ML093020466
| ML093020466 | |
| Person / Time | |
|---|---|
| Site: | Hope Creek  |
| Issue date: | 11/19/2009 |
| From: | Chernoff H Plant Licensing Branch 1 |
| To: | Joyce T Public Service Enterprise Group |
| Ennis R, NRR/DORL, 415-1420 | |
| References | |
| TAC ME0230 | |
| Download: ML093020466 (18) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 November 19, 2009 Mr. Thomas Joyce President and Chief Nuclear Officer PSEG Nuclear P.O. Box 236, N09 Hancocks Bridge, NJ 08038
SUBJECT:
SAFETY EVALUATION OF RELIEF REQUEST FOR THE SECOND 10-YEAR INTERVAL OF THE INSERVICE INSPECTION PROGRAM FOR HOPE CREEK GENERATING STATION (TAC NO. ME0230)
Dear Mr. Joyce:
By letter dated December 11, 2008, as supplemented by letter dated July 28, 2009, PSEG Nuclear LLC (PSEG or the licensee) submitted relief request HC-12-RR-A25 which requested relief from certain requirements specified in Section XI of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) for the inservice inspection (lSI) of components at Hope Creek Generating Station (HCGS). PSEG stated that it had conducted examinations as part of the second 10-year lSI interval to the extent practical. However, coverage for examinations of the subject components was less than required by the ASME Code.
The U.S. Nuclear Regulatory Commission (NRC) staff, with technical assistance from its contractor, the Pacific Northwest National Laboratory, has completed its review of relief request HC-12-RR-A25 as documented in the enclosed Safety Evaluation. The NRC staff concludes that the ASME Code examination coverage requirements are impractical for the subject components listed in the relief request. However, based on the volumetric and/or surface coverage obtained, it is concluded that if significant service-induced degradation had occurred, there is reasonable assurance that evidence of it would have been detected by the examinations that were performed. As such, the NRC staff further concludes that there is reasonable assurance of the structural integrity and/or leak tightness of the subject components based on the examinations that have been performed. Therefore, the NRC staff is granting PSEG's request for relief pursuant to 10 CFR 50.55a(g)(6)(i), for the second 10-year lSI interval at HCGS.
Granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the public interest given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
All other ASME Code,Section XI requirements for which relief was not specifically requested and approved remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
- 1. Joyce
- 2 If you have any questions concerning this matter, please contact the HCGS Project Manager, Mr. Richard Ennis, at (301) 415-1420.
Sincerely, 1 f
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Harold K. Chernoff, Chief Plant Licensing Branch 1-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-354
Enclosure:
Safety Evaluation cc w/encl: Distribution via ListServ
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO RELIEF REQUEST FOR THE SECOND 10-YEAR INTERVAL OF THE INSERVICE INSPECTION PROGRAM PSEG NUCLEAR LLC HOPE CREEK GENERATING STATION DOCKET NO. 50-354
1.0 INTRODUCTION
By letter dated December 11, 2008, as supplemented by letter dated July 28, 2009 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML083590292 and ML092240586, respectively), PSEG Nuclear LLC (PSEG or the licensee) submitted relief request HC-12-RR-A25 which requested relief from certain requirements specified in Section XI of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) for the inservice inspection (lSI) of certain components at Hope Creek Generating Station (HCGS). PSEG stated that it had conducted examinations as part of the second 10-year lSI interval to the extent practical. However, coverage for examinations of the subject components was less than required by the ASME Code.
2.0 REGULATORY EVALUATION
The lSI of ASME Code Class 1, 2, and 3 components is to be performed in accordance with Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," of the ASME Code and applicable edition and addenda as required by Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a(g), except where specific relief has been granted by the Nuclear Regulatory Commission (NRC or the Commission) pursuant to 10 CFR 50.55a(g)(6)(i).
Pursuant to 10 CFR 50.55a(a)(3), alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if the licensee demonstrates that: (i) the proposed alternatives would provide an acceptable level of quality and safety, or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) must meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulation requires that inservice examination of components and system pressure tests conducted during the first 1O-year interval, and subsequent intervals, comply with Enclosure
- 2 the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein.
The second 10-year lSI interval at HCGS began on December 13,1997, and ended on December 12, 2007. The ASME Code of record for the start of the second 1O-year lSI interval was the 1989 Edition, no Addenda, of Section XI of the ASME Code. However, beginning with the third period of the interval, the licensee updated the ASME Code of record for HCGS to the 1998 Edition up through and including the 2000 Addenda.
