ML083330276

Revision to Tornado/Helb Mitigation Strategies and Regulatory Commitments

ML083330276
Person / Time
Site:	Oconee
Issue date:	11/18/2008
From:	Baxter D Duke Energy Carolinas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML083330276 (17)

Text

DA VE BAXTER Ener Vice President PC Energy, Oconee Nuclear Station Duke Energy Corporation ONO1 VP/7800 Rochester Highway Seneca, SC 29672 864-885-4460 November 18, 2008 864-885-4208 fax dabaxter@dukeenergy.com Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Subject:

Duke Energy Carolinas, LLC (Duke)

Oconee Nuclear Station, Units 1, 2, and 3 Docket Numbers 50-269, 50-270, and 50-287, Renewed Operating Licenses DPR-38, DPR-47, and DPR-55 Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments

References:

1. Letter to the Nuclear Regulatory Commission from Henry B.

Barron (Duke) dated November 30, 2006, "Tornado/HELB Mitigation Strategies and Regulatory Commitments."

2. Letter to the Nuclear Regulatory Commission from Bruce H. Hamilton (Duke) dated June 28, 2007, "Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments."

3. Letter to the Nuclear Regulatory Commission from Henry B. Barron (Duke) dated January 25, 2008, "Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments."

The purpose of this letter is to notify the Nuclear Regulatory Commission (NRC) of revisions to the commitments provided in Reference 1 in accordance with the provisions of Commitments 1OT and 25H. Adjustments to two of the commitments in Reference 1 were previously provided to the NRC in Reference

2. Subsequently adjustments were made to several tornado and HELB commitments in Reference 3. The commitments from Reference 3, including the revisions discussed herein, have been updated and are provided in Attachments 1 and 2. The revised commitments are provided below:

1) Commitment 1T The due date has been revised to May 2009 to reflect the impact of contractor quality issues and the resulting work stoppage that occurred during the modification implementation phase.

I www. duke-energy. corn

Nuclear Regulatory Commission Revisions to Tornado/HELB Mitigation Strategies and Regulatory Commitments November 18, 2008 Page 2

2) Commitment 14T The due date has been revised to June 2009 due to increases in scope for the wall testing program. Earlier test results revealed that shrinkage cracking in the vertical mortar joints along the infill masonry wall sides and inadequate bedding of the horizontal mortar joint along the wall top must be addressed to fully develop the capability of the fiber-reinforced polymer system. The test program has been expanded to include conventionally-designed, out-of-plane structural steel restraints to compensate for these wall edge conditions. The design, procurement, and implementation of activities associated with the Natural Phenomena Barrier System are being performed in parallel with this licensing activity. Consequently, the completion date for commitment 5T has not been revised.

3) Commitments completed since Reference 3 was submitted:

3T, 7T, 2H (Unit 1), 6H (Unit 1), and 22H.

Other than the changes to these commitments, the status of the remaining commitments remains on schedule. Inquiries concerning this matter should be directed to Stephen C. Newman of the Oconee Regulatory Compliance Group at (864) 885-4388.

Very truly yours, Dav Baxter, Site Vice President, Oconee Nuclear Station Attachments:

1. Tornado commitments table

2. HELB commitments table

Nuclear Regulatory Commission Revisions to Tornado/HELB Mitigation Strategies and Regulatory Commitments November 18, 2008 Page 3 cc:

Mr. Luis Reyes Regional Administrator U.S. Nuclear Regulatory Commission - Region II Sam Nunn Atlanta Federal Center, 23 T85 61 Forsyth St., SW Atlanta, GA 30303-8931 Mr. Leonard N. Olshan Senior Project Manager Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 0-8 G9A 11555 Rockville Pike Rockville, Maryland 20852-2738 Mr. Timothy McGinty Deputy Director Division of Operator Reactor Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, Maryland 20852-2738 Mr. Joseph Giitter Director Division of Operator Reactor Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, Maryland 20852-2738 Mr. Len Wert Director, DRP U.S. Nuclear Regulatory Commission - Region II Sam Nunn Atlanta Federal Center, 23 T85 61 Forsyth St., SW Atlanta, GA 30303-8931

