05000456/LER-2025-002, Liquid Penetrant Indication in Control Rod Drive Mechanism Nozzle Seal Weld Repair Due to Subsurface Weld Defects Opening from Thermal and Pressure Stresses During Operation

Liquid Penetrant Indication in Control Rod Drive Mechanism Nozzle Seal Weld Repair Due to Subsurface Weld Defects Opening from Thermal and Pressure Stresses During Operation

ML25338A187
Person / Time
Site:	Braidwood
Issue date:	12/04/2025
From:	Constellation Energy Generation
To:	Office of Nuclear Reactor Regulation
Shared Package
ML25338A185	List: 05000456/LER-2025-002, Liquid Penetrant Indication in Control Rod Drive Mechanism Nozzle Seal Weld Repair Due to Subsurface Weld Defects Opening from Thermal and Pressure Stresses During Operation BW250053, Liquid Penetrant Indication in Control Rod Drive Mechanism Nozzle Seal Weld Repair Due to Subsurface Weld Defects Opening from Thermal and Pressure Stresses During Operation (Cover Letter)
References
BW250053 LER 2025-002-00
Download: ML25338A187 (0)

LER-2025-002, Liquid Penetrant Indication in Control Rod Drive Mechanism Nozzle Seal Weld Repair Due to Subsurface Weld Defects Opening from Thermal and Pressure Stresses During Operation

Event date:
Report date:
4562025002R00 - NRC Website

text

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 04/30/2027 (04-02-2024)

2. DOCKET NUMBER YEAR 05000456 2025 Reactor Power: 000 percent

3. LER NUMBER SEQUENTIAL NUMBER 002 Ambient temperature and depressurized REV NO.

00 No structures, systems or components were inoperable at the start of this event that contributed to the event.

B. Description of Event

On October 10, 2025 at 02 30 CDT, a Liquid Penetrant (PT) examination on the seal weld repair known as the Embedded Flaw Repair (EFR) of Control Rod Drive Mechanism (CROM) Penetration 69 was performed. During the PT examination, one unacceptable rounded indication was discovered on the EFR penetration. Rounded indications that exceed 3/16 inches in any dimension are unacceptable per the acceptance criteria in ASME Section Ill.

The indication was a 3/8-inch rounded indication located at 190 degrees on the reactor head portion of the overlay and was 4.3 inches from the tube of the head to the penetration on the head side. Zero degrees azimuth is located at the outermost portion of the penetration on the flange side (downhill/outermost side). The transition is the point where the vertical portion of the penetration meets the horizontal area of the reactor head.

This event is reportable in accordance with 10 CFR 50. 73(a)(2)(ii)(A) for "Any event or condition that resulted in the condition of the nuclear power plant, including its principal safety barriers, being seriously degraded", since the as-found indication did not meet the applicable acceptance criterion referenced in ASME Section Ill to remain in service vvithout repair. This LER is being submitted in follovv-up to E~~S 57978 rnade on October 10 1 2025 at 09:25 CDT.

C. Cause of Event

The cause of the indication is attributed to existing mechanical discontinuities/minor subsurface voids growing or opening to the weld surface due to the thermal and/or pressure stresses during plant operation. Unacceptable rounded indications have previously been identified on the EFR on CROM Penetration 69.

D. Safety Consequences

This condition had no actual safety consequences impacting plant or public safety.

The unacceptable indication was identified in a timely manner during routine inspection activities and repaired prior to through-wall leakage occurring The indication did not penetrate through the EFR. With these required inspections being performed at the required intervals, detected degradation that does not meet acceptance criteria will be repaired or evaluated prior to reaching any level of significance. This condition is limited to CROM Penetration 69 at Braidwood Unit 1. CROM Penetration 69 is the only penetration at Braidwood Unit 1 that has been repaired utilizing this EFR method.

Bare metal visual examination on the reactor vessel closure head did not detect any evidence of reactor coolant pressure boundary leakage. Based on the characteristics and dimensions of the unacceptable indication discovered during PT examination, there was no loss of safety function due to this indication.

NRC FORM 366.A. (04-02-2024)

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E. Corrective Actions

Estimated burden per response to lessor1s learned are incorporated into burden estimate to the FOLL, Library collection request 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported fed back to industry. Send comments Collecticns Braner, (T-6 A 1 Olvl). U S 20555-0001.

or by email to at: 0MB Office of information and Desk Officer for the Nuclear P.egulatcry Cocr,mission. 725 17th Street Washington The NRC may not conduct or sponsor. and a person is not required to respond to, a coiiection of information unless the document requesting or requiring the collection displays a currently valid OlvlB control number.

2. DOCKET NUMBER YEAR 05000456 2025

3. LER NUMBER SEQUENTIAL NUMBER 002 REV NO.

00 Actions were completed to buff and blend the indication to remove the indication to meet applicable acceptance criteria in ASME Section Ill. A PT examination was performed after the buffing/blending to determine if the indication met acceptance criteria and the indication was verified to have been removed.

F.

Previous Occurrences

Previous Licensee Event Reports were made in June 2012, November 2013, June 2015, November 2016 and November 2022 at Braidwood Station Unit 1 for indications on CROM penetration 69 (LER 2012-002-00, LER 2013-002-00, LER 2015-002-00, LER 2016-003-00, and LER 2022-001-00).

G. Component Failure Data

Manufacturer Westinghouse Nomenclature Reactor Vessel Integrated Head Package Termination Model 1718E72 Mfg. Part Number N/A Page_3_ of _3_