Event Notification Report for January 31, 2001

OFFSITE NOTIFICATION - SEWAGE SPILL

At approximately 1400 CST on 01/31/01, an untreated sewage spill, overflowing from an underground manhole cover, of approximately 200 gallons occurred outside of the Generation Support Building. The sewage spilled into the storm drains which drain into East Creek. The spill has been isolated and contained. The spill occurred outside the Protected Area but remained inside the Owner Controlled Area during the event with no spillage reaching the Mississippi River. The Louisiana Department of Environmental Quality was notified by River Bend personnel at
1451.

POTENTIAL INABILITY TO CONTROL A RADIOACTIVE RELEASE

At 1145 on 1/31/01, the door to the auxiliary engineered safeguards suction side vestibule in unit 2 was found stuck open. This bypasses the normal flowpath for both trains of ESF fans and renders them inoperable. The plant made an unrecognized entry into Technical Specification 3.0.3 until the door could be closed, which occurred in approximately one minute. This eight hour report is being made in accordance with 10 CFR 50.72 based on the temporary inability to control a possible radioactive release.

The licensee notified the NRC resident inspector.


* * * UPDATE AT 1543 ON 3/21/01, BY CHERBA RECEIVED BY WEAVER * * *

The licensee has retracted this event based on the following analysis.

"Subsequent evaluation concluded that if a postulated accident had occurred while the door was open, control room doses would be less than 10CFR Appendix A, GDC-19 limits and site boundary doses would remain within CNP's accident analysis assumptions. This conclusion is based on an actual measured total ECCS unfiltered leakrate of 0.02292 gpm, which is less than the CNPs established limit of 0.2 gpm via the unit vent stack. Since the total leakrate is less than 0.2 gpm, the AES system is not required to filter the building effluent to maintain control room habitability during a postulated accident. In addition, it was concluded that the ECCS pump and heat exchanger rooms would not have experienced temperatures greater than previously evaluated if a postulated accident had occurred while the door was open. This was due primarily because of the low supply air temperature (28 degrees Fahrenheit) and near freezing lake water temperature.

"Based on the above, this event would not have impacted the radiation removal capability of the AES ventilation system. As such, this notification is being made to retract event 37706 made on January 31, 2001."

The licensee informed the NRC resident inspector. The operations center notified the R3DO (Shear).

UNIT 1 EXPERIENCED AN AUTOMATIC REACTOR SCRAM FOLLOWING FAILURE OF A MAIN POWER TRANSFORMER

"At 21:47 CST, U-1 automatically scrammed from a main turbine 'NON-EHC' trip caused from a failure of a main power transformer. The main power transformers received an auto deluge signal and an acrid smell is reported in the area. The main generator tripped from the loss of the main power transformer causing the main turbine to trip, which caused an automatic reactor scram. The fast closure of the main turbine valves caused a reactor pressure spike which tripped both reactor recirculation pumps and caused two safety relief valves to actuate.

"All automatic actions initiated as designed, but the following anomalies were noted;

- 1A circulating water pump tripped
- Division 1 alternate rod insertion failed to reset on scram recovery
- 1B recirculation pump received a low oil level alarm on restart attempt
- U2 received an electrical perturbation from the U1 scram which resulted in a loss of the 2A heater drain pump and two heaters. Cram rods were inserted in accordance with Operating procedures. U2 was stabilized at 930 MWE."

All rods fully inserted. The two safety relief valves reseated after actuation. Decay heat is currently being removed via the bypass valves to the main condenser. RCIC is inoperable but available, if needed. There are no challenges to offsite power and the system auxiliary transformer is fully available. The licensee is presently resetting the deluge system in order to assess if there is mechanical damage on the 1 west main power transformer and will determine whether a U-1 cooldown is required to evaluate the 1B recirculation pump problem. The NRC resident inspector was informed and is currently onsite.

* * * UPDATE AT 2007 EST ON 2/1/01 BY SHANE MARIK TO FANGIE JONES * * *

"This is a follow up notification to event #37707 to enhance and clarify plant response following the post scram investigation. It was determined that a bushing/insulator failure on the 'C' phase of the 1 West Main Power Transformer failed causing the lockout of the main generator. The failed bushing/insulator is not located directly on the 1 West Main Power transformer but is located on the first main tower between the transformer and the switchyard.

"During the turbine trip and reactor scram the reactor vessel level instrumentation spiked causing a 'ringing phenomenon' initiated from the increase in pressure. This phenomenon was identified from the transient analyses data and seen during previous pressure transients. The ringing in the level instrumentation caused varying level indication (<1/2 second cycles) which is indication only, not a real change in reactor level. This ringing phenomenon caused to the actuations and 1/2 isolations identified during the scram.

"The following is offered to clarify the anomalies identified during the event.
1. The main steam isolation valves received a 1/2 group one isolation due to the ringing phenomenon.
2. Reactor recirculation pumps tripped off due to the ringing phenomenon.
3. Four safety relief valves opened. Previously reported as two. All four safety relief valves re-closed properly.
4. Reactor building ventilation tripped due to the inboard isolation dampers closing on low voltage transient.
5. The main generator voltage regulator failed to auto transfer to manual.
6. A division one ground was received and was subsequently isolated to three alarm points associated with the main power transformers which received a deluge on the bushing fault."

The licensee notified the NRC Resident Inspector. The R3DO (David Hills) has been notified.

INVALID ACTUATION OF THE "A" EMERGENCY DIESEL GENERATOR

On January 31, 2001 at 1559 while performing an air roll of the "A" Emergency Diesel Generator (EDG) as part of the restoration of the EDG to an operable status, the EDG started. This occurred because the fuel racks were not properly tripped as required by the operating procedure. The operator had attempted to trip the fuel racks, but did not hit the trip button with sufficient force to trip the racks. As a result the EDG started and came up to speed, but the EDG did not progress through the loading sequence since there was no loss of power. Control Room personnel were immediately notified and the EDG was properly shutdown by initiating an emergency trip from the Control Room.

The actuation of the EDG occurred due to human error and procedural inadequacy and was not due to actual plant conditions. Therefore, the actuation was not a valid actuation. The "A" EDG had been declared inoperable under Technical Specification 3.8.1.1.b to perform a six hour loaded run. 10CFR50.73(a)(2)(iv) excludes reporting an invalid actuation if the equipment is properly taken out of service. However, the EDG was "not properly taken out of service" at the time as described in NUREG-1022 to qualify for the exclusion to reporting the invalid actuation. Although the EDG had been declared inoperable, it was still "available". If an Engineered Safeguards Actuation System (ESAS) signal had occurred, the EDG would have been available to perform its function. In order to qualify for the exclusion from reporting this invalid actuation, the undervoltage start capability from ESAS would have to have been defeated, the flow of fuel to the EDG stopped, or other appropriate action taken. Therefore, this event is reportable as a 60-day ENS phone call.

The NRC Resident Inspector was notified.