05000528/LER-2023-002, Reactor Coolant System Degraded Pressure Boundary
| ML23342A068 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 12/08/2023 |
| From: | Harbor C Arizona Public Service Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 102-08706-CDH/TR LER 2023-002-00 | |
| Download: ML23342A068 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| 5282023002R00 - NRC Website | |
text
10 CFR 50.73 A member of the STARS Alliance, LLC Callaway
- Diablo Canyon
- Palo Verde
- Wolf Creek Cary D. Harbor Vice President Regulatory & Oversight Palo Verde Nuclear Generating Station P.O. Box 52034 Phoenix, AZ 85072 Mail Station 7605 Tel: 623.393.7953 102-08706-CDH/TR December , 2023 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Subject:
Palo Verde Nuclear Generating Station (PVNGS) Unit 1 Docket No. STN 50-528 /Renewed License No. NPF-41 Licensee Event Report 2023-002-00 Enclosed, please find the Licensee Event Report (LER) 50-528/2023-002-00 that has been prepared and submitted pursuant to 10 CFR 50.73. This LER FRQFHUQs a Unit 1 Reactor Coolant System Degraded Pressure Boundary event which was rHSRUWHG to the Nuclear Regulatory Commission (NRC) on October 9, 2023.
In accordance with 10 CFR 50.4, copies of this LER are being forwarded to the NRC Regional Office, NRC Region IV, and the Senior Resident Inspector.
No new commitments are being made to the NRC by this letter. Should you need further information regarding this submittal, please contact Michael DiLorenzo, Department Leader, Nuclear Regulatory Affairs, at (623) 393-3495.
Sincerely, CDH/TR/cr Enclosure: Unit 1 Licensee Event Report 2023-002-00 cc:
J. Monninger NRC Region IV Regional Administrator S. P. Lingam NRC NRR Project Manager for PVNGS L. N. Merker NRC Senior Resident Inspector for PVNGS Harbor, Cary (Z16762)
Digitally signed by Harbor, Cary (Z16762)
Date: 2023.12.08 07:31:12 -07'00'
ENCLOSURE Unit 1 Licensee Event Report 2023-002-00
NRC FORM 366 (10-01-2023)
U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)
(See Page 2 for required number of digits/characters for each block)
(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2024
- 1. Facility Name 052 050
- 2. Docket Number
- 3. Page 1 OF
- 4. Title
- 5. Event Date Month Day Year
- 6. LER Number Year Sequential Number Revision No.
- 7. Report Date Month Day Year
- 8. Other Facilities Involved Facility Name Facility Name Docket Number Docket Number
- 9. Operating Mode
- 10. Power Level 050 052
Month Day Year Palo Verde Nuclear Generating Station (PVNGS) Unit1
00528 4
Reactor Coolant System Degraded Pressure Boundary 10 09 2023 2023 002 00 12 0
2023 5
000
Michael DiLorenzo, Department Leader, Nuclear Regulatory Affairs 623-393-3495 B
AB PZR C490 Y
16. Abstract (Limit to 1326 spaces, i.e., approximately 13 single-spaced typewritten lines)
On October 9, 2023, during the Palo Verde Nuclear Generating Station (PVNGS) Unit 1 refueling outage, while performing small nozzle inspection in support of boric acid walkdowns, boric acid was found on the area of the weld of a pressurizer thermowell. Non-destructive examination UHVXOWVindicated PLQRUleakage through the ZHOGWKDWGLG
QRWFKDOOHQJHWKHSK\\VLFDOLQWHJULW\\RIWKHUHDFWRUFRRODQWV\\VWHP. The exam result constitutes welding or material defects in the primary coolant system that are RXWVLGHWKH American Society of Mechanical Engineers (ASME)
Section XIFULWHULD.
The direct cause of the reactor coolant pressure boundary leakage identified on the Unit 1 pressurizer thermowell nozzle weld was three pinhole leaks on the welded connection. The pressurizer thermowell nozzle was replaced prior to entering Mode 4 using materials knowQ to be resistant to Primary Water Stress Corrosion Cracking (PWSCC). Page of
- 3. LER NUMBER YEAR SEQUENTIAL NUMBER REV NO.
052 050
7. CORRECTIVE ACTIONS
Perform an ASME Code approved* welded pad / nozzle repair, using materials known to be resistant to Primary Water Stress Corrosion Cracking. The Unit 1 pressurizer thermowell nozzle was replaced prior to entering Mode 4.
Review the results of the boat sample analysis performed by an off-site vendor to determine the root cause of the Unit 1 pressurizer thermowell nozzle weld failure. A supplement to the LER will be provided if that analysis results in a substantial change in the corrective actions.
- To complete the code approved repair, Arizona Public Service Company proposed to the NRC an alternative to the requirements of the ASME Code in a Relief Request. The NRC determined that the proposed alternative provides an acceptable level of quality and safety in accordance with 10 CFR 50.55a(z)(1) and provided a verbal authorization.
8. PREVIOUS SIMILAR EVENTS
No similar events have been reported by PVNGS in the last three years.
4 4
Palo Verde Nuclear Generating Station Unit 1 00528 2023 002 00