Information Notice 1998-36, Inadequate or Poorly Controlled, Non-Safety-Related Maintenance Activities Unnecessarily Challenged Safety Systems

Inadequate or Poorly Controlled, Non-Safety-Related Maintenance Activities Unnecessarily Challenged Safety Systems

ML031040558
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	09/18/1998
From:	Roe J Office of Nuclear Reactor Regulation
To:
References
IN-98-036, NUDOCS 9809210079
Download: ML031040558 (7)

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~0- f9 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 September 18, 1998 NRC INFORMATION NOTICE 98-36: INADEQUATE OR POORLY CONTROLLED, NON-

SAFETY-RELATED MAINTENANCE ACTIVITIES

UNNECESSARILY CHALLENGED SAFETY SYSTEMS

Addressee

All holders of operating licenses for nuclear power reactors.

purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to alert

addressees to several recent events in which inadequate or poorly controlled, non-safety- related maintenance activities resulted in unnecessary challenges to safety systems. It is

expected that recipients will review the information for applicability to their facilities and consider

action, as appropriate to avoid similar problems. However, suggestions contained in this

information notice are not NRC requirements; therefore, no specific action or written response

is required.

Description of Circumstances

BRAIDWOOD UNIT 2

On January 18, 1996, with Braidwood Unit 2 operating at full power, .offsite power was lost.

Inadequately secured roofing repair materials located on the roof of the adjacent service

building were blown off the roof during a rain storm, causing a phase-to-ground arc on one of

two station auxiliary transformers (SATs). As designed, the second SAT tripped when the first

SAT failed. Both emergency diesel generators (EDGs) automatically started and all safe- shutdown loads automatically sequenced on to the engineered safety feature (ESF) buses. All

automatic bus transfers occurred as designed, maintaining power to non-ESF buses from the

unit auxiliary transformers (UATs). The reactor remained stable at full power throughout the

event. To restore offsite power to Unit 2, the licensee cross-tied both Unit 2 ESF buses to the

respective ESF buses of Unit 1, which also remained at full power throughout the event.

Inspection of the faulted SAT revealed damage to (1) the Phase B and C bushings and (2) a

gas detector relay on top of the transformer where heavy arcing occurred. The licensee

determined that the Initiating event was a Phase C arc-to-ground, followed by a Phase B to

vNOrT g NO -98T- goz 98 0e 8

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f IN 98-36 September 18, 1998 Phase C arc. A 345-kilovolt switchyard breaker, Which connected the SAT to the switchyard

ring bus, was also damaged. Approximately one square foot of the Phase B bushing was

blown out.

BYRON UNIT I

On May 23, 1996, with the Unit 1 reactor shut down In excess of a month for a refueling outage, offsite power was lost when one of the two Unit I SATs Isolated because of a Phase A to

Phase B current differential relay operation. The second SAT tripped as designed when the

first SAT failed. Both EDGs automatically started and all safe-shutdown loads automatically

sequenced on to the ESF buses. Because the reactor was shut down, power to non-ESF

buses was lost and two service water pumps and a station air compressor common to both

Byron units tripped. Without the service water pumps, Unit 2, which was operating at full

power, had no cooling water to many loads, including the main generator auxiliaries, station air

compressors, condensate pumps, and condensate booster pumps. Subsequently, Unit 2 was

manually tripped.

The licensee determined that the SAT that initially tripped underwent a phase-to-ground fault on

a Phase B insulator. The failed insulator was located outdoors, about halfway between the SAT

and the auxiliary building. After Initiating, the arc continued down the bus bar, Increasing in

width until It involved the other two phases. Air and water present in the bus bar duct was

heated by the arc and resulted in pressurization of the duct.

Chronic water leakage through inadequately caulked Insulator mounting holes and through an

improperly compressed gasket caused degradation of the insulator metal inserts and Insulator

material between these inserts. Eventually, the bus flashed to ground through the degraded

insulator and initiated the transient.

