ML12276A376
| ML12276A376 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 09/28/2012 |
| From: | Gillespie T Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML12276A376 (12) | |
Text
Duke T. PRESTON GILLESPIE, JR.
Vice President SEnergy Oconee Nuclear Station Duke Energy ONO0 VP / 7800 Rochester Hwy.
Seneca, SC 29672 September 28, 2012 864-873-4478 864-873-4208 fax U. S. Nuclear Regulatory Commission T.Gillespie@duke-energy.com ATTN: Document Control Desk Washington, DC 20555-0001
Subject:
Duke Energy Carolinas, LLC (Duke Energy)
Oconee Nuclear Station Units 1 and 2 Docket Numbers 50-269, -270 Relief Request 11-ON-001 Request for Additional Information (RAI) Response On December 23, 2011, Duke Energy submitted Relief Request 1 1-ON-001 (ADAMS Accession No. ML12009A091) pursuant to 10 CFR 50.55a(g)(5)(iii), requesting NRC approval from the requirement to examine 100% of the volume specified by the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code), Section Xl, Rules for Inservice Inspection of Nuclear Power Plant Components, 1998 Edition with 2000 Addenda (as modified by Code Case N-460).
On August 14, 2012, the NRC Staff electronically requested additional information regarding this relief request. The enclosure provides Duke Energy' s response. In addition please remove sections 27 and 28 of the Relief Request 1 1-ON-001 (for welds 2-51A-0029-94 and 2-HP-0396-23) because Duke Energy has determined that preservice examination of these welds was not required and relief is no longer needed.
This submittal document contains no regulatory commitments.
If you have any questions or require additional information, please contact Corey Gray of the Regulatory Affairs Group at (864) 873-6325.
Sincerely, T. Preston Gillespie Jr.,
Site Vice President
Enclosure:
Oconee Nuclear Station Unit 1 and 2 Duke Response to Request for Additional Information (RAI) Relief Request 11-ON-001 1EOC-25 and 2EOC-24 Limited Weld Examinations AWkr www. duke-energy, corn
U. S. Nuclear Regulatory Commission September 28, 2012 Page 2 xc (w/enclosure):
Victor Mcree Region II Administrator U. S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, Ga 30303-1257 John Boska Project Manager (by electronic mail only)
U. S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation 11555 Rockville Pike Rockville, MD 20852 cc: (w/o enclosure)
NRC Senior Resident Inspector Oconee Nuclear Station Susan Jenkins Section Manager Division of Waste Management Bureau of Land and Waste Management SC Dept. of Health & Environment Control 2600 Bull St.
Columbia, SC 29201
U. S. Nuclear Regulatory Commission September 28, 2012 Page 3 bxc w/enclosure:
ONS Information Service and Compliance ELL EC050 bxc w/o enclosure:
M. A. Pyne J. M. Boughman D. A. Cummings R. G. Sheffield S. H. Clark D. K. Zimmerman K. R. Alter C. A. Gray
Enclosure Oconee Nuclear Station Unit 1 and 2 Duke Response to Request for Additional Information (RAI)
Relief Request 11-ON-001 1 EOC-25 and 2EOC-24 Limited Weld Examinations RAI li-ON-Qol Page 1 RAI 11-0N-001 Page 1
2.0 REQUEST FOR ADDITIONAL INFORMATION RR 1 1-ON-001 2.1 General Information Required on Request for Relief 11-ON-001 For all welds in this request of relief, there was a check mark next to "Reject" under the results section on each of the data sheets, regardless whether there were indications detected. Please confirm that this is Duke Energy's procedure meant only for tracking purposes of examinations that do not meet the requirements of ASME Code Case N-460, Revision 16 "Alternative Examination Coverage for Class 1 and Class 2 Welds, Section X1, Division 1." If this is not the case, please confirm why all weld examination results are considered rejectable.
Duke Response:
Current Duke Energy procedures require ASME Code, Section X1 examinations that do not meet the requirements of Code Case N-460 to be marked "reject" for tracking purposes, regardless of whether indications were noted. This procedure requirement was first implemented in August 2007. Therefore, some limited exams in 11-ON-001 without indications were marked "reject".
