ML070740586
| ML070740586 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 05/01/2007 |
| From: | Chernoff H NRC/NRR/ADRO/DORL/LPLI-2 |
| To: | Christian D Dominion Nuclear Connecticut |
| nerses V, NRR//DORL, 415-1484 | |
| References | |
| IR-2-42, RR-89-58, TAC MD1715, TAC MD1716 | |
| Download: ML070740586 (8) | |
Text
May 1, 2007 Mr. David A. Christian Sr. Vice President and Chief Nuclear Officer Dominion Nuclear Connecticut, Inc.
Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711
SUBJECT:
MILLSTONE POWER STATION, UNIT NOS. 2 AND 3 RELIEF REQUESTS RR-89-58 AND IR-2-42 FOR RELIEF FROM THE 10-YEAR REACTOR VESSEL EXAMINATIONS REQUIREMENTS (TAC NOS. MD1715 AND MD1716)
Dear Mr. Christian:
By letter dated May 11, 2006, [Agency Documents Access and Management System (ADAMS) accession number ML061530137] Dominion Nuclear Connecticut, Inc. (DNC) submitted to the U.S. Nuclear Regulatory Commission (NRC), Relief Requests RR-89-58 and IR-2-42 for approval to use alternatives to the examination requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI at the Millstone Power Station, Unit Nos. 2 and 3 (MPS2 and MPS3). Specifically, DNC proposes to use an alternative through wall depth sizing criteria for ASME Code,Section XI, Appendix VIII, Supplements 2, 3, and 10, when examining components from the inside surface. The relief is requested pursuant to Title 10 of the Code of Federal Regulations (10 CFR),
Section 50.55a(a)(3)(i).
Based upon the review of the information you provided, the NRC concluded that the proposed alternative provides reasonable assurance of a satisfactory through wall depth sizing criteria, and the NRC finds that the use of this sizing criteria provides an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), your proposed alternative is authorized for the remainder of the third 10-year inservice inspection (ISI) interval at MPS2 and the second 10-year ISI interval at MPS3. The NRC staffs Safety Evaluation is enclosed. If you have any questions, please contact the project manager, John Hughey at (301) 3204.
Sincerely,
/ra/
Harold K. Chernoff, Chief Plant Licensing Branch I-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-336 and 50-423
Enclosure:
As stated cc: See next page
LPLI-2/BC NAME VNerses RSola JHughey TChan
- MBaty HChernoff DATE 3/27/2007 3/27/2007 4/24/2007 2/14/07 4/24/2007 5/1/07
Millstone Power Station, Unit Nos. 2 and 3 cc:
Lillian M. Cuoco, Esquire Senior Counsel Dominion Resources Services, Inc.
Building 475, 5th Floor Rope Ferry Road Waterford, CT 06385 Edward L. Wilds, Jr., Ph.D.
Director, Division of Radiation Department of Environmental Protection 79 Elm Street Hartford, CT 06106-5127 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 First Selectmen Town of Waterford 15 Rope Ferry Road Waterford, CT 06385 Charles Brinkman, Director Washington Operations Nuclear Services Westinghouse Electric Company 12300 Twinbrook Pkwy, Suite 330 Rockville, MD 20852 Senior Resident Inspector Millstone Power Station c/o U.S. Nuclear Regulatory Commission P. O. Box 513 Niantic, CT 06357 Mr. J. W. "Bill" Sheehan Co-Chair NEAC 19 Laurel Crest Drive Waterford, CT 06385 Ms. Nancy Burton 147 Cross Highway Redding Ridge, CT 00870 Mr. Evan W. Woollacott Co-Chair Nuclear Energy Advisory Council 128 Terrys Plain Road Simsbury, CT 06070 Mr. Joseph Roy Director of Operations Massachusetts Municipal Wholesale Electric Company P.O. Box 426 Ludlow, MA 01056 Mr. David W. Dodson Licensing Supervisor Dominion Nuclear Connecticut, Inc.
Building 475, 5th Floor Roper Ferry Road Waterford, CT 06385 Mr. J. Alan Price Site Vice President Dominion Nuclear Connecticut, Inc.
Building 475, 5th Floor Rope Ferry Road Waterford, CT 06385 Mr. Chris L. Funderburk Director, Nuclear Licensing and Operations Support Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUESTS RR-89-58 AND IR-2-42 MILLSTONE POWER STATION, UNIT NOS. 2 AND 3 DOMINION NUCLEAR CONNECTICUT, INC.
