Information Notice 1991-29, Deficiencies Identifie During Electrical Distribution System Functional Inspections

Deficiencies Identifie During Electrical Distribution System Functional Inspections

ML031190636
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:	04/15/1991
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-91-029, NUDOCS 9104090124
Download: ML031190636 (10)

4 A

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 April 15, 1991 NRC INFORMATION NOTICE NO. 91-29: DEFICIENCIES IDENTIFIED DURING ELECTRICAL

DISTRIBUTION SYSTEM FUNCTIONAL INSPECTIONS

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

This information notice is intended to alert addressees to deficiencies identi- fