ML060400445
| ML060400445 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 02/09/2006 |
| From: | Hartz L Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 06-057 | |
| Download: ML060400445 (13) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA23261 February 9 , 2006 United States Nuclear Regulatory Commission Serial No.06-057 Attention: Document Control Desk NLOS/GDM RO Washington, D.C. 20555 Docket No. 50-281 License No. DPR-37 VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNIT 2 ASME SECTION XI INSERVICE INSPECTION PROGRAM RELIEF REQUEST CMP-006 REVISION 1 REQUEST TO USE CODE CASE N-706 AS AN ALTERNATIVE In a letter dated August 25, 2003 (Serial No.03-428), Virginia Electric and Power Company (Dominion) submitted Relief Request CMP-006 for Surry Power Station Unit 2 pertaining to ASME Section XI Code required inspections on the Regenerative Heat Exchanger. In a subsequent letter to the NRC dated May 5, 2004 (Serial No.
03-428A), Dominion withdrew the subject relief request and noted our intent to resubmit the subject relief request at a later date.
Since that time the ASME Boiler and Pressure Vessel Code Committee approved Code Case N-706, "Alternative Requirements to Table IWB and IWC 2500-1 for PWR Stainless Steel Residual and Regenerative Heat ExchangersSection XI, Division 1 on,I1 October 11, 2005. Code Case N-706 is not yet listed in Regulatory Guide 1.147, "Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1." However, provisions stated in footnote 6 to 10 CFR 50.55a provide for the use of other Code Cases upon request, if approved by the Director of the Office of Nuclear Reactor Regulation pursuant to 10 CFR 50.55a(a)(3).
Dominion has reviewed the Code Case and the Westinghouse report "Technical Basis for Revision of Inspection Requirements for Regenerative and Residual Heat Exchangers" prepared at the request of the Westinghouse Owner's Group (WOG). The Westinghouse paper was written to support the elimination of surface and volumetric inspections of the Residual and Regenerative Heat Exchangers by approval of this Code Case. Dominion has verified the application of the Code Case and technical basis for Surry Unit 2 in Relief Request CMP-006, Revision 1. The relief request is provided in Attachment 1, and a copy of Code Case N-706 is provided in Attachment 2.
NRC approval of Relief Request CMP-006, Revision 1, is requested for the Surry Unit 2
Serial No.06-057 Docket 50-281 Page 2 Regenerative and Residual Heat Exchangers for the duration of the Fourth lnservice Inspection Interval pursuant to 10 CFR 50.55a(a)(3)(i).
If you have any questions or require additional information, please contact Mr. Gary D.
Miller at (804) 273-2771.
Very truly yours, Leslie N. Hartz Vice President - Nuclear Engineering Attachments Commitments made by this letter: None cc: U. S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303 Mr. S. R. Monarque U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 8H12 Rockville, MD 20852 Mr. N. P. Garrett NRC Senior Resident Inspector Surry Power Station Mr. R. A. Smith Authorized Nuclear Inspector Surry Power Station
Serial No.06-057 Docket No. 50-281 Attachment 1 Relief Request CMP-006, Revision 1 Virginia Electric and Power Company (Dominion)
Surry Power Station Unit 2
Serial No.06-057 Docket 50-281 Attachment 1 RELIEF REQUEST CMP-006. REVISION 1 SURRY POWER STATION UNIT 2
- 1. IDENTIFICATION OF COMPONENTS Various welds on the Residual (2-RH-E-1A and 2-RH-E-1B) and Regenerative Heat Exchangers (2-CH-E-3). The welds are:
2-RH-E-1A Welds DescriDtion Cateaorv/ltem -
Class 1-A01 Head Circumferential Weld c-NC1.20 2 1-A02 She II Ci rcumferential Weld C-A/Cl. 10 2 1-A05, 1-A06, Reinforcing Plate Welds to C-BK2.3 1 2 1-AO7, I-A08 Nozzle and Vessel 2-RH-E-1 B Welds DescriPtion Cateaorv/ltem -
Class 1-B01 Head Circumferential Weld c-NC1 .20 2 1-B02 Shell Circumferential Weld c-NC1.10 2 1-805, 1-B06, Reinforcing Plate Welds to C-BE2.3 1 2 1-B07,1-B08 Nozzle and Vessel 1
Serial No.06-057 Docket 50-281 Attachment 1 2-CH-E-3 Welds Descrbtion CateaorWltem -
Class 1-04, 1-17, Circumferential Head Welds B-B/B2.51 1
& 1-19 1-03, 1-18, Tubesheet-to-Shell Welds 8-B/B2.80 1
& 1-22 1-06, 1-08, Nozzle-to-Vessel Welds B-D/B3.150 1 1-09, 1-11, 1-13, & 1-15 NIR-06, NIR-08, Nozzle Inside Radius Section B-DlB3.160 1 NIR-09, NIR-11, NIR-13, & NIR-15 I-01,1-21, Head Circumferential Welds c-NC1.20
& 1-24 1-02, 1-20, Tubesheet-to-Shell Welds C-NC1.30
& 1-23 II. APPLICABLE CODE EDITION AND ADDENDA Surry Unit 2 is currently in the Fourth lnservice Inspection Interval under the 1998 Edition through the 2000 Addenda of the ASME Section XI Code.