3.0 TECHNICAL EVALUATION
The NRC staff, with technical assistance from its contractor, the Pacific Northwest National Laboratory (PNNL), evaluated the information provided by PSEG in support of the subject relief request as documented below. For clarity, the request has been evaluated in several parts according to ASME Code Examination Category.
3.1 Request for Relief HC-12-RR-25 (Part A), ASME Code,Section XI, Examination Category B-A, Items B1.12 and B1.40, Pressure Retaining Welds in Reactor Pressure Vessel ASME Code Requirement ASME Code,Section XI, Examination Category B-A, Item B1.12 requires essentially 100 percent volumetric examination, as defined by ASME Code,Section XI, Figure IWB-2500-2, of the length of longitudinal shell welds on the reactor pressure vessel (RPV). ASME Code,Section XI, Item B1.40 requires essentially 100 percent VOlumetric and surface examination of the length of head-to-flange welds, as defined by ASME Code,Section XI, Figure IWB-2500-5. "Essentially 100%," as clarified by ASME Code Case N-460, "Alternative Examination Coverage for Class 1 and Class 2 Welds," is greater than 90 percent coverage of the examination volume, or surface area, as applicable. ASME Code Case N-460 has been approved for use by the NRC in Regulatory Guide (RG) 1.147, Revision 15, "Inservice Inspection Code Case Acceptability."
Licensee ASME Code Relief Request In accordance with 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from the ASME Code-required 100% volumetric examination of the ASME Code, Class 1 RPV welds shown in Table 3.1.1.
- 3 81.12 RPV1-W12-1 81.12 RPV1-W12-2 81.12 RPV1-W12-3 81.40 RPVI-W20 Longitudinal Seam at 110Deg Longitudinal Seam at 230Deg Longitudinal Seam at 350Deg Head-to-Flange 71.40%
70.00%
71.50%
70.23%
Licensee's 8asis for Relief Request (as stated)
"[ASME] Code required coverage is impractical for the identified subject components due to the head flange configuration preventing ultrasonic examination from the flange side of the head flange weld, and proximity of core spray internal piping and feedwater spargers to the [RPV] longitudinal weld seams limiting access to the weld seams."
"The [RPV] longitudinal weld seams were examined from inside the [RPV]. Additional coverage could have been obtained if the inspection was performed from outside the
[RPV] but this would cause additional radiation dose to obtain access to the weld and to examine the weld."
"To obtain full coverage of the flange, the [RPV] would require design modifications. This would impose a significant burden to PSEG."
Licensee's Proposed Alternative Examination (as stated)
"No alternative provisions are practical for the subject welds. Examinations were performed to the maximum extent practical with no reportable indications."
"Subject components have been subjected to a visual leakage examination after completion of each refueling outage. The head flange was also fully examined by
[magnetic particle testing (MT)] with no reportable indications. These exams provide additional assurance that the structural integrity of the subject components was maintained."
NRC Staff Evaluation
The ASME Code requires essentially 100 percent volumetric examination of the accessible length of the subject RPV welds. However, complete examinations are restricted by the proximity of core spray internal piping and feedwater spargers for the RPV longitudinal weld seams, and the geometric configuration of the RPV flange and head-to-flange weld. In order to increase the volumetric coverage on the subject welds, the RPV would require design modifications. Imposing this requirement would place a
-4 burden on the licensee; therefore, the ASME Code-required 100 percent volumetric examinations are impractical.
As shown on the sketches and technical descriptions1 included in the licensee's submittal, ultrasonic (UT) examinations of the subject longitudinal seam welds have been performed to the extent practical. The sketches for the subject welds show the feedwater sparger and core spray internal piping obstructions to the examination areas.
The longitudinal seam welds were examined from the inside surface using procedures that were qualified through performance demonstration requirements of ASME Code,Section XI, Appendix VIII. The licensee obtained volumetric coverage ranging from approximately 70 percent to 72 percent (see Table 3.1.1 above). For the RPV head-to-flange weld, 60-degree ultrasonic shear wave examinations were performed on the weld region. However, no UT examination coverage was obtained from the flange side due to the curvature between the flange and head weld area which causes contact of the ultrasonic unit to be interrupted. Full coverage was achieved during the MT surface examination. No recordable indications were observed during any of the examinations.
As discussed above, it is impractical to meet the ASME Code-required examination coverage for the subject welds. However, based on the volumetric and surface coverage obtained, it is concluded that if significant service-induced degradation had occurred, there is reasonable assurance that evidence of it would have been detected by the examinations that were performed. As such, the NRC staff further concludes that there is reasonable assurance of structural integrity of the subject welds based on the examinations that have been performed.
