ML100560334
| ML100560334 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 03/02/2010 |
| From: | Kulesa G Plant Licensing Branch II |
| To: | Ajluni M Southern Nuclear Operating Co |
| Martin R, NRR/DORL, 415-1493 | |
| References | |
| TAC ME1124 FNP-ISI-ALT-08, Ver 1.0 | |
| Download: ML100560334 (10) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555*0001 March 2, 2010 Mr. Mark J. Ajluni Manager, Nuclear Licensing Southern Nuclear Operating Company, Inc 40 Inverness Center Parkway Birmingham, Alabama 35201
SUBJECT:
JOSEPH M. FARLEY NUCLEAR PLANT, UNIT 2, SAFETY EVALUATION OF RELIEF REQUEST FNP-ISI-ALT-08, VERSION 1.0, FOR REACTOR VESSEL NOZZLE TO SAFE-END DISSIMILAR METAL WELD AND ADJACENT AUSTENITIC SAFE-END WELD EXAMINATIONS (TAC NO. ME1124)
Dear Mr. Ajluni:
By letters to the U.S. Nuclear Regulatory Commission (NRC), dated April 22,2009, and February 23,2010, Southern Nuclear Operating Company, Inc. (SNC, the licensee) submitted request for relief FNP-ISI-ALT-08 from certain examination qualification requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code at the Joseph M.
Farley Nuclear Plant, Unit 2. By letter dated September 11,2009, SNC withdrew FNP-ISI-ALT 07 which had been included in the April 22, 2009 letter.
Based on the proposed alternatives and information provided in SNC's submittal, the NRC staff has determined that requiring the licensee to qualify procedures, personnel, and equipment to meet the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) required root mean square error (RMSE) for crack-depth sizing is not feasible at the present time. SNC's proposal to add the difference between the Code-required RMSE and the demonstrated RMSE to the measured through-wall extent, with the IWB-3500 acceptance standards, provides an acceptable level of quality and safety. Additionally, SNC's proposal to use surface geometry profiling combined with eddy current examination provides reasonable assurance that the axial flaws in the presence of rough surfaces will be detected, thus providing an acceptable level of quality and safety.
M. Ajluni
- 2 Therefore, relief is granted pursuant to 10 CFR 50.55a(3)(i) for the remainder of the fourth 1O-year inservice inspection interval. 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.
Sincerely,
()(~
Gloria Kulesa, Branch Chief Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-364
Enclosure:
Safety Evaluation cc w/encl: Distribution via Listserv
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO RELIEF REQUEST NUMBER Ft\\lP-ISI-ALT-08 FOURTH 10-YEAR INSERVICE INSPECTION INTERVAL SOUTHERN NUCLEAR OPERATING COMPANY, INC.
JOSEPH M. FARLEY NUCLEAR PLANT, UNIT 2 DOCKET NO. 50-364
1.0 INTRODUCTION
By letter dated April 22, 2009 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML091120752), supplemented by letter dated February 23, 2010 (ADAMS No. ML100550139), Southern Nuclear Operating Company (SNC, the licensee) submitted a request for relief from certain examination requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) at the Joseph M.
Farley Nuclear Plant (FNP), Unit 2. In the letter, the licensee requested, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(a)(3)(i), that the Nuclear Regulatory Commission (NRC) approve Relief Request FNP-ISI-ALT-08 that relates to the inservice inspection (lSI) of reactor vessel nozzle to safe-end dissimilar metal welds as well as the adjacent austenitic safe-end welds during the fourth 1O-year inservice inspection (lSI) interval which began on December 1, 2007, and is scheduled to end on November 30, 2017.
2.0 REGULATORY REQUIREMENTS The NRC regulations in 10 CFR 50.55a(g) specify that lSI of nuclear power plant components shall be performed in accordance with the requirements of the ASME Code,Section XI, except where specific written relief has been granted by the NRC pursuant to 10 CFR 50.55a(g)(6)(i).
10 CFR 50.55a(g)(6)(i) states that the NRC may grant such relief and may impose such alternative requirements as it determines is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest, given the consideration of the burden upon the licensee. 10 CFR 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, 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. 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 NRC and submit, as specified in Section 50.4, information to support the determinations.
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 preservice
- 2 examination requirements, set forth in the 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 lSI of components and system pressure tests conducted during the first 1a-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.
3.0 TECHNICAL EVALUATION
3.1
Applicable Code Edition and Addenda
The code of record for the fourth 1a-year lSI program at FNP, Unit 2, is the 2001 Edition through the 2003 addenda of the ASIVIE Code,Section XI. In addition, as required by 10 CFR 50.55a(b)(2)(xv), licensees who use later editions and addenda than the 2001 Edition of the ASME Code shall use the 2001 Edition of Appendix VIII, "Performance Demonstration for Ultrasonic Examinations Systems." The fourth 1a-year lSI interval for FNP, Unit 2, began on December 1, 2007, and is scheduled to end on November 30, 2017.
