ML11201A302
| ML11201A302 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 07/18/2011 |
| From: | Krich R Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML11201A302 (19) | |
Text
Tennessee Valley Authority 1101 Market Street, LP 3R Chattanooga, Tennessee 37402-2801 R. M. Krich Vice President Nuclear Licensing July 18, 2011 10 CFR 50.4 10 CFR 50.55a ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Unit 3 Facility Operating License No. DPR-68 NRC Docket No. 50-296
Subject:
Response to NRC Request for Additional Information Regarding Relief Request 3-ISI-25
References:
- 1. NRC Letter to TVA, "Browns Ferry Nuclear Plant, Unit 3 -
Request for Additional Information Regarding Relief Request 3-ISI-25 (TAC No. ME5400)," dated June 9, 2011
- 2. TVA Letter to NRC, "American Society of Mechanical Engineers,Section XI Inservice Inspection Program for the Unit 3 Third Ten-Year Inspection Interval, Request for Relief 3-1SI-25," dated January 21, 2011 On January 21, 2011, the Tennessee Valley Authority (TVA) submitted request for relief 3-1SI-25 for Browns Ferry Nuclear Plant, Unit 3 (Reference 2). On June 9, 2011, the NRC transmitted a request for additional information (RAI) (Reference 1).
The enclosures to this letter provide the TVA response to the RAI. The due date for this response is July 18, 2011.
printed on recycled paper
U.S. Nuclear Regulatory Commission Page 2 July 18, 2011 There are no new regulatory commitments contained in this letter. Please direct any questions concerning this matter to Tom Matthews at (423) 751-2687.
Respectfully, R. M. Krich
Enclosures:
- 1. TVA Response to NRC Request for Additional Information
- 2. Weld Diagrams cc (Enclosures):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant
ENCLOSUREI Tennessee Valley Authority Browns Ferry Nuclear Plant, Unit 3 Request for Relief 3-1SI-25, Updated Risk Informed Inservice Inspection Program TVA Response to NRC Request for Additional Information NRC Request for Additional Information Introduction By letter dated January 21, 2011, the Tennessee Valley Authority (the licensee) submitted Relief Request 3-ISI-25 requesting relief from the weld examination coverage requirements specified in American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section Xl, 2001 Edition, as amended by Title 10 of the Code of Federal Regulations, Section 50.55a (b)(2)(xv)(A)(2), for seven full penetration welds due to access limitations caused by design. These welds include three Residual Heat Removal (RHR) System full penetration piping welds, two Reactor Water Cleanup (RWCU) System full penetration piping welds, and two High Pressure Coolant Injection System full penetration piping welds.
The U.S. Nuclear Regulatory Commission staff requests that the licensee provide additional information to support the relief from ASME Code Section XI-required volumetric examination of essentially 100 percent of the seven full-penetration welds.
NRC Question 1:
Please provide a detailed diagram, identifying the materials (stainless steel, carbon steel, nickel alloy) of the base metal, weld, and buttering and show dimensions (nominal inside diameter (ID), outside diameter (OD), and wall thickness) of the flued head to valve configuration for welds DRHR-3-03, DRHR-3-12, and DRHR-3-21, to address questions about the geometry and materials in the residual heat removal system fluid [sic] head to valve welds.
TVA Response: of this response includes two Wall Thickness Profile Sheets for welds DRHR-3-03 and DRHR-3-12, in addition to the diagrams previously submitted with the original relief request dated January 21, 2011.
The weld Wall Thickness Profile Sheets show details of the welds taken by ultrasonic testing (UT) examiners during the examinations. They show the wall thickness, the contour of the examination area and location of the weld, crown height and width, weld length, and nominal pipe diameter. Since the welds are essentially uniform around their circumference, only one measurement was taken on each weld.
El-1
The Wall Thickness Profile Sheet for weld DRHR-3-21 was performed eight years after the other two welds and shows the coverage scans. The difference in the information provided is due to updated procedural requirements.
Additionally, the detailed descriptions of composition materials are:
a) Weld DRHR-3-03 is a nominal 24" Valve to Flued Head weld. Actual thicknesses can be found on the Wall Thickness Profile Sheets. The material is cast stainless steel A-351 CF8M to forged stainless steel SA-1 82 GR F304.