3.2 Request for Relief HC-12-RR-25 (Part 8), ASME Code. Section XL Examination Category 8-0. Item 83.90, Full Penetration Welded Nozzles in Vessels ASME Code Requirement ASME Code,Section XI, Examination Category 8-0, Item 83.90 requires 100 percent volumetric examination, as defined by ASME Code,Section XI, Figure IW8-2500-7 (a-d, as applicable) of ASME Code, Class 1 nozzle-to-shell welds on the RPV. ASME Code Case N-460, as an alternative approved for use by the NRC in RG 1.147, Revision 15, states that a reduction in examination coverage due to part geometry or interference for any Class 1 and 2 weld is acceptable provided that the reduction is less than 10 percent (i.e., greater than 90 percent examination coverage is obtained).
Licensee ASME Code Relief Request In accordance with 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from the ASME Code-required 100 percent volumetric examination of the nozzle-to-vessel welds shown in Table 3.2.1.
Sketches and technical descriptions provided by the licensee in its letters dated December 11, 2008, and July 28,2009 (ADAMS Accession Nos. ML083590292 and ML092240586, respectively) are not included in this safety evaluation (SE).
- 5 RPV1-N2B RPV1-N2C RPV1-N2J RPV1-N2K RPV1-N4A Nozzle-to-shell weld 12" recirc inlet at 60 de Nozzle-to-shell weld 12" recirc inlet at 90 de Nozzle-to-shell weld 12" recirc inlet at 300 de Nozzle-to-shell weld 12" recirc inlet at 330 de Nozzle-to-shell weld 77.45%
77.45%
77.45%
77.45%
75.00%
RPV1-N4B Nozzle-to-shell weld 75.00%
RPV1-N4C Nozzle-to-shell weld 71.00%
RPV1-N4D Nozzle-to-shell weld 75.00%
RPV1-N4E Nozzle-to-shell weld 75.00%
RPV1-N4F Nozzle-to-shell weld 71.00%
RPV1-N5A Nozzle-to-shell weld 10" core spray inlet at 120 de 77.45%
77.45%
75.00%
75.00%
75.00%
75.00%
75.00%
75.00%
75.00%
75.00%
77.45%
l'Jozzle-to-shell at 45 de Nozzle-to-shell 4" 'et instrumentation Nozzle-to-shell at 135 de Nozzle-to-head s ra nozzle Nozzle-to-shell weld 10" core spray inlet at 240 de Nozzle-to-head vent nozzle Nozzle-to-shell at 315 de Nozzle-to-head s are head nozzle Nozzle-to-shell weld 4" CRD h draulic return Nozzle-to-shell 'et instrumentation RPV1-N17D RPV1-N17B RPV1-N9A RPV1-N8B RPV1-N5B RPV1-N6A RPV1-N17A RPV1-N8A RPV1-N6B PV1-N7 Licensee's Basis for Relief Request (as stated)
"ASME Code required coverage is impractical for the subject components due to nozzle configuration and therefore portions of the ASME Code required examination volume cannot be completely examined with ultrasonic techniques. The curvature of the blend radius of nozzle forgings prevents ultrasonic scanning of the weld from the nozzle side."
"Altering the [RPV] or nozzle configuration would require design modifications that would impose a significant burden to PSEG."
Licensee's Proposed Alternative Examination (as stated)
"No alternative provisions are practical for the subject welds. Examinations were performed to the maximum extent practical with no reportable indications."
"Subject components have been subjected to a visual leakage examination after completion of each refueling outage. This provides additional assurance that the structural integrity of the subject components was maintained."
- 6
NRC Staff Evaluation
The ASME Code requires 100 percent volumetric examination of full penetration welded nozzles in the RPV. However, examinations of the nozzles listed in Table 3.2.1 (see above) are limited by the design of the components, and the curvature of the nozzle-to-shell blend radius, which precludes ultrasonic examination to the extent required by the ASME Code. In order for the licensee to obtain 100 percent of the ASME Code-required examination coverage of the subject welds, both the RPV and the nozzles would need to be redesigned and modified. Imposing this requirement would place a burden on the licensee, therefore, the ASME Code-required 100 percent volumetric examinations are considered impractical.
