ML050590046
| ML050590046 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry, Watts Bar, Sequoyah  |
| Issue date: | 02/23/2005 |
| From: | Mashburn F Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML050590046 (14) | |
Text
Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402-2801 February 23, 2005 10 CFR 50.55a U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Stop: OWFN P1-35 Washington, D.C. 20555-0001 Gentlemen:
In the Matter of
)
Docket Nos.
50-259 50-260 Tennessee Valley Authority
)
50-296 50-327 50-328 50-390 BRO'VNNS FERRY NUCLEAR PLANT (BFN) UNITS 1, 2, AND 3, SEQUOYAH NUCLEAR PLANT (SQN) UNITS 1 AND 2, AND WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 - AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME)
BOILER AND PRESSURE VESSEL CODE, RELIEF-REQUEST TO USE ASME SECTION XI, APPENDIX VIII AND PERFORMANCE DEMONSTRATION INITIATIVE (PDI) FOR REACTOR VESSEL FLANGE WELDS - PDI-4 Pursuant to 10 CFR 50.55a(a)(3)(i), TVA requests approval of an alternative to ASME Section XI, paragraph IWA-2232, of applicable editions for the 10-year Reactor Pressure Vessel (RPV) examinations performed at BFN Units 2 and 3; BFN Unit I restart; future examinations at SQN Units I and 2, and Watts Bar Unit 1.
Specifically, TVA requests relief from the requirement to perform ultrasonic examination of RPV circumferential shell-to-flange welds using Section XI, Appendix I, that references ASME Section V, Article 4. TVA proposes to use the techniques, personnel, and equipment qualified to meet ASME Section XI, Appendix VIII, Supplements 4 and 6, of the 1995 Edition through the 1996 Addenda, as administered by the Electric Power Research Institute's (EPRI)
PDI, which considers the guidance of Regulatory Guide (RG) 1.150, Revision 1, "Ultrasonic Testing (UT) of Reactor Vessel Welds during Preservice and Inservice Examinations."
Performance of examinations by the PDI processes provides a better examination method. The proposed alternative represents the best available methodology in qualification of equipment and personnel performing ultrasonic examinations and uses an examination process that will provide the highest practical quality and greatest amount of coverage for the performance of the shell-to-flange weld examinations. In addition, this method will reduce personnel radiation exposure.
Proted onrecycled pape
U.S. Nuclear Regulatory Commission Page 2 February 23, 2005 The subject request is similar to relief request RR-04-GO-002 initially submitted by Duke-Energy for Oconee, McGuire, and Catawba Nuclear Stations on July 14, 2004 (ML042040261), and approved by NRC on October 20, 2004 (ML042810601).
TVA requests NRC review and approval to support work planned during near-term refueling outages at WBN, SQN, and work activities for BFN Unit I restart. TVA plans to proceed with the provisions described herewith for UT examination of RPV circumferential shell-to-flange welds at WBN, SQN, and BFN Unit 1. TVA understands that its relief request and the ability to rely on the subsequent examination results in order to meet the NRC requirements is subject to NRC review and approval in accordance with 10 CFR 50.55a(a)(3)(i).
There are no new regulatory commitments in this letter. If you have any questions, please call Rob Brown at (423) 751-7228.
Sincerely, Fredrick C. Mashburn Senior Program Manager Nuclear Licensing Enclosure cc (Enclosure):
Eva A. Brown (BFN Units 2 & 3), Project Manager U.S. Nuclear Regulatory Commission MS 08G9 One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2738 Margaret H. Chernoff (BFN Unit 1), Project Manager U.S. Nuclear Regulatory Commission MS 08G9 One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2738 Douglas V. Pickett, Project Manager (SQN &WBN)
U.S. Nuclear Regulatory Commission One White Flint North MS 08G9 11555 Rockville Pike Rockville, Maryland 20852-2738 cc: Continued on page 3
U.S. Nuclear Regulatory Commission Page 3 February 23, 2005 cc (Enclosure):
U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303-8931 NRC Senior Resident Inspector Browns Ferry Nuclear Plant 10833 Shaw Road Athens, Alabama 35611-6970 NRC Senior Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379-3624 NRC Senior Resident Inspector Watts Bar Nuclear Plant 1260 Nuclear Plant Road Spring City, Tennessee 37381-2000
ENCLOSURE TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN) UNITS 1, 2,3 SEQUOYAH NUCLEAR PLANT (SQN) UNITS 1, 2 WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) SECTION Xi, REQUEST FOR RELIEF USE OF APPENDIX VIII AND PERFORMANCE DEMONSTRATION INITIATIVE (PDI)
METHODOLOGIES FOR PERFORMANCE OF THE ULTRASONIC EXAMINATION OF REACTOR PRESSURE VESSEL SHELL-TO-FLANGE WELDS IN LIEU OF THE REQUIREMENT OF APPENDIX I AND THE ASSOCIATED ARTICLE 4, ASME SECTION V PDI-4 TVA requests approval of an alternative to ASME Section XI, paragraph IWA-2232 of applicable editions for the 10-year Reactor Pressure Vessel (RPV) examinations performed at Browns Ferry Units 2 and 3 and for future examinations at Browns Ferry Unit I (prior to restart), at Sequoyah Units I and 2, and at Watts Bar Unit 1.
