05000315/LER-2008-001, Regarding Unit 1 Manual Reactor Trip Due to Main Turbine Vibrations
| ML080950124 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 04/01/2008 |
| From: | Peifer M Indiana Michigan Power Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| AEP:NRC:2573-43 LER 08-001-00 | |
| Download: ML080950124 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3152008001R00 - NRC Website | |
text
INDIANA MICHIGAN Indiana Michigan Power POWER One Cook Place Bridgman, MI 49106 A unit ofAmerican Electric Power Indiana Mic higa nPower.com April 1, 2008 AEP:NRC:2573-43 10 CFR 50.73 Docket No. 50-315 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop O-PI-17 Washington, DC 20555-0001 Donald C. Cook Nuclear Plant Unit I LICENSEE EVENT REPORT 315/2008-001-00 UNIT I MANUAL REACTOR TRIP In accordance with the criteria established by 10 CFR 50.73, -Licensee Event Report System, the following report is being submitted:
LER 315/2008-001-00: "Unit I Manual Reactor Trip."
There are no commitments contained in this submittal.
Should you have any questions, please contact Mr. James M. Petro, Jr., Regulatory Affairs Manager, at (269) 466-2491.
Sinerely Site Vice President JEN/rdw Attachment 4E~
U. S. Nuclear Regulatory Commission AEP:NRC:2573-43 Page 2 c:
J. L. Caldwell - NRC Region III K. D. Curry - AEP Ft. Wayne, w/o attachment INPO Records Center J. T. King - MPSC, w/o attachment MDEQ - WHMD/RPS, w/o attachment NRC Resident Inspector P. S. Tam - NRC Washington DC
NRC Form 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB:
NO. 3150-0104 EXPIRES 08/31/2010 (9-2007)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Donald C. Cook Nuclear Plant Unit# 1 05000-315 1 of 4
- 4. TITLE Unit 1 Manual Reactor Trip due to Main Turbine Vibrations
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL REVISION FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NUMBER MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 02 02 2008 2008 001 00 04 01 2008
- 9. OPERATING MOD11.
THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
C3 20.2201(b)
E] 20.2203(a)(3)(i)
[I 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii)
[ _1 20.2201(d)
[] 20.2203(a)(3)(ii)
E] 50.73(a)(2)(ii)(A)
E] 50.73(a)(2)(viii)(A)
E] 20.2203(a)(1)
E] 20.2203(a)(4)
E] 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
E] 20.2203(a)(2)(i)
[E 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii)
E] 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii)
- ] 50.36(c)(1)(ii)(A)
Z 50.73(a)(2)(iv)(A)
[] 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
E] 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71(a)(4) 93 %
El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B) 73.71 (a)(5)
El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
U OTHER Specify in Abstract below El 20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D) or in (If more space is required, use additional copies of NRC Form (366A)
Conditions Prior to Event
The reactor was at 93% power with a power reduction in progress in response to rising main turbine vibrations.
Description of Event
On February 2, 2008, at 0530 hours0.00613 days <br />0.147 hours <br />8.763227e-4 weeks <br />2.01665e-4 months <br />, Donald C. Cook Nuclear Plant Unit 1 operators initiated a manual reactor trip from 93% power due to main turbine high vibrations reaching the manual trip setpoint.
All control rods fully inserted and the Auxiliary Feedwater System (AFW)
[BA] started automatically and performed as designed.
The electrical buses transferred normally to Reserve Feed and bus voltage was maintained as required.
The main turbine was operating with elevated bearing vibration levels of approximately 8.5 mils.
This vibration level is acceptable for continued operation and is below the high vibration annunciator setpoint.
The setpoint value varies and is field set (typically 2 mils above the nominal observed value for each bearing).
Both operating Non-Essential Service Water [KG]
(NESW) pumps' strainers automatically backwashed at the same time resulting in a lower NESW header pressure which caused an automatic start of the two standby NESW pumps.
A lake temperature drop, combined with the auto-starts of the two standby NESW pumps while Main Turbine Lube Oil [LL]
(MTLO) temperature control was in manual (the temperature control valve was not functioning in automatic control), resulted in an unintentional cooldown of MTLO.
This MTLO cooldown contributed to oil whirl/whip and rising bearing vibration.
Bearing vibration increased from 8.5 mils to 10.5 mils over a 2-hour period. Operators took appropriate actions in accordance with plant procedures to warm MTLO, within the normal band, from 111 degrees to 115 degrees.
This had no effect on vibration.
The crew commenced lowering power level from 100% in an attempt to lower vibration.
At 93% power vibration levels increased to the manual trip setpoint of 13.8 mils and the operators performed a manual reactor trip The reactor trip was uncomplicated and all major plant components functioned as designed.
The reactor trip was reported in accordance with 10 CFR 50.72(b) (2) (iv) (B) and the AFW actuation was reported in accordance with 10 CFR 50.72(b) (3) (iv) (A).
The reactor trip and AFW actuations are reportable as a Licensee Event Report (LER) in accordance with 10 CFR 50.73(a) (2) (iv) (A).
Cause of Event
An unintentional cooldown of Main Turbine Lube Oil (MTLO) induced an oil whip condition that exacerbated main turbine bearing vibrations.
Contributing causes were 1) the non-functioning oil temperature control valve which contributed to an oil temperature excursion and 2) bearings 5 and 6 being loaded more lightly than the other bearings.
(if more space is required, use additional copies of NRC Form (366A)
Analysis of Event
Review of pertinent control room logs and post-trip review documentation indicate that:
No risk significant plant equipment was unavailable at the time of the unit
- trip, or failed following the trip, All reactor and secondary plant equipment functioned as designed without challenging plant safety, Plant electrical buses remained energized by offsite electrical power following the trip,
- and, Operator actions were appropriate in responding to the elevated main turbine vibration, executing actions to trip the unit, and monitoring and controlling the post-trip plant response.
Thus, the manually initiated unit trip resulted in no significant risk to the plant or surrounding population.
Corrective Actions
Balance weights were added to the main turbine rotor to return vibration to normal levels.
Actions to repair the oil temperature control valve are in the station work control process.
Operations has instituted a compensatory measure to run three NESW pumps in order to enhance NESW system stability and provide operating margin from a NESW pump auto-start due to low header pressure.
This compensatory measure shall remain in place until additional corrective actions to address system stability are completed.
Actions are in the station work control process to adjust NESW pump setpoints for automatic start on low pressure and strainer backwash to set them differently between units in order to minimize the potential for simultaneous automatic starts.
Evaluation of critical data testing of the main turbine which was performed during
.a subsequent shutdown (refueling) is being performed.
Following this evaluation, additional actions will be initiated as appropriate, including revision of the causal analysis if necessary.
(If more space is required, use additional copies of NRC Form (366A)
Previous Similar Events
The following LERs identify reactor trip events in the past three years.
The causes of these reactor trips were not similar in nature to the cause of this trip.
05000316/2005-001-00 Reactor Trip from RCP Bus Undervoltage Signal Complicated by Diesel Generator Output Breaker Failure 05000315/2007-001-00 Reactor trip from low Steam Generator water level coincident with a steam flow -
feedwater flow mismatch