ML21069A064
| ML21069A064 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 03/18/2021 |
| From: | Undine Shoop Plant Licensing Branch II |
| To: | Maza K Duke Energy Progress |
| Mahoney M-NRR/DORL 301-415-3867 | |
| References | |
| EPID L-2020-LLR-0143 | |
| Download: ML21069A064 (8) | |
Text
March 18, 2021 Ms. Kim Maza Site Vice President Shearon Harris Nuclear Power Plant 5413 Shearon Harris Road Mail Code NHP01 New Hill, NC 27562-9300
SUBJECT:
SHEARON HARRIS NUCLEAR POWER PLANT, UNIT 1 - ALTERNATIVE TO ASME SECTION XI CODE REQUIREMENTS TO DEFER REPAIR OF EMERGENCY SERVICE WATER SYSTEM SOCKET WELD (EPID L-2020-LLR-0143)
Dear Ms. Maza:
The U.S. Nuclear Regulatory Commission (NRC) has approved your request for a deferral of an American Society of Mechanical Engineers (ASME) Code repair of a through-wall leak in a pipe in the Emergency Service Water (ESW) system for the Shearon Harris Nuclear Power Plant, Unit 1. This action is in response to your request RA-20-312, dated November 4, 2020, as supplemented by letter dated February 25, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML20309A774 and ML21056A625, respectively).
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), the licensee requested to use an alternative on the basis that complying with the specified requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The NRC staff has concluded that the proposed alternative RA-20-312 provides reasonable assurance of structural integrity of the subject components and that complying with the specified ASME Code requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Accordingly, the NRC staff concludes that the licensee has adequately addressed all the regulatory requirements set forth in 10 CFR 50.55a(z)(2).
Therefore, the NRC staff authorizes proposed alternative RA-20-0312 at the Shearon Harris Nuclear Power Plant, Unit 1, until the next planned outage of sufficient duration, but no later than the next refueling outage, currently scheduled to begin in April 2021.
All other ASME Boiler and Pressure Vessel Code,Section XI, requirements which are not modified by the NRC staffs approval of the licensees request remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
K. Maza If you have any questions, please contact the Shearon Harris, Project Manager, Michael Mahoney at 301-415-3867 or via email at Michael.Mahoney@nrc.gov.
Sincerely, Digitally signed by Undine S. Undine S. Shoop Date: 2021.03.18 Shoop 15:45:11 -04'00' Undine S. Shoop, Chief Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-400
Enclosure:
Safety Evaluation cc: Listserv
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST RA-20-0312 - ALTERNATIVE TO ASME SECTION XI CODE REQUIREMENTS TO DEFER REPAIR OF EMERGENCY SERVICE WATER SYSTEM SOCKET WELD DUKE ENERGY PROGRESS, LLC SHEARON HARRIS NUCLEAR POWER PLANT, UNIT 1 DOCKET NO. 50-400
1.0 INTRODUCTION
By letter RA-20-312, dated November 4, 2020, as supplemented by letter dated February 25, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession Nos.
ML20309A774 and ML21056A625, respectively), Duke Energy Progress, LLC (the licensee),
requested U.S. Nuclear Regulatory Commission (NRC) approval for deferral of an American Society of Mechanical Engineers (ASME) Code repair of a through-wall leak in a pipe in the Emergency Service Water (ESW) system for the Shearon Harris Nuclear Power Plant, Unit 1 (Harris).
Pursuant to Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Paragraph 55a(z)(2),
the licensee requested the NRC to authorize deferral of the ASME Code repair of the identified through-wall leak until the next planned outage of sufficient duration, but no later than the next refueling outage, currently scheduled to begin in April 2021.
Specifically, pursuant to 10 CFR 50.55a(z)(2), the licensee requested to use the proposed alternative on the basis that compliance with the specified ASME Code requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
2.0 REGULATORY EVALUATION
Regulatory Requirements Adherence to Section XI of the ASME Code is mandated by 10 CFR 50.55a(g)(4), which states, in part, that ASME Code Class 1, 2, and 3 components will meet the requirements, except the design and access provisions and the pre-service examination requirements, set forth in the ASME Code,Section XI.
Paragraph 10 CFR 50.55a(z) states, in part, that alternatives to the requirements of 10 CFR 50.55a(b) through (h) may be used, when authorized by the Director, Office of Nuclear Enclosure
Reactor Regulation, if (1) the proposed alternatives would provide an acceptable level of quality and safety or (2) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The licensee has submitted this request on the basis that compliance with the specified ASME Code requirements would result in unnecessary hardship without a compensating increase in the level of quality and safety.
