ML082890540

9 Month Response to NRC Generic Letter 2008-01: Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems, Dated 01/11/2008

ML082890540
Person / Time
Site:	Browns Ferry, Watts Bar, Sequoyah
Issue date:	10/11/2008
From:	Purcell M Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
GL-08-001
Download: ML082890540 (44)

Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402-2801 October 11, 2008 10 CFR 50.54(f)

U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 In the Matter of

)

Docket Nos.

50-259 50-327 Tennessee Valley Authority

)

50-260 50-328 50-296 50-390 BROWNS FERRY NUCLEAR PLANT (BFN) UNITS 1, 2 AND 3, SEQUOYAH NUCLEAR PLANT (SQN) UNITS 1 AND 2, AND WATTS BAR NUCLEAR PLANT (WBN) UNIT I - 9 MONTH RESPONSE TO NRC GENERIC LETTER (GL) 2008-01:

MANAGING GAS ACCUMULATION IN EMERGENCY CORE COOLING, DECAY HEAT REMOVAL, AND CONTAINMENT SPRAY SYSTEMS, DATED JANUARY 11, 2008

References:

1. TVA's letter to NRC dated May 9, 2008, Initial Response to NRC GL 2008-01: Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment-Spray Systems, Dated January 11, 2008

2. TVA's letter to NRC dated June 6, 2008, Revised Initial Response to NRC GL 2008-01: Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems, Dated January 11, 2008

3. TVA's letter to NRC dated July 11, 2008, NRC GL 2008-01:

Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems, Dated January 11, 2008 - Revised Commitment

4. Nuclear Energy Institute (NEI) Letter to APC 08-13, September 24, 2008, Generic Letter (GL) 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems, Evaluation and 9-Month Response Template, Revision 1

5. NEI Letter to APC dated March 20, 2008, Generic Letter (GL) 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment, Spray Systems Printed on recycled paper

U.S. Nuclear Regulatory Commission Page 2 October 11, 2008

6. NRC's letter to TVA dated September 25, 2008, Brown Ferry Nuclear Plant, Units 1, 2, and 3, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems, Proposed Alternative Course of Action The purpose of this letter is to provide TVA's "9-Month" response to GL 2008-01.

TVA's initial responses were provided in references 1, 2, and 3 above.

NRC issued GL 2008-01 requesting that each licensee evaluate the licensing basis, design, testing, and Corrective Action Programs for the Emergency Core Cooling Systems (ECCS), Decay Heat Removal (DHR) System, and Containment Spray System, 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.

GL 2008-01 requested each licensee to submit a written response in accordance with 10 CFR 50.54(f) within 9 months of the date of the GL to provide the following information:

(a)

A description of the results of evaluations that were performed pursuant to the requested actions of the GL. This description should provide sufficient information to demonstrate that you are or will be in compliance with the quality assurance criteria in Sections III, V, XI, XVI, and XVII of Appendix B to 10 CFR Part 50 and the licensing basis and operating license as those requirements apply to the subject systems of.the GL; (b)

A description of all corrective actions, including plant, programmatic, procedure, and licensing basis modifications that you determined were necessary to assure compliance with the quality assurance criteria in Sections III, V, Xl, XVI, and XVII of Appendix B to 10 CFR Part 50 and the licensing basis and operating license as those requirements apply to the subject systems of the GL; and, (c)

A statement regarding which corrective actions were completed, the schedule for completing the remaining corrective actions, and the basis for that schedule.

TVA has completed the evaluations in accordance with the GL and determined that the primary systems addressed in the GL are in compliance with the Technical Specification definition of Operability, i.e.; capable of performing their intended safety function. In addition, BFN, SQN and WBN are in compliance with 10 CFR 50, Appendix B, Criterion Ill, V, XI, XVI and XVII, with respect to the concerns outlined in GL.

U.S. Nuclear Regulatory Commission Page 3 October 11, 2008 Enclosures 1 through 3 of this letter contain TVA's "9-Month" response to GL 2008-01 for BFN, SQN and WBN, respectively. These enclosures follow the format and content of the guidance provided in reference 4 and were performed using the evaluation guidance provided in reference 5.

In accordance with TVA's commitments provided in reference 3 and the NRC's discussion in reference 6, TVA will conduct walkdowns of piping inside containment at BFN Unit 1 during the fall 2008 refueling outage. Due to recent industry developments, however, TVA will follow NRC and industry discussions concerning whether walkdowns inside containment are necessary for the Boiling Water Reactor design. If NRC agreement is reached and additional walkdowns are determined unnecessary for BFN Units 2 and 3, then TVA will revise our plans and commitments for these units accordingly. Enclosure 4 contains a list of new TVA Commitments made by this letter.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the /0 day of de-1, 2008.

Sincerel, M' hael A. Purcell Senior Licensing Manager Nuclear Power Group Enclosures cc

See page 4

U.S. Nuclear Regulatory Commission Page 4 October 11, 2008 Enclosures cc (Enclosures):

Eva A. Brown, Senior Project Manager U.S. Nuclear Regulatory Commission MS 08G9A One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2738 Thomas H. Boyce, Chief, Branch 11-2 U.S. Nuclear Regulatory Commission One White Flint North MS 08G9A 11555 Rockville Pike Rockville, Maryland 20852-2738 John G. Lamb, Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North MS 80B1A 11555 Rockville Pike Rockville, Maryland 20852-2738 Brendan T. Moroney, Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North MS 8G9A 11555 Rockville Pike Rockville, Maryland 20852-2738 Regional Administrator U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303-8931 NRC Senior Resident Inspector Browns Ferry Nuclear Plant 10833 Shaw Road Athens, Alabama 35611-6970 NRC Senior Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379-3624 NRC Senior Resident Inspector Watts Bar Nuclear Plant 1260 Nuclear Plant Road Spring City, Tennessee 37381-2000

ENCLOSUREI 9-MONTH RESPONSE TO NRC GENERIC LETTER (GL) 2008-01 REQUESTED INFORMATION FOR BROWN'S FERRY NUCLEAR PLANT (BFN)

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This Enclosure contains the BFN 9-Month Response to NRC Generic Letter (GL) 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems, dated January 11, 2008. In GL 2008-01, the NRC requested "that each addressee evaluate its ECCS, DHR System, and Containment Spray System licensing basis, design, testing, and corrective actions 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."

The following information is provided in this response:

a) A description of the results of evaluations that were performed pursuant to the requested actions in the GL (see Section A of this Enclosure),

b) A description of all corrective actions determined necessary to assure compliance with the quality assurance criteria in Sections III, V, XI, XVI, and XVII of Appendix B to 10 CFR Part 50 and the licensing basis and operating license with respect to the systems identified in the GL (see Section B of this Enclosure), and c) A statement regarding which corrective actions were completed by October 11, 2008, the schedule for completing the corrective actions not completed by October 11, 2008, and the basis for that schedule (see Section C of this Enclosure).

The following systems were determined to be in the scope of GL 2008-01 for BFN:

Emergency Core Cooling System

° Decay Heat Removal System However, there are related issues that the nuclear industry is currently considering with respect to the overall performance of these systems (e.g., Generic Safety Issue (GSI)-193). Resolution of these issues will continue to be pursued through the various Owner's Groups and industry leadership organizations and are not addressed herein.

A. EVALUATION RESULTS Licensing Basis Evaluation The BFN licensing basis was reviewed with respect to gas accumulation in the Emergency Core Cooling and Decay Heat Removal System. This review included the Technical Specifications (TS), TS Bases, Updated Final Safety Analysis Report (UFSAR), the Technical Requirements Manual (TRM) and TRM Bases, responses to NRC Generic Communications, Regulatory Commitments, and License Conditions.

1. Summarize the results of the review of these documents:

The above documents and regulatory commitments were evaluated for compliance with applicable regulatory requirements. This review determined that the licensing basis for the ECCS and DHR System is that voiding in these systems is maintained at a level that does not significantly affect their performance when mitigating design basis accidents (DBAs) or while maintaining safe shutdown (SSD). Therefore, to be in compliance with the E1-2

licensing basis for BFN, voiding in these systems must be maintained at a level that does not significantly affect the performance of these systems when mitigating DBAs or maintaining SSD.

2. Summarize the changes to licensing basis documents (Corrective Actions):

BFN has not made any changes to licensing basis documents as a result of this GL response.

3. Provide a detailed list of items that have not been completed, a schedule for their completion, and the basis for that schedule.

TS improvements are being addressed by the Technical Specifications Task Force (TSTF) to provide an approved TSTF Traveler for making changes to individual licensee's TS related to the potential for unacceptable gas accumulation. The development of the TSTF Traveler relies on the results of the evaluations of a large number of licensees to address the various plant designs. TVA is continuing to support the industry and Nuclear Energy Institute (NEI) Gas Accumulation Management Team activities regarding the resolution of Generic TS changes via the TSTF Traveler process. After NRC approval of the Traveler, TVA will evaluate its applicability to the BFN, and evaluate adopting the Traveler to either supplement or replace the current TS requirements.

Design Evaluation The BFN design basis was reviewed with respect to gas accumulation in the Emergency Core Cooling and Decay Heat Removal Systems. This review included Design Basis Documents, Calculations, Engineering Evaluations, and Vendor Technical Manuals.

1. Discuss the results of the review of the design basis documents. This discussion should include a description of any plant specific calculations or analyses that were performed to confirm the acceptability of gas accumulation in the piping of the affected systems, including any acceptance criteria if applicable. Note: This should describe the "as found" (pre Generic Letter) condition prior to any corrective or enhancement actions.

This review determined that the ECCS and DHR System design includes features that ensure pumps, pipe and components are maintained full of water. These features include:

The pumps are located below their suction sources with no inverted U-turns in the suction pipe.

The level in the suction sources is monitored and minimum water levels have been established to ensure that unacceptable air ingestion does not occur during a DBA.

" The level instrumentation on these sources is sloped to ensure it can be filled and vented.

Suction pipe is at greater than atmospheric pressure during power operation.

There are no significant sources of gas in suction or discharge pipe.

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Pumps have full flow test lines and are periodically run at a flow rate sufficient to sweep voids through the suction pipe or at the maximum flow rate expected during a DBA.