111. CODE REQUIREMENTS Examination Categories B-B and B-D from Table IWB-2500-1 and C-A and C-B from Table IWC-2500-1 require that volumetric or surface examinations be performed on the welds and nozzle inside radius areas listed above.
IV. BASIS FOR RELIEF The subject welds are shown in Figures 1, 2 and 3 for stainless steel components 2-RH-E-1A, 2-RH-E-1B and 2-CH-E-3, respectively.
The regenerative heat exchanger (2-CH-E-3) provides preheat for the normal charging water flowing into the reactor coolant system (RCS). The residual heat exchangers are designed to cool the RCS during plant shut down operations.
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Serial No.06-057 Docket 50-281 Attachment 1 On October 11, 2005, the ASME Boiler and Pressure Vessel Standards Committee approved Code Case N-706, "Alternative Examination Requirements of Table IWB-2500-1 and Table IWC-2500-1 for PWR Stainless Steel Residual and Regenerative Heat Exchanger Section XI, Division 1 (Attachment 2).
Westinghouse provided the technical justification for the Code Case for eliminating the surface and volumetric inspections of the Residual and Regenerative Heat Exchangers under the Westinghouse Owner's Group (WOG) project, "Technical Basis for Revision of Inspection Requirements for Regenerative and Residual Heat Exchangers", August, 2004. The components at Surry Power Station are typical of the heat exchangers described in the Westing house report by fabrication, geometric design, inspection requirements and geometric restrictions.
As stated in the Westinghouse report, these components were designed and installed before the imposition of the inservice inspection requirements by ASME Section XI and are not designed for conducive performance of ultrasonic and surface examination. The small diameter of the vessel and nozzles of the Regenerative Heat Exchanger makes a meaningful ultrasonic examination very time consuming and dose intensive. The physical limitations would substantially diminish the ability to discriminate flaw indications from geometry existing around the joint. Regarding the Residual Heat Exchangers, interference with the lower support and interference with inlet and outlet pipes would permit only partial coverage for examination of the head and shell circumferential welds.
Furthermore, these components are located in high radiation fields. The estimated personnel dose to perform interval Code inspections on the Regenerative Heat Exchanger is 12.0 man-rem. It is estimated that 4.5 man-rem would be required to meet the inspection requirements per interval for the Residual Heat Removal Heat Exchanger. In view of the dose expended for limited examination providing questionable results, the value of performing the Code required exams is minimal.
Two other factors presented in the Westinghouse report for these components were considered by the ASME committee: flaw tolerance and risk assessment.
Fracture evaluations were performed for the components using finite element models and fracture calculations. It was concluded that the heat exchangers have a large flaw tolerance and that significant leakage would be expected long before any failure occurred. Fatigue crack growth was determined to be extremely slow even in the most highly stressed region. Thus, detailed inspections are not required to ensure heat exchanger integrity.
A risk evaluation was performed using the accepted methodology applied for Risk Informed IS1 piping inspection programs. The following conclusions were made:
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Serial No.06-057 Docket 50-281 Attachment 1 Safety equipment required to respond to the potential event is unaffected.
Potential for loss of pressure boundary integrity is negligible.
No safety analysis margins are changed.
0 Leakage before full break is expected (no core damage consequences associated with leakage).
Consequently, elimination of the subject inspections would not be expected to result in a significant increase in risk.
There have been no through-wall leaks on these components or components of similar design as reported in industry and as discussed in the Westinghouse report. The only related leak in the United States occurred in January 2004 at San Onofre Unit 3 on the letdown line exiting the Regenerative Heat Exchanger.
This failure was caused by excessive vibration on the piping line and is not an indication of failure on the actual heat exchanger.
V. PROPOSED ALTERNATIVE In accordance with the provisions of 10CFR50.55a(a)(3)(i), approval is requested to use Code Case N-706 as an alternative to the requirements in Table IWB 2500-1 for Categories B-B and B-D pertaining to the Regenerative Heat Exchanger and Table IWC 2500-1 for Categories C-A and C-B pertaining to the Residual and Regenerative Heat Exchangers. Specifically, a VT-2 examination will be performed as an acceptable alternative to the Code required examination.
VI. DURATION OF PROPOSED ALTERNATIVE The use of Code Case N-706 is requested for the duration of the Surry Unit 2 Fourth Inservice Inspection Interval or until the NRC publishes the Code Case for acceptable use in a future revision of Regulatory Guide 1.147.
VII. PRECEDENTS Similar requests for relief were submitted and approved before this Code Case was approved by the ASME Section XI committee including Joseph M. Farley under TAC No. MA3449; North Anna Power Station Unit 2 under TAC No.