Guidance NRC Generic Letter (GL) 90-05, Guidance for Performing Temporary Non-Code Repair of ASME Code Class 1, 2, and 3 Piping, (ADAMS Legacy Accession No. 9006120310), provides generic guidance to licensees that will be considered by the NRC staff in evaluating proposed alternatives for temporary non-code repairs of ASME Code Class 3 piping.
3.0 TECHNICAL EVALUATION
3.1 ASME Code Components Affected by the Proposed Alternative Emergency Service Water (ESW) System piping, line 3SW1-141SB-1 Code Class: ASME, Class 3
==
Description:==
Connection line for pressure transmitter located at the outlet of the B Component Cooling Water heat exchanger within the ESW return line.
Size: 1 inch, schedule 80 Material: Carbon Steel SA-106, Grade B 3.2 Applicable Code Edition, Addenda, and Requirements The fourth inspection interval for Harris began on September 9, 2017 and is scheduled to end September 8, 2027. The Code of Record for the fourth inspection interval is ASME Code,Section XI, 2007 Edition through 2008 Addenda.
ASME Code, Section Xl, 2007 Edition through 2008 Addenda, Article IWA-4421, General Requirements, requires that defects be removed or mitigated in accordance with code requirements IWA-4340, IWA-4411, IWA-4461, or IWA-4462 (Note: Use of IWA-4340 is prohibited by 10 CFR 50.55a(b)(2)(xxv)(A)).
3.3 Reason for Request The licensee stated that on September 20, 2020, personnel identified a pinhole leak in the ESW piping line 1SW1-141SB-1 during operator rounds. The licensee stated that ASME Code, Section Xl, 2007 Edition requires ab ASME Code repair and isolation of the affected line is not practical given the location of the line relative to the ESW return header. Additionally, repair will require removing the affected train of ESW from service for the repair duration, which requires entry into the technical specification (TS) limiting condition of operation (LCO) TS 3.7.4 for one inoperable ESW train. TS LCO 3.7.4, requires restoration to an operable status of an
inoperable ESW train within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, or the plant would have to be in hot standby within the following next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. The licensee further states:
Based on the difficulty of isolating the affected area of service water piping and performing a code repair within the time period permitted by the limiting condition of operability, relief is being requested from ASME Code, Section Xl, 2007 Edition through 2008 Addenda, Article IWA-4421, in accordance with 10 CFR 50.55a(z)(2) to prevent an unnecessary hardship caused by requiring a unit shutdown without a compensating increase in quality and safety.
3.4 Licensees Proposed Alternative As an alternative to the ASME Code repair, as required by ASME Code, Section Xl, 2007 Edition through 2008 Addenda, Article IWA-4421, the licensee proposed the following strategy to address the identified flaw:
Duke Energy proposes to defer the code repair of the identified flaw until the next planned outage of sufficient duration, but no later than the next refueling outage, currently scheduled to begin in April 2021. During the interim period, augmented inspections will be performed at a three-month frequency to detect changes in the condition of the identified defect. This testing will use suitable nondestructive examination methods, including UT [ultrasonic testing].
Additionally, a qualitative assessment of leakage will be performed at least once a week during plant walkdown inspections to determine if there is additional degradation of structural integrity.
3.5 Licensees Bases for Use The licensee stated that that complying with ASME Code, Section Xl, 2007 Edition through 2008 Addenda, Article IWA-4421, requirements to remove defective portions of this piping prior to performing a repair/replacement activity represents a hardship or unusual difficulty without a compensating increase in the level of quality and safety, for the following reasons:
The current loss of flow from the ESW system is negligible compared to the total system flow.
There is no equipment in the area that would be damaged due to spray from the pinhole leak, should spray develop and the leakage does not present any flooding concerns in the area.
The licensee performed augmented UT in accordance with GL 90-05 on five additional accessible locations deemed most susceptible to a similar flaw and no additional flaws were detected requiring characterization or evaluation.
The licensee used GL 90-05 through-wall flaw evaluation criteria to access the structural integrity of the piping with the identified flaw. The licensee stated that the evaluation determined that the crack length does not exceed 15 percent of the pipe circumference.
Additionally, the licensee stated that the identified flaw shows no signs of propagation.
Further, the licensee stated:
Based on the structural integrity evaluation, the low risk of impact to nearby components, and the monitoring, Duke [the licensee] believes deferring the repair to the next refueling outage is acceptable.
3.6 Duration of Proposed Alternative The licensee requested NRC approval to defer implementation of ASME Code repairs no later than the next scheduled refueling outage, currently scheduled for April 2021, as permitted by GL 90-05.
