Reference:

1. NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems," dated January 11,2008
2. Letter from Mohan C.7Thadani to Edward D. Halpin dated September 22, 2008, "South Texas Project, Units 1 and 2 - Generic Letter 2008-01, "Managing Gas Accumulation in Emergency.Core Cooling, Decay Heat Removal, and Containment Spray Systems," Proposed Alternative Course of Action and Request for Additional Information (TAC Nos. MD7881 and MD7882).
3. Letter from G. T. Powell to NRC Document Control Desk dated October 13,:

2008, "Nine-Month Response to Generic Letter 2008-01". (NOC-AE-08002355)

(ML082960430)

4. Email from Mohan C. Thadani to Albon W. Harrison dated October 13, 2009,,

Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core.

Cooling, Decay Heat Removal, and Containment Spray Systems,"

(ML092860079)

The Nuclear Regulatory Commission (NRC) issued GenericLetter (GL) 2008-01 (Reference 1) to request that each licensee evaluate the emergency core cooling, (ECCS), decay heat removal (DHR), and containment spray systems to ensure that gas accumulation is maintained less than the amount that challenges operability of these systems, and that appropriate action is taken when conditions adverse to quality are identified.

As requested in Reference 2 and committed to in Reference 3, please find attached the South Texas Project (STP) supplemental response to the 9-month response letter (Reference 3).

In summary, STP Nuclear Operating Company (STPNOC) has concluded that based on the previous reviews of the current plant configuration, plant specific operating experience, and procedure reviews the subject systems/functions are in compliance with the current licensing and design bases and applicable regulatory requirements. System piping walkdowns and slope

.determinations performed to date have not yielded any information to alter this conclusion. All identified systems are capable of performing their design function.

STI: 32603566 A member of the STARS (Strategic.Teaming and Resource Sharing) Alliance IyI Callaway - Comanche Peak - Diablo Canyon - Palo Verde - San Onofre - South Texas Project - Wolf Creek

NOC-AE-10002511 Page 2 Enclosure 1 to this letter contains the STPNOC 9-month supplemental response to NRC GL 2008- 01.

Enclosure 2 to this letter contains the STPNOC response to the Request for Additional Information (Reference 4) on the 9 month response to NRC GL 2008-01 provided by STPNOC (Reference 3).

There are no new commitments in this letter.

If there are any questions or if additional information is needed, please contact Mr. Wayne Harrison at 361-972-7298.

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

Executed on -elorm.A It Z010.

G.T. Powell Vice President, Engineering Attachments:

'Enclosure 1 9-Month Supplemental Response to NRC Generic Letter 2008-01, "Managing

NOC-AE-1 0002511 Page 3 cc:

(paper copy) (electronic copy)

Regional Administrator, Region IV A. H. Gutterman, Esquire U. S. Nuclear Regulatory Commission Morgan, Lewis & Bockius LLP 612 East Lamar Blvd, Suite 400 Arlington, Texas 76011-4125 Mohan C. Thadani U. S. Nuclear Regulatory Commission Mohan C. Thadani Kevin Howell Senior Project Manager Catherine Callaway U.S. Nuclear Regulatory'Commission Jim von Suskil One White Flint North (MS 8B1A) NRG South Texas LP 11555 Rockville Pike Rockville, MD 20852 Ed Alarcon Senior Resident Inspector J. J. Nesrsta U. S. Nuclear Regulatory Commission R. K. Temple P.O. Box 289, Mail Code: MN116 Kevin Polio Wadsworth, TX 77483 City Public Service

_Q. M. Canady Jon C. Wood "City of Austin Cox Smith Matthews Electric Utility Department 721 Barton Springs'Road C. Mele Austin, TX 78704 City of Austin Richard A. Ratliff Texas Department of State Health Services Alice Rogers Texas Department of State Health Services

Enclosure 1 NOC-AE-10002511 Page 1 of 2 9-Month Supplemental Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" This enclosure provides the 9-Month Supplemental (Post Outage) Response to Generic Letter 2008-01 for actions that were deferred until after the Unit 1 refueling outage as requested by the NRC in Reference 2 of the cover letter.

