ML093340617
| ML093340617 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 12/11/2009 |
| From: | Boyce T Plant Licensing Branch II |
| To: | Swafford P Tennessee Valley Authority |
| Brown E, NRR/DORL, 415-2315 | |
| References | |
| RR 2-ISI-21, TAC ME1319 | |
| Download: ML093340617 (13) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 December 11, 2009 Mr. Preston D. Swafford Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801
SUBJECT:
BROWNS FERRY NUCLEAR PLANT, UNIT 2 - CORRECTION TO LETTER AND SAFETY EVALUATION REGARDING THE THIRD TEN-YEAR INTERVAL INSERVICE INSPECTION PROGRAM RELATED TO THE EXAMINATION OF PIPING WELD OVERLAYS (TAC NO. ME1319)
Dear Mr. Swafford:
By letter dated May 22,2009, the Tennessee Valley Authority (TVA) requested relief (RR 2-ISI-21) from the requirements specified in the American Society of Mechanical Engineers Code,Section XI for inspecting piping weld overlays using ultrasonic testing under Title 10, Code of Federal Regulations, Section 50.55a(a)(3)(i) for the Browns Ferry Nuclear Plant, Unit 2. TVA informed the Nuclear Regulatory Commission (NRC) by letter dated October 5, 2009, that NRC's August 12, 2009, response to that request contained errors.
Enclosed is the corrected version of that response, in its entirety. Lines in the right margin indicate areas of the corrections. These corrections do not affect the NRC staffs conclusions associated with the safety evaluation for RR 2-ISI-21. We regret any inconvenience this may have caused.
If you have any questions regarding this matter, please call Ms. Eva Brown at (301) 415-2315.
Sincerely,
~
Thomas H. Boyce, ph,ief Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-260
Enclosure:
Corrected Letter cc w/enclosure: Distribution Iistserv
ENCLOSURE BROWNS FERRY NUCLEAR PLANT, UNIT 2 CORRECTION TO LETTER AND SAFETY EVALUATION REGARDING THE THIRD TEN-YEAR INTERVAL INSERVICE INSPECTION PROGRAM RELATED TO THE EXAMINATION OF PIPING WELD OVERLAYS
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 August 12,2009 Mr. Preston D. Swafford Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801
SUBJECT:
BROWNS FERRY NUCLEAR PLANT, UNIT 2, THE THIRD TEN-YEAR INTERVAL INSERVICE INSPECTION PROGRAM RELATED TO THE EXAMINATION OF PIPING WELD OVERLAYS (TAC NO. ME1319)
Dear Mr. Swafford:
Bya letter dated May 22,2009, the Tennessee Valley Authority (TVA, the licensee) submitted Relief Request (RR) 2-ISI-21 requesting relief from the requirements specified in the American Society of Mechanical Engineers Code (AS ME),Section XI for inspecting piping weld overlays using ultrasonic testing under Title 10, Code of Federal Regulations (10 CFR), Section 50.55a(a)(3)(i) for the Browns Ferry Nuclear Plant, Unit 2. The request proposed that in lieu of the requirements of the ASME Code,Section XI, Appendix VIII, Supplement 11 requirements, the procedures, personnel, and equipment qualified to meet the requirements of ASME Section XI, Appendix VIII, Supplement 11 as stated in the 1995 Edition via 1996 addenda, as administered by the Electric Power Research Institute's Performance Demonstration Initiative processes be used to conduct the required examinations for piping weld overlays.
The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review of the information provided in TVA's May 22, 2009, letter. The NRC staff concluded that the proposed alternative to the requirements of Section XI, 1995 Edition through 1996 addenda as amended by 10 CFR 50.55a(b)(2)(xxiv), Appendix VIII, Supplement 11 of the ASME Code described in the licensee's letter provides an acceptable level of quality and safety. Therefore, RR-2-ISI-21 is authorized pursuant to 10 CFR 50.55a(a)(3)(i) for Browns Ferry Nuclear Plant, Unit 2. All other requirements of the ASME Code,Section XI for which relief was not specifically requested and approved in this relief request remain applicable, including third party review by the Authorized Nuclear Inservice Inspector.
