ML022400191
| ML022400191 | |
| Person / Time | |
|---|---|
| Site: | McGuire  |
| Issue date: | 08/26/2002 |
| From: | John Nakoski NRC/NRR/DLPM/LPD2 |
| To: | Barron H Duke Energy Corp |
| Martin R, NRR/DLPM, 415-1493 | |
| References | |
| TAC MB5327 | |
| Download: ML022400191 (8) | |
Text
August 26, 2002 Mr. H. B. Barron Vice President, McGuire Site Duke Energy Corporation 12700 Hagers Ferry Road Huntersville, NC 28078-8985
SUBJECT:
MCGUIRE NUCLEAR STATION, UNIT 1, RE: RELIEF REQUEST NO.02-001 (TAC NO. MB5327)
Dear Mr. Barron:
By letter dated May 23, 2002, Duke Energy Corporation (the licensee) requested that the U.S.
Nuclear Regulatory Commission staff grant relief from certain requirements of the American Society of Mechanical Engineers, Boiler and Pressure Vessel Code,Section XI, regarding leakage at bolted connections at McGuire Nuclear Station, Unit 1 for the third inspection interval.
The staff has reviewed the information provided for this relief request. The staffs evaluation and conclusion are provided in the Enclosure. Based on the information provided in the relief request, the staff concludes that your proposed alternative will provide an acceptable level of quality and safety. Therefore, the proposed alternative is authorized pursuant to Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a(a)(3)(i) for the third inspection interval for inservice inspection at McGuire Nuclear Station, Unit 1.
Sincerely,
/RA by L.Olshan Acting for/
John A. Nakoski, Chief, Section 1 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket Nos. 50-369
Enclosure:
As stated cc w/encl: See next page
ML022400191 OFFICE PDII-1:PM PDII-1:LA OGC/NLO
- PDII-1:SC NAME RMartin CHawes RHoefling JNakoski DATE 08/22/02 08/21/02 08/13/02 08/22/02
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION THIRD 10-YEAR INTERVAL INSERVICE INSPECTION REQUEST FOR RELIEF 02-001 MCGUIRE NUCLEAR STATION, UNIT 1 DUKE ENERGY CORPORATION DOCKET NO. 50-369
1.0 INTRODUCTION
The inservice inspection of American Society of Mechanical Engineers (ASME) Code Class 1, 2, and 3 components is to be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code (Code) and applicable addenda as required by Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). 10 CFR 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if the licensee demonstrates that (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.
Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the pre-service examination requirements, set forth in ASME Code,Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable edition of Section XI of the ASME Code for the third 10-year interval for McGuire, Unit 1 is the 1995 Edition with the 1996 Addenda.
By the letter dated May 23, 2002, Duke Energy Corporation, the licensee for McGuire Nuclear Station, Unit 1 submitted a request for relief (No.02-001) from the requirements of the ASME Code,Section XI, 1995 Edition with the 1996 Addenda, Subsection IWA-5250(a)(2) regarding the removal of bolting and performance of a VT-3 visual examination for degradation if leakage occurs at a bolted connection during the conduct of a system pressure test. The licensees alternative would allow stoppage of leakage at the bolted connection or, if leakage is 1The acceptance criteria for Visual, VT-1 will be used to assess the acceptability of the bolting.
not stopped, would require that the connection be evaluated for joint integrity in accordance with specified criteria. The staff has reviewed and evaluated the licensees request for relief pursuant to 10 CFR 50.55a(a)(3)(i).
2.0 LICENSEES EVALUATION The Components for Which Relief is Requested All Class 1, 2, and 3 systems/components subject to IWA-5000 pressure testing.
Requirement From Which Relief is Requested Section XI of the ASME Code, 1995 Edition with 1996 Addenda, Subsection IWA 5250(a)(2) states, If leakage occurs at a bolted connection, on other than a gaseous system, one of the bolts shall be removed, VT-3 examined, and evaluated in accordance with IWA-3100. The bolt selected shall be the one closest to the source of the leakage. When the removed bolt has evidence of degradation, all remaining bolting in the connection shall be removed, VT-3 examined, and evaluated in accordance with IWA-3100.