As shown on the sketches and technical descriptions included in the licensee's submittal, examination of the subject nozzles has been performed to the extent practical with the licensee obtaining volumetric coverage ranging from approximately 71 percent to 77 percent. These nozzles are of the "set-in" design which essentially makes the welds concentric rings aligned parallel with the nozzle axes in the through-wall direction of the RPV shell. This design geometry limits ASME Code-required ultrasonic angle beam examinations to be performed only from the shell side of the welds. In addition, nozzle side scans were limited by the nozzle-to-shell blend radii, which cause contact of the ultrasonic search unit to be interrupted. This blend radius limitation affects both axial and circumferential scanning of the ASME Code-required examination volumes.
The UT examinations on the subject carbon steel nozzle welds included O-degree longitudinal, and 45-,50- and 60-degree shear waves from the shell side only. However, 100 percent volume coverage was only obtained using the transverse technique with the 45 - and 60-degree scan angles for nozzle-to-shell welds RPV1-N2B, RPV1-N2C, RPV1 N2J, RPV1-N2K, RPV1-N5A, RPV1-N5B, and RPV1-N9A. Examinations of these welds were performed prior to the implementation of UT methods qualified through performance demonstration initiative (POI) requirements of ASME Code,Section XI, Appendix VIII. Nozzle-to-shell welds RPV1-N4A, RPV1-N4B, RPV1-N4C, RPV1-N40, RPV1-N4E, RPV1-N4F, RPV1-N8A, RPV1-N8B, RPV1-N17A, RPV1-N17B, NRPV1-N170, RPV1-N6A, RPV1-N6B, and RPV1-N7 were examined using methods qualified through performance demonstration requirements of ASME Code,Section XI, Appendix VIII. No recordable indications were observed in the subject nozzle welds.
Although UT scans were primarily limited to the shell side only, recent studies have found that inspections conducted through carbon steel are equally effective whether the ultrasonic waves have only to propagate throu~h the base metal, or have to also propagate through the carbon steel weldment.
As discussed above, it is impractical to meet the ASME Code-required examination coverage for the subject welds. However, based on the volumetric coverage obtained, it is concluded that if significant service-induced degradation had occurred, there is reasonable assurance that evidence of it would have been detected by the examinations P. G. Heasler, and S. R. Doctor, 1996. Piping Inspection Round Robin, NUREG/CR-5068, PNNL-10475, U. S. Nuclear Regulatory Commission, Washington, DC.
2
- 7 that were performed. As such, the NRC staff further concludes that there is reasonable assurance of structural integrity of the subject welds based on the examinations that have been performed.
3.3 Request for Relief HC-12-RR-25 (Part C), ASME Code,Section XI, Examination Category B-G-1, Item B6.40, Pressure Retaining Bolting Greater Than 2 Inches in Diameter ASME Code Requirement ASME Code,Section XI, Examination Category B-G-1, Item B6.40, requires 100 percent volumetric examination, as defined by ASME Code, Figure IWB-2500-12, of the threaded ligament area around each stud hole in the RPV closure flange. ASME Code Case N-460, as an alternative approved for use by the NRC in RG 1.147, Revision 15, states that a reduction in examination coverage due to part geometry or interference for any Class 1 and 2 weld is acceptable provided that the reduction is less than 10 percent, (i.e., greater than 90 percent examination coverage is obtained).
Licensee's ASME Code Relief Request In accordance with 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from the ASME Code-required 100 percent volumetric examination of the threaded ligaments surrounding stud holes in the RPV head closure flange.
Licensee's Basis for Relief Request (as stated)
"[ASME] Code required coverage is impractical for the identified subject component due to head flange configuration. The [ultrasonic (UT)] examination of the threads in the flange is performed on the exposed carbon steel [RPV] flange around the stud holes.
The flange has stainless steel cladding from the inside surface of the vessel to approximately 3/8 inch from the stud hole. The rUT] transducer does not have access to this small area of the exposed carbon steel flange between the stud hole and the cladding."
"Altering the head flange design or bolting configuration would require design modification that would impose a significant burden on PSEG."
Licensee's Proposed Alternative Examination (as stated)
"No alternative provisions are practical for the subject component. Examinations were performed to the maximum extent practical with no reportable indications."
"Subject component has been subjected to a visual leakage examination after completion of each refueling outage. This provides additional assurance that the structural integrity of the subject component was maintained."
- 8
NRC Staff Evaluation
The ASME Code requires 100 percent volumetric examination of ASME Code, Class 1 threaded ligament areas in the RPV closure flange. However, examinations of these areas at HCGS are limited due to the design of the flange geometry and adjacent cladding. In order for the licensee to obtain 100 percent of the ASME Code-required examination coverage, the closure head flange would need to be redesigned and modified. This would place a burden on the licensee; therefore the ASME Code examinations are impractical.