Provided in this enclosure is a description of the results of evaluations that were performed pursuant to Generic Letter 2008-01 on the previously incomplete activities, such as system piping walkdowns, at the South Texas Project (STP).

The original conclusions documented in the 9-month response with respect to the licensing basis evaluation, testing evaluations, and corrective action evaluations have not changed. This supplement will only discuss the results of design evaluation reviews conducted since the October 13, 2008 submittal (Reference 3).

A. EVALUATION RESULTS

1. Design Basis Documents No changes have been made to any STP design basis documents as a result of evaluations performed for this GL response.
2. Confirmatory Walkdowns In our 9-month response (Reference 3), STPNOC committed to complete the following:

Complete the slope survey of inaccessible piping in Unit 1 during the fall outage of 2009 and provide a report within 90 days after completion of the outage.

STP slope survey and evaluation of normally inaccessible piping in Unit 1 is complete.

This activity involved slope surveys of applicable GL 2008-01 systems piping in the Unit 1 Reactor Containment Building. Much of the piping required scaffolding to provide proper access to perform the slope surveys.

The piping slope surveys were performed using conventional surveying tools (laser level equipment). The activity involved both un-insulated inaccessible piping and insulated inaccessible piping. On insulated piping, the insulation was temporarily removed as necessary to gain access to the pipe surface. Additionally, ultrasonic examination of selected pump suction piping was performed.

Industry provided guidance was utilized to determine the applicable acceptance criteria and in the assessment of the data. For pump suction piping, industry guidance provided by the Nuclear Energy Institute (NEI) was utilized to perform the evaluations (Reference 8). For pump discharge piping evaluations, industry guidance provided by the Pressurized Water Reactor Owner's Group (PWROG) was utilized (Reference 9). A PWROG Position Paper providing guidance on the quantities of non-condensable gases that can enter the RCS from the ECCS piping was also utilized as required in the

Enclosure 1 NOC-AE-10002511 Page 2 of 2 9-Month Supplemental Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" evaluations (Reference 10). The results of the slope surveys, assessment of data and the evaluations performed on the subject piping were found to be acceptable.

3. Vent Valves No new vent locations or modifications to existing vent valves were identified as a result of the slope surveys or the evaluations performed.
4. Procedures No additional procedures or additional procedure revisions were identified as a result of the slope surveys or the evaluations performed.

B. DESCRIPTION OF NECESSARY ADDITIONAL CORRECTIVE ACTIONS

1. Additional Corrective Actions No additional corrective actions have been identified as a result of the slope surveys and evaluations performed.
2. Corrective Action Updates No updates or changes to previous corrective actions have been identified as a result of the slope surveys and evaluations performed.

Conclusion STP has completed the slope surveys and evaluations of the normally inaccessible portions of GL systems piping in Unit 1 and has concluded they are in compliance with the current licensing and design bases, applicable regulatory requirements and remain capable of performing their design function.

As committed to in Reference 3, the following items remain to be performed:

9 STPNOC will perform the remaining piping slope surveys of normally inaccessible piping inside containment for STP Unit 2 during 2RE1 4, currently scheduled to begin in March of 2010 and provide a report 90 days after completion of the outage.

Enclosure 2 NOC-AE-10002511 Page 1 of 5 Response to Request For Additional Information on 9-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" RAI No. 1:

"STP will evaluate the resolution of TS issues with respect to the changes containedin the Technical Specifications Task Force traveler to determine applicabilityand further assess any changes to the TS and TS Bases" (Reference 4). Clarify the schedule for evaluating the TSTF traveler,and submitting a license amendment, if it is necessary to submit a license amendment as a result of the evaluation of the TSTF traveler.

