ML13102A298
| ML13102A298 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 04/05/2013 |
| From: | Grecheck E Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML13102A298 (22) | |
Text
10 CFR 50.55a VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 April 5, 2013 United States Nuclear Regulatory Commission Serial No.13-141 Attention: Document Control Desk NAPS/JHL RO Washington, D.C. 20555 Docket No. 50-338 License No. NPF-4 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)
NORTH ANNA POWER STATION UNIT 1 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION ASME SECTION Xl INSERVICE INSPECTION PROGRAM RELIEF REQUEST NI-14-LMT-001 - FOURTH INTERVAL PERIOD 1 LIMITED EXAMINATIONS By letter dated November 1, 2012 (Serial No.12-660), Virginia Electric and Power Company (Dominion) submitted a relief request for limited examination coverage (i.e.,
less than 90% weld coverage achieved, due to physical interferences that prohibited attaining full weld coverage) obtained during the inservice inspection (ISI) examinations at North Anna Power Station Unit 1 during the fourth ten-year ISI interval. These examinations were performed to meet the requirements of the 2004 Edition of ASME Section XI with No Addenda and the Risk-Informed/Safety-Based Inservice Inspection (RIS B) Program Plan based on Code Case N-716. In an E-mail from Dr. V. Sreenivas, dated March 4, 2013, the NRC requested additional information to complete the review of the limited examination relief request. Submittal of the additional information was requested by April 5, 2013. The responses to the request for additional information are provided in the attachment to this letter.
If you have any questions or require additional information regarding the information provided in the attachment, please contact Mr. Thomas Shaub at (804) 273-2763.
Very truly yours, E. S. Grecheck Vice President - Nuclear Engineering and Development
Attachment:
Response to Request for Additional Information - ASME Section Xl Inspection Program Relief Request Nl-14-LMT-001 Fourth Interval Period Limited Examinations Commitments made in this letter: None Ao-y
Serial No.13-141 Docket No. 50-338 Response to Request for Additional Information Fourth Interval Period 1 ISI Limited Exam Relief Request Page 2 of 2 cc: U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia 30303 Mr. J. E. Reasor, Jr.
Old Dominion Electric Cooperative Innsbrook Corporate Center 4201 Dominion Blvd.
Suite 300 Glen Allen, Virginia 23060 NRC Senior Resident Inspector North Anna Power Station Ms. K. R. Cotton NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 0-8 G9A 11555 Rockville Pike Rockville, Maryland 20852 Dr. V. Sreenivas NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 0-8 G9A 11555 Rockville Pike Rockville, Maryland 20852
Serial No.13-141 Docket No. 50-338 Attachment Response to Request for Additional Information ASME Section XI Inservice Inspection Program Relief Request NI-14-LMT-001 - Fourth Interval Period I Limited Examinations North Anna Power Station Unit I Virginia Electric and Power Company (Dominion)
Serial No.13-141 Docket No. 50-338 Page 1 of 19 REQUEST FOR ADDITIONAL INFORMATION (RAI)
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNIT I BACKGROUND By letter dated November 1, 2012 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML12319A278), Virginia Electric and Power Company (Dominion) submitted Relief Request (RR) NI-14-LMT-001 for U.S. Nuclear Regulatory Commission (NRC) review and approval. Dominion requested relief from certain requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code), Section Xl, specifically related to examination coverage.
RR Nl-14-LMT-001 is applicable to the fourth 10-year inservice inspection (ISI) interval for the North Anna Power Station (NAPS) Unit 1, which commenced on May 1, 2009 and will end on April 30, 2019. On March 4, 2013, the NRC sent Dominion a request for additional information (RAIs) concerning this relief request. The response to the RAIs was requested by April 5, 2013. The RAIs and the associated Dominion responses are provided below.
NRC INFORMATION REQUEST NRC Question 1 The weld schematics (scan plots) in RR NI-14-LMT-001, Enclosure A1-1, pages 13 and 20 of 105, show that the volume covered by the (UT) examinations performed from the vessel side, (or the refracted 45 and 60-degree shear waves traveling through the weld material), were terminated at the boundary between the weld material and the base material's heat affected zone (HAZ). Discuss reason, basis, or implication of this volume coverage.
Dominion Response For both pages 13 and 20 of 105, the termination at the weld boundary is to determine coverage for weld metal only, as identified on pages 15 and 22, respectively. Base metal coverage is also identified on pages 15 and 22, and the plots for base metal coverage are shown on pages 12 and 19. The limitation is due to nozzle radius interference.
When reviewing the data sheets to answer this question, it was determined that while the coverage is correctly calculated, the plots were labeled incorrectly and the corresponding percentages were reversed. The data sheets were corrected, reviewed, and verified by the ANII. The corrected data sheet pages are attached.
