05000247/LER-2006-004, Regarding Automatic Actuation of Both Motor Driven Auxiliary Feedwater Pumps Due to Trip of 21 Main Feedwater Pump Caused by High Vibrations
| ML062970237 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  (DPR-026) |
| Issue date: | 10/23/2006 |
| From: | Dacimo F Entergy Nuclear Indian Point 2 |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-06-095 LER 06-004-00 | |
| Download: ML062970237 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(iv), System Actuation |
| 2472006004R00 - NRC Website | |
text
Indian Point Energy Center 450 Broadway, GSB P.O. Box 249 Buchanan, N.Y. 10511-0249 EntffgyTel (914) 734-6700 Fred Dacimo Site Vice President Administration October 23, 2006 Indian Point Unit No. 2 Docket No. 50-247 NL-06-095 Document Control Desk U.S. Nuclear Regulatory Commission Mail Stop O-P1-17 Washington, DC 20555-0001
Subject:
Licensee Event Report # 2006-004-00, "Automatic Actuation of Both Motor Driven Auxiliary Feedwater Pumps Due to Trip of 21 Main Feedwater Pump Caused by High Vibrations."
Dear Sir:
The attached Licensee Event Report (LER) 2006-004-00 is the follow-up written report submitted in accordance with 10 CFR 50.73. This event is of the type defined in 10 CFR 50.73(a)(2)(iv)(A) for an event recorded in the Entergy corrective action process as Condition CR-IP2-2005-05098.
There are no commitments contained in this letter. Should you or your staff have any questions regarding this matter, please contact Mr. Patric W. Conroy, Manager, Licensing, Indian Point Energy Center at (914) 734-6668.
- Srince, Fred R. Dacimo Site Vice President Indian Point Energy Center
Docket No. 50-247 NL-06-095 Page 2 of 2 Attachment: LER-2006-004-00 cc:
Mr. Samuel J. Collins Regional Administrator - Region I U.S. Nuclear Regulatory Commission U.S. Nuclear Regulatory Commission Resident Inspector's Office Resident Inspector Indian Point Unit 2 Mr. Paul Eddy State of New York Public Service Commission INPO Record Center
Abstract
On August 24, 2006, while performing a plant startup, the 21 Main Boiler Feedwater Pump (MBFP) tripped as a result of high vibration initiating the automatic actuation of both motor driven Auxiliary Feedwater Pumps (AFWP).
At the time of the event both AFWPs were in operation, both MBFP's isolated and the 22 MBFP was shutdown.
Operations was starting the 21 MBFP by rolling up the steam turbine.
During the turbine rollup the MBFP turbine was near the low end of the turbine critical speed while operators were transferring MBFP turbine control.
MBFP turbine vibration increased significantly during transition through the critical speed and the high vibration actuated one of the MBFP trip devices.
As a result of the MBFP trip, both motor driven AFW pumps received start signals.
The direct cause of the event was turbine vibration due to excitation of the turbine rotor and casing as a result of the rotor being near the turbine critical speed.
The apparent cause was weak procedural guidance in the main feedwater (FW) system operating procedure (SOP) which provided a critical speed that was too narrow.
Corrective actions include; a brief of operations on the event, a review for revision of the FW SOP to include a wider critical speed range and delay of turbine control transfer past the critical speed and to allow the MBFP turbine to be rolled on steam via Lovejoy controls past the critical speeds.
Necessary procedure revisions will be implemented.
The event had no effect on public health and safety.
NRC FORM 366 (6-2004)
(If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17)
Procedure 2-SOP-21.l will be reviewed for revision to provide a wider range for critical speed, and to allow the MBFP turbine to be rolled on steam via the Lovejoy startup station until past the critical speed range.
The procedure is scheduled to be reviewed and recommendations identified by November 22, 2006.
Necessary procedure revisions will be completed by December 29, 2006.
Event Analysis
The event is reportable under 10CFR50.73(a) (2) (iv)
(A).'
The licensee shall report any event or condition that resulted in manual or automatic actuation of any of the systems listed under 10CFR50.73(a) (2) (iv)
(B).
Systems to which the requirements of 10CFR50.73(a) (2) (iv)
(A) apply for this event include the AFWS.
This event meets the reporting criteria because the AFWS was actuated in accordance with design as a result of a trip of the 21 MBFP.
Past Similar Events A review of the past two years of Licensee Event Reports (LERs) for similar events that involved an ESF actuation identified one LER.
LER-2005-003 reported actuation of both motor driven AFW pumps due to the trip of the 22 MBFP on low lube oil pressure during swap of the in-service lube oil cooler.
The cause of LER-2005-003 was an inadequate MBFP lube oil system procedure (2-SOP-21.4) for venting the lube oil coolers.
The cause of this LER was weak procedural guidance in the main FW system operating procedure (2-SOP-21.I).
The corrective actions for this event were briefing operations and enhancement of the FW system operating procedure.
The corrective actions for LER-2005-003 were revision of the system operating procedure for the MBFP lube oil system.
Therefore, those corrective actions would not have prevented this event.
Safety Significance
This event had no effect on the health and safety of the public.
There were no actual safety consequences for the event because the AFWS was in operation and the MBFPs were not aligned to deliver flow to the SGs.
The SGs had adequate FW flow from the AFWS to maintain SG water level.
Operators had alarms/indications alerting them to MBFP trip and actuation of the AFWS and procedures to direct proper actions.
Operators during this event recognized the MBFP trip and took appropriate actions in accordance with plant procedures.
There were no significant potential safety consequences of this event under reasonable and credible alternative conditions.
Loss of FW at full power is a
credible alternative condition.
This event would be bounded by the analyzed event described in FSAR Section 14.1.9, Loss of Normal Feedwater.
A loss of one MBFP at power will result in a plant trip on low SG level if
operator action
does not correct the FW flow imbalance.
A Low-Low water level in any one SG initiates actuation of two motor-driven AFW pumps and a Low-Low water level in any two SGs actuates the steam driven AFW pump.
The AFW System has adequate redundancy to provide the minimum required flow assuming a single failure.
The analysis of a loss of normal FW shows that following a loss of normal FW, the AFWS is capable of removing the stored and residual heat plus reactor coolant pump heat, thereby preventing either over pressurization of the RCS or loss of water from the reactor coolant system and returning the plant to a safe condition.