2.2 Request for Relief 11-ON-001, Part A, ASME Code, Section Xl, Examination Category B-D, Items B3.110 and B3.150, Full Penetration Welded Nozzles in Vessels (ONS I and 2)
The licensee has provided only general, and somewhat vague, information regarding impracticality of obtaining ASME Code-required volumetric examinations. For example, the licensee's statement "limitation was caused by the design of the nozzle, " is inadequate to describe the basis for not obtaining the ASME Code-required examination volumes.
2.2.1 Please submit detailed and specific information to support the bases for limited examination in all requests for relief in ASME Code, Section X1, Examination Category B-D, and therefore, demonstrate impracticality.
a) Include detailed descriptions (written and/or sketches, as necessary) of the interferences to applied NDE techniques.
Duke Response:
B3.1 10 Pressurizer Nozzle to Head and Nozzle to Shell welds were examined to the maximum extent practical for the nozzle geometries. Coverage calculations and sketches illustrating the areas were provided in Attachments A and B in Relief Request 11-ON-001.
B3.150 Letdown Channel Body to Nozzle welds were examined to the maximum extent practical for the nozzle geometries. Coverage calculations and sketches illustrating the areas were provided in Attachments A and B in Relief Request 11-ON-001.
The coverage limitations for all category B-D welds were caused by the curvature of the scanning surface in the nozzle as it transitions from pipe to vessel. The curvature does not allow the sound wave to be directed into the entire required examination volume. To RAI li-ON-QOl Page 2 RAI 11-ON-001 Page 2
obtain the required coverage, the nozzle would need to be redesigned and replaced. This is impractical.
b) As applicable, describe NDE equipment (ultrasonic (UT) scanning apparatus), details of the listed obstructions (size, shape, proximity to the weld, etc.) to demonstrate accessibility limitations, and discuss whether alternative methods or advanced technologies could be employed to maximize ASME Code coverage.
Duke Response:
This component was scanned manually with conventional methods.
As described above, the limitation for each category B-D weld was caused by the curvature of the nozzle scanning surface. The sketches in Attachments A and B of the relief request show the nozzles are welded into the vessel which creates a scanning and coverage limitation on the nozzle side of the welds. Orientation of the nozzle in regard to the weld produced limited coverage of the nozzle to shell welds. Cross-sectional sketches that are provided are intended to illustrate the maximum coverage obtainable from each shear wave angle used in each examination. There were no other obstructions that limited coverage.
Alternative NDE methods such as radiography would not be practical because there is no access for film placement. Use of other manual or automated UT, whether conventional or phased array, qualified under ASME Section Xl, Appendix VIII would not increase coverage. Due to the limitation created by the configuration of the nozzle, as stated above, any other UT technique available would incur the same physical scanning limitations.
2.2.2 It is not clear from the information provided in the licensee's submittal which UT wave mode corresponds to each insonification angle for Items B3. 110 (ON, Unit 2) and B3.150 (ONS 1). Please clarify the wave modality and insonification angles used for all ultrasonic examinations performed on the pressurizer (PZR) (ONS 2) and letdown cooler (ONS 1) nozzle-to-vessel welds listed in ASME Code, Examination Category B-D.
Duke Response:
ONS 1 letdown cooler nozzle to vessel welds examinations were conducted using manual scanning employing combinations of 45°and 600 shear waves in the axial and circumferential direction along with a 700 refracted longitudinal wave in the axial direction.
ONS 2 pressurizer nozzle to vessel weld examinations were conducted using manual scanning employing combinations of 450 and 600 shear waves in the axial and circumferential direction plus a straight beam longitudinal wave.
RAI li-ON-QOl Page 3 RAI 11-ON-001 Page 3
2.3 Request for Relief II-ON-001, Part B, ASME Code, Section Xl, Examination Category B-J, Item B9.11, Pressure Retaining Welds in Piping (ONS I and 2) 2.3.1 Please describe NDE equipment (UT scanning apparatus) and discuss whether alternative methods or ASME Code, Section Xl, Appendix VII qualified advanced technologies could be employed to maximize ASME Code coverage.
Duke Response:
The B9.1 1 components were scanned manually with conventional methods. Scanning requirements are described in 10 CFR 50.55a(b)(2)(xv)(A)(1). These requirements describe and are specific to scanning components in two axial and two circumferential directions. This component was scanned to the extent possible to meet these requirements.
