ML031220027
| ML031220027 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 05/06/2003 |
| From: | Richard Laufer NRC/NRR/DLPM/LPD1 |
| To: | Conway J Nine Mile Point |
| Tam P, NRR/DLPM, 415-1451 | |
| References | |
| TAC MB5732 | |
| Download: ML031220027 (8) | |
Text
May 6, 2003 Mr. John T. Conway Vice President Nine Mile Point Nine Mile Point Nuclear Station, LLC P.O. Box 63 Lycoming, NY 13093
SUBJECT:
NINE MILE POINT NUCLEAR STATION, UNIT NO. 2 - AUTHORIZATION OF ALTERNATIVE, INSERVICE INSPECTION (ISI) RELIEF REQUEST ISI-23B (TAC NO. MB5732)
Dear Mr. Mueller:
By letter dated November 20, 2002, Nine Mile Point Nuclear Station, LLC (NMPNS) proposed an alternative to the American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI, Appendix VIII, Supplement 11, Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds. In lieu of the Code requirements, NMPNS proposed using the qualification process as administered by the Electric Power Research Institute (EPRI) - Performance Demonstration Initiative (PDI) for weld overlay qualifications.
The Nuclear Regulatory Commission (NRC) staff reviewed NMPNSs request. On the basis that the NRC staff had previously found the PDI acceptable, the NRC staff determines that the proposed alternative (Relief Request ISI-23B) to use the PDI program for weld overlay qualifications, as described in the November 20, 2002, application, will provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the proposed alternative (Relief Request ISI-23B) is authorized for the third 10-year ISI interval. Details are set forth in the enclosed safety evaluation. If you have any questions, please contact the Project Manager, Mr. Peter S. Tam at 301-415-1451.
Sincerely,
/RA/
Richard J. Laufer, Chief, Section 1 Project Directorate I Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-410
Enclosure:
As stated cc w/encl: See next page
May 6, 2003 Mr. John T. Conway Vice President Nine Mile Point Nine Mile Point Nuclear Station, LLC P.O. Box 63 Lycoming, NY 13093
SUBJECT:
NINE MILE POINT NUCLEAR STATION, UNIT NO. 2 - AUTHORIZATION OF ALTERNATIVE, INSERVICE INSPECTION (ISI) RELIEF REQUEST ISI-23B (TAC NO. MB5732)
Dear Mr. Mueller:
By letter dated November 20, 2002, Nine Mile Point Nuclear Station, LLC (NMPNS) proposed an alternative to the American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI, Appendix VIII, Supplement 11, Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds. In lieu of the Code requirements, NMPNS proposed using the qualification process as administered by the Electric Power Research Institute (EPRI) - Performance Demonstration Initiative (PDI) for weld overlay qualifications.
The Nuclear Regulatory Commission (NRC) staff reviewed NMPNSs request. On the basis that the NRC staff had previously found the PDI acceptable, the NRC staff determines that the proposed alternative (Relief Request ISI-23B) to use the PDI program for weld overlay qualifications, as described in the November 20, 2002, application, will provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the proposed alternative (Relief Request ISI-23B) is authorized for the third 10-year ISI interval. Details are set forth in the enclosed safety evaluation. If you have any questions, please contact the Project Manager, Mr. Peter S. Tam at 301-415-1451.
Sincerely,
/RA/
Richard J. Laufer, Chief, Section 1 Project Directorate I Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-410
Enclosure:
As stated cc w/encl.: See next page DISTRIBUTION:
PUBLIC S. Little ACRS G. Hill (2)
PDI-1 Reading File P. Tam B. Platchek, RGI OGC R. Hernandez Accession Number: ML031220027 OFFICE PDI-1/PM PDI-1/LA EMCB/SC OGC PDI-1/SC NAME PTam SLittle TChan* RHoefling RLaufer DATE 4/24/03 4/23/03 4/7/03 5/1/03 5/6/03 OFFICIAL RECORD COPY
- Safety evaluation transmitted by memo of 4/7/03.
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION NINE MILE POINT NUCLEAR STATION, LLC DOCKET NO. 50-410 NINE MILE POINT NUCLEAR STATION, UNIT NO. 2 RELIEF REQUEST ISI-23B
1.0 INTRODUCTION
By letter dated November 20, 2002, Nine Mile Point Nuclear Station, LLC (the licensee) proposed an alternative to the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, Appendix VIII, Supplement 11, Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds. In lieu of the Code requirements, the licensee proposed using the qualification process as administered by the Electric Power Research Institute (EPRI) - Performance Demonstration Initiative (PDI) for weld overlay qualifications.
