Information Notice 1997-01, Improper Electrical Grounding Results in Simultaneous Fires in the Control Room and the Safe-Shutdown Equipment Room

Improper Electrical Grounding Results in Simultaneous Fires in the Control Room and the Safe-Shutdown Equipment Room

ML031050393
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:	01/08/1997
From:	Martin T Office of Nuclear Reactor Regulation
To:
References
IN-97-001, NUDOCS 9701030090
Download: ML031050393 (10)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001

• January 8, 1997 NRC INFORMATION NOTICE 97-01: IMPROPER ELECTRICAL GROUNDING RESULTS IN

SIMULTANEOUS FIRES IN THE CONTROL ROOM

AND THE SAFE-SHUTDOWN EQUIPMENT ROOM

Addressees

All holders of operating licenses or construction permits for nuclear power reactors.

Purpose

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

addressees to potential component grounding problems that could result in simultaneous

fires. It is expected that recipients will review the information for applicability to their facilities

and consider actions, 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

At approximately 5:00 p.m. on April 4, 1996, during a refueling outage, a licensee firewatch

detected smoke in the back panel area of the control room at the Palo Verde Nuclear

Generating Station, Unit 2. Licensee operators observed smoke emanating from the Train B

emergency lighting uninterruptible power supply (ELUPS) panel in the control room.

The fire in the control room resulted in loss of power to Train B control room emergency

lighting circuits, some general plant essential lighting and plant fire detection and alarm

system panels. Lighting powered by the unaffected Train A lighting system was sufficient to

operate the unit. The circuit breaker supplying power to the ELUPS panel tripped open when

wiring insulation in the conduit supplying the power supply panel melted and caused various

conductors to short circuit. The circuit breaker trip also deenergized power to the fire

detection and alarm panels in the auxiliary building. When operators checked the control

room fire alarm annunciator monitor, they noted that a large number of fire detector trouble

alarms were alarming and that the alarms were scrolling on the monitor screen as a result of

the deenergized fire detection and alarm panels.

The control room staff dispatched auxiliary operators to inspect their assigned areas to check I

for possible fire conditions and additional problems. An auxiliary operator discovered smoke

and fire in the Train B dc equipment room on the 100-foot level of the auxiliary building. The

fire was located in the 480/120-volt essential lighting isolation transformer. The trouble

alarms resulting from the lost power supply masked the actual fire alarm in the Train B dc

equipment room. J t-

9701030090 LA Ad pi

Ps E o48c. St .Ol r

IN 97-01 January 8, 1997 The licensee's onsite fire department responded and all fires were extinguished within a short

period of time. The licensee established the required compensatory firewatches in areas with

disabled fire detectors. Actual equipment damage was limited to the components involved in

the fires.

Discussion

The licensee's root-cause investigation indicated that the core of the regulating isolation

transformer (located in the Train B dc equipment room) failed and made contact with the

transformer coils, causing a short circuit fault to station ground through the transformer's

panel ground. The purpose of the subject transformer is to isolate nonsafety-related portions

of the circuit from the safety-related function of the circuit. The investigation also determined

that the neutral leg of the transformer had not been grounded. An alternate source of power

for the essential lighting uninterruptible power supply panel is provided by an inverter. The

system had been designed with ground connections on the neutral leg of the inverter instead

of grounding the neutral leg of the power supply (regulating transformer) in accordance with

industry practice. The neutral wiring conductors within the inverter and from the inverter to

the essential lighting distribution panel became the return fault path to the regulating

transformer. These conductors were not designed to handle the high fault currents to which

they were subjected. As a result, these wires ignited under these high fault currents. These

components are depicted in Figure 1. The licensee also determined that the fires were

related and were caused by a design error in the electrical grounding, which dated back to

plant construction. The licensee found similar grounding arrangements in the other two

Palo Verde units.

The final safety analysis report for the facility documented that grounding was accomplished

in accordance with Institute of Electrical and Electronics Engineers (IEEE)

Standard 142-1982, "Grounding of Industrial and Commercial Power Systems." The

transformer and equipment supplied by the transformer was designed as a grounded system.

IEEE 142-1982 defined a grounded system as a system of conductors in which at least one

conductor or point (usually the middle wire or neutral point of the transformer or the

generator windings) is intentionally grounded. The licensee also indicated that the grounding

design for Palo Verde was in accordance with Bechtel Drawing 13-E-ZVG-007, "Grounding

Notes, Symbols, and Details," Revision 20. The document did not require grounding of the

transformer's neutral leg.

The licensee's corrective actions included grounding the neutral leg of the isolation

transformer and fusing the output of the transformer to limit fault propagation. The licensee

also removed the ground from the control room ELUPS panel. These modifications did not

impact the isolation function of the transformer.

The event was of concern because a single electrical fault caused simultaneous fires in the

control room and the Train B dc equipment room which supports alternative post-fire safe

shutdown capability in the event of a control room fire. This electrical design error is

important because it created a fire vulnerability in two separate areas of the plant. The fire

could have resulted in operational challenges which are outside of the plant's design basis

IN 97-01 January 8, 1997 and the scope of the NRC fire protection regulations (10 CFR 50.48). This vulnerability was

caused by the inadequate design of the grounding circuitry from the electrical power supplies, which have been in service since the original construction.

