ML18235A316
| ML18235A316 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 08/17/2018 |
| From: | Mark D. Sartain Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 18-160 | |
| Download: ML18235A316 (9) | |
Text
10 CFR 50.55a VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 August 17, 2018 United States Nuclear Regulatory Commission Serial No.18-160 Attention: Document Control Desk NRNDEA RO Washington, D.C. 20555 Docket Nos. 50-338 50-339 License Nos. NPF-4 NPF-7 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION ENERGY VIRGINIA)
NORTH ANNA POWER STATION UNITS 1 AND 2 ASME SECTION XI INSERVICE INSPECTION PROGRAM RELIEF REQUESTS N1-15-NDE-001 AND N2-15-NDE-001 PROPOSED ALTERNATIVE - PZR SURGE LINE VT-2 EXAM IN PLACE OF UT EXAM In accordance with 10 CFR 50.55a(z)(2), Dominion Energy Virginia hereby requests Nuclear Regulatory Commission (NRC) approval of proposed inservice inspection (ISi) relief requests N1-15-NDE-001 and N2-15-NDE-001 for North Anna Units 1 and 2. The request is for a proposed alternative to allow the pressurizer surge line nozzle-to-vessel (weld and nozzle inner radius) to be examined as part of the normally scheduled Class 1 system leakage test during each refueling outage (ASME Code VT-2). The request for alternative is provided in Attachment 1.
Approval of the proposed alternative is requested by September 1, 2019 to support the Unit 1 2019 Fall outage. If you have any questions, please contact Ms. Diane E. Aitken at (804) 273-2694.
Sincerely,
~-
Mark Sartain Vice President - Nuclear Engineering and Fleet Support
Attachment:
- 1. Relief Requests N1-15-NDE-001 and N2-15-NDE-001 for Proposed Alternative -
Pressurizer Surge Line Visual VT-2 Examination in Place of UT Examinations This letter contains no NRC commitments.
Serial No.18-160 Docket Nos.: 50-338, 50-339 RR N1-15-NDE-001 and N2-15-NDE-001 Proposed Alternative Page 2 of 2 cc: U.S. Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, Georgia 30303-1257 Mr. Marcus Harris Old Dominion Electric Cooperative Innsbrook Corporate Center 4201 Dominion Blvd.
Suite 300 Glen Allen, Virginia 23060 Mr. James R. Hall NRC Senior Project Manager U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 B1-A 11555 Rockville Pike Rockville, Maryland 20852 Ms. K. R. Cotton NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 G-9A 11555 Rockville Pike Rockville, Maryland ,20852-2738 NRC Senior Resident Inspector North Anna Power Station
Serial No.18-160 Pressurizer Surge Nozzle Page 1 of 7 ATTACHMENT 1 RELIEF REQUESTS N1-15-NDE-001 and N2-15-NDE-001 PROPOSED ALTERNATIVE PRESSURIZER SURGE LINE VISUAL VT-2 EXAMINATION IN PLACE OF UT EXAMINATIONS VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION ENERGY VIRGINIA)
NORTH ANNA POWER STATION UNIT 1 AND UNIT 2
Serial No.18-160 Docket Nos. 50-338 and 50-339 Pressurizer Surge Nozzle Attachment 1, Page 2 of 7 RELIEF REQUESTS N1-15-NDE-001 and N2-15-NDE-001 Proposed Alternative in Accordance with 10 CFR 50. 55a(z)(2)
-- Hardship without a Compensating Increase in Quality and Safety --
1.0 ASME CODE COMPONENTS AFFECTED Pressurizer (1-RC-E-2 and 2-RC-E-2) nozzle-to-vessel welds 9 and nozzle inner radius sections 9NIR (see Figures 1 and 2).
2.0 APPLICABLE CODE EDITION AND ADDENDA The ASME Boiler and Pressure Vessel Code (ASME Code)Section XI of record for the North Anna Power Station Units 1 and 2 fifth inspection intervals is the 2013 Edition.
3.0 APPLICABLE CODE REQUIRMENTS The 2013 Edition of ASME Code,Section XI, Table IWB-2500-1, Category B-D, Item B3.110, requires a volumetric examination of pressurizer surge line nozzle-to-vessel Weld 9. The 2013 Edition of Section XI does not require an examination of the nozzle-inside-radius of Weld 9 (9NIR). However, 10 CFR 50.55a(b)(2)(xxi) mandates use of the 1998 Edition of Section XI for the examination requirements of 9NIR. Category B-D, Item B3.120 of the 1998 Edition requires a volumetric examination of the nozzle inside radius section of the pressurizer surge nozzle. 10 CFR 50.55a(b)(2)(xxi) allows an enhanced visual VT-1 on the inside surface in lieu of the volumetric requirement, which is performed from the outside surface.