MB07050; Surry Power Station Unit 1 for the third inservice inspection interval under TAC No. MB1998 and Surry Power Station Unit 2 for the third inservice inspection interval under TAC No. MB1999.
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Serial No.06-057 Docket 50-281 Attachment 1 REGENERATIVE HEAT EXCHANGER L6 x 6 I 3/1'
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TUBE SIDE OUlLEll ELEVATION LOOKING WEST SECTION '6' SECTION 'A' Figure 3 Regenerative Heat Exchanger 7
Serial No.06-057 Docket 50-281 Attachment 2 ATTACHMENT 2 Code Case N-706 Alternative Examination Requirements of Table IWB-2500-1 and Table IWC-2500-1 for PWR Stainless Steel Residual and Regenerative Heat Exchanger Section XI, Division 1 Virginia Electric and Power Company (Dominion)
Surry Power Station Unit 2
Gal IX 0402H706 10-17-0509:0646 Case number: N-706 FOO~W SUPP. 7 - NC (Status: ON)
PDF Footer: PDF RELEASE (Status: ON)
Approval Drt.: Octobor 11,2005 The ASME Boiler end Pressure Ueswl Standards Committee took ection to eliminate Code Case expiration dams e W v e Mamh 11,2005. W s means that all Code Cases listed in this Supplement and beyond w.11 remain available for use until annulled by the ASME Boiler and Pressure btwsel Stand8ds Committee.
Cast N-706 Alternative Examination Requirements of Table IWB-2500-1and Table TWC-2500-1for PWR Stain-less Steel Residual and RegenerativeHeat Exchanger Section X I , Division 1 Inquiry: What alternative to the requirements ofTable IWB-2500.1, ExaminationCategoriesB-B, B-D, and B-J.
and Table WC-2500-1, Examination Categories C-A.
C-B, and C-F-1, ITBY be used for PWR stainl~sssteel mgenerative and residual heat exchangers?
Reply: It is the opinion of the Committee that the requirements of Table 1 m a y be used for PWR stainless steel =generative and residual heat exchangers, in lieu of the requirements of Table IWB-2500-1,Examination Categories B-B, B-D,and B-J, and Table WC-2500-1, Examination Categories C-A, C-B, and C-P1.
This Case may not be applied to any heat exchanger nor to any heat exchangerdesign or configuration that has experienceda through-wallleak, such as h a t exchangers with an inner shell (inner barnl). The Owner shall evalu-ate industry experience to determine which heat exchanger designs or configurations have leaked. If any leakage is b t e d , it shall be comctbd in accordance with IWA-4000 or (IWA-7000prior to the 1991 Addenda). Use of this Casc shall be discontinuedfor that heat exchanger designor configuration. The affected heat exchanger and others of the same design or configuration shall be examined in accordance with LWB-2500or WC-2500,as applicable.
Gal IX 000402H76A 10-17-05 1018:21 TABLE 1 PRESSURE RETAINING WELDS I N PWR STAINLESS STEEL RESIDUAL AND REGENERATIVE HEAT EXCHANGERS Extent and Frequency of Examination Deferral of Item Acceptance Fitst Inspection Successive Inspection to No. Parts Examined Examination Method Standard Intmal I ~ O n I ~ S End of Interval 1.10 Resldual and Rcgencrattve Heat ExchangersL2 1.11 Category 8-8 welds' VT-2 IWB-3522 Ail mlds Same as for 1st interval Not permissible 1.12 Category 8-0w e l d VT-2 I W 8-3522 All welds Same as for 1st interval Not permissible 1.13 Category B J welds' VT-2 IWB-3522 All welds S a m a for 1st Interval Not permissible 1.14 Category C-A mi&' VT-2 IWB-3516 All welds Same as for 1st interval N o t permissible 1.15 Category C-B welds' VT-2 IWB-3516 All welds Same as for 1st interval N o t permissible 1.16 Category C-F-1 welds' VT-2 IWB-3516 All welds Same as for 1st interval Not permissible NOTES:
(1) Applicaion of the mqulrements of this table Is limited to those welds that are part of the as-meived heat exchanger mrnbly. The regenerative heat exchanger assembly may be formd from multlpk smaller heat exchanger sukomponewts connected by KcUona of piping. All of the smaller heat exchanger subcomponents and the connecting piping am wlthln the boundary of the heat exchanger assembly.
(2) All welds shall have received at kast one volunetric examination; the prrscrvke or Construction Code voiumetrlc exarnlnatlon may be ured to meet thls requirement (3) Component shall k examined for evidence of leakage while undergoing the system leakage test (IWB-5220) as required by Examination Category B-P, to k performed every refueling Outage.
(4) Component shall k examinedfor evidence of leakagewhik undergoing the system leakagetest (1WC6220) as required by Examination Category C-H, to be performed every inspcctlonperiod.