05000341/LER-2009-001
| Docket Number03 28 2009 2009 -O001 -Oo00 05 22 2009 05000 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| Initial Reporting | |
| ENS 44942 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation |
| 3412009001R00 - NRC Website | |
Initial Plant Conditions:
Mode 1 Reactor Power 24 Percent
Description of the Event
At 0146 hours0.00169 days <br />0.0406 hours <br />2.414021e-4 weeks <br />5.5553e-5 months <br /> EDT March 28, 2009, the reactor mode switch [HS] was taken to shutdown in response to high vibration levels on the Main Turbine [TA] number 1 bearing. Reactor power had been reduced in preparation for a manual scram from below 25 percent power to enter into a unit Refueling Outage (RF13). The reactor protection system (RPS) [JD] performed as expected, and all rods were fully inserted into the core. Reactor water level reached a low of approximately 162 inches above top of active fuel and recovered to normal level automatically without operator intervention.
Reactor water level was maintained in the normal band of 173 to 214 inches with the Control Rod Drive System after the scram. Reactor pressure control was maintained by the turbine bypass valves. The peak Reactor Pressure was 965.3 psig, within normal pressure control limits. Reactor water Level 3 isolations occurred as expected.
There was no maintenance or testing in progress that would affect turbine vibration levels. Safety related plant equipment responded as expected to the manual reactor scram. At the time of the scram all Emergency Core Cooling Systems (ECCS) and Emergency Diesel Generators (EDGs) [DG] were operable.
Reactor water level was maintained above Level 2, and as expected, none of the primary containment isolations or safety injection systems initiations associated with Level 2 occurred. Safety related plant equipment responded as expected to the manual reactor scram.
The high turbine vibration was attributed to a High Pressure (HP) Turbine rub transversing bearing number 1. Cooling of the Moisture Separator Reheaters (MSRs) [SB] occurred early in the shutdown process, and it was determined that the rub was due to the MSR cool down process.
Significant Safety Consequences and Implications This event posed no significant safety implications because the reactor protection and safety related systems functioned as designed following the manual reactor trip. The transient was compared to the UFSAR transient analysis for the Manual Scram, and the actual response was enveloped by the UFSAR analysis.
This event is being reported under 10 CFR 50.73(a)(2)(iv)(A), as an event or condition that resulted in manual actuation of the reactor protection system and a reactor scram. A 4-hour non-emergency notification was made to the NRC Operations Center at 0345 EDT on March 28, 2009 (EN 44942) in accordance with 10 CFR 50.72(b)(2)(iv)(B) for an actuation of the reactor protection system.
Cause of the Event
The manual scram was inserted when turbine vibration levels on bearing #1 reached 15 mils during the shutdown for RF13. The high turbine vibration was due to a HP Turbine rub transversing bearing number 1.
By comparing the shutdown for RF13 with previous shutdowns and with other industry events where cooling of the MSRs occurred early in the shutdown process, it was determined that the rub was due to the MSR cool down process.
Operations personnel followed the system operating procedures (SOP) for the shutdown process.
Corrective Actions
The shutdown procedures will be reviewed in conjunction with vendor information and industry operating experience to determine potential procedure enhancement. Improvements will be made where applicable.
This event is documented and evaluated in the Fermi 2 corrective action program. Other actions are being considered to address this event. These actions will be tracked and implemented by the corrective action program
Additional Information
A. Failed Components: None B. Previous LERs on Similar Problems: None