3.2 Components for Which Relief is Requested The affected components are the Class 1, Category B-F, Item B5.1 0, reactor pressure vessel nozzle to safe-end dissimilar metal (DM) butt welds and the adjacent Category B-J, Item B9.11, austenitic safe-end welds.
3.3
Applicable Code Requirement
ASIVIE Code,Section XI, IWB-2500, Examination Category B-F, "Pressure Retaining Dissimilar Metal Welds in Vessel Nozzles," Item B5.1 0, "Nozzle-to-Safe End Butt Welds" and Examination Category B-J, "Pressure Retaining Welds in Piping," Item B9.11, "Circumferential welds,"
specify volumetric examination. IWA-2232, "Ultrasonic Examination," requires that ultrasonic (UT) examinations be performed per Appendix I. Appendix I, 1-2220, requires that UT examination procedures, equipment, and personnel be qualified by performance demonstration in accordance with Appendix VIII.
3.3.1 Variation to 0.125 Root Mean Square Error (RMSE)
SNC states that, as an alternate to the ASME Code,Section XI, Appendix VIII, qualification requirements, it uses Code Case N-695, "Qualification Requirements for Dissimilar Metal Piping Welds" and Code Case N-696, "Qualification Requirements for Appendix VIII Piping Examinations Conducted from the Inside Surface" in its lSI program. This is permissible, in accordance with 10 CFR 50.55a(b), since these code cases have been included in Revision 15 of Regulatory Guide (RG)1.147 on lSI code case acceptability.
Code Case N-695, provides an alternative to the Appendix VIII, Supplement 10, qualification requirements for DM piping welds. Paragraph 3.3(c) indicates that examination procedures, equipment, and personnel are qualified for depth-sizing when the RMSE of the flaw depth measurements, as compared with the true depths, does not exceed 0.125 inches.
- 3 Code Case 1\\J-696, provides an alternative to the Appendix VIII, Supplements 10 and 2, qualification requirements for piping welds that are examined from the inside surface.
Paragraph 3.3(d) indicates that examination procedures, equipment, and personnel are qualified for depth-sizing when the RMSE of the flaw depth measurements, as compared to the true depths, does not exceed 0.125 inches.
3.3.2 Inside Diameter (10) Ultrasonic CUT) Examinations Supplemented by Eddy Current Relief from the qualification requirements of ASME Code,Section VIII, Supplements 10 and 2 pertaining to the detection of axially oriented flaws in the presence of surface roughness when performing UT examinations from the 10 surface.
3.4 Licensee Proposed Alternative and Basis for Use 3.4.1 Variation to 0.125 RMSE SNC stated that a request for relief from the required RMSE in depth sizing is needed because, to date, examination vendors have not met the established RMSE of 0.125 inch for depth-sizing.
SNC proposes to use a contracted examination vendor that has demonstrated ability to meet a depth sizing qualification requirement with an RMSE of 0.189 inch instead of the 0.125 inch required for Supplement 10 and an RMSE of 0.245 inch instead of the 0.125 inch for Supplements 10 and 2 combined.
SNC states that in the event an indication is detected that requires depth siZing, the difference between the required RMSE and the demonstrated RMSE will be added to the measured through-wall extent for comparison with applicable ASME Code,Section XI, acceptance criteria.
If the examination vendor demonstrates an improved depth-sizing RMSE prior to the examination, the excess of that improved RMSE over the 0.125 inch RMSE req uirement, if any, will be added to the measured value for comparison with applicable acceptance criteria.
3.4.2 Inside Diameter UT Examinations Supplemented by Eddy Current The following is extracted from SNC's alternative and basis, as described in its submittal:
SNC states that the examination vendor for the FNP reactor vessel nozzle examinations has qualified for detection of axial flaws in accordance with Appendix VIII, Supplements 10 and 2, as demonstrated through the Electric Power Research Institute (EPRI)
Performance Demonstration Initiative (POI) Program, for OM nozzle-to-safe end and austenitic safe-end welds examined from the inside diameter (10) surface provided the surface is machined or ground smooth with no exposed root reinforcement or counter bore. However, surface roughness may be present that could call into question the ultrasonic qualifications demonstrated for detection of axial flaws. SNC notes that the examination vendor has qualified for detection of circumferential flaws in accordance with Appendix VIII, Supplements 10 and 2, as demonstrated through the EPRI POI Program for DSM nozzle-to-safe end and austenitic safe-end welds examined from the 10 surface.)
SNC proposes using surface geometry profiling software (profilometry) in conjunction with a focused immersion ultrasonic transducer positioned to permit accurate profile data
-4 across the examination volume, to help the examiner confirm locations where the raw data indicates lack of transducer contact due to problematic surface geometry.
