United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9804070202


LICENSEE EVENT REPORT (LER)
FACILITY NAME: Calvert Cliffs, Unit 1 PAGE: 1 OF 06
DOCKET NUMBER: 05000317
TITLE: Battery Charger Circuit Breakers Missing Seismic Positioner
EVENT DATE: 03/03/98 LER #: 98-004-00 REPORT DATE: 04/01/98
OTHER FACILITIES INVOLVED: Calvert Cliffs, U2 DOCKET NO: 05000318
OPERATING MODE: 1 POWER LEVEL: 100
THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR SECTION: 50.73(a)(2)(i)
LICENSEE CONTACT FOR THIS LER:
NAME: J. K. Kirkwood TELEPHONE: (410) 495-2013
COMPONENT FAILURE DESCRIPTION:
CAUSE: B SYSTEM: EK COMPONENT: BKR MANUFACTURER: W120
REPORTABLE NPRDS: Y
SUPPLEMENTAL REPORT EXPECTED: NO


ABSTRACT:

On March 3, 1998, we discovered that Calvert Cliffs No. 13 Battery Charger had been inoperable since the initial licensing of Unit 1. The 480-volt supply breaker (Breaker 52-1407) for the battery charger was installed in the plant without the required seismic positioner. On March 9, 1998, we discovered that the No. 14 Battery Charger 480-volt supply breaker (Breaker 52-1120) was missing the required seismic positioner, and the No. 14 Battery Charger had also been inoperable since the initial licensing of Unit 1. The breaker position indication and high voltage trip would probably be inoperable after a design basis seismic event. Both Units were operating at 100 percent power when the discovery was made.

The event investigation concluded that the seismic positioner had never been observed on either breaker. All safety-related 480-volt circuit breakers have been inspected. No other seismic positioners were missing.

END OF ABSTRACT


TEXT PAGE 2 OF 6

I. DESCRIPTION OF EVENT

On January 12, 1998, during the performance of routine periodic maintenance on the No. 13 Battery Charger 480 Volt breaker, the electrician performing the maintenance noticed that the breaker did not have a seismic positioner installed. The circuit breaker is a Westinghouse, safety-related, 480 Volt AC 'DS' style circuit breaker which supplies the No. 13 Battery Charger from the No. 14 480 Volt vital AC bus.

During the maintenance, the electrician noticed that the breaker looked different from the other Westinghouse safety-related, 480-Volt circuit breakers on which he had worked. Further investigation revealed that the breaker did not have a seismic positioner installed. A seismic positioner was obtained from a spare breaker, and installed on the No. 13 Battery Charger circuit breaker before the breaker was re-installed in its housing.

Westinghouse Electric Corporation was contacted to determine the operability of the circuit breaker, in this application, with the seismic positioner missing. on March 3, 1998, Westinghouse informed Plant Engineering that the circuit breaker probably would have sustained damage sufficient to render it inoperable in a seismic event. Therefore, the No. 13 Battery Charger was inoperable without the seismic positioner installed in the circuit breaker.

On March 9, 1998, all safety-related 480-Volt Westinghouse circuit breakers on site were inspected for the seismic positioner. During the inspection, the No. 14 Battery Charger 480-Volt circuit breaker was discovered to be missing the seismic positioner. A spare seismic positioner was obtained from a spare safety-related circuit breaker, and installed on the No. 14 Battery Charger circuit breaker.

Further investigation revealed that both Nos. 13 and 14 Battery Charger circuit breakers were probably installed without the seismic positioner installed during the construction of Unit 1.

The No. 13 Battery Charger supplies the No. 21 125 Volt DC bus with the No. 21 Battery Charger as a redundant power supply. The No. 14 Battery Charger supplies the No. 22 125 Volt DC bus with the No. 22 Battery Charger as a redundant power supply. Since the initial license of Unit 1, anytime either Nos. 21 or 22 Battery Chargers were removed from service, the Nos. 21 or 22 125 Volt DC busses were powered by an inoperable power supply.