Discharge pipe that is susceptible to voiding due to leakage is connected to a continuous makeup flow (head tank) to prevent void formation.

In addition, there are no component void traps in the suction pipe that would result in a void being transported in whole to the pump suction.

Review of the Design Control Program determined that the design change review checklist should have an explicit item to determine if the design change introduces or increases the potential for gas accumulation beyond established acceptance criteria. This adds an additional procedural barrier to prevent unintended consequences from plant changes and is an enhancement to the Design Control Program.

2. Discuss new applicable gas volume acceptance criteria for each piping segment in each system where gas can accumulate where no acceptance criteria previously existed and summarize the Corrective Actions, and schedule for completion of any Corrective Actions.

a) Pump Suction Piping Pump suction void volume acceptance criteria was determined to be a bounding 2 percent void fraction for continuous voiding and 10 percent void fraction for up to 5 seconds for latent voids. These conservative criteria have been applied in support of system operability until further data supports a change. These values used in conjunction with other factors such as Net Positive Suction Head required (NPSHr), duration of gas flow, and transients for which the system is credited provide a basis for system operability.

b) Pump discharge piping which is susceptible to pressure pulsation after a pump start Pump discharge void volume acceptance criteria was based on maintaining pressure pulsations less than that which would cause a discharge pipe relief valve to lift or result in a hydraulic force that causes pipe stress to exceed allowable values. In order to meet these criteria, there must be no sudden changes in flow as the ECCS and DHR System Pumps start and compresses voids in the discharge pipe. These criteria are usually met when the discharge pipe has been filled to the isolation valve as this prevents an abrupt stopping of flow. In an otherwise full pipe system, voids due to unfavorable pipe slope and bow in nominally horizontal pipe or trapped due to flow obstructions (e.g., orifice plates) are gradually compressed and do not result in an unacceptable pressure transient during pump start.

An analysis of ECCS piping downstream of the injection valves has been completed and a determination made that the existence of air voids in this piping except for High Pressure Coolant Injection (HPCI) will have no adverse consequences related to accident conditions. Even if small voids E1-4

did exist the pressure transient would not be greater than the normal injection pressure.

A separate evaluation was performed for the HPCI discharge pipe. The configuration of this pipe allows for all voids upstream of the discharge isolation valve to be swept to the condensate storage tank during periodic pump tests. The discharge pressure of the HPCI Pump is much higher than the pressure in the primary system so the flow through the discharge pipe to the reactor vessel does not stop during a DBA. For these reasons, the pressure transient due to voids in the HPCI discharge pipe will be mild.

The HPCI discharge pipe does not have a relief valve.

c) Pump discharge piping which is not susceptible to water hammer or pressure pulsation following a pump start The DHR System Pumps can be aligned to the drywell and wetwell spray headers. Because the pipe downstream of the spray header isolation valves is open to the containment atmosphere, the pipe downstream of the discharge isolation valves is not subject to pressure pulsations or waterhammer when the DHR System Pumps discharge to these empty spray headers.

d) Primary System Allowable Gas Ingestion The effects of latent gas voids being injected into the reactor vessel during a DBA were evaluated. A conservative "worst case" scenario evaluation provided a limiting Loss of Coolant Accident (LOCA) Peak Clad Temperature (PCT) heatup rate of 12 °F/s is determined for the entire United States Boiling Water Reactor (BWR) fleet. Using this heatup rate, 48 OF of PCT impact is assessed with a maximum of 4-second delay in the ECCS actuation.

An assessment justified that gas voids passing through the core do not pose an additional safety concern mainly because of the unlikely path for air to get into the core and high void conditions in the core present during LOCA.

Assessments on the Loss of Feedwater (LOFW) and Anticipated Transient Without Scram (ATWS) events concluded that a delay of 5 seconds in ECCS flow would affect the analysis results insignificantly and have no impact on meeting the acceptance criteria. The evaluation of station blackout events indicates that a delay of 10 seconds would not impact the ability of the water makeup system to maintain the vessel water level above the top of active fuel. Similarly, it is concluded that a delay of 10 seconds would have an insignificant impact on meeting the acceptance criteria in Appendix R fire safe shutdown analysis.

The ECCS and DHR System Pumps have a high flow rate during a DBA.

For example, the HPCI Pump delivers 5000 gpm. A 4 second delay in delivering this flow during a LOCA corresponds to more than 40 cubic feet.

of voided discharge pipe. This amount of gas voiding is much greater than could exist in a filled ECCS.

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In summary, the effect on the ECCS core cooling function of non-condensable gas entering the primary system was assessed and found not to be limiting with respect to allowable void size.

3. Summarize the changes, if any, to the design basis documents (Corrective Actions) and the schedule for completion of the Corrective Actions.

The review determined that no changes to design basis documents are required. However, as discussed in Item (1), an enhancement is being made to the design change review checklist through the Corrective Action Program.

4. Discuss the results of the system P&ID and isometric drawing reviews to identify all system vents and high points.

The ECCS and DHR System mechanical flow diagrams, physical pipe drawings and isometric drawings were reviewed. The pipe configuration in these systems is relatively simple so the physical pipe drawings were used to evaluate each pipe segment. These systems were designed to be filled by gravity feed from their water sources. The review of the pipe configuration determined vents are located such that all significant voids can be removed by gravity fill from the systems water sources. The drawing review determined that in the absence of significant adverse pipe slope or pipe bow in nominally horizontal pipe, these systems have sufficient vent valves at the proper locations to allow for filling of pipes and components (e.g., no inverted U-turns in the pipe). As discussed in Item (6), nominally horizontal pipe has been surveyed to identify adverse pipe slope or pipe bow.

5. Identify new vent valve locations, modifications to existing vent valves, or utilization of existing vent valves based on the drawing review, and summarize the Corrective Actions, and schedule for completion of the Corrective Actions.

The drawing review did not identify the need for additional vent valves.

6. Discuss the results (including the scope and acceptance criteria used) of the system confirmation walkdowns that have been completed for the portions of the systems that require venting to ensure that they are sufficiently full of water.

Suction Pipe:

The ECCS and DHR System Pumps are periodically tested at the maximum flow rate expected during a Design Basis Accident (DBA) or at a flow rate that transports any voids in their suction pipe and part of their discharge pipe to the Pressure Suppression Chamber (PSC).

An exception to the above is the suction pipe from the PSC to the HPCI Pump. The HPCI Pump is normally aligned and periodically run with its suction aligned to the condensate storage tank. During some DBA scenarios, the HPCI Pump is run with its suction aligned to the PSC. The HPCI Pump suction pipe from the PSC was surveyed and no locations were found that would result in a void fraction at the HPCI Pump in excess of its acceptance E1-6

criteria. In addition, the HPCI Pump suction pipe from the PSC was inspected by Ultrasonic Testing (UT) and it was confirmed that this pipe is full.

Although not necessary to ensure the remaining ECCS and DHR System suction pipe does not contain voids, this pipe was surveyed for unfavorable pipe slope or pipe bow. Because some locations in the suction pipe were identified that have unfavorable pipe slope or pipe bow, operating procedures are being revised to require dynamic venting of these locations should this pipe be drained (see Item (8)). As stated above, periodic testing of the ECCS and DHR System Pumps ensure that the suction pipe does not have any locations that contain a void that would result in a void fraction at the pump in excess of its acceptance criteria.

A portion of the DHR System suction pipe from the primary system is located inside containment. The survey of this pipe was identified in references 2 and 3 as being deferred until the next refueling outage for each unit. Due to the configuration of this pipe and its distance from the DHR System Pump suction, it cannot contain a void large enough to cause a loss of the DHR System Pumps when they take suction from the primary system. The DHR System Pumps have not become gas bound with their suctions' aligned to the primary system for shutdown cooling. Therefore, this pipe is no longer required to be surveyed in upcoming refueling outages.

Discharge Pipe:

The survey of the ECCS and DHR System discharge pipe identified some locations that due to unfavorable pipe slope or pipe bow could contain a void; however, voids at these locations are either swept to the PSC or Condensate Storage Tank (CST) during periodic pump tests or are well below the size that would result in significant pressure pulsations. For example, the largest possible void in the Core Spray Pump discharge pipe that is not swept during periodic pump tests has a maximum cross section of 7 percent of the pipe flow area. Even though the maximum possible void in this pipe segment is acceptable portions of the pipe segments were inspected by UT and no voiding was identified.

There is one pipe segment in the Unit 3 HPCI System that due to unfavorable pipe slope could contain a void whose maximum cross section exceeds 20 percent of the pipe flow area. However, the average void cross section in this pipe segment could not exceed 20 percent of the pipe flow area. In addition, this pipe segment is located downstream of the HPCI injection isolation valve and is not susceptible to sudden compression. Based on this, the maximum possible void in this pipe segment does not result in unacceptable pressure pulsations or waterhammer. Even though the maximum possible void in this pipe segment is acceptable, it was inspected by UT and no voiding was identified.

Because some pipe segments in the discharge pipe were identified that have unfavorable pipe slope or pipe bow, operating procedures are being revised to require UT inspection or dynamic venting of some of these locations should this pipe be drained (see Item (8)).

In the HPCI discharge pipe, there is a short length of horizontal pipe in the steam tunnel that was not surveyed. The survey of this pipe was identified in El -7

references 2 and 3 as being deferred until the next refueling outage for each unit. Due to the configuration of this pipe, it cannot contain a void that exceeds acceptance criteria. Therefore, this pipe. is no longer required to be surveyed in upcoming refueling outages.

The discharge pipe from the Low Pressure ECCS Pumps has been surveyed to their normally closed, outside containment injection valves. As discussed in Item (2), voids in pipe downstream of these injection valves do not adversely affect system performance. The survey of this pipe was identified in references 2 and 3 as being deferred until the next refueling outage for each unit. Therefore, this pipe is no longer required to be surveyed in upcoming refueling outages.

7. Identify new vent valve locations, modifications to existing vent valves, or utilization of existing vent valves that resulted from the confirmatory walkdowns, and summarize the Corrective Actions, and the schedule for completion of the Corrective Actions.

The survey of ECCS and DHR System pipe did not identify the need for additional vent capability.

8. Discuss the results of the fill and vent activities and procedure reviews for each system. (Note that routine periodic surveillance testing is addressed in the "Testing Evaluation" section of this template).

