Text

Generic Letter 2004-02 Response Extension Request
	ML073440044
Person / Time
Site:	Vogtle
Issue date:	12/07/2007
From:	Stinson L; Southern Nuclear Operating Co
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	GL-07-002, NL-07-1969
	Download: ML073440044 (19)
	v • d • e

L M. Stinson (Mike) Southern Nuclear Vice President Operating Company, Inc.

Fleet Operations Support 40 Inverness Center Parkway Post Office Box 1295 Birmingham. Alabama 35201 Tel 205.992.5181 Fax 205.992.0341 SOUTHERN COMPANY A

December 7, 2007 Energy to Serve lOur World'"

Docket Nos.: 50-424 NL-07-1969 50-425 U. S. Nuclear RegUlatory Commission ATrN: Document Control Desk Washington, D. C. 20555-0001 Vogtle Electric Generating Plant Units 1 and 2 Generic Letter 2004-02 Response Extension Request Ladies and Gentlemen:

By letter dated August 31, 2005, Southern Nuclear Operating Company (SNC) submitted a combined SNC response for Joseph M. Farley Nuclear Plant (FNP) and Vogtle Electric Generating Plant (VEGP) as required by NRC Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized Water Reactors." In this letter, SNC committed to the installation of the VEGP Unit 1 and Unit 2 new post-LOCA containment sump recirculation screens, completion of required modifications, and implementation of required procedural changes by December 31, 2007.

By letter dated June 22, 2006, SNC requested an extension for the completion of the modifications to mitigate downstream effects for VEGP Unit 1 until the completion of the Unit 1 2008 spring outage. This letter also provided SNC's basis for concluding that it is acceptable to extend the completion time for the modifications. In a teleconference on June 30, 2006 with the NRC staff reviewer of the June 22, 2006 extension request, SNC was requested to provide an update of on-going activities and a clarification to the basis for the extension request. By letter dated JUly 28, 2006, SNC provided an update of on-going activities and a clarification to the basis for the extension request. The extension request was approved by the NRC in a letter dated September 7,2006.

SNC is fully committed to resolving GSI-191. To improve existing margins until all modifications and head loss/chemical effects testing can be implemented, VEGP has performed the following modifications:

Installed new sump screens on Units 1 & 2 that increased the available screen area approximately 1400% for each of the Residual Heat Removal (RHR) screens, and approximately 1075% for each of the Containment Spray (CS) screens. The new sump screens have a smaller mesh size, 3/32" diameter vs. 1/8" square opening on the old screens. The new screens were sized to the original debris generation criteria of NEI 04-07 and the associated NRC Safety Evaluation Report dated December 6,

U. S. Nuclear Regulatory Commission NL-07-1969 Page 2 2004. The debris loading has since been reduced significantly due to a reduction in the Zone of Influence (ZOI) for Nukon insulation and coatings.

Preliminary head loss testing (without chemical effects) performed for Vogtle yielded that removal of Min-K insulation resulted in a significant reduction in head loss across a loaded screen. Based on this testing, Min-K insulation that was in the original ZOI analyzed for GL 2004-02 was removed from both VEGP containments.

Modifications to mitigate downstream effects on Unit 2 were completed during the spring 2007 outage. Installation of the new Unit 1 Emergency Core Cooling System flow orifices is scheduled for the Spring 2008 outage. (Note: The extension request was previously approved by the NRC in a letter dated September 7,2006.)

However, in addition to the Unit 1 downstream effects modifications, the VEGP passive screen design still has open industry and plant specific design issues to be resolved. The projected outstanding items for each unit are:

Complete downstream effects evaluations in accordance with WCAP 16406-P Rev. 1, "Evaluation of Downstream Sump Debris Effects in Support of GSI-191" and WCAP-16793-NP, "Evaluation of Long-Term Cooling Considering Particulate, Fibrous and Chemical Debris in the Recirculating Fluid."

Complete chemical effects testing and evaluation of test results.

Determine 1) whether hardware and/or procedural modifications are needed as a result of the downstream effects evaluations and chemical effects testing/evaluation, and 2) modification implementation schedule, if required.

Develop a license amendment request (LAR) and receive NRC approval of new Technical Specification values for the Refueling Water Storage Tank (RWST) minimum volume and semi-automatic switchover values.

It is estimated that approximately 9.5 feet of head loss margin will be available to account for chemical effects.