PERRY

On June 5, 1997, Perry was operating at full power when an automatic reactor scram occurred

following a three-phase fault in one of two high-voltage secondary winding termination

compartments of the UAT. The fault resulted in the actuation of the auxiliary transformer phase

differential relay, a main generator lockout, a main turbine trip, and fast closure of the turbine

control valves.

At the time of the transient, safety-related electrical loads were being supplied by the in-service

startup transformer. The non-safety-related electrical loads supplied by the transformer

automatically transferred to the startup transformer except for the bus that was faulted.

Operators stabilized the plant without major complication.

The licensee determined that the fault had developed as a result of an accumulation of moisture

and dust that had entered the termination compartment housing where a 2-Inch-long piece of

gasket material was missing from the compartment housing-to-transformer sealing surface.

The missing piece of gasket material may have been lost during work performed when

K>1 IN 98-36 September 18, 1998 replacing the auxiliary transformer following failure of the transformer on May 30, 1996. The

cause of that failure was attributed to Inadequate original design or poor assembly practices or

both.

POINT BEACH UNIT I

During a severe storm on January 8, 1998, a ground In the low-voltage-side bus duct caused

the failure of the Unit I SAT. This failure and a failure of the 13.8-kilovolt automatic bus transfer

to the Unit 2 SAT resulted in the loss of normal power to the Unit I safeguards buses. The

EDGs subsequently started and restored power to the buses. Unit I remained at 98 percent

power throughout the transient. Unit 2 was in cold shutdown.

The licensee attributed the failure of the transformer to the buildup of condensation internal to

the buses and long-term insulation degradation In the bus duct on the low-voltage side of the

transformer. Before the transformer failed, the circuit breaker for a heater designed to keep the

bus duct dry would not remain closed. Consequently, in August 1996, the licensee left the

circuit breaker open and wrote a work order for its repair. However, work schedulers did not

recognize that the bus duct heater was inoperable with the circuit breaker open, and the work

order was erroneously classified as "minor maintenance" and given low priority. At the time the

transformer failed, the work order was in the "backlog' of maintenance Items. In addition to the

inoperable heater, the:licensee determined that the lack of a routine inspection program for the

bus ducts may have contributed to the event. Inspection of the bus ducts after the transformer

failed revealed insulation breakdown that would likely have been Identified through a periodic

Inspection program.

Discussion

These events illustrate the potentially significant consequences of inadequate or poorly

performed maintenance activities on non-safety-related plant components. Unnecessary

challenges to plant safety systems or control room operators or both could result from

inadequate control or inattention to detail during non-safety-related maintenance activities. The

potential impact on safety systems of such activities as the re-roofing of nuclear power plant

support buildings, the Installation of gaskets, or the caulking of outdoor components, could

easily be overlooked. In addition, several of the events discussed here highlight the need for

licensees to have better control over the maintenance activities of contractor and non-station

utility employees, and the need for thorough periodic walkdowns or preventive maintenance on

auxiliary transformers and the associated outdoor bus ducts.

IN 98-36 September 18, 1998 This information notice requires no specific action or written response. However, recipients are

reminded that they are required to consider Industry-wide operating experience (including NRC

INs) where practical, when setting goals and performing periodic evaluations under Section

50.65, "Requirements for Monitoring the Effectiveness of Maintenance at Nuclear Power

Plants," of Part 50 of Title 10 of the Code of Federal Regulations. If you have any questions

about the information Inthis notice, please contact one of the technical contacts listed below or

the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

, Acting Director

eJack

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Mike Kunowski, Region IlIl John Neisler, Region IlIl

630-829-9816 630429-9718 E-mail: mak3@nrc.gov E-mail: jhn@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

A,(ttachment 1 IN 98-36 September 18, 1998 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

98-35 Threat Assessments and 914/98 All U.S. NRC fuel cycle facilities

Consideration of Heightened power and non-power reactor

Physical Protection Measures licensees (Safeguard issues, not

for public disclosure.)

