05000219/LER-2004-004
| Docket Number09 01 2004 2004 - 004 - 00 10 01 2004 | |
| Event date: | 09-01-2004 |
|---|---|
| Report date: | 10-01-2004 |
| 2192004004R00 - NRC Website | |
Description of Event
At 09:38 on September 1, 2004, a Plant Computer System (PCS) (El IS-ID) Isolator Power Supply (EIIS- RJX) failed. In accordance with procedures an administrative control rod block was inserted and all reactivity manipulations ceased. At 13:50, upon installation of a replacement PCS isolator Power Supply, the PCS heat balance indicated 1936 MWth that was in excess of the maximum steady state power limit of 1930 MWth for Oyster Creek. The Reactor Operator (RO) lowered reactor power to restore and maintain indicated heat balance power less than1930 MWth. At 15:00, a manual heat balance was calculated to verify the indicated Plant Computer System (PCS) Heat Balance.
Initial indications are that the PCS Isolator Power Supply began to degrade on August 29, 2004. This degradation resulted in a lowering of indicated Control Rod Drive (CRD) (EIIS-AA) Flow into the PCS Heat Balance calculation. There were no audible alarms as indicated CRD flow reduced. The computer generated PCS alarms at three setpoints on a display screen in the Main Control Room (MCR) with numerous other computer inputs that have changed state. The RO maintained indicated PCS heat balance slightly below 1930 MWth as expected. Reactor Recirculation System (EIIS-AD) flow adjustments to maintain slightly below 100% power were not abnormally high during the power supply degradation.
Based on evaluations of the degradation of the CRD Flow input to the heat balance, the 1930 MWth limit was exceeded on August 30, 2004 at 18:41. The peak power attained was 1937 MWth, approximately 100.4%, on Sept. 1, 2004. Since 1930 MWth was exceeded for more than eight hours, this event is reportable within 30 days under Operating License Condition 2.E as a violation of 2.C.(1), Maximum Power Level.
Analysis of Event
The significance of this event on plant safety was minimal since the actual peak sustained power level was less than the 102% reactor power assumed as initial conditions in updated facility safety accident report (UFSAR) analysis.
Cause of Event
Degradation of the power supply for PCS isolator cabinet PC-1.
Corrective Actions:
1. Reduced Reactor power to 2. Verified correct all computer inputs into the PCS Heat Balance.
3. Established a PCS Point Group for Heat Balance inputs that are being checked twice per shift per a new Operations Standing Order.
4. Briefed the operating crews on the event, highlighting the shortfalls identified and the importance of periodically confirming that PCS heat balance inputs are not in an alarm condition.
5. Failed power supply was replaced.
Corrective Actions (cont'd) 6.�Extent of condition was performed by verifying the operable condition of other PCS isolator power supplies.
Additional Information
A. Failed Components:
Degradation of the PCS isolator power supply.
B. Previous similar events:
None C. Identification of components referred to in this Licensee Event Report:
Components IEEE 805 System ID�IEEE 803A Function CAP ID� RJX