05000529/LER-2023-001-01, Unit 2 Automatic Reactor Trip on Low Steam Generator Water Level Due to Degraded Feedwater Flow
| ML23313A162 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 11/09/2023 |
| From: | Harbor C Arizona Public Service Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 102-08679-CDH/TR LER 2023-001-01 | |
| Download: ML23313A162 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| 5292023001R01 - 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 102-08679-CDH/TR November 9, 2023 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Subject:
Palo Verde Nuclear Generating Station (PVNGS) Unit 2 Docket No. STN 50-529 /Renewed License No. NPF-51 Licensee Event Report Supplement 2023-001-01 Enclosed, please find the Licensee Event Report (LER) 50-529/2023-001-01 that has been prepared and submitted pursuant to 10 CFR 50.73. This LER supplement provides additional information that was identified through PVNGS evaluation of the unplanned Unit 2 reactor trip that occurred on June 2, 2023. The initial LER 2023-001-00 for the Unit 2 reactor trip was provided to the Nuclear Regulatory Commission (NRC) on August 1, 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 2 Licensee Event Report 2023-001-01 cc:
J. Monninger NRC Region IV Regional Administrator S. P. Lingam NRC NRR Project Manager for PVNGS D. Galvin NRC NRR Project Manager L. N. Merker NRC Senior Resident Inspector for PVNGS Harbor, Cary (Z16762)
Digitally signed by Harbor, Cary (Z16762)
Date: 2023.11.09 06:33:16 -07'00'
ENCLOSURE Unit 2 Licensee Event Report 2023-001-01
Abstract
Palo Verde Nuclear Generating Station (PVNGS) Unit 2
00529 5
Unit 2 Automatic Reactor Trip On Low Steam Generator Water Level Due To Degraded Feedwater Flow 06 02 2023 2023 001 01 11 09 2023 1
100
Michael DiLorenzo, Department Leader, Nuclear Regulatory Affairs 623-393-3495 B
SJ FCV G080 Y
Unit 2 experienced an automatic reactor trip from 100 percent power on June 2, 2023, at 0405 Mountain Standard Time due to a drifting down of the A feedwater (FW) pump speed. Feedwater control system (FWCS) speed demand increased, as expected, to counter the reduction in feedwater flow; however, the A FW pump speed was unresponsive to demand. The B FW pump speed increased in response to the increased demand signal with no abnormalities. Steam Generator (SG) 1 and SG 2 wide-range level indications lowered to 44 percent, which resulted in a reactor trip and turbine trip.
The cause of the reactor trip was determined to be the result of the loose nuts on either side of the moveable armature block within the servo control valve installed in the A FWCS. Corrective actions resulting from the event include ensuring the servo nuts are torqued and thread locker is applied and implementation of servo valve inspection and functional testing upon receipt and prior to installation. Page of
- 3. LER NUMBER YEAR SEQUENTIAL NUMBER REV NO.
052 050
8. PREVIOUS SIMILAR EVENTS
No similar events have been reported by PVNGS in the last three years due to the same initial cause.
However, there has been a similar sequence of events that occurred on March 3, 2020, when the Unit 2 reactor automatically tripped on a low SG 1 level signal. Although the initiating event for the reactor trip was the same, the cause of the SG low water level was different. In 2020, the Unit 2 reactor trip was due to a trip of both of the Main Feedwater Pumps (MFWPs), which tripped during restoration of power to the MFWPs Lube Oil (LO) control panels.
The corrective actions from the previous LER event would not have prevented the event which is the subject of this Licensee Event Report.
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Palo Verde Nuclear Generating Station Unit 2 00529 2023 001 01