Nuclear Regulatory Commission Revisions to Tornado/HELB Mitigation Strategies and Regulatory Commitments November 18, 2008 Page 4 Mr. Steven Rose Chief, Branch 1, DRP U.S. Nuclear Regulatory Commission - Region II Sam Nunn Atlanta Federal Center, 23 T85 61 Forsyth St., SW Atlanta, GA 30303-8931 Mr. Robert E. Carroll U.S. Nuclear Regulatory Commission - Region II Sam Nunn Atlanta Federal Center, 23 T85 61 Forsyth St., SW Atlanta, GA 30303-8931 Mr. Andy Hutto NRC Senior Resident Inspector Oconee Nuclear Station Susan E. Jenkins, Manager, Infectious and Radioactive Waste Management, Bureau of Land and Waste Management Department of Health & Environmental Control 2600 Bull Street, Columbia, SC 29201

Nuclear Regulatory Commission Revisions to Tornado/HELB Mitigation Strategies and Regulatory Commitments November 18, 2008 Page 5 bcc:

R. A. Jones R. J. Freudenberger T. P. Gillespie, Jr.

R. Mike Glover B. G. Davenport J. R. Sumpter T. D. Brown L. M. Kanipe S. L. Nader L. F. Vaughn S. L. Batson J. E. Burchfield G. K. Mc Aninch J. E. Smith (NRC Commitment Coordinator)

S. C. Newman R. E. Hall T. D. Mills R. L. Gill - NRI&IA R. D. Hart-CNS K. L. Ashe - MNS D. Repka NSRB, EC05N ELL, ECO50 File - T.S. Working ONS Document Management Tornado Commitments No.

Commitment Completion Date 1T Physically protect the Unit 3 Control Room north wall from 05-2009 the effects of a tornado per associated UFSAR Class 1 structure tornado wind, differential pressure, and missile criteria.

2T Physically protect the Standby Shutdown Facility (SSF)

Complete diesel fuel vents from the effects of a tornado per associated UFSAR SSF tornado wind, differential pressure and missile criteria.

3T Analyze and/or protect as required, the elevated/exposed Complete portions (at the north end of the Standby Shutdown Facility

[SSF] and where the SSF and CT-5 trenches intersect) of the SSF cable/pipe trench from the effects of a tornado per associated UFSAR SSF tornado wind, differential pressure and missile criteria.

4T Analyze and protect as required, each unit's Borated 12-2010 Water Storage Tank and associated piping per the UFSAR Class 1 structure tornado wind, differential pressure, and missile criteria.

5T Improve the protection of tornado mitigation equipment 12-2010 located within the West Penetration Room (WPR) and Cask Decontamination Tank Room (CDTR) from the effects of a tornado. The CDTR block walls will be upgraded to Regulatory Guide 1.76, Rev. 1 tornado differential pressure criteria using Fiber Reinforced Polymer. (Loads generated by the design tornado wind will be resisted by external siding and transferred directly into the reinforced concrete frame of the Auxiliary Building via structural steel members.) Duke will evaluate the need for additional missile protection of the CDTR/WPR walls using TORMIS.

6T Submit a License Amendment Request (LAR) to use Fiber Complete Reinforced Polymer (FRP) technology for application in strengthening selected masonry walls against the effects of tornado wind and differential pressure. The LAR will commit to utilizing technical procedures to control testing

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Commitment Completion Date of concrete substrate and installation and inspection of the FRP systems and in-service inspection of the FRP system once installed.

7T Submit a License Amendment Request (LAR) establishing Complete a new tornado licensing basis (LB) and mitigation strategy.

The LAR will address the two redundant mitigation systems, Standby Shutdown Facility (SSF) and Protected Service Water/High Pressure Injection (PSW/HPI) used in the tornado mitigation strategy.

The LAR will commit to the following and include information concerning:

" The use of TORMIS to collectively assess certain SSCs (with the exception of the Keowee Hydro Units (KHU)) that support the Secondary Side Decay Heat Removal (SSDHR), Reactor Coolant Pump (RCP)

Seal Injection or Reactor Coolant System (RCS) pressure boundary functions in the first 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> after the event that are not currently protected in accordance with UFSAR tornado missile criteria.

" The elimination of credit for the Spent Fuel Pool to High Pressure Injection (HPI) pump flow path.

In accordance with the CLB, single active failures will

-not be assumed in the updated tornado mitigation strategy.

• A description of the upgrade of the current low pressure Auxiliary Service Water (ASW) system to a high head PSW system that can be actuated, aligned, and controlled from the main Control Rooms (CR) for SSDHR. This system will be credited for both tornado and HELB events.

" The ASW upgrade also includes the installation of new PSW switchgear with alternate power provided from the KHUs via a tornado protected, underground feeder path. The PSW switchgear and supporting equipment will be located in a new tornado protected building. Power will also be provided from the Central/Lee 100kV transmission line through a new transformer that will be located to further minimize concurrent damage of the station switchyard, KHU

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Commitment Completion Date and the new transformer.