2.0 REGULATORY REQUIREMENTS Inservice inspection (ISI) of the ASME Code Class 1, 2, and 3 components is performed in accordance with Section XI of the ASME Code and applicable addenda as required by Title 10 of the Code of Federal Regulations (10 CFR), Subsection 50.55 a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i).
Meanwhile, 10 CFR 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when authorized by the Nuclear Regulatory Commission (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.
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 Inservice Inspection (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) twelve months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable Code of record for the Enclosure 1
second 10-year ISI for Nine Mile Point Nuclear Station, Unit No. 2 (NMP2), is the 1989 Edition of the ASME Code,Section XI.
Pursuant to 10 CFR 50.55a(a)(3)(i), the licensee requested relief to use the EPRI PDI Program for implementation of ASME Code,Section XI, Appendix VIII, Supplement 11 requirements, "Qualification Requirements For Full Structural Overlaid Wrought Austenitic Piping Welds."
3.0 TECHNICAL EVALUATION
The U.S. nuclear licensees created the PDI to implement performance demonstration requirements contained in Appendix VIII of Section XI of the Code. To this end, PDI has developed a program for qualifying equipment, procedures, equipment, and personnel in accordance with the ultrasonic testing criteria of Appendix VIII, Supplement 11. Prior to the Supplement 11 program, EPRI was maintaining a performance demonstration program for weld overlay qualification under the Tri-party Agreement.1 Instead of having two programs with similar objectives, the NRC staff recognized the PDI program for weld overlay qualifications as an acceptable alternative to the Tri-party Agreement.2 The PDI program does not fully comport with the existing requirements of Supplement 11. The differences are discussed below.
(1) Paragraph 1.1(b) of Supplement 11 states limitations to the maximum thickness for which a procedure may be qualified. The Code states that [t]he specimen set must include at least one specimen with overlay thickness within -0.1-in. to +0.25-in. of the maximum nominal overlay thickness for which the procedure is applicable. The Code requirement addresses the specimen thickness tolerance for a single specimen set, but is confusing when multiple specimen sets are used. The PDI proposed alternative states that the specimen set shall include specimens with overlays not thicker than 0.1-in. more than the minimum thickness, nor thinner than 0.25-in. of the maximum nominal overlay thickness for which the examination procedure is applicable. The proposed alternative provides clarification on the application of the tolerance. The tolerance is unchanged for a single specimen set, however, it clarifies the tolerance for multiple specimen sets by providing tolerances for both the minimum and maximum thicknesses. The proposed wording eliminates confusion while maintaining the intent of the overlay thickness tolerance. Therefore, the NRC staff had found this PDI Program revision acceptable.
(2) Paragraph 1.1(d)(1) requires that all base metal flaws be cracks. PDI determined that certain Supplement 11 requirements pertaining to location and size of cracks would be extremely difficult to achieve. For example, flaw implantation requires excavating a volume of base material to allow a pre-cracked coupon to be welded into this area. This 1
The Tri-party Agreement is between NRC, EPRI, and the Boiling Water Reactor Owners Group (BWROG), Coordination Plan for NRC/EPRI/BWROG Training and Qualification Activities of NDE (Nondestructive Examination) Personnel, July 3, 1984.
2 Letter from William H. Bateman to Michael Bratton, Weld Overlay Performance Demonstration Administered by PDI as an Alternative for Generic Letter 88-01 Recommendations, January 15, 2002 (see ADAMS Accession No. ML020160532).
process would add weld material to an area of the specimens that typically consists of only base material, and could potentially make ultrasonic examination more difficult and not representative of actual field conditions. In an effort to satisfy the requirements, PDI developed a process for fabricating flaws that exhibit crack-like reflective characteristics.