The RPV threaded flange ligament areas, designated as RPV1-THDF by the licensee, are designed such that the cladding surface is approximately 1/4-inch higher than the surface of the carbon steel ligament areas. A machined edge exists that creates an inaccessible 3/8-inch area between the edge of cladding and stud hole. Thus, ultrasonic probes cannot make the necessary contact in this area to allow ultrasonic beam projection into the full ASME Code-required threaded (flange ligament) region. As shown on the sketch and technical descriptions included in the licensee's submittal, examination of the RPV flange threads has been performed to the extent practical. The licensee has achieved 75 percent of the ASME Code-required coverage. These examinations were performed prior to the implementation of performance demonstrated procedures qualified to ASME Code, Appendix VIII. No reportable flaws were detected during the examination of these threaded areas.
As discussed above, it is impractical to meet the ASME Code-required examination coverage for the subject component. However, based on the volumetric coverage obtained, it is concluded that if significant service-induced degradation had occurred, there is reasonable assurance that evidence of it would have been detected by the examinations that were performed. As such, the NRC staff further concludes that there is reasonable assurance of structural integrity of the subject component based on the examinations that have been performed.
3.4 Request for Relief HC-12-RR-25 (Part D), ASME Code,Section XI, Examination Category 8-J, Items 89.11 and 89.31! Pressure Retaining Welds in Piping ASME Code Requirement ASME Code,Section XI, Examination Category 8-J, Item 89.11 requires essentially 100 percent VOlumetric and surface examinations, as defined by ASME Code,Section XI, Figure IW8-2500-8, of the length of ASME Code, Class 1 circumferential piping welds.
ASME Code,Section XI, Item 89.31 requires essentially 100% surface and volumetric examinations, as defined in ASME Code,Section XI, Figure IW8-2500-9, -10, or -11, as applicable, of the length of piping branch connection welds, 4-inch nominal pipe size or larger. "Essentially 100%", as clarified by ASME Code Case N-460 is greater than 90 percent coverage of the examination volume, or surface area, as applicable. ASME Code Case N-460 has been approved for use by the NRC in RG 1.147, Revision 15.
- 9 Licensee ASME Code Relief Request In accordance with 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from the ASME Code-required 100 percent volumetric and, for Weld 1-FC-4DBA-003-16 only, surface examinations of the ASME Code, Class 1 piping welds shown in Table 3.4.1.
B9.11 B9.11 B9.11 B9.11 B9.11 B9.11 B9.11 B9.11 B9.31 B9.31 B9.31 B9.31 B9.31 1-BB-28VCA-013-6-R2 1-BC-6DBA-003-21 1-BC-12CCA-116-5
'I-BG-4CCA-012-1 1-BG-4CCA-011-1 1-FC-4DBA-003-7A 1-FC-4DBA-003-7B 1-FC-4DBA-003-16 1-BB-22VCA-013-3BC1 1-BB-22VCA-013-3BC2 1-BB-22VCA-014-1 BC1 1-BB-22VCA-014-1 BC2 1-BB-22VCA-014-3BC2 Pipe-to-Reducing Tee Valve-to-Flange Pipe-to-Reducing Tee Weldolet-to-Pipe Weldolet-to-Pipe Pipe-to-Flow Element Flow Element-to-Pipe EIbow-to-Pipe 12-in Branch Connection 12-in Branch Connection 12-in Branch Connection 12-in Branch Connection 12-in Branch Connection 50.00%
33.33%
80.20%
50.00%
50.00%
67.90%
76.20%
51.8% (MT) 26.05%
75.00%
75.00%
75.00%
75.00%
75.00%
Licensee's Basis for Relief Request (as stated)
"[ASME] Code required coverage is impractical for the identified subject components due to reducing tee configuration, branch piping configuration, valve and flange configuration, weld crown contours, weld-o-Iet configuration, sock-o-Iet configuration, and a pipe support. These issues limit or prevent full examination of the subject weld."
"Altering these components would require design modifications that would impose a burden on PSEG from a cost and radiation dose perspective."
Licensee's Proposed Alternative Examination (as stated)
"No alternative provisions are practical for the subject welds. Examinations were performed to the maximum extent practical with no reportable indications."
"Subject components have been subjected to a visual leakage examination after completion of each refueling outage. Also all components, except for one that was limited by a pipe support, were also fully examined by [dye penetrant (PT)] with no reportable indications. This provides additional assurance that the structural integrity of the subject components was maintained."