EXECUTIVE
SUMMARY
In accordance with 10 CFR 50.55a(a)(3)(i), TVA is requesting relief from the specific requirements of performing the volumetric examination of the reactor pressure vessel (RPV) circumferential shell-to-flange welds in the subject TVA units in accordance with the requirement of Appendix I of Section XI.
In addition, the guidance of Regulatory Guide (RG) 1. 150, Revision 1, was historically applied with these processes. In lieu of the requirements of Appendix I and its associated sub-requirements of Article 4 of Section V, TVA will use the techniques, personnel, and equipment qualified to meet the requirements of ASME Section XI Appendix VIII, Supplements 4 and 6 of the 1995 Edition through the 1996 Addenda, as administered by the Electric Power Research Institute's (EPRI) Performance Demonstration Initiative (PDI) processes. TVA proposes to apply the alternative examination methodology to the BFN Unit 2 and 3 examinations already performed. TVA also plans to use the proposed alternative during the next regularly scheduled RPV examinations to be performed at or near the end of the current 10-year ISI Program intervals for each of the other units as indicated below.
Effectively, relief is requested to be approved for each of the six TVA operating units (five operating units, one unit currently in recovery from a long-term shutdown). This proposed alternative represents the best available methodology in qualification of equipment and personnel performing ultrasonic examinations and uses an examination process that has provided and will provide the highest practical quality and greatest amount of coverage for the performance of the shell-to-flange weld examinations.
As such, the proposed alternative methodology provides an acceptable level of quality and safety. In addition, the approval of this relief results in savings in the cost of performing the examinations, with not having to incorporate the use of two different sets of examination equipment, and also results in lower personnel radiation exposure from not having to use a different methodology for the shell-to-flange weld.
Note that this request for relief is similar to that requested in the Duke Energy Company request for the Oconee, McGuire, and Catawba Nuclear Stations, RR-04-GO-002, submitted initially in a letter to the Page El of 11
NRC, dated July 14, 2004 (see ML042040261) and approved by the Staff in a letter dated October 20, 2004 (see ML042810601).
I SYSTEM/COMPONENT(S) FOR WHICH RELIEF IS REQUESTED:
ASME Code Class I Reactor Pressure Vessel (RPV) Upper Vessel Shell-to-Flange Welds, Table IWB-2500-1 Category B-A, Item Number B 1.30, (originally Category B-C, Item No. B 1.3 for the BFN Unit I program in accordance with the 1974 Edition through the 1975 Summer Addenda) for:
BFN:
Unit I - TVA ISI Program Weld Designation I-C-5-FLG Unit 2 - TVA ISI Program Weld Designation 2-C-5-FLG Unit 3 - TVA ISI Program Weld Designation 3-C-5-FLG SQN:
Unit I - TVA ISI Program Weld Designation I-W06-07 Unit 2 - TVA ISI Program Weld Designation 2-W06-07 WBN: Unit I - TVA ISI Program Weld Designation W06-07 II APPLICABLE CODE EDITION AND ADDENDA FOR THE GIVEN EXAM The following table provides a summary of the examinations performed, (or to be performed), the applicable Units' ISI program interval and program Code-of-Record, the percentage of exam coverage obtained (or estimated to be obtained), and the dates when the examinations were performed, or when the examinations are currently next scheduled to be performed.
Page E2 of 11
TVA RPV SHELL-TO-FLANGE WELD EXAMINATIONS Plant/
Weld No.