In addition, during the review of Operational Experience of the industry with respect to GSI-191 containment sump designs and supporting analyses. SNC identified certain nonconservatisms that were not accounted for in the analyses.

and nonconservatisms in the design input from SNC to the vendor designing the sump screens. The net effect of these nonconservatisms was that the new Residual Heat Removal (RHR) sump screens would potentially not be fully SUbmerged in the worst case scenario at the initiation of cold-leg recirculation.

The containment spray sump screens are not affected by this condition as they are not as tall as the RHR sump screens. In order to ensure that the new RHR

U. S. Nuclear Regulatory Commission NL-07-1969 Page 3 sump screens are indeed submerged, SNC has identified the need for two changes to the VEGP Technical Specifications (TS):

1) Increase the minimum RWST inventory required by SR 3.5.4.2.

2) Decrease the Nominal Trip Setpoint LCO 3.3.2, Table 3.3.2-1, Functional Unit 7b, Semi-Automatic Switchover to Containment Sump, RWST Level Low. The associated Allowable Value would be decreased commensurately.

SNC has performed an operability determination that documents the operability of the screens under current design and licensing basis conditions. This evaluation included vortexing, air ingestion, and RHR net positive suction head (NPSH).

The evaluation demonstrated that the new sump screens are capable of performing their functions under current design and licensing basis conditions given the nonconservatisms discussed above. Note that the basis for the previously approved extension for Unit 1 downstream effects modifications is not affected by this condition.

The need for a LAR was discussed with NRC NRR personnel and the NRR project manager for VEGP on November 13, 2007. SNC will be submitting the Technical Specification LAR by January 11, 2008. This submittal date was discussed with the NRR project manger for VEGP on November 28, 2007.

Considering the above, an extension to the completion schedule is respectfully requested to extend the completion of the corrective actions required by Generic Letter 2004-02 for VEGP Units 1 and 2 from December 31,2007 to June 30, 2008. This would allow SNC time to complete downstream effects modifications for Unit 1, complete the downstream effects evaluation for both units, receive and process the screen vendors test reports for chemical effects testing, and allow sufficient time for the NRC review and approval of the Technical Specification LAR for both units. Based on the upcoming spring outage for flow orifice installation (downstream effects modification preViously approved), June 30,2008 is within 90 days after completion of all actions needed to address Generic Letter 2004-02. to this letter provides the basis for SNC's conclusion that it is acceptable to extend the completion of the corrective actions required by Generic Letter 2004-02, an update of on-going activities, and a clarification to the basis for the extension request.

The NRC commitments contained in this letter are provided as a table in . If you have any questions, please advise.

SNC requests approval of the proposed request by December 31, 2007.

U. S. Nuclear Regulatory Commission NL-07-1969 Page 4 Mr. L. M. Stinson states he is a Vice President of Southern Nuclear Operating Company, is authorized to execute this oath on behalf of Southern Nuclear Operating Company and to the best of his knowledge and belief, the facts set forth in this letter are true.

Respectfully submitted, SOUTHERN NUCLEAR OPERATING COMPANY

/?/t(*41~

L. M. Stinson Vice President Fleet Operations Support Sworn to and subscribed before me this 16 day of ~ bec ,2007.

/uO.Y-LtNotary Public My commission expires: J: Iy --1 .;kl ~

LMS/DWM/daj

Enclosures:

1. SNC Request for Extension for Completing Corrective Actions for Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors"

2. List of Regulatory Commitments cc: Southern Nuclear Operating Company Mr. J. T. Gasser, Executive Vice President Mr. T. E. Tynan, Vice President - Vogtle Mr. D. H. Jones, Vice President - Engineering RType: CVC7000 U. S. Nuclear Regulatory Commission Mr. V. M. Mcree, Acting Regional Administrator Mr. S. P. Lingam, NRR Project Manager - Vogtle Mr. G. J. McCoy, Senior Resident Inspector - Vogtle State of Georgia Mr. N. Holcomb, Commissioner - Department of Natural Resources

Vogtle Electric Generating Plant GL 2004-02 Extension Request Enclosure 1 GL 2004-02 Extension Request

Vogtle Electric Generating Plant GL 2004-02 Extension Request Enclosure 1 GL 2004-02 Extension Request Table of Contents 1.0 Background 2.0 Justification for Proposed Extension 3.0 Reason for the Request for Proposed Extension 4.0 Compliance with SECY-06-0078 Criteria 4.1 SECY-06-0078 Criterion NO.1:

4.2 SECY-06-0078 Criterion NO.2:

4.2.1 Mitigative Measures 4.2.2 New Screen Installation 4.2.3 Debris Generation 4.2.4 Leak-Before-Break (LBB) 4.2.5 Containment Floor Configuration 4.2.6 Zone-Of-Influence Reduction for Qualified Coatings 4.2.7 Procedure Guidance, Training and Actions 4.2.8 Containment Cleanliness 5.0 Risk Assessment 6.0 Conclusion

