ML042240259
| ML042240259 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 08/06/2004 |
| From: | Pace P Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TAC MC2368, TAC MC2369 | |
| Download: ML042240259 (21) | |
Text
Tennessee Valley Authority, Post Office Box 2000, Spnng City, Tennessee 37381-2000 AUG 0 6 2004 10 CFR 50.55a U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 Gentlemen:
In the Matter of ) Docket No.50-390 Tennessee Valley Authority WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 - AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) INSERVICE INSPECTION (ISI) PROGRAM REQUEST FOR RELIEF 1-ISI-14 AND 1-ISI RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION (TAC NOS. MC2368 AND MC2369)
The purpose of this letter is to respond to NRC's request for additional information received from the Watts Bar Project Manager by electronic mail (e-mail) on June 23, 2004, concerning the subject request for relief. TVA submitted the request for relief on March 19, 2004. The Enclosure provides TVA's responses to NRC's questions.
There are no regulatory commitments identified in this letter.
If you have any questions concerning these responses, please contact me at (423) 365-1824.
Sincerely, Pace Manager, Site Licensing and Industry Affairs Enclosure cc: See page 2 C47 Pnted on mcyced pape
U.S. Nuclear Regulatory Commission Page 2 AUG 0 6 2004 cc (Enclosure):
NRC Resident Inspector Watts Bar Nuclear Plant 1260 Nuclear Plant Road Spring City, Tennessee 37381 Ms. Margaret H. Chernoff, Project Manager U.S. Nuclear Regulatory Commission MS 08G9 One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2738 Mr. M. M. Comar, Project Manager U.S. Nuclear Regulatory Commission MS 08G9 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
ENCLOSURE WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME)
REQUEST FOR RELIEF 1-ISI-14 AND 1-ISI-15 REQUEST FOR ADDITIONAL INFORMATION By letter dated March 19, 2004, TVA submitted for staff review and approval proposed Requests for Relief Nos. 1-ISI-14 and 1-ISI-15. These requests were seeking relief from the requirements of the ASME Code, Section XI, for the first 10-year inservice inspection (ISI) interval at WBN Unit 1. In order to complete the review, the staff has requested by electronic mail on June 23, 2004, the following additional information:
NRC Questions for Both Relief Requests 1-ISI-14 and 1-ISI-15 QUESTION 1 Provide beginning and end dates for the first 10 year inspection interval for both relief requests.
Response
The WBN first 10 year inspection interval began May 27, 1996 and ends December 26, 2006.
QUESTION 2 TVA examined the subject welds in both relief requests during refueling Cycle 5 and discussed the weld examination coverage in the attachment to the March 19, 2004, letter. Discuss the inspection results.
Response
The ultrasonic examination of welds WP-l1, WP-12, WP-13, WP-14, WP-15, and SIF-D086-02 resulted in no recordable indications.
The ultrasonic examination of weld RHRF-D054-09 revealed geometric reflectors originating from the weld root and counter bore areas.
E-1
ENCLOSURE WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME)
REQUEST FOR RELIEF 1-ISI-14 AND 1-ISI-15 REQUEST FOR ADDITIONAL INFORMATION QUESTIONS ON RELIEF REQUEST 1-ISI-14 QUESTION 3 On Page E1-2,Section V, TVA stated that the design configuration limits ultrasonic examination to about 68 percent of the required examination.
(a) Discuss whether each of the subject welds has the same volume and design configuration (i.e., WP-11, WP-13, WP-14, and WP-15);
Response 3(a)
The configuration of WP-11, WP-12, WP-13, WP-14, and WP-15 are essentially identical as the welds are all nozzle to pressurizer upper head welds.