DOCKET NUMBERS 50-336 AND 50-423
1.0 INTRODUCTION
By letter dated May 11, 2006, Dominion Nuclear Connecticut, Inc. (DNC) submitted to the U.S. Nuclear Regulatory Commission (NRC, or the Commission), Relief Requests RR-89-58 and IR-2-42 for approval to use alternatives to the examination requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI at the Millstone Power Station, Unit Nos. 2 and 3 (MPS2 and MPS3). Specifically, in Relief Requests RR-89-58 and IR-2-42, DNC proposes to use an alternative through wall depth sizing criteria for ASME Code,Section XI, Appendix VIII, Supplements 2, 3, and 10, when examining components from the inside surface. The relief is requested pursuant to Title 10 of the Code of Federal Regulations (10 CFR), Section 50.55a(a)(3)(i).
2.0 REGULATORY EVALUATION
Inservice Inspection (ISI) of ASME Code Class 1, 2, and 3 components is to be performed in accordance with Section XI of the ASME Code and applicable edition and addenda as required by 10 CFR 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). As stated, in part, in 10 CFR 50.55a(a)(3), 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 the ASME Code,Section XI, "Rules for ISI 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 in 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 ISI Code of Record for the third 10-year ISI interval for MPS2 and the second 10-year ISI interval for MPS3 is the 1989 Edition of the ASME Code,Section XI. In addition, 10 CFR 50.55a(g)(6)(ii)(C)(2) requires that licensees using the 1989 Edition or earlier editions must implement the 1995 Edition with the 1996 Addenda of Appendix VIII and the supplements to Appendix VIII of Section XI of the ASME Code.
3.0 EVALUATION FOR RELIEF REQUEST NOS. RR-89-58 AND IR-2-42 3.1 Components for Which Relief is Requested Relief is requested for the following nozzle to transition piece welds at MSP2:
Weld ID Description Internal Diameter (inches)
Wall Thickness (inches)
P-5-C-1-A Inlet nozzle to transition piece (RC loop 1A) 30 3.6 P-3-C-1-A Inlet nozzle to transition piece (RC loop 1B) 30 3.6 P-14-C-1-A Inlet nozzle to transition piece (RC loop 2A) 30 3.6 P-18-C-1-A Inlet nozzle to transition piece (RC loop 2B) 30 3.6 P-1-C-1-A Inlet nozzle to transition piece (RC loop 1) 42 3.6 P-10-C-1-A Outlet nozzle to transition piece (RC loop 2) 42 3.6 The base materials of the above components are SA-533-65, Grade B, Class 1 and SA-515 GR 70 carbon steel (with cladding). The weld is ferritic carbon steel (with cladding).
In addition relief is requested for the following Nozzle-to-Safe end welds at MSP3:
Weld ID Description Internal Diameter (inches)
Wall Thickness (inches) 301-121-A Inlet nozzle to safe end (RC loop 3) 27.5 2.32 301-121-B Inlet nozzle to safe end (RC loop 4) 27.5 2.32 301-121-C Inlet nozzle to safe end (RC loop 1) 27.5 2.32 301-121-D Inlet nozzle to safe end (RC loop 2) 27.5 2.32 302-121-A Outlet nozzle to safe end (RC loop 3) 29 2.45 302-121-B Outlet nozzle to safe end (RC loop 4) 29 2.45 302-121-C Outlet nozzle to safe end (RC loop 1) 29 2.45 302-121-D Outlet nozzle to safe end (RC loop 2) 29 2.45 The base materials of the above components are SA-508 Class 2 and SA-182 F316. The weld metal is austenitic stainless steel.
3.2 Code Requirements MPS2 is currently in its third 10-year ISI interval and MPS3 is currently in its second 10-year ISI interval. The applicable Code edition and addenda is the 1989 Edition of the ASME Code,Section XI. In addition, as required by 10 CFR 50.55a, ASME Code,Section XI, 1995 Edition with 1996 Addenda is used for Appendix VIII, Performance Demonstration for Ultrasonic Examination Systems.
The 1995 Edition with 1996 Addenda, ASME Code,Section XI, Appendix VIII, Supplement 2, paragraph 3.2(b), states, The RMS [root mean square] error of the flaw depths estimated by ultrasonics, as compared with the true depths, shall not exceed 0.125 in.
Appendix VIII, Supplement 3, Section 3.2, addresses the sizing criteria for ferritic piping welds.
It states in part, Qualification of examination procedures, equipment, and personnel for ferritic pipe examination shall be accomplished by satisfying the requirements of Supplement 2...
