05000255/LER-2019-001, Reactor Protection System and Auxiliary Feedwater System Actuation Due to Turbine Governor Valve Failure
| ML19059A082 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 02/28/2019 |
| From: | Hardy J Entergy Nuclear Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| PNP 2019-010 LER 2019-001-00 | |
| Download: ML19059A082 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 2552019001R00 - NRC Website | |
text
PNP 2019-010 February 28, 2018 ATTN: Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555-0001 Entergy Nuclear Operations, Inc.
Palisades Nuclear Plant 27780 Blue Star Memorial Highway Covert, MI 49043 Tel 269 764 2000 Jeffery A. Hardy Regulatory Assurance Manager 10 CFR 50.73
SUBJECT:
LER 2019-001 Reactor Protection System and Auxiliary Feedwater System Actuation due to Turbine Governor Valve Failure Palisades Nuclear Plant NRC Docket 50-255 Renewed Facility Operating License No. DPR-20 Entergy Nuclear Operations, Inc., hereby submits the enclosed Licensee Event Report (LER),
2019-001-00, for the Palisades Nuclear Plant. The LER describes a manual actuation of the reactor protection system and an automatic actuation of the auxiliary feedwater system. The occurrence is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A).
This letter contains no new commitments and no revisions to existing commitments.
Should you have any questions concerning this report, please contact Mr. Jeffery Hardy, Regulatory Assurance Manager, at (269) 764-2011.
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Enclosure:
LER 2019-001-00, Reactor Protection System and Auxiliary Feedwater System Actuation due to Turbine Governor Valve Failure CC Administrator, Region III, USNRC Project Manager, Palisades, USNRC Resident Inspector, Palisades, USNRC
ENCLOSURE PNP 2019-010 LER 2019-001-00, Reactor Protection System and Auxiliary Feedwater System Actuation Due to Turbine Governor Valve Failure 3 Pages Follow
NRC FORM 366 U.S. NUCLEAR REGULATORY APPROVED BY OMB: NO. 3150*0104 EXPIRES: 03/31/2020 (02-2018)
, the NRC may not conduct or sponsor, and a Derson is not reauired to resDond to the information collection.
- 1. Facility Name
~. Docket Number
- 3. Page PALISADES NUCLEAR PLANT 05000255 10F3
- 4. Title Reactor Protection System and Auxiliary Feedwater System Actuation due to Turbine Governor Valve Failure
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved Sequential Rev Facility Name Docket Number Month Day Year Year Number No.
Month Day Year
~5000 01 03 2019 2019
- - 001
- - 00 02 28 2019 Facility Name Docket Number
~5000
- 9. Operating Mode Abstract (Limit to 1400 spaces, i.e.* approximately 14 single-spaced typewritten lines)
On January 3, 2019, while the reactor was in mode 1 at 85% power, the linear variable differential transformer (LVDT) core on CV-0576, "High Pressure Turbine #4 Governor Valve," broke, causing uncontrolled cycling of the valve and an excursion in generator output. Upon control room notification of the uncontrolled movement of CV-0576, the operators placed the turbine controls in manual operation. However, CV-0576 proceeded to open and close independently of valve controls. Due to the inability to maintain positive control of CV-0576 manually, the operators manually tripped the reactor in accordance with site procedures. The required safety systems and shutdown equipment performed as expected, resulting in an uncomplicated trip. The condition was reported on January 3, 2019 (Event Number 53813) in accordance with 10 CFR 50.72(b)(2)(iv)(8) and 10 CFR 50.72(b)(3)(iv)(A) for a valid reactor protection system (RPS) actuation and an auxiliary feedwater (AF=W) actuation.
This condition is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as a condition that resulted in the actuation of both the RPS and the AFW.
The condition was attributed to a high-cycle fatigue failure of the LVDT core, which led to the uncontrolled movement of CV-0576.
Corrective actions were taken to replace the L VDT cores on all four governor valves before returning to power operations.
The investigation led to a corrective action to create preventative maintenance tasks to replace the governor valve L VDTs during normally scheduled actuator inspection and refurbishment. (04-2017) u.s. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1 022, R.3 for instruction and guidance for completing this form http://www.nrc..Qov/readinQ-rm/doc-coliections/nureas/staff/sr1 022/r3/\\
APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collectio,
- 3. LEA NUMBER YEAR PALISADES NUCLEAR PLANT 05000-255 2019
EVENT DESCRIPTION
SEQUENTIAL NUMBER
- - 001 REV NO.
- - 00 On January 3, 2019, at approximately 1900 EST, the reactor was in mode 1 at 85% power. Power output had been reduced to 85% during the previous shift to support isolation of level control valve [LCV] CV-0605, "Feedwater Heater E-6B Level Control," in order to perform emergent maintenance.
Later that day, at approximately 2009 EST, turbine [TRB] first-stage pressure began rising, ultimately producing a rise in net station electric output. As a result of the increased power output, the operators placed the turbine in runback in an attempt to return power to pre-event levels.
During the turbine runback, CV-0576 was observed to be cycling from what appeared to be 100% open to nearly 50% open within five minutes. The operators placed the turbine controls in manual to prevent any further valve movement. With the turbine controls in manual, CV-0576 proceeded to open and close in a similar manner as previously observed. Due to the inability to maintain positive control of CV-0576 while the digital electro-hydraulic (DEH) controls were in manual, the reactor was manually tripped in accordance with site procedures. The auxiliary feedwater system automatically actuated to recover steam generator level [SG], as designed. The plant was stabilized in a hot shutdown condition.
Troubleshooting identified that the linear variable differential transformer [XFMR] (LVDT) core had broken off the LVDT rod. All four LVDT governor valve cores were replaced. The plant was returned to service on January 5, 2019.
There were no other structures, systems, or components (SSCs) that were inoperable at the time that contributed to the event.
This condition is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as a condition that resulted in a valid actuation of both the reactor protection system and the auxiliary feedwater system.
Energy Industry Identification System (EllS) codes and component codes are identified in brackets above.
CAUSE OF THE EVENT
Failure of the LVDT core occurred at the threaded interface between the magnetic core and the non-magnetic push rod. The direct cause for the broken LVDT core on CV-0576 was high-cycle fatigue.
ASSESSMENT OF SAFETY CONSEQUENCES
The safety significance of the event was low. The fatigue limit of the threaded connection was reached after many cycles of operation. No specific vendor recommendation exists regarding replacement of the LVDTs.
LVDTs are typically replaced as a result of failure to calibrate or physical damage identified by personnel, but not due to fatigue failure concerns.
There were no consequences with regard to the safety of the public, nuclear safety, industrial safety, or radiological safety for this event.
CORRECTIVE ACTIONS
During troubleshooting, it was identified that the LVDT rod had split from the core. All four governor valve cores were replaced prior to plant restart on January 5, 2019.
A preventative maintenance task was created to periodically replace the governor valve LVDTs during future normally scheduled actuator inspection and refurbishment activities.
PREVIOUS OCCURENCES
A review of the Palisades Nuclear Plant (PNP) corrective action program database was completed. No similar events were previously identified involving LVDT core failure.