The review of ECCS and DHR System operating procedures determined that these procedures provide adequate instructions for filling and venting the suction piping, the pump casing, discharge piping to the inboard injection valves (i.e.; the normally closed valve nearest the reactor vessel). The procedure review found that the Low Pressure Coolant Injection (LPCI) lines would be more completely vented by using a vent valve on the bonnet of the out board injection valve than by using the vent valve specified in the fill and vent procedure. Using the vent valve specified in the fill and vent procedure would not have left an unacceptable void in the LPCI lines; however, the procedure change is necessary to ensure that the lines are vented at the optimum high point.

BFN operating experience has been that these systems are adequately filled and vented after maintenance or modification and prior to being returned to service.

Nuclear industry operating experience has identified instances where the ECCS has not been adequately filled. Based on this, the ECCS and DHR System operating procedures are being revised to require UT inspection or dynamic venting of locations that could contain a significant void should this pipe be drained. These locations will include the discharge pipe high points, which ensure the filling of this pipe is complete. This procedure change adds an additional procedural barrier to prevent inadequate filling of a safety system and is an enhancement.

9. Identify procedure revisions, or new procedures resulting from the fill and vent activities and procedure reviews that need to be developed, and summarize the Corrective Actions, and schedule for completion of E1-8

the Corrective Actions. (Note that routine periodic surveillance testing is addressed in the "Testing Evaluation" section of this template).

The review determined that no changes to operating procedures (fill and vent) are required; however, as discussed in Item (8), above, several enhancements to operating procedures are being made through the Corrective Action Program.

10. Discuss potential gas intrusion mechanisms into each system for each piping segment that is vulnerable to gas intrusion.

All ECCS and DHR System suction pipe is at greater than atmospheric pressure during power operation. This positive pressure results in water leakage from any location that would pull air into the system should the suction pressure drop below atmospheric pressure during a DBA. There are no significant sources of gas in ECCS and DHR System suction or discharge pipe.

11. Ongoing Industry Programs Ongoing industry programs are planned in the following areas which may impact the conclusions reached during the Design Evaluation relative to gas accumulation. The activities will be monitored to determine if additional changes to the plant design may be required or desired to provide additional margin.

Gas Transport in Pump Suction Piping The Pressurized Water Reactor Owners Group (PWROG) has initiated testing to provide additional knowledge relative to gas transport in large diameter piping. One program performed testing of gas transport in 6-inch and 8-inch piping. Another program will perform additional testing of gas transport in 4-inch and 12-inch low temperature systems and 4-inch high temperature systems. This program will also integrate the results of the 4-inch, 6-inch, 8-inch and 12-inch testing.

Pump Acceptance Criteria Long-term industry tasks were identified that will provide additional tools to address GL-2008-01 with respect to pump gas void ingestion tolerance limits.

12. Provide a detailed list of items that have not been completed, a schedule for their completion, and the basis for that schedule.

This information is in Section B.

Testing Evaluation

1. Discuss the results of the periodic venting or gas accumulation surveillance procedure review.

There are test procedures for monthly discharge piping vents for the ECCS.

There are no Surveillance Procedures to vent suction piping other than operating procedures for fill and vent. There is also a procedure section in the E1-9

quarterly pump flow rate surveillances to vent discharge piping and verify discharge pipe is pressurized prior to operating the pump.

The monthly vent procedures have a "steady stream (flow) of water" as acceptance criteria. This has been acceptable because Surveillance Requirement (SR) 3.5.1.1 requires at least once per 31 days verify the ECCS piping is full of water by venting the ECCS Pump discharge piping high point vents.

To ensure all gas is removed during venting, the venting procedures require a steady stream (flow) of water to demonstrate that voids have been removed.

The venting procedures for HPCI and Core Spray discharge pipe require a steady stream of water for 4 minutes. The venting procedure for LPCI discharge pipe does not have a time specified for the steady stream of water from the vent. The venting procedures for LPCI discharge pipe are being revised to include a time requirement on water flow from the vent. This LPCI venting procedure change is an enhancement.

The test procedures for verifying Core Spray Pump flow require that the system be verified to be full of water prior to operating the pumps. This is accomplished by using either the operating procedure for fill and vent or by using the monthly vent procedure. The monthly vent procedure is considered the better procedure to be used for ensuring the discharge pipe is full.

Therefore, the Core Spray Pump flow test procedures are being revised to require only the monthly vent procedures to be used for verifying the system is full of water. This Core Spray Pump flow test procedure change is an enhancement.

2. Identify procedure revisions or new procedures resulting from the periodic venting or gas accumulation surveillance procedure review that need to be developed.

There is no documentation that contains information about the amount of gas released during past venting of the ECCS and DHR System. However, given the lack of gas sources in either the suction or discharge pipe it is expected that no significant gas releases have occurred during these monthly surveillances. The procedures that are used for meeting SR 3.5.1.1 are being revised to require that gas releases be timed and results trended. The revised venting procedures will also require that, in the event of an extended gas release, a report is entered into the Corrective Action Program. This procedure change is an enhancement to better identify and evaluate unexpected voiding.

3. Discuss how procedures adequately address the manual operation of the DHR System in its decay heat removal mode of operation. Include how the procedures assure that the DHR System is sufficiently full of water to perform its decay heat removal safety function (high point venting or UT) and how pump operation is monitored by plant personnel (including a description of the available instrumentation and alarms).

The DHR System suction pipe from the primary system is maintained full of water from the outboard containment isolation valve to the DHR System Pumps by a continuous makeup flow from a head tank. Once this pipe has been filled, the connection to the head tank ensures it remains full. There is a El-10

portion of the DHR System suction pipe from the primary system, inside containment that is not maintained full by the head tank. Due to the configuration of this pipe and its distance from the DHR System Pump suction, it cannot contain a void large enough to cause a loss of the DHR System Pumps when they take suction from the primary system. The DHR System Pumps have not become gas bound with their suctions' aligned to the primary system for shutdown cooling.

Operators have instrumentation to monitor the DHR System and procedures to mitigate a loss of the DHR System.

4. Summarize the results of the procedure reviews performed to determine that gas intrusion does not occur as a result of inadvertent draining due to valve manipulations specified in the procedures, system realignments, or incorrect maintenance procedures.

BFN operating experience is that testing, maintenance or system alignment changes do not result in inadvertent draining or the introduction of gas voids into the ECCS and DHR Systems.

5. Describe how gas voids are documented (including the detection method such as venting and measuring or UT and void sizing and post venting checks), dispositioned (including method(s) used such as static or dynamic venting), and trended, if found in any of the subject systems.

As discussed in Item (2), above, procedures that are used for meeting SR 3.5.1.1 are being revised to require that, for an extended gas release in the ECCS and DHR System, a report is entered into the Corrective Action Program.

6. Provide a detailed list of items that have not been completed, a schedule for their completion, and the basis for that schedule.

This information is in Section B.

Corrective Actions Evaluation

1. Summarize the results of the reviews regarding how gas accumulation has been addressed at your site.

BFN's Corrective Action Program is used to document gas intrusion /

accumulation issues as potential nonconforming conditions. As part of BFN's Corrective Action Program, Problem Evaluation Reports related to plant equipment are evaluated for potential impact on operability and reportability.

Therefore, BFN's review concluded that issues involving gas intrusion /

accumulation are properly prioritized and evaluated under the Corrective Action Program.

2. Provide a detailed list of items that have not been completed, a schedule for their completion, and the basis for that schedule.

This information is in Section B.

Conclusion El-11

Based upon the above, TVA has concluded that BFN is in conformance with 10 CFR 50, Appendix B, Criterion III, V, XI, XVI, and XVII, and any identified deviations have been entered into the BFN Corrective Action Program for tracking and final resolution, as described in Section B.

B. DESCRIPTION OF CORRECTIVE ACTIONS, SCHEDULE AND JUSTIFICATION FOR SCHEDULE The completed evaluations have determined that voiding is being maintained less than the amount that challenges the capability of the ECCS and DHR System to mitigate DBAs and maintain SSD. Based on these systems being fully capable of performing their safety functions, the schedule for completing the corrective actions is listed in Table 1:

TABLE 1 Item Description Date

1. TVA will evaluate adopting the revised Integrated Within 6 Standard Technical Specification (ISTS) SR 3.5.1.1 at months of BFN.

NRC approval of the Traveler

2. The design change review checklist is revised to Complete include an explicit item to determine if the design change introduces or increases the potential for gas accumulation beyond established acceptance criteria.

3. The procedure for venting the LPCI injection lines is Complete revised to use the vent valve on the bonnet of the LPCI injection isolation valve.

4. The ECCS and DHR System operating procedures are 11/26/2008 being revised to require UT inspection or dynamic venting of locations that could contain a significant void should this pipe be drained.

5. The venting procedures for LPCI discharge pipe are Complete revised to include a time requirement on water flow from the vent.

6. The Core Spray Pump flow test procedures are revised Complete to require the monthly vent procedures to be used for verifying the system is full of water prior to testing the pump.

7. The procedures that are used for meeting SR 3.5.1.1 1/31/2009 are being revised to require that gas releases be timed and results trended. The revised venting procedures will also require that, in the event of an extended gas release, a report is entered into the Corrective Action Program.

Items 2 through 7 have been entered into BFN's Corrective Action Program.

A Commitment for item 1 in the above Table is listed in Enclosure 4.

In addition, the Boiling Water Reactor (BWR)/PWROG is proceeding with various programs on the affect of voids on safety system performance. TVA will follow the BWR/PWROG Programs and take additional actions, if needed to ensure system operability, as the results of these programs becomes available.

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Revision to ISTS SR 3.5.1.1 may result in a requirement that quantitative void limits for some locations in the ECCS and DHR System are established and that void monitoring be implemented. A TS SR change of this scope would require additional plant specific calculations and plant modifications may be required to implement void monitoring. The time frame for evaluating the revised TS for adoption is left somewhat open at this time due to the recently developing NRC and industry efforts.

Conclusion TVA has evaluated the accessible portions of those BFN systems that perform the functions described in this GL and has concluded that these systems are Operable, as defined in the BFN TS and are in conformance to our commitments to the applicable General Design Criteria (GDC), as stated in the BFN UFSAR.