P. Swafford -2 This relief is authorized for the remainder of the third 1O-year inservice inspection interval at Browns Ferry Unit 2, which began May 23, 2001, and is scheduled to end May 24, 2011.
Sincerely, 4Jf7:~
Thomas H. Boyce, ~ief Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-260
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 INSERVICE INSPECTION PROGRAM TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT, UNIT 2 DOCKET NO. 50-260
1.0 INTRODUCTION
By letter dated May 22,2009, the Tennessee Valley Authority (TVA, the licensee) submitted a relief request from certain qualification requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (ASME Code) at the Browns Ferry Nuclear Plant (BFN), Unit 2. Specifically, the licensee proposed in Relief Request 2-ISI-21 to use the ASME Code,Section XI, Appendix VIII, Supplement 11, "Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds," as administered by the Electric Power Research Institute (EPRI), Performance Demonstration Initiative (PDI) program. The request is for the remainder of the third 1O-year inservice inspection (IS I) interval that began on May 23, 2001, and is scheduled to end May 24, 2011.
The safety evaluation is being issued to document the decision made by the U.S. Nuclear Regulatory Commission (NRC) staff to grant the licensee's request by verbal authorization on May 26, 2009. The NRC staffs memorandum dated June 12, 2009, reflects the basis for verbal approval.
2.0 REGULATORY EVALUATION
The lSI of the 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 Title 10 Code of Federal Regulations (10 CFR) Section 50.55a(g), except where specific relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). It states, in part, in 10 CFR 50.55a(a)(3) that alternatives to the requirements of paragraph (g) may be used when authorized by the NRC, if the applicant 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) will meet the requirements, except the design and access provisions and the 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 inservice Enclosure
-2 examination of components and system pressure tests conducted during the first 1O-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. As stated in 10 CFR 50.55a(g)(4)(iv), inservice examination of components and system pressure tests may meet the requirements set forth in subsequent editions and addenda that are incorporated by reference in paragraph 10 CFR 50.55a(b), subject to the limitations and modification listed in 10 CFR 50.55a(b) and subject to Commission approval. Portions of editions or addenda may be used provided that all related requirements of the respective editions or addenda are met. The code of record for the third 1O-year interval for Unit 2 is the 1995 Edition through 1996 Addenda of the ASME Code.
3.0 TECHNICAL EVALUATION
3.1 Affected Component BFN Unit 2 Weld Overlays in the Risk-Informed lSI Program that require examination:
WELD-NO SYSTEM PIPE SIZE CATEGORY GR-2-15* Recirculation 12.0 E DSRWC-2-03* RWCU 6.0 E DSRWC-2-04* RWCU 6.0 E DSRWC-2-05* RWCU 6.0 E Weld Overlays in the BFN Unit 2 Risk-Informed lSI Program that currently do not require examination:
WELD-NO SYSTEM PIPE SIZE CATEGORY TCS-2-421* Core Spray 12.0 E GR-2-45* Recirculation 12.0 E GR-2-59* Recirculation 28.0 E GR-2-61* Recirculation 28.0 E GR-2-64* Recirculation 28.0 E RFW-2-018-001 Feedwater 2.0 N/A
- Welds previously approved in BFN Relief Request 2-ISI-21, Revision 0, submitted by TVA letter dated June 30,2003, and approved for relief by NRC SER dated December 19,2003.