Response

Should a Technical Specification Task Force (TSTF) traveler be approved, within twelve months of approval STP will evaluate the TSTF position for applicability at STP. If STPNOC should determine that a license amendment request is necessary, a schedule for requesting the submittal will be provided at that time.

RAI No. 2:

In Reference 4 the licensee states that if "voids are found duringperiodic venting, the procedurerequires that the Shift Supervisorbe notified and a condition report would be written in accordancewith the CorrectiveAction program." Clarifyhow the condition is determined, includingany criteriaused. Discuss follow-up actions, such as quantifying the size of the void, and trending the volume of the void.

Response

Periodic venting of the ECCS is per OPSP03-SI-0014 'ECCS Valve Checklist' which, provides instructions for verifying the Emergency Core Cooling System (ECCS) piping is full of water as required by Technical Specification Surveillance Requirement 4.5.2.b.1.

During the performance of this procedure, each ECCS Train (A,B,C) is verified full of water at least once per 31 days by venting at the Safety Injection pump casings and at accessible piping high points. An acceptance criterion per this procedure is "NO air-observed during the venting process". If air is observed during the venting process, the procedure requires notification to the Shift Manager and initiation of a condition report.

The condition report would be evaluated in accordance with our station's Corrective Action Program. This evaluation would include (depending on void location) techniques to quantify the void including utilization of ultrasonic testing (UT) or the performance of a calculation to size the void. Industry guidance has been issued by the Nuclear Energy Institute (APC 09-20) and transmitted to the NRC regarding evaluation of unexpected voids or gas in the ECCS and other systems. Development of a plan of action including appropriate trending would be implemented as necessary for resolution of the condition.

Enclosure 2 NOC-AE-10002511 Page 2 of 5 Response to Request For Additional Information on 9-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" RAI No. 3:

Clarify the meaning of 'accessible'and 'normally inaccessible'as used in references 4 and 5. Include discussion of piping within containment;piping that requires scaffolding to reach; and piping in posted radiationareas.

Response

'Accessible' piping means piping outside of containment that does not require scaffold for access, and is not located in a high radiation area. This includes all of the Safety Injection System and Containment Spray System suction piping and the discharge piping for both systems up to the containment penetration. This was based on guidance from a Nuclear Energy Institute (NEI) Generic Letter 2008-01 response template dated 3/16/2008. As stated in Reference 5 dated January 22, 2009, STPNOC completed the piping surveys and the evaluations of the 'accessible' piping.

'Normally inaccessible' means piping inside containment, or requires scaffolding to access, and/or is located in a high radiation area and where an outage may be required in order to provide the proper access and sufficient planning time. This includes all of the Residual Heat Removal piping, a large portion of the Safety Injection System discharge piping and a large portion of the Containment Spray discharge piping. This was based on guidance from a Nuclear Energy Institute (NEI) Generic Letter 2008-01 response template dated 3/16/2008.

RAI No. 4:

"Water level setpointsalong with system design features are designed to prevent vortex effects that otherwise could potentiallyingest gas into the GL systems during design basis events" (Reference 4). Since flow rates under realistic accident conditions(non-degradedpumps, three trains running)may significantly exceed the design basis accident flow rates,clarify how the stated conclusions are applicableto actual expected accident conditionsin all modes of operation.

Response

It is recognized that in performing vortexing analyses, it is conservative to maximize the assumed flow rate being drawn from the suction source. It is also recognized that actual post-accident plant response can result in significantly higher flow rates being drawn from such a suction source than that assumed in certain design basis accident (DBA) analyses. This is because the DBA analyses assume that one of the ECCS trains could fail to operate as a result of single active failure (for example, failure of a standby diesel generator coincident with loss of offsite power). This would result in the pumps for the affected train not responding, and less than maximum flow rates for the systems.