Weld DRHR-3-03 has an ER308 and/or E308 filler material. This was derived from TVA's weld filler material matrix in G29 General Welding Procedure 1.M.1.2 (3.0). Per this matrix, the CF8M grade is equivalent to grade 316. The matrix states that 304 grade material welded to 316 grade material indicates a weld filler material of ER308 (for GTAW) and/or E308 (for SMAW) for the welding process.
b) Weld DRHR-3-12 is a nominal 24" Valve to Flued Head weld. Actual thicknesses can be found on the Wall Thickness Profile Sheets. The material is cast stainless steel A-351 CF8M to forged stainless steel SA-182 GR F304. Weld DRHR-3-12 has an ER308 and/or E308 filler material.
c) Weld DRHR-3-21 is a nominal 20" OD Elbow to Valve piping weld with a nominal thickness of 1.031". Actual thicknesses can be found on the Wall Thickness Profile Sheets. The material is stainless steel A403 WP304 to cast stainless steel A351 CF8M.
Weld DRHR-3-21 has an ER308 and/or E308 filler material.
Please note that only one of the components listed above, an elbow, is actually a piping component, so nominal thickness can be misleading. Elbows of this size may be thicker than nominal due to the manufacturing process. Valves and flued heads typically are thicker than the piping components to which they are welded. They are machined to fit each other either in the shop or field, so actual thicknesses are the only appropriate measure. The actual thickness of the components and welds can be found on the Wall Thickness Profile Sheets.
ID measurements are determined by subtracting the actual thickness from the nominal OD dimensions.
NRC Question 2:
The diagrams provided in the submittal showed obstructions for scans performed from the OD surface and appear free of obstructions from the ID surface. Provide a discussion on the feasibility of using different nondestructive examination methods to examine the ID surface for surface-breaking flaws.
E1-2
TVA Response:
Access to the ID of Reactor Coolant System (RCS) valves is difficult due to their configuration and the relatively long distances an examiner would need to reach into the valve bodies to do proper examinations. Personnel would need to physically enter the valve bodies and reach for the ID surface of the welds. These valve body entries would result in high radiation doses and potential personnel contamination because the internal RCS piping systems are highly contaminated.
It is unlikely that valid surface examinations could be performed as found after disassembly of the valves.
Without a proper weld preparation, a dye liquid penetrant examination could not be performed, as corrosion products and other small debris can accumulate in the area of interest, thus interfering with the examination. The weld would need to be prepped and corrosion products removed.
The preparation of the ID surface within a constricted and confined space of the valve interior body while wearing personnel protective equipment would impair manual dexterity and cause limited visibility of the weld area. Furthermore, the preparation of the ID of the weld might introduce foreign material, such as loose sanding dust or metal shavings, into the affected RCS piping. The potential for having this undiscovered debris migrate to undesirable RCS locations during power operation is high, leading to undesired consequences.
There is currently no UT examination technique qualified for the ID surface of welds. Again, if a UT technique was qualified, some preparation of the ID weld surface would likely be needed to provide an adequate surface for the examination.
The only other feasible volumetric method of the ID region is radiography (RT). There is currently no Electric Power Research Institute Performance Demonstration Initiative (EPRI PDI) qualified technique for RT on piping welds.
Based on the above discussion, different nondestructive examination methods to examine the ID surface for surface-breaking flaws are not considered to be feasible.
NRC Question 3:
The difficulties in obtaining coverage in several welds seem to be caused by the use of fixed-angle probes with a limited area available for scanning. Provide a discussion of alternative examination methods and techniques, such as phased-array ultrasonic techniques (line scan or raster) that cover many angles, which can be used to obtain greater coverage for welds RWCU-3-001-070, DRHR-3-03, DRHR-3-12, and DRHR-03-21.
TVA Response:
TVA has investigated the possible use of other techniques and phased array for all the welds mentioned above with limitations, but has concluded that other methods and techniques do not provide any additional coverage beyond that of conventional UT. The primary limitations are the EPRI PDI procedure requirements of the permitted angles and the physical construction E1-3
differences between the types of transducers and wedges. The Appendix VIII Phased Array procedure, EPRI-PIPE-MPA-1, requires a 35 degree impingement angle at the ID surface. PDI-UT-2, Revision C has very specific angle requirements for the examination of welds based on performance qualifications. The angles used for the examinations were in accordance with the procedure. The different angle of the Phased Array technique was evaluated for use and would actually achieve less coverage than the conventional technique.
NRC Question 4:
This information request concerns the coverage limitations for welds DRHR-3-03 and DRHR-3-12, based on the drawings and Table 1. Please explain why single-sided coverage and Section 50.55a (b)(2)(xv)(A)(2) are cited as a limitation in Table 1 for DRHR-3-03 and DRHR-3-12, when the drawings show that the calculated coverage for welds DRHR-3-03 and DRHR-3-12 includes examinations from both sides of the weld.
