ML052090182
| ML052090182 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 08/15/2005 |
| From: | Marshall M NRC/NRR/DLPM/LPD2 |
| To: | Stall J Florida Power & Light Co |
| Moroney B, NRR/DLPM, 415-3974 | |
| References | |
| TAC MC7338 | |
| Download: ML052090182 (12) | |
Text
August 15, 2005 Mr. J. A. Stall Senior Vice President, Nuclear and Chief Nuclear Officer Florida Power and Light Company P.O. Box 14000 Juno Beach, Florida 33408-0420
SUBJECT:
TURKEY POINT NUCLEAR PLANT, UNIT 4 - SAFETY EVALUATION FOR RELIEF REQUEST REGARDING MECHANICAL CLAMPING DEVICE ON PRESSURE BOUNDARY PIPING (TAC NO. MC7338)
Dear Mr. Stall:
By a letter dated June 20, 2005, Florida Power and Light Company (the licensee) requested relief from certain provisions of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) for Turkey Point Unit 4. Pursuant to Title 10 of the Code Federal Regulation (10 CFR) Section 50.55a(a)(3)(ii), the request proposed to deviate from the requirements of Appendix IX, Article IX-1000, Paragraph (c)(2), which prohibits the use of clamping devices on . . . portions of a piping system that forms the containment boundary.
The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the licensees proposed alternative and has concluded that the licensee has provided an acceptable alternative to the requirements of Appendix IX of ASME Code,Section XI. Furthermore, the staff finds that performance of an immediate Code repair would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Therefore, pursuant to 10 CFR 50.55(a)(3)(ii), the alternative is authorized for the Turkey Point Nuclear Plant, Unit 4, until the next scheduled outage exceeding 30 days, but no longer than the next refueling outage. At that time a Code repair shall be performed.
Verbal authorization of the requested relief was granted in a telephone conversation between the NRC staff and licensee representatives on June 21, 2005. Participants in the call included Michael Marshall, Terence Chan and Eva Brown of the NRC staff, and Michael Pearce and Walter Parker of the Turkey Point staff.
The NRC staff also notes that, following verbal authorization, the mechanical clamping device was installed on June 21, 2005. It was subsequently removed and the piping was repaired in accordance with the ASME Code during a plant outage that occurred from June 27 through July 13, 2005.
J. Stall Further details on the bases for the NRC staffs conclusions regarding use of the mechanical clamping device at Turkey Point Unit 4 are contained in the enclosed safety evaluation. If you have any questions regarding this issue, please feel free to contact Brendan Moroney at (301) 415-3974.
Sincerely,
/RA/
Michael L. Marshall, Jr., Chief, Section 2 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-251
Enclosure:
Safety Evaluation cc: See next page
ML052090182 NRR-028 OFFICE PDII-2/PM PDII-2/LA EMCB/SC OGC PDII-2/SC NAME BMoroney BClayton TChan by JHull MMarshall memo DATE 07/ 28 /05 07/ 28 /05 07/21/05 08/ 08 /05 08/ 15 /05 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST TO USE A CLAMPING DEVICE ON PRESSURE BOUNDARY PIPING FLORIDA POWER AND LIGHT TURKEY POINT NUCLEAR PLANT, UNIT 4 DOCKET NO. 50-251
1.0 INTRODUCTION
By letter dated June 20, 2005, Florida Power and Light (FPL, the licensee) requested, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Section 50.55a(a)(3)(ii), relief from certain American Society of Mechanical Engineers (ASME) Code,Section XI, requirements related to repair of a small pinhole leak on a 1-inch line for the 4A steam generator liquid sample system at its Turkey Point Nuclear Plant, Unit 4. The licensee proposed to deviate from the requirements of Appendix IX, Article IX-1000, paragraph (c)(2),
which prohibits the use of clamping devices on . . . portions of a piping system that forms the containment boundary. Instead, the licensee proposed to use a clamping device to stop the leak and to monitor the sump level logs every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to ensure that the leak is not recurring.
2.0 REGULATORY EVALUATION
It specifies in 10 CFR 50.55a(g) that inservice inspection (ISI) of nuclear power plant components shall be performed in accordance with the requirements of the ASME Boiler and Pressure Vessel Code (Code),Section XI, except where specific written relief has been granted by the U.S. Nuclear Regulatory Commission (NRC) pursuant to 10 CFR 50.55a(g)(6)(i).
Alternatives to the requirements of paragraph (g) may be used when authorized by the NRC, pursuant to 10 CFR 50.55a(a)(3), if (i) the proposed alternatives would provide an acceptable level of quality and safety or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Furthermore, 10 CFR 50.55a(g)(5)(iii) states that if the licensee has determined that conformance with certain code requirements is impractical for its facility, the licensee shall notify the Commission and submit, as specified in 10 CFR 50.4, information to support the determinations.