Enclosure 1 GL 200+02 Extension Request 1.0 Background By letter dated August 31,2005, Southern Nuclear Operating Company (SNC) submitted a combined SNC response for Joseph M. Farley Nuclear Plant (FNP) and Vogtle Electric Generating Plant (VEGP) as required by NRC Generic Letter 2004*02, "Potential Impact of Debris Blockage on Emergency Recirculation during Design Basis Accidents at Pressurized Water Reactors." In this letter, SNC committed to the installation of the VEGP Unit 1 and Unit 2 new post-LOCA containment sump recirculation screens, completion of required modifications, and implementation of required procedural changes by December 31,2007. By letter dated June 22, 2006, SNC requested an extension for the completion of the modifications to mitigate downstream effects for VEGP Unit 1 until the completion of the Unit 1 2008 spring outage. This letter also provided SNC's basis for concluding that it is acceptable to extend the completion time for the modifications. In a teleconference on June 30, 2006 with the NRC staff reviewer of the June 22,2006 extension request, SNC was requested to provide an update of on-going activities and a clarification to the basis for the extension request. The extension request was approved by the NRC in a letter dated September 7,2006.

SNC is fUlly committed to resolving GSI-191. To improve existing margins until all modifications and head loss/chemical effects testing can be implemented, VEGP has performed the folloWing analyses/modifications:

Installed new sump screens on Units 1 & 2 that increased the available screen area from approximately 54 sq ft to 765 sq ft for each of the Residual Heat Removal (RHR) screens, an approximate 1400% increase, and from approximately 54 sq ft to 590 sq ft for each of the Containment Spray screens, an approximate 1075% increase. The new sump screens have a smaller mesh size, 3/32" diameter vs. 1/8" square opening on the old screens. The new screens were sized to the original debris generation criteria of NEI 04-07 and the associated NRC Safety Evaluation Report (SER) dated December 6, 2004. The debris loading has since been reduced significantly due to a reduction in the Zone of Influence for Nukon insulation and coatings based on recent industry testing.

Preliminary head loss testing (without chemical effects) performed for Vogtle yielded that removal of Min-K insulation resulted in a significant reduction in head loss across a loaded screen. Based on this testing, Min-K insulation that was in the original ZOI analyzed for GL 2004-02 was removed from both VEGP containments.

Modifications to mitigate downstream effects on Unit 2 were completed during the spring 2007 outage. Installation of the new Unit 1 Emergency Core Cooling System (ECCS) flow orifices is scheduled for the Spring 2008 outage. (Note: The extension request was previously approved by the NRC in a letter dated September 7,2006.)

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Enclosure 1 GL 2004-02 Extension Request However, in addition to the downstream effects modifications discussed above, the VEGP passive screen design still has open industry and plant specific design issues to be resolved. The projected outstanding items for each unit are:

Complete downstream effects evaluations in accordance with WCAP 16406-P Rev. 1 "Evaluation of Downstream Sump Debris Effects in Support of GSI-191" and WCAP-16793-NP, "Evaluation of Long-Term Cooling Considering Particulate, Fibrous and Chemical Debris in the Recirculating Fluid."

Complete chemical effects testing and evaluation of test results.

Determine 1) whether hardware and/or procedural modifications are needed as a result of the downstream effects evaluations and chemical effects testing/evaluation, and 2) modification implementation schedule, if required.

Develop a license amendment request (LAR) and receive NRC approval of new Technical Specification values for the Refueling Water Storage Tank (RWST) minimum volume and semi-automatic switchover values.

It is estimated that approximately 9.5 feet of head loss margin will be available to account for chemical effects.

In addition, during the review of Operational Experience of the industry with respect to GSI-191 containment sump designs and supporting analyses, SNC identified certain nonconservatisms that were not accounted for in the analyses, and nonconservatisms in the design input from SNC to the vendor designing the sump screens. The net effect of these nonconservatisms was that the new RHR sump screens would potentially not be fully submerged in the worst case scenario at the initiation of cold-leg recirculation. The containment spray sump screens are not affected by this condition because they are not as tall as the RHR screens. In order to ensure that the new RHR sump screens are indeed submerged, SNC has identified the need for two changes to the VEGP Technical Specifications (TS):

1) Increase the RWST minimum inventory required by SR 3.5.4.2.