TVA Response:
Welds DRHR-3-03 and DRHR-3-12 were examined from both sides, so the Code of Federal Regulations (CFR) reference should not have been cited in the original relief request for these welds. The stated examination coverage was the maximum possible utilizing a two-sided examination technique within the limitations of the weld and adjacent component configurations.
The two identified welds in Table 1 (shown below) have been corrected by removing the cited CFR listed under the comments column.
Weld No.
Nominal ISI Examination Unit I Comments (System)
Pipe Drawing Coverage Refueling Size No.
Percent Cycle (NPS)
(Date)
DRHR-3-03 24" 3-ISI-0330-C 62.5%
3/13 Limitations due to (Residual component Heat (Spring configuration, Removal 2008) flued head to System) valve.
DRHR-3-12 24" 3-ISI-0330-C 62.5%
3 /13 Limitations due to (Residual component Heat (Spring configuration, Removal 2008) flued head to System) valve.
NRC Question 5:
Although the Appendix VIII performance demonstration, as administered by the Performance Demonstration Initiative (PDI) program, identifies the coverage from one direction as 50 percent (based on examinations performed from the base metal to the centerline of the weld), the performance demonstration also includes flaws on the other side of the weld centerline. PDI identifies the area on the other side of the weld centerline as "best effort." Were any E1-4
examinations conducted on these welds that would be deemed by PDI as "best effort"? If so, were any indications found?
TVA Response:
Following the procedural requirements of PDI-UT-2, Section 1.8a, Revision C, a best effort exam was performed on the far side of welds DRHR-3-21 and RWCU-3-001-070. No recordable indications were found on these welds during this best effort examination, and root geometry was recorded on weld RWCU-3-001-070.
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ENCLOSURE 2 Tennessee Valley Authority Browns Ferry Nuclear Plant, Unit 3 Request for Relief 3-ISI-25, Updated Risk Informed Inservice Inspection Program Weld Diagrams DRHR-3-03 DRHR-3-12 DRHR-3-21
000242 1 li TENNESSEE VALLEY AUTIHORITY EXAMINATION SIUMMARY AND RESOLUTION DATA SHEET REPORT NUMBER:
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J Valve TO Flued Head EXAMINER-EXAMINER:
EXAMINER:
EXAMINER:
LEL:LEVEL LEVEL:
LEVEL:
The package contns the ultrasonic examination data for DRHR-3-03.
This exam meets the requirements of NUREG 0313 for [GSCC.
The examination was performed using ASMjE Section XI, Appendix VII and Appendix VITI personnel, equipment and techniques as amended by the 10CFRS0.55a Final Rule The joint configuration is a valve to flued head full pen butt weld.
The examination was performed using TVA Procedure N-UT-64 which implements PDI Procedure PDl-UT-2 for Austeni-tic pipe welds The weld was examined using 45 degree shear wave for axial and circumfrerential scan directions. 60 and 70 degree shear waves were also used for scans in the axial direction.
The achieved examination volume was 62:5%
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The package contains the ultrasonic examination data for DRHR.3-12.
This exam meets the requirements of NUREG 0313 and ASME Section Xl 2001 edition, 2003 Addenda, Category R-A, item RI.16G, EXREQ B02-02 The examination was perlbrmed using ASME Secticm XI, Appendix V11 and Appendix VIII personnel, equipment and techniques as amended by the 10CFR50.55a Final Rule The joint configuration is a valve to flued head tull pen butt weld.
The examination was perfbrmed using TVA Procedure N-UT-64 which implements PDI Procedure PDT-UT-2 for Austenitic pipe welds.
The weld was examined using 45 degree shear wave for axial and circumferential scan directions. 60 and 70 degree shear waves were also used for scans in the axial direction.
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This report contains the data associated with the manual ultrasonic examination weld DRHR3-21.
The exam was performed to meet the requirements of NU0313, EXREQ B02-02 Category C and ASME Section XI 2001 Edition 2003 Addenda, Category R-A, Item RI.16C.
This exam was performed using equipment, procedures and personnel qualified in accordance with ASME Section XI, Appendix VIII as amended by I OCFR50.55a final rule.
This exam was performed using TVA Nuclear Procedure N-UT-64 Rev. 11 which incorporates PDI-UT 2 Rev C Addenda No. 1,2, and 3, for UT examination Austenitic Welds..
The component was a single sided stainless steel piping weld, 20 inch diameter schedule 80 1.031" nominal Elbow to Valve weld, which limited the upstream scan due to configuration.
A 450 Shear and a 600 RI. was used for the axial scans and a 450 Shear for circ scans.
-53.75 Coverage Achieved.
RESOLUIJTON BY: Tommy Brw0 REVIEWED BY: Matt Welch ANIPF D
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