Instead of all flaws being cracks as required by Paragraph 1.1(d)(1), the PDI weld overlay performance demonstrations contain at least 70% cracks with the remainder being fabricated flaws exhibiting crack-like reflective characteristics. The fabricated flaws are semi-elliptical with tip widths of less than 0.002 inch. The licensee provided further information describing a revision to the PDI Program alternative to clarify when real cracks, as opposed to fabricated flaws, will be used: Flaws shall be limited to the cases where implantation of cracks produces spurious reflectors that are uncharacteristic of actual flaws. The NRC has reviewed the flaw fabrication process, compared the reflective characteristics between actual cracks and PDI-fabricated flaws, and found the fabricated flaws acceptable for this application.3,4 (3) Paragraph 1.1(e)(1) requires that at least 20% but not less than 40% of the flaws shall be oriented within +/-20 degrees of the axial direction of the piping test specimen. Flaws contained in the original base metal heat-affected zone satisfy this requirement, however, PDI excludes axial fabrication flaws in the weld overlay material. PDI has concluded that axial flaws in the overlay material are improbable because the overlay filler material is applied in the circumferential direction (parallel to the girth weld),
therefore fabrication anomalies would also be expected to have major dimensions in the circumferential direction. The NRC staff found this approach to implantation of fabrication flaws to be reasonable and, therefore, found PDIs application of flaws oriented in the axial direction acceptable.
(4) Paragraph 1.1(e)(1) also requires that the rules of IWA-3300 shall be used to determine whether closely spaced flaws should be treated as single or multiple flaws. PDI treats each flaw as an individual flaw and not as part of a system of closely spaced flaws. PDI controls the flaws going into a test specimen set such that the flaws are free of interfering reflections from adjacent flaws. In some cases, this permits flaws to be spaced closer than what is allowed for classification as a multiple set of flaws by IWA-3300, thus potentially making the performance demonstration more challenging.
Hence, PDIs application for closely spaced flaws was found acceptable.
(5) Paragraph 1.1(e)(2)(a)(1) requires that a base grading unit shall include at least 3 inches of the length of the overlaid weld, and the base grading unit includes the outer 25% of the overlaid weld and base metal on both sides. The PDI program reduced the criteria to 1 inch of the length of the overlaid weld and eliminated from the grading unit the need to include both sides of the weld. The proposed change permits the PDI program to continue using test specimens from the existing weld overlay program which have flaws on both sides of the welds. These test specimens have been used 3
NRC memorandum, "Summary of Public Meeting Held January 31 - February 2, 2001," with PDI Representatives, March 22, 2001(see ADAMS Accession No. 010940402).
4 NRC memorandum, "Summary of Public Meeting Held June 12 through June 14, 2001," with PD1 Representatives, November 29, 2001 (see ADAMS Accession No. ML013330156).
successfully for testing the proficiency of personnel for over 16-years. The weld overlay qualification is designed to be a near-side [relative to the weld] examination, and it is improbable that a candidate would detect a flaw on the opposite side of the weld due to sound attenuation and re-direction caused by the weld microstructure. However, the presence of flaws on both sides of the original weld (outside the PDI grading unit) may actually provide a more challenging examination, as candidates must determine the relevancy of these flaws, if detected. Therefore, PDIs use of the 1-inch length of the overlaid weld base grading unit and elimination from the grading unit the need to include both sides of the weld, as described in the revised PDI Program alternative, was found acceptable.
(6) Paragraph 1.1(e)(2)(a)(3) requires that for unflawed base grading units, at least 1 inch of unflawed overlaid weld and base metal shall exist on either side of the base grading unit. This is to minimize the number of false identifications of extraneous reflectors.
The PDI program stipulates that unflawed overlaid weld and base metal exists on all sides of the grading unit and that flawed grading units must be free of interfering reflections from adjacent flaws which addresses the same concerns as Code. Hence, PDIs application of the variable flaw-free area adjacent to the grading unit was found acceptable.
(7) Paragraph 1.1(e)(2)(b)(1) requires that an overlay grading unit shall include the overlay material and a base metal-to-overlay interface of at least 6 square inches. The overlay grading unit shall be rectangular, with minimum dimensions of 2 inches. The PDI program reduces the base metal-to-overlay interface to at least 1 inch (in lieu of a minimum of 2 inches) and eliminates the minimum rectangular dimension. This criterion is necessary to allow use of existing examination specimens that were fabricated in order to meet the guidance of NRC Generic Letter 88-01 (Tri-party Agreement, see Footnote 1 on Page 2). This criterion may be more challenging than Code requirements because of the variability associated with the shape of the grading unit. Hence, PDIs application of the grading unit was found acceptable.