(b) Discuss whether the proposed 68 percent examination covers the same volume and area of each of the five subject weld metal. If the 68 percent examination covers the same volume in each weld, then there would be no inspection data on the remaining 32 percent volume. It is preferable that the 68 percentage examination would cover different parts of the five welds so that, as a group, the condition of the entire volume would be covered; Response 3(b)
The ultrasonic examination limitations are essentially the same for all five welds. The percent of the total weld volume covered in each of the limited welds is comprised of the volume defined by the visible areas (within the ultrasonic testing (UT) beam projection) shown in Attachment 1 cross-sectional drawings when the depicted area is scanned for the full circumferential length around each of the nozzles. A copy of the TVA procedure used to calculate the volumes covered is provided in Attachment 4.
E-2
ENCLOSURE WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME)
REQUEST FOR RELIEF 1-ISI-14 AND 1-ISI-15 REQUEST FOR ADDITIONAL INFORMATION (c) Discuss whether the 68 percent volumetric examination will cover the inside (ID) and outside (OD) surface areas of the subject welds; Response 3(c)
The ultrasonic examinations of the subject welds are limited on the inside and outside surfaces. See Attachment 1 for a depiction of the ultrasonic examination coverage.
(d) Discuss the percentage of the examination coverage for the upper portion and root of the weld; and Response 3(d)
The ultrasonic examination of the root area and upper portion of the weld is limited when scanning away from the nozzle and the ultrasonic beam directed perpendicular to the weld. See Attachment 1 for a depiction of the ultrasonic examination coverage.
(e) Discuss the percentage of examination coverage on the interface (i.e., surface areas) between the weld metal and base metal in which lack of fusion usually originates.
Response 3(e)
The ultrasonic examination of weld metal/base metal interface is limited when the beam is directed perpendicular to the weld and scanning away from the nozzle. See Attachment 1 for a depiction of the ultrasonic examination coverage.
E-3
ENCLOSURE WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME)
REQUEST FOR RELIEF 1-ISI-14 AND 1-ISI-15 REQUEST FOR ADDITIONAL INFORMATION NRC QUESTIONS ON RELIEF REQUEST 1-1S1-15 QUESTION 4 On page E2-1, TVA identified the 6-inch and 8-inch safety injection system piping welds as the components for Relief Request 1-ISI-15. On Page E2-3, the components were identified as SIF-D086-02 and RHRF-D054-09.
(a) Confirm that RHRF-D054-09 weld is associated with the 8-inch pipe, and Response 4(a)
RHRF-D054-09 weld is associated with the 8-inch pipe.
(b) Clarify whether SIF-D086-02 weld is associated with the 6-inch pipe or 3-inch pipe because in Attachment 4 to Enclosure 2, pages 1 and 5, it is shown that the subject pipe is 3 inches, not 6 inches, in diameter.
Response 4(b)
SIF-D086-02 is associated with the 3-inch pipe. The "6-inch" reference on Page E2-1 is in error.
QUESTION 5 On page E2-2,Section V, TVA stated that the examination area is limited to one side of the subject welds. On page E2-3, TVA stated that the best effort coverage in the volumetric examination is 50 percent of the subject welds.
(a) Confirm that the volumetric examination can only be performed from the pipe side, not the valve side.
Response 5(a)
Due to the tapered surface and physical restriction on the valve side of the weld, a meaningful ultrasonic examination is not feasible from the valve surface. Additionally, TVA E-4
ENCLOSURE WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME)
REQUEST FOR RELIEF 1-ISI-14 AND 1-ISI-15 REQUEST FOR ADDITIONAL INFORMATION is not aware of any industry qualified ultrasonic techniques for examination from the valve side, however efforts (higher beam angles) were made to maximize examination coverage while scanning from the pipe side of the weld.
(b) Discuss which volume or areas of the subject welds will not be covered in the examination; Response 5(b)
The examination volume was ultrasonically interrogated to the extent possible while scanning on the pipe side of the weld. See Attachment 2 and Attachment 3 for a depiction of the ultrasonic examination coverage of the subject welds.
See Attachment 4 for the TVA procedure used to calculate the volumes covered.
(c) Discuss whether the entire inside pipe surface area of the welds will be covered in the proposed examination; Response 5(c)
The examination volume was ultrasonically interrogated to the extent possible while scanning on the pipe side of the weld. See Attachment 2 and Attachment 3 for a depiction of the ultrasonic examination coverage of the subject welds.
