ML14063A206
| ML14063A206 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 02/27/2014 |
| From: | Sartain M D Dominion, Dominion Nuclear Connecticut |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 13-566A, TAC MF2520 | |
| Download: ML14063A206 (15) | |
Text
AlDominion-Dominion Nuclear Connecticut, Inc.5000 Dominion Boulevard, Glen Allen, VA 23060Web Address:
www, doix.comFebruary 27, 2014U.S. Nuclear Regulatory Commission Attention:
Document Control DeskWashington, DC 20555Serial No.NLOSA/WDC Docket No.License No.13-566ARO50-336DPR-65DOMINION NUCLEAR CONNECTICUT, INC.MILLSTONE POWER STATION UNIT 2RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION FORALTERNATIVE REQUEST RR-04-16 FOR THE USE OF ENCODED PHASEDARRAY ULTRASONIC EXAMINATION TECHNIQUES (PAUT) IN LIEU OFRADIOGRAPHY (TAC NO. MF2520)In a letter dated August 1, 2013, Dominion Nuclear Connecticut, Inc. (DNC) requested relief from the requirements of the American Society of Mechanical Engineers (ASME)Boiler and Pressure Vessel Code Section III for Millstone Power Station Unit 2(MPS2). Specifically, DNC requested approval to use encoded Phased ArrayUltrasonic Examination Techniques as an alternative to radiographic examination forASME Class 2 carbon steel circumferential pipe weld joints to satisfy nondestructive examination requirements.
In a letter dated October 1, 2013, the Nuclear Regulatory Commission (NRC) transmitted a request for additional information (RAI) to DNCrelated to the alternative request.
In a letter dated November 22, 2013, DNCresponded to RAI Questions 2, 3.a, 3.c, 3.d, 3.e, 5, and 6.The attachment to this letter containsQuestions 1, 3.b and 4.If you have any questions regarding this(804) 273-4687.
DNC's response to the remaining RAIsubmittal, please contact Wanda Craft atSincerely, Mark D. SartainVice President
-Nuclear Engineering
Attachment:
Response to Request for Additional Information for Alternative Request RR-04-16Proposed Alternative to ASME Section III.Commitments made in this letter: NoneAo4T Serial No. 13-566ADocket No. 50-336Page 2 of 2cc: U.S. Nuclear Regulatory Commission Region I2100 Renaissance BlvdSuite 100King of Prussia, PA 19406-2713 Mohan C. ThadaniProject ManagerU.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08 B 111555 Rockville PikeRockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station Serial No. 13-566ADocket No. 50-336ATTACHMENT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION FORALTERNATIVE REQUEST RR-04-16PROPOSED ALTERNATIVE TO ASME SECTION IIIMILLSTONE POWER STATION UNIT 2DOMINION NUCLEAR CONNECTICUT, INC.
Serial No. 13-566ADocket No. 50-336Attachment, Page 1 of 12Background In a letter dated August 1, 2013, Dominion Nuclear Connecticut, Inc. (DNC) requested relief from the requirements of the American Society of Mechanical Engineers (ASME)Boiler and Pressure Vessel Code Section III for Millstone Power Station Unit 2 (MPS2).Specifically, DNC requested approval to use encoded Phased Array Ultrasonic Examination Techniques (PAUT) as an alternative to radiographic examination forASME Class 2 carbon steel circumferential pipe weld joints to satisfy nondestructive examination requirements.
In a letter dated October 1, 2013, the Nuclear Regulatory Commission (NRC) transmitted a request for additional information (RAI) to DNCrelated to the alternative request.
In a letter dated November 22, 2013, DNC responded to RAI Questions 2, 3.a, 3.c, 3.d, 3.e, 5, and 6. This attachment provides DNC'sresponse to RAI Questions 1, 3.b and 4.Question 1Please provide examples of successful detections and characterizations of fabrication flaws, including lack of fusion defects, lack of penetration
- defects, cracks, slag, andporosity in representative welds using a representative ultrasonic procedure.
Includeflaw maps showing the true state for examples of each type of flaw including thosefound by penetrant
- testing, the ultrasonic results including detection andcharacterization of flaws, and the radiographic results for these specimens.