The open actions cited above are considered to be enhancements to the existing programs/processes/procedures for assuring continued Operability of these subject systems.

As committed in References 2 and 3, TVA will complete its evaluation of the inaccessible portions of these systems by startup from the next Refuel Outage at BFN and will provide a supplement to this response within 90 days thereafter.

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ENCLOSURE2 9-MONTH RESPONSE TO NRC GENERIC LETTER (GL) 2008-01 REQUESTED INFORMATION FOR SEQUOYAH NUCLEAR PLANT (SQN)

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This Enclosure contains the SQN 9-Month Response to NRC Generic Letter (GL) 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems, dated January 11, 2008. In GL 2008-01, the NRC requested "that each addressee evaluate its ECCS, DHR system, and containment spray system licensing basis, design, testing, and corrective actions 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."

The following information is provided in this response:

a) A description of the results of evaluations that were performed pursuant to the requested actions in the GL (see Section A of this Enclosure),

b) A description of all corrective actions determined necessary to assure compliance with the quality assurance criteria in Sections III, V, XI, XVI, and XVII of Appendix B to 10 CFR Part 50 and the licensing basis and operating license with respect to the systems identified in the GL (see Section B of this Enclosure), and c) A statement regarding which corrective actions were completed by October 11, 2008, the schedule for completing the corrective actions not completed by October 11, 2008, and the basis for that schedule (see Section C of this Enclosure).

The following systems were determined to be in the scope of GL 2008-01 for SQN:

Emergency Core Cooling System Decay Heat Removal System Containment Spray Systems (SQN has the capability to provide containment spray from both the Containment Spray System and the DHR System)

A. EVALUATION RESULTS Licensinq Basis Evaluation The SQN licensing basis was reviewed with respect to gas accumulation in the Emergency Core Cooling, Decay Heat Removal System and Containment Spray System. This review included the Technical Specifications (TS), TS Bases, Updated Final Safety Analysis Report (UFSAR), the Technical Requirements Manual (TRM) and TRM Bases, responses to NRC Generic Communications, Regulatory Commitments, and License Conditions.

1. Summarize the results of the review of these documents:

The above documents and regulatory commitments were evaluated for compliance with applicable regulatory requirements. This review determined that the licensing basis for the ECCS, DHR System and Containment Spray System is that voiding in these systems is maintained at a level that does not significantly affect their performance when mitigating Design Basis Accidents (DBAs) or while maintaining Safe Shutdown (SSD). Therefore, to be in compliance with the licensing basis for SQN, voiding in these systems must be maintained at a level that does not significantly affect the performance of these systems when mitigating DBAs or maintaining SSD.

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2. Summarize the changes to licensing basis documents (Corrective Actions):

SQN has not made any changes to licensing basis documents as a result of this GL response.

3. Provide a detailed list of items that have not been completed, a schedule for their completion, and the basis for that schedule.

TS improvements are being addressed by the Technical Specifications Task Force (TSTF) to provide an approved TSTF Traveler for making changes to individual licensee's TS related to the potential for unacceptable gas accumulation. The development of the TSTF Traveler relies on the results of the evaluations of a large number of licensees to address the various plant designs. TVA is continuing to support the industry and Nuclear Energy Institute (NEI) Gas Accumulation Management Team activities regarding the resolution of Generic TS changes via the TSTF Traveler process. After NRC approval of the Traveler, TVA will evaluate its applicability to the SQN, and evaluate adopting the Traveler to either supplement or replace the current TS requirements.

Design Evaluation The SQN design basis was reviewed with respect to gas accumulation in the Emergency Core Cooling and Decay Heat Removal Systems. This review included Design Basis Documents, Calculations, Engineering Evaluations, and Vendor Technical Manuals.

1. Discuss the results of the review of the design basis documents. This discussion should include a description of any plant specific calculations or analyses that were performed to confirm the acceptability of gas accumulation in the piping of the affected systems, including any acceptance criteria if applicable. Note: This should describe the "as found" (pre Generic Letter) condition prior to any corrective or enhancement actions.

This review determined that the ECCS, DHR System and Containment Spray System design includes features that ensure pumps, pipe and components are maintained full of water. These features include:

The pumps are located below their suction sources with no inverted U-turns in the suction pipe.

The level in the suction sources is monitored and minimum water levels have been established to ensure that unacceptable air ingestion does not occur during a DBA.

The level instrumentation on suction sources is sloped to ensure it can be filled and vented.

Suction pipe is at greater than atmospheric pressure during power operation.

There are no significant sources of gas in suction pipe from the refueling water storage tank or from the containment sump.

Periodic pump tests and/or normal system operation have a flow rate sufficient to sweep voids through most of their suction pipe.

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In addition, there are no component void traps in the suction pipe that would result in a significant void being transported in whole to the pump suction.

Review of the Design Control Program determined that the design change review checklist should have an explicit item to determine if the design change introduces or increases the potential for gas accumulation beyond established acceptance criteria. This adds an additional procedural barrier to prevent unintended consequences from plant changes and is an enhancement to the Design Control Program.

2. Discuss new applicable gas volume acceptance criteria for each piping segment in each system where gas can accumulate where no acceptance criteria previously existed and summarize the Corrective Actions, and schedule for completion of any Corrective Actions.

a) Pump Suction Piping The interim allowable gas accumulation in the pump suction piping is based on limiting the gas entrainment to the pump after a pump start. A PWROG Program established interim pump gas ingestion limits to be employed by the member utilities. The interim criteria address pump mechanical integrity only and are as follows:

Single-Stage Multi-Stage Multi-Stage Stiff Shaft Flexible Shaft Steady-State 2 percent 2 percent 2 percent Transient*

5 percent for 20 percent for 10 percent for 20 seconds 20 seconds 5 seconds QB.E.P. Range 70 percent to 70 percent to 70 percent to 120 percent 140 percent 120 percent Pump Type WDF CA RLIJ, JHF (transient data),

• The transient criteria are based on pump test data and vendor supplied information.

b) Pump discharge piping which is susceptible to pressure pulsation after a pump start Pump discharge void volume acceptance criteria was based on maintaining pressure pulsations less than that which would cause a discharge pipe relief valve to lift or result in a hydraulic force that causes pipe stress to exceed allowable values. In order to meet these criteria, there must be no sudden changes in flow as the ECCS and DHR System pumps start and compresses voids in the discharge pipe. These criteria are usually met when the discharge pipe has been filled to the isolation valve as this prevents an abrupt stopping of flow. In an otherwise full pipe system, voids due to unfavorable pipe slope and bow in nominally horizontal pipe or trapped due to flow obstructions (e.g., orifice plates) are gradually compressed and do not result in an unacceptable pressure transient during pump start.

c) Pump discharge piping which is not susceptible to water hammer or pressure pulsation following a pump start E2-4

1. The PWROG methodology for Containment Spray evaluates the piping response as the Containment Spray header is filled and compares the potential force imbalances with the weightof the piping. The net force resulting from the pressurization of the Containment Spray header during the filling transient is a small fraction of the dead weight of the filled piping, and therefore the filling transient is well within the margin of the pipe hangers.

The design basis of SQN includes a detailed calculation of the force imbalances during the filling of the Containment Spray discharge headers that shows the resultant force imbalances to be within the margin of the pipe hangers.

2. A PWROG methodology has been developed to assess when a significant gas-water waterhammer could occur during switchover to hot leg injection. The methodology concludes that: If the upstream valve has an opening time of approximately 10 seconds and the downstream path to the Reactor Coolant System (RCS) is only restricted by check valve(s), no significant waterhammer would occur, i.e.; none of the relief valves in the subject systems would lift, or none of the piping restraints would be damaged.

The SQN ECCS flow path for hot leg injection from the DHR System Pumps has an upstream valve that has an opening time greater than 10 seconds and the downstream path to the RCS is only restricted by check valves. Therefore, consistent with the PWROG Program methodology, no significant waterhammer will occur, i.e.; none of the relief valves in the subject systems would lift, or none of the piping restraints would be damaged.

The ECCS, Safety Injection System Pumps (SIPs) are aligned for hot leg injection by stopping the SIPs, closing the Cold Leg Injection (CLI) valves and opening the hot leg injection valves prior to restarting the SIPs. In addition, there are flow restricting orifices in each hot leg injection line. While this configuration was not explicitly evaluated in the PWROG methodology, the fact that the primary system is depressurized and flow to the hot legs does not stop after the SIPs are restarted, ensures no significant waterhammer will occur, i.e.; none of the relief valves in the subject systems would lift, or none of the piping restraints would be damaged.

d) Primary System Allowable Gas Ingestion The PWROG qualitatively evaluated the impact of non-condensable gases entering the RCS on the ability on the post-accident core cooling functions of the RCS. This evaluation assumed that 5 cubic feet of non-condensable gas at 400 psig was present in the High Head Safety Injection (HHSI) and Intermediate Head Safety Injection (IHSI) discharge piping concurrent with 5 cubic feet of non-condensable gas at 100 psig in the Low Head Safety Injection (LHSI) discharge piping. The qualitative evaluation concluded that these quantities of gas that will not prevent the ECCS from performing its core cooling function.

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The quantity of gas determined to be acceptable based on the above described limits is very large. For example, should the entire ECCS be initially filled and vented, the above evaluated gas quantities total more than 50 cubic feet of voided pipe and components.

In summary, the effect on the ECCS core cooling function of non-condensable gas entering the primary system was assessed and found not to be limiting with respect to allowable void size.

3. Summarize the changes, if any, to the design basis documents (Corrective Actions) and the schedule for completion of the Corrective Actions.

The review determined that no changes to design basis documents are required. However, as discussed in Item (1), an enhancement is being made to the design change review checklist through the Corrective Action Program.

4. Discuss the results of the system P&ID and isometric drawing reviews to identify all system vents and high points. ?

The ECCS, DHR System and Containment Spray System mechanical flow diagrams, physical pipe drawings and isometric drawings were reviewed. The pipe configuration in these systems is relatively simple so the physical pipe drawings and isometrics were used to evaluate each pipe segment. These, systems were designed to be filled by gravity feed from their water sources.

