05000528/LER-2023-001, Reactor Trip Following a Main Turbine Trip
| ML23158A305 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 06/07/2023 |
| From: | Harbor C Arizona Public Service Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 102-08628-CDH/DHD LER 2023-001-00 | |
| Download: ML23158A305 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| 5282023001R00 - 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 102-08628-CDH/DHD June 7, 2023 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Subject:
Palo Verde Nuclear Generating Station Unit 1 Docket No. STN 50-528 /Renewed License No. NPF-41 Licensee Event Report 2023-001-00 Enclosed, please find the Licensee Event Report (LER) 50-528/2023-001-00 that has been prepared and submitted pursuant to 10 CFR 50.73. This LER reports an event in which Unit 1 had an unplanned reactor trip following a main turbine trip on April 8, 2023.
In accordance with 10 CFR 50.4, copies of this LER are being forwarded to the Nuclear Regulatory Commission (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/DHD/cr Enclosure: Unit 1 Licensee Event Report 2023-001-00 cc:
R. J. Lewis Acting 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: 2023.06.07 17:38:01 -07'00'
ENCLOSURE Unit 1 Licensee Event Report 2023-001-00
Abstract
Palo Verde Nuclear Generating Station (PVNGS) Unit 1
00528 5
Unit 1 Reactor Trip Following a Main Turbine Trip 04 08 2023 2023 001 00 06 07 2023 1
100
Michael DiLorenzo, Department Leader, Nuclear Regulatory Affairs 623-393-3495 E
TG Motor GE Yes X
TL RLY GE Yes
07 31 2023 On April 8, 2023 at approximately 2144 MST, following a turbine trip due to the loss of control oil header pressure, both 13.8 kV non-class buses de-energized, which caused a loss of power to the Reactor Coolant Pumps and resulted in a reactor trip. The B auxiliary feedwater pump was started to feed both steam generators due to the de-energization also having led to the main feed pumps tripping on low suction pressure. A Main Steam Isolation Signal was manually actuated due to a loss of circulating water flow to the condenser, which isolated the main steam header and required the use of Atmospheric Dump Valves for heat removal.
The cause investigation is in progress, and the results will be reported in a supplement to this Licensee Event Report.Page of
- 3. LER NUMBER YEAR SEQUENTIAL NUMBER REV NO.
052 050
6. CAUSE OF THE EVENT
A Level 1 Root-Cause Evaluation is in progress for this event and at the time of the Licensee Event Report submittal the evaluation has not been completed. A supplement to the LER will be provided at the completion of the root-cause evaluation.
The following includes the most current information available regarding the immediate causes:
The A CO pump tripped on an electrical protection ground fault. The ground fault was caused by a degraded motor cable splice connection, which exposed the B-phase bolted connection.
The B CO pump did not build up immediate pressure due to insufficient oil level in the CO reservoir. The B CO pump delay in developing pressure led to the main turbine trip on low CO header pressure.
The generator switchyard output breakers did not open and a FBT did not occur due to no signal from the reverse power relays.
7. CORRECTIVE ACTIONS
A Level 1 Root-Cause Evaluation is in progress for this event and at the time of the Licensee Event Report submittal the evaluation has not been completed. A supplement to the LER will be provided at the completion of the root-cause evaluation, including additional corrective actions identified as part of the evaluation.
IMMEDIATE CORRECTIVE ACTIONS
The degraded cable splice connection on the A CO pump was repaired.
Addition of hydraulic fluid to the CO reservoir, calibration of the CO level indicating switch, and retrieval/reinstallation of the missing float parts from the CO reservoir for the level indicating switch were completed for the B CO pump hydraulic fluid low level condition.
8. PREVIOUS SIMILAR EVENTS
No similar events have been reported by PVNGS in the last three years due to the same initial cause.
5 5
Palo Verde Nuclear Generating Station Unit 1 00528 2023 001 00