3.2 Applicable Code The 1995 Edition through 1996 addenda of ASME Section XI, as required by 10 CFR 50.55a(b)(2)(xxiv). The ultrasonic testing (UT) examination must be performed using personnel, procedures, and equipment qualified in accordance with Appendix VIII, Supplement 11. The selected paragraphs in Supplement 11 affected by this request for relief are:
-3 1.1 (b), 1.1 (d)(1), 1.1 (e)(1), 1.1 (e)(2), 1.1 (e)(2)(a)(1), 1.1 (e)(2)(a)(2), 1.1 (e)(2)(a)(3), 1.1 (e)(2)(b)(1),
1.1(e)(2)(b)(2), 1.1(e)(2)(b)(3), 1.1(f)(1), 1.1(f)(3), 1.1(f)(4), 2.0, 2.1, 2.2(d), 2.3, 3.1, 3.2(a), and 3.2(b).
3.3 Proposed Alternative In lieu of the requirements of ASME Section XI, 1995 Edition through 1996 addenda, Appendix VIII, Supplement 11, the POI Program shall be used. The licensee proposes to utilize personnel, procedures, and equipment qualified in accordance with ASME Section XI, Appendix VIII, Supplement 11.
3.4 Licensee Basis for the Alternative and Staff Evaluation The U.S. nuclear utilities created the POI program to implement performance demonstration requirements contained in Appendix VIII of Section XI of the ASME Code. To this end, POI has developed a program for qualifying equipment, procedures, and personnel for examinations of weld overlays in accordance with the UT criteria of Appendix VIII, Supplement 11. Prior to the Supplement 11 program, EPRI maintained a performance demonstration program for weld overlay qualification under the Tri-party Agreement (Reference 1). Instead of having two programs with similar objectives, the NRC staff recognized the POI program for weld overlay qualifications as an acceptable alternative to the Tri-party Agreement (AOAMS Accession No. ML020160532).
The POI program is routinely assessed by the NRC staff for consistency with the current ASME Code and proposed changes. The POI program does not fully comport with the existing requirements of Supplement 11. The differences are in flaw locations within test specimens and fabricated flaw tolerances. The changes in flaw location permitted using test specimens from the Tri-party Agreement, and the changes in fabricated flaw tolerances provide UT acoustic responses similar to the responses associated with intergranular stress corrosion cracking (IGSCC). Based on the discussions at these public meetings, the staff determined that the POI program provides an acceptable level of quality and safety.
Pursuant to 10 CFR 50.55a(a)(3)(i), the licensee requested relief to use the EPRI POI Program for implementation of Appendix VIII, Supplement 11 requirements. Specifically, relief is requested from Supplement 11, Paragraphs 1.1(b), 1.1(d)(1), 1.1(e)(1), 1.1(e)(2), 1.1(e)(2)(a)(1),
1.1(e)(2)(aX2), 1.1(e)(2)(a)(3), 1.1(e)(2)(b)(1), 1.1(e)(2)(b)(2), 1.1(e)(2)(b)(3), 1.1(f)(1), 1.1(f)(3),
1.1(f)(4), 2.2(d), 2.0, 2.1, 2.2(d), 2.3, 3.1, 3.2(a) and 3.2(b). The proposed alternative will be implemented through use of the EPRI-POI Program weld overlay examination qualification requirements.
The licensee's basis for the proposed alternative and the staff evaluation of the differences identified in the POI program with Supplement 11 are as follows:
Paragraph 1.1 (b) of Supplement 11 states limitations to the maximum thickness for which a procedure may be qualified. The ASME Code states that, "The specimen set must include at least one specimen with an overlay thickness within minus 0.1 O-inch to plus 0.25-inch of the maximum
- 4 nominal overlay thickness for which the procedure is applicable." The ASME Code requirement addresses the specimen thickness tolerance for a single specimen set, but is confusing when multiple specimen sets are used. The POI proposed alternative states that, "the specimen set shall include specimens with overlays not thicker than 0.1 O-inch more than the minimum thickness, nor thinner than 0.25-inch 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, the proposed alternative 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 staff finds that this POI program alternative maintains the intent of the Supplement 11 requirements and is acceptable.