2) Decrease the Nominal Trip Setpoint LCO 3.3.2, Table 3.3.2-1, Functional Unit 7b, Semi-Automatic Switchover to Containment Sump, RWST Level Low. The associated Allowable Value would be decreased commensurately.

Revisions to RWST minimum inventory and Semi-Automatic Switchover setpoint will ensure that the ECCS and CS sump strainer will be fUlly submerged at the time of the initiation of switchover to ECCS recirculation. The change in delivered water volume between the current RWST minimum inventory and the RWST Semi-Automatic Switchover Setpoints will significantly increase the amount of E1-2

Enclosure 1 GL 2004-02 Extension Request water in the flood plane at the beginning of ECCS switchover. Not only will this increase available NPSH and reduce transport of debris to the emergency sumps, it will delay the start of ECCS switchover.

The new RWST minimum inventory and Semi-Automatic Switchover setpoint will continue to ensure that ECCS switchover is completed prior to receipt of the RWST Empty alarm. The Containment Spray switchover will continue to occur after the receipt of the RWST Empty alarm. The RWST Empty alarm is also being lowered to provide a conservative volume of water for ECCS transfer assuming the worst single active failure. The revised RWST Empty alarm provides sufficient margin to ensure Containment Spray switchoveris complete and suction to the RWST is isolated without allowing air entrainment from the RWST.

The exact RWST volumes for the minimum required volume and the volume at switchover will be supplied in the Technical Specification amendment request.

These values will be determined taking into account operational considerations for raising the minimum volume and will also account for ensuring sufficient time is allowed for manual operator actions to complete the switchover process.

SNC has performed an operability determination that documents the operability of the screens under current design and licensing basis conditions. This evaluation included vortexing, air ingestion, and RHR net positive suction head (NPSH).

The evaluation demonstrated that the new sump screens are capable of performing their functions under current design and licensing basis conditions given the nonconservatisms discussed above. Note that the basis for the previously approved extension for Unit 1 downstream effects modifications is not affected by this condition.

SNC will be submitting the Technical Specification License Amendment Request (LAR) by January 11, 2008.

Considering the above, an extension to the completion schedule is respectfully requested to extend the completion of the corrective actions required by Generic Letter 2004-02 for VEGP Units 1 and 2 from December 31,2007 to June 30, 2008. This would allow SNC time to complete downstream effects modifications for Unit 1, complete the downstream effects evaluation for both units, receive and process the screen vendors test reports for chemical effects testing, and allow sufficient time for the NRC review and approval of the Technical Specification LAR for both units. Based on the upcoming spring outage for flow orifice installation (downstream effects modi'fication previously approved), June 30, 2008 is within 90 days after completion of all actions needed to address Generic Letter 2004-02.

2.0 Justification for Proposed Extension VEGP will not be in full compliance with GL 2004-02 by December 31, 2007 due to the open industry issues identified above. Justification of the requested extension is based on the following:

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Enclosure 1 GL 2004-02 Extension Request

The VEGP containments are compartmentalized making transport of debris to the sump difficult.

VEGP does not require switchover to recirculation from the sump during a large-break loss-of-coolant accident (LOCA) until approximately 20 minutes after accident initiation, allowing time for much of the debris to settle in other places within containment.

The probability of the initiating event (Le., LBLOCAs) is extremely low.

Safety-related emergency containment coolers can supplement containment heat removal capability if spray flow is degraded.

Application of the leak-before-break analysis principle has been approved by the NRC Staff for VEGP. Postulated breaks in the reactor coolant loop (RCL), except for branch line connections, have been eliminated for both Unit 1 and Unit 2.

Leak-before-break (LBB) qualified piping is of sufficient toughness that it will most likely leak (even under safe shutdown earthquake conditions) rather than rupture. The current issue regarding primary water stress corrosion cracking (PWSCC) associated with pressurizer Alloy 82/182 dissimilar metal welds was addressed during the Unit 2 Spring 2007 refueling outage by the use of weld overlay on the pressurizer surge line nozzle-to-safe end weld followed by nondestructive examinations using Performance-Demonstration Initiative (PDI)-qualified techniques. In addition, the pressurizer relief, safety, and spray nozzle-to safe end welds were also proactively mitigated using weld overlays followed by nondestructive examination using PDI-qualified techniques. Mitigation by weld overlay will be completed for the equivalent pressurizer nozzles on Unit 1, including the examination thereof, by the end of the Unit 1 Spring 2008 refueling outage.

Additional favorable design features and administrative controls are described in Section 4.2.1 Mitigative Measures below. These elements will remain valid during the extension period requested by this submittal.