(d) For the volume or areas that will not be covered by the examination, discuss how the structural integrity of those volumes or areas of the welds be assured.
Response 5(d) 10 CFR 50.55a(xv)(A)(2) requires that if access is available, the weld shall be scanned in each of the four directions (parallel and perpendicular to the weld) where required. Coverage credit may be taken for single side exams on ferritic piping. However, for austenitic piping, an examination procedure must be qualified with flaws on the inaccessible side of the weld. There are currently no qualified single side examination procedures that demonstrate equivalency to two-sided examination procedures on austenitic piping welds. Current technology is not capable of reliably detecting or sizing flaws on the far E-5
ENCLOSURE WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME)
REQUEST FOR RELIEF 1-ISI-14 AND 1-ISI-15 REQUEST FOR ADDITIONAL INFORMATION side of an austenitic weld for configurations common to nuclear applications. The Performance Demonstration Initiative (PDI) Program conforms with 10 CFR 50.55a(xv) regarding single side access for piping. PDI Performance Demonstration Qualification Summary (PDQS) certificates for austenitic piping list the limitation that single side examination is performed on a best effort basis. The best effort qualification is provided in place of a complete single side qualification to demonstrate that the examiners qualification and the subsequent weld examination is based on application of the best available technology. The best available techniques as qualified through the PDI for Supplement 2 to ASME Section XI, Appendix VIII, "Performance Demonstration for Ultrasonic Examination Systems," with demonstrated best effort for single side examination, was used from the accessible side of the weld as previously described. The maximum extent practical ultrasonic examination of the subject welds provides reasonable assurance of an acceptable level of quality and safety.
Significant degradation, if present, would have been detected during the best effort ultrasonic examination that was performed on the subject welds. In addition, as a result of the best effort ultrasonic examination and the VT-2 system pressure test, reasonable assurance of operational readiness has been provided.
QUESTION 6 Identify the material of the SIF-D086-02 and RHRF-D054-09 welds and the associated pipe and valve.
Response
Materials for weld SIF-D086-02:
Pipe: SA-376 TP 304 Valve: SA-182 F316 Weld: ER-308 Materials for weld RHRF-D054-09:
Pipe: SA 376 TP 304 Valve: SA-182 F316 Weld: ER-308 & E-308 E-6
ENCLOSURE WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME)
REQUEST FOR RELIEF 1-ISI-14 AND 1-ISI-15 REQUEST FOR ADDITIONAL INFORMATION ATTACHMENT 1 EA1-1
ENCLOSURE WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME)
REQUEST FOR RELIEF 1-ISI-14 AND 1-ISI-15 REQUEST FOR ADDITIONAL INFORMATION ATTACHMENT 1 Nozzle
_ mExam Volume pressurizer Top Head Ckd Ultrasonic beams (45 & 60) directed parallel to weld fxamlnatlon Imitatlon Illustrated hi croSs hatch area Typha b "h.1.. P1.qor IdP.1 1a 1X 14int;s EA1-2
ENCLOSURE WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME)
REQUEST FOR RELIEF 1-ISI-14 AND 1-ISI-15 REQUEST FOR ADDITIONAL INFORMATION ATTACHMENT 2 Ultrasonic beams (45 & 70-) directed perpendicular to weld, scanning on pipe side Examination limitatlon Illustrated In cross hatch area E% Exam Volume )
Weld SIF-D086-02 Valve Pipe Ultrasonic beam (451) directed parallel to weld Examination llmitatlon Illustrated In cross hatch area EA2-1
ENCLOSURE WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME)