Serial No.13-141 Docket No. 50-338 Page 2 of 19 Serial No.12-660 Docket No. 50-338 NAPS Unit 1 4 1h Interval 11SPeriod Limited Exams ENCLOSURE Al-1 I Page 13 of 105 mobý,
Supplemental Report Rcport No.: UT-I 2-054 70-00"w-Page: 5 of T Summary No.: N1.l3.110.001 Examiner: Stevermer, Aaron.) Level: II-PIDI Revimerw. +/-i..- ... Date;: '-S.2cc Examiner. NIA Level: MIA Site Reviea.w*-- a( Cja Date: z Other MIA Level:" NIA ANIi Review. Date: ____
Comment:
SRetch or Photo:
3pm 1 EXAMINED 1.28 SQ. IN. OF THE 4.0 SQ. IN REQOURED WELD METAL VOLUMEMLE*'LGPEM E NOZ SIDE 1.2814 =.32X 100=32%
EXAMINED 1.84 SQ. IN. OF THE 4.0 SQ. IN. REQUIRED WELD METAL VOLUMEJ.L*EIGIME NOZ SIDE 1.8414 =.40 X 100 =40%
List/.'.:? '.
Addtional - Supplemental Data
Serial No.13-141 Docket No. 50-338 Page 3 of 19 Serial No.12-660 Docket No. 50-338 NAPS Unit 1 0 Interval 16' Period Limited Exams ENCLOSURE A1-1 Page 15 of 105 Report No: UT-17-054 Summary # N1.13.110.001 WO oflnlinif Pg. 7 of 7 Prepared b:W. Thomas Date: 4/31201Z Weld Number 10 Thickness 3.111 Weld Length 50" 2"
Weld Width ANGLE SCAN AREA SCAN 5IJR. DIRECI1OIN COVERAGE 0 BASE AND WELD METAL HEADAWD NIA 81.2%
45j 60 BASE METAL HFADWLD ýCIRC 74.9%
- 45. 60 BASE METAL .HEA/WELD AX 87.3%
45 WELD METAL HEAL/WEiD Ax i1 40A8-' WELD METAL NOVWELD AX 32%
45 WELD METAL. WELD CIRC 100%
60 WELD METAL HEAD/WELD AX 110%9
'1X WELD METAL MOZ/WELD I AX 46%
60WELD METAL WELD CRC. 100%
TOTAL .721.4 /.9 = 80%
DUE TO NOZZLE CONFIGURATION, 100% OF THE REQUIRED EXAMINATION VOLUME WAS NOT ACHIEVED. AN vw_._
Ini"il C FiMnl IE 4813-CT EAdIIIUIOLflJ*S ~'~J'.'~'*......~~0*~* Length 45= Width 5.1" r~llll~l~l/l V~gIII*IICI*U* *l*lCoverage' .Su mma ry "" .
Required Scans (each has a weighing fiacto'r:0f 100lfor Comple-te coveraged ANGLE UpStA-Circ DnSt-Ax DnSt-Circ
- SEE ABOVF Code Coverage Total
- Best Effort Coverage (Max 25%) Total N/A Note$:
- 1) Code.Coverage refers to the maximum percentage of the required examination volume thatis effecively examined with the qualified examination procedure-
- 2) Best Effort Coverane refers to the required examination volume pat the weld centerline that Is examined in the axial beam direction with an Appendix VIII demonstrated procedure for single sided coverage.
Serial No.13-141 Docket No. 50-338 Page 4 of 19 Serial No.12-660 Docket No. 50-338 NAPS Unit 1 4 th Interval 1s' Period Limited Exams ENCLOSURE A1-2 Page 20 of 105 Supplemental Report Ropott No,: UT-12-DIS Page. 5 of 7 Summary No.: Ni.B131110'06 Examiner: Stevermer. Aaron J. Level: II-PDI Reviewer S.1W,.." ,- .
Date:..ag Examiner; NIA Level: WA Site Review: T . , a Other; NIA Level: NWA ANII Review.
Comments; Sketchor Photo:
II EXAMINED 1.288SQ. IN..OF THE 410 SQ: IN REQUIRED WELD METAL VOLUMEoS DEGREE NOZ SIDE 12814 =.32X 100=32%
EXAMINED 1.54 SO. IN. OF THE 4.0 SQ. IN. REQUIRED WELD METAL VOLUMEJ7 DEGREE NDZ SIDE 1,8414.=.46 X 100 -46%
i > /
Mddltonal- Supplemental Data
Serial No.13-141 Docket No. 50-338 Page 5 of 19 Serial No.12-660 Docket No. 50-338 NAPS Unit 1 4 th Interval 1`1 Period Limited Exams ENCLOSURE A1-2 Page 22 of 105 Report No: UT-12-053 iWDominion Summary 4 N1.B3.110.01 PC. 7 of 7 Prepared by: W. Thomas -
Date: 4/3/2012 Weld Number 14 AN .DW Thickness 3.10" Weld Length So" HO! 0?