98-34 NRC Configuration Control 8/28/98 All holders of Operating licenses

Errors for nuclear power reactors, except

for those who have ceased

operations and have certified that

fuel has been permanently

removed from the reactor vessel

98-33 NRC Regulations Prohibit 8128198 All holders of a U.S. Nuclear

Agreements that restrict or Regulatory Commission (NRC)

Discourage an Employee from license.

Participating In Protected Activities

98-32 Problems Associated with Post- 8126198 All holders of operating licenses

Fire Safe-Shutdown Circuit for nuclear power reactors, except

Analyses those who have permanently

ceased operations and have

certified that fuel has been

permanently removed form the

reactor

98-31 Fire Protection System Design 8/26/98 All holders of operating licences

Deficiencies and Common-Mode for nuclear power reactors, except

Flooding of Emergency Core Cooling those licensees that have

System Rooms at Washington Nuclear permanently ceased operations

Project Unit 2 and have certified that fuel has

been permanently removed from

the reactor vessel.

OL = Operating License

CP = Construction Permit

- IN 98-36 September 18, 1998 This information notice requires no specific action or written response. However, recipients are

reminded that they are required to consider industry-wide operating experience (including NRC

INs) where practical, when setting goals and performing periodic evaluations under Section

50.65, "Requirements for Monitoring the Effectiveness of Maintenance at Nuclear Power

Plants," of Part 50 of Title 10 of the Code of Federal Regulations. If you have any questions

about the information in this notice, please contact one of the technical contacts listed below or

the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

Jack W. Roe, Acting Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Mike Kunowski, Region IlIl John Neisler, Region IlIl

630-829-9816 630-829-9718 E-mail: mak3@nrc.gov E-mail: jhn@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

• See previous concurrence & e.

C,,tt

• • E-mail concurrence c<f()

DOCUMENT NAME: G:\NICK\REGION.IN

To receive a copy of this document, indicate in the box C=Copy wlo attachment/enclosure E=Copy with attachmentlenclosure N = No copy

OFFICE PECB I Tech EdI Reg III [ Regil I PECB I C:PECB l_ji D M

NAME NFields* RSanders* MKunowski** JNeisler** RDennig* JStolz* JRo

DATE 09/03/98 08/26/98 09/03/98 Ii09/03/98 09/14/98 J09/14/98 \/98 OFFICIAL RECORD COPY

IN 98-xx

September xx, 1998 This information notice requires no specific action or written response. However, recipie are

reminded that they are required to consider industry-wide operating experience (includ g NRC

INs) where practical, when setting goals and performing periodic evaluations under ection

50.65, "Requirements for Monitoring the Effectiveness of Maintenance at Nuclea ower

Plants," of Part 50 of Title 10 of the Code of Federal Regulations. If you have ny questions

about the information in this notice, please contact one of the technical con cts listed below or

the appropriate Office of Nuclear Reactor Regulation (NRR) project man er.

Jack W. Roe, Acting irector

Division of Reactor rogram Management

Office of Nuclea eactor Regulation

Technical contacts: Mike Kunowski, Region IlIl Joh eisler, Region IlIl

630-829-9816 63 -829-9718 E-mail: mak3@nrc.gov -mail: jhn@nrc.gov

Attachment: List of Recently Issued NRC Info tion Notices

DOCUMENT NAME: G:\NICK\REGION.IN

To receive a copy of this document, Indicate in the box C=Copy wlo attachmentenclosure E=Copy with attachmentlenclosure N = No copy

OFFICE PECB. I _ Tech Ed I _ Reg I lI _I Reg 11 l 1/E "ECB (A)D:DRPM l

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l DATE /3/98 1SW98 17/3/98 15/3198 lH/ 48 q/l98 l I /98 OFFICIAL RECORD COPY I