05000255/LER-2008-001, Regarding Reactor Protection System and Auxiliary Feedwater System Actuation
| ML080720376 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 03/10/2008 |
| From: | Schwarz C Entergy Nuclear Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 08-001-00 | |
| Download: ML080720376 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(x) |
| 2552008001R00 - NRC Website | |
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Enlergy Nuclear Operations, Inc.
Palisades Nuclear Plant 27780 Blue Star Memorial Highway Covert, MI 49043 Tel269 764 2000 March 10, 2008 10 CFR 50.73(a)(2)(iv)(A)
U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Palisades Nuclear Plant Docket 50-255 License No. DPR-20 Licensee Event Report 08-001, Reactor Protection System and Auxiliary Feedwater System Actuation
Dear Sir or Madam:
Licensee Event Report (LER)08-001 is enclosed. 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 I 0 CFR 50.73(a)(2)(iv)(A).
Summarv of Commitments This letter contains no new commitments and no revisions to existing commitments.
Christopher J. Schwarz '
Site Vice President Palisades Nuclear Plant Enclosure (1 )
CC Administrator, Region Ill, USNRC Project Manager, Palisades, USNRC Resident Inspector, Palisades, USNRC
ENCLOSURE 1 LER 08- 001 Reactor Protection System and Auxiliary Feedwater System Actuation 3 Pages Follow
(9-2007)
LICENSEE EVENT REPORT (LER)
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 5: (Check all that apply)
C] 20.2203(a)(3)(i)
I7] 50.73(a)(2)(i)(C)
C] 50.73(a)(2)(vii)
I7] 50.73(a)(2)(ii)(A)
C] 50.73(a)(2)(viii)(A) 0 50.73(a)(2)(ii)(B)
C] 50.73(a)(2)(viii)(B)
C] 50.73(a)(2)(iii)
[7 50.73(a)(2)(ix)(A)
C] 20.2203(a)(2)(ii)
C] 50,36(c)(l)(ii)(A) 50.73(a)(2)(iv)(A)
C] 50.73(a)(2)(x)
C] 20.2203(a)(2)(iii)
C] 50.36(~)(2)
- 12. LICENSEE CONTACT FOR THIS LER ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines On January 13, 2008, with the plant in Mode 1 at 100% power, main feedwater pump P-1 B tripped unexpectedly. Operators entered the loss of main feedwater procedure and appropriately carried out the procedurally directed action to manually trip the reactor. As expected, the auxiliary feedwater system started automatically to recover steam generator level.
The immediate cause of the main feedwater pump trip was low lube oil pressure. The low lube oil pressure resulted from the loss of the main feedwater pump's shaft-driven lube oil pump, which occurred when its drive coupling became disengaged. An incorrect shaft key allowed the lower hub to slide down the shaft, making only partial engagement with the sleeve. The partial tooth engagement between the lower hub and sleeve was not sufficient to withstand the shaft torque, which ultimately resulted in stripping the splines on the coupling sleeve and decoupling the lube oil pump's shaft drive.
The lube oil pump was rebuilt, incorporating a design change that added a spacer beneath the lower hub to prevent the hub from sliding down the shaft and losing engagement with the coupling sleeve. The event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in an actuation of both the reactor protection system and the auxiliary feedwater system.
NRC FORM 366 (9-2007)
NRC FORM 366W U.S. NUCLEAR REGULATORY COMMISSION (9-2007)
LICENSEE EVENT REPORT (LER)
CONTIINUATllON SHEET PALISADES NUCLEAR PLANT
EVENT DESCRIPTION
On January 13, 2008, with the plant in Mode 1 at 100% power, main feedwater pump P-1 B [P;SJ]
tripped unexpectedly. Operators entered the loss of main feedwater procedure and appropriately carried out the procedurally directed action for loss of a main feed pump at >80% power, which is to manually trip the reactor [RCT;AB]. As expected, the auxiliary feedwater system [BA] started automatically to recover steam generator [SG;AB] level.
The event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in an actuation of both the reactor protection system [JC] and the auxiliary feedwater system.
CAUSE OF THE EVENT
The immediate cause of the main feedwater pump trip was low lube oil pressure. The low lube oil pressure resulted from the loss of the main feedwater pump's shaft-driven lube oil pump, which occurred when its drive coupling became disengaged.
The drive coupling is a vertically oriented sleeve, which mates upper and lower drive hubs. The inner surface of the sleeve is machined with splines to mesh with teeth that are machined on the outside surface of the drive hubs. The upper hub is secured to its shaft via an interference fit.
The lower hub is not an interference fit, and was previously secured by a key with a projection, which served to maintain the hub in vertical position by preventing the hub from sliding down its shaft past the projection.
Investigation revealed that the installed key for the lower hub did not have the desired projection.
At an unknown time in the past, the lower hub key was either replaced with one that had no projection, or the original projection on the key was removed. Pump component descriptions and drawings did not show the desired shape of the key, which allowed an incorrect key for this application to be installed. Without the correct key, the lower hub was able to slide down the shaft, making only partial engagement with the sleeve.
The partial tooth engagement between the lower hub and sleeve was not sufficient to withstand the shaft torque, which ultimately resulted in stripping the splines on the coupling sleeve and decoupling the lube oil pump's shaft drive. The partial engagement configuration existed from October 30, 2007, when the lube oil pump was installed and the main feedwater pump was placed in service, until,its failure on January 13, 2008.
IRC FORM 366A 3-2007)
U.S. NUCLEAR REGULATORY COMMUSSUON LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
CORRECTIVE ACTIONS
The lube oil pump was rebuilt, incorporating a design change that added a spacer beneath the lower hub to prevent the hub from sliding down the shaft and losing engagement with the coupling sleeve.
The feedwater pump work instructions will be upgraded to include detailed vendor drawings and information.
SAFETY SIGNIFICANCE
The event is considered to be of very low safety significance. All safety systems functioned as expected.
PREVIOUS SIMILAR EVENTS
None RC FORM 366A (9-2007)