Specifically, the modification will provide alternate power for:

1. The PSW/HPI system itself,

2. An HPI pump for RCP seal injection that can be promptly aligned from the main CRs,

3. A sufficient number of pressurizer (PZR) heaters (also operated from the main CRs) to maintain a steam bubble in the PZR for RCS pressure

control,

4. The existing vital instrumentation and control battery chargers,

5. The SSF SSCs in case the SSF diesel generator is unavailable,

6. RCS High Point Vent and Reactor Vessel Head Vent valves for boration and RCS inventory control. At least one high point vent is required to control RCS inventory at Safe Shutdown conditions.

8T Installation of the PSW/HPI modifications.

12-2010 9T A program will be developed to monitor site missile Complete inventories.

1 OT Verbally notify in advance the Deputy Director, Division of As Reactor Licensing of the NRC, followed by a written necessary, communication, of significant changes in the scope and/or until 12-completion dates of the commitments in Attachment 1 of 2014 this submittal. The notification will include the reason for the changes and the modified commitments and/or schedule.

11T Installation of Main Steam Isolation Valve modifications.

Unit 1 -

12-2012 12T Unit 2 -

13T 12-2014 Unit 3 -

12-2013

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Commitment Completion Date 14T Submit a License Amendment Request (LAR) to use Fiber 06-2009 Reinforced Polymer (FRP) technology for application in strengthening the West Penetration Room (WPR) brick walls against the effects of tornado differential pressure using Regulatory Guide 1.76, Rev. 1 criteria. (Loads generated by the design tornado wind will be resisted by external siding and transferred directly into the reinforced concrete frame of the Auxiliary Building via structural steel members.) The LAR will commit to utilizing technical

>w procedures to control testing of concrete substrate and installation and inspection of the FRP systems and in-service inspection of the FRP system once installed. The suitability and design of FRP to strengthen brick walls like those of the WPR for tornado differential pressure loading will be based upon testing.

High Energy Line Break Commitments No.

Commitment Completion Date HELB Piping Inspection Program 1 H Implement an inspection program that ensures the Complete Auxiliary Building Main Steam and Main Feedwater girth and accessible attachment welds are re-inspected at least once during each subsequent 10 year ASME Section XI In-service Inspection interval for weld flaws and thickness.

2H Implement an inspection program that ensures the Unit 1, following welds are re-inspected at least once during each Complete subsequent 10 year ASME Section XI In-service Inspection interval for weld flaws and thickness:

a. Other Auxiliary Building high energy piping critical 12-2008 crack locations at welds.

Unit 3, 06-2009 3H Complete initial ASME Section XI In-service Inspection Complete interval ultrasonic testing of the Auxiliary Building Main Steam and Main Feedwater girth welds and accessible attachment welds for weld flaws and thickness.

Accessible attachment welds are to undergo visual examination for general weld quality as well as surface examination using either a magnetic particle or a liquid penetrant test.

4H Complete initial ASME Section XI In-service Inspection 03-2012 interval ultrasonic testing of the following welds for weld flaws and thickness. Accessible attachment welds are to undergo visual examination for general weld quality as well as surface examination using either a magnetic particle or a liquid penetrant test:

a. Other Auxiliary Building high energy piping critical crack locations at welds.

5H Implement an inspection program that ensures that Complete accessible piping base metal downstream of Main Feedwater isolation valves located in the East Penetration Room and not enclosed by the guard pipe receive an

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Commitment Completion Date ASME Section XI In-service Inspection interval ultrasonic testing inspection at least once every 10 years.

6H Implement an inspection program that ensures the Unit 1, following piping base metal receive an ASME Section XI Complete In-service Inspection interval ultrasonic testing inspection Unit 2, at least once every 10 years.

a. Other Auxiliary Building high energy piping critical 12-2008 crack locations not at welds.

Unit 3, 06-2009 7H Complete the initial ASME Section XI In-service Inspection Complete interval ultrasonic testing inspection of piping base metal downstream of Main Feedwater isolation valves located in the East Penetration Room and not enclosed by the guard pipe.

8H Complete initial ASME Section XI In-service Inspection 03-2012 interval ultrasonic testing inspection of the following piping base metal:

a. Other Auxiliary Building high energy piping critical crack locations not at welds.

9H Implement an inspection program that requires external Complete visual inspection of accessible attachment welds at the terminal ends inside the main feedwater guard pipe at least once every 10 years.

