ML071020109
| ML071020109 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 04/05/2007 |
| From: | James Smith Tennessee Valley Authority |
| To: | Document Control Desk, NRC/NRR/ADRO |
| References | |
| Download: ML071020109 (21) | |
Text
l Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381-2000 APR o 5 2007 10 CFR 50.55a U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Gentlemen:
In the Matter of Tennessee Valley Authority
))
Docket No. 50-390 WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 - AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) INSERVICE INSPECTION (ISI) PROGRAM REQUEST FOR RELIEF 1-ISI-20
Reference:
TVA Letter to NRC dated February 21, 2007, "Watts Bar Nuclear Plant (WBN)
Unit 1 - American Society of Mechanical Engineers (ASME)Section XI Inservice Inspection (ISI) Summnary Report for the Seventh Cycle of Operation."
The purpose of this letter is to request relief from ASME Section XI Code required examinations due to limitations which were identified in the WBN Unit 1 Cycle 7 Refueling Outage. This request for relief is being submitted in accordance with 10 CFR 50.55a(g)(5)(iii).
TVA stated in the above referenced report that a request for relief was required to be written for a component examined during the inspection and this request would be submitted under separate letter. The required examination coverage could not be achieved for the pressurizer surge line nozzle-to-vessel weld due to the configuration of the pressurizer bottom head. Enclosure 1 provides request for relief 1-ISI-20 for the pressurizer surge line nozzle-to-vessel weld. provides the examination data sheets for weld WP-10.
A041-7 Printed on recycled paper
U.S. Nuclear Regulatory Commission Page 2 APR 0 5 2007 There are no regulatory commitments associated with this submittal. If you have any questions concerning this matter, please call me at (423) 365-1824.
Sincerely, J. D. Smith Manager, Site Licensing and Industry Affairs (Acting)
Enclosures
- 1.
Request for Relief 1-ISI-20
- 2.
Examination Data Sheets for Weld WP-10 cc: See Page 3
U.S. Nuclear Regulatory Commission Page 3 APR 0 5 2007 Enclosures cc (Enclosures):
NRC Resident Inspector Watts Bar Nuclear Plant 1260 Nuclear Plant Road Spring City, Tennessee 37381 Mr. Brendan T. Moroney, Project Manager U.S. Nuclear Regulatory Commission MS 08G9a One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2738 U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303 Watts Bar Nuclear Plant (WBN) Unit 1 American Society of Mechanical Engineers (ASME)
Inservice Inspection Program Request for Relief 1-ISI-20 Summal-ý:
Due to design configuration of the pressurizer bottom head, volumetric examination of the surge nozzle-to-vessel weld, WP-10, during the Unit 1 Cycle 7 refueling outage resulted in less than essentially 100 percent (%) of ASME code coverage being achieved. The proximity of the pressurizer heaters to the surge nozzle interferes with performance of an ultrasonic scan from the vessel side scanning perpendicular to the weld and the curvature of the surge line nozzle limits access when scanning perpendicular to the weld from the nozzle side, thus preventing essentially 100% examination of the required full volume. Volumetric examination of this component is required in accordance with ASME Section XM Table lWB-2500-1, Examination Category B-D, Item Number B3. 110. The full volume weld examination requirement is illustrated by Figure TWB-2500-7(b).
An inservice ultrasonic examination was performed on accessible areas to the maximum extent practical, given the physical limitations of the surge line nozzle-to-vessel weld. The design configuration limits the best effort ultrasonic examination to approximately 55% of the required volume of the nozzle-to-vessel weld. The volumetric examinations resulted in no recordable indications for the nozzle-to-vessel weld. Ultrasonic examination to the maximum extent allowed by the designed configuration provides reasonable assurance of an acceptable level of quality and safety. The information and data obtained from the volume examined provides sufficient information to judge the overall integrity of the surge line nozzle-to-vessel weld.
In accordance with 10 CFR 50.55a (g) (5) (iii), an exemption is requested from the extent of examination requirement due to physical restrictions. Relief is requested from these examinations because the code requirement is impractical to implement.
El-i Watts Bar Nuclear Plant (WBN) Unit 1 American Society of Mechanical Engineers (ASME)
Inservice Inspection Program Request for Relief 1-ISI-20 ASME Section Xl Code Edition/Addenda:
The Watts Bar Nuclear Plant Unit 1 Code of Record is the 1989 Edition, no addenda.
Component:
Pressurizer surge line Nozzle-to-Vessel Weld Weld Identifier WP-10 Reference ISI Drawing CHM-2570-C-01 and CHM-2570-C-05 Code Requirement:
ASME Section XI, 1989 Edition, Table IWB-2500-1, Examination Category B-D, Item Number B3. 110, Pressurizer Nozzle-to-Vessel Welds, examination requirement as defined by Figure IWB-2500-7(b).