125 Volt DC Bus Battery Chargers:

21 13 and 21

22 14 and 22


TEXT PAGE 3 OF 6

II. CAUSE OF EVENT

The root cause of this event was a quality issue related to the vendor. The Nos. 13 and 14 Battery Chargers, circuit breakers were both installed without the seismic positioners installed, but similar Westinghouse 480 Volt, safety related circuit breakers were installed with the seismic positioners in place.

The bolts that were in place where the seismic positioner should have been installed were too short to have held a seismic positioner. Therefore, it is ascertained that the seismic mount was not removed during maintenance. A review of the preventive maintenance of the breakers did not reveal an occurrence of any instance that would have necessitated the removal of the seismic positioner.

Westinghouse tracked the serial numbers of the breakers back to the lot that was shipped to Calvert Cliffs Nuclear Power Plant and determined that the shop order included directions to install the seismic positioner on the breakers.

No record of an observation of the seismic positioners could be found for either circuit breaker. The Technical manual supplied with the 480 Volt, safety-related, type 'DS' circuit breaker did not mention the seismic positioner as a component of the circuit breaker. The vendor has not issued any recommendation to perform inspections on this part of the breaker, and there are no current industry events related to the seismic positioners.

III. ANALYSIS OF EVENT

The 125 Volt DC and vital AC systems are designed to furnish continuous power to the plant vital instrumentation and control systems. The reliability of the system is increased by redundancy of vital equipment and circuits.

The 125 Volt DC and 120 volt vital AC systems for the plant are divided into four independent and isolated channels. Each channel consists of one battery, two battery chargers, one DC bus, multiple DC unit control panels, and two dual inverters. Each inverter has an associated vital AC distribution panelboard. Power to the DC bus, DC unit control panels, and dual inverters is supplied by the station batteries and/or the battery chargers. Each battery charger is fully rated and can recharge a discharged battery while at the same time supplying the steady state power requirements of the system.

125 Volt DC Busses 11 and 22 are a part of Load Group A, and 125 Volt DC Busses 12 and 21 are a part of Load Group B. The 125 Volt DC Bus 11 provides control power for equipment associated with Load Group A for both units. The 125 Volt DC Bus 21 provides control power for equipment associated with Load


TEXT PAGE 4 OF 6

Group B for both units. The 125 Volt DC Busses 12 and 22 are used to supply power to the computer inverters, Diesel Generator 1B control circuits, Control Room emergency lighting, and two channels of the 120 Volt vital AC inverters.

There is one battery charger fed from Unit 1 and another battery charger fed from Unit 2 connected to each 125 Volt DC bus. The AC power for both battery chargers per bus is obtained from the same load group.

The 125 Volt DC system has been designed to function properly while subjected to Safe Shutdown Earthquake accelerations.

During normal operation, all battery chargers are energized and maintain a constant voltage to supply the batteries with sufficient current to keep them fully charged and maintain the steady state load of DC instruments, control circuits, and inverters. In the event of loss of auxiliary system power, the batteries will continue to supply the required DC and vital AC equipment. When AC power is regained from the diesel generators, the battery chargers will be re-energized, and resume normal operation. The batteries are sized to supply the anticipated DC and vital AC load, without support from battery chargers, for a period of two hours.

Westinghouse conducted seismic testing on this type of breaker and found that the breaker did receive damage to the secondary couplers sufficient to disable the position indication and the high voltage trip. For a seismic event in which the breaker was damaged, we would have had up to two hours to replace the breaker based on the capacity of the battery.

The probability of having a design basis seismic event involving a demand for the emergency backup power, and the concurrent loss of Nos. 21 or 22 Battery Chargers is considered very small. In addition, the ability to manually close the battery charger supply breaker, replace the supply breaker if necessary, and the two hour capacity of the batteries further mitigates the potential consequences of this event. Therefore, this event did not result in a significant threat to the health and safety of the public.

This event is considered reportable in accordance with 10 CFR 50.73(a)(2)(i)(B); "Any event or condition prohibited by the plant's Technical Specifications." With a Unit in Mode 1, 2, 3, or 4, and one 125 Volt bus inoperable, Calvert Cliff's Technical Specification 3.8.2.3 Action a requires the following:

Restore the inoperable bus to OPERABLE status within two hours or be in at least HOT STANDBY within the next six hours and in COLD SHUTDOWN within the following 30 hours.