10H Complete initial visual inspections of accessible Complete attachment welds at the terminal ends inside the main feedwater guard pipes.

Repair of Electrical Penetration Enclosures Located in the EPR to the Correct Configuration 11H Inspect and repair the Unit 2 East Penetration Room Complete electrical penetration termination enclosures to their correct configuration. Missing and/or damaged covers, gaskets, and fasteners will be repaired or replaced.

12H Inspect and repair the Unit 1 East Penetration Room Complete electrical penetration termination enclosures to their

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Commitment Completion Date correct configuration. Missing and/or damaged covers, gaskets, and fasteners will be repaired or replaced.

1 3H Inspect and repair the Unit 3 East Penetration Room Complete electrical penetration termination enclosures to their correct configuration. Missing and/or damaged covers, gaskets, and fasteners will be repaired or replaced.

1 4H Create an inspection plan to select a portion of Units 1, 2 Complete and 3 en *closures to open and inspect for signs of internal debris and.corrosion.

1 5H Revise station procedures and processes as needed to Complete ensure penetration termination enclosures are maintained in their correct configurations.

EPR Flood Prevention Modifications 1 6H Complete the design and installation of flood outlet Complete devices for the Unit 1 East Penetration Room.

1 7H Complete the design and installation of flood outlet Complete devices for the Unit 2 East Penetration Room.

1 8H Complete the design and installation of flood outlet Complete devices for the Unit 3 East Penetration Room.

1 9H Complete the design and installation of flood Complete impoundment and exterior door flood improvement features for the Unit 1 East Penetration Room 20H Complete the design and installation of flood Complete impoundment and exterior door flood improvement features for the Unit 2 East Penetration Room.

21 H Complete the design and installation of flood Complete impoundment and exterior door flood improvement features for the Unit 3 East Penetration Room.

HELB Design and Licensing Basis Reconstitution 22H Submit License Amendment Requests (LARs) to Unit 1 23H establish an updated HELB Licensing Basis and HELB Complete mitigation strategy for Oconee Nuclear Station (ONS).

Unit 2, TheLARs will address deviations from and

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No.

Commitment Completion Date 24H clarifications of selected portions of References 6 (the 12-2008 Giambusso letter) and 7 (the Schwencer letter) and the Unit 3, criteria that will be substituted or clarified. Each unit LAR will include licensing basis changes based on 06-2009 design basis documents replacing OS 73.2.

The first LAR will commit to the following and will also provide the analysis results for Unit 1.

The LAR will outline the basic elements of Selected Licensee Commitment changes to ensure licensing basis clarity and component operability such that HELB mitigation capability is maintained.

The LAR will identify any Turbine Building (TB) high energy piping girth welds and critical crack locations at welds whose failure would result in adverse interactions impacting the ability to achieve safe shutdown (SSD) or cold shutdown (CSD), as appropriate, following a HELB event.

The LAR will identify any TB high energy critical crack locations not at welds whose failure would result in adverse interactions impacting the ability to achieve SSD or CSD, as appropriate, following a HELB event.

The LAR will identify any crack locations in high energy piping other than Main Steam and Main Feedwater in the Auxiliary Building (AB) per the criteria in Commitments 22H-24H. These locations are referenced in Commitment #'s 2H, 4H, 6H and 8H as "other AB high energy piping critical crack locations".

" High energy systems will be defined as those systems with operating temperatures greater than or equal to 200 F or pressures greater than 275 psig. For those systems that operate at high energy conditions less than 1% of the total plant operating time or at high energy conditions less than 2% of the total system operating time, no breaks or cracks will be postulated.

" For piping that is seismically analyzed, i.e. stress analysis information is available and the analysis includes seismic loadina. intermediate breaks will

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Commitment Completion Date be postulated in equivalent Class 2 or 3 piping at axial locations where the calculated stress for the applicable load cases exceed 0.8(SA + Sh).

Applicable load cases include internal pressure, dead weight (gravity), thermal, and seismic (defined as operational basis earthquake, OBE).

Intermediate breaks will not be postulated at locations where the expansion stress exceeds 0.8SA. Thermal stress is a secondary stress, and taken in absence of other stresses, does not cause ruptures in pipe. This approach is permitted by GL 87-11 as a deviation from Reference 6.

For piping that is not rigorously analyzed or does not include seismic loadings, intermediate breaks will be postulated at locations as provided in BTP MEB 3-1 (Section B.1.c(2)(b)(i)). This MEB 3-1 section provides more detail than the associated requirements in Reference 6, as amended by Reference 7, so that the most adverse locations can be identified as required in these references.