This information notice requires no specific action or written response. 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 project manager.

f Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Chris Vandenburgh, Region IV

(817) 860-8161 E-mail: cavenrc.gov

Phil Qualls, Walnut Creek Field Office

(510) 975-0245 E-mail: pmqenrc.gov

Ronaldo Jenkins, NRR

(301) 415-2985 E-mail: rvjenrc.gov

Attachments:

1. Figure 1

2. List of Recently Issued NRC Inforation Nices

AIW J 7 tsn

---

Control Building Elevation 140' F 2E-QBN-D84 I Essential Ughting I

I Distribution Panel I Control Room

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I 2E-QDN-N02 Control Room Emergency

I Routed hIcaot and tay (FO1) Lighting Uninterruptable,

2E-QBB-V02 Power Supply (

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Control Building Elevation 100'

Figure 1 t0

Attachment 2 IN 97-01 January 8, 1997 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

96-72 Undetected Failure that 12/24/96 All teletherapy

May Occur During Patient licensees

Treatments with Teletherapy

Devices

96-71 Licensee Response to Indi- 12/27/96 All holders of OLs

cations of Tampering, Van- or CPs for nuclear

dalism, or Malicious Mis- power reactors

chief

96-70 Year 2000 Effect on Computer 12/24/96 All U.S. Nuclear

System Software Regulatory Commission

licensees, certificate

holders, and registrants

96-69 Operator Actions Affecting 12/20/96 All holders of OLs

Reactivity or CPs for nuclear

power reactors

96-68 Incorrect Effective Diaphragm 12/19/96 All holders of OLs

Area Values in Vendor Manual or CPs for nuclear

Result in Potential Failure power reactors

of Pneumatic Diaphragm

Actuators

96-67 Vulnerability of Emergency 12/19/96 All holders of OLs

Diesel Generators to Fuel or CPs for nuclear

Oil/Lubricating Oil Incom- power reactors

patibility

OL = Operating License

CP = Construction Permit

IN 97-01 January 8, 1997 and the scope of the NRC fire protection regulations (10 CFR 50.48). This vulnerability was

caused by the inadequate design of the grounding circuitry from the electrical power supplies, which have been in service since the original construction.

This information notice requires no specific action or written response. 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 project manager.

original signed by D.B. Matthews

fA homas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Attachments:

1. Figure 1

2. List of Recently Issued NRC Information Notices

Technical contacts: Chris Vandenburgh, Region IV

(817) 860-8161 E-mail: cav~nrc.gov

Phil Qualls, Walnut Creek Field Office

(510) 975-0245 E-mail: pmqenrc.gov

Ronaldo Jenkins, NRR

(301) 415-2985 E-mail: rvj@nrc.gov

DOCUMENT NAME: 97-01lN

Tech Editor reviewed 10/11/96 To receive a copy of this document, hIdicate In the box: ACE = Copy w/o

attachment/enclosure 'E - Copy wlattachmentlenclosure 'N' - No copy

OFFICE TECH CONTS IC/PECB:DRPM lIID/DRPMA II,

NAME PQualls* AChaffee* TMarti'

CVandenburgh*

____ ___ R ienki ns* _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _

DATE 12/09/96 12/26/96 01/';/97 M

OFFIC1AL RECORD COPY

v-vIN 96-xx

December xx, 1996 The event was of concern because a single electrical fault caused simultaneous fires in the

control room and the Train B dc equipment room which supports alternative post-fire safe

shutdown capability in the event of a control room fire. This electrical design error is

important because it created a fire vulnerability in two separate areas of the plant. e fire

could have resulted in operational challenges which are outside of the plant's d gn basis

and the scope of the NRC fire protection regulations (10 CFR 50.48). This nerability was

caused by the inadequate design of the grounding circuitry from the ele I power supplies, which have been in service since the original construction.

This information notice requires no specific action or written res nse. If you have any

questions about the information in this notice, please conta ne of the technical contacts

listed below or the appropriate Office of Nuclear Reactor gulation project manager.

Tho s T. Martin, Director

Di i on of Reactor Program Management

ice of Nuclear Reactor Regulation

Technical contacts: Chris Vandenbu, Region IV

(817) 860-81 Email: cay nrc.gov

Phil ua s, Walnut Creek Field Office

(5 ) 975-0245 ail: pmq@nrc.gov

Ronaldo Jenkins, NRR

(301) 415-2985 EMail: rvjinrc.gov

Attachme s:

1. Figur 1

2. Lis cf Recently Issued NRC Information Notices

DOCUMENT NAME: G:URTRPALOIN.DFT

Tech Editor reviewed 10/11 To receive a copy of this document, indicate in the box: "C" = Copy without

attachment/enclosure "E" = Copy with attachment/enclosure "N" = No copy

OFFICE

CONTACT

S IC/EELB:DE C/SRXB:DSSAL C/PECB:DRPM D/DRPM

NAME PQualls* JCalvo* LMarsh* AChaftee TMartin

CVandenburgh*

RJenkins*

DATE 12 /09/96 12/09/96 12/12/96 12P__96 121 /96 OFFICIALtta REODCP', A90===11

-IN 96-xx

December xx, 1996 The event was of concern because a single electrical fault caused simultaneous

fires in the control room and the Train B dc equipment room which supports

alternative post-fire safe shutdown capability in the event of a control room

fire. This electrical design error is important because it created a fire

vulnerability in two separate areas of the plant. The fire ould have

resulted in operational challenges which are outside of t plant's design

basis and the scope of the NRC fire protection regulations (10 CFR 50.48).

