Event Notification Report for April 12, 2006

UNIT 2 EXPERIENCED AN AUTOMATIC REACTOR TRIP FOLLOWING THE LOSS OF THE "2B2" REACTOR COOLANT PUMP

At 1335 EDT the Unit 2 Reactor tripped from 100% power on a Flux/Flow/Imbalance on two (2) RPS Channels "A" and "D." The initiating event was the trip of the "2B2" Reactor Coolant Pump (RCP) for unknown reasons. I & E Techs were working in the RCP Monitoring Cabinets at the time. Immediately following the RCP trip, Unit 2 commenced a runback as expected for approximately six (6) seconds before the RPS actuation occurred. All rods fully inserted with an anomaly noted for CRD [Control Rod Drive] Group 3 Rod 7 API [Absolute Position Indication] indicating approximately 21%, however, the PI [Position Indicating] Panel light was on. The licensee suspects that the problem is related to a reed switch for the API indication and not the actual rod position. Shutdown Margin has confirmed that the Reactor is subcritical. The Pressurizer Code Safeties and PORV did not lift during the transient.

Unit 2 is currently stable in Mode 3 discharging steam to the Main Condenser via the Turbine Bypass Valves using Main Feedwater for steam generator level control. Offsite power is available and stable. This event did not impact Units 1 or 3. RCP "2B2" will remain secured until the cause of the trip is identified and corrected. There is no known primary to secondary leakage for Unit 2. The licensee has completed EOP (Emergency Operating Procedure) subsequent actions.

The licensee informed the NRC Resident Inspector.

UF6 RELEASE DETECTION SYSTEM FAILED DURING TESTING

"At 0813 CDT on 04/12/2006, the Plant Shift Superintendent (PSS) was notified that immediately following routine test firing of the C-333 Unit 4 cell 7 UF6 Release Detection System (TSR surveillance requirement 2.4.4.1-1), smoke and sparks were observed coming from the UF6 Release Detection System control module and the system ready light was extinguished. The Area Control Room alarm locked in and the system was declared inoperable by the PSS. The cell and associated piping were above atmospheric pressure (Cascade Mode 2) at the time of the failure.

"The UF6 Release Detection System is a TSR system that is required to be operable per TSR 2.4.4.1, when a cascade cell and associated piping are in Cascade Mode 2. After discovery of failed system condition, a continuous UF6 smoke watch was initiated on the areas affected by the loss of detection capability in accordance with LCO Required Actions 2.4.4.1.B.1 and 2.4.4.C.1.

"This event is reportable as a 24 hour event in accordance with 10CFR 76.120(c)(2)(i). This is an event in which equipment is disabled or fails to function as designed when:

a.) the equipment is required by a TSR to prevent releases, prevent exposures to radiation and radioactive materials exceeding specified limits, mitigate the consequences of an accident, or restore this facility to a pre-established safe condition after an accident;

b.) the equipment is required by a TSR to be available and operable and either should have been operating or should have operated on demand, and

c.) no redundant equipment is available and operable to perform the required safety function.

"The NRC Senior Resident Inspector has been notified of this event.

"PGDP Problem Report No. ATRC-06-1197; PGDP Event Report No. PAD-2006-03."

There was no release from this event. The failure was shorted contacts in the alarm reset relay.

* * * UPDATE FROM WALLACE TO KNOKE AT 19:04 EDT on 04/18/06 * * *

"This report is being retracted. Subsequent to the event, Maintenance and System Engineering determined that the alarm disable switch control module faulted when the operator attempted to reset the ACR PGLD alarm. This fault caused the system power supply to fail. Resetting the alarms is the last step in the test procedure being performed when the failure occurred. Only after the alarms are cleared is the PGLD system returned to normal operating condition and testing complete. In this case, the evidence clearly indicated that the failure occurred during the conduct of the surveillance and the successful firing of the detectors and the start of the test provides positive evidence that the failure did not exist prior to the surveillance. Therefore, the in-service safety system failure reporting criteria of 10CFR 76.120(c)(2)(i) is not applicable.

"The Senior Resident Inspector has been notified of this retraction."

Notified R2DO(Lesser) and NMSS (Janosko).