The review identified some pipe segments in the ECCS, DHR System and Containment Spray System that can trap relatively small voids. However, vents are located such that all) significant voids can be removed by gravity fill from the systems water sources. Operating experience has also not identified any adverse consequences of voiding in these pipe segments. The drawing review determined that in the absence of significant adverse pipe slope or pipe bow in nominally horizontal pipe, these systems have sufficient vent valves at the proper locations to allow for filling of pipes and components. As discussed in Item (6), nominally horizontal pipe in the Auxiliary Building that was accessible has been surveyed to identify adverse pipe slope or pipe bow.

5. Identify new vent valve locations, modifications to existing vent valves, or utilization of existing vent valves based on the drawing review, and summarize the Corrective Actions, and schedule for completion of the Corrective Actions.

The drawing review did not identify the need for additional vent valves.

However, additional vent valves are being considered for some locations to enhance venting capabilities.

6. Discuss the results (including the scope and acceptance criteria used) of the system confirmation walkdowns that have been completed for the portions of the systems that require venting to ensure that they are sufficiently full of water.

Discharge Pipe:

The survey of the ECCS, DHR System and Containment Spray System discharge pipe outside containment determined that there are not any E2-6

locations that could contain a void that exceeds acceptance criteria. In general, the maximum possible void cross section in the pipe segments in the Auxiliary Building is well below 20 percent of the pipe flow area. However, the average void cross section in'these pipe segments in the Auxiliary Building could not exceed 20 percent of the pipe flow area and the maximum possible total void volume is relatively small. Based on this, the maximum possible void in these pipe segments would not result-in unacceptable pressure pulsations or waterhammer. Because some pipe segments in the discharge pipe were identified that have unfavorable pipe slope or pipe bow, operating procedures are being revised to require UT inspection or dynamic venting of some of these locations should this piping be drained (see Item (8)).

The majority of the ECCS, DHR System and Containment Spray System discharge pipe is located inside containment and has not been surveyed to identify unfavorable pipe slope or bow in nominally horizontal discharge pipe that could trap voids. The survey of ECCS, DHR System and Containment Spray System discharge pipe inside containment was identified in reference 2 as being deferred until the next refueling outage for each Unit.

As discussed in Item (2), the containment spray system pipe inside containment and the Hot Leg Injection (HLI) pipe inside containment are not subject to significant waterhammer. In addition, the Cold Leg Injection (CLI) pipe from the Centrifugal Charging Pumps (CCPs) is also not subject to significant waterhammer. Therefore, this pipe is no longer required to be surveyed in upcoming refueling outages.

There are a few pipe segments in the ECCS discharge pipe and the Containment Spray System discharge pipe that were not surveyed due to the need to remove lead shielding and / or erect scaffolding to access the pipe.

The survey of pipe segments that meet these criteria was identified in reference 2 as being deferred until the next refueling outage for each Unit.

These pipe segments have been conservatively assessed by assuming that the void height is one inch in the entire length of the pipe segment. The results of the pipe survey have demonstrated that this amount of voiding is bounding.

Suction Pipe:

The ECCS and DHR System Pumps are tested at full flow during each refueling outage. These full flow tests result in a flow rate that transports voids in portions of their suction and discharge pipe to the primary system.

The Containment Spray System Pumps are periodically tested at a flow rate that transports voids in their suction pipe and part of their discharge pipe to the refueling water storage tank. Although not necessary to ensure all accessible pipe segments in the ECCS, DHR System and Containment Spray System suction pipe do not contain voids, all this piping was surveyed for unfavorable pipe slope or pipe bow.

The survey of the ECCS, DHR System and Containment Spray System suction pipe identified one pipe segment in the Unit 2 refueling water storage tank (RWST) supply to one of the Safety Injection Pumps and one pipe segment in the Unit 2 Residual Heat Removal Pumps (RHRPs) supply to the Centrifugal Charging Pumps (CCPs) that due to unfavorable pipe slope or pipe bow could contain a void whose maximum cross section exceeds 10 E2-7

percent of the pipe flow area. However, the average void cross section in these pipe segments could not exceed 10 percent of the pipe flow area and the total void volume is relatively small. Based on this, there are not any pipe segments in this suction pipe that could contain a void that would result in a void fraction at the pump in excess of its acceptance criteria.

Even though the maximum possible void in these pipe segments is acceptable, they were inspected by UT and no voiding was identified.

Because some pipe segments in the suction pipe were identified that have unfavorable pipe slope or pipe bow, operating procedures are being revised to require UT inspection or dynamic venting of some of these locations should this pipe be drained (see Item (8)).

A portion of the DHR System suction pipe from the primary system is located inside containment. The survey of this pipe was identified in reference 2 as being deferred until the next refueling outage for each unit. Procedures require venting of this suction pipe just prior to it being placed in service for shutdown cooling. In addition, the configuration of this pipe and its horizontal and vertical distance from the DHR Pump suction ensures that it cannot contain a void that would result in gas binding of the pumps. The DHR System Pumps have not become gas bound with their suctions' aligned to the primary system for shutdown cooling. Therefore, this pipe is no longer required to be surveyed in upcoming refueling outages.

7. Identify new vent valve locations, modifications to existing vent valves, or utilization of existing vent valves that resulted from the confirmatory walkdowns, and summarize the Corrective Actions, and the schedule for completion of the Corrective Actions.

The survey of ECCS, DHR System and Containment Spray System pipe did not identify the need for additional vent capability. However, additional vent valves are being considered for some locations to enhance venting capabilities.

8. Discuss the results of the fill and vent activities and procedure reviews for each system. (Note that routine periodic surveillance testing is addressed in the "Testing Evaluation" section of this template).

The review of ECCS, DHR System and Containment Spray System operating procedures determined that these procedures provide detailed instructions for filling and venting the suction piping, the pump casing and discharge piping.

SQN have made many plant and procedure changes since initial licensing to ensure the ECCS, DHR System and Containment Spray Systems are adequately filled. Recent operating experience has been that these systems are adequately filled and vented after maintenance or modification and prior to being returned to service.

Nuclear industry operating experience has identified instances where the ECCS has not been adequately filled. Based on this, the ECCS, DHR System and Containment Spray System operating procedures are being revised to require UT inspection or dynamic venting of locations that could contain a significant void should this pipe be drained. These locations will include the discharge pipe high points, which ensure the filling of this pipe is complete.

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This procedure change adds an additional procedural barrier to prevent inadequate filling of a safety system and is an enhancement.

9. Identify procedure revisions, or new procedures resulting from the fill and vent activities and procedure reviews that need to be developed, and summarize the Corrective Actions, and schedule for completion of the Corrective Actions. (Note that routine periodic surveillance testing is addressed in the "Testing Evaluation" section of this template).

The review determined that no changes to operating procedures (fill and vent) are required; however, as discussed in Item (8), above, an enhancement to operating procedures is being made through the Corrective Action Program to provide additional actions and checks to ensure the ECCS, DHR System and Containment Spray System pipe is full of water prior to these systems being returned to a status of TS operable.

10. Discuss potential gas intrusion mechanisms into each system for each piping segment that is vulnerable to gas intrusion.

All ECCS, DHR System and Containment Spray System suction pipe is at greater than atmospheric pressure during power operation. This positive pressure results in water leakage from any location that would pull air into the system should the suction pipe pressure drop below atmospheric pressure during a DBA.

There are no significant sources of gas in ECCS, DHR System and Containment Spray System suction pipe, except for the water that circulates through the Centrifugal Charging Pumps (CCPs). These pumps circulate reactor coolant that contains hydrogen and noble gases that can come out of solution and form voids in the suction pipe. At SQN, locations that due to pipe configuration trap voids are inspected by UT each month and vented as needed; the amount of voiding at these locations has not been sufficient to significantly adversely affect performance of the CCPs.

Voids can form in the CLI lines due to primary system and Cold Leg Accumulator (CLA) leakage. Primary system and CLA leakage is monitored and trended. In addition, SQN operating experience is that this leakage results in pressurization of the ECCS discharge pipe. These indicators would be used to assess the need for an increase in the frequency of ECCS discharge pipe venting (through the Corrective Action Program).

The Safety Injection Pumps (SIPs) and Residual Heat Removal Pumps (RHRPs) are the intermediate head and low head ECCS Pumps, respectively.

These pumps are aligned to their CLI lines during power operation. These pumps are individually tested each quarter in a configuration that results in the compression of any voids in their CLI lines. Recent operating experience from these quarterly tests has shown that unacceptable pressure pulsations or hydraulic forces do not occur when these pumps are started. This is the basis for the conclusion that a successful quarterly test of the SIPs and RHRPs (i.e.;

no waterhammer) provides verification that voids in the SIP and RHRP discharge pipe are below that which significantly affect their safety functions.

11. Ongoing Industry Programs E2-9

Ongoing industry programs are planned in the following areas which may impact the conclusions reached during the Design Evaluation relative to gas accumulation. The activities will be monitored to determine if additional changes to the plant design may be required or desired to provide additional margin.

0 Gas Transport in Pump Suction Piping The PWROG has initiated testing to provide additional knowledge relative to gas transport in large diameter piping. One program performed testing of gas transport in 6-inch and 8-inch piping. Another program will perform additional testing of gas transport in 4-inch and 12-inch low temperature systems and 4-inch high temperature systems. This program will also integrate the results of the 4-inch, 6-inch, 8-inch and 12-inch testing.

Pump Acceptance Criteria Long-term industry tasks were identified that will provide additional tools to address GL-2008-01 with respect to pump gas void ingestion tolerance limits.

12. Provide a detailed list of items that have not been completed, a schedule for their completion, and the basis for that schedule.

This information is in Section B.

Testing Evaluation

1. Discuss the results of the periodic venting or gas accumulation surveillance procedure review.

SQN has procedures for the venting of the ECCS. This venting is done to meet Surveillance Requirement (SR) 4.5.2.b.1. Vent valves at the high points on the discharge pipe of the ECCS are opened each month and any gas discharge is timed and trended. Operating experience from periodic venting of these high points indicates that the ECCS discharge pipe is maintained full of water. There have been no incidents where any of these systems were found in a voided condition that would have prevented them from performing their safety functions.

2. Identify procedure revisions, or new procedures resulting from the periodic venting or gas accumulation surveillance procedure review that need to be developed, and summarize the Corrective Actions, and schedule for completion of the Corrective Actions. For example, new or revised procedure(s) were implemented for additional leak testing or periodic maintenance to demonstrate the leak tightness of valves in potential gas intrusion paths.