Weld Width ANGLE SCANAREA sCAN SUA. DiRECFION COVERAGE 0 BASEANOWELDMETAL HEAD/WELD NIA 91.25 4S,.60 BASE METAL HEAD/WELD. CmRC 74.9%
45,60 BASE METAL HEAD/WELD AX 87.3%
45 WELD METAL. HEAD/WELD AX 100%
_ _ WELD METAL OkVWEL.) AX 32%
45 WELD METAL WELD 100%
11- 60 WELD METAL HWELD
_ __c AX 100%
____ WELD METAL woz(WELD Ax 46%
TOTAL 721-4 / 9 -80%
DUE TO NOZZLE CONFIGURATION, 100% OF THE REQUIRED EXAMINATION VOLUME WAS NOT ACHIEVED.
cX~iTItI1dLIUI I V~JI UHFI~ ~'H*HS~**~.. - .3_i.. Length 45" Width .5.1" Coverage Surmmary Required: Scans (each has a weighing factor of 100 for complete coveragei ,,
ANGLE UpSt-Ax UpSt-Crc DnSt-Ax DnSt-Circ
- SEE A*OVE Code Coverage Total Best Effort Coverage (Max 25%) Total N/A Notes:
- 1) Code Coverage refers to the maximum percentage of the required examination volume that is effectively examined with the qualified examination procedure.
Z) Best Effort coverage refers to the required examination volume past the Weld centerline that is examined in the axial beam direction with an Appendix VIII demonstrated procedure for single stded coverage.
Serial No.13-141 Docket No. 50-338 Page 6 of 19 NRC Question 2 Section 4 of WCAP-14572, Rev. 1-NP-A, states in part, "When an examination location is selected that does not meet > 90% examination coverage, a strategy should be applied with regard to examination coverage as follows:
- 4. If the area or volume of concem still remains insufficiently addressed, consideration should be given to leakage monitoring options such as more frequent pressure testing and VT-2 examinations or operatorwalkdowns."
For each weld for which relief is requested (i.e., the required coverage is not achieved),
discuss whether any supplemental examinations or compensatory measures, as specified above, have been taken to provide additional assurance of pressure boundary leak tightness.
Dominion Response WCAP-14572, Rev. 1-NP-A was not used as the basis for the North Anna Unit 1 Fourth Interval Risk-Informed ISI Program. The NAPS 1 Risk-Informed ISI Program is based on ASME Code Case N-716, commonly referred to as an RISB Program. The Unit 1 Risk-Informed ISI Program was submitted as Relief Request N1-14-RI-001 in a Dominion letter dated February 23, 2010 (Serial No.10-050), and approved by NRC letter dated January 21, 2011 (TAC No. ME3449).
Section 3.3.2 of approved Relief Request Nl-14-RI-001 states:
3.3.2 Program Relief Requests An attempt has been made to select RISB locations for examination such that a minimum of >90% coverage (i.e., Code Case N-460 criteria) is attainable.
However, some limitations will not be known until the examination is performed since some locations may be examined for the first time by the specified techniques. In instances where locations at the time of the examination fail to meet the >90% coverage requirement, the relief process outlined in 10 CFR 50.55a will be followed.
Per footnote 3 of Table 1 of Code Case N-716, when the required examination volume or area cannot be examined due to interference by another component or part geometry, limited examinations shall be evaluated for acceptability.
Acceptance of limited examinations or volumes shall not invalidate the results of the change-in-risk evaluation (paragraph 5 of Code Case N-716). The change in risk evaluation of Code Case N-716 is consistent with previous RI-ISI applications and meets RG 1.174 change in risk acceptance criteria. Areas with acceptable limited examinations, and their bases, shall be documented.
Serial No.13-141 Docket No. 50-338 Page 7 of 19 Consistent with previously approved RI-ISI submittals, NAPS will calculate coverage and use additional examinations or techniques in the same manner it has for traditional Section Xl examinations. Experience has shown this process to be weld-specific (e.g., joint configuration). As such, the effect on risk, if any, will not be known until that time. Relief requests will be submitted per the requirements of 10 CFR 50.55a(g)(5)(iv) within one (1) year after the end of the interval.
Element selection for the NAPS RI-ISI Program is in accordance with Code Case N-716 and the approved Relief Request N1-14-RI-001. While the element selection criteria in Relief Request N1-14-RI-001, Section 3.3, allows random selections within the provided guidelines based on degradation mechanism, system, and other location criteria, Dominion also considered previous examination history. Each of the risk-informed welds included in this relief request have an examination history, whether under the ISI Program, the previous Risk-Informed Program, or previous Augmented Inspection Program. Continuing to perform "successive examinations" is reasonable for the purpose of identifying service-induced flaws and degradation.