Turkey Point Unit 4 is currently in the fourth 10-year ISI inspection interval. The 1998 Edition of ASME Code,Section XI through 2000 Addenda, governs the current repair/replacement activities at Turkey Point Unit 4.
Enclosure
3.0 TECHNICAL EVALUATION
3.1 Licensees Evaluation 3.1.1 ASME Code Component Affected The affected elbow is in the 4A steam generator blowdown sample line.
Pipe is 1 inch Schedule 80 (min), SA/A A106 Grade B (carbon steel). Fittings are 3000 lb forged steel socket weld SA/A 105. Code of record: ANSI [American National Standards Institute] B31.1 Code Class 2.
Design temperature and pressure: 600°F and 1085 psig.
3.1.2 Applicable Code Edition and Addenda ASME Code,Section XI, the 1998 edition through the 2000 Addenda 3.1.3 Applicable Code Requirement for Which a Deviation is Requested ASME Code,Section XI, paragraph IWA-4133, Mechanical Clamping Devices Used as Piping Pressure Boundary, and Section XI, Appendix IX, Article IX-1000, paragraph (c)(2).
3.1.4 Reason for Request Article IX-1000, paragraph (c) of Appendix IX to ASME Code Section XI limits the use of clamping devices. Paragraph (c)(2) states that piping and associated components that form the containment boundary are excluded. FPL requests a deviation from this provision to allow repair of the leaking socket weld inside containment on the 4A steam generator blowdown sample line. This line is part of a closed system in containment and is considered an extension of the containment boundary. All other provisions of ASME Code,Section XI, Paragraph IWA-4133 and Appendix IX will be met.
The mechanical clamping device that will be used will comply with all Code requirements with the exception that it will be located on system piping that is considered a containment boundary.
Discussions with industry experts indicate that the basis for this scope limitation is to prevent temporary repair of containment boundaries, which could depressurize and have the potential for communication with the postaccident environment inside containment.
The mechanical clamping device will reside within the boundary of a containment isolation feature that incorporates the use of a "closed system." The normal operating pressure at the location of the mechanical clamping device is in the range of 800-1000 psig. As such, positive verification of the leak-tight integrity of the mechanical clamping device will be continuously ascertained, as leakage during operation will be detected by indirect methods, such as elevated containment sump levels. These parameters are monitored as required by plant Technical Specifications, and confirmed to be effective by detection of the existing leak using that method.
The use of a mechanical clamping device on a portion of a closed system which is considered a containment boundary is acceptable based on the device being continuously pressurized at
greater than 10 times containment design pressure, and leakage during operation would be detected by degraded system performance or other indirect methods.
Review of assumed accidents that involve the potential release of radioactive fluids, as described in Chapter 14 of the Turkey Point Updated Final Safety Analysis Report (UFSAR),
indicates that the steam generators remain pressurized above the containment atmosphere, preventing any communication between the subject line and the containment environment.
Furthermore, the location of the proposed repair is at a low elevation relative to the steam generator ensuring that the line will remain water-solid as long as the steam generator is not faulted. A faulted steam generator concurrent with an accident that can cause release of radioactivity to containment is outside the plant design and licensing basis.
Since the affected piping cannot be isolated during plant operation, it would be necessary to shut down Unit 4 in order to effect a permanent ASME Code repair. This creates a hardship in that the shutdown and subsequent restart unnecessarily cycles plant systems and components.
FPL would prefer to use paragraph IWA-4133 to perform a temporary ASME Code repair using a mechanical clamping device as a replacement for the piping pressure boundary containing the leak. Based on the above discussion, FPL requests approval of a deviation from the provision in Article IX-1000, paragraph (c)(2) regarding the use of clamping devices on piping that forms the containment boundary in that compliance would result in hardship without a compensating increase in the level of quality or safety.
3.1.5 Temporary Repair Method Article IX-6000, Monitoring Requirements, of Appendix IX to ASME Code Section XI requires a monitoring plan for defect growth immediately adjacent to the clamp. Article IX-6000, paragraph (b), allows a specific exemption for circumferential defects that are self-limiting with respect to maximum growth. Article IX-2000 states that, if the defect size cannot be directly determined, a conservative bound of the size shall be determined and documented.
Visual examination identifies the existing leak size as a pinhole and has placed the defect at the toe of the socket weld to the affected elbow. There is no indication of degradation to the piping wall thickness. On those bases, the defect can be conservatively characterized as residing within the socket weld and any growth would be limited to the weld itself, effectively limiting the impact of the defect to that of a circumferential crack.