- 10
NRC Staff Evaluation
The ASME Code requires essentially 100 percent volumetric and surface examinations for selected ASME Code,Section XI, Examination Category B-J pressure retaining welds in piping. However, complete volumetric examinations are restricted by several factors, including pipe fitting, weld crown, and branch connection configurations. These conditions preclude the licensee obtaining full volumetric examinations from both sides of the weld. To gain access for examination, the welds would require design modifications.
Imposition of this requirement would place a burden on the licensee; therefore, the ASME Code-required 100 percent volumetric examinations are impractical.
As shown on the sketches and technical descriptions included in the licensee's submittal, examinations of the subject welds have been performed to the extent practical with the licensee obtaining volumetric coverage ranging from 26 to 80 percent (see Table 3.4.1 above). Various scan limitations in the axial and circumferential directions were caused by the configuration of the welds and interfering adjacent components as stated previously. The ultrasonic examinations conducted by the licensee included 45 degree, 60 degree, and 70 degree shear wave scan angles. In addition, the licensee performed 45 degree, and in some cases 60 degree, refracted longitudinal wave (L-wave) examinations from the accessible side of these welds. The L-wave method is believed capable of detecting planar inside diameter (ID) surface-breaking flaws on the far-side of wrought stainless steel welds. Studies 3, 4 reported in the technical literature recommend the use of both shear and L-waves to obtain the best detection results, with minimum false calls, in austenitic welds. For the subject pipe welds, volumetric examinations were conducted using manual techniques qualified in accordance with performance demonstration requirements listed in ASME Code,Section XI, Appendix VIII. The licensee completed the ASME Code-required surface PT examinations on the subject austenitic welds, with no limitations. However, limited coverage of approximately 52 percent was obtained with the MT surface examination for carbon steel elbow-to-pipe Weld 1-FC-4DBA-003-16 due to an adjacent pipe support that restricted access to a portion of the weld. No recordable indications were observed during any of the ultrasonic and surface examinations.
As discussed above, it is impractical to meet the ASME Code-required examination coverage for the subject welds. However, based on the volumetric and surface coverage obtained, it is concluded that if significant service-induced degradation had occurred, there is reasonable assurance that evidence of it would have been detected by the examinations that were performed. As such, the NRC staff further concludes that there is reasonable assurance of structural integrity of the subject welds based on the examinations that have been performed.
3 F. V. Ammirato, X. Edelmann and S. M. Walker. 1987. "Examination of Dissimilar Metal Welds in BWR Nozzle-to-Safe End Joints," s" International Conference on NDE in the Nuclear Industry, ASM International.
4 P. Lemaitre, T. D. Koble, and S. R. Doctor, 1995. "PISC III Capability Study on Wrought-to-Wrought Austenitic Steel Welds: Evaluation at the Level of Procedures and Techniques," Effectiveness of Nondestructive Examination Systems and Performance Demonstration, PVP-Volume 317, NDE-Volume 14, ASME.
- 11 3.5 Request for Relief HC-12-RR-25 (Part El, ASME Code,Section XI, Examination Category C-G, Item C6.10, Pressure Retaining Welds in Pumps and Valves ASME Code Requirement ASME Code,Section XI, Examination Category C-G, Item 6.10, requires 100 percent surface examination, as defined by ASME Code,Section XI, Figure IWC-2500-8, for ASME Code, Class 2 pump casing welds. ASME Code Case N-460, as an alternative approved for use by the NRC in RG 1.147, Revision 15, states that a reduction in examination coverage due to part geometry or interference for any Class 1 and 2 weld is acceptable provided that the reduction is less than 10 percent (Le., greater than 90 percent examination coverage is obtained).
Licensee ASME Code Relief Request In accordance with 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from the ASME Code-required 100% surface examination of Core Spray Pump casing Weld CP 206 CSP-W2.
Licensee's Basis for Relief Request (as stated)
"A major portion of the Core Spray Pump Casing Weld, CP 206-CSP-W2 is embedded in the concrete pump pedestal. Relief Request RR-C1, Part C, for the second inspection interval requested relief for 73% coverage for this weld. This coverage was based on the first interval data sheets reporting 73% coverage. Subsequent review of the first interval data sheets showed that the exam was 73% limited due to inaccessibility because of the pump pedestal. The second interval examination of this weld achieved 23.4% coverage due to the concrete pump pedestal obstruction."