Each of the welds included in this relief request, other than the three Main Steam System welds (87% coverage); are Class 1 welds located inside the reactor containment; are included within the Class 1 pressure boundary; receive visual examinations at the beginning of each refueling outage as part of our Boric Acid Corrosion Control Program; and receive VT-2 visual examinations at the end of the refueling outage once operating pressure and temperature is achieved before unit start-up. The three Main Steam System welds with reduced coverage also receive complete surface examinations (magnetic particle) as they are included in the augmented program for Main Steam System Postulated Break Locations. The associated Main Steam lines are regularly walked down during normal operator rounds.
For the welds in this relief request where Dominion performs single-sided examinations, with Code coverage limited to only 50%, additional non-Code coverage was obtained (Best Effort Coverage) on the critical inside surface volume of both the weld and heat-affected area. These are additional measures that provide reasonable assurance that these welds are structurally sound. If the completed examination failed to provide that reasonable assurance, then the evaluation of these limited examinations following each refueling outage, as well as the RI-ISI period updates, could establish additional locations for examination or other additional measures. The North Anna Unit 1 Risk-Informed Inservice Inspection Program Period Update completed November 9, 2012 made several weld selection changes with the intention of achieving greater inspection coverage. However, the examination coverage of the welds included in this relief request has been evaluated to require no further actions in order to provide reasonable assurance of pressure boundary leak tightness.
Serial No.13-141 Docket No. 50-338 Page 8 of 19 NRC Question 3 Provide ASME Code class type (e.g., Class 1, 2, or 3 piping) for risk informed welds for which relief is requested. Provide piping system (e.g., reactor coolant system) for each weld for which relief is requested.
Dominion Response Weld Code Line # Class System 1515 1 RC - Reactor Coolant System 6"-RC-16 20 20 1 RC - Reactor Coolant System 6"-RC-17 SW-4 2711R1 1 RC - Reactor Coolant System 27 1/2"-RC-3 151 1 RC - Reactor Coolant System 6"-RC-21 19 19 1 SI - Safety Injection System 6"-S1-131 88 1 SI - Safety Injection System 12"-SI-67 11 1 RC - Reactor Coolant System 8"-RC-1 1 4R 1 RC - Reactor Coolant System 8"-RC-1 1 11 1 CH - Chemical and Volume Control System 4"-CH-A1 4 SW-10 Non-Safety SHP - Main Steam 32"-SHP-57 Related SW-12 Non-Safety SHP - Main Steam 32"-SHP-58 Related SW-1l Non-Safety SHP - Main Steam 32"-SHP-59 Related 35 3R 1 RC - Reactor Coolant System 4"-RC-1 5 11
Serial No.13-141 Docket No. 50-338 Page 9 of 19 NRC Question 4 RR NI-14-LMT-001, Enclosure R1-1 through R3-7, pages 30, 35, 40, 45, 54, 61, 70, 75, 80, 84, 90, 97, 103 of 105 documented the examination volume.
- a. Clarify whether the correct width dimension for the welds was used in the calculation of volume. As an example, Enclosure R1-2, page 35 of 105, top right of page, documented, "Weld Width 1.1 [inches]," for Weld No. 20 (Line No. (6"-RC-17) while middle right of the same page documented "Width 1.1 [inches] for the "Examination Volume Dimensions." For this example, clarify why the examination volume does not include the required expanded volume (e.g., heat affected zone of base materials or the risk-informed expanded volume).
- b. Clarify why the thickness dimension for the welds documented in "UT Calibration/Examination" sheets is different than the thickness documented in the weld schematics (scan plots) for the same weld. As an example, Enclosure RI-1, page 26 of 105, documented, "Thickness/Diameter: 0. 719"/6.0 [inches]," for Weld No. 15 (Line No. 6"-RC-16), while page 30 of 105 documented "Weld Thickness:
0.771 [inch]," for the same weld. Clarify whether the correct thickness, or height dimension, for the welds was used in the calculation of volume.
Dominion Response
- a. On several of the identified pages, it was found that some of the Examination Volume Dimensions were recorded on the data sheets incorrectly. When re-verifying the examination coverage calculations, it was identified that in each case the correct values were used to determine coverage.
For example, page 35 of 105 indicated that the weld width is the same as the examination volume width, and this is incorrect. This is proved by multiplying the volume height, 0.273", by 1.05" (half the volume width of 2.1") which equals 0.29 square inches (0.28665") as indicated in the middle of page 35 of 105 (weld width 1.1" and volume width 2.1").
When re-verifying the examination coverage calculations it was also discovered that incorrect examination volume width was recorded on other data sheet pages as well (pages 75, 80, 84, and 90 of 105). Dominion has corrected these pages and verified that the correct values were used in calculating coverage. The examination procedure states that the expanded volume for risk-informed examinations without counterbore is 1/2" from the weld toes, which was followed for these examinations.
The corrected and ANII reviewed data sheet pages are attached.
The re-verification also found that the length dimension recorded on page 40 of 105 was actually the pipe diameter. The coverage calculations are correct, but the recorded dimensions required correction and are attached.