REQUEST FOR RELIEF 1-ISI-14 AND 1-ISI-15 REQUEST FOR ADDITIONAL INFORMATION ATTACHMENT 3 LUlbd "-(*' JW) dkoldpmm.1 v o-W~ung ,epip Emb-cnfl on0 lod-fefd In w_ befh ae Uftm& beems (4V & 1 dk.hdpwdeld bedi Exvendn 5"Ati loa.d In w- 1ak ar EA3-1
ENCLOSURE ATTACHMENT 4 WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME)
REQUEST FOR RELIEF 1-ISI-14 AND 1-ISI-15 REQUEST FOR ADDITIONAL INFORMATION PROCEDURE N-GP-28 CALCULATION OF ASME CODE COVERAGE FOR SECTION XI NDE EXAMINATIONS
NONDESTRUCTIVE EXAMINATION PROCEDURE Procedure No. N-GP-28 TVA Nuclear Power Revision 4 Page 1 of 8 W47 031219 000 QA RECORD CALCULATION OF ASME CODE COVERAGE FOR SECTION Xl NDE EXAMINATIONS "QUALITY RELATED Prepared By: Robert E. Hardawav Date: 12118/03 Technical Review: Joel W. Whitaker NDE Level IlIl, Date: 12/18103 ISO Approval: W. Ed Freeman PDate: 12/18/03
NONDESTRUCTIVE EXAMINATION PROCEDURE Procedure No. N-GP-28 TVA Nuclear Power Revision 4 Page 2 of 8 Rev. No. Date Description 0 4/3196 Initial issue.
1 8/15/97 Incorporate TC 97-09.
2 10/18/00 General revision to incorporate 10CFR50.55a ruling change which implements Appendix Vill 3 5/24/01 Revised to upgrade procedure to ASME Section Xi 1995 Edition with Addenda through 1996 4 12/18/03 Revised to incorporate corrective actions from PER 03-014859-000.
NONDESTRUCTIVE EXAMINATION PROCEDURE Procedure No. N-GP-28 TVA Nuclear Power Revision 4 Page 3 of 8 1.0 Scone The scope of this procedure is to provide generic guidelines for calculating the ASME Section Xl code coverage and augmented examination coverage obtained during volumetric and surface examinations. This procedure incorporates the requirements of Code Case N-460 and NRC Information Notice 98-42. This procedure is not applicable for calculating the examination coverage for RPV examinations performed in accordance with Appendix Vil.
2.0 Purpose This procedure applies to the calculation of ASME Section XI Code coverage for vessel welds (excluding the RPV welds performed in accordance with Appendix VilI) piping welds, and integral attachments. This procedure applies when performing surface, volumetric or visual examinations and may be used as a guide when calculating the examination coverage for preservice and inservice examinations. Coverage limitations may be due to an obstruction, interference, geometric configuration or other applicable reason.
3.0 References 3.1 ASME Code Case N-460 3.2 10CFR 50.55a, as amended by the Federal Register Notice, Vol. 64, No. 183, dated September 22,1999 (Final Rule)- Implementation of Appendix Vil as executed by the Performance Demonstration Initiative (PDI) Program Description Document, Rev. 1, Change 1.
3.3 Guideline for the Implementation of Appendix VIil and 10CFR 50.55a, Rev. D, April 18, 2000 3.4 NRC Information Notice 98-42 3.5 SON PER 03-014859-000 l 4.0 Definitions 4.1 Examination Coverage- The percentage of the examination surface or volume obtained during the performance of the examination.
4.2 Examination Surface- The surface of the weld and base material required to be examined by ASME Section Xl or other requirement using a surface and/or visual examination method as applicable.
4.3 Examination Volume- The volume of weld and base material required to be examined by ASME Section Xl or other requirement using a volumetric examination method.
4.4 Scan Limitation- the inability to scan the surface(s) as required by procedure due to interferences.
4.5 Surface Limitation- the inability to perform a surface examination of the required surface(s) because of an interference.
NONDESTRUCTIVE EXAMINATION PROCEDURE Procedure No. N-GP-28 TVA Nuclear Power Revision 4 Page 4 of 8 4.6 Volumetric Limitation- the inability to examine the required volume because of the geometric configuration, a physical interference, or a metallurgical condition of the material being examined.