This vulnerability was caused by the inadequate desigf of the grounding

circuitry from the electrical power supplies, whic ave been in service since

the original construction.

This information notice requires no specific ction or written response. If

you have any questions about the informatio in this notice, please contact

one of the technical contacts listed bel or the appropriate Office of

Nuclear Reactor Regulation project manaer.

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical Contacts: Chris ndenburgh. Region IV

(817) 60-8161 EMai : cav@nrc.gov

P il Qualls, Walnut Creek Field Office

510) 975-0245 EMail: pmq@nrc.gov

Ronaldo Jenkins, NRR

(301) 415-2985 EMail: rvj@nrc.gov

Attachment: 1. Figure 1

2. List of Recently Issued NRC Information Notices

DOCUM T NAME: G:\JRT\PALOIN.DFT

Tech Editor reviewed 10/11

[

To receive a copy of this document, indicate in the box: "C"= Copy without

attachment/enclosure

NAME PQualls*

CVandenburgh*

RJenkins*

"E"= Copy with attachment/enclosure "N" = No copy

OFFICE

CONTACT

S L C/EELB:DE [_ C/SRXB:DSSA L C/PECB:DRPM _D/DRPM

_

JCalvo* LMarsh* AChaffee TMartin

DATE 12 /09/96 12/09/96 12/12/96 12/ /96 ., 12/ /96 OFFICIAL RECORD COPY

4 IN 96-xx

December xx, 1996 vulnerability in two separate areas of the plant. The fire cowd have

resulted in operational challenges which are outside of thei ant's design

basis and the scope of the NRC fire protection regulation (10 CFR 50.48).

This vulnerability was caused by the inadequate design the grounding

circuitry from the electrical power supplies, which e been in service since

the original construction.

This information notice requires no specific ac *on or written response. If

you have any questions about the information i this notice, please contact

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation project manager.

omas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical Contacts: Chris Vanonburgh, Region IV

(817) 8O -8161 EMail: cav@nrc.gov

Phi Qualls, Walnut Creek Field Office

CI0) 975-0245 ail: pmq@nrc.gov

Ronaldo Jenkins, NRR

(301) 415-2985 EMail: rvj@nrc.gov

Attachments: 1. Figure 1

2. List of Recently Issued NRC Information Notices

DOCUME NAME: G:\JRT\PALOIN.DFT

Tech ditor reviewed 10/11 To receive a copy of this document, indicate in the box: "C"= Copy without

attachment/enclosure "E"= Copy with attachment/enclosure "N"= No copy

OFFICE

CONTACT

S C/EELB: C/SRXB IC/PECB D/DRPM

Pr. DE L DSSA L_ :DRPM

NAME PQualls ul. JCalvo LMarshA AChaffee TMartin

CVandenb IM{

DATE R denkin_ _ _ _ _ _ _ _ _ _ _ _ _ _

DATE 12 /-/96 12/q/96 12/aE/96 12/ /96 12/ /96

,OFFICALRECORD COPY

0,119

4 t ' e

IN 96-xx

December xx, 1996 ,

potential to challenge the licensee's "Fire Protection Progr ' of 10 CFR

Part 50, Appendix R. This vulnerability was caused by th ?nadequate design

of the grounding circuitry from the electrical power supies, which have been

in service since the original construction.

This information notice requires no specific actiofi or written response. 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 project manager. J

Thomas T. Martin, Director

,Division of Reactor Program Management

//Office of Nuclear Reactor Regulation

Technical Contacts: Chris Vandenburgh, Region IV

(817) 860,:8161 EMail: /av@nrc.gov

Phil/Qualls, Walnut Creek Field Office

(5i) 975-0245 EMail: pmq@nrc.gov

Ronaldo Jenkins, NRR

(301) 415-2985 EMail: rvj@nrc.gov

Attachments: 1. Figure 1

2. List of Recently Issued NRC Information Notices

DOCUM T NAME: G:\JRT\PALOIN.DFT

Tec Editor reviewed 10/11 Tg receive a copy of this document, indicate in the box: "C"= (Copy without

attachment/enclosure "E"= Copy with attachment/enclosure "N'

" = No copy

OFFICE

CONTACT

S l I B:/EELB:

[C/SRXI C/PECB D/DRPM

_- ] DSSA DE :DRPM J

NAME PQualls 7 LMarsh JCalvo AChaffee TMartin

CVandenb 0ig

7 RJenkin t 110l

DATE 12 iJI98J9W 12/ /96 12/ /96 12/ /96 12/ /96 OFFIC RECORD COPY