1ISI Program Current 10-When Percent (%)
Unit ASME Section XI Year Interval Performed Coverage Code-of-Record and Dates or Obtained, or Edition/Addenda 2 W hen 3Estimated Currently Coverage Scheduled BFN / I I-C-5-FLG 1995 Edition with the 1" interval 2Prior to 3~95%, estimated, 1996 Addenda (re-restart as part based upon Unit 3 baseline 09/16/75 to I of the Unit I examination examinations) year after re-baseline results restart ISI exams (currently scheduled May, 2007)
BFN / 2 2-C-5-FLG 1995 Edition with the 3 d Interval Cycle 11 76.6% (see TVA 1996 Addenda
- outage, examination report 05/25/2001 to 04/03/2001
BFN / 3 3-C-5-FLG 1989 Edition 2nd Interval Cycle 11 95% (see TVA (No Addenda)
- outage, examination report 11/19/1996 to 03/15/2004
- R-212R) 11/18/2005 SQN / I I-W06-07 1989 Edition 2 d Interval 2Cycle 14 3>90%
(No Addenda) outage 12/16/1995 to 05/31/2006 SQN /2 2-W06-07 1989 Edition 2nd Interval 2Cycle 13 3>90%
(No Addenda) outage 12/16/1995 to 05/31/2006 WBN / I W06-07 1989 Edition 1St Interval 2Cycle 6 3>90%
(No Addenda) outage 05/27/1996 to 12/26/2006 Table Notes: (continued on next page)
Page E3 of 11
Table Notes:
(I)
TVA currently performs nondestructive examinations (NDE) in accordance with the methodologies and acceptance criteria shown in the requirements of the 1995 Edition through the 1996 Addenda of ASME Section XI, as approved by the NRC Staff. Component selection and the percentages of exams / number of exams are established in accordance with the base ISI Program Codes-of-Record for the given plantlunits' 10-year interval program.
(2)
Dates of actual examinations performed are as indicated. Dates for future examinations are shown as being performed during the outage when the exam is currently scheduled to be performed.
(3)
The estimated percentages of coverage for the future examinations are based upon past similar RPV examination results, or on estimates obtained through computer-aided graphical representations of the vessel welds and their required extent of examination volumes. The actual percent of coverage obtained will be dependent upon the physical configuration of the equipment and examination areas encountered during the conduct of the exams.
III CODE REOUIREMIENTS FRO1M WHICH RELIEF IS REOIJESTED:
In accordance with ASME Section XI, paragraph IWA-2232, "Ultrasonic examinations shall be conducted in accordance with Appendix I."
Further, in accordance with Appendix I, paragraph I-21 10(b) "Ultrasonic examination of reactor vessel-to-flange welds, closure head-to-flange welds, and integral attachment welds shall be conducted in accordance with Article 4 of Section V, except that alternative examination beam angles may be used."
IV RELIEF REOIJESTED:
Pursuant to 10 CFR 50.55a(a)(3)(i), TVA requests relief from performing the designated vessel shell-to-flange weld examination in accordance with the requirements of ASME Section XI, paragraph IWA-2232, Appendix I, and the associated Article 4 of Section V methodology in accordance with paragraph 1-2110(b).
V BASIS FOR RELIEF:
In accordance with ASME Section XI, Subarticle IWA-2232, TVA is required to perform ultrasonic examinations (UT) of the RPV upper shell-to-flange welds (at the indicated plants and units) using Section XI, Appendix I, which in turn requires the use of the NDE methodologies and processes of ASME Section V, Article 4. In addition, the guidance of RG-1.150, Revision 1, was historically applied.
The above listed welds are the only circumferential shell welds in the RPVs that are not examined in accordance with the requirements of ASME Section XI, Appendix VIII, as mandated in 10 CFR 50.55a with the issuance of the rule change shown in the Federal Register Notice 64 FR 51370, dated September 22, 1999. This rule change mandated the use of ASME Section XI, Appendix VIII, Supplements 4 and 6 for the conduct of RPV examinations. It has been recently stated in EPRI PDI coordination meetings between the PDI committee members and the NRC Staff representatives that the NRC Staff expectations are that licensees should submit requests for relief to use the more technically advanced Appendix VIII/PDI processes for the shell-to-flange weld exams, in lieu of the Section XI Appendix I and its associated Section V, Article 4 processes.
Page E4 of 11
VI PROPOSED ALTERNATIVES TVA proposes to use the procedures, personnel, and equipment qualified to meet the requirements of ASME Section XI Appendix VIII, Supplements 4 and 6 of the 1995 Edition through the 1996 Addenda, as administered by the Electric Power Research Institute's (EPRI) Performance Demonstration Initiative (PDI) processes to conduct the required vessel-to-flange weld examinations.