Serial No.13-141 Docket No. 50-338 Page 10 of 19
- b. The thickness dimension identified in the "UT Calibrations/Examination" sheets for any particular line number is the nominal thickness dimension from the piping specification for the pipe schedule and diameter. The examiner gets the dimension from the scan plan cover sheet in the package before performing the examination.
The pages where the examination volume is recorded (i.e., pages 30, 35, 40, etc.
mentioned above) document the actual volume thickness as determined from the UT readings.
For example, the thickness dimension on page 26 of 105 is the nominal thickness dimension for the particular line number, pipe schedule, and pipe diameter. On page 30 of 105, the actual weld thickness used for coverage calculations is the measured thickness from UT readings. The measured thickness is used in order to gain more accurate coverage calculations since fittings are usually thicker than the nominal dimensions. Using the actual measured thickness values to calculate volume coverage is in accordance with the procedure requirements for risk-informed without counterbore examinations.
Serial No.13-141 Docket No. 50-338 Page 11 of 19 Serial No.12-660 Docket No. 50-338 NAPS Unit 1 4'6 Interval 1s' Period Limited Exams ENCLOSURE R1-2 Page 35 of 105 Report No: UT-1 0-224 Summary # N1.R1. 1.008 Pg. 5 of 5 SDuminion- Prepared By: W.L. Thomas 0 -
Date: 09/29/2010 Wi IeldNumber 20 Weld Width 1.1" w 'ed Thickness Wa 0,880" tld Length 20.8" 3 2 1 0 1 2 CL VALVE
.al*O T"OAL FEQuIE: CEXAMVUAMEODS= Q12DSC INWI-EXAMINED 103% RUQUREfl.VULLAE OS SI rM.
1tOtAL FQURB3 EXAM 2OLLME US = 029S. IND-M NOEXAM FCRO.21 M. INCES CSIDLE AXIAL FECITICfN NP19'",
., EXAVfgOg* 8Q I1'i3EC1 E8T.vrao ISO I,
--Pxamhatiow-volume flimensrons-
- CB.2=
....en on-amLti!X egh--27 li2---r-1ei tn ORrL SS- EA0 ALSfE-cN-h--2a--w ---
a-'
~14t5T~3O
--A.' -~ -
,-:.,-. I',
'~
Coverage Summar Required Scans (each has a weighing factor of 100 for complete coverage)
ANGEI UpSt-Ax UpSt-Circ DnSt-Ax DnSt-Girc.
45/60 0%,- 100% 100%
60 L *28% "
Code Coverage Total 500/
100+100+28+0=228400=57 ' Bestifort Coverage (Max 25 %) Total 7 Notes: 1,) Code Coverage refers to fte maximum percentage of the required examination volume timat is eftectively exarirlheo with Mle qualified examination procdure,
- 2) Best Effort Coverage refers to the required examination volume past the weld centerilne that is examined in the axial beam dlirection with an* AppendixVlfl demonstrated procedure forsingle side .dcoverage.
ANNtSteb4Ž~
IntiaI 03 Pinat 0--
Serial No.13-141 Docket No. 50-338 Page 12 of 19 Serial No.12-660 Docket No. 50-338 NAPS Unit 1 40 Interval it Period Limited Exams ENCLOSURE R1-3 Page 40 of 105 Report No: UT-1 0-210
' Dom0nion" Summary# N1.R1.11o029 Pg. 5 of 5 Prepared By:, W.L. Thomas Date: 09128/2010 0,0-L~D(
WeldNumber Weld Thickness N/A Weld Lengthm WeYd Width 3,,
EXAMINATION LIMITED DUE TO:CONFIGURATION. AT THE HORIZONTAL CROSS SECTIONS THE EFFECTIVE ULTRASONIC BEAM COVERAGE IS LIMITED TO 58% OF THE CROSS SECTIONAL AREA FOR 50% OF THE WELD LENGTH. AT THE CURVED CROSS SECTIONS OF THE WELD, THE EFFECTIVE ULTRASNIC COVERAGE IS 100% OF THE WELD FOR 50%
OF THE WELD LENGTH. AXIAL SCAN COVERAGE= (58% + 100%)112 = 79%,
CIRCUMFERENTIAL SCAN COVERAGE IS LIMITED DUE TO THE WELD CROWN I RADIUS FOR THE ENTIREWELD LENGTH. CIRC EXAM COVERAGE = 1.0 SQ- INCH OF THE TOTAL EXAM VOLUME 2.46 SQ. INCHES. 112.,46 = 41% CIRCUMFERENTIAL COVERAGE.
,,,,'iiJ' ,,...............
Examination Volume Dimensions - Height 083" Length " Width 2.96" Coverage summary Required Scans (eac*h has a wmtghing factor of 100 for complete coverage)
AANLE
'AK CRC 45 79% 41%
' .Code Coverage Total . 60%
79+41=120/200=60% Best Effort Covege (Max 25%) Total N/A Notes:
- 1) Code Coverage refers to the maximum percentage of the required examination volume that is effectively examined witr the qualMed examinatlon procedure.
