05000339/LER-2023-001, Reactor Coolant Pressure Boundary Leak Due to Poor Weld Workmanship

Reactor Coolant Pressure Boundary Leak Due to Poor Weld Workmanship

ML24012A145
Person / Time
Site:	North Anna
Issue date:	11/30/2023
From:	Hilbert L Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
23-321 LER 2023-001-00
Download: ML24012A145 (1)

LER-2023-001, Reactor Coolant Pressure Boundary Leak Due to Poor Weld Workmanship

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(1) 10 CFR 50.73(a)(2)(v), Loss of Safety Function
3392023001R00 - NRC Website

text

VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 10CFR50.73 Virginia Electric and Power Company North Anna Power Station 1022 Haley Drive Mineral, Virginia 23117 November 30, 2023 Attention: Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555-0001 Dear Sir or Madam:

Serial No.:

23-321 NAPS:

RAP Docket Nos.: 50-339 License Nos.: NPF-7 Pursuant to 1 0CFR50.73, Virginia Electric and Power Company hereby submits the following Licensee Event Report applicable to North Anna Power Station Unit 2.

Report No. 50-339/2023-001-00 This report has been reviewed by the Facility Safety Review Committee and will be forwarded to the Management Safety Review Committee for its review.

Sincerely, 4 ad)--

Lisa Hilbert Site Vice President North Anna Power Station Enclosure Commitments contained in this letter: None cc:

United States Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, Georgia 30303-1257 NRC Senior Resident Inspector North Anna Power Station

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2024 (1~1-2023)

1. Facility Name

~ 050

2. Docket Number

3. Page North Anna Power Station 00339 1 OF 3

052

4. Title Reactor Coolant Pressure Boundary Leak Due to Poor Weld Workmanship

5. Event Date

6. LER Number

7. Report Date

8. Other Facllltles Involved Month Day Year Year Sequential Revlalon Month Day Year Facility Name Docket Number Number No.

050 10 03 2023 2023 -

001 -

00 11 30 2023 Facility Name Docket Number 052

9. Operating Mode 110. Power Leval 6

000

11. This Report Is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply) 10 CFR Part 20 20.2203(a)(2)(vl) 10 CFR Part 50

~ 50. 73(a)(2)(11)(A)

50. 73(a)(2)(vlll)(A) 73.1200(a) 20.2201(b) 20.2203(8)(3)(1) 50.36(c)(1)(1)(A)

50. 73(a)(2)(11)(B)

50. 73(a)(2)(vlll)(B) 73.1200(b) 20.2201(d) 20.2203(a)(3)(11) 50.36(c)(1)(11)(A)

50. 73(a)(2)(111)

50. 73(a)(2)(1x)(A) 73.1200(c) 20.2203(8)(1) 20.2203(8)(4) 50.36(c)(2)

50. 73(a)(2)(1v)(A)

50. 73(a)(2)(x) 73.1200(d) 20.2203(8)(2)(1) 10 CFR Part 21 50.46(a)(3)(11)

50. 73(a)(2)(v)(A) 10 CFR Part 73 73.1200(8) 20.2203(8)(2)(11) 21.2(c) 50.69(g)

50. 73(a)(2)(v)(B)

73. 77(a)(1) 73.1200(f) 20.2203(8)(2)(111) 50.73(a)(2)(1)(A)

50. 73(a)(2)(v)(C) 73.n(a)(2)(1) 73.1200(g) 20.2203(a)(2)(Iv) 50.73(a)(2)(1)(B) 50.73(a)(2)(v)(D)

73. n(a)(2)(11) 73.1200(h) 20.2203(a)(2)(v) 50.73(a)(2)(1)(C)

50. 73(a)(2)(vll)

OTHER (Specify here, In abstract, or NRC 366A).