Code Requirements From Which Relief Is Requested:
Relief is requested from performing the required volumetric examination on essentially 100% of the pressurizer surge line nozzle-to-vessel weld.
Basis for Relief:
The design configuration of the pressurizer surge line nozzle precludes a volumetric examination of the required volume for the pressurizer surge line nozzle-to-vessel weld from either the pressurizer side or the nozzle side. The configuration limits the volumetric examination of the code required examination volume to 55%. Reference Enclosure 2, Examination Summary and Resolution Sheet, Report Number R-1178, for a description of the limitations and areas examined.
Alternative Examination:
In lieu of the code required 100% volumetric examination, an ultrasonic examination was performed on accessible areas to the maximum extent practical given the physical limitations of the nozzle-to-vessel weld. Refer to Enclosure 2 Attachments for the examination data reports.
El-2 Watts Bar Nuclear Plant (WBN) Unit 1 American Society of Mechanical Engineers (ASME)
Inservice Inspection Program Request for Relief 1-ISI-20 Justification For The Granting Of Relief.
The design configuration of the pressurizer surge line nozzle precludes ultrasonic examination of essentially 100% of the nozzle-to-vessel weld. The nozzle-to-vessel weld examination was performed by manual ultrasonic (UT) scanning equipment. The target scope of the examinations included 100% of the accessible weld. The examination coverage requirements and actual areas scanned for nozzle-to-vessel weld is discussed in Enclosure 2. Examination of the nozzle-to-vessel weld is obstructed from the pressurizer side by the proximity of the heater assemblies and from the nozzle side by curvature of the nozzle. The design configuration allows for ultrasonic examination of approximately 55% of the required volume.
The ASME Section XI code requirements for reflectors oriented parallel and transverse to the weld stipulate that the angle beam search units shall be aimed, with the search unit manipulated, so that the ultrasonic beams pass throughout the entire volume of weld metal. The required examination volume A-B-C-D-E-F-G-H is depicted on ASME Section XI Figure IWB-2500-7(b).
In order to examine the pressurizer surge line nozzle-to-vessel weld in accordance with the code requirement, the pressurizer would require extensive modification. This modification would be impractical to implement. Other examination techniques were also determined to be impractical for this configuration. Due to the design configuration of the surge line nozzle-to-vessel weld and the pressurizer, ultrasonic examination from inside surface of the pressurizer is impractical. Radiographic examination as an alternative volumetric examination method was also determined to be impractical.
Limited two direction transverse scans and parallel scans were performed as depicted in. No reportable indications were identified based on the scans performed.
Ultrasonic examination to the maximum extent practical provides reasonable assurance of an acceptable level of quality and safety. The information and data obtained from the volume examined provides sufficient information to judge the overall integrity of the pressurizer surge line nozzle-to-vessel weld.
Conformance with the referenced code requirement is impractical, therefore, this request for relief is submitted pursuant to 10CFR 50.55a (g) (5) (iii).
Implementation Schedule:
This request for relief is applicable to WBN's first 10-year inspection interval.
El-3 Watts Bar Nuclear Plant (WBN) Unit 1 American Society of Mechanical Engineers (ASME)
Inservice Inspection Program Request for Relief 1 -ISI-20 Examination Data Sheets for Weld WP-10 (Report R-1178, 14 pages)
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1 NONDESTRUCTIVE EXAMINATION PROCEDURE Procedure No. N-GP-23 TVA Nuclear Power Revision 5 Page 6 of 8 9.0 Ultrasonic Examinations - Vessel Welds NOTE: THIS IS NOT APPLICABLE FOR APPENDIX VIII EXAMINATIONS OF THE RPV WELDS.
9.1 Examination volume coverage calculations are based upon the folloMing suppositions:
a)
To achieve full examination coverage nine different scans are required for a typical vessel weld or nozzle examination. The following may be used for other vessel configurations:
aAk 1) 2)3) 4)
5) 6)
7) 6)
9) 0 degree (weld metal scan) 45 degree Transverse-scan from vessel side of the weld 45 degree Transverse-scan from nozzle side of the weld 60 degree Transverse-scan from vessel side of the weld 60 degree Transverse-scan from nozzle side of the weld 45 degree Parallel-scan CW direction 45 degree Parallel-scan CCW direction 60 degree Parallel-scan CW direction 60 degree Parallel-scan CCW direction 9.2 The examination volume achieved for each above examination scan shall be obtained and documented on a percentage basis. This calculation considers the required examination volume required per the ASME Section Xl Code.
a)
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