- 2) Best Effort-Coverage refers to:the required examination volume past the weld centerline that is examined in Ihe axial beam direction With an Appendix VIII demonstrated procedure for single sided coverage.
_ 0-89.I
Serial No.13-141 Docket No. 50-338 Page 13 of 19 Serial No.12-660 Docket No. 50-338 NAPS Unit 1 4 h Interval 1- Period Limited Exams ENCLOSURE R3-2 Page 75 of 105 Report No: UT-I 0-209 Summary # Ni .R1 .20.028 9 D,0miniwn Pg. 5 of 5 Prepared By:. W.L. Thomas Date- 912512010 Weld Number 4 Weld Length 27.1 0.952" Weld Width 1 2" WcId Thickcness 6
- -.-- 1 1,. . 1 I ..
I I I 0 1 2 3 MyýMKMAC4CUTK4NMR ý DýA CL .4:
PIPE 42' MIT .9y" TOIAL RE UREMAJLVE [I5 E=0Z34SQ VCHES EXA1NB*WY.CF,:TUTALRECLUFEDVC.A
- E DS SiDE TMA_ FEWJ *MX (*ISSUE = ON.So IIH>ES NOEK6MNA'nc# PORQ2sQ. IZ-155LUS SEE AX DIFIIEtfON z 1/.3-.4 X MA1t6BM OFOWU -0 AGLUIREMCna -
Examirotion Vble ins nst s -ietght
- -0.31 . Length 27.1" . Width*--------- 7.- -X.
Cove table Sti mm ary * * .
Required Scans each has a weighing factor of 100 for ,omplete.coverage) uNOl
,pt-Ax,pt-r 'ntA ,ntGr 601. !41% "
100+100+41+0=241I4,00,, =60% Code Coverage Total 50%
- Best Effort Coverage(ax 25%) Total 10%
Notes:
- 1) Code Coverage refera to the maximum percentage of thue required examinalion volume that is effectivery examined with the qualified examination proceaiure.
- 2) Best Effort Coverage refers to the required examination volume past the weld centerline that I examined in the axial beam direction with an Appendix VIII demonstrated prcedure for single sided coverage, ANMI* DateZge*Jo Inltitl [O Final M-'
HSB-CT
Serial No.13-141 Docket No. 50-338 Page 14 of 19 Serial No.12-660 Docket No. 50-338 NAPS Unit 1 4 !h Interval 1I$Period Limited Exams ENCLOSURE R3-3 Page 80 of 105 Report No: UT-12-051 Summary # NLR1.20.057 2Dovndni el Pg. 5 of S Prepared by: W. Thomas ý0 -
Date: 415/2012 4
Weld Number 1 ANRII-e-fýL.___
Thickness .532" 8--
ntHaw~
Weld Length .14.125"
.7" Weld Width I"-: ....... . .
2 1 0 1 2 FLOW CL PIPM TEE M1r -frX.Br6W1)D16501IN. RE0UIFDE'MVCLLMELP5TANDI)NBT810 LyEMMID 1001OFTht K-RE DnWVOWLWE UR~TW
,. I3%e*
aE81rEnORrDawIrDAXOm4ECnOt
-:ýýVdil NOEnW- XIHPFItMIM 77 Examidnation Volume Dimensions - Height . .177" Lengtdh 14.425" Wrdth Wt*
nath 14.1.2501 Mdth Awe fi, Coverage Summary 1 Required Scans (each has a weighing factor of 100 for complete coverageJT ANGLE" UpS.t-Ax UpSt-Circ DnSt-.Ax DnSt-alrc 45 1(0% . 0%
70 "100%
60L
.. :Code Coverage Total* 50%
1004-100401-13=213/4=53, Best Effort Coverage (Max 2.S%) Total 3%
Notes:
1).Code Coverage refers to the maximum percentage of the required examination volume that Is effectively examined with the qualifled examination procedure.
- 2) Best Effort Coverage refers to the tequired examination volume past the weld centerline that is examined in the axial beam direction with an Appendix Viii demonstrated procedure for single sided coverage.
Serial No.13-141 Docket No. 50-338 Page 15 of 19 Serial No.12-660 Docket No. 50-338 NAPS Unit 1 41h Interval 15' Period Limited Exams ENCLOSURE R3-4 Page 84 of 105 Report No: UT-12-034 Diomblo Summary 4 N1.RL20,071 Pg. 4 of 4 Prepared by- W. Thomas Date: 4/3/2012 Weld Number . sW-I. Weld Width 1.4" Thickness 1.013" Weld Length 112.5' S:2 1 o 1 2 45i Dual covortee i1 1-t!fl, daimed for Risk Intormed and Aug7 OL 45 70i~a FPnJ G-~
.337rHTX I 2"WO Xl I 2.WLEW93TN -45.5 OWS IN. IPBQJIRED AMM VOLUMe VP6-1rAND DNST.
