ML20217E413
| ML20217E413 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 09/24/1997 |
| From: | Edison G NRC (Affiliation Not Assigned) |
| To: | Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| References | |
| GL-90-05, GL-90-5, TAC-M99426, NUDOCS 9710070015 | |
| Download: ML20217E413 (3) | |
Text
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- 4 UNITED STATES s
j NUCLEAR REGULATORY COMMISSION WASHINGTON. D.C. 30eeH001 8
.....,o September 24, 1997 Mr. J. P. O'Hanlon Senior Vice President - Nuclear Virginia Electric and Power Company 5000 Dominion Blvd.
Glen Allen. Virginia 23060
SUBJECT:
NORTH ANNA POWER STATION UNIT 1 - ASME SECTION XI RELIEF REQUEST NDE SERVICE WATER SYSTEM (SWS) LEAKS (TAC NO. M99426)
Dear Mr. O'Hanlon:
The NRC staff has evaluated the information provided in your August 8,1997, submittal. related to the inservice inspection program relief request NDE-42.
Based on the evaluation of relief request NDE-42, it is concluded the repair would have necessitated removing portions of the SWS that are otherwise structurally sound and capable of performing their intended safety function.
This would have unnecessarily reduced the margin of safety of the SWS.
Therefore, the immediate Code repair during the period June 25, 1997, through July 9. 1997, would have constituted an undue burden on Virginia Electric and Power Company (VEPCO).
Your alternative program for this period included evaluation of the flaws which is consistent with the guidelines and acceptance criteria of Generic letter (GL) 90-05. The staff finds the structural integrity and operability assessments to be acceptable. You have stated that during the period of June 25 through July 9. 1997, the welds were monitored by plant personnel and all the flaws were repaired by July 9.1997.
In addition, you had evaluated the defective areas and determined that the flaws were acceptable and the SWS was determined to be operable.
While the impracticality of the Code requirements was not shown, the staff finds that relief may be granted pursuant to 10 CFR 50.55a(a)(3)(ii).
The staff's evaluation and conclusions are contained in the Enclosure.
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-2 The staff has completed its evaluation of this matter and we are, therefore.
closing out TAC No, M99426.
Sincerely.
(Original Signed By)
Gordon E. Edison, Acting Director Project Directorate II-1 Division of Reactor Projects I/II Office of Nuclear Reactor Regulation Docket No. 50-338
Enclosure:
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Mr. J. P. O'Hanlon North Anna Power Station
- Virginia Electric & Power Company Units 1 and 2-cc:
Mr. J. Jeffrey Lunsford County Administrator Regional Administrator. Region 11 Louisa' County U.S. Nuclear Regulatory Commission P.O. Box 160-Atlanta Federal Center Louisa. Virginia 23093 61 Forsyth St., SW. Suite 23T85 Atlanta Georgia 30303 Michael W. Maupin. Esquire Hunton and Williams Mr. W. R. Matthews Manager Riverfront Plaza. East Tower North Anna Power Station 951 E. Byrd Street-P. O. Box 402 Richmond Virginia 23219 Mineral. Virginia 23117 Dr. W. T. Lough-Mr. Al Belisle Virginia State Corporation' U.S. Nuclear Regulatory Commission Comission Atlanta Federal Center Division of Energy Regulation 61 Forsyth St.
SW. Suite 23T85 P. O. Box 1197 Atlanta, Georgia 30303 Richmond ' Virginia 23209 l
Mr. David Christian, Manager Old Dominion Electric Cooperative Surry Power Station 4201 Dominion Blvd.
Virginia Electric and Power Company
-Glen Allen. Virginia 23060 5570 Hog Island Road Surry Virginia 23883
-Mr.-J.-H. McCarthy Manager
' Nuclear Licensing & Operations Support Virginia Electric and Power Company Innsbrook Technical Center 5000 Dominion Blvd.
4 Glen Allen. Virginia-23060 Office of the Attorney General Commonwealth of Virginia 900 East Main Street Richmond, Virginia 23219 Senior Resident Inspector North Anna Power Station U.S. Nuclear Regulatory Commission 1024 Hale Mineral. y Drive Virginia 23117-Robert B. Strobe. M.D., M.P.H.