(8) Paragraph 2.3 states that, for depth sizing tests, 80% of the flaws shall be sized at a specific location on the surface of the specimen identified to the candidate. This requires detection and sizing tests to be separate. PDI revised the weld overlay program to allow sizing to be conducted either in conjunction with, or separately from, the flaw detection test. If performed in conjunction with detection, and the detected flaws do not meet the Supplement 11 range criteria, additional specimens will be presented to the candidate with the regions containing flaws identified. Each candidate will be required to determine the maximum depth of flaw in each region. For separate sizing tests, the regions of interest will also be identified and the maximum depth and length of each flaw in the region will similarly be determined. In addition, PDI stated that grading units are not applicable to sizing tests, and that each sizing region will be large enough to contain the target flaw, but small enough that candidates will not attempt to size a different flaw. The above clarification provides a basis for implementing sizing tests in a systematic, consistent manner that meets the intent of Supplement 11. As such, this method was found acceptable by the NRC staff.
(9) Paragraphs 3.1 and 3.2 of Supplement 11 state that procedures, equipment and personnel as a complete ultrasonic system are qualified for detection or sizing of flaws,
as applicable, when certain criteria are met. The PDI program allows procedure qualification to be performed separately from personnel and equipment qualification.
Historical data indicate that, if ultrasonic detection or sizing procedures are thoroughly tested, personnel and equipment using those procedures have a higher probability of successfully passing a qualification test. In an effort to increase this passing rate, PDI has elected to perform procedure qualifications separately in order to assess and modify essential variables that may affect overall system capabilities. For a procedure to be qualified, the PDI program requires three times as many flaws to be detected (or sized) as shown in Supplement 11 for the entire ultrasonic system. The personnel and equipment are still required to meet Supplement 11. Therefore, the PDI program exceeds ASME Code requirements for personnel, procedures, and equipment qualification.
(10) Paragraph 3.2(b) requires that all extensions of base metal cracking into the overlay material by at least 0.10 inch are reported as being intrusions into the overlay material.
The PDI program omits this criterion because of the difficulty in actually fabricating a flaw with a 0.10 inch minimum extension into the overlay, while still knowing the true state of the flaw dimensions. However, the PDI program requires that cracks be depth-sized to the tolerance of 0.125-inch as specified in the Code. Since the Code tolerance is close to the 0.10-inch value of Paragraph 3.2(b), any crack extending beyond 0.10 inch into the overlay material would be identified as such from the characterized dimensions. The reporting of an extension in the overlay material is redundant for performance demonstration testing because of the flaw sizing tolerance. Therefore, PDIs omission of highlighting a crack extending beyond 0.10-inch into the overlay material was found acceptable.
4.0 CONCLUSION
The NRC staff reviewed the licensees request to use the PDI program as an alternative to the ASME B&PV Code, 1995 Edition with 1996 Addenda, Appendix VIII, Supplement 11, requirements. On the basis that the NRC staff had previously found the PDI acceptable, the NRC staff determines that the licensees proposed alternative (Relief Request ISI-23B) to use the PDI program for weld overlay qualifications, as described in the November 20, 2002, application, will provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the proposed alternative is authorized for the third 10-year ISI interval.
All other requirements of the ASME Code,Section XI, for which relief has not been specifically requested and approved, remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: R. Hernandez Date: May 6, 2003
Nine Mile Point Nuclear Station Unit No. 2 cc:
Regional Administrator, Region I Mr. Michael J. Wallace U. S. Nuclear Regulatory Commission President 475 Allendale Road Nine Mile Point Nuclear Station, LLC King of Prussia, PA 19406 c/o Constellation Energy Group 750 East Pratt Street Resident Inspector Baltimore, MD 21201-2437 Nine Mile Point Nuclear Station P.O. Box 126 James M. Petro, Jr., Esquire Lycoming, NY 13093 Counsel Constellation Power Source, Inc.
111 Market Place Mr. John V. Vinquist, MATS Inc. Suite 500 P.O. Box 63 Baltimore, MD 21202 Lycoming, NY 13093 Mr. William M. Flynn, President Supervisor New York State Energy, Research, Town of Scriba and Development Authority Route 8, Box 382 17 Columbia Circle Oswego, NY 13126 Albany, NY 12203-6399 Mr. Paul D. Eddy Electric Division NYS Department of Public Service Agency Building 3 Empire State Plaza Albany, NY 12223 Charles Donaldson, Esquire Assistant Attorney General New York Department of Law 120 Broadway New York, NY 10271 C. Adrienne Rhodes Chairman and Executive Director State Consumer Protection Board 5 Empire State Plaza, Suite 2101 Albany, NY 12223-1556 Mark J. Wetterhahn, Esquire Winston & Strawn 1400 L Street, NW.
Washington, DC 20005-3502