NO EXAM 05 AX DIRF&CIeN FOR .0230 *N. Xaa2G"LENCrM OFTHE REMeIRED DNZ!AXV0LUME
.0 X 50.26-1.12G14G.G- .2 X 100-2%MN0D5
,J E ,AAX0 DJNCMICM DINST'3IDE EXAmINeo a%9AX D~imcTvoaNs011SF SD EXAMtN4ED 00% AX OIRCT~FI UPSTSJCrE. , -
zx*JP~.4ito~o% UsarnE oRbDIREc-ioN.*aIm ~ Ot 1201 iSfO%. 0 Examination -Volume 13imensions - Height .337" Length 112.S" Width Avr ý '1 Coverage Summary I /~yy.
.- /
...Required Scans (each has a weighing factor of 100 for complete c~over, ge) -
ANGLE* ,UpSt,-Ax 'UpSt-Circ DnSt-Ax. .. OnSt-Circ 45 ,00% 50
"'70 "100%
Code Coveraue Total 87%
100. 100+98+50-348/4-87 Best. Effort Coverage.(Max 25%) Total N/A NRotes:
1),Code Coverage refers to the maximum percentage of the requiredexaminatlon volume that Is effectively examinPe with the qualified examination procedure.
Z) Best Effort Coverage refers to the required examlnation vorume pastthe weld centerline that is examined In the axial beam direction with an Appendix vni demonstrated procedure, for single sided coverage.
Serial No.13-141 Docket No. 50-338 Page 16 of 19 Serial No. 12-66(
Docket No. 50-331 NAPS Unit 1 4 th Interval 1it Period Limited Exam!
ENCLOSURE R3-5 Page 90 of 10!
Report No; UT412-037 SD11n1Iumio Surmnmyl # N1.R1.20.073 P6. 5 of 7 Prepared by: W. Thomas 100-Date: 4f3/2012 wl Weld Number SW-12 Weld Wldtlh L.4" Thick,*,ws 1.0AN Weld Lengt ~h 112.5" q I 2 SW12- rI-nw Dual Coerage Is tding daimed ror RIsk Infurmec and ALn'7.
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.249'X NT XtIA flOIjt 1125I LBNflTH -5 CUROg* INRBWFRED IW.AM VDL %UJflTANDIONCT".
W WU iU AP PX H*rUT F Ao02 MX E*" LUrH IC .5 Of' TS REJIRED ONST *X VOLMUMI CCP4C.0% WCKMeO1ONCRC? SOO. lOGIG DRWTCNtflTalog.
.CCD .C EUMWINi100% US SIDE CIRt DIREfIUL EXAtMINW 0165 CR0.3DG IROlDlCT.
Examination Volume Dimensions - He49ht ..3430 Length .112.5 Width 1A-4 L/
- 1 . -
Coverage Summary 1,4 Required Scans (each has a weighi*ng factor of 100 for complete coverage) ~ 17 K.'p ANGLE UpSt-Ax UpS t-Circ DnSt-Ax OnSt-Cin; 4.5 100% 50%
70 '100% "98%. .. .
Code Coverage Total 87%
100*100÷-550-98=348/4=87% Best Effort Coverage (Max 25%) Total N/A Notes:
- 1) Code Coverage reters to the maximum percentage of the required examination volume that Is effectively examined with the qualified examination procedure.
- 2) Best Effort Coverage refers to the required examination volume past the weld centedline that Isexamined in the axial beam direction with an Appendix VIII demonstrated procedure fur single sided coverage.
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Serial No.13-141 Docket No. 50-338 Page 17 of 19 NRC Question 5 The licensee requested relief from the required risk-informed (RI) - ISI examination coverage (greater than 90% of the ASME Code required volume) due to single-sided access and physical limitations. The staff notes that when the RI-ISI program is established, the welds should be selected such that the ASME Code required examination coverage is achievable.
The staff noted that RR N1-14-LMT-001, Attachment R1 through R3, contain the following statements:
In Attachment R1, the licensee stated that, "Inspection of these particular welds are considered the best choices for meaningful examination."
In Attachment R2, the licensee stated that, "No alternative selections are available to meet greaterthan 90% coverage."
In Attachment R3, the licensee stated that, "Inspection of these particular welds are considered the best choices for meaningful examination results."
It is unclear whether the licensee intended to state that, there were not any other welds with the same risk-significance subject to the same degradation mechanism that could be examined, and achieved the required examination coverage. Please clarify.
Or discuss whether there were other welds with the same risk-significance, subject to the same degradation mechanism that could be examined, and achieved the required examination coverage. If the answer is yes, then will the licensee substitute that weld for the subject weld in its RI-ISI program update?