In the STP Refueling Water Storage Tank vortex breaker evaluation, the above factors are addressed appropriately. The evaluation utilizes conservative, bounding system flow rates assuming a maximum flow scenario in which all three trains of the Safety Injection' System (SIS) and the Containment Spray System (CSS) respond with the corresponding three High Head Safety Injection (HHSI), three Low Head Safety Injection (LHSI) and '

Enclosure 2 NOC-AE-10002511 Page 3 of 5 Response to Request For Additional Information on 9-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" three CSS pumps taking suction from the RWST concurrently. The evaluation is also performed assuming a bounding RWST water level as low as at the top of the installed vortex breaker. The evaluation results are that the RWST vortex breaker will prevent excessive air entrainment over the full range of flows and water levels in the RWST.

The RWST vortex breaker conclusions are therefore applicable to actual expected accident conditions.

In the evaluation of containment emergency sump vortex breakers (one per ECCS train) bounding considerations similar to those used in the RWST evaluation, maximum flow rates at minimum submergence were used. The emergency sump vortex breaker conclusions are applicable to actual expected accident conditions.

RAI No. 5:

The licensee states in Reference 4 that "time delays estimated for delivery of flow for the variousECCS functions are based on pump start times and valve opening times. No additionalallowance for the effects of gas accumulation is included in the calculations." Justify that the use of conservative delays due to pump start and valve actuationis enough to bound the effect of gas accumulation in the subject systems.

Response

STPNOC participates in the NEI Gas Accumulation Team and the respective PWR Owners' Group activities focused on developing suitable guidance for licensees in the evaluation of voids in ECCS piping and responses to various issues relating to GL 2008-

01. In the STPNOC 9-month response to NRC Generic Letter 2008-01 (Reference 4) page 9, reference is made to a PWROG Position Paper (Reference 10) on non-condensable gas voids in ECCS piping entering the RCS. The PWROG Position Paper qualitatively assesses potential effects on RCS Transients including Chapter 15 Events and post accident core cooling. This qualitative evaluation assumes that an equivalent of 5 cubic feet of non-condensable gas at 400 psi is present in the HHSI discharge piping concurrent with 5 cubic feet at 100 psi in the LHSI discharge piping. The PWROG Position Paper also assumed that postulated gas voiding would not delay or reduce ECCS flow beyond the point assumed in the safety analysis of record. The PWROG Position Paper conclusion is that LOCA and Non-LOCA analyses are not impacted and that there would be no impact on post accident core cooling functions due to these assumed quantities of gas, thereby bounding the potential effects of gas accumulation in these systems.

As stated in Reference 4 (page 9) STPNOC has reviewed the PWROG Position Paper and determined the results of the evaluation are applicable to STP. The results of slope surveys and evaluations which have been performed indicate potential for gas voiding is less than the equivalents assumed in the PWROG Position Paper. The generic assumption made in the evaluation that ECCS flow would not be delayed orreduced beyond the point assumed in the safety analysis is applicable for STP. The results of slope survey evaluations indicate the potential for gas voiding is small and would not delay or reduce ECCS flow beyond the point assumed in the safety analysis of record.

Enclosure 2 NOC-AE-10002511 Page 4 of 5 Response to Request For Additional Information on 9-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" Therefore, the pump start times and valve actuation times assumed in the safety analysis bound the effect of gas accumulation.

RAI No. 6:

Training was not identified in the GL (Reference 3) but is considered to be a necessary partof applying procedures and other activities when addressingthe issues identified in the GL as the licensee has recognized. Providea brief descriptionof training.

Response

STPNOC has evaluated gas intrusion in response to SOER 97-1 and SER 02-05. As.a result of our evaluation of these events, STPNOC has revised our initial Licensed Operator Training lesson materials. Specifically, discussions on gas intrusion and our standards for monitoring gas binding have been added to course LOT 201.06, Chemical and Volume Control Systems; and, course LOT 201.10, Emergency Core Cooling Systems. Additionally, continuing training has been developed and implemented for our Instrumentation and Controls Technicians. Specifically, ICCO61.04, Valve Lineups, Filling & Venting, and Operating Experience includes detailed review of the precautions to be used to eliminate gas intrusion when conducting work on various instruments and other plant components. Continuing training has been presented to operations personnel on a biennial basis since the issuance of SOER 97-1. This training covers not only details from the SOER, but recent industry and STP operating experience related to gas accumulation.