Subsequently, eddy current examination will be used to supplement ultrasonic [UT]
examination where there is sufficient surface roughness to call into question the applicability of the ultrasonic examination qualification to detect axial flaws. The ultrasonic examinations, supplemented by eddy current examinations and profilometry, will be conducted to the maximum extent practical. It is anticipated that all six DSM nozzle-to-safe-end welds and all six safe-end welds could be examined using this process.
To supplement the UT examinations for rough surface detection coverage, the following eddy current techniques will be utilized:
Up to two plus point probes applied circumferentially on the inside surface in scan increments of 0.08 inches circumferentially (for axial flaws) and 0.25 inches axially.
Automated systems for data collection and analysis.
The target flaw size for the eddy current procedure is 0.28 inches long, well within the ASME Code linear flaw acceptance standards of 0.45 inches for austenitic material, and 0.625 inches for ferritic material (defined for the outside surface in the Code Tables).
The eddy current technique was first used in the V. C. Summer reactor vessel primary nozzle examinations of 2000. The procedure was refined by applying it to the V. C. Summer hot-leg dissimilar metal weld section removed from service.
The removed section had a number of primary water stress corrosion cracking flaws along with non-relevant indications resulting from metallurgical interface and surface geometry. Using these actual flaws and geometric conditions in the removed section to refine the technique, the vendor developed reliable flaw screening criteria which allowed for the successful use of the procedure in the V. C. Summer 2002 and 2003 examinations.
Subsequently, the technique was successfully blind tested for the Swedish authority SQC Kvalificeringscentrum AS (SQC NOT Qualification Center) under the program, "Qualification of Equipment, Procedure and Personnel for Detection, Characterization and Sizing of Defects in Areas in Nozzle to Safe End Welds at Ringhals Unit 3 and 4," Hakan Soderstrand 7-10-03. The important qualification parameters for eddy current in the SQC blind tests (Ref. SQC Qualification Report No. 019AN03) were as follows:
Defect types: fatigue and stress corrosion cracks, surface initiated Tilt: +/-10 degrees; Skew: +/-10 degrees Detection target size: IDSCC 6mm (0.25 inches) long Flaw Location: within 10mm (13/32 inch)
Length of the planar flaw within a 70% confidence interval: +/- 9mm (3/8 inch)
False call rate: less than or equal to 20% for the personnel qualification tests
- 5 The use of ultrasonic profilometry and eddy current examination, with procedures and personnel qualified through the SOC blind tests to supplement Appendix VIII qualified ultrasonic procedures and personnel, provides additional assurance that surface-breaking flaws (that may be present) will be detected in the presence of potential surface roughness. This process will assure that there is reasonable assurance of structural integrity and thus, will provide an acceptable level of quality and safety. Permission is requested to use this process in accordance with 10 CFR 50.55a(a)(3)(i).
3.4.3 Duration of Proposed Alternative The proposed alternative is requested for the fourth 1a-year lSI interval for Unit 1 of FNP, which began on December 1, 2007, and is scheduled to end on November 30,2017.
4.0 STAFF EVALUATION 4.1 Variation to 0.125 RMSE ASME Code,Section XI, Appendix VIII, Supplement 10, states that examination procedures, equipment, and personnel are qualified for depth-sizing when the RMS error of the flaw depth measurements, as compared to true depths, do not exceed 0.125 inch. Supplement 2 also requires that the RMSE of the flaw depths estimated by ultrasonic examination, as compared with true depths, shall not exceed 0.125 in. Code Case N-696, which combines the requirements of Supplements 10 and 2, states that Supplement 2 examination procedures, equipment, and personnel are qualified for depth-sizing when the flaw depths estimated by ultrasonic examination, as compared with the true depth, do not exceed 0.125 inch RMS, when they are combined with a successful Supplement 10 qualification. (Note: Code Cases N-695 and N-696 are identified as Acceptable Section XI Code Cases in Revision 15 of the NRC RG 1.147, "Inservice Inspection Code Case Acceptability ASME Section XI, Division 1.")