The B9.11 components were examined using procedures, equipment and personnel qualified in accordance with ASME Section Xl, Appendix VIII. Radiography (RT) is not a desired option because RT is limited in the ability to detect service induced flaws and has not been qualified through performance demonstration.
Use of other manual or automated UT techniques, whether conventional or phased array, qualified under ASME Section Xl, Appendix VIII would not increase coverage due to the limitation created by the component configuration. The use of any other technique available would incur the same physical scanning limitations.
2.3.2 Please state whether a full surface examination was performed on each of the piping welds and state whether any indications were discovered as a result of the surface examinations on each of the ASME Code, Class I piping welds for ONS 2.
Duke Response:
Original relief request sections 22, 23, and 24 (welds 2-PIAl-8, 2-PDA2-1, and 2-PDB2-1) did not receive a surface examination based on evaluation and application of ASME Code Case N 663, Alternative Requirements for Classes 1 and 2 Surface Examinations, Section Xl, Division 1. Since no surface examinations were performed, no surface indications were discovered.
2.4 Request for Relief II -ON-001, Part C, ASME Code, Section Xl, Examination Category C-F-I, Items C5.1I and C5.21, Pressure Retaining Welds in Austenitic Stainless Steel or High Alloy Piping (ONS I and 2)
For ONS 1, the licensee did not provided a description of the limitation for each of the subject welds. Only burden statements were provided of the modifications required to be performed in order to scan all of the ASME Code required volume.
2.4.1 Submit detailed and specific information to support the bases for limited examinations in all welds in ASME Code, Section X1, Examination Category C-F-1 (ONS 1) and therefore, demonstrate impracticality.
RAI li-ON-OQi Page 4 RAI 11-0N-001 Page 4
a) Include detailed descriptions (written and/or sketches, as necessary) of the interferences to applied NDE techniques.
b) As applicable, describe NDE equipment (UT scanning apparatus), details of the listed obstructions (size, shape, proximity to the weld, etc.) to demonstrate accessibility limitations, and discuss whether alternative methods or advanced technologies could be employed to maximize ASME Code coverage.
Duke Response:
Summary Number O1.C5.11.0028/Weld #1-53A-02-65L pipe to valve weld was scanned manually with conventional methods.
Scanning requirements are described in 10 CFR 50.55a(b)(2)(xv)(A)(1). These requirements describe and are specific to scanning components in two axial and two circumferential directions. This component was scanned to the extent possible to meet these requirements.
The impracticality was caused by the cast stainless steel material which cannot be effectively interrogated by ultrasound. There are currently no examination techniques that have been qualified through Appendix VIII. Therefore coverage could not be obtained by scanning from the valve side. In order to scan all of the required volume for this weld, the valve would have to be redesigned and replaced, which is impractical. See Attachment A in 11-ON-001 for detailed sketches.
This weld was examined using procedures, equipment and personnel qualified in accordance with ASME Section Xl, Appendix VIII. Radiography (RT) is not a desired option because RT is limited in the ability to detect service induced flaws and has not been qualified through performance demonstration. Use of other manual or automated UT techniques, whether conventional or phased array, qualified under ASME Section Xl, Appendix VIII would not increase coverage due to the limitation created by the component configuration. The use of any other technique available would incur the same physical scanning limitations.
Summary Number O1.C5.21.0004/Weld #1-51A-04-1C pipe to valve weld was scanned manually with conventional methods.
Scanning requirements are described in 10 CFR 50.55a(b)(2)(xv)(A)(1). These requirements describe and are specific to scanning components in two axial and two circumferential directions. This component was scanned to the extent possible to meet these requirements.
The impracticality was caused by the configuration of the valve body which did not allow access to the full volume of the weld. Therefore coverage could not be obtained by scanning from the valve side. In order to scan all of the required volume for this weld, the valve would have to be redesigned and replaced, which is impractical.
See Attachment A in 11-ON-001 for detailed sketches.
RAI 11-ON-001 Page 5
This weld was examined using procedures, equipment and personnel qualified in accordance with ASME Section Xl, Appendix VIII. Radiography (RT) is not a desired option because RT is limited in the ability to detect service induced flaws and has not been qualified through performance demonstration. Use of other manual or automated UT techniques, whether conventional or phased array, qualified under ASME Section Xl, Appendix VIII would not increase coverage due to the limitation created by the component configuration. The use of any other technique available would incur the same physical scanning limitations.