The requirement of Article IX-6000, paragraph (c), to monitor the clamping device for leakage on a weekly basis will be fulfilled by continuous monitoring of the containment (reactor) sump levels for any indication of increasing leakage, supplemented by visual inspection during any planned containment entry.
Encapsulating the elbow with an ASME Code clamping device will repair the leak. The clamp device includes an axial restraint to accommodate thrust loads resulting from a complete failure of the welded connection of concern. The clamp device has been designed to meet or exceed the design rating of the associated piping. A piping stress review has been completed to ensure that the additional mass does not adversely affect the qualification of the existing piping system. As discussed above, the repair device has been designed in full compliance with the requirements of Article IX-3000 and materials have been specified in accordance with Article IX-4000. Therefore, the subject temporary leak repair enclosure and clamp are suitable
for the intended application and capable of performing the specified design functions. As the defect is located in a weld zone, the repair enclosure completely surrounds the subject fitting, and the enclosure design will accommodate full circumferential severance of the socket weld at the defect location.
3.1.6 Monitoring Plan Leakage monitoring of the degraded piping will be accomplished using the same containment sump level instrumentation that identified the leak. The Turkey Point Unit 4 containment is provided with diverse sump level indication consisting of nonsafety, quality-related and safety-related systems. The nonsafety-related sump level transmitter, LS-4-1538, provides control room indication and alarm functions. The sump level chart recorder provides a means for continuous monitoring by the Operations staff. Control room Operators are required to record readings every shift (8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />). The design of the chart recorder is such that any small change in rate is readily apparent. This level instrument also provides output to the plant network and the stored data is routinely analyzed by the System Engineers and Shift Technical Advisors.
Therefore, the monitoring plan will be accomplished using the Reactor Operator logs (once every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />) and weekly review by the System Engineers, supplemented by visual inspection during any planned containment entry.
In addition to the sump level indication described above, there is a quality-related monitoring system consisting of two redundant systems, LI-6308A and B. Each system is provided with two level indicators for an indicating range from the bottom of the containment sump to approximately the 22-foot level inside containment.
The safety-related wide-range sump level indicators, LI-6309A and B, satisfy the requirements of NUREG-0578, TMI-2 Lessons Learned Task Force Report, for containment water level monitors. These level transmitters have a range of 90 inches and indicate water level above the 14-foot level of the containment building.
3.1.7 Duration of Proposed Alternative A permanent repair will be performed during the next scheduled Unit 4 outage requiring entry into Mode 5. If a Unit 4 shutdown to Mode 3 is scheduled for a sufficient duration to effect the repair, FPL will make the repair if adequate isolation from the secondary system can be obtained. The permanent repair will be made no later than the next Unit 4 refueling outage.
FPL plans to install a clamping device in accordance with the design requirements of ASME Code Section XI, Appendix IX, Article IX-3000. Materials and pressure testing will satisfy the requirements of Articles IX-4000 and IX-5000 of Appendix IX to ASME Code Section XI.
3.2 Staff Evaluation The staff reviewed the information provided by the licensee in support of its request to use a clamping device to implement a temporary repair on a leak at Turkey Point Unit 4.
The licensee is proposing to use a mechanical clamping device that will comply with all ASME Code requirements with the exception that it will be located on system piping that is considered a containment pressure boundary. The clamping device has been designed in full compliance with the requirements of ASME Code,Section XI, Article IX-3000 and materials have been specified in accordance with Article IX-4000. The design of the clamp device also meets or exceeds the design rating of the associated piping. Because the clamping device meets all design and materials requirements of ASME Code,Section XI, the licensee concluded that the use of the clamp is an acceptable temporary leak repair method, and that the clamp is suitable for the intended application and capable of performing its specified design functions.
The staff agrees with the licensees conclusion that the clamping device is suitable for the intended application because the clamping device meets the requirements of ASME Code,Section XI. Compliance with the requirements of ASME Code Section XI provides an acceptable level of quality and safety.
The licensee is proposing to install the clamping device on piping that is a part of the containment pressure boundary. The Code prohibits the use of clamping devices on containment pressure boundary piping because of concerns that temporary clamping devices may not be able to prevent interaction between the affected line and containment atmosphere during accident conditions. The licensee has addressed this concern by showing that the clamping device will reside within the boundary of a containment isolation feature that is considered a closed system. The normal operating pressure at the location of the mechanical clamping device is in the pressure range of 800-1000 psig. The licensees review of UFSAR Chapter 14 assumed accidents that involve the potential release of radioactive fluids, indicates that the steam generators remain pressurized above the containment atmosphere and thus prevent any interaction between the subject line and the containment environment. Further, the location of the proposed repair is at a low elevation relative to the steam generator ensuring that the line will remain water-solid during accident conditions.