The nuclear industry is in the process of qualifying personnel to Supplement 10 as implemented by the Performance Demonstration Initiative (POI) program. However, for demonstrations performed from the inside surface of a pipe weld, personnel have been unsuccessful at achieving the ASME Code-required 0.125 inch RMSE flaw depth-sizing criterion. At this time, the NRC staff concludes that achieving the 0.125 inch RMSE for depth-sizing does not appear to be feasible as personnel have only been capable of achieving an accuracy of 0.189 inch RMSE to size any detected flaws. The vendor contracted by the licensee has proposed to use an RMSE of 0.189 inch instead of the 0.125 inch required for supplement 10 and an RMSE of 0.245 inch instead of the 0.125 inch for Supplements 10 and 2 combined, as per approved Code Case N-696. In the event an indication is detected that requires depth-sizing, the difference between the required RMSE and the demonstrated RMSE (e.g., 0.245 inch - 0.125 inch =0.120 inch for Supplements 10 and 2 combined) will be added to the measured through wall extent. This total will then be assessed against the applicable acceptance criteria specified in ASME Code,Section XI, IWB-3500 for flaw evaluation. Additionally, the licensee proposes that, if the examination vendor demonstrates an improved depth-sizing RMSE prior to the examination, the excess of that improved RMSE over the 0.125 inch RMSE requirement, if any, will be added to the measured value for flaw evaluation with applicable acceptance criteria specified in Section IWB-3500 of the ASME Code.
- 6 The !\\IRC staff finds that compliance with the ASME Code-required RMSE value is not feasible at this time and that adding the difference between the ASME Code-required RMSE and the demonstrated RMSE to the measured through-wall extent, in addition to the use of the acceptance standards specified in Section IWB 3500 of the ASME Code, provides reasonable assurance of structural integrity, and thus an acceptable level of quality and safety.
4.2 Inside Diameter UT Examinations Supplemented by Eddy Current SNC's examination vendor did not fully meet the qualification requirements of ASME Code,Section XI, Appendix VIII, Supplements 10 and 2. The vendor is qualified for detection of axial flaws for nozzle-to-safe end OM welds and austenitic safe-end welds examined from the 10 surface provided the surface is machined or ground smooth with no exposed root reinforcement or counter-bore. However, where surface roughness may be present, the UT qualifications demonstrated for detection of axial flaws is called into question due to the UT transducer's lift-off from the rough surface/unfavorable 10 geometry. The NRC staff notes that the POI program is not successful in qualifying examiners to detect axial flaws in the presence of rough surfaces.
Therefore, the NRC staff has determined that to fully comply with the subject ASIVIE Code qualification requirement is not possible at this time.
The licensee proposed the use of surface geometry profiling software (profilometry) in conjunction with a focused immersion UT transducer positioned to permit accurate profile data across the examination volume to help the examiner confirm locations where the raw ultrasonic data indicates lack of transducer contact due to problematic surface geometry. The NRC staff finds that the use of profilometry to confirm the presence of rough surfaces acceptable as it provides additional information as to the condition of the surface of the examination volume.
In addition to profilometry, the licensee proposed the use of eddy current examination to supplement the UT examination for the nozzle-to-safe end and safe end-to-pipe welds having sufficient surface roughness to call into question the applicability of the UT examination qualification to detect axial flaws. Profilometry will confirm the presence of rough surfaces and the eddy current examination will assure the detection of surface breaking flaws. SI\\IC states that the eddy current methodology to be used is similar to that used in the V. C. Summer Nuclear Station (VCSNS), Unit 1, outages in 2000, 2002 and 2003. The technique was refined based on examinations performed on a hot-leg OM weld section removed from VCSNS during the 2000 refueling outage. The removed section contained primary water stress corrosion cracking flaws and non-relevant indications resulting from surface geometry and metallurgical interfaces. The NRC staff finds that the licensee's proposed alternative, which combines UT and eddy current techniques in examining for axial flaws in the presence of rough surfaces, will provide an acceptable level of detectability and sensitivity. Therefore, the NRC staff concludes that the licensee's proposed alternative will provide an acceptable level of quality and safety for the subject welds.
5.0 CONCLUSION
Based on the above review, the NRC staff has determined that requiring the licensee to qualify procedures, personnel, and equipment to meet the maximum error of 0.125 inch RMSE for crack depth-sizing is not feasible at the present time. The licensee's proposal of adding the difference between the ASME Code-required RMSE and the demonstrated RMSE to the measured through-wall extent, in addition to the use of the acceptance standards specified in
- 7 Section IWB-3500 of the ASIVIE Code, provides an acceptable level of quality and safety.
Additionally, the licensee's proposal to use surface geometry profiling combined with eddy current examination provides reasonable assurance that the axial flaws in the presence of rough surfaces will be detected, thus providing an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the proposed alternative is authorized for the fourth 10-year lSI interval for FNP, Unit 2, which began on December 1, 2007, and is scheduled to end on November 30,2017. All other ASIVIE 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: Carol Nove, NRRlDCI/CPNB Date of issuance:
March 2, 2010
'memo transmitted SE dated OFFICE NRRlLPL2-1/PM NRRlLPL2-1/LA NRRlCPNB/BC OGC NRRlLPL2-1/BC NAME RMartin SRohrer TChan' Waived GKulesa DATE 3/1/10 3/1/10 12/17/2009 ML090480460 3/2/10