5.0 General 5.1 During the performance of inservice inspections, ASME Section Xl requires examination coverage to be essentially 100%/6 of the weld area or volume. For examination coverage less than 100%, TVA has implemented ASME Code Case N-460 which states that when the entire examination volume or area cannot be examined due to interference by another component or part geometry, a reduction in examination coverage for Class 1 or Class 2 welds may be accepted provided the reduction in coverage for that weld is less than 10%. (NRC Information Notice 98-42 further defines the >90% rule to include all welds and other areas required by ASME Section Xl.
5.2 Surface and/or visual examinations are typically conducted on the weld area plus a defined amount of base material on each side of the weld. Volumetric examinations specify a particular volume to be examined. The Section Xl required examination volume or surface examination area for each type of weld is depicted in figures of IWB-2500, IWC-2500 and IWD-2500 as applicable. As depicted for piping welds, volume width generally constitutes the weld plus 1/4t on each side while volume thickness generally constitutes the lower 1/3 of the piping thickness for the length of the weld. The exception normally includes code category B-O which includes the weld plus 1/2 inch and full volume for the length of the weld. As depicted, for vessel welds, the volume width generally constitutes the weld plus 11/2t on each side of the weld while volume thickness generally constitutes the entire component thickness (i.e. full volume). The volume changes with variations in weld configuration (e.g. transition between different pipe thickness or vessel weld configurations).
Note: Risk-Informed (RI) programs require larger volumes in certain areas.
5.3 The required examination volume or area shall be verified prior to calculation of the limitation.
6.0 Documenting and Calculating Examination Coveraae 6.1 While performing a visual, surface or ultrasonic examination, the NDE Examiner shall make every attempt to examine 100 percent of the examination area or volume.
6.2 When practical, the two beam path directions for ultrasonic examinations should be performed from two sides of the weld or additional angles employed In order to maximize coverage.
6.3 If 100% percent of the examination surface or volume cannot be examined, the NDE Examiner should perform the following under the direction of the inspection coordinator or the NDE Level IlIl:
6.3.1 Perform additional examinations with higher angles in order to maximize cover for ultrasonic exams.
NONDESTRUCTIVE EXAMINATION PROCEDURE Procedure No. N-GP-28 TVA Nuclear Power Revision 4 Page 5 of 8 6.3.2 Perform another surface method (i.e., PT in lieu of MT) in order to maximize coverage.
6.3.3 Perform alternative NDE methods if applicable.
6.4 The examiner shall accurately document all limitations, obstructions, interferences, geometric configurations or other applicable reasons for not obtaining the required code coverage. This information shall be validated and verified by the assisting examiner or independent verifier and documented in the NDE data report.
6.5 The examiner shall document the limitation on a sketch. Examination coverage estimates may be performed by the examiner or the reviewer.
7.0 Calculation Basis 7.1 Volumetric Examinations- Piping Welds and Vessels 2 inches and less in thickness a) Examination volume coverage may be increased as previously discussed or by use of refracted longitudinal wave techniques on stainless steel or dissimilar metal welds. Use of refracted longitudinal waves to penetrate stainless steel weld material will increase the examination volume coverage by the amount depicted on the examination coverage drawing.
b) Estimates shall be derived by estimating coverage based on two-beam path direction coverage of the complete examination. Each scan direction equals 25% (downstream, up-steam, clockwise, counterclockwise.)
(Reference Figure 1) c) The effects of adjacent component interferences (e.g. welded lug attachments) along the weld length are also taken into account with the reduction in coverage identified as a percentage of reduced volume.
8.0 Visual and Surface Examinations - Pipinq Welds And Integral Attachments 8.1 Examination area coverage calculations are based upon one of the following suppositions:
a) The total examination area is calculated, typically length x width, then the total area of limitation or interference is subtracted from the total examination area.
b) The area of achieved coverage is divided by the total examination area for percentage of examination achieved.