Also, the high operating pressure at the location of the clamping device will provide positive verification of the leak-tight integrity of the device, which will be continuously ascertained because leakage during operation will be detected by the monitoring systems that monitor the containment sump levels. The containment sump level parameters are monitored as required by the plant Technical Specifications, which are confirmed to be an effective method to detect leaks. The monitoring will be accomplished using the Reactor Operator logs (once every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />) and weekly review by the System Engineers, supplemented by visual inspection during any planned containment entry.
The licensee has also stated that a permanent ASME Code repair is not possible during plant operation because the affected piping cannot be isolated and, therefore, the plant would need to be shut down in order to perform the permanent Code repair. This creates a hardship in that the shutdown and subsequent restart unnecessarily cycles plant systems and components.
Therefore, requiring the licensee to shut down the plant to do a permanent Code repair would result in hardship without a compensating increase in the level of quality or safety.
The staff finds the licensees reasoning in support of its request to install a clamping device on containment pressure boundary (steam generator blowdown sample line) acceptable because the licensee has demonstrated that the containment environment during accident condition
would remain unchanged as a result of installation of the clamping device. This is based on the fact that the licensees review of UFSAR Chapter 14 assumed accidents showed that the steam generators would remain pressurized above the containment atmosphere and, thus, prevent any interaction between the clamped line and the containment environment.
Also, because the clamping device would be located on a closed system having normal operating pressure that is significantly higher than the normal operating containment pressure, interaction between the clamped line and the containment environment is unlikely. Further, the staff finds that requiring the licensee to perform a permanent ASME Code repair would impose a hardship because the affected piping cannot be isolated and, therefore, the plant would need to be shut down in order to perform the permanent Code repair. Requiring the plant to be shut down for repair is not in the public interest and safety, taking into consideration the alternative that the licensee has proposed, because the shutdown and subsequent restart would unnecessarily cycle plant systems and components.
4.0 CONCLUSION
Based on the information provided in the licensees submittal, the NRC staff concludes that the licensee has provided an acceptable alternative to the requirements of Appendix IX of ASME Code,Section XI. Furthermore, the staff finds that performance of an immediate Code repair would constitute an undue burden (create undue hardship) upon the licensee without a compensating increase in the level of quality and safety since it would result in the shutdown of the plant. In this case, plant shutdown is not in the best interest of public safety, given the magnitude of the flaw and the licensees temporary repair and monitoring provisions.
Therefore, pursuant to 10 CFR 50.55a(a)(3)(ii) the alternative is authorized for the Turkey Point Nuclear Plant, Unit 4, until the next scheduled outage exceeding 30 days, but not beyond the next refueling outage. At that time a Code repair shall be performed.
All other ASME Code,Section XI, requirements for which relief was not specifically requested and authorized herein by the NRC staff remain applicable, including third party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: George Georgiev Date: August 15, 2005
Mr. J. A. Stall TURKEY POINT PLANT Florida Power and Light Company cc:
M. S. Ross, Managing Attorney Attorney General Florida Power & Light Company Department of Legal Affairs P.O. Box 14000 The Capitol Juno Beach, FL 33408-0420 Tallahassee, Florida 32304 Marjan Mashhadi, Senior Attorney Michael O. Pearce Florida Power & Light Company Plant General Manager 801 Pennsylvania Avenue, NW. Turkey Point Nuclear Plant Suite 220 Florida Power and Light Company Washington, DC 20004 9760 SW. 344th Street Florida City, FL 33035 T. O. Jones, Site Vice President Turkey Point Nuclear Plant Walter Parker Florida Power and Light Company Licensing Manager 9760 SW. 344th Street Turkey Point Nuclear Plant Florida City, FL 33035 9760 SW 344th Street Florida City, FL 33035 County Manager Miami-Dade County Mark Warner, Vice President 111 Northwest 1 Street, 29th Floor Nuclear Operations Support Miami, Florida 33128 Florida Power and Light Company P.O. Box 14000 Senior Resident Inspector Juno Beach, FL 33408-0420 Turkey Point Nuclear Plant U.S. Nuclear Regulatory Commission Mr. Rajiv S. Kundalkar 9762 SW. 344th Street Vice President - Nuclear Engineering Florida City, Florida 33035 Florida Power & Light Company P.O. Box 14000 Mr. William A. Passetti, Chief Juno Beach, FL 33408-0420 Department of Health Bureau of Radiation Control 2020 Capital Circle, SE, Bin #C21 Tallahassee, Florida 32399-1741 Mr. Craig Fugate, Director Division of Emergency Preparedness Department of Community Affairs 2740 Centerview Drive Tallahassee, Florida 32399-2100