4.0 REASON FOR REQUEST
- Access to the North Anna Power Station (NAPS) Units 1 and 2 pr~ssurizer surge line nozzles is obstructed by multi-layered, stainless steel mirror insulation and the cables for the pressurizer heaters. Removal of the insulation and cables would be difficult as well as labor and time intensive. It is also likely that cable or heater pin damage could occur during removal. The pressurizer surge line nozzle is integrally cast into the bottom head of the pressurizer, is located under the pressurizer skirt, and is surrounded by 78 heater penetrations.
Some, and possibly all, heater cables would have to be disconnected so that the cables can be pulled back to allow access for removing insulation and doing the exam. Dose rates are predicted using a step approach to build the total projected E;lxposure. The worst case option assumes that all 78 heater cables
Serial No.18-160 Docket Nos. 50-338 and 50-339 Pressurizer Surge Nozzle Attachment 1, Page 3 of 7 have to be disconnected and pulled back. These cables have brazed connections that will be time consuming to remove and replace following the exam. This option carries a dose estimate of 54.320 rem. If the outer ring of heaters can be left intact during the examination (disconnect/reconnect 46 heaters), then the dose estimate is 34.144 rem. If only the first ring of heaters is disconnected/reconnected (20 heaters), then the dose estimate is 17.751 rem.
Even if all the cables are removed, examination coverage would still be limited due to the weld joint design and heater penetration interferences.
C Other personnel safety concerns potentially involved in this examination include the increased risk of an unplanned exposure event and the potential for contamination of personnel wedged between the surge line and the exposed portion of the pressurizer heaters. Temporary shielding is considered impractical because placement of the shielding material would obstruct and potentially preclude accessibility to the examination surface.
In conjunction with license renewal, Westinghouse has performed an evaluation to address the impact of operational transients for NAPS 1 and 2 to account for insurge/outsurge transients in addition to design transients in the pressurizer lower head (Reference 8.1 ). The results of the evaluation show that the Cumulative Usage Factor (CUF), after service equivalent to 60 years of operation for the lower head to nozzle weld (the subject weld), is 0.32 for the inside surface and 0.07 for the outside surface. The CUFs for the nozzle inner radius are 0.25 (inside surface) and 0.09 (outside surface). These CUFs are considerably less than the design limit of 1.0 and provide insight into the potential for failure in this area. Additionally, Dominion is unaware of an industry failure involving the inside radius section of the surge-line nozzle in a Westinghouse design pressurizer.
The alternative visual VT-1 examination on the inside of the pressurizer nozzle to vessel weld cannot be performed without great difficulty and risk. The pressurizer manway at the top of the vessel would have to be removed and a boroscope threaded down the length of the pressurizer through the support plates and through a screen device located at the outlet of the surge line near the bottom of the vessel. The examination would be partially obscured by the thermal sleeves and the examination would only be of the non-structural cladding covering the welds. If performed, the examination would provide only marginal benefit. The added radiological exposure, the risk of foreign material intrusion into the reactor coolant system and the unusual difficulties associated with attempting this examination are not commensurate with the limited benefit that may be obtained.
Due to the fact that compliance with the specified requirements would result in hardship or unusual difficulties without a compensating increase in the level of quality and safety, an alternative is requested.
Serial No.18-160 Docket Nos. 50-338 and 50-339 Pressurizer Surge Nozzle Attachment 1, Page 4 of 7 5.0 PROPOSED ALTERNATIVES AND BASIS FOR USE Per 10 CFR 50.55a(z)(2) Dominion is applying for the following alternative:
The pressurizer surge line nozzle-to-vessel (weld and nozzle inner radius) will be examined as part of the normally scheduled Class 1 system leakage test during each refueling outage(ASME Code VT-2). In addition, the surveillance requirements of Technical Specifications that determine the reactor coolant system leak rate and the containment atmosphere radioactivity will be satisfied.
