ML101400144
| ML101400144 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 05/18/2010 |
| From: | Baxter D Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML101400144 (14) | |
Text
P Duke Energye DAVE BAXTER Vice President Oconee Nuclear Station Duke Energy ON01 VP / 7800 Rochester Highway Seneca, SC 29672 May 18, 2010 864-873-4460 864-873-4208 fax dave.baxter@duke-energy.com Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Subject:
Duke Energy Carolinas, LLC 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."
- 4. Letter to the Nuclear Regulatory Commission from Dave Baxter (Duke) dated November 18, 2008, "Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments."
This letter documents Duke Energy Carolinas, LLC (Duke Energy) notification to the Nuclear Regulatory Commission (NRC) of revisions to tornado and high energy line break (HELB) mitigation strategy commitments in accordance with the provisions of commitments 1OT and 25H in reference 1. The bases for these changes were discussed in detail during a meeting with NRC management on April 22, 2010. In addition to the commitment change adjustments outlined in this submittal, earlier adjustments are documented in references 2 through 4 above. As required by commitments 1OT and 25H, the following written communication information is being provided to describe the changes to the mitigation strategy schedule.
Due primarily to engineering product and equipment supplier quality performance, project schedule impacts have occurred to several commitments associated with the Natural Phenomena Barrier System (NPBS) modifications and installation of the Protected Service Water (PSW) system. The Main Steam Isolation Valve (MSIVs) project was also impacted because it is sequenced after the NPBS and PSW projects. The commitments involved are 4T, 5T, 8T, 11T, 12T, 13T, as well as 10T and 25H. Commitment 10T has been extended to align with the completion of the MSIV project. Commitment 25H has been administratively closed since it redundant to commitment 1OT. The remaining project related commitments are being tracked as "T" commitments. The revised status of the comr www. duke-energy,
Nuclear Regulatory Commission Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments May 18, 2010 Page 2 tornado and HELB commitments from the November 30, 2006, commitment letter are given in the enclosure to this letter.
Duke Energy remains committed to the completion of these projects and recognizes their contribution to resolution of outstanding tornado, HELB, and fire protection regulatory issues as well as their significant positive impact on the station's probabilistic risk assessment margin. Duke acknowledges that challenging schedules are required to complete the PSW and NPBS projects; however, our priorities are safety, quality and good plans.
If you have any questions in regard to this letter, please contact Stephen C. Newman, Regulatory Compliance Lead Engineer, Oconee Nuclear Station, at (864) 873-4388.
Sincerely, Dave Ba ter, Site Vice President, Oconee Nuclear Station Enclosure
Nuclear Regulatory Commission Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments May 18, 2010 Page 3 cc (w/enclosure):
Mr. J. F. Stang, Project Manager Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 0-14 H25 Washington, D. C. 20555 Mr. L. A. Reyes, Regional Administrator U. S. Nuclear Regulatory Commission - Region II Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, GA 30303-1257 Mr. Andy Sabisch NRC Senior Resident Inspector Oconee Nuclear Station S. E. Jenkins, Manager Infectious and Radioactive Waste Management Section 2600 Bull Street Columbia, SC 29201
Enclosure Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments
Enclosure:
Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments No. Tornado.(T) COmmmitments Complete Cue Date (YIN ___
1T Physically protect the Unit 3 Control Room north wall from the Y 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) diesel Y 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 Y 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 Water N 7-2011 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 located N 7-2011 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 CDTRJWPR walls using TORMIS.
6T Submit a License Amendment Request (LAR) to use Fiber Y 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 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 a Y 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:
Enclosure:
Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments N.Tornado (T) Commitments Complete 'Due bate No~f ___ _ _Y/N)
(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 and the new transformer.
Specifically, the modification will provide alternate power for:
- 1. The PSW/HPI system itself,
- 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.
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Enclosure:
Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments N.Trado (T) Commitments Complete. Due Date (YIN) 8T Installation of the PSW/HPI modifications. N 7-2012 9T A program will be developed to monitor site missile inventories. Y _
1OT Verbally notify in advance the Deputy Director, Division of N As Reactor Licensing of the NRC, followed by a written Necessary communication, of significant changes in the scope and/or Until completion dates of the commitments in Attachment 1 of this 7-2016 submittal. The notification will include the reason for the changes and the modified commitments and/or schedule.