Additionally, when station procedures are revised, an assessment for training needs and change management is required in accordance with STPNOC procedure OPAP01ZA0102 'Plant Procedures'. The determination is typically a function of the nature of the change and the perceived impact on the organization. If required, the training is generally accomplished prior to, or in parallel with the issuance of, the procedure. As examples, for the fill and vent and the surveillance procedures revised as a result of this GL, the changes have generally been minor, and have been considered enhancements. For these revisions, the training method or type selected was an e-mail or bulletin communication, issued prior to or in conjunction with the effective date of the procedure revision.

STPNOC is an active participant in the NEI Gas Accumulation Team, which is currently coordinating with the Institute of Nuclear Power Operations (INPO) in the development of generic training modules for gas accumulation and management. These training modules target the Engineering, Operations and Maintenance disciplines. When these training modules are completed STPNOC will evaluate them for applicability, and may implement a version tailored to meet station needs.

REFERENCES

1. "Preliminary Assessment of Responses to Generic Letter 2008-01, 'Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems,' and Future NRC Staff Review Plans." Letter from

Enclosure 2 NOC-AE-10002511 Page 5 of 5 Response to Request For Additional Information on 9-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" Ruland, William H., Nuclear Regulatory Commission to James H. Riley, Nuclear Energy Institute, ML091390637, dated May 28, 2009.

2. "Generic Letter 2008-01 Response Guidance Generic Letter (GL) 2008-01,

'Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Contain Spray Systems.' Evaluation and 3 Month Response Template," Enclosure 2, Generic Letter 2008-01 Response Guidance. Letter from James H. Riley, Director of Engineering, Nuclear Generation Division, Nuclear Energy Institute, to Administrative Points of Contact." ML093070575, dated March 20, 2008.

3. "NRC Generic Letter 2008-01: Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems," Letter from Michael J. Case, Director, Division of Policy and Rulemaking, Office of Nuclear.

Reactor Regulation, Nuclear Regulatory Commission, ML072910759, January 11,2008.

4. "South Texas Project, Units 1 and 2, Docket No. STN 50-498, STN 50-499, Nine-Month Response to NRC Generic Letter 2008-01 ," Letter from G.T.

Powell, Vice President, Engineering, STP Nuclear Operating Company, to Document Control Desk, Nuclear Regulatory Commission, ML082960430, dated October 13, 2008.

5. "South Texas Project, Units 1 and 2, Docket No. STN 50-498, STN 50-499, Nine-Month Supplemental Response to Generic Letter 2008-01 ," Letter to Document Control Desk, NRC, from Vice President, Engineering, STP Nuclear Operating Company, ML090330142, dated January 22, 2009.
6. Warren C. Lyon, U.S. Nuclear Regulatory Commission, "Draft Revision 2 to NRC Staff Criteria for Gas Movement in Suction Lines and Pump Response to Gas," ML090900136, dated March 26, 2009.
7. Letter from W.H. Ruland, U.S. Nuclear Regulatory Commission, to J.H. Riley, NEI, ML081830557, dated July 8, 2008.
8. NEI APC 09-20 from J. H. Riley, NEI, dated May 18, 2009.
9. Letter from PWR Owner's Group, "Transmittal of Revision 1 of Letter Report for "Gas Voids Pressure Pulsations (PA-SEE-0451)" dated September 08, 2008.
10. Letter from Westinghouse, "PWROG Position Paper on Non-condensable Gas Voids in ECCS Piping; Qualitative Engineering Judgment of Potential Effects on Reactor Coolant System Transients Including Chapter 15 Events", dated September 4, 2008.
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