VII JUSTIFICATION FOR GRANTING RELIEF:
ASME Section V, Article 4, describes the required techniques to be used for the UT of welds in ferretic pressure vessels with wall thicknesses greater than 2 inches. The techniques were first published in ASME Section V in the 1974 Edition, summer 1975 Addenda. The calibration techniques, recording criteria and flaw sizing methods are based upon the use of a distance-amplitude-correction curve (DAC) derived from machined reflectors in a basic calibration block. UT performed in accordance with Section V, Article 4, used recording thresholds of 50 percent DAC for the outer 80 percent of the required examination volume and 20 percent DAC from the clad/base metal interface to the inner 20 percent margin of the examination volume. Indications detected in the designated exam volume portions, with amplitudes below these thresholds, were therefore not required to be recorded. Use of the Appendix VIILPDI processes would enhance the quality of the examination results reported because the detection sensitivity is more conservative and the procedure requires the examiner to evaluate all indications determined to be flaws regardless of their associated amplitude. The recording thresholds in Section V, Article 4, requirements and in the guidelines of RG-1.150, Revision 1, are generic and somewhat arbitrary and do not take into consideration such factors as flaw orientation, which can influence the amplitude of UT responses.
The EPRI Report NP-6273, "Accuracy of Ultrasonic Flaw Sizing Techniques for Reactor Pressure Vessels," dated March 1989, established that UT flaw sizing techniques based on tip diffraction are the most accurate. The qualified prescriptive-based UT procedures of ASME Section V, Article 4 have been applied in a controlled process with mockups of RPVs which contained real flaws and the results statistically analyzed according to the screening criteria in Appendix VIII of ASME Section XI. The results show that the procedures in Section V, Article 4, are less effective in detecting flaws than procedures qualified in accordance with Appendix VIII as administered by the PDI processes. Appendix VIII/PDI qualification procedures use the tip diffraction techniques for flaw sizing. The proposed alternative Appendix VIIIPDI UT methodology uses analysis tools based upon echo dynamic motion and tip diffraction criteria which has been validated, and is considered more accurate than the Section V, Article 4 processes.
UT performed in accordance with the Section V, Article 4 processes requires the use of beam angles of 00, 450, 60°, and 70° with recording criteria that precipitates equipment changes. Having to perform these process changes is time consuming and results in increased radiation exposure for the examination personnel. Having to comply with the specific ASME Section XI, Appendix I requirements for the RPV circumferential shell-to-flange weld, when the data is obtained using a less technically advanced process, results in an examination that does not provide a compensating increase in quality and safety for the higher costs and personnel exposures involved.
Past RPV shell-to-flange examinations already performed at TVA plants and units (i.e., for BFN Units 2 and 3) used automated and manual UT systems operated by qualified vendors. The examination coverage achieved during the 2001 exam of the Unit 2 weld (during the 2nd ISI program interval) resulted Page E5 of 11
in a coverage of approximately 76.6 percent which is less than the required essentially 100 percent.
Manual examination techniques were performed from the outside surfaces of the RPV during the Unit 2 examination in order to maximize the coverage. Examination coverage performed from the inside surfaces was limited due to the taper in the vessel wall at the edge of the weld area and the obstructions encountered with the guide rods and the steam nozzle plugs with the specific UT equipment used during the exam. The manual examination of the weld volume performed from the outside surfaces was limited by the flange configuration. This limited exam with a percentage of coverage of less than 90 percent was the subject of a BFN Unit 2 relief request number RR 2-ISI-14. This relief was reviewed by the NRC and found to be acceptable. A safety evaluation report (SER), on this relief, was issued by the NRC in a letter to J. A. Scalice, from Allen G. Howe, dated April 3, 2003, [see TAC NOS. MB5309, MB8130, MB8132, and MB8133 (ML030970815)]. The examination performed on the Unit 3 RPV used a different set of newer designed UT equipment and thereby achieved a calculated coverage of 95 percent.
Therefore, the Unit 3 examination results did not require the submittal and review of a relief request.
For future RPV shell-to-flange weld examinations TVA does not anticipate any less coverage than the required minimum of 90 percent of coverage. However, if any such limitations are encountered during the conduct of the examinations, separate individual relief requests will be submitted, as needed.
Sketches of the basic RPV shell-to-flange weld configurations for the six units addressed by this request are attached for information and use with this requested review and are shown as Figure 1, for BFN Units 1, 2, and 3; Figure 2a for SQN Unit 1, Figure 2b for SQN Unit 2, and Figure 3 for WBN Unit 1.