12. Licensee Contact for this LER Licensee Contact Phone Number (Include area code)

Lisa Hilbert, Site Vice President (540} 894-2101 Cause System Component Manufacturer Reportable to IRIS Cause System Component Manufacturer Reportable to IRIS A

AB TBG y

14. Supplemental Report Expected Month Day Year 0

15. Expected Submission Date No Yes (If yes, complete 15. Expected Submission Date)

18. Abstract (Limit to 1326 spaces. I.e., approximately 13 single-spaced typewritten lines)

On September 11, 2023, at 1558 hours0.018 days <br />0.433 hours <br />0.00258 weeks <br />5.92819e-4 months <br /> with Unit 2 in Mode 5 at 140 degrees F and 30 psig for a refueling outage, a boric acid leak was discovered on tubing associated with a Pressurizer level transmitter. The leak was not quantifiable as it consisted of a small amount of dry boric acid. Non-destructive examination (NDE} was performed on the leak to determine if it was a through wall leak. On October 3, 2023, at 1154 with Unit 2 in Mode 6 at 100 degrees F and atmospheric pressure, the NOE determined the leak was a through wall leak. This failure constitutes welding or material defects in the primary coolant system that cannot be found acceptable under ASME Section XI. Therefore, an 8-hour report was made for a degraded.condition under 10 CFR 50.72(b}(3}(ii}(A}.

The direct cause of the weld failure was due to inadequate welding process control by the welder. Unit 1 was not impacted by this event. The health and safety of the public were not affected by this event.

..I 1.0 Description of Event

2. DOCKET NUMBER I

00339

3. LER NUMBER r:::7 NUMBER NO.

I YEAR SEQUENTIAL REV

~-I 001 1-0 On September 11, 2023, at 1558 hours0.018 days <br />0.433 hours <br />0.00258 weeks <br />5.92819e-4 months <br /> with Unit 2 in Mode 5 at 140 degrees F and 30 psig for a refueling outage, a boric acid leak was discovered on tubing associated with a Pressurizer (EIIS Component PZR, System AB) level transmitter (EIIS Component LT, System AB). The leak was not quantifiable as it consisted of a small amount of dry boric acid.

Non-destructive examination (NOE) was performed on the leak to determine if it was a through wall leak. On October 3, 2023, at 1154 with Unit 2 in Mode 6 at 100 degrees F and atmospheric pressure, the NDE determined the leak was a through wall leak. This failure constituted welding or material defects in the primary coolant system that cannot be found acceptable under ASME Section XI. Therefore, an 8-hour report was made for a degraded condition under 10 CFR 50.72(b)

(3)(ii)(A). This weld was part of an instrument tubing design change that was implemented in 1998.

l2.0 Significant Safety Consequences and Implications No significant safety consequences resulted from this event. The leak was discovered while Unit 2 was shut down for a refueling outage. The leak was not quantifiable based on the small amount of boric acid noted and, therefore, well within the capability of one charging pump (EIIS Component P, System CB). The health and safety of the public were not affected by this event.

3.0 Cause of the Event

!The direct cause of the weld failure was due to inadequate welding process control by the welder. The specific socket welds in question exhibited poor workmanship by having a large degree of melt-through and suck-back on the inside surface, and multiple arc strikes and excessive grinding on the outside surface. During the metallurgical failure analysis, the sample was

~actioned through the area of suspected leakage, which revealed a lack of fusion defect between the weldment and base metal. The degree of lack of fusion confirmed in the laboratory analysis was substantial enough to provide the eventual leak path after a 25-year service period.

14.0 Immediate Corrective Action Both the leaking socket welded coupling and a non-leaking downstream socket welded coupling were replaced. NDE isurface examinations were performed on the replacement socket welds, and the area was also examined during an external leakage check.

5.0 Additional Corrective Actions Additional Liquid Penetrant (LP) exams were performed on tubing welds from the pressurizer steam space to a different Pressurizer level transmitter. No weld flaws or boric acid residue was identified during these examinations. For the next refueling outages for each unit, work orders have been created to inspect tubing socket welds that were fabricated in a similar timeframe, under similar field conditions, using the same welding and inspection procedures, and had an overlap of qualified welders performing the work.

6.0 Actions to Prevent Recurrence

2. DOCKET NUMBER

3. LER NUMBER I

00339 NUMBER NO.

I YEAR SEQUENTIAL REV 1

001 1-0 Nuclear Welding Program Authorized By training will be updated to include this operating experience (OE) of workmanship issues when welding tubing.

7.0 Similar Events No similar events have been noted at North Anna for instrument tube welding failures.

8.0 Additional Information Unit 1 was unaffected by this event. Page 3

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