"Altering this component would require a design modification that would impose a burden on PSEG from a cost and radiation dose perspective."
Licensee's Proposed Alternative Examination (as stated)
"No alternative provisions are practical for the subject weld. Examinations were performed to the maximum extent practical with no reportable indications."
"The subject component has been subjected to a visual leakage examination during each period of the interval. This provides additional assurance that the structural integrity of the subject component was maintained."
NRC Staff Evaluation
The ASME Code requires 100 percent surface examination of selected ASME Code, Class 2 pump casing welds. However, examination of Core Spray Pump casing Weld CP 206-CSP-W2 is limited by the adjacent concrete surrounding the area of required surface examination. In order for the licensee to obtain 100 percent of the ASME Code-required examination coverage for the subject weld, the pump and concrete vault
- 12 would have to be redesigned and modified, or the pump would require disassembly to access the weld from the inside diameter surface. These alternatives would place a burden on the licensee; therefore, the ASME Code examination requirements are impractical.
As shown on the sketches, photographs, and technical descriptions included in the licensee's submittal, examination of the subject weld could not be performed due to the pump's design, which places most of the casing weld within vertical concrete walls, making it nearly inaccessible from the outside surface. Only 23.4% of the required surface examination coverage was achieved using a PT method. No recordable indications were observed in the examined region of this weld.
As discussed above, it is impractical to meet the ASME Code-required examination coverage for the subject pump casing weld. However, based on the limited examination performed, and the VT-2 visual examinations that are conducted after each refueling outage, it is concluded that if significant service-induced degradation had occurred, there is reasonable assurance that evidence of it would have been detected by the examinations that were performed. As such, the NRC staff further concludes that the VT-2 visual examinations provide reasonable assurance of leak tightness of the subject pumps.
3.6 Request for Relief HC-12-RR-25 (Part F), ASME Code,Section XI, Examination Category R-A Item R1.20, Austenitic Piping Welds Governed by A Risk-Informed Program ASIVIE Code Requirement The examination requirements for the subject piping welds at HCGS are governed by a Risk-Informed Inservice Inspection (RI-ISI) program that was approved by the NRC in a safety evaluation dated February 3,2000 (ADAMS Accession No. ML003680090). The RI-ISI program was developed in accordance with Electric Power Research Institute (EPR!) Topical Report TR-112657, Rev. B-A, Revised RI-Inservice Inspection Evaluation Procedure (January 2000). As part of the NRC-approved program, the licensee has implemented inspection requirements listed in ASME Code Case N-578-1,5Risk-lnformed Requirements for ASME Code, Class 1, 2 or 3 Piping, Method B, with more detailed provisions contained in TR-112657. The topical report includes a provision for requesting relief from volumetric examinations if 100 percent of the required volumes cannot be examined.
Table 1 of ASME Code Case N-578-1 assigns the Examination Category R-A Item R1.20, to piping inspection elements not subject to a known damage mechanism.
This table requires 100 percent of the examination location volume, as described in Figures IWB-2500-8, 9, 10, or 11, as applicable, including an additional %-inch of base metal adjacent to the ASME Code volume, be completed for selected Class 1 circumferential piping welds. ASME Code Case N-460, as an alternative approved for use by the NRC in RG 1.147, Revision 15, states that a reduction in examination 5
ASME Code Case N-578 has not been approved for use in RG-1.147, Revision 15. Licensees base their RI-ISI inspection sample size and examination methodology on Table 1 of ASME Code Case N-578.
- 13 coverage due to part geometry or interference for any ASME Code Class 1 and 2 weld is acceptable provided that the reduction is less than 10 percent (i.e., greater than 90 percent examination coverage is obtained).
Licensee's ASME Code Relief Request In accordance with 10 CFR 50.55a(g)(5)(iii), the licensee has requested relief from the 100 percent volumetric examination coverage requirements contained in Table 1 of ASME Code Case N-578 for the ASME Code, Class 1 piping welds as shown below in Table 3.6.1.
R1.20 R1.20 R1.20 1-BB-4VCA-011-1-R1 1-BB-4VCA-012-1-R1 1-BG-6DBA-001-29 Branch connection-to-pipe Branch connection-to-pipe Pipe-to-valve 50.00%
50.00%
58.07%
Licensee Basis for Relief (as stated)
"[ASME] Code required coverage is impractical for the identified subject components due to weld-o-Iet configuration, pipe to flange configuration, valve taper configuration, and a weld crown condition. These issues limit the examination of the subject weld[s]."