3.7 NRC Staff Evaluation The licensee proposed to defer the repair of the subject pinhole leak in the socket weld that attaches the 1-inch nominal pipe size (NPS) ESW piping line 3SW1-141SB-1 to a sockolet on ESW return line 3SW24-73SB-1. Piping line 3SW1-141SB-1 is classified as ASME Code Class 3 and operates at relatively low temperature and pressure, 125 degrees Fahrenheit and 130 pounds per square inch gauge maximum, respectively. The licensee stated that the flaw appears to be at the stop-start interface of the socket weld. The flaw was discovered on September 20, 2020. The licensees letter dated November 4, 2020 indicated that the flaw was less than 1/16 inches in diameter and leaking at approximately 1 drop per minute. The licensee stated in their letter dated February 25, 2021 that daily monitoring indicated that the leakage was less than 1 drop per minute. The NRC staff notes that the lack of a noticeable increase in leakage over a 5-month period, indicates that the flaw is stable and not increasing at any measurable rate.
The NRC staff evaluated the licensees proposed alternative RA-20-0312, including its use of the guidance provided in GL 90-05 and the basis for the proposed alternative, in accordance with 10 CFR 50.55a(z)(2). GL 90-05 provides generic guidance to licensees that will be considered by the NRC staff in evaluating proposed alternatives for temporary non-code repairs of ASME Code Class 3 piping when a code repair of such piping would necessitate a plant shutdown. The guidance in GL 90-05 includes use of the through-wall flaw approach or wall-thinning approach to determine structural integrity and assessing the overall degradation of the system by performance of augmented inspections. Additionally, system interactions such as flooding, water spray on equipment, and loss of flow, should be considered.
The licensee performed UT of the pipe (3SW1-141SB-1) material in the vicinity of the flaw and measured a minimum wall-thickness of 0.137 inches. The nominal wall-thickness of the subject pipe is 0.179 inches. The licensee performed thickness measurements of return line 3SW24-73SB-1, where the sockolet is welded to the return line with no measurements below the nominal wall thickness of 0.375 inches recorded. The sockolet wall-thickness was also measured with no appreciable degradation discovered. The UT results and the lack of vibration in the line, as reported by the licensee, supports the licensees determination that the flaw is most likely a small hole that extends in the radial direction from the pipe to outer edge of the coupling (from where there is likely stagnant water between the outer diameter of the pipe and the inside diameter of the sockolet fitting). The NRC staff notes that this type of flaw is unlikely to challenge structural integrity of the line.
The licensee utilized the through-wall flaw approached described in GL 90-05, postulating a conservative crack length of 0.1 inches, and determined that the structural integrity of the flawed pipe will be maintained until the next refueling outage, scheduled to begin in April 2021. The NRC staff reviewed the licensees evaluation and verified that its through-wall flaw approach is consistent with the guidance provided in GL 90-05. Consistent with the GL 90-05, the licensee performed augmented UT examinations of five additional locations deemed to be the most susceptible to degradation discovered in line 3SW1-141SB-1 and did not discover any flaws that required characterization or evaluation. The licensee stated that there is no spray from the flaw, and should a spray develop, there is no equipment in the area that would be damaged. Given that the system flow is 8,500 gallons per minute, loss of flow due to the flaw is insignificant.
Based on the above, the NRC staff finds that the licensee has appropriately followed the guidance provided in GL 90-05.
The licensee indicated that the time period permitted by TS LCO 3.7.4 is not sufficient to perform an ASME Code repair and a plant shutdown would be required. The NRC staff finds that performing an ASME Code repair of the subject flaw, resulting in a plant shutdown, would unnecessarily cycle the unit, resulting in unnecessary transients, potential plant risk and personnel exposure. In addition, the licensee has provided sufficient information to support its conclusion that the structural integrity of the subject pipe will be maintained until the next scheduled refueling outage.
3.6.5 NRC Staff Evaluation Summary The NRC staff finds that complying with the specified requirements described in the licensees request, referenced above, would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Additionally, the NRC staff finds that the proposed alternative provides reasonable assurance of structural integrity of the subject component.
5.0 CONCLUSION
As set forth above, NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(2). Therefore, the NRC authorizes the use of proposed alternative RA-20-0312 at the Shearon Harris Nuclear Power Plant, Unit 1, until the next planned outage of sufficient duration, but no later than the next refueling outage, currently scheduled to begin in April 2021.
All other ASME BPV Code,Section XI requirements for which an alternative was not specifically requested and approved in this proposed alternative remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: R. Davis, NRR Date: March 18, 2021
ML21069A064 *By Memorandum OFFICE NRR/DORL/LPL2-2/PM NRR/DORL/LPL2-2/LA NRR/DNRL/NPHP/BC*
NAME MMahoney RButler MMitchell DATE 03/17/2021 03/16/2021 03/05/2021 OFFICE DORL/LPL2-2/BC NAME UShoop DATE 03/17/2021