The procedures that are used to meet SR 4.5.2.b.1 are being revised to require that, in the event of an extended gas release, a report is entered into the Corrective Action Program.

3. Discuss how procedures adequately address the manual operation of the DHR System in its decay heat removal mode of operation. Include how the procedures assure that the DHR System is sufficiently full of E2-10

water to perform its decay heat removal safety function (high point venting or UT) and how pump operation is monitored by plant personnel (including a description of the available instrumentation and alarms).

Procedures require venting of the suction and discharge pipe in the DHR System, just prior to it being placed in service for shutdown cooling. When placed in service for shutdown cooling, the isolation valves in the suction pipe are opened and the DHR System pressurizes to primary system pressure prior to starting the DHR System Pumps. Any pre-existing voids in the system are compressed to roughly 1/10 of their original size. The DHR System would need to be greatly voided in standby to contain a significant void once pressurized for shutdown operation. The DHR System Pumps have not become gas bound with their suctions' aligned to the primary system for shutdown cooling.

Operators have instrumentation to monitor the DHR System and procedures to mitigate a loss of the DHR System.

4. Summarize the results of the procedure reviews performed to determine that gas intrusion does not occur as a result of inadvertent draining due to valve manipulations specified in the procedures, system realignments, or incorrect maintenance procedures.

Based on recent operating experience testing, maintenance and system alignment changes do not result in inadvertent draining or the introduction of voids into the ECCS, DHR System or Containment Spray System. SQN has experienced voids in the past; procedure revision and addition of vent valves have corrected the previous events.

5. Describe how gas voids are documented (including the detection method such as venting and measuring or UT and void sizing and post venting checks), dispositioned (including method(s) used such as static or dynamic venting), and trended, if found in any of the subject systems.

As discussed in Item (2), above, procedures that are used for meeting SR 4.5.2.b.1 are being revised to require that, for an extended gas release in the ECCS and DHR System, a report is entered into the Corrective Action Program.

6. Provide a detailed list of items that have not been completed, a schedule for their completion, and the basis for that schedule.

This information is in Section B.

Corrective Actions Evaluation

1. Summarize the results of the reviews regarding how gas accumulation has been addressed at your site.

SQN's Corrective Action Program is used to document gas intrusion /

accumulation issues as potential nonconforming conditions. As part of this Corrective Action Program, Problem Evaluation Reports related to plant equipment are evaluated for potential impact on operability and reportability.

Therefore, SQN's review concluded that issues involving gas intrusion /

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accumulation are properly prioritized and evaluated under the Corrective Action Program.

2. Provide a detailed list of items that have not been completed, a schedule for their completion, and the basis for that schedule.

This information is in Section B.

Conclusion Based upon the above, TVA has concluded that SQN is in conformance with 10 CFR 50, Appendix B, Criterion Ill, V, XI, XVI, and XVII, and any identified deviations have been entered into the SQN Corrective Action Program for tracking and final resolution, as described in Section B.

B. DESCRIPTION OF CORRECTIVE ACTIONS, SCHEDULE AND JUSTIFICATION FOR SCHEDULE The completed evaluations have determined that voiding is being maintained less than the amount that challenges the capability of the ECCS, DHR System and Containment Spray System to mitigate DBAs and maintain SSD. Based on these systems being fully capable of performing their safety functions, the schedule for completing the corrective actions is listed in Table 2:

TABLE 2 Item Description Date

1. TVA will evaluate adopting the revised Integrated Within 6 Standard Technical Specifications (ISTS) SR 3.5.2.3 months of (NUREG 1431) at SQN.

NRC approval of the Traveler

2. The design change review checklist is revised to include Complete an explicit item to determine if the design change introduces or increases the potential for gas accumulation beyond established acceptance criteria.

3. The ECCS, DHR System and Containment Spray 1/31/2009 System operating procedures are being revised to require UT inspection or dynamic venting of locations that could contain a significant void should this pipe be drained.

4. Periodic venting procedures used to meet SR 4.5.2.b.1 1/31/2009 are being revised to require that, for an extended gas release, a report is entered into the Corrective Action Program.

Items 2 through 4 have been entered into SQN's Corrective Action Program.

A Commitment for item 1 in the above Table is listed in Enclosure 4.

In addition, the BWR/PWROG is proceeding with various programs on the affect of voids on safety system performance. TVA will follow the BWR/PWROG programs and take additional actions, if needed to ensure system operability, as the results of these programs becomes available.

Revision to ISTS SR 3.5.2.3 (NUREG 1431) may result in a requirement that quantitative void limits for some locations in the ECCS and DHR System are E2-12

established and that void monitoring be implemented. A TS SR change of this scope would require additional plant specific calculations and plant modifications may be required to implement void monitoring. The time frame for evaluating the revised TS for adoption is left somewhat open at this time due to the recently developing NRC and industry efforts.

Conclusion TVA has evaluated the accessible portions of those SQN systems that perform the functions described in this GL and has concluded that these systems are Operable, as defined in their TS and are in conformance to commitments to the applicable General Design Criteria (GDC), as stated in the SQN UFSAR.

The open actions cited above are considered to be enhancements to the existing programs/processes/procedures for assuring continued Operability of these subject systems.

As committed in Reference 2, TVA will complete its evaluation of the inaccessible portions of these systems by startup from the next Refuel Outage at SQN for each unit and will provide a supplement to this response within 90 days thereafter.

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ENCLOSURE3 9-MONTH RESPONSE TO NRC GENERIC LETTER (GL) 2008-01 REQUESTED INFORMATION FOR WATTS BAR NUCLEAR PLANT (WBN)

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This Enclosure contains the WBN 9-Month Response to NRC Generic Letter (GL) 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems, dated January 11, 2008. In GL 2008-01, the NRC requested "that each addressee evaluate its ECCS, DHR system, and containment spray system licensing basis, design, testing, and corrective actions 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."

The following information is provided in this response:

a) A description of the results of evaluations that were performed pursuant to the requested actions in the GL (see Section A of this Enclosure),

b) A description of all corrective actions determined necessary to assure compliance with the quality assurance criteria in Sections Il, V, XI, XVI, and XVII of Appendix B to 10 CFR Part 50 and the licensing basis and operating license with respect to the systems identified in the GL (see Section B of this Enclosure),

and c) A statement regarding which corrective actions were completed by October 11, 2008, the schedule for completing the corrective actions not completed by October 11, 2008, and the basis for that schedule (see Section B).

The following systems were determined to be in the scope of GL 2008-01 for WBN:

Emergency Core Cooling System Decay Heat Removal System Containment Spray Systems (WBN has the capability to provide containment spray from both the Containment Spray System and the DHR System)

A. EVALUATION RESULTS Licensing Basis Evaluation The WBN licensing basis was reviewed with respect to gas accumulation in the Emergency Core Cooling, Decay Heat Removal System and Containment Spray System. This review included the Technical Specifications (TS), TS Bases, Updated Final Safety Analysis Report (UFSAR), the Technical Requirements Manual (TRM) and TRM Bases, responses to NRC Generic Communications, Regulatory Commitments, and License Conditions.

1. Summarize the results of the review of these documents:

The above documents and regulatory commitments were evaluated for compliance with applicable regulatory requirements. This review determined that the licensing basis for the ECCS, DHR System and Containment Spray System is that voiding in these systems is maintained at a level that does not significantly affect their performance when mitigating design basis accidents (DBAs) or while maintaining Safe Shutdown (SSD). Therefore, to be in compliance with the licensing basis for WBN, voiding in these systems must be maintained at a level E3-2

0 that does not significantly affect the performance of these systems when mitigating DBAs or maintaining SSD.

2. Summarize the changes to licensing basis documents (Corrective Actions):

WBN has not made any changes to licensing basis documents as a result of this GL response.

3. Provide a detailed list of items that have not been completed, a schedule for their completion, and the basis for that schedule.

TS improvements are being addressed by the Technical Specifications Task Force (TSTF) to provide an approved TSTF Traveler for making changes to individual licensee's TS related to the potential for unacceptable gas accumulation. The development of the TSTF Traveler relies on the results of the evaluations of a large number of licensees to address the various plant designs.

TVA is continuing to support the industry and Nuclear Energy Institute (NEI) Gas Accumulation Management Team activities regarding the resolution of Generic TS changes via the TSTF Traveler process. After NRC approval of the Traveler, TVA will evaluate its applicability to the WBN, and evaluate adopting the Traveler to either supplement or replace the current TS requirements.

Design Evaluation The WBN design basis was reviewed with respect to gas accumulation in the Emergency Core Cooling, Decay Heat Removal and Containment Spray Systems.

This review included Design Basis Documents, Calculations, Engineering Evaluations, and Vendor Technical Manuals.

1. Discuss the results of the review of the design basis documents. This discussion should include a description of any plant specific calculations or analyses that were performed to confirm the acceptability of gas accumulation in the piping of the affected systems, including any acceptance criteria if applicable. Note: This should describe the "as found" (pre Generic Letter) condition prior to any corrective or enhancement actions.

This review determined that the ECCS, DHR System and Containment Spray System design includes features that ensure pumps, pipe and components are maintained full of water. These features include:

The pumps are located below their suction sources with no inverted U-turns in the suction pipe.

The level in the suction sources is monitored and minimum water levels have been established to ensure that unacceptable air ingestion does not occur during a DBA.

The level instrumentation on suction sources is sloped to ensure it can be filled and vented.

Suction pipe is at greater than atmospheric pressure during power operation.

There are no significant sources of gas in suction pipe from the refueling water storage tank or from the containment sump.

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Periodic pump tests and/or normal system operation have a flow rate sufficient to sweep voids through most the suction pipe.

In addition, there are no component void traps in the suction pipe that would result in a significant void being transported in whole to the pump suction.

Review of the Design Control Program determined that the design change review checklist should have an explicit item to determine if the design change introduces or increases the potential for gas accumulation beyond established acceptance criteria.

This adds an additional procedural barrier to prevent unintended consequences from plant changes and is an enhancement to the Design Control Program.