Terminal ends are vessel/pump nozzles, building penetrations, in-line anchors, and branch to run connections that act as essentially rigid constraints to piping thermal expansion. A branch appropriately modeled in a rigorous stress analysis with the run flexibility and applied branch line movements included and where the branch connection stress is accurately known will use the stress criteria noted above for postulating break locations as noted above in the 6 th bullet. For unanalyzed branch connections or where the stress at the branch connection is not accurately known, break locations will be postulated as noted in the 7 th bullet above.

Reference 6, as amended by Reference 7, provided criteria to determine pipe break orientation at break locations and specifies that longitudinal breaks in piping runs and branch runs be postulated for nominal pipe sizes greater than or equal to four inches. Circumferential breaks are to be postulated at the terminal ends. The design of existing and potentially new rupture restraints may

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Commitment Completion Date be used to mitigate the results from such breaks, including prevention of pipe whip and alteration of the break flow. For ONS, longitudinal breaks will not be postulated at terminal ends.

For piping that is seismically analyzed (i.e. stress analysis information is available and the analysis includes seismic loading), critical cracks will be postulated in equivalent Class 2 or 3 piping at axial locations where the calculated stress for the applicable load cases exceed O.4 (SA + Sh).

Applicable load cases will include internal pressure, dead weight (gravity), thermal and seismic (defined as operational basis earthquake, OBE). This approach is in accordance with BTP MEB 3-1 (Section B.1.e(2)) which is deviation from the requirements of Reference 7.

" For piping that is not rigorously analyzed or does not include seismic loadings, critical cracks will not be postulated since the effects of postulated circumferential and longitudinal breaks at these locations will bound the effects from critical cracks (See the 7 th bullet above).

" Actual stresses used for comparison to the break and crack thresholds noted above will be calculated in accordance with the ONS piping code of record, USAS B31.1.0. (1967 Edition) Allowable stress values SA and Sh will be determined in accordance with the USAS B31.1.0 or the USAS B31.7 (February 1968 draft edition with errata) code as appropriate.

" Moderate energy line breaks will not be postulated.

Moderate energy rules were not in place when ONS was licensed and built and the effect of moderate energy cracks have not been evaluated.

• Systems and-components not required to reach SSD, but necessary to reach CSD, will not be protected from HELBs. Station repair guidelines will be employed to effect repairs as required to those systems and components necessary to reach CSD. The affected unit will remain at SSD conditions while those necessary repairs are

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Commitment Completion Date completed. Current damage repair guidelines and procedures will be enhanced, as necessary, to extend SSD capability beyond the 72-hour Current Licensing Basis (CLB) and to establish CSD. The enhanced capability will not be part of the CLB or related to operability of the Standby Shutdown Facility (SSF).

A single active failure will be postulated in the Protected Service Water/High Pressure Injection (PSW/HPI) or SSF systems for the initial event mitigation as well as achieving and maintaining SSD. Single active failures will not be postulated during plant cooldown to CSD. The LAR will include a provision to continue reliance on the CLB regarding application of the single failure criteria to the letdown piping.

" Onsite emergency power distribution systems located in the TB will not be credited for mitigation of HELBs that could occur in the TB. New switchgear, to be installed as part of the PSW system, along with the SSF will be utilized for mitigation of HELBs that could occur in the TB.

" The new PSW and the East Penetration Room flood prevention modifications will be designed and constructed to the quality standards applicable to a safety-related system.

" A new time critical action will be created for the operators to place the PSW system into operation within 15 minutes following a complete loss of main and emergency feedwater with a complete loss of 4160 VAC power. A single HPI pump can be aligned to the Borated Water Storage Tank and started to reestablish seal cooling for the reactor coolant pumps. A new time critical action will be created for the operators to place HPI into operation (from PSW power) within 20 minutes following a complete loss of 4160 VAC power. The new time critical actions will be time validated in accordance with the current ONS standards for emergency procedures. The operator would then maintain SSD conditions and energize pressurizer heaters as necessary to maintain reactor coolant

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Commitment Completion Date pressure within limits.

An analysis that shows that SSD can be maintained with a failed open MSIV.

25H Verbally notify in advance the Deputy Director, Division of As Reactor Licensing of the NRC, followed by a written necessary, communication, of significant changes in the scope and/or until 12-2014 completion dates of the commitments in Attachment 3 to (Note: month this submittal. The notification will include the reason for changedto the changes and the modified commitments and/or agree with schedule.

.commitment 1OT)