DNC ResponseThe following nine figures provide examples of the ultrasonic testing (UT) datarepresenting successful detections and characterizations of typical fabrication flawsfrom the Dominion procedure qualification data. These figures provide examples of lackof fusion defects, lack of penetration
- defects, cracks, slag inclusions, and porosity, which were implanted into the welded mockups.
These mockups represent the weldconfigurations and welding processes to be used for the replacement welds. The flawmap for each of these examples is included in the applicable figures.
No surfaceexaminations were performed for the implanted flaws. Radiography was performed foreach mockup weld. The radiography was performed using typical ASME Section V,Article 2 techniques with an Iridium 192 radiation source. The planar flaws identified inFigures 1, 3, 5, and 6 were not detected with the radiographic examination performed.
The UT procedure qualification has demonstrated 100% flaw detection capability.
100% of the near and far side circumferential flaws were detected when evaluated assingle side access. 100% of the axial flaws were detected using the circumferential beam direction data. The detected flaws were accurately categorized as either planaror volumetric type flaws. The flaws categorized as volumetric flaws were accurately length-sized within 0.25" of the implanted size.
Serial No. 13-566ADocket No. 50-336Attachment, Page 2 of 12Figure 1Weld I -Flaw 9, Lack of FusionFLAW 9Upstream (Near Side) Detection Using Second LegDown Stream (Far Side) Detection Using First Leg Serial No. 13-566ADocket No. 50-336Attachment, Page 3 of 12Figure 2Weld 2 -Flaw 10, PorosityUpstream Detection Using First LegDown Stream Detection Using First Leg Serial No. 13-566ADocket No. 50-336Attachment, Page 4 of 12Figure 3Weld 2 -Flaw 16, CrackFLAW 16} F 0.090IU: IT... ... ..7Upstream Detection Using First LegDDiDown Stream Detection Using First LegI Serial No. 13-566ADocket No. 50-336Attachment, Page 5 of 12Figure 4Weld 2 -Flaw 18, Slag Inclusion FLAW 18Upstream Detection Using First LegDown Stream Detection Using First Leg Serial No. 13-566ADocket No. 50-336Attachment, Page 6 of 12Figure 5Weld 3 -Flaw 1, Lack of FusionO.40"Upstream (Near Side) Detection Using First and Second Legs=1r Irot -,.77=:;Down Stream (Far Side) Detection Using First LegI Serial No. 13-566ADocket No. 50-336Attachment, Page 7 of 12Figure 6Weld 3 -Flaw 4, CrackFLAW 4Upstream Detection Using First LegDown Stream Detection Using First Leg Serial No. 13-566ADocket No. 50-336Attachment, Page 8 of 12Figure 8Weld 8 -Flaw 12, CrackFLAW 12 F 0.180"i2}Upstream (Far Side) Detection Using First and Second LegsDown Stream (Near Side) Detection Using First and Second Legs Serial No. 13-566ADocket No. 50-336Attachment, Page 9 of 12Figure 9Weld 8- Flaw 19, Incomplete Penetration RAW 19Upstream Detection Using First LegDown Stream Detection Using First Leg Serial No. 13-566ADocket No. 50-336Attachment, Page 10 of 12Question 3The technical basis for the reliable detection and characterization of fabrication flawshas thus far assumed that the inspections will be conducted from both sides of the weld.The few experimental evaluations that have explored the reliability of single-sided ultrasonic testing (UT) suggest that detecting fabrication flaws, especially lack of fusiondefects, using single sided UT misses flaws found by inspections conducted from bothsides (see EPRI Report 1021181 page A-5 and the paper "An Empirical Study onUltrasonic Testing in Lieu of Radiography for Nuclear Power Plants" in the Proceedings of the 9th international conference on NDE in relation to structural integrity for nuclearand pressurized components).
As the technical basis for the detection andcharacterization of flaws from one side of the weld has not been established, thefollowing information on the single-sided examinations is required:
- b. If single-sided ultrasonic inspections are to be used in lieu of radiographic testing for welds covered in RR-04-16, please provide a technical basis justifying the use of single-sided examinations for fabrication defects in the subject welds.DNC ResponseMockups containing eight welds representative of the welds to be examined in the fieldwere fabricated to evaluate the capabilities of the ultrasonic examination techniques tobe used. These mockups are summarized in the following table. To maintain securityof the mockups to support blind personnel demonstrations and future procedure enhancement demonstrations, only general statements of the mockup designs areprovided.