2. Discuss new applicable gas volume acceptance criteria for each piping segment in each system where gas can accumulate where no acceptance criteria previously existed and summarize the Corrective Actions, and schedule for completion of any Corrective Actions.

a) Pump Suction Piping The interim allowable gas accumulation in the pump suction piping is based on limiting the gas entrainment to the pump after a pump start. A PWROG Program established interim pump gas ingestion limits to be employed by the member utilities. The interim criteria address pump mechanical integrity only and are as follows:

Single-Stage Multi-Stage Multi-Stage Stiff Shaft Flexible Shaft Steady-State 2 percent 2 percent 2 percent Transient*

5 percent for 20 percent for 10 percent for 20 seconds 20 seconds 5 seconds QB.E.P. Range 70 percent to 70 percent to 70 percent to 120 percent 140 percent 120 percent Pump Type WDF CA RLIJ, JHF (transient data)

• The transient criteria are based on pump test data and vendor supplied information.

b) Pump discharge piping which is susceptible to pressure pulsation after a pump start Pump discharge void volume acceptance criteria was based on maintaining pressure pulsations less than that which would cause a discharge pipe relief valve to lift or result in a hydraulic force that causes pipe stress to exceed allowable values. In order to meet these criteria, there must be no sudden changes in flow as the ECCS and DHR System Pumps start and compresses voids in the discharge pipe. These criteria are usually met when the discharge pipe has been filled to the isolation valve as this prevents an abrupt stopping of flow. In an otherwise full pipe system, voids due to unfavorable pipe slope and bow or trapped due to flow obstructions (e.g., orifice plates) are gradually compressed and do not result in an unacceptable pressure transient during pump start.

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c) Pump discharge piping which is not susceptible to water hammer or pressure pulsation following a pump start

1. The PWROG methodology for Containment Spray evaluates the piping response as the Containment Spray Header is filled and compares the potential force imbalances with the weight of the piping. The net force resulting from the pressurization of the Containment Spray Header during the filling transient is a small fraction of the dead weight of the filled piping, and therefore the filling transient is well within the margin of the pipe hangers.

The design basis of WBN includes a detailed calculation of the force imbalances during the filling of the Containment Spray discharge headers that shows the resultant force imbalances to be within the margin of the pipe hangers.

2. A PWROG methodology has been developed to assess when a significant gas-water waterhammer could occur during switchover to hot leg injection. The methodology concludes: If the upstream valve has an opening time of approximately 10 seconds and the downstream path to the Reactor Coolant System (RCS) is only restricted by check valve(s);

no significant waterhammer would occur, i.e.; none of the relief valves in the subject systems would lift, or none of the piping restraints would be damaged.

The WBN ECCS flow path for hot leg injection from the DHR System Pumps has an upstream valve that has an opening time greater than 10 seconds and the downstream path to the RCS is only restricted by check valves. Therefore, consistent with the PWROG Program methodology, no significant waterhammer will occur, i.e.; none of the relief valves in the subject systems would lift, or none of the piping restraints would be damaged.

The ECCS, Safety Injection System Pumps (SIPs) are aligned for hot leg injection by stopping the SIPs, closing the Cold Leg Injection (CLI) valves and opening the hot leg injection valves prior to restarting the SIPs. In addition, there are flow restricting orifices in each hot leg injection line.

While this configuration was not explicitly evaluated in the PWROG methodology, the fact that the primary system is depressurized and flow to the hot legs does not stop after SIPs are restarted, ensures no significant waterhammer will occur, i.e.; none of the relief valves in the subject systems would lift, or none of the piping restraints would be damaged.

d) Primary System Allowable Gas Ingestion The PWROG qualitatively evaluated the impact of non-condensable gases entering the RCS on the ability on the post-accident core cooling functions of the RCS. This evaluation assumed that 5 cubic feet of non-condensable gas at 400 psig was present in the HHSI and IHSI discharge piping concurrent E3-5

with 5 cubic feet of non-condensable gas at 100 psig in the LHSI discharge piping. The qualitative evaluation concluded that these quantities of gas will not prevent the ECCS from performing its core cooling function.

The quantity of gas determined to be acceptable based on the above described limits is very large. For example, should the entire ECCS be initially filled and vented, the above evaluated gas quantities total more than 50 cubic feet of voided pipe and components.

In summary, the effect on the ECCS core cooling function of non-condensable gas entering the primary system was assessed and found not to be limiting with respect to allowable void size.

3. Summarize the changes, if any, to the design basis documents (Corrective Actions) and the schedule for completion of the Corrective Actions.

The review determined that no changes to design basis documents are required.

However, as discussed in Item (1), an enhancement is being made to the design change review checklist through the Corrective Action Program.

4. Discuss the results of the system P&ID and isometric drawing reviews to identify all system vents and high points.

The ECCS, DHR System and Containment Spray System mechanical flow diagrams, physical pipe drawings and isometric drawings were reviewed. The pipe configuration in these systems is relatively simple so the'physical pipe drawings and isometrics were used to evaluate each pipe segment. Most piping in these systems was designed to be filled by gravity feed from their water sources. The review identified some pipe segments in the ECCS, DHR System and Containment Spray System that can trap relatively small voids. However, vents are located such that all significant voids can be removed by gravity fill from the systems water sources. Operating experience has also not identified any adverse consequences of voiding in these pipe segments. The drawing review determined that in the absence of significant adverse pipe slope or pipe bow in nominally horizontal pipe, these systems have sufficient vent valves at the proper locations to allow for filling of pipes and components. As discussed in Item (6), nominally horizontal piping in the Auxiliary Building that was accessible has been surveyed to identify adverse pipe slope or pipe bow.

5. Identify new vent valve locations, modifications to existing vent valves, or utilization of existing vent valves based on the drawing review, and summarize the Corrective Actions, and schedule for completion of the Corrective Actions.

The drawing review did not identify the need for additional vent valves. However, additional vent valves are being considered for some locations to enhance venting capabilities.

6. Discuss the results (including the scope and acceptance criteria used) of the system confirmation walkdowns that have been completed for the E3-6

portions of the systems that require venting to ensure that they are sufficiently full of water.

Discharge Pipe:

The survey of the ECCS, DHR System and Containment Spray System discharge pipe outside containment determined that there are not any locations that could contain a void that exceeds acceptance criteria. In general, the maximum possible void cross section in the pipe segments in the Auxiliary Building is well below 20 percent of the pipe flow area. In a few small bore pipe segments, the maximum possible void cross section exceeds 20 percent of the flow area; however, the maximum possible void volume in these pipe segments is less than 0.25 cubic feet.

The majority of the ECCS, DHR System and Containment Spray System discharge pipe is located inside containment and has not been surveyed to identify unfavorable pipe slope or bow in nominally horizontal discharge pipe that could trap voids. The survey of ECCS, DHR System and Containment Spray System discharge pipe inside containment was identified in reference 2 as being deferred until the next refueling outage.

As discussed in Item (2), the containment spray system pipe inside containment and the HLI pipe inside containment are not subject to significant waterhammer.

In addition, the Cold Leg Injection (CLI) pipe from the Centrifugal Charging Pumps (CCPs) is also not subject to significant waterhammer. Therefore, this pipe is no longer required to be surveyed in the upcoming refueling outage.

Suction Pipe:

The ECCS and DHR System Pumps are tested at full flow during each refueling outage. These full flow tests result in a flow rate that transports voids in portions of their suction and discharge pipe to the primary system. The Containment Spray System Pumps are periodically tested at a flow rate (approximately 4,000 gpm) that transports voids in their suction pipe and part of their discharge pipe to the refueling water storage tank. Although not necessary to ensure all pipe segments of the ECCS, DHR System and Containment Spray System suction pipe do not contain voids, all accessible pipe segments were surveyed for unfavorable pipe slope or pipe bow. This survey determined that there are not any locations in this suction pipe that could contain a void that would result in a void fraction at the ECCS, DHR System or Containment Spray System Pumps in excess of their acceptance criteria.

In general, the maximum possible void cross section in the pipe segments is well below 10 percent of the pipe flow area. In a few pipe segments, the maximum possible void cross section exceeds 10 percent of the flow area; however, the maximum possible void volume in these pipe segments is less than 0.5 cubic feet. In addition, the horizontal pipe segments nearest the ECCS, DHR System and Containment Spray System Pumps were inspected by UT and no voiding identified.

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A portion of the DHR System suction pipe from the primary system is located inside containment. The survey of this pipe was identified in reference 2 as being deferred until the next refueling outage. Procedures require venting of this suction pipe just prior to it being placed in service for shutdown cooling. In addition, the configuration of this pipe and its horizontal and vertical distance from the DHR Pump suction ensures that it cannot contain a void that would result in gas binding of the pumps. The DHR System Pumps have not become gas bound with their suctions aligned to the primary system for shutdown cooling.

Therefore, this pipe is no longer required to be surveyed in the upcoming refueling outage.

7. Identify new vent valve locations, modifications to existing vent valves, or utilization of existing vent valves that resulted from the confirmatory walkdowns, and summarize the Corrective Actions, and the schedule for completion of the Corrective Actions.

The survey of ECCS, DHR System and Containment Spray System pipe did not identify the need for additional vent capability.

8. Discuss the results of the fill and vent activities and procedure reviews for each system. (Note that routine periodic surveillance testing is addressed in the "Testing Evaluation" section of this template).

The review of ECCS, DHR System and Containment Spray System operating procedures determined that these procedures provide detailed instructions for filling and venting the suction piping, the pump casing and discharge piping.

WBN has made many plant and procedure changes since initial licensing to ensure the ECCS, DHR System and Containment Spray Systems are adequately filled. Recent operating experience has been that these systems are adequately filled and vented after maintenance or modification and prior to being returned to service.

The operating procedure review also identified:

That not all vent valves that could be used to vent the Safety Injection Pump discharge pipe outside containment were included in the operating procedure for filling and venting this pipe.

There are no instructions for filling and venting portions of the Centrifugal Charging Pump discharge pipe.

The affected operating procedures are being revised to enhance filling and venting performance in these areas.

Nuclear industry operating experience has identified instances where the ECCS has not been adequately filled. Based on this, the ECCS, DHR System and Containment Spray System operating procedures are being revised to require UT inspection or dynamic venting of locations that could contain a significant void should this pipe be drained. These locations will include the discharge pipe high points, which ensure the filling of this pipe is complete. This procedure change E3-8

adds an additional procedural barrier to prevent inadequate filling of a safety system and is an enhancement.