3.0 Reason for the Request for Proposed Extension VEGP will not be in full compliance with GL 2004-02 by December 31, 2007 due to the open industry issues identified above. The follOWing activities require completion to address GL 2004-02:

Complete downstream effects evaluations in accordance with WCAP 16406-P Rev. 1, "Evaluation of Downstream Sump Debris Effects in Support of GSI-191."

Complete the plant-specific chemical plateout evaluation per WCAP 16793-NP, "Evaluation of Long-Term Cooling Considering Particulate, E1-4

Enclosure 1 GL 2004-02 Extension Request Fibrous and Chemical Debris in the Recirculating Fluid."

PerWCAP-16793-NP, reasonable assurance of long-term core cooling for all plants is demonstrated by the following:

1. The size of holes in replacement sump screens designs limits the size of debris that is passed through the screen during operation of the ECCS in the recirculation mode.

2. Based on available test observations, the characteristic dimension of this debris is typically less than the screen hole size, even for fibrous debris. Consequently, debris buildup at critical locations in the reactor vessel and core is not expected.

3. Based on data presented internationally during the resolution of the BWR strainer performance concerns, fibrous debris was observed to not strongly adhere to fuel cladding. Thus, the small size of the debris and its tendency to not adhere to fuel indicates that long-term core cooling of the fuel will not be impaired by either the collection of fibrous and particulate debris in fuel elements, or by the collection of fibrous debris on fuel cladding surfaces.

4. Supporting calculations have demonstrated long-term core cooling will be maintained with about 99.4% of the core blocked. The cladding temperature response to blockage at grids and the collection of precipitation on clad surfaces was also demonstrated to be acceptable with resulting cladding temperatures less than 400°F.

5. A method to evaluate chemical effects on fuel has been developed, applied to several "worst case" plant chemistries and acceptable clad temperatures were calculated.

The WCAP concludes that reasonable assurance of acceptable long term core cooling with debris and chemical products in the recirculating fluid is demonstrated for all plants based on;

Items 1 through and including 4, are directly applicable to all PWRs, and,

Either a demonstration that the sample calculations identified in Item 5, above, bound the plant-specific chemistry, or the completion of a plant-specific calculation using the method identified in Item 5, above.

SNC had not completed the plant-specific calculation using the method identified in Item 5, above.

Complete chemical effects testing and evaluation of test results.

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Enclosure 1 GL 2004-02 Extension Request

Determine 1) whether hardware and/or procedural modifications are needed as a result of the downstream effects evaluations and chemical effects testing/evaluation, and 2) modification implementation schedule, if required.

NRC Approval of the LAR to increase the minimum required volume for the RWST and decrease the setpoint for the semi-automatic switchover from the RWST to the containment sumps.

4.0 Compliance with SECY*06-0078 Criteria SECY-06-0078 dated March 31,2006, "Status of Resolution of GSI-191, "Assessment of [Effect 01] Debris Accumulation on PWR Sump Performance,"

specifies two criteria for short duration GL 2004-02 extensions limited to several months. These first two criteria and SNC's responses are provided below.

4.1 SECY*06-0078 Criterion No.1:

The licensee has a plant-specific technicaVexperimental plan with milestones and schedule to address outstanding technical issues with enough margin to account for uncertainties.

SNC Response .

ISSUE COMPLETION DATE Submit LAR for Tech Spec amendment January 11, 2008 to increase the minimum required volume for the RWST and decrease the setpoint for the semi-automatic switchover from the RWST to the containment sumps.

Complete downstream effects 1st Qtr 2008 evaluations in accordance with WCAP 16406-P Rev. 1 and WCAP-16793-NP.

Complete chemical effects testing and 1st Qtr 2008 evaluation of test results.

Determine 1) whether hardware and/or 1st Qtr 2008 procedural modifications are needed as a result of the downstream effects evaluations and chemical effects testing/evaluation, and 2) modification imolementation schedule, if reauired.

Installation of the new Unit 1 ECCS Spring 2008 outage flow orifices. (Note: The extension request for this activity was previously approved by the NRC in a letter dated September 7,2006.)

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Enclosure 1 GL 2004-02 Extension Request Based on the above discussion, SNC meets the requirements of SECY-06 0078 Criterion No.1.

4.2 SECY-06-0078 Criterion No.2:

The licensee identifies mitigative measures to be put in place prior to December 31, 2007, and adequately describes how these mitigative measures will minimize the risk of degraded EGGS [emergency core cooling system] and CSS [containment spray system] functions during the extension period.

SNC Response The following mitigative measures have already been implemented to minimize the risk of degraded ECCS and CSS functions during the extension period.