11T Installation of Main Steam Isolation Valve (MSIV) N Ul: 12-2014 12T modifications. N U2: 12-2015 N U3: 07-2016 13T 14T Submit a License Amendment Request (LAR) to use Fiber Y -
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 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.
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Enclosure:
Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments No. High Energy Line Break (H) Commitments, Complete Due (YIN) Date 1H Implement an inspection program that ensures the Y 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 Y following welds are re-inspected at least once during each subsequent 10 year ASME Section Xl In-service Inspection interval for weld flaws and thickness:
- a. Other Auxiliary Building high energy piping critical crack locations at welds.
3H Complete initial ASME Section XI In-service Inspection Y 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 Xl In-service Inspection Y 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 Y 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 ASME Section XI In-service Inspection interval ultrasonic testing inspection at least once every 10 years.
6H Implement an inspection program that ensures the following piping base metal receive an ASME Section Xl In-service Inspection interval ultrasonic testing inspection at least once every 10 years.
- a. Other Auxiliary Building high energy piping critical crack locations not at welds.
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Enclosure:
Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments No. .. High Energy Line Break (H) Commitments. Complete Due
____(YIN) Date, 7H Complete the initial ASME Section Xl In-service Y Inspection 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 Xl In-service Inspection Y 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 Y 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 Y attachment welds at the terminal ends inside the main feedwater guard pipes.
11H Inspect and repair the Unit 2 East Penetration Room Y 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 Y electrical penetration termination enclosures to their correct configuration. Missing and/or damaged covers, gaskets, and fasteners will be repaired or replaced.
13H Inspect and repair the Unit 3 East Penetration Room Y electrical penetration termination enclosures to their correct configuration. Missing and/or damaged covers, gaskets, and fasteners will be repaired or replaced.
14H Create an inspection plan to select a portion of Units 1, Y 2 and 3 enclosures to open and inspect for signs of internal debris and corrosion.
15H Revise station procedures and processes as needed to Y ensure penetration termination enclosures are maintained in their correct configurations.
16H Complete the design and installation of flood outlet Y -
devices for the Unit 1 East Penetration Room.
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Enclosure:
Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments No.] High Energy Line Break (H)Commitments- Complete IDue
____ fYIN) ] Date 17H Complete the design and installation of flood outlet Y devices for the Unit 2 East Penetration Room.
18H Complete the design and installation of flood outlet Y devices for the Unit 3 East Penetration Room.
19H Complete the design and installation of flood Y impoundment and exterior door flood improvement features for the Unit 1 East Penetration Room 20H Complete the design and installation of flood Y impoundment and exterior door flood improvement features for the Unit 2 East Penetration Room.
21H Complete the design and installation of flood Y -
impoundment and exterior door flood improvement features for the Unit 3 East Penetration Room.
22H Submit License Amendment Requests (LARs) to Y 23H -establish an updated HELB Licensing Basis and HELB mitigation strategy for Oconee Nuclear Station (ONS).
24H The LARs will address deviations from and clarifications of selected portions of References 6 (the Giambusso letter) and 7 (the Schwencer letter) and the criteria that will be substituted or clarified. Each unit LAR will include licensing basis changes based on 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 hi qh Page 6
Enclosure:
Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments No.**, HghEnergy Line Break:(H) Commitments [Complete[ Due
___I (Y/N) [Date 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 #Ws2H, 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 loading, intermediate breaks will 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. 8 SA. 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 Page 7
Enclosure:
Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments aDove in me 0- DUlie. r-or unanaiyzea Drancn 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 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 7h 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 Shwill 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 Page 8
Enclosure:
Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments No. ~HighEnergy Line Break (H) Commitments Cmlt J(YN),
1 Dateý 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 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 Page 9
'I
Enclosure:
Revision to Tornado/HELB Mitigation Strategies and Regulatory Commitments with the current UNb standards tor emergency procedures. The operator would then maintain SSD conditions and energize pressurizer heaters as necessary to maintain reactor coolant 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 Y of Reactor Licensing of the NRC, followed by a written.
communication, of significant changes in the scope and/or completion dates of the commitments in Attachment 3 to this submittal. The notification will include the reason for the changes and the modified commitments and/or schedule.
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