Summary of the UT in Lieu of RT MockupsWeld Diameter/
l WNominal Thickness Configuration Weld ProcessGTAW -Root and Hot Pass1 ~~18" / 0.75" Pipe to Elbow SMW-Rmingel SMAW -Remaining Weld218" / 0.75" Elbow to Pipe GTAW -Root and Hot Pass2 1 SMAW -Remaining Weld3 18" / 0.75" Elbow to Elbow GTAW -Complete WeldGTAW -Root and Hot Pass4 6"/0.280" Pipe to Pipe SMAW -Remaining Weld5 6" / 0.280" Elbow to Pipe GTAW -Complete WeldGTAW -Root and Hot Pass6 6" / 0.280" Elbow to Pipe SMAW -Remaining Weld7 18" / 0.75" Elbow to Pipe GTAW -Complete WeldGTAW -Root and Hot Pass8 18" / 0.75" Elbow to Pipe SMAW -Remaining Weld Serial No. 13-566ADocket No. 50-336Attachment, Page 11 of 12Each of the eight welds was examined with RT, applying ASME Section V, Article 2techniques typically used for field RT examinations.
An interpretation of theradiographic film resulted in 30% of the implanted flaws not being detectable with theRT method. The flaws not detected with RT were all lack of fusion and crack planarflaws. The implanted volumetric flaws, i.e., inclusions and porosity, were all detected.
No surface examinations were performed for these welds.Each of the eight welds was examined ultrasonically with three independent scans thatincluded upstream axial beam direction, downstream axial beam direction, andcircumferential beam directions (clockwise and counter clockwise).
The data analysiswas performed to evaluate each axial beam scan independently to represent limitedsingle side access conditions.
Addressing each scan direction independently provided116 circumferential flawed grading unit opportunities to be used for the procedure qualification and provided an independent evaluation of each of the circumferential flaws from both sides of the weld. This approach resulted in 35% of the circumferential flawed grading units being evaluated as far side of the weld flaws and the remaining 65% being evaluated as near side of the weld flaws. The implanted flaws consisted of27% being volumetric (inclusions and porosity) and 73% of the flaws being planar (lackof fusion, incomplete penetration, and cracks) that are representative of the weldingprocesses being used.When compared to volumetric or far side planar fabrication flaws, near side planar flawsare more difficult to detect with standard ultrasonic examination techniques due to theorientation of the flaws with the ultrasonic beam. The use of multiple examination angles and full V-path encoded phased array techniques demonstrate enhanced flawdetection capabilities for both near and far side weld access conditions.
The procedure qualification has demonstrated 100% flaw detection capability.
100% of the near andfar side circumferential flaws were detected when evaluated as single side access.100% of the axial flaws were detected using the circumferential beam direction data.The detected flaws were accurately categorized as either planar or volumetric typeflaws. The flaws categorized as volumetric flaws were accurately length-sized within0.25" of the implanted size.In summary, the Dominion procedure qualification has demonstrated that the ultrasonic examination techniques are more reliable for the detection of critical planar fabrication flaws than the standard RT examination techniques used for weld examinations.
Inaddition, the procedure qualification has demonstrated effective and reliableexamination capabilities for both near and far sided examination access. Thedemonstrated procedure is effective for proper categorization of detected flaws andaccurate length-sizing of volumetric flaws. The demonstrated procedure meets all ofthe requirements of the demonstration process outline within RR-04-16.
Serial No. 13-566ADocket No. 50-336Attachment, Page 12 of 12Question 4The current technical basis for performing ultrasonic inspections in lieu of radiography assumes that the weld crowns will be removed and machined or ground flush. Will theweld crowns of the welds covered in RR-04-16 be machined or ground flush prior to theproposed ultrasonic inspections?
If the weld crowns are not to be ground flush, pleaseprovide a technical basis, including a detailed description of the ultrasonic inspection procedure, showing that inspections with the weld crown present are able to reliablydetect and characterize fabrication flaws.DNC ResponseThe weld crowns will be ground flush prior to the ultrasonic examination.