4.2.1 Mitigative Measures The following mitigative measures have already been implemented to minimize the risk of degraded ECCS and CSS functions during the extension period:

SNC has completed the installation of the new sump strainers on Units 1 and 2. These strainers have increased available surface area to deal with debris in the recirculation water.

Procedural guidance exists regarding containment foreign material exclusion (FME) controls. This helps ensure that the strainers are not subjected to undue loading from foreign material.

Bulletin 2003-01 training and procedural guidance to expedite plant cooldown in response to a small break LOCA are incorporated into plant emergency response procedures.

Preliminary head loss testing (without chemical effects) performed for Vogtle yielded that removal of Min-K insulation resulted in a significant reduction in head loss across a loaded screen. Based on this testing, Min-K insulation that was in the original ZOI analyzed for GL 2004-02, was removed from VEGP's containments.

Application of the leak-before-break analysis principle has been approved by the NRC Staff for VEGP in relation to breaks in the reactor coolant loop primary piping and pressurizer surge line piping. Thus the debris loading that SNC has assumed for the strainers is conservative.

The NPSH analysis for the CS System pumps and the RHR pumps do not credit containment overpressure. Therefore the NPSH analyses for E1-7

Enclosure 1 GL 2004-02 Extension Request VEGP are conservative and additional margin is available.

4.2.2 New Screen Installation VEGP has installed new sump screens on Units 1 & 2 that increased the available screen area from approximately 54 sq ft to 765 sq ft for each of the RHR screens, an approximate 1400% increase, and from approximately 54 sq ft to 590 sq ft for each of the Containment Spray screens, an approximate 1075%

increase. The new sump screens have a smaller mesh size, 3/32" diameter vs.

1/8" square opening on the old screens. The new screens were sized to the original debris generation criteria of NEI 04-07 and NRC SER dated December 6, 2004. The debris loading has since been reduced significantly due to a reduction in the Zone of Influence for Nukon insulation and coatings based on recent industry testing.

4.2.3 Debris Generation The insulation in containment at Vogtle Nuclear Power Plant consists mainly of Nukon Fiber. The amount of Nukon debris generated is dependent on the proximity of each insulated target to the postulated break. The SER (Reference

3) recommends a ZOI radius of 17.00 ("0" being the inside diameter of the pipe break) for both jacketed and unjacketed Nukon Fiber. Based on industry testing contained in Westinghouse report WCAP-16710-P, "Jet Impingement testing to Determine the Zone of Influence (ZOI) of Min-K and NUKON Insulation for Wolf Creek and Callaway Nuclear Operating Plants," a reduced ZOI of 8.00 is used for the Vogtle Nuclear Power Plant debris generation analysis.

4.2.4 Leak*Before--Break (LBB)

Postulated breaks in the reactor coolant loop (RCL), except for branch line connections, have been eliminated for both Unit 1 and Unit 2 (reference Federal Register, Vol. 50, No. 27, February 8, 1985). Subsequent to the General Design Criterion 4 final rule change (52 FR 41288, October 27, 1987), postulated breaks in the RCL branch lines (pressurizer surge line, accumulator line, and residual heat removal (RHR) line for Unit 2 and the pressurizer surge line for Unit 1) were eliminated by application of leak-before-break technology. Approval of the elimination of breaks in these Unit 2 branch lines is given in the Vogtle Safety Evaluation Report, Supplement 7, dated November 19, 1987. The necessary information supporting the elimination of breaks in the Unit 1 pressurizer surge line was submitted to the NRC via GPC-to-NRC letter transmitting WCAP-12218 Supplement 1 and WCAP-12219 Supplement 1.

While leak-before-break is not being used to establish the design basis debris load on the new sump screens, the use of LBB results in a substantial reduction in the zone of influence, and thus a significant reduction in the postUlated debris generation and loading on the sump screens. With the installation of the additional sump screen area, the possibility of screen clogging due to debris is greatly reduced.

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Enclosure 1 GL 2004-02 Extension Request Leak-before-break qualified piping is of sufficient toughness that it will most likely leak (even under safe shutdown earthquake conditions) rather than rupture. The current issue regarding primary water stress corrosion cracking (PWSCC) associated with pressurizer Alloy 82/182 dissimilar metal welds was addressed during the Unit 2 Spring 2007 refueling outage by the use of weld overlay on the pressurizer surge line nozzle-to-safe end weld followed by nondestructive examinations using Performance-Demonstration Initiative (PDI)-qualified techniques. In addition, the pressurizer relief, safety, and spray nozzle-to safe end welds were also proactively mitigated using weld overlays followed by nondestructive examination using PDI-qualified techniques. Mitigation by weld overlay will be completed for the equivalent pressurizer nozzles on Unit 1, including the examination thereof, by the end of the Unit 1 Spring 2008 refueling outage.