Summary Number O1.C21.0027NVeld #1 HP-387-118A elbow to valve weld was scanned manually with conventional methods.
Scanning requirements are described in 10 CFR 50.55a(b)(2)(xv)(A)(1). These requirements describe and are specific to scanning components in two axial and two circumferential directions. This component was scanned to the extent possible to meet these requirements.
The impracticality was caused by the configuration of the valve body which did not allow access to the full volume of the weld. Therefore coverage could not be obtained by scanning from the valve side. In order to scan all of the required volume for this weld, the valve would have to be redesigned and replaced, which is impractical.
See Attachment A in 11 -ON-001 for detailed sketches.
This weld was examined using procedures, equipment and personnel qualified in accordance with ASME Section Xl, Appendix VIII. Radiography (RT) is not a desired option because RT is limited in the ability to detect service induced flaws and has not been qualified through performance demonstration. Use of other manual or automated UT techniques, whether conventional or phased array, qualified under ASME Section Xl, Appendix VIII would not increase coverage due to the limitation created by the component configuration. The use of any other technique available would incur the same physical scanning limitations.
Summary Number O1.C21.0040NVeld #1 HP-1 93-17 pipe to tee weld was scanned manually with conventional methods. Scanning requirements are described in 10 CFR 50.55a(b)(2)(xv)(A)(1).
These requirements describe and are specific to scanning components in two axial and two circumferential directions. This component was scanned to the extent possible to meet these requirements.
The impracticality was caused by the configuration of the tee which did not allow access to the full volume of the weld. Therefore coverage could not be obtained by scanning from the tee side. In order to scan all of the required volume for this weld, the tee would have to be redesigned and replaced, which is impractical. See Attachment A in 11-ON-001 for detailed sketches.
RAI 11-ON-001 Page 6
This weld was examined using procedures, equipment and personnel qualified in accordance with ASME Section Xl, Appendix VIII. Radiography (RT) is not a desired option because RT is limited in the ability to detect service induced flaws and has not been qualified through performance demonstration. Use of other manual or automated UT techniques, whether conventional or phased array, qualified under ASME Section Xl, Appendix VIII would not increase coverage due to the limitation created by the component configuration. The use of any other technique available would incur the same physical scanning limitations.
Summary Number O1.C21.0051Neld #1-51A-02-16BH Pipe to flange weld was scanned manually with conventional methods.
Scanning requirements are described in 10 CFR 50.55a(b)(2)(xv)(A)(1). These requirements describe and are specific to scanning components in two axial and two circumferential directions. This component was scanned to the extent possible to meet these requirements.
The impracticality was caused by the configuration of the flange which did not allow access to the full volume of the weld. Therefore coverage could not be obtained by scanning from the flange side. In order to scan all of the required volume for this weld, the flange would have to be redesigned and replaced, which is impractical.
See Attachment A in 1 1-ON-001 for detailed sketches.
This weld was examined using procedures, equipment and personnel qualified in accordance with ASME Section Xl, Appendix VIII. Radiography (RT) is not a desired option because RT is limited in the ability to detect service induced flaws and has not been qualified through performance demonstration. Use of other manual or automated UT techniques, whether conventional or phased array, qualified under ASME Section Xl, Appendix VIII would not increase coverage due to the limitation created by the component configuration. The use of any other technique available would incur the same physical scanning limitations.
2.4.2 For Pipe-to-Valve Weld 1-51A-04-IC (ONS 1), confirm that the two indications found were acceptable per ASME Code, Section X1 criteria.
Duke Response:
The indications (two) detected during the examination were the result of component geometry, were not associated with flaws in the component weld, and were acceptable without further evaluation.
The indications were dispositioned using procedure guidance on probe skewing, use of higher angles, and indication plotting. The reject box on each UT Calibration/Examination sheet is marked for internal tracking of the coverage limitation only.
RAI 11-ON-OO1 Page 7 RAI 11-ON-001 Page 7
2.4.3 State whether a full surface examination was performed on each of the Pipe-to-Valve Welds ILP-251-27 and 2HP-341-VI (ONS 2) and state whether any indications were discovered as a result of the surface examinations on each of the welds.