'The required ASME Code coverage is impractical for the subject welds since the components would require design modifications that would impose a significant burden to PSEG."
Licensee's Proposed Alternative Examination (as stated)
"1\\10 alternative provisions are practical for the subject welds. Examinations were performed to the maximum extent practical with no reportable indications."
"Subject components have been subjected to a visual leakage examination after completion of each refueling outage. This provides additional assurance that the structural integrity of the subject components was maintained."
NRC Staff Evaluation
The examination requirements for the subject piping welds are governed by a RI-ISI program that was approved by the NRC in a safety evaluation dated February 3, 2000.
This program assigns Examination Category R-A, Item R1.20 to piping elements not subject to a known damage mechanism, and requires inspection of 100 percent of the examination location volume for ASME Code Class 1 circumferential piping welds.
However, valve taper, weld crown, and weld-o-Iet configurations on the subject piping welds limit volumetric examinations. In order to meet the RI-ISI program volumetric
- 14 coverage requirements, these components would have to be re-designed and modified which would cause a burden on the licensee. Therefore, 100 percent required volumetric examination is impractical for the subject welds.
The UT examinations on branch connection-to-piping Welds 1-BB-4VCA-011-1-R1 and 1-BB-4VCA-012-1-R1 were limited by the weld-o-Iet configuration, which prevented full scanning of the required volumes from both sides of the weld. These examinations were performed as pre-service examinations, following a repair during a forced outage.
Because these were preservice examinations, no other welds could have been substituted and examined instead. Downstream ultrasonic examinations were performed using shear wave techniques at 45 degree, 60 degree and 70 degree scan angles. No examinations were performed in the upstream direction due to the configuration of the branch connection. In addition, the UT examinations were supplemented by construction radiography. No recordable flaw indications were observed during these examinations.
As shown on the sketches and technical descriptions included in the licensee's submittal, examination of the subject welds has been performed to the extent practical using methods qualified through performance demonstration requirements of the ASME Code,Section XI, Appendix VIII.
For pipe-to-valve Weld 1-BG-60BA-001-29, UT VOlumetric examination was limited by the valve taper configuration and existing weld crown. A 45 degree shear wave was applied from the upstream (pipe side) of the weld. Other welds in the same risk segment as 1-BG-60BA-001-29 had already been selected for examination; therefore, no other welds with the same risk were available to supplement this limited examination. Based on the sketch 10 provided, no volumetric coverage could be obtained from the valve side of the weld. In addition, the weld crown also caused volumetric coverage limitations.
The methods used to perform the subject weld examinations were qualified through the POI requirements of ASME Code,Section XI, Appendix VIII. No recordable flaw indications were observed during these examinations.
As discussed above, it is impractical to meet the ASME Code-required examination coverage for the subject welds. However, based on the ultrasonic coverage obtained for the subject welds, and considering the licensee's performance of supplemental radiographic examinations (construction radiographs following repairs) for two of these welds, it is reasonable to conclude that if significant service-induced degradation had occurred, evidence of it would have been detected by the examinations that were performed. As such, the NRC staff further concludes that there is reasonable assurance of structural integrity of the subject welds based on the examinations that have been performed.
4.0 CONCLUSION
S The NRC staff, with technical assistance from its contractor, the PNNL, has reviewed the licensee's relief request and concludes that the ASME Code examination coverage requirements are impractical for the subject components. Furthermore, imposition of the ASME Code requirements would create a burden on the licensee. Based on the volumetric and/or surface coverage obtained, it is concluded that if significant service-induced degradation had occurred, there is reasonable assurance that evidence of it would have been detected by the examinations
- 15 that were performed. As such, the NRC staff further concludes that there is reasonable assurance of the structural integrity and/or leak tightness of the subject components based on the examinations that have been performed.
Granting relief request pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the public interest given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(g)(6)(i), and is in compliance with the ASME Code's requirements with the granting of this relief. Therefore, the NRC staff is granting PSEG's request for relief pursuant to 10 CFR 50.55a(g)(6)(i), for the second 10-year lSI interval at HCGS.
All other ASME Code,Section XI requirements for which relief was not specifically requested and approved remain applicable, including third-party review by the Authorized Nuclear lnservice Inspector.
Principal Contributors: T. McLellan C. Nove Date: November 19, 2009
ML093020466 OFFICE LPL1-2/PM LPL1-2/LA CVIB/BC CPNB/BC LPL1-2/BC NAME REnnis ABaxter MMitchell TChan HChernoff DATE 11/17/09 11/18/09 11/6109 11/9/09 11/19/09