TEXT PAGE 5 OF 6

With a Unit in Mode 1, 2, 3, or 4, and both 125 Volt battery chargers from the same DC bus inoperable, Technical Specification 3.8.2.3 Action c requires:

Except when necessary during surveillance testing, restore at least one 125 Volt DC battery charger to OPERABLE status within two hours or be in at least HOT STANDBY within the next six hours and in COLD SHUTDOWN within the following 30 hours.
During surveillance testing, restore at least one 125 Volt DC battery charger to OPERABLE status within four hours or be in at least HOT STANDBY within six hours and in COLD SHUTDOWN within the following 30 hours.

With the Unit in Mode 5 or 6, and less than two 125 Volt DC busses operable, Technical Specification 3.8.2.4 requires the following actions:

a. Immediately suspend all operations involving CORE ALTERATIONS, positive reactivity changes, movement of irradiated fuel and movement of heavy loads over irradiated fuel until the minimum required DC equipment and busses are restored to OPERABLE status, and;
b. Immediately initiate corrective actions to restore the minimum DC equipment and busses to OPERABLE status, and;
c. All containment penetrations providing direct access from the containment atmosphere to the outside atmosphere shall be either closed by an isolation valve, blind flange, or manual valve, or be capable of being closed by an OPERABLE automatic purge valve. A minimum of one door in each air lock shall be closed and the equipment door shall be closed and held in place by a minimum of four bolts.

When the inoperability of the Nos. 13 and 14 Battery Charger supply breakers was discovered, both Unit 1 and Unit 2 were operating at 100 percent power. The Nos. 21 and 22 125 Volt DC busses were supplied by Nos. 21 and 22 Battery Chargers. The seismic positioners were installed before any actions were required.

IV. CORRECTIVE ACTIONS

A. We have inspected all safety-related Westinghouse 480 Volt Circuit Breakers to ensure that the seismic positioners are installed. No additional breakers were found to be missing seismic positioners.


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B. We have changed the Electrical Functional Test Procedures 52 and 53, for the Westinghouse 'DS' style circuit breaker to verify these seismic positioners are always installed on the circuit breakers.

V. ADDITIONAL INFORMATION

A. Component Identification
 
  IEEE 803 IEEE 805
Component EIIS Function System ID
Circuit Breaker 52-1120 BKR EK
Circuit Breaker 52-1407 BKR EK
 
B. There have been no previous reportable events involving seismic mounts on circuit breakers at Calvert Cliffs.
C. We have notified the industry of the missing seismic positioner via the Nuclear Network Operating Experience report system.
D. Number and location of Westinghouse 480 Volt 'DS' style circuit breakers:
Location Number of Breakers
U1 27' Switchgear 24
U1 45' Switchgear 24
U2 27' Switchgear 24
U2 45' Switchgear 24
1A Emergency Diesel Generator Building 4


ATTACHMENT TO 9804070202 PAGE 1 OF 1
 
BGE
Peter E. Katz Baltimore Gas and Electric Company
Plant General Manager Calvert Cliffs Nuclear Power Plant
Calvert Cliffs Nuclear Power Plant Plant 1650 Calvert Cliffs Parkway
Lusby, Maryland 20657
410 495-4101
April 1, 1998
U.S. Nuclear Regulatory Commission Washington, DC 20555
 
ATTENTION: Document Control Desk
SUBJECT: Calvert Cliffs Nuclear Power Plant
Unit Nos. 1 and 2; Docket Nos. 50-317 and 50-318;
License Nos. DPR 53 and DPR 69
Licensee Event Report 98-004
Battery Charger Circuit Breakers Missing Seismic Positioner

The attached report is being sent to you as required under 10 CFR 50.73 and 10 CFR 21.21 guidelines. Should you have questions regarding this report, we will be pleased to discuss them with you.

Very truly yours,

PEK/JKK/bjd

Attachment

cc: R. S. Fleishman, Esquire H. J. Miller, NRC
J. E. Silberg, Esquire Resident Inspector, NRC
A. W. Dromerick, NRC R. I. McLean, DNR
Director, Project Directorate I-1, NRC J. H. Walter, PSC


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