9. Identify procedure revisions, or new procedures resulting from the fill and vent activities and procedure reviews that need to be developed, and summarize the Corrective Actions, and schedule for completion of the Corrective Actions. (Note that routine periodic surveillance testing is addressed in the "Testing Evaluation" section of this template).

As discussed in Item (8), above, the review identified changes to operating procedures to improve instructions for filling portions of the ECCS discharge pipe. In addition, an enhancement to operating procedures is being made through the Corrective Action Program to provide additional actions and checks to ensure the ECCS, DHR System and Containment Spray System pipe is full of water prior to these systems being returned to a status of TS operable.

10. Discuss potential gas intrusion mechanisms into each system for each piping segment that is vulnerable to gas intrusion.

All ECCS, DHR System and Containment Spray System suction pipe is at greater than atmospheric pressure during power operation. This positive pressure results in water leakage from any location that would pull air into the system should the suction pipe pressure drop below atmospheric pressure during a DBA.

There are no significant sources of gas in ECCS, DHR System and Containment Spray System suction pipe, except for the water that circulates through the Centrifugal Charging Pumps (CCPs). These pumps circulate reactor coolant that contains hydrogen and noble gases that can come out of solution and form voids in the suction pipe. At WBN, continuous vents remove voids from locations that due to pipe configuration could collect gas.

Voids can form in the CLI lines due to primary system and Cold Leg Accumulator (CLA) leakage. Primary system and CLA leakage is monitored and trended. In addition, WBN operating experience is that this leakage results in pressurization of the ECCS discharge pipe. These indicators would be used to assess the need for an increase in the frequency of ECCS discharge pipe venting (through the Corrective Action Program).

The Safety Injection Pumps (SIPs) and Residual Heat Removal Pumps (RHRPs) are the intermediate head and low head ECCS Pumps, respectively. These pumps are aligned to their CLI lines during power operation. These pumps are individually tested each quarter in a configuration that results in the compression of any voids in their CLI lines. Recent operating experience from these quarterly tests has shown that unacceptable pressure pulsations or hydraulic forces do not occur when these pumps are started. This is the basis for the conclusion that a successful quarterly test of the SIPs and RHRPs (i.e.; no waterhammer) provides verification that voids in the SIP and RHRP discharge pipe are below that which significantly affect their safety functions.

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11. Ongoing Industry Programs Ongoing industry programs are planned in the following areas which may impact the conclusions reached during the Design Evaluation relative to gas accumulation. The activities will be monitored to determine if additional changes to the plant design may be required or desired to provide additional margin.

Gas Transport in Pump Suction Piping The PWROG has initiated testing to provide additional knowledge relative to gas transport in large diameter piping. One program performed testing of gas transport in 6-inch and 8-inch piping. Another program will perform additional testing of gas transport in 4-inch and 12-inch low temperature systems and 4-inch high temperature systems. This program will also integrate the results of the 4-inch, 6-inch, 8-inch'and 12-inch testing.

0 Pump Acceptance Criteria Long-term industry tasks were identified that will provide additional tools to address GL-2008-01 with respect to pump gas void ingestion tolerance limits.

12. Provide a detailed list of items that have not been completed, a schedule for their completion, and the basis for that schedule.

This information is in Section B.

Testing Evaluation

1. Discuss the results of the periodic venting or gas accumulation surveillance procedure review.

WBN has procedures for the venting of the ECCS. This venting is done to meet SR 3.5.2.3. Vent valves at the high points on the discharge pipe of the ECCS are opened each month and any gas discharge is identified and evaluated.

Operating experience from periodic venting of these high points indicates that the ECCS discharge pipe is maintained full of water. There have been no incidents where any of these systems were found in a voided condition that would have prevented them from performing their safety functions.

2. Identify procedure revisions, or new procedures resulting from the periodic venting or gas accumulation surveillance procedure review that need to be developed, and summarize the Corrective Actions, and schedule for completion of the Corrective Actions. For example, new or revised procedure(s) were implemented for additional leak testing or periodic maintenance to demonstrate the leak tightness of valves in potential gas intrusion paths.

The procedures that are used to meet SR 3.5.2.3 are being revised to require that, in the event of an extended gas release, a report is entered into the Corrective Action Program.

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3. Discuss how procedures adequately address the manual operation of the DHR System in its decay heat removal mode of operation. Include how the procedures assure that the DHR System is sufficiently full of water to perform its decay heat removal safety function (high point venting or UT) and how pump operation is monitored by plant personnel (including a description of the available instrumentation and alarms).

Procedures require venting of the suction and discharge pipe in the DHR System, just prior to it being placed in service for shutdown cooling. When placed in service for shutdown cooling, the isolation valves in the suction pipe are opened and the DHR System pressurizes to primary system pressure prior to starting the DHR System Pumps. Any pre-existing voids in the system are compressed to roughly 1/10 of their original size. The DHR System would need to be greatly voided in standby to contain a significant void once pressurized for shutdown operation. The DHR System Pumps have not become gas bound with their suctions aligned to the primary system for shutdown cooling.

Operators have instrumentation to monitor the DHR System and procedures to mitigate a loss of the DHR System.

4. Summarize the results of the procedure reviews performed to determine that gas intrusion does not occur as a result of inadvertent draining due to valve manipulations specified in the procedures, system realignments, or incorrect maintenance procedures.

WBN operating experience is that testing, maintenance or system alignment changes do not result in inadvertent draining or the introduction of voids into the ECCS, DHR System or Containment Spray System.

5. Describe how gas voids are documented (including the detection method such as venting and measuring or UT and void sizing and post venting checks), dispositioned (including method(s) used such as static or dynamic venting), and trended, if found in any of the subject systems.

As discussed in Item (2), above, procedures that are used for meeting SR 3.5.2.3 are being revised to require that, for an extended gas release in the ECCS and DHR System, a report is entered into the Corrective Action Program.

6. Provide a detailed list of items that have not been completed, a schedule for their completion, and the basis for that schedule.

This information is in Section B.

Corrective Actions Evaluation

1. Summarize the results of the reviews regarding how gas accumulation has been addressed at your site.

WBN's Corrective Action Program is used to document gas intrusion /

accumulation issues as potential nonconforming conditions. As part of these E3-11

Corrective Action Programs, Problem Evaluation Reports related to plant equipment are evaluated for potential impact on operability and reportability.

Therefore, WBN's review concluded that issues involving gas intrusion /

accumulation are properly prioritized and evaluated under the Corrective Action Program.

2. Provide a detailed list of items that have not been completed, a schedule for their completion, and the basis for that schedule.

This information is in Section B.

Conclusion Based upon the above, TVA has concluded that WBN is in conformance with 10 CFR 50, Appendix B, Criterion III, V, XI, XVI, and XVII, and any identified deviations have been entered into the WBN Corrective Action Program for tracking and final resolution, as described in Section B.

B. DESCRIPTION OF CORRECTIVE ACTIONS, SCHEDULE AND JUSTIFICATION FOR SCHEDULE The completed evaluations have determined that voiding is being maintained less than the amount that challenges the capability of the ECCS, DHR System and Containment Spray System to mitigate DBAs and maintain SSD. Based on these systems being fully capable of performing their safety functions, the schedule for completing the corrective actions is listed in Table 3:

TABLE 3 Item Description Date

1. TVA will evaluate adopting the revised Integrated Within 6 Standard Technical Specification (ISTS) SR 3.5.2.3 months of (NUREG 1431) at WBN.

NRC approval of the Traveler

2. The design change review checklist is revised to include Complete an explicit item to determine if the design change introduces or increases the potential for gas accumulation beyond established acceptance criteria.

3. Operating procedures are being revised to improve 1/31/2009 instructions for filling portions of the ECCS discharge pipe.

4. The ECCS, DHR System and Containment Spray System 1/31/2009 operating procedures are being revised to require UT inspection or dynamic venting of locations that could contain a significant void should this pipe be drained.

5. Periodic venting procedures used to meet SR 3.5.2.3 are 1/31/2009 being revised to require that, for an extended gas release, a report is entered into the Corrective Action Program.

Items 2 through 5 have been entered into WBN's Corrective Action Program. A Commitment for item 1 in the above Table is listed in Enclosure 4.

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In addition, the BWRPPWROG is proceeding with various programs on the affect of voids on safety system performance. TVA will follow the BWR/PWROG Programs and take additional actions, if needed to ensure system operability, as the results of these programs becomes available.

Revision to ISTS SR 3.5.2.3 (NUREG 1431) may result in a requirement that quantitative void limits for some locations in the ECCS and DHR System are established and that void monitoring be implemented. A TS SR change of this scope would require additional plant specific calculations and plant modifications may be required to implement void monitoring. The timeframe for evaluating the revised TS for adoption is left somewhat open at this time due to the recently developing NRC and industry efforts.

Conclusion TVA has evaluated the accessible portions of those WBN systems that perform the functions described in this GL and has concluded that these systems are Operable, as defined in their TS and are in conformance to commitments to the applicable General Design Criteria (GDC), as stated in the WBN UFSAR.

The open actions cited above are considered to be enhancements to the existing programs/processes/procedures for assuring continued Operability of these subject systems.

As committed in Reference 2, TVA will complete its evaluation of the inaccessible portions of these systems by startup from the next Refueling Outage at WBN and will provide a supplement to this response within 90 days thereafter.

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ENCLOSURE4 LIST OF TVA COMMITMENTS LIST OF BFN-SPECIFIC COMMITMENTS TVA will evaluate adopting the revised Integrated Standard Technical Specification (ISTS) Surveillance Requirement (SR) 3.5.1.1 at BFN (NUREG 1433) within 6 months of NRC approval of the Traveler.

LIST OF SQN-SPECIFIC COMMITMENTS TVA will evaluate adopting the revised ISTS SR 3.5.2.3 (NUREG 1431) at SQN within 6 months of NRC approval of the Traveler.

LIST OF WBN-SPECIFIC COMMITMENTS TVA will evaluate adopting the revised ISTS SR 3.5.2.3 (NUREG 1431) at WBN within 6 months of NRC approval of the Traveler.

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