ML050310406
| ML050310406 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 01/31/2005 |
| From: | Richard Laufer NRC/NRR/DLPM/LPD1 |
| To: | Shriver B PPL Generation |
| Guzman R, NRR/DLPM 415-1030 | |
| References | |
| TAC MC4027, TAC MC4028 | |
| Download: ML050310406 (11) | |
Text
January 31, 2005 Mr. Bryce L. Shriver President, PPL Generation, LLC, and Chief Nuclear Officer PPL Generation, LLC 2 North Ninth Street Allentown, PA 18101
SUBJECT:
SUSQUEHANNA STEAM ELECTRIC STATION, UNITS 1 AND 2 (SSES 1 and 2) - RELIEF FOR QUALIFICATION REQUIREMENTS FOR DISSIMILAR METAL PIPING WELDS (TAC NOS. MC4027 AND MC4028)
Dear Mr. Shriver:
In a letter dated July 26, 2004, PPL Susquehanna, LLC (PPL, the licensee), submitted Relief Request No. 12 proposing alternatives to the requirements of Title 10 of the Code of Federal Regulations (10 CFR), Section 50.55a, concerning the requirements of the American Society of Mechanical Engineers, Boiler and Pressure Vessel Code (ASME Code), for inservice inspection (ISI) programs at SSES 1 and 2. PPL is currently in its third 10-year ISI interval which began on June 1, 2004, and will end on May 31, 2014. The ISI Code of record for the third 10-year interval for SSES 1 and 2 is the 1998 edition through 2000 addenda of ASME Code,Section XI.
Supplement 11 to Appendix VIII, Performance Demonstration for Ultrasonic Examination Systems, of Section XI of the ASME Code contains the qualification requirements for procedures, equipment, and personnel involved with examining dissimilar metal welds using ultrasonic techniques. In lieu of these ASME Code requirements, PPL requested to use dissimilar metal weld criteria of the Electric Power Research Institutes Performance Demonstration Initiative Program.
Based on the information provided by PPL, the Nuclear Regulatory Commission (NRC) staff concludes that the proposed alternative will provide an acceptable level of quality and safety.
Therefore, the use of the proposed alternative is authorized pursuant to 10 CFR 50.55a(a)(3)(i) for the remainder of the current 10-year ISI interval at each unit. The NRC staffs safety evaluation is enclosed.
B. Shriver If you have any questions, please contact your project manager, Mr. Rich Guzman, at (301)415-1030.
Sincerely,
/RA/
Richard J. Laufer, Chief, Section 1 Project Directorate I Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket Nos. 50-387 and 50-388
Enclosure:
Safety Evaluation cc w/encl: See next page
B. Shriver If you have any questions, please contact your project manager, Mr. Rich Guzman, at (301)415-1030.
Sincerely,
/RA/
Richard J. Laufer, Chief, Section 1 Project Directorate I Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket Nos. 50-387 and 50-388
Enclosure:
Safety Evaluation cc w/encl: See next page DISTRIBUTION:
PUBLIC PDI-1 RF RLaufer TChan ACRS RGuzman MOBrien GHill (4)
OGC GMatakas, Rgn-1 PPatnaik CMiller, EDO, RGN-I DLPM DPR ACCESSION NO.: ML050310406
- SE provided. No major changes made.
OFFICE PDI-1/PM PDI-2/LA EMEB/SC*
OGC PDI-1/SC NAME RGuzman MO'Brien TChan MYoung RLaufer DATE 1/14/05 1/14/05 10/12/04 SE DTD 1/27/05 1/31/05 OFFICIAL RECORD COPY
Susquehanna Steam Electric Station, Unit Nos. 1 and 2 cc:
Britt T. McKinney Vice President - Nuclear Site Operations PPL Susquehanna, LLC 769 Salem Blvd., NUCSB3 Berwick, PA 18603-0467 Robert A. Saccone Vice President - Nuclear Operations PPL Susquehanna, LLC 769 Salem Blvd., NUCSB3 Berwick, PA 18603-0467 Aloysius J. Wrape, III General Manager - Nuclear Assurance PPL Susquehanna, LLC Two North Ninth Street, GENPL4 Allentown, PA 18101-1179 Terry L. Harpster General Manager - Performance Improvement and Oversight PPL Susquehanna, LLC 769 Salem Blvd., NUCSA4 Berwick, PA 18603-0467 Gregory F. Ruppert General Manager - Nuclear Engineering PPL Susquehanna, LLC 769 Salem Blvd., NUCSB3 Berwick, PA 18603-0467 Rocco R. Sgarro Manager - Nuclear Regulatory Affairs PPL Susquehanna, LLC Two North Ninth Street, GENPL4 Allentown, PA 18101-1179 Walter E. Morrissey Supervising Engineer Nuclear Regulatory Affairs PPL Susquehanna, LLC 769 Salem Blvd., NUCSA4 Berwick, PA 18603-0467 Michael H. Crowthers Supervising Engineer Nuclear Regulatory Affairs PPL Susquehanna, LLC Two North Ninth Street, GENPL4 Allentown, PA 18101-1179 Dale F. Roth Manager - Quality Assurance PPL Susquehanna, LLC 769 Salem Blvd., NUCSB2 Berwick, PA 18603-0467 Luis A. Ramos Community Relations Manager, Susquehanna PPL Susquehanna, LLC 634 Salem Blvd., SSO Berwick, PA 18603-0467 Bryan A. Snapp, Esq Assoc. General Counsel PPL Services Corporation Two North Ninth Street, GENTW3 Allentown, PA 18101-1179 Supervisor - Document Control Services PPL Susquehanna, LLC Two North Ninth Street, GENPL4 Allentown, PA 18101-1179 Richard W. Osborne Allegheny Electric Cooperative, Inc.
