Event Notification Report for April 20, 1999

Postulated fire in the Auxiliary Feedwater room could affect diesel power to Safe Shutdown Equipment.

For a postulated fire in the north half of the Auxiliary Feed Water (AFW) Pump Room, the G-0l Diesel Generator is relied upon to provide emergency diesel power to Safe Shutdown Equipment. Without the fuel oil pump, there will only be enough fuel in the day tanks to run the diesel for 4 hours. This will not support maintaining Hot Shutdown of the units. The G-02 Diesel Generator will not be available due to loss of ventilation to the G-02 Diesel Room for room exhaust fan cables being located in the north half of the AFW Pump Room. The G-03 or G-04 Diesel Generators will not be available due to the potential loss of control circuitry and power feeds to transformers 1X-14 and 2X-14 being located in the north half of the AFW Pump Room as well.

The primary significance of this scenario is that in order to insure the proper Appendix R equipment is available for a fire in the north half of the AFW Pump Room the 1A-05 bus must have power. Provisions must be made to maintain G-01 as that supply source or qualify another source such as G-05 Gas Turbine. Without G-01 availability, this places the plant outside of design basis for Appendix R.

Compensatory actions at this time are twice per shift (8 hour shift) Appendix R fire inspections.

The licensee is looking into using the Gas Turbine, G-05, or locally starting the G-03 Diesel Generator.

The NRC Resident Inspector will be informed of this notification by the licensee.

- Aux Bldg Vent Systems may not meet their safety and accident mitigation function during accident conditions -

The licensee reviewed the Auxiliary Building Ventilation Systems as part of the Expanded System Readiness Reviews (ESRRs). The scope of the ventilation review included the Engineered Safety Features (ESF) Ventilation, known as Auxiliary Equipment Subsystem (AES), which is the focus for this report.

The AES safety and accident mitigation function is to provide sufficient cooling to the general areas and safety related equipment rooms required to operate during accident conditions for multiple safety related systems, including Component Cooling Water System, Containment Spray System, Residual Heat Removal System, Charging System, and Safety Injection System.

As a result of the ESRR, it has been concluded that currently there is insufficient assurance that the AES is capable of meeting its safety and accident mitigation function for temperature control of the Auxiliary Building in its present configuration. This conclusion is based on significant errors that were identified in ventilation related temperature calculations for the Auxiliary Building, combined with the small margin that previously existed between calculated results and design requirements, such that there is little assurance of adequate auxiliary building room cooling for ESF equipment. In addition, the AES dampers are not single failure proof (as previously reported) and the system lacks missile protection between trains.

Both units are currently in Operational Mode 5 (Cold Shutdown). Priority evaluation of these issues, including determination of the need for physical modifications, is ongoing and will be resolved prior to startup of the units.

The licensee notified the NRC Resident Inspector.

- AUTO REACTOR SCRAM FROM 100% POWER DUE TO LOSS OF MAIN FEEDWATER; ECCS INJECTION -

AT 1832 ON 04/20/99, WITH UNIT 1 AT 100% POWER, ALL EIGHT CONDENSATE SYSTEM DEEP BED DEMINERALIZER OUTLET MOTOR OPERATED VALVES FAILED CLOSED POSSIBLY DUE TO A COMPUTER MALFUNCTION. THE DEMINERALIZER BYPASS VALVES TRIPPED DUE TO THERMAL OVERLOADS AND FAILED TO OPEN, CAUSING ALL THREE STEAM DRIVEN MAIN FEEDWATER PUMPS TO TRIP. THE REACTOR VESSEL WATER LEVEL DROPPED FROM A NORMAL LEVEL OF +35 INCHES TO +12.5 INCHES, CAUSING THE REACTOR TO AUTOMATICALLY SCRAM FROM 100% POWER DUE TO LOW REACTOR VESSEL WATER LEVEL. ALL CONTROL RODS INSERTED COMPLETELY; HOWEVER, ROD #30-39 INSERTED SLOWLY. NO SAFETY/RELIEF VALVES LIFTED. STEAM IS BEING DUMPED TO THE MAIN CONDENSER.