Duke Response:
Original relief request section 25, and 26 (welds 2LP-215-27, 2HP-341-V1) did not receive a surface examination based on evaluation and application of ASME Code Case N 663, Alternative Requirements for Classes 1 and 2 Surface Examinations,Section XI, Division 1. Since no surface examinations were performed, no surface indications were discovered. Duke understands the RAI references weld # 1 LP-215-27, but the intent was to request additional information on weld 2LP-215-27 per email clarification from the NRC dated September 5, 2012.
2.4.4 The licensee's submittal states that the subject weld areas were interrogated with a combination of 38-, 45-, 60-, and/or 70-degree shear waves, and in some cases, 60- and 70-degree longitudinal waves (L-waves) were applied to detect circumferentially-oriented flaws.
The licensee's submittal further states that examinations were performed in accordance with ASME Code, Section X1, Appendix VIII (performance demonstration), and consisted of single-sided examinations.
Confirm the insonification angles and wave modalities used to examine each of the subject welds. Discussions with the industry's Performance Demonstration Initiative (PDI) administrator, the Electric Power Research Institute (EPRI), indicate that Supplement 2 qualifications require refracted longitudinal wave or 70-degree shear wave methods to be applied, as applicable, depending on thickness. If the pipe thickness was equal to or less than 0. 50-inches, please explain why 70-degree shear waves were not used. If only shear wave techniques were used to examine the subject stainless steel welds and the pipe thickness was greater than 0. 50-inches, please explain why refracted longitudinal wave techniques were not used as part of a "best effort" examination. The L-wave method has been shown capable of detecting planar inside diameter (ID) surface-breaking flaws on the far-side of wrought stainless steel welds. Recent studiesl,2,3 recommend the use of both shear and L-waves to obtain the best detection results, with minimum false calls, in austenitic welds. If both shear and L-waves were used please, state the "best effort" coverage achieved on the near-and far-side of the subject weld volumes.
Duke Response:
Duke Energy confirmed that the primary insonification angles and wave modalities used were either 38 or 45 degree shear waves in the circumferential direction, and either 45 or 60 degree shear waves in the axial direction. Supplemental insonification angles and wave modalities used were 60 degree longitudinal waves or 70 degree shear waves on single sided exams to supplement the missed coverage by the shear waves in the lower 1/3 region.
The requirements of the ASME Code, Section Xl, Supplement 2 pertaining to 60 degree refracted longitudinal wave or 70 degree shear wave methods are to be applied during single sided exams when axial scanning can only be performed from one side of the weld. Each limited axial examination reported in Category C-F-1 and C-F-2 was examined with a 60 degree refracted longitudinal wave for components greater than 0.50" or a 70 degree shear wave for components equal to or less than 0.50". Per EPRI RAI 11-ON-001 Page 8
procedure PDI-UT-2, the "best effort" examination wave mode is dependent on the pipe wall thickness. The weld coverage calculations that are reported in this Relief Request are based on the primary inspection angles only. "Best effort" coverage calculations are included for information only.
2.4.5 Below in Table 2.4, is a list of the ASME Code, Section X1, Examination Category C-F-1 welds contained in RR-11-ON-001, that required ASME Code, Section Il/, acceptance and preservice inspection examinations in accordance with ASME Code, Section XI:
Table 2.4 - ASME Code, Section Xl, Examination Category C-F-1 ON,
C5.21 1-HP-0187-184 Pipe-to-Valve IHP-140 I
C5.21 1-HP-0187-185 Pipe-to-Valve 1HP-139 2
C5.21 2-51A-0029-94 Pipe-to-Valve 2HP-139 2
C5.21 2HP-0396-23 Pipe-to-Valve 2HP-140 Briefly describe the nondestructive examinations that were performed on the subject welds contained in Table 2.4 above during the repair/replacement activities of the subject components, including examinations for ASME Code, Section Il/, acceptance and preservice inspection in accordance with ASME Code, Section X1. State whether or not any indications were observed as a result of the ASME Code-required repair/replacement or preservice examinations that could interfere with any future inservice inspection UT examinations.
Duke Response:
In accordance with an email from NRC dated September 5, 2012, the two Unit 1 welds in Table 2.4 were removed from the scope of the RAI. Duke Energy also withdraws entire sections 27 and 28 (welds 2-51A-0029-94 and 2-HP-0396-23) from 11-ON-001. As a result, no other information is provided in this response.