212 Locust Street P.O. Box 1266 Harrisburg, PA 17108-1266 Director - Bureau of Radiation Protection Pennsylvania Department of Environmental Protection P.O. Box 8469 Harrisburg, PA 17105-8469 Senior Resident Inspector U.S. Nuclear Regulatory Commission P.O. Box 35, NUCSA4 Berwick, PA 18603-0035
Susquehanna Steam Electric Station, Unit Nos. 1 and 2 cc:
Regional Administrator, Region 1 U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Board of Supervisors Salem Township P.O. Box 405 Berwick, PA 18603-0035 Dr. Judith Johnsrud National Energy Committee Sierra Club 443 Orlando Avenue State College, PA 16803
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO RELIEF REQUEST NO. 12 TO USE ALTERNATIVE PROGRAM AS AN ALTERNATIVE FOR IMPLEMENTATION OF SUPPLEMENT 11 TO APPENDIX VIII OF THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS BOILER AND PRESSURE VESSEL CODE, SECTION XI, REQUIREMENTS PPL SUSQUEHANNA, LLC ALLEGHENY ELECTRIC COOPERATIVE, INC.
SUSQUEHANNA STEAM ELECTRIC STATION, UNITS 1 AND 2 DOCKET NOS. 50-387 AND 50-388
1.0 INTRODUCTION
By letter dated July 26, 2004 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML042180182), PPL Susquehanna, LLC (PPL, the licensee),
submitted Relief Request No. 12 (3RR-12) proposing alternatives to the requirements of Title 10 of the Code of Federal Regulations (10 CFR), Section 50.55a, concerning the requirements of the American Society of Mechanical Engineers, Boiler and Pressure Vessel Code (ASME Code), for inservice inspection (ISI) programs at Susquehanna Steam Electric Station, Units 1 and 2 (SSES 1 and 2).
Supplement 11 to Appendix VIII, Performance Demonstration for Ultrasonic Examination Systems, of Section XI of the ASME Code contains the qualification requirements for procedures, equipment, and personnel involved with examining dissimilar metal welds using ultrasonic techniques. In lieu of these ASME Code requirements, PPL requested to use the dissimilar metal weld criteria of the Electric Power Research Institutes (EPRIs) Performance Demonstration Initiative (PDI) Program. PPLs request applies to the third 10-year ISI interval for both SSES 1 and 2.
2.0 REGULATORY EVALUATION
Section 50.55a(g) requires that ISI of ASME Code, Class 1, 2, and 3 components be performed in accordance with Section XI of the ASME Code and applicable addenda, except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i).
According to 10 CFR 50.55a(a)(3), alternatives to the requirements of paragraph (g) may be used, when authorized by the Nuclear Regulatory Commission (NRC), if an applicant demonstrates that the proposed alternatives would provide an acceptable level of quality and safety or if the specified requirement 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 preservice 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 ISI 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 ISI Code of record for the third 10-year interval for SSES 1 and 2 is the 1998 edition through 2000 addenda of ASME Code,Section XI.
3.0 TECHNICAL EVALUATION
3.1 Components for Which Relief is Requested PPL has requested relief for pressure retaining welds that are subject to examination using procedures, personnel, and equipment qualified to the 1995 edition, 1996 addenda of ASME Code,Section XI, Appendix VIII, Supplement 11, Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds.
3.2 Code Requirements for which Relief is Requested Pursuant to 10 CFR 50.55a(a)(3)(i), the licensee is requesting relief from the weld overlay requirements in the following paragraphs of ASME Code,Section XI, Appendix VIII, Supplement 11.
Paragraph 1.1(d)(1) requires that all base metal flaws be cracks.