Proposed Alternative When leakage is identified at bolted connections by Visual, VT-2 examination during system pressure testing, an evaluation will be performed to determine the susceptibility of the bolting to corrosion and to assess the potential for failure as stated in Code Case N-566-2.
The evaluation will consider the following factors:
- 1. the number and service age of the bolts;
- 2. bolt and component material;
- 3. corrosiveness of process fluid;
- 4. leakage location and system function;
- 5. leakage history at connection or other system components; and
- 6. visual evidence of corrosion at the assembled connection.
When the evaluation of the above variables is concluded and the evaluation determines that the leaking condition has not degraded the fasteners, then no further action is necessary. However, reasonable attempts to stop the leakage shall be taken.
If the evaluations of the variables above indicate the need for further evaluation, or no evaluation is performed, then a bolt closest to the source of leakage shall be removed and VT-31 visually examined. When the removed bolting shows evidence of rejectable degradation, all remaining bolts in the connection shall be removed and VT-3 visually examined. If the leakage is identified when the bolted connection is in service or Technical Specifications require it to be operable, and the information in the evaluation is supportive, the removal of the bolt for VT-3 visual examination may be deferred to the next component/system outage of sufficient duration.
Licensees Basis for Requesting Relief Removal of pressure retaining bolting at mechanical connections for visual, VT-3 examination and subsequent evaluation in locations where leakage has been identified is not always the most discerning course of action to determine the acceptability of the bolting. The Code requirement to remove, examine, and evaluate bolting in this situation does not allow the owner to consider other factors which may indicate the acceptability of mechanical joint bolting.
Other factors that should be considered when evaluating bolting acceptability when leakage has been identified at a mechanical joint include, but are not limited to: joint bolting material, service age of joint bolting materials, location of the leakage, history of leakage at the joint, evidence of corrosion with the joint assembled, and corrosiveness of process fluid.
Performance of the pressure test while the system is in service may identify leakage at a bolted connection that, upon evaluation, may conclude the integrity and pressure retaining ability of the joint is not challenged. It would not be prudent to impact the availability of a safety system by removing the system from service to address a leak that does not challenge the systems ability to perform its safety function.
A situation frequently encountered at Duke Energy Corporation is the complete replacement of bolting materials (studs, bolts, nuts, washers, etc.) at mechanical joints during plant outages. When the associated system piping is pressurized during plant start up, leakage may be identified at these joints. The root cause of this leakage is most often due to thermal expansion of the piping and bolting materials and subsequent fluid seepage at the joint gasket. Proper retorquing of the bolting, in most cases, stops the leakage. Removal of the bolting to evaluate for corrosion would be unwarranted in this situation due to the new condition of the bolting materials.
2.1 Staff Evaluation In accordance with the 1995 Edition, with the 1996 Addenda of the ASME Code,Section XI, when leakage occurs at bolted connections, one of the bolts shall be removed, VT-3 examined, and evaluated in accordance with IWA-3100. In lieu of the Code-required removal of bolting to perform a VT-3 visual examination, the licensee has proposed to perform an evaluation of the bolted connection to determine the susceptibility of the bolting to corrosion and the potential for failure.