Paragraph 1.1(d)(1) requires that all base metal flaws be cracks. POI 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 process would add weld material to an area of the specimen 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, POI 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 POI program for weld overlays contain at least lO-percent 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-inches. The licensee provided further information describing a revision to the POI 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 POI-fabricated flaws, and found that the fabricated flaws for this application provide assurance that the POI program meets the intent of the Supplement 11 requirement. Therefore, the staff finds that the proposed alternative to the Supplement 11 requirement is acceptable.
Paragraph 1.1(e)(1) requires that at least 20-percent but not less than 40-percent of the flaws shall be oriented within plus or minus 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, POI excludes axial fabrication flaws in the weld overlay material. POI 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 finds that this approach to implantation of fabrication flaws is reasonable for meeting the intent of the Supplement 11 requirement. Therefore, the staff concludes that POI's application of flaws oriented in the axial direction is acceptable.
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. POI treats each flaw as an individual flaw and not as part of a system of closely spaced flaws. POI 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
-5 multiple set of flaws by IWA-3300, thus potentially making the performance demonstration more challenging than the existing requirement. Hence, the staff concludes that POI's application for closely spaced flaws is acceptable.
Paragraph 1.1 (e )(2) requires that specimens be divided into base metal and overlay grading units.
The POI program adds clarification with the addition of the word "fabrication" and ensures that flaw identification will not be masked by other flaws with the addition of "Flaws shall not interfere with ultrasonic detection or characterization of other flaws." POI's alternative provides c1ari"fication and assurance that the flaws are identified. Therefore, the staff finds that the POI alternative to the Supplement 11 requirement is acceptable.
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 POI 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 POI program to continue using test specimens from the existing weld overlay program which have Haws on both sides of the welds. These test specimens have been used 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 the sound attenuation and re-direction caused by the weld microstructure. However, the presence of flaws on both sides of the original weld (outside the POI grading unit) may actually provide a more challenging examination, as candidates must determine the relevancy of these flaws, if detected.
The NRC staff has detennined that POI's use of the one 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 POI program alternative, is an acceptable alternative to the Supplement 11 requirements. Therefore, the staff finds the proposed alternative acceptable.
Paragraph 1.1(e)(2)(a)(2) requires, when base metal cracking penetrates into the overlay material, that a portion of the base grading unit shall not be used as part of the overlay grading unit. The staff finds that the POI program adjusts for the changes in Paragraph 1.1(e)(2)(a)(2) and conservatively states that when base metal flaws penetrate into the overlay material, no portion of it shall be used as part of the overlay fabrication grading unit. The staff finds that the POI program also provided clarification by the addition of the term "flaws" for "cracks" and the addition of "fabrication" to "overlay grading unit." The NRC staff concludes that the POI program alternative provides clarification and conservatism and, therefore, is acceptable.
Paragraph 1.1(e)(2Xa)(3) requires that for unflawed base grading units, at least 1 inch of un11awed 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 POI program stipulates that unflawed overlaid weld and base metal exists on all sides of the grading unit and flawed grading units must be free of interfering reflections from adjacent flaws which addresses the same concerns as the ASME Code. Hence, the staff concludes that POI's application of the variable flaw-free area adjacent to the grading unit meets the intent of the Supplement 11 requirements and is, therefore, acceptable.
-6 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 one inch (in lieu of a minimum of two inches) and eliminates the minimum rectangular dimension. This change is necessary to allow use of existing examination specimens that were fabricated in order to meet NRC Generic Letter 88-01 (Tri-party Agreement, July 1984). This change may be more challenging to meet than that of the ASME Code because of the variability associated with the shape of the grading unit. Therefore, the staff concludes that PDl's application of the grading unit is an acceptable alternative to the Supplement 11 requirements and is acceptable.
