05000251/LER-2025-001-01, Degraded Condition
| ML25143A173 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 05/23/2025 |
| From: | Mack K Florida Power & Light Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-2025-104 LER 2025-001-01 | |
| Download: ML25143A173 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2512025001R01 - NRC Website | |
text
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U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 Re:
Turkey Point Unit 4 Docket No. 50-251 Renewed Facility Operating License No. DPR-41 Reportable Event: 2025-01-01 Date of Event: March 3, 2025 Degraded Condition
References:
May 23, 2025 L-2025-104 10 CFR 50.73
- 1. L-2025-084"Degraded Condition" (ADAMS Accession No. ML25115A227)
The attached Licensee Event Report, 2025-01-01, is being submitted pursuant to the requirements of 10 CFR 50.73 to provide notification of the subject event. The original report was submitted under 2025-02 but should have been 2025-01 because the original 2025-01 was retracted.
Should you have any questions regarding this submission, please contact Maribel Valdez, Fleet Licensing Manager, at 561-904-5164.
This letter contains no new or modified regulatory commitments.
Sincerely, Kennet~ack Director, Licensing and Regulatory Compliance Florida Power & Light Company Attachment cc:
USNRC Regional Administrator, Region II USNRC Project Manager, Turkey Point Nuclear Plant USNRC Senior Resident Inspector, Turkey Point Nuclear Plant Mr. Clark Eldredge, Florida Department of Health Florida Power & Light Company 9760 SW 344th Street, Homestead, FL 33035
Abstract
On March 3, 2025, at 18:03 EST, while in Mode 5, a boric acid leak was found in Bottom Mounted Instrumentation I
(BMI) nozzle #6. There was cracking in the Bottom Mounted Nozzle (BMN) safe-end. This flaw was not able to be I
found acceptable in accordance with American Society of Mechanical Engineers (ASME)Section XI. The In-I I Service Inspection (ISi) program detected the leak and the issue was fixed with a designed replacement. A Past I
Operability Review (POR) found the RCS pressure boundary inoperable from January 15, 2024 to March 1, 2025, I
violating Technical Specification (TS) 3.4.13.a. This event is reported under 10 CFR 50. 73(a)(2)(ii)(A) and 10 CFR I
- 50. 73(a)(2)(i)(B).
Description of Event
I
- 2. DOCKET NUMBER
- 3. LER NUMBER IB SEQUENTIAL REV NUMBER NO.
00251
- - I 1-0 01 On March 3, 2025, at 1803 EST, while in Mode 5, it was determined that a flaw in the reactor coolant system pressure boundary did not meet ASME Section XI, Table IWB-341 0-1, "Acceptable Standards" due to a boric acid leak in BMI nozzle #6. There was cracking in the BMN safe-end. The ISi program identified leakage, which is the intent of the programmatic inspection. The degraded condition was corrected with a designed replacement that included a socket welded coupling joining the BMN nozzle to the thimble guide tube. The remaining bottom mounted nozzle safe-ends were visually inspected for leakage. A POR concluded the RCS pressure boundary was inoperable from January 15, 2024 to March 1, 2025 when unit 4 entered Mode 5 and was no longer in a mode of applicability, which is a violation of TS 3.4.13.a. This event is being reported pursuant to 10 CFR 50.73(a)(2)(ii)(A), Degraded Condition and 10 CFR 50.73(a)(2)(i)(B), Condition Prohibited by TS.
Cause of Event
The metallurgical failure analysis identified that the 304 stainless steel BMN safe-end had a "sensitized" microstructure. "Sensitization" is a metallurgical phenomenon in which chromium diffuses from the grain boundaries and reduces the corrosion resistance that was provided by the chromium. This phenomenon only occurs at a temperature range of roughly 900F to 1300F, which exceeds design and operating temperatures.
A review of the vessel fabrication and installation sequence specific to Turkey Point Unit 3 and Unit 4 identified that the safe end was welded to the penetrating nozzle prior to post weld heat treatment of the vessel penetration welds. This likely provided the thermal event needed to cause "sensitization".
Safety Significance
The RCS pressure boundary was inoperable because of the degraded pressure boundary, however, the charging pumps had the capability to make up for the leakage caused by the small cross section through-wall indication. The leakage detection systems were functional and are set to identify the leakage before it would be considered a significant issue. This leakage was below the significance of detection. The leakage was corrected by replacing the degraded safe-end.
This event is being reported pursuant to 10 CFR 50.73(a)(2)(ii)(A), Degraded Condition and 10 CFR 50.73(a)(2)(i)(B), Condition Prohibited by TS.
Corrective Actions
When the degraded condition was identified Turkey Point (PTN) replaced the BMI safe-end. A subsequent visual inspection of all other BMN safe-end nozzles did not identify any additional leaks. PTN is following industry guidance which specifies that visual monitoring for leakage pursuant to existing programmatic scopes and frequencies is sufficient and no changes are required.
Similar Events
A review of events over the past 5 years did not identify any similar events with the same cause as this event. Page 2
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