Dominion Response The purpose of the inservice inspection (ISI) program is to assure the structural and pressure-retaining integrity of safety-related nuclear power plant components in accordance with the rules of the ASME Section Xl Code and the requirements of 10 CFR 50.55a. The risk-informed inservice inspection (RI-ISI) program approved in Request for Alternative Nl-14-RI-001 applies ASME Code Case N-716 to select and examine a cross-section of high safety significant (HSS) welds based on PRA modeling and other risk factors to assure the Code requirements for structural and pressure-retaining integrity. Although Dominion could select only weld locations where greater than 90% examination coverage is possible (when available based on selection criteria),
meeting the purpose of the Code requires selecting a mix of not only piping-to-piping
Serial No.13-141 Docket No. 50-338 Page 18 of 19 welds (where essentially 100% coverage is more likely), but also piping-to-valve welds, piping-to-pump welds, piping-to-vessel welds, socket welds, nozzle-to-pipe welds, etc.
The ASME Code allows only 50% Code coverage for single-sided examinations, and in cases other than most piping-to-piping welds, the majority of weld examinations are considered single-sided examinations.
On pages 25 of 105, and 65 of 105, of relief request NI-14-LMT-001, it is identified that "selections were made based on plant specific operating experience or history of examination, weld repairs, random selection across different pipe sizes and configurations, and radiation concerns." An effective examination program must include selections from different piping configurations, as well as selections from piping configurations categorized with different degradation mechanisms.
In the NRC Safety Evaluation for the NAPS RI-ISI Program, dated January 21, 2011, it was accepted that our intention was to focus inspection on the most safety-significant welds. In considering degradation mechanisms, although the entire section of pipe is subject to the degradation mechanism, the risk significance of each weld in a piping system may vary based on its configuration (valves, pumps, tanks, tees, elbows, etc.).
The selection of welds must include these locations, even if the Code allowed coverage is only 50%, in order to provide reasonable assurance of safety.
The specific selections in this request include R1.11 components on 6-inch branch lines off of Reactor Coolant loop piping, R1.16 components on 6-inch and 12-inch Safety Injection lines, and various R1.20 components. These selections represent various configurations of HSS components.
There are a total of twenty 6-inch R1.11 components off of Reactor Coolant Loop piping. Fifteen of these components have been selected for examination as part of the RI-ISI Program. Six welds connect piping or elbows to check valves. Three of those six are included in this request, and the other three are scheduled to be examined later in the interval. All of these are single-sided examinations, with coverage no greater than 50%. There are three branch connection welds to the hot-legs. One is included in this request and another is scheduled to be examined later in the interval. These three welds are subject to similar limitations. There are three pipe-coupling welds at the previously mentioned branch connections. Previous examinations of these welds have been limited. Two of the pipe-coupling welds are scheduled to be examined later in the interval. Of the remaining eight welds, four have been examined successfully and another is scheduled to be examined later in the interval. The only three remaining R1.11 weld locations with the possibility of achieving full examination coverage are located on the same branch line from the cold leg. Two of these welds have already been examined successfully. Therefore, these welds are not good choices for achieving a representative sampling of locations subject to the given degradation mechanism.
Serial No.13-141 Docket No. 50-338 Page 19 of 19 There are a total of nine R1.16 components. All are associated with the Safety Injection System. In addition to the two welds included in this request, there is one additional weld scheduled for examination later in the interval. These nine welds connect valves to piping or elbows, and examination of these welds would be single-sided with coverage no greater than 50%. The best selections representing the configurations in the plant that avoid less than the maximum 50% coverage, while providing additional non-Code coverage, have been selected.
Among R1.20 components (HSS welds with no particular degradation mechanism) it is possible to select only piping-to-piping welds that provide full coverage. There are twenty-seven 8-inch Reactor Coolant piping components, with four selected for examination. Three are nozzle-to-pipe, cast stainless steel component-to-stainless steel piping configurations, and all three will be limited. It is reasonable to select these locations because they connect to the Loop Stop Motor-Operated valves, which are dynamic components that are also subject to inspections and maintenance during outages. There is also an elbow-to-pipe weld included in the selections. It is noted that there are two other welds among the 8-inch RC piping components that were examined during the Third ISI Inspection Interval. These welds received full coverage and could still be considered for examination during the Fourth Inspection Interval.
There are three 4-inch Reactor Coolant System R1.20 welds selected for examination among seventy-nine possible components. The first weld has been examined with essentially 100% coverage. The second weld is a pipe-to-pipe weld that will likely be examined with full coverage. The third weld is included in this request and is single-sided. There are also three other welds among the seventy-nine that are examined each inspection period as part of an augmented inspection program (UT and PT each period). The selected welds are representative of the types of welds in the Reactor Coolant System.
There are four possible selections for 4-inch Chemical and Volume Control system R1.20 welds. The weld with the best access for examination was selected, and it is included in this relief request.
The six Main Steam System R1.20 weld selections are the most significant among the thirty possibilities. These six welds have also been included in our augmented inspection program for Main Steam Postulated Break Locations. The 87% UT coverage along with the 100% MT coverage is sufficient to ensure structural integrity at these locations.