Appendix VIII, Supplement 10, Section 3.2(b), addresses the sizing criteria for dissimilar metal piping welds. It states, Examination procedures, equipment, and personnel are qualified for depth sizing when the RMS error of the flaw depth measurements as compared to the true flaw depths, is less than or equal to 0.125 in.
3.3 Licensees Proposed Alternative and Basis To date, although qualified for detection and length sizing on the subject welds, the examination vendors have not met the established root mean square error (RMS) requirement for depth sizing (0.125 inches). The licensees examination vendor has achieved an RMS value of 0.224 inches instead of the required value of 0.125 inches.
The licensee proposes to use the demonstrated 0.224 inches instead of the 0.125 inches specified for depth sizing. In the event an indication is detected that requires depth sizing, the 0.099-inch difference between the required RMS value and the demonstrated RMS value (0.224 inches - 0.125 inches = 0.099 inches) will be added to the measured through-wall extent for comparison with the applicable acceptance criteria. If the examination vendor demonstrates an improved depth sizing RMS value prior to the examination, the excess of the improved RMS value over the 0.125-inch RMS requirement, if any, will be added to the measured value for comparison with the applicable acceptance criteria.
Adding the difference of the actual RMS value and the required RMS value (0.125 inches) to the estimated flaw depths measured will compensate for the actual RMS value being larger than the allowable RMS value.
The examination vendors are qualified for detecting axial flaws on surfaces that are machined or ground smooth with no root reinforcement or counterbore. If surface roughness is experienced during the examination it could affect the qualification and the detection of axial flaws in the volume immediately under the surface. Therefore, ultrasonic profilometry will be used to assess surface areas, if any, where roughness may limit the ability of the ultrasonic examination to be applied as qualified through the performance demonstration. The licensee will supplement the ultrasonic examinations in these areas with eddy current examination. Use of profilometry and eddy current techniques will assure that any axial flaws in the near surface volume that could be missed by ultrasonic examination due to surface roughness are detected and sized.
3.4
NRC Staff Evaluation
Supplements 2, 3, and 10 of Appendix VIII to ASME Code,Section XI requires that examination procedures, equipment, and personnel meet specific criteria for flaw depth sizing accuracy.
The Code specifies that the maximum error of flaw depth measurements, as compared to the true flaw depths must be less than or equal to 0.125-inch RMS. The industry is in the process of qualifying personnel to meet Appendix VIII supplements as implemented by the Performance Demonstration Initiative Program. However, for demonstrations performed from the inside surface of a pipe weldment, personnel have been unsuccessful at achieving the 0.125-inch RMS depth sizing criterion.
To compensate for the larger RMS in flaw sizing, the licensee proposed that, in the event that a flaw is identified during the examination of the subject welds, the licensee will add 0.099 inches which is the difference of the demonstrated sizing error and the code-required RMS of 0.125-inches to the measured flaw depth. The staff has determined that this approach is acceptable because it provides a reasonable adjustment to the measured flaw depth in flaw evaluation to ensure structural integrity and provides an acceptable level of quality and safety.
In addition, the licensee proposes to use ultrasonic profilometry on surfaces where roughness may limit the ability of the ultrasonic examination to be applied as qualified through the PDI program. As an alternative, the licensee will use a surface geometry profiling technique to identify locations which lack transducer contact. An eddy current technique will then be used to supplement the ultrasonic procedure at these locations. The eddy current probe will provide data from areas with irregular surface conditions. The licensee will use the eddy current examination to supplement the ultrasonic examination of the volume immediately under the surface of the subject welds with sufficient surface roughness which may challenge the applicability of the ultrasonic examination qualification to detect axial flaws. This technique proposed by the licensee has been demonstrated and blind tested by the industry in recent years. The staff finds that this portion of the licensees proposed alternative, which combines ultrasonic testing and eddy current techniques in examining for axial flaws in areas with irregular surface conditions, will provide an acceptable level of detectability and sensitivity.
3.5 Summary Based on the NRC staffs evaluation of the licensees proposal as discussed above, the NRC staff finds that the licensees proposed alternative will provide reasonable assurance of structural integrity of the subject welds.
4.0 C0NCLUSION The staff has reviewed the information provided by the licensee and finds that the proposed alternative will provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the NRC staff authorizes the proposed alternative for the remainder of the third 10-year ISI interval at MPS2 and the second 10-year ISI interval at MPS3.
All other ASME Code,Section XI requirements for which relief was not specifically requested and approved remain applicable, including third party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: A. Keim Date: May 1, 2007