Paragraph 1.1 (e)(2)(b)(2) requires that unflawed overlay grading units shall be surrounded by unflawed overlay material and unflawed base metal-to-overlay interface for at least one inch around it's entire perimeter. The PDI program redefines the area by noting unflawed overlay fabrication grading units shall be separated by at least 1 inch of unflawed material at both ends and sufficient area on both sides to preclude interfering reflections from adjacent flaws. The staff determined that the relaxation in the required area on the sides of the specimens, while still ensuring no interfering reflections, may provide a more challenging demonstration than required by ASME Code because of the possibility of having a parallel flaw on the opposite side of the weld.
Therefore, the staff concludes that PDl's application is an acceptable alternative to the Supplement 11 requirements.
Paragraph 1.1(e)(2)(b)(3) requirements are retained in the PDI program. In addition, the PDI program requires that initial procedure qualification contain three times the number of flaws required for a personal qualification. To qualify new values of essential variables, the equivalent of at least one personal qualification is required. The NRC staff concludes that PDl's additions enhance the ASME Code requirements and are, therefore, acceptable because it provides for a more stringent qualification criteria.
Paragraph 1.1 (f)( 1) requirements are retained in the PDI program, with the clarification change of the term "flaws" for "cracks." In addition, the PDI program includes the requirements that sizing sets shall contain a distribution of flaw dimensions to verify sizing capabilities. The PDI program also requires that initial procedure qualification contains three times the number of flaws required for a personal qualification. To qualify new values of essential variables, the equivalent of at least one personal qualification is required. The staff concludes that PDl's additions enhance the ASME Code requirements and are, therefore, acceptable because it provides a more stringent qualification criteria.
Paragraphs 1.1(f)(3) and 1.1(f)(4) requirements are clarified by the PDI program by replacing the term "cracking" with "flaws" because of the use of alternative flaw mechanisms. The staff concludes that this clarification in the PDI program meets the intent of the ASME Code requirements and is acceptable.
-7 Paragraph 2.0 is silent on performance demonstrations for the weld metal and overlay fabrication.
The POI program addresses the two performance demonstrations by specifying that they may be performed separately. The POI program adds clarity to the testing criteria without changing the requirement. Therefore, the staff concludes that POI's clarification is an enhancement to ASME Code requirement and is acceptable.
Paragraphs 2.1 and 2.2(d) requirements are clarified by the POI program by the addition of the terms "metal" and "fabrication." These terms were added to clarify the description of the grading units present in a specimen. Metal was added to base to read base metal, and fabrication was added to overlay to read overlay fabrication. The staff determined that the clarifications provide acceptable classification of the terms they are enhancing. Therefore, the NRC staff concludes that the POI program meets the intent of the ASME Code requirements and is acceptable.
Paragraph 2.3 requires that, for depth sizing tests, aD-percent 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 performed separately. The POI 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 the 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, POI 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 such that candidates will not attempt to size a different flaw. The staff has determined that the above clarification provides a basis for implementing sizing tests in a systematic, consistent manner that meets the intent of Supplement 11. Therefore, the staff concludes that POI's method is acceptable.
Paragraph 3.1 requires that examination 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 POI 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, POI 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 POI 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 the Supplement 11 requirement. Therefore, the POI program criteria exceed the ASME Code requirements for personnel, procedures, and equipment qualifications. The NRC staff concludes that the POI program criteria are acceptable.
Paragraph 3.2(a) refers to term the "cracking" in the base metal and flaws within the same acceptance criteria. The POI program changed the term from cracking to flaws for consistence in the acceptance criteria and uniformity within the proposed alternative. The staff concludes that POI's change adds clarity and meets the intent of the ASME Code requirements, thus the change is acceptable.
-8 Paragraph 3.2(b) requires that all extensions of base metal cracking into the overlay material by at least 0.1 O-inch are reported as being intrusions into the overlay material. The POI program omits this criterion because of the difficulty in actually fabricating a flaw with a 0.1 O-inch minimum extension into the overlay, while still knowing the true state of the flaw dimensions. However, the POI program requires that cracks be depth-sized to the tolerance specified in the ASME Code which is 0.125-inch. Since the ASME Code tolerance is close to the 0.10-inch value of Paragraph 3.2(b), any crack extending beyond 0.1 O-inch into the overlay material would be identified as such from the characterized dimensions. The NRC staff has determined that reporting of an extension in the overlay material is redundant for performance demonstration testing because of the flaw sizing tolerance. Therefore, the staff concludes that POI's omission of highlighting a crack extending beyond 0.1 O-inch into the overlay material is acceptable.