State Health Comissioner Office of the Commissioner Virginia Department of Health P.O. Box 2448 Richmond Virginia 23218 l
- [pn:g *4 UNITED STATES g
j NUCLEAR REGULATORY COMMISSION
%..... /g WASHINGTON, D.C. 3004H001 g
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REOUEST FOR APPROVAL TO REPAIR FLAWS IN ACCORDANCE WITH GENERIC LETTER 90-05 FOR ASME CODE CLASS 3 SERVICE WATER PIPING VIRGINTA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION. UNIT 1 DOCKET NO. 50 338
1.0 INTRODUCTION
10 CFR 50.55a(g) requires nuclear power facility piping and components to meet the applicable requirements of Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (hereafter referred to as the Code).
Section XI of the Code specifies Code-acceptable repair methods for flaws that exceed Code acceptance limits in piping that is in-service. A Code repair is required to restare the structural integrity of flawed Code piping, independerd, of the operational mode of the plant when the flaw is detected. Those repairs not in compliance with Section XI of the Code are non-Code repairs.
However, the implementation of required Code (weld) repairs to ASME Code Class 1. 2 or 3 systems is often impractical for nuclear licensees since the repairs normally require an isolation of the system requiring the repair. and often a shutdown of the nuclear power plant.
Alternatives to Code requirements may be used by nuclear licensees when authorized by the Director of the Office of Nuclear Reactor Regulation if the proposed altematives to the requirements are such that they are shown to provide an acceptable level of quality and safety in lieu of the Code requirements [10 CFR 50 55a(a)(3)(1)]. or if compliance with the Code requirements would resuu. in hardship or unusual difficulty without a compensating increase in the level of quality and safety [10 CFR 50.55a(a)(3)(ii)].
A licensee may also submit recuests for relief from certain Code requirements when a licensee has determinec that conformance with certain Code requirements is imaractical for its facility [10 CFR 50.55a(g)(5)(iii)].
Pursuant to 10 CFR 50.55a(g)(6)(i). the Commission will evaluate determinations of impracticality and may grant relief and may impose alternative requirements as it determines are authorized by law.
Generic Letter (GL) 90-05. " Guidance for Performing Temporary Non-Code Repair of ASME Code Class 1. 2 and 3 Piping." dated June 15. 1990, provides guidance for the staff in evaluating relief requests submitted by licensees for temporary non-Code repairs of Code Class 3 aiping.
The staff uses the guidance in GL 90-05 as its criteria for macing its safety evaluation of relief requests for temporary non-Code repairs of Code Class 3 piping.
ENCLOSURE De o 6YjlvuNo M N &ff
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2.0 BACKGROUND
On June 25, 1997, at the North Anna Power Station. Unit 1. Virginia' Electric
-and Power Com)any (hereafter referred to as the licensee) identified four locations wit 1 evidence of possible previous leakage. i.e., stains in three ASME Class 3 service water system (S4S) lines. A repair plan was developed and implemented for the affected lines..The four welds were repaired in-accordance with the ASME Code requirements b August 8. 1997, pursuant to 10 CFR 50.55a(g)y July 9. 1997.
By letter dated (6)(1). the licensee requested a relief from the ASME Code.Section XI re through July 9.1997. placement requirements for the period of June 25, 1997 The licensee based its request for relief on the results of a "through wall flaw" evaluation that was performed by the licensee in accordance with the guidelines and acceptance criteria contained in GL 90-05.
3.1 LICENSEE'S RELIEF REOUEST l
3.1 Comoonents for Which Relief is Reauested Weld #
line #
Joint Tvoe 9W 2"-WS-84-163-03 Socket Weld 16W 4"-WS-46-163-03 Butt Weld 84 4"-WS-57-163 03 Butt Weld 19W 3" WS-75-163-03
. Butt Weld The above listed welds are ASME Code Class 3. moderate energy piaing in the SWS. The 4"-WS46-163 03 provides cooling water to the Unit 1 clarging pump lube oil coolers and instrument air compressors. Line 2"-WS-84-163-03 is the return from the 1-IA-E-1A heat exchanger.
Line 4"-WS-57-163-03-is the return from the instrument air compressors and charging pump lube oil coolers.
Line 3"-WS-75-163-03 is the return from the charging pump lube oil coolers.
The nominal operating pressure is 75 psig and operating temperature is 95 F.
3.2 Section XI-Edition for North Anna 1 1983 Edition of the ASME Code.Section XI including Summer 1983 Addenda.
3.3 ASME Section XI Code Reauirement The ASME Code Section XI requires that repairs or replacements of ASME Code Class components be performed in accordance with rules found in Articles IWA-4000 or 14A-7000, respectively. The intent of these rules serves to provide an acceptable means of restoring the structural integrity of a degraded Code Class system back to the original design requirements.