4.2.5 Containment Floor Configuration Heavy particles are impeded from reaching the sumps because the surrounding floor slopes away from the sumps. This facilitates settling of debris on the floor prior to reaching the sump area. In addition, the new screens will be mounted approximately six inches above the containment floor. This raised mounting would allow accumulation of debris below screen inlet levels and the possibility of sump screen clogging is reduced.

4.2.6 Zone-Of-Influence Reduction for Qualified Coatings Coatings on steel, concrete and equipment in containment are also evaluated.

Qualified coatings are evaluated for a 4.0D ZOI based upon the results of testing presented in WCAP-16568-P, "Jet Impingement Testing to Determine the Zone of Influence (ZOI) for DBA-Qualified / Acceptable Coatings." Unqualified coatings are all considered to be debris, as recommended by the guidance documents.

4.2.7 Procedure Guidance, Training and Actions By letter dated August 26, 2005, the NRC acknowledged VEGP's response to NRC Bulletin 2003-01, "Potential Impact of Debris Blockage on Emergency Sump Recirculation at Pressurized Water Reactors" as responsive and meets the intent of the bulletin. SNC's letter stated in the bulletin response of August 7,2003, that it had implemented the following interim compensatory measures:

(1) Training on integrated plant computer indications to ensure adequate ECCS now through both the injection and recirculation phases; new training materials and simulator scenarios addressing the need for long-term monitoring of the recirculation phase; how to recognize that sump blockage is taking place; and actions to be taken if blockage is encountered.

(2) Guidance to reduce depletion of the RWST and initiate makeup to the RWST from normal and alternate sources during efforts to restore normal ECCS f1owpaths.

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Enclosure 1 GL 2004-02 Extension Request (3) sump screen and rack inspections for cleanliness, damage, corrosion and stability upon containment entry; containment exit inspections with logged material accounting procedures, and comparable controls for emergency entries into containment; and post-outage emergency sump cleanliness and material control procedures to ensure the sumps are free of debris such as trash, rags, tools or protective clothing.

(4) Post-refueling and heat-up procedures to inspect that reactor cavity drains are properly restored with their blind flanges removed.

(5) Inspections to ensure ECCS subsystem inlets are free of debris and show no evidence of abnormal corrosion or structural distress, and that the sump screens are correctly configured and securely bolted in place.

4.2.8 Containment Cleanliness A containment exit inspection procedure is implemented after every containment entry and during each refueling outage, prior to entering Mode 4 from Mode 5 and establishing containment integrity. The primary purpose of this procedure is to ensure compliance with the Vogtle Technical Requirements Manual by verifying that no debris is present in the Containment BUilding which could be transported to the emergency sump and cause restriction of ECCS pump suctions during LOCA conditions. After the transition to Mode 4, the procedure also requires that any material taken into containment be logged in and out.

Logged materials remaining inside containment after Mode 4 entry must be attended at all times and capable of being removed promptly in the event of an emergency. The procedure includes a data sheet detailing materials normally left inside containment. The data sheet is used to evaluate the status of these materials and verify that approved limits are not exceeded.

In addition to the procedure described above, Vogtle administrative procedures establish comparable controls for ensuring emergency sump cleanliness and integrity for containment entries in Modes 1 through 4.

5.0 Risk Assessment The design features and the administrative controls listed in the Justification for Extension and the Mitigative Measures sections adequately support the risk of this extension request. In addition, NRC letter dated November 8, 2007 to Mr.

Anthony R. Pietrangelo of NEI stated that extension requests beyond June 30, 2008 should include a quantitative risk assessment to support its request. Since the extension request for downstream effects evaluations / chemical effects testing and evaluations is not requested beyond June 30, 2008, no quantitative risk assessment is required.

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Enclosure 1 GL 2004-02 Extension Request 6.0 Conclusion Per the criteria listed in SECY 06-0078, SNC has established a plant-specific plan with milestones and schedules to address outstanding technical issues with enough margin to account for uncertainties. Additionally, SNC has identified mitigative measures to be put in place by December 31, 2007. and adequately described how these mitigative measures will minimize the risk of degraded ECCS functions during the extension period.