Procedures, equipment, and personnel qualified through the Appendix VIII, Supplements 4 and 6 PDI programs have shown to have a high probability of detection of flaws and are generally considered superior to the techniques employed earlier for RPV examinations. This results in increased reliability of RPV inspections and conditions where an acceptable level of quality and safety is provided with the proposed alternative methodologies. Accordingly, approval of this alternative evaluation process is requested pursuant to 10 CFR 50.55a(a)(3)(i).
VIII IMPLEMENTATION SCIIEDIJLE AND DURATION:
This alternative will be applied for BFN Units 1, 2, and 3; SQN Units I and 2, and WBN Unit I until the end of each unit's current ten-year ISI Program intervals when the unit's corresponding ISI and In-service Inspection programs are updated. With respect to BFN Unit 1, which is in an extended shutdown, the provisions of this request will be used during the performance of the currently planned restart examination of the RPV. The respective unit's current ISI program intervals are as follows:
BFN Unit I is currently in the third period of its first 10-year ISI program interval and is in an extended shutdown. In accordance with the ASME Section XI Unit I ISI Program Code of Record paragraph IWA-2400, the Unit I first ISI program interval will be extended by a period equal to the length of the extended shutdown. By letter dated March 1, 1988, TVA established that the current Unit I ISI program interval would be extended from its start on September 16, 1975 to a period of one year after restart of the unit. Unit I is currently scheduled for restart May, 2007.
BFN Unit 2 is currently in the second period of its third 10-year ISI program interval which extends from May 25, 2001 through May 24, 2011.
BFN Unit 3 is currently in the third period of its second 10-year ISI program interval which extends from November 19, 1996 through November 18, 2005.
Page E6 of 11
SQN Units I and 2 are currently in the third periods of their second program intervals which extend from December 16, 1995 through May 31, 2006.
WBN Unit I is currently in the third period of its first ten-year interval which extends from May 27, 1996 through December 26, 2006.
IX Precedents This request for relief is similar to, and closely follows the content and statements made in, the relief requested in the Duke Energy Company request for the Oconee, McGuire, and Catawba Nuclear Stations, RR-04-GO-002, submitted initially in a letter to the NRC, dated July 14, 2004 (see ML042040261) and approved by the Staff in a letter dated October 20, 2004 [see TAC NOS. MC3804, MC3805, MC3807, MC3810 (ML042810601)]. In addition, other similar approved requests include those for the Southem California Edison Company with the San Onofre Unit 3 in a letter dated January 3, 2003 [TAC No.
MB6708 (ML030150218)] and with the Public Service Enterprise Group Salem Unit I plant in a letter dated May 3, 2001 [TAC No. MB1234 (ML011060083)].
Page E7 of 11
Filurle I BFN Units 1 2. & 3 RPV F1ltae to Shell Weld T17
- (latl Thickness z 6" Nomiinal Ye, Nv1ii,.
I 7 k u III,,
Thick css I '3
)
Nomini al NI.ll. :1 Taper WI Id Ihickn css Page E8 of 11
Figure 2a SQN Ul VESSEL FLANGE DETAIL
-TOP OF tSSEL.70I-M CLOSJqe F".SE LYMAI-:J7>
"'.oW FRO 1~nj INSM:C 9RFAI Wt.H V
IRASDUCER CEP:C7E fiE-,U:RED EXAMiAT:Oh VOLU-E Weld Cl %I l Ns:Oriss'.MJ Ps F CL Nozzles Page E9 of 11
Figure 2b SQN U2 VESSEL FLANGE DETAIL TOP OF VESSEL-TOHEAD CLOSUER.
F~LAIGE t~.XA tATION VS LUNl FRO3 INSIDE SUqfACt
%w:1 H
%NSCLKZER C:CTED REQLUIRD LXAMINAtlOts
%lo-IME-INS:CE SURPA:E -
C:MtNhS:ONMS SlOA'N IN MH CL Ntozzles Page E10 of 11
Figure 3 WBN VESSEL FLANGE DETAIL TOP Of-VESSEL-7O-HLAO2 noCL ~uh!
Fv'rat I
I1 iC 1026 I
330 14 272 2171 W:rToN VOLUME-V FROM IMUM 9vAMut
- '.,T" IRANSCU tRV PAtWU:ZLD EXAtM:NA71-1h VCtUM!
"I R EntURED i
kX1MIfJ.TIOR y VLMf-E Rint I
4:
I 2
GWL7O 14:
1 275 7-~
-279 MrSME SUMJ-AC N
I Top eor CXCt ?IOZZfc WAc CNl1EJS:O'4S iHC.V'J 1'1 f-M CL Nozzles Page ElI of 11