Paragraph 1.1(e)(1) requires that at least 20 percent but not less than 40 percent of the flaws shall be oriented within +/-20 degrees of the axial direction.
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.
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 outer 25 percent of the overlaid weld and base metal on both sides.
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.
Paragraph 1.1(e)(2)(b)(1) requires that an overlay grading unit shall include the overlay material and the base metal-to-overlay interface of at least 6 square inches. The overlay grading unit shall be rectangular, with minimum dimensions of 2 inches.
Paragraph 3.2(b) requires that all extensions of base metal cracking into the overlay material by at least 0.1 inch are reported as being intrusions into the overlay material.
3.3 Licensees Proposed Alternative to ASME Code The proposed alternative is to use the EPRI-PDI Program in lieu of the requirements of ASME Code,Section XI, Appendix VIII, Supplement 11.
3.4 Licensees Bases for Request (as stated by PPL)
Paragraph 1.1(d)(1), requires that all base metal flaws be cracks. As illustrated
[in PPLs July 26, 2004 submittal], implanting a crack requires excavation of the base material on at least one side of the flaw. While this may be satisfactory for ferritic materials, it does not produce a usable axial flaw in austenitic materials because the sound beam, which normally passes only through base material, must now travel through weld material on at least one side, producing an unrealistic flaw response. To resolve this issue, the PDI program revised this paragraph to allow use of alternative flaw mechanisms under controlled conditions. For example, alternative flaws shall be limited to when implantation of cracks precludes obtaining an effective ultrasonic response, flaws shall be semielliptical with a tip width of less than or equal to 0.002 inches, and at least 70 percent of the flaws in the detection and sizing test shall be cracks and the remainder shall be alternative flaws.
Relief is requested to allow closer spacing of flaws provided they didnt interfere with detection or discrimination. The existing specimens used to date for qualifications to the Tri-party (NRC/BWROG[Boiling Water Reactor Owners Group]/EPRI) agreement have a flaw population density greater than allowed by the current Code requirements. These samples have been used successfully for all previous qualifications under the Tri-party agreement program. To facilitate their use and provide continuity from the Tri-party agreement program to Supplement 11, the PDI Program has merged the Tri-party test specimens into their weld overlay program. For example: the requirement for using IWA-3300 for proximity flaw evaluation in paragraph 1.1(e)(1) was excluded, instead indications will be sized based on their individual merits; paragraph 1.1(d)(1) includes the statement that intentional overlay fabrication flaws shall not interfere with ultrasonic detection or characterization of the base metal flaws; paragraph 1.1(e)(2)(a)(1) was modified to require that a base metal grading unit include at least 1 inch of the length of the overlaid weld, rather than 3 inches; paragraph 1.1(e)(2)(a)(3) was modified to require sufficient unflawed overlaid weld and base metal to exist on all sides of the grading unit to preclude interfering reflections from adjacent flaws, rather than the 1 inch requirement of Supplement 11; paragraph 1.1(e)(2)(b)(1) was modified to define an overlay fabrication grading unit as including the overlay material and the base metal-to-overlay interface for a length of at least 1 inch rather than the 6 square inch requirement of Supplement 11; and paragraph 1.1(e)(2)(b)(2) states that overlay fabrication grading units designed to be unflawed shall be separated by unflawed overlay material and unflawed base metal-to-overlay interface for at least 1 inch at both ends, rather than around its entire perimeter.
1 The existing weld overlay program is the industrys response to Generic Letter 88-01 which resulted in a Tri-party Agreement between NRC, EPRI, and the Boiling Water Reactor Owners Group (BWROG), Coordination Plan for NRC/EPRI/BWROG Training and Qualification Activities of NDE Personnel, July 3, 1984.
Additionally, the requirement for axially oriented overlay fabrication flaws in paragraph 1.1(e)(1) was excluded from the PDI Program as an improbable scenario. Weld overlays are typically applied using automated gas tungsten arc welding techniques with the filler metal being applied in a circumferential direction. Because resultant fabrication induced discontinuities would also be expected to have major dimensions oriented in the circumferential direction axial overlay fabrication flaws are unrealistic.
The PDI Program revised paragraph 2.0 to permit the overlay fabrication flaw test and the base metal flaw tests be performed separately. The requirement in paragraph 3.2(b) for reporting all extensions of cracking into the overlay is omitted from the PDI Program because it is redundant to the RMS [root mean square] calculations performed in paragraph 3.2(c) and its presence adds confusion and ambiguity to depth sizing as required by paragraph 3.2(c). This also makes the weld overlay program consistent with the Supplement 2 depth sizing criteria.