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Vogtle Electric Generating Plant Generic Letter 2004-02 Response Extension Request Enclosure 2 List of Regulatory Commitments

List of Regulatory Commitments The following table identifies those actions committed by Southern Nuclear Operating Company in this document Vogtle Electric Generating Plant. Any other statements in this submittal are provided for information purposes and are not considered to be regulatory commitments.

Regulatory Commitments Due Date I Event Submit LAR for TS revision to increase the minimum required volume for the RWST and decrease the setpoint for the semi-automatic January 11, 2008 switchover from the RWST to the containment sumps.

VEGP Units 1 and 2 will be in compliance with the regUlatory requirements listed in the Applicable June 30,2008 Regulatory Requirements section of GL 2004-02.

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L M. Stinson (Mike) Southern Nuclear Vice President Operating Company, Inc.

Fleet Operations Support 40 Inverness Center Parkway Post Office Box 1295 Birmingham. Alabama 35201 Tel 205.992.5181 Fax 205.992.0341 SOUTHERN COMPANY A

December 7, 2007 Energy to Serve lOur World'"

Docket Nos.: 50-424 NL-07-1969 50-425 U. S. Nuclear RegUlatory Commission ATrN: Document Control Desk Washington, D. C. 20555-0001 Vogtle Electric Generating Plant Units 1 and 2 Generic Letter 2004-02 Response Extension Request Ladies and Gentlemen:

By letter dated August 31, 2005, Southern Nuclear Operating Company (SNC) submitted a combined SNC response for Joseph M. Farley Nuclear Plant (FNP) and Vogtle Electric Generating Plant (VEGP) as required by NRC Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized Water Reactors." In this letter, SNC committed to the installation of the VEGP Unit 1 and Unit 2 new post-LOCA containment sump recirculation screens, completion of required modifications, and implementation of required procedural changes by December 31, 2007.

By letter dated June 22, 2006, SNC requested an extension for the completion of the modifications to mitigate downstream effects for VEGP Unit 1 until the completion of the Unit 1 2008 spring outage. This letter also provided SNC's basis for concluding that it is acceptable to extend the completion time for the modifications. In a teleconference on June 30, 2006 with the NRC staff reviewer of the June 22, 2006 extension request, SNC was requested to provide an update of on-going activities and a clarification to the basis for the extension request. By letter dated JUly 28, 2006, SNC provided an update of on-going activities and a clarification to the basis for the extension request. The extension request was approved by the NRC in a letter dated September 7,2006.

SNC is fully committed to resolving GSI-191. To improve existing margins until all modifications and head loss/chemical effects testing can be implemented, VEGP has performed the following modifications:

Installed new sump screens on Units 1 & 2 that increased the available screen area approximately 1400% for each of the Residual Heat Removal (RHR) screens, and approximately 1075% for each of the Containment Spray (CS) screens. The new sump screens have a smaller mesh size, 3/32" diameter vs. 1/8" square opening on the old screens. The new screens were sized to the original debris generation criteria of NEI 04-07 and the associated NRC Safety Evaluation Report dated December 6,

U. S. Nuclear Regulatory Commission NL-07-1969 Page 2 2004. The debris loading has since been reduced significantly due to a reduction in the Zone of Influence (ZOI) for Nukon insulation and coatings.

Preliminary head loss testing (without chemical effects) performed for Vogtle yielded that removal of Min-K insulation resulted in a significant reduction in head loss across a loaded screen. Based on this testing, Min-K insulation that was in the original ZOI analyzed for GL 2004-02 was removed from both VEGP containments.

Modifications to mitigate downstream effects on Unit 2 were completed during the spring 2007 outage. Installation of the new Unit 1 Emergency Core Cooling System flow orifices is scheduled for the Spring 2008 outage. (Note: The extension request was previously approved by the NRC in a letter dated September 7,2006.)

However, in addition to the Unit 1 downstream effects modifications, the VEGP passive screen design still has open industry and plant specific design issues to be resolved. The projected outstanding items for each unit are:

Complete downstream effects evaluations in accordance with WCAP 16406-P Rev. 1, "Evaluation of Downstream Sump Debris Effects in Support of GSI-191" and WCAP-16793-NP, "Evaluation of Long-Term Cooling Considering Particulate, Fibrous and Chemical Debris in the Recirculating Fluid."

Complete chemical effects testing and evaluation of test results.

Determine 1) whether hardware and/or procedural modifications are needed as a result of the downstream effects evaluations and chemical effects testing/evaluation, and 2) modification implementation schedule, if required.

Develop a license amendment request (LAR) and receive NRC approval of new Technical Specification values for the Refueling Water Storage Tank (RWST) minimum volume and semi-automatic switchover values.