The POI Program is routinely assessed by the NRC staff for consistency with the current ASME Code and proposed changes. The POI Program does not fully comport with the existing requirements of Supplement 11. POI presented the differences at public meetings in which the NRC participated (AOAMS Accession no. ML010940402 and ML013330156). The differences are in flaw locations within test specimens and fabricated flaw tolerances. The changes in flaw location permitted using test specimens from the Tri-party Agreement, and the changes in fabricated flaw tolerances provide UT acoustic responses similar to the responses associated with IGSCC. The NRC staff is assured that the comparison of the tests provided for the Tri-party agreement performance demonstration was being represented in the POI program for Appendix VIII, Supplement 11. Based on discussions at these meetings, the NRC Staff determined that the POI Program for provides an alternative that the proposed request for the qualification of personnel, procedures, and equipment will provide reasonable assurance of structural integrity.
4.0 CONCLUSION
The NRC staff has reviewed the licensees submittal and determined that, in accordance with 10 CFR 50.55a(a)(3)(i), use of the POI Program alternative to select paragraphs in Supplement 11 provides an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i),
the alternative proposed in Relief Request 2-ISI-21 is authorized for the third 1O-year lSI interval at Browns Ferry Nuclear Plant, Unit 2, that is scheduled to end May 24,2011. This authorization is limited to those components described in Section 3.1 above.
All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in this relief request remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: Carol A. Nove Oate: December 11, 2009
December 11, 2009 Mr. Preston D. Swafford Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 SUB~IECT: BROWNS FERRY NUCLEAR PLANT, UNIT 2 - CORRECTION TO LETTER AND SAFETY EVALUATION REGARDING THE THIRD TEN-YEAR INTERVAL INSERVICE INSPECTION PROGRAM RELATED TO THE EXAMINATION OF PIPING WELD OVERLAYS (TAC NO. ME1319)
Dear Mr. Swafford:
By letter dated May 22,2009, the Tennessee Valley Authority (TVA) requested relief (RR 2-ISI-21) from the requirements specified in the American Society of Mechanical Engineers Code,Section XI for inspecting piping weld overlays using ultrasonic testing under Title 10, Code of Federal Regulations, Section 50.55a(a)(3)(i) for the Browns Ferry Nuclear Plant, Unit 2. TVA informed the Nuclear Regulatory Commission (NRC) by letter dated October 5, 2009, that NRC's August 12, 2009, response to that request contained errors.
Enclosed is the corrected version of that response, in its entirety. Lines in the right margin indicate areas of the corrections. These corrections do not affect the NRC staff's conclusions associated with the safety evaluation for RR 2-ISI-21. We regret any inconvenience this may have caused.
If you have any questions regarding this matter, please call Ms. Eva Brown at (301) 415-2315.
Sincerely, IRA!
Thomas H. Boyce, Chief Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-260
Enclosure:
Corrected Letter cc w/enclosure: Distribution listserv Distribution:
PUBLIC LPL2-2 RtF Rids NrrPM BrownsFerry RidsNrrDorlLpl2-2 RidsAcrsAcnw_MailCTR RidsNrrDciCpnb RidsOgcRp RidsNrrLABClayton CNove DDiaz-Toro, EDO RidsRgn2MailCenter ADAMS Accession No*.. ML093340617 OFFICE LPL2-2/PM LPL2-2/LA CPNB/BC LPL2-2/BC NAME EBrown BClayton TChan by TBoyce memo DATE 12/07/09 12/03/09 01/29/09 12/11/09 OFFICIAL RECORD COpy