REACTOR VESSEL WATER LEVEL FURTHER DROPPED TO -38 INCHES, CAUSING THE HIGH PRESSURE COOLANT INJECTION (HPCI) AND THE REACTOR CORE ISOLATION COOLING (RCIC) SYSTEMS TO ACTUATE AND INJECT INTO THE REACTOR VESSEL. THE REDUNDANT REACTIVITY CONTROL SYSTEM INITIATED TO TRIP THE CIRCUIT BREAKERS FOR THE REACTOR RECIRCULATION PUMPS. PRIMARY CONTAINMENT ISOLATION SYSTEM GROUPS 1B, 2A, 2B, 2C, 3, 6A, 6B, 6C, 7B, AND 8B ISOLATED. THE DIVISION 'A' ATWS/RPT CIRCUIT BREAKER FOR THE 'A' RECIRC MOTOR GENERATOR SET FAILED TO TRIP, AS REQUIRED. SMOKE WAS OBSERVED TO BE COMING FROM THE BREAKER. THE BREAKER WAS MANUALLY TRIPPED FROM THE CONTROL ROOM AND THE SMOKING STOPPED. THE 'A' AND 'B' RECIRC MOTOR GENERATOR SET DRIVE MOTOR CIRCUIT BREAKERS ALSO FAILED TO TRIP ON THE 13 kV BUS FAST TRANSFER. THE BREAKERS WERE MANUALLY TRIPPED.

REACTOR VESSEL WATER LEVEL DROPPED TO A LOW LEVEL OF -75 INCHES ABOUT 40 SECONDS INTO THE EVENT (TOP OF ACTIVE FUEL IS -161 INCHES). THE HPCI AND RCIC SYSTEMS RECOVERED REACTOR VESSEL WATER LEVEL TO +25 INCHES, AT WHICH TIME CONTROL ROOM OPERATORS MANUALLY SECURED THE HPCI SYSTEM. THE RCIC SYSTEM IS MAINTAINING REACTOR VESSEL WATER LEVEL AT +25 INCHES WITH REACTOR PRESSURE AT 875 PSIG AT AN INJECTION RATE OF 300 GPM.

PLANT OPERATORS ENCOUNTERED A PROBLEM WITH THE AUXILIARY STEAM SYSTEM AND THE MECHANICAL VACUUM PUMP. THEY MANUALLY CLOSED THE MAIN STEAM ISOLATION VALVES. THEY ARE CONTROLLING REACTOR VESSEL WATER LEVEL WITH THE RCIC SYSTEM AND REACTOR COOLANT SYSTEM PRESSURE WITH THE HPCI SYSTEM.

UNIT 1 IS STABLE IN OPERATIONAL CONDITION 3 (HOT SHUTDOWN) AND COOLING DOWN TO COLD SHUTDOWN. PRIMARY CONTAINMENT PARAMETERS ARE NORMAL. THERE WAS NO RELEASE OF RADIOACTIVE MATERIAL. RELEASE RATES ARE NORMAL. THIS EVENT HAD NO IMPACT ON UNIT 2 WHICH IS IN OPERATIONAL CONDITION 5 IN A REFUELING OUTAGE.

THE LICENSEE NOTIFIED THE NRC RESIDENT INSPECTOR AND IS INVESTIGATING THIS EVENT. THEY PLAN TO ISSUE A PRESS RELEASE.

*** UPDATE ON 4/21/99 @ 0418 BY HUNTER TO GOULD ***

THE REACTOR IS IN OPCON 3 AT 350 PSIG CONTINUING TO COLD SHUTDOWN. CONDENSER VACUUM IS BEING REESTABLISHED IN ORDER TO RE-OPEN THE MSIVs AND SECURE HPCI FROM PRESSURE CONTROL MODE. FEEDWATER SYSTEM IS BEING REPRESSURIZED TO REESTABLISH NORMAL FEED AND SECURE RCIC FROM LEVEL CONTROL MODE.

ALSO THE "1A" AND "1B" MG SET DRIVE MOTOR BREAKERS DID NOT TRIP DURING THE TRANSIENT SINCE PLANT LOADS WERE PREVIOUSLY TRANSFERRED BY A REACTOR OPERATOR PRIOR TO THE TURBINE TRIP. THE BREAKERS, THEREFORE, OPERATED AS DESIGNED.

THE RESIDENT INSPECTOR WAS NOTIFIED.

THE REG 1 RDO(SHANBAKY) WAS NOTIFIED.

*** UPDATE ON 4/22/99 @ 0220 BY HUNTER TO GOULD ***

THE UNIT IS IN COLD SHUTDOWN AS OF 2214 ON 4/21/99. RESOLUTION OF EQUIPMENT PROBLEMS WHICH RESULTED IN THE SHUTDOWN ARE IN PROGRESS. ACTIVITIES ARE ALSO IN PROGRESS FOR PLANT STARTUP.

ALL CONTROL RODS INCLUDING 30-39 WENT FULL IN WITHIN THE REQUIRED TECHNICAL SPECIFICATION TIME. ROD 30-39 POSITION INDICATION WAS LOST FOR APPROXIMATELY TWO MINUTES AFTER THE SCRAM, THEN THE "00" FULL IN POSITION INDICATION BECAME AVAILABLE AND REMAINED AVAILABLE THROUGHOUT THE SHUTDOWN.

THE RESIDENT INSPECTOR WILL BE INFORMED. THE REG 1 RDO(SHANBAKY) WAS INFORMED.