The PDI Program omits the phrase and base metal on both sides, in paragraph 1.1(e)(2)(a)(1) because some of the qualification samples included flaws on both sides of the weld. To avoid confusion, several instances of the term cracks or cracking were changed to the term flaws because of the use of alternative flaw mechanisms. Additionally, to avoid confusion, the overlay thickness tolerance contained in the last sentence of paragraph 1.1(b), was reworded and the phrase and the remainder shall be alternative flaws was added to the next to last sentence in paragraph 1.1(d)(1).
3.5
NRC Staff Evaluation
The nuclear power industry tasked PDI with the implementation of an ASME Code,Section XI, Appendix VIII, Supplement 11, performance demonstration program. The PDI program is routinely assessed by the NRC staff for consistency with the ASME Code and proposed ASME Code changes. In order to meet the scheduled implementation date of November 22, 2001, specified in 10 CFR 50.55a(g)(6)(ii)(C), PDI evaluated the applicability of using test specimens from an existing weld overlay program1 for its Supplement 11 performance demonstration program. Their evaluation identified differences with Paragraphs 1.1(e)(1), 1.1(e)(2)(a)(1),
1.1(e)(2)(a)(3), 1.1(e)(2)(b)(1), and 3.2(b). PDI proposed through the ASME Code that these paragraphs be changed to permit using the existing weld overlay test specimens.
Paragraph 1.1(e)(1) requires that at least 20 percent but not less than 40 percent of the flaws shall be oriented within +/- 20 degrees of the axial direction. In the PDI program, the flaws satisfy the requirement and specifies that the flaws must be in the base metal. This is a tightening of the requirements. Hence, PDIs application of flaw angles to the axial direction provide reasonable assurance of structural integrity.
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 would permit flaws to be closer together than what is allowed by IWA-3300, thus making the performance demonstration more challenging. Hence, PDIs application for closely spaced flaws provide reasonable assurance of structural integrity.
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 percent 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 test specimens from the existing weld overlay program have flaws on both sides of the welds which prevents them from satisfying the base grading unit requirements. These test specimens have been used successfully for testing the proficiency of personnel for over 16 years. This is a more challenging test because the individual must locate the flaw on the correct side of the weld. Hence, PDIs application of the 1-inch length of the overlaid weld base grading unit and elimination from the grading unit of the need to include both sides of the weld provide reasonable assurance of structural integrity.
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 exist on all sides of the grading unit and be free of interfering reflections from adjacent flaws, which addresses the same concerns as the Code. Hence PDIs application of the variable flaw free area adjacent to the grading unit provide reasonable assurance of structural integrity.
Paragraph 1.1(e)(2)(b)(1) requires that an overlay grading unit shall include the overlay material and the 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 more challenging than the Code because of the variability associated with the shape of the grading unit. Hence, PDIs application of the grading unit provide reasonable assurance of structural integrity.
Paragraph 3.2(b) requires that all extensions of base metal cracking into the overlay material by at least 0.1 inch be reported as intrusions into the overlay material. The PDI program omits this criteria. The PDI program requires that cracks be sized to the tolerance specified in the Code, which is 0.125 inches. Since the Code tolerance is close to the 0.1 inch value of Paragraph 3.2(b), any crack extending beyond 0.1 inch into the overlay material would be identified from its dimensions. The reporting of an extension in the overlay material is redundant for performance demonstration testing. Hence, PDIs omission of highlighting a crack extending beyond 0.1 inch into the overlay material provide reasonable assurance of structural integrity.
In addition to the changes for flaw locations, PDI determined that certain Supplement 11 requirements pertaining to location and size of cracks would be difficult to achieve. In an effort to satisfy the requirements, PDI developed a process for fabricating flaws that exhibited crack-like reflective characteristics. Instead of all flaws being cracks, as required by
2 NRC memorandum, Summary of Public Meeting Held January 31 - February 2, 2001, with PDI Representatives, March 22, 2001 (ADAMS Accession No. ML010940402).
3 NRC memorandum, Summary of Public Meeting Held June 12 through June 14, 2001, with PDI Representatives, November 29, 2001 (ADAMS Accession No. ML013330156).
paragraph 1.1(d)(1), the PDI weld overlay performance demonstrations contain at least 70 percent cracks with the remainder being fabricated flaws exhibiting crack-like reflective characteristics. The NRC has reviewed the flaw fabrication process, and has compared the reflective characteristics between cracks and fabricated flaws. NRC finds that the flaw fabrication process provides reasonable assurance of structural integrity.2, 3
4.0 CONCLUSION
The NRC staff concludes that the licensees proposed alternative to Supplement 11, as administered by the EPRI-PDI Program, provides an acceptable level of quality and safety.
Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the NRC staff authorizes the proposed alternative described in PPLs letter dated July 26, 2004, for SSES 1 and 2 for the third 10-year ISI interval.
All other ASME Code,Section XI, requirements for which relief has not been specifically requested remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: P. Patnaik