Most leakage at bolted connections is caused by thermal expansion of the piping and bolting materials and subsequent fluid seepage at the joint gasket. Therefore, proper torquing of the bolting, in most cases, would stop the leakage. Following stoppage of a leak, the bolting and component material will be evaluated to determine the susceptibility of the bolting to corrosion and failure considering all of the following factors:
- 1. the number and service age of the bolts
- 2. bolt and component material
- 3. corrosiveness of process fluid
- 4. leakage location and system function
- 5. leakage history at connection or other system components
- 6. visual evidence of corrosion at the assembled connection If the evaluation determines that the leaking condition has not degraded the fasteners, then no further action is necessary. If the initial evaluation indicates the need for a more in-depth evaluation, the bolt closest to the source of leakage will be removed, VT-3 examined, and evaluated in accordance with IWA-3100. In a situation where a leakage is not stopped, the licensee indicated it would evaluate the structural integrity of the bolting, the consequences of continued operation and the effect on the system operability of continued leakage along with the considerations of the above six factors. Such an evaluation will be the basis for deferral of removing the bolt closest to the source of leakage to the upcoming outage. This alternative allows the licensee to utilize a systematic approach and sound engineering judgement, provided that, as a minimum, all of the six evaluation factors listed in the licensees proposed alternative are considered. This proposed alternative engineering evaluation considers all the factors necessary to identify degradation of the bolts in any leaking bolted connection. Accordingly, the use of this type of engineering evaluation is expected to result in the identification of such degradation and corrective actions when appropriate and avoids unnecessary joint disassembly when the bolts are fit for service. As a result, the licensees alternative to the Code-required removal of bolting at a joint when leakage occurs will provide an acceptable level of quality and safety since the integrity of the joint will be maintained.
The licensee noted that if a bolt has to be removed, it will perform a VT-3 examination and use VT-1 acceptance criteria. It is appropriate to apply VT-1 acceptance criteria to bolting since there are no VT-3 acceptance criteria in the Code applicable to bolting.
This alternative to the requirements of ASME Code, 1995 Edition with the 1996 Addenda, Subsection IWA-5250(a)(2) is consistent with ASME Code Case N-566-2.
3.0 CONCLUSION
Based on the NRC staffs review of the information provided in the request for relief (Relief Request 02-001), the staff concludes that the licensees proposed alternative to the requirements of Subsection IWA-5250(a)(2) at McGuire, Unit 1 is a technically sound engineering approach and will provide an acceptable level of quality and safety by ensuring the integrity of bolted connections. Therefore, the proposed alternative is authorized for the third 10-year inservice inspection interval of McGuire, Unit 1 pursuant to 10 CFR 50.55a(a)(3)(i).
Principal Contributor: Nathan T. Sanfilippo Date: August 26, 2002
McGuire Nuclear Station cc:
Ms. Lisa F. Vaughn Legal Department (PBO5E)
Duke Energy Corporation 422 South Church Street Charlotte, North Carolina 28201-1006 County Manager of Mecklenburg County 720 East Fourth Street Charlotte, North Carolina 28202 Michael T. Cash Regulatory Compliance Manager Duke Energy Corporation McGuire Nuclear Site 12700 Hagers Ferry Road Huntersville, North Carolina 28078 Anne Cottingham, Esquire Winston and Strawn 1400 L Street, NW.
Washington, DC 20005 Senior Resident Inspector c/o U.S. Nuclear Regulatory Commission 12700 Hagers Ferry Road Huntersville, North Carolina 28078 Dr. John M. Barry Mecklenburg County Department of Environmental Protection 700 N. Tryon Street Charlotte, North Carolina 28202 Mr. Peter R. Harden, IV VP-Customer Relations and Sales Westinghouse Electric Company 6000 Fairview Road 12th Floor Charlotte, North Carolina 28210 Ms. Karen E. Long Assistant Attorney General North Carolina Department of Justice P. O. Box 629 Raleigh, North Carolina 27602 Mr. C. Jeffrey Thomas Manager - Nuclear Regulatory Licensing Duke Energy Corporation 526 South Church Street Charlotte, North Carolina 28201-1006 Elaine Wathen, Lead REP Planner Division of Emergency Management 116 West Jones Street Raleigh, North Carolina 27603-1335 Mr. Richard M. Fry, Director Division of Radiation Protection North Carolina Department of Environment, Health and Natural Resources 3825 Barrett Drive Raleigh, North Carolina 27609-7721 Mr. T. Richard Puryear Owners Group (NCEMC)
Duke Energy Corporation 4800 Concord Road York, South Carolina 29745