NONDESTRUCTIVE EXAMINATION PROCEDURE Procedure No. N-GP-28 TVA Nuclear Power Revision 4 Page 6 of 8 9.0 Ultrasonic Examinations - Vessel Welds NOTE: THIS IS NOT APPLICABLE FOR APPENDIX Vil EXAMINATIONS OF THE RPV WELDS.
9.1 Examination volume coverage calculations are based upon the following 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:
- 1) 0 degree (weld metal scan)
- 2) 45 degree Transverse-scan from vessel side of the weld
- 3) 45 degree Transverse-scan from nozzle side of the weld
- 4) 60 degree Transverse-scan from vessel side of the weld
- 5) 60 degree Transverse-scan from nozzle side of the weld
- 6) 45 degree Parallel-scan CW direction
- 7) 45 degree Parallel-scan CCW direction
- 8) 60 degree Parallel-scan CW direction
- 9) 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 Xi Code.
a) The total examination coverage may be calculated by averaging the exam volume coverage for all nine scans.
10.0 PDI Implementation for Piping Welds 10.1 Where examination from both sides is not possible, full coverage credit may be claimed from a single side for ferritic welds provided the examiner is qualified for single sided examination. Current technology is not capable of reliably detecting or sizing flaws on the far side of an austenitic weld for configurations common to US nuclear applications. Therefore, examination of austenitic material welds shall be performed from both sides or a scan limitation shall be documented.
10.2 The NDE Level IlIl shall make an evaluation In the Weld Resolution document regarding total examination coverage (best effort) as calculated above in Section 7.0. In addition, a coverage evaluation which considers the PDI Implementation Guideline shall also be indicated in the Weld Resolution sheet. These two coverage evaluations shall be reported to the ISI Programs Engineer for incorporation into the Relief Request.
10.3 Typically a one-sided austenitic weld examination with no circumferential restrictions would be indicated as 75% examination coverage or 50% if circumferential scans were limited to one side.
NONDESTRUCTIVE EXAMINATION PROCEDURE Procedure No. N-GP-28 TVA Nuclear Power Revision 4 Page 7 of 8 NOTE: These requirements do not apply to augmented examinations of piping welds.
11.0 Responsibilities 11.1 The examiner, assisting examiner or designee shall document the amount of code coverage obtained after all necessary steps to perform additional examinations has been completed Inorder to maximize coverage. The documentation including verification of limitations shall become part of the examination weld data package.
11.2 The documentation may be reviewed by another individual with the same or higher NDE certification.
11.3 The NDE Level IlIl or data reviewer may review the calculations in order to verify that the information is accurate and correct.
11.4 The NDE Level IlIl may recalculate the examination coverage to obtain a more accurate value of the examination surface or volume examined. The calculation shall be documented on the exam report.
11.5 The NDE Level IlIl may require an alternate examination technique or method, or request that the interference be removed. For nozzle examinations, supplemental scans from the nozzle bore or flange face may provide complete coverage of the weld.
11.6 If the examination coverage indicates less than 90 percent of the required examination volume or surface, the site ISI Program Engineer shall be notified.
11.7 The site ISI supervisor shall ensure that examination results are accurately documented and incorporate results into a Request for Relief if necessary.
. I pt NONDESTRUCTIVE EXAMINATION PROCEDURE Procedure No. N-GP-28 TVA Nuclear Power Revision 4 Page 8 of 8 mI3230 APPENDIX D - MANDATORY m-331o Interference between shoo I
IL I Exam vot.
k C-D-E-F GENERAL NOTE:
Forthis example of Interference with a 'AV examination applied from both sides. only the E-F G-41 portion of the examination volume receives two direction coverage. while volumes C-G-f and t-D0E receive one direction coverage. In this case, ihe examination beam path shall be Increased to
%V I0D. to t. and back towards 0.0. for %t) to provide the required two Crection coverage over the examination volume. Use of a %V examination beam path (0.D. to LD. to 'At) provides additional beam path (past %tl to help in obtaining required coverage when examination part thickness t incaases.
FIG. 111-3230-1 EXAMPLE OF PHYSICAL RESTRICTONS TO THE WELD EXAMINATION Figure 1