05000445/LER-2023-001-01, (Cpnpp), Automatic Reactor Trip Due to Lo-Lo Steam Generator Level
| ML23285A094 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 10/12/2023 |
| From: | John Lloyd Luminant, Vistra Operating Co. (VistraOpCo) |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| CP-202300477, TXX-23079 LER 2023-001-01 | |
| Download: ML23285A094 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 4452023001R01 - NRC Website | |
text
m Luminant CP-202300477 TXX-23079 October 12, 2023 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 JayJ. Lloyd Senior Director, Engineering & Regulatory Affairs
Subject:
Comanche Peak Nuclear Power Plant (CPNPP)
Docket Nos. 50-445 Automatic Reactor Trip Due to Lo-Lo Steam Generator Level Licensee Event Report 445 / 23-001-01
Dear Sir or Madam:
Ref Comanche Peak Nuclear Power Plant (Vistra Operations Company LLC)
P.O. Box 1002 6322 North FM 56 Glen Rose, TX 76043 T 254.897.5337 10CFR50.73 Attached is Licensee Event Report (LER) 23-001-01, "Automatic Reactor Trip Due to Lo-Lo Steam Generator Level" for Comanche Peak Nuclear Power Plant (CPNPP) Unit 1. This is a supplement to the initial report, LER 23-001-00, submitted on August 15, 2023 (ML23227A145).
This communication contains no new commitments regarding CPNPP Units 1 and 2.
Should you have any questions, please contact Kassie Mandrell at (254) 897-6987 or Kassie.Mandrell@luminant.com.
Sincerely, Jay J. Lloyd Attachment: NRC Form 366 (4 pages) c (email) -
John Monninger, Region IV Uohn.Monninger@nrc.gov]
Dennis Galvin, NRR [Dennis.Galvin@nrc.gov]
John Ellegood, Senior Resident Inspector, CPNPP Uohn.Ellegood@nrc.gov]
Dominic Antonangeli, Resident Inspector, CPNPP [Dominic.Antonangeli@nrc.gov]
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 Comanche Peak Nuclear Power Plant
445 4
Automatic Reactor Trip Due to Lo-LoSteam Generator Level 06 16 2023 2023 001 -
01 10 12 2023 Mode 1 100
Kassie Mandrell 254-897-6987 B
JK PSV GE Y
16. Abstract (Limit to 1326 spaces, i.e., approximately 13 single-spaced typewritten lines)
On June 16, 2023, unit 1 was operating at 100% power. At 18:22, the 1B Main Feedwater Pump (MFP) began indicating oscillating speed. The oscillations increased in severity and became unresponsive to manual control input. Due to the loss of control, the 1B MFP was manually tripped as it approached the overspeed setpoints. Following the manual trip of the 1B MFP the Unit responded with an automatic runback to 700MWe. Following the runback, the combined effects of the entire transient resulted in an automatic reactor trip due to Steam Generator #4 Lo-Lo water level.
The direct cause of this event was a degraded servo on the 1B MFP. Vendor analysis of the component did not identify a specific failure mechanism and the cause is inconclusive. Based on engineering evaluation, the most probable cause is particulate accumulation in the servo valve due to historical water intrusion events into the 1B lube oil system. An additional supplement will be submitted if further analysis has more conclusive results. Corrective action included replacement of the servo.
This LER is a supplement to the original LER 23-001-00 submitted on 8/15/2023. All times are in Central Daylight Time (CDT).Page of
- 3. LER NUMBER YEAR SEQUENTIAL NUMBER REV NO.
052 050 C.SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT A turbine trip is an ANS Condition II event (Faults of Moderate Frequency). When the reactor was automatically tripped the Auxiliary Feedwater System started to provide feedwater to the steam generators. The reactor trip on lo-lo water level in any steam generator provides the necessary protection against a loss of normal feedwater.
An automatic reactor trip was exercised and the Auxiliary Feedwater System started automatically as expected and all plant safety systems responded as designed during the resultant transient. This event had no impact on nuclear safety, reactor safety, radiological safety, environmental safety or the safety of the public. This event has been evaluated as not meeting the definition of a safety system functional failure per 10 CFR 50.73(a)(2)(v).
IV.CAUSE OF THE EVENT The direct cause of this event was a degraded servo on the 1B MFP. Vendor analysis of the component failure was inconclusive. Engineering evaluation of the failure determined the most probable cause to be historical water intrusion events into the 1B lube oil system. This caused particulate accumulation in the servo valve and limited the ability of the LP control valves to regulate steam and control turbine speed.
V.CORRECTIVE ACTIONS Corrective actions include replacement of the 1B MFP servo and increased monitoring of speed oscillations.
VI.PREVIOUS SIMILAR EVENTS There have been no previous similar reportable events at CPNPP in the past three years.
4 4
Comanche Peak Nuclear Power Plant 445 23 001
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