The pressurizer surge line weld to the reactor coolant hot leg will also be examined as part of augmented inspections to detect environmentally affected fatigue (EAF) and will be used as the leading indicator of EAF. The inspection of the pressurizer surge line connection to the hot leg piping is a commitment for license renewal aging management implementation at North Anna Power Station (Reference 8.2).
A search of operating experience (OE) involving degradation at the inside radius section of the surge line nozzle in a Westinghouse designed pressurizer was conducted using the Institute of Nuclear Power Operators (INPO) website and among industry experts. The OE identified no known indications for pressurizer nozzle inside radius sections for any reactor or steam generator nozzle NIRs at Pressurized Water Reactor plants of any type.
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Furthermore, Dominion has an active Boric Acid Corrosion Control Program that identifies and monitors borated water leakage to identify and evaluate boric acid related degradation of the Reactor Coolant System. These programs ensure that the overall level of plant quality and safety will not be compromised.
6.0 DURATION OF PROPOSED ALTERNATIVE The proposed alternative to the ASME Code is applicable for the duration of the fifth 10-year inservice inspection (ISi) intervals at NAPS Unit 1 (May 1, 2019 -
April 30, 2029) and Unit 2 (December 14, 2020 - December 13, 2030).
7.0 PRECEDENTS 7.1 An NRG letter dated December 11, 2011 granted relief for the same component on North Anna Power Station Unit 1, Relief Request N1-14-NDE-003-R1 (ADAMS# ML11320A122) 7.2 An NRG letter dated October 6, 2010 granted relief for the same component on North Anna Power Station Unit 2, Relief Request N2-14-NDE-001 (TAC No. ME3292).
Serial No.18-160 Docket Nos. 50-338 and 50-339 Pressurizer Surge Nozzle Attachment 1, Page 5 of 7 7 .3 An NRC letter dated February 18, 2005 granted similar relief for the fourth ten-year inservice inspection interval for Kewaunee Power Station.
7.4 Similar relief was granted for North Anna Power Station Unit 1 during the second and third inservice inspection intervals (TAC Nos. M71066 and MA5750, respectively) and for North Anna Power Station Unit 2 for the second and third inservice inspection intervals (TAG Nos. M79147 and MB2280, respectively).
7.5 Similar relief was granted for Surry Power Station Units 1 and 2 for the third inservice inspection intervals (TAC Nos. M87312 and M89085, respectively),
and for the fourth inspection interval (TAC Nos. MD3673 and MD3674).
7.6 Byron Station Units 1 and 2 were granted relief for the second inservice inspection intervals (TAC Nos. M94830 and M94831 respectively).
7.7 Haddam Ne.ck Plant was granted relief for the third inservice inspection interval (TAC No. M80457).
7..8 Beaver Valley Power Station was granted relief for the third inservice inspection interval in an NRC letter dated October 8, 1997.
8.0 REFERENCES
8.1 WCAP-15607, "Evaluation of Pressurizer lnsurge/Outsurge Transients for Surry and North Anna," December 2000.
8.2 NAPS Updated Final Safety Analysis Report, Section 18.2.1, Augmented Inspection Activities.
Serial No.18-160 Docket Nos. 50-338 and 50-339 Pressurizer Surge Nozzle Attachment 1, Page 6 of 7 RELIEF REQUESTS N1-15-NDE-001 AND N2-15-NDE-001 CONTINUED FIGURE 1 Vessel Penetration Power Relief and _,,/' Nozzle for Spray Line Safety Valve Nozzles"'-
Manway Instrument Nozzles Upper Support Bracket Angle Iron r..-- Insulation Bands Lifting Trunnion Top View Operating Water Level Seismic Lug 78 Heater Elements Heater Support ------>t::::J Baffles Bottom View Instrument Nozzles -----_,__,__.
Circular Support Skirt Surge Basket Thermal Nozzle Diffuser Sleeve Graphics No. C81671A PRESSURIZER
Serial No.18-160 Docket Nos. 50-338 and 50-339 Pressurizer Surge Nozzle Attachment 1, Page 7 of 7 RELIEF REQUESTS N1-15-NDE-001 AND N2-15-NDE-001 CONTINUED FIGURE 2 STAINLESS STEEL PIPE STAINLESS STEEL WELD-SAFE ENO FORGING PIPE TO SAFE-END SA-182 F316L WELD OVERLAY WELD OVERLAY --.,11a---INCONEL NOZZLE TO SAFE-END WELD
[NCONEL WELD BUILD-UP
- --* .1':r CLADDING SURGE NOZZLE