3.4 Content of the Relief Reauest Relief is sought from performing a repair or replacement of the service water piping per the requirements of Article IWA-4000 or IWA-7000, respectively.
Relief is being sought for the period of June 25, 1997, through July 9. 1997.
because performing'a Code repair during that period was determined to be not 9
3 practical. The licensee had accomplished permanent Code repairs for all welds by the end of that period, 3.5 Basis for Relief Request for relief has been submitted and alternatives to the Code requirements have been proposed by the licensee.
The NRC staff reviewed the proposed alternatives for compliance with the arovisions of 10 CFR 50 55a(g)(6)(1). The licensee has evaluated tie flaws in accordance with the-guidance provided in GL 90-05.
Based upon the evaluation, it was established that the discovered flaws satisfy the criteria for non-code repair as-described in GL 90-05 and performing ASME Code during the >eriod June 25. permanent re> airs in accordance with the 1997, througl July 9. 1997, would have constituted an undue Jurden (create undue hardship) upon the licensee since the repairs would have necessitated the unnecessary isolation of portions of i
l SWS that are structurally sound and thus reduce the margin of safety.
3.6 Licensee's Alternative Proaram During the period of June 25. 1997, through July 9, 1997, the SWS $ th the identified possible through-wall flaws was monitored by the licensee as follows.
1.
Weekly visual monitoring of through-wall flaws and leakage.
2.
Radiographic examination of butt welds.
4.0 STAFF EVALUATION AND CONCLUSIONS 4.1 Ooerability Determination. Root Cause Analysis and Structural Intecrity Evaluation The licensee determined that two locations _on_the SWS have a "through-wall flaw" and analyzed them in accordance with the position stated in GL 90-05.
This system was constructed in accordance with the requirements of ASME Code, i
Class 3.
Based on.the radiographic testing (RT) examination data, the flaws were determined to be small voids surrounded by exfoliation, which is typical of microbiologically induced corrosion (MIC).
No other type of operationally caused defects were identified by the RT. The licensee evaluated the structural integrity of the welds based on the radiographic examination and determined the following:
(1) butt weld 16W on line 4"-WS-46-163-03 and 19W on line 3"-WS-75-163-03 were analyzed and found to be acceptable: (2) the butt weld 84 on line 4"-WS-57-163-03 did not meet the assessment requirements of GL 90-05 and the line was-removed from service and the weld was replaced on July
- 3. 1997: (3) radiography of socket weld 9W on line 2"-WS-84-163-03 was not done since radiographs of socket welds do not yield meaningful results. The line was removed from service and the weld was replaced 2 days after the
. evidence of leakage was detected.
4.2 Auomented Insoection To assess the overall degradation of the SWS. augmented radiographic
f I
4
-examination was yerformed on five additional locations on lines having the same function.
our of the five welds had evidence of MIC but showed no evidence of through-wall leakage. The fifth weld which did not show evidence of MIC was on a reducer on the opposite side of a weld containing MIC. Any indication was treated as a through-wall defect and analyzed for structural integrity in accordance with the guidance provided in GL 90-05. All augmented weld locations were found to be structurally acceptable. However, all five welds selected for augmented inspection were replaced.
4.3 ff_02psed Temocrary Non-Code Reoair and Monitorino Provisions During the period June 25. 1997, through July 9, 1997, the licensee performed weekly visual monitoring of all areas with possible evidence of leakage.
The areas met the criteria for flooding and spraying consequences for structural integrity.
4.4 Staff Conclusions The staff has determined that the licensee's flaw evaluation has been consistent with the guidelines and acceptance criteria of GL 90-05. The staff therefore finds the licensee's structural integrity and operability assessments to be acceptable. During the period of June 25, 1997, through July 9,1997, the welds were monitored by plant personnel and the flaws were repaired by July 9, 1997.
Furthermore, the staff finds that performance of an immediate Code repair during the period June 25, 1997 through July 9. 1997, would have resulted in hardship without a compensating increase in the level of quality and safety.
An immediate re) air would have necessitated the isolation of portions of the SWS that are otlerwise structurally sound and capable of performing their intended safety function, and would not have been in the )est interest of plant safety, given the small magnitude-of the flaw and the licensee's alternative program.
Accordingly, relief is authorized pursuant to 10 CFR 50.55a(a)(3)(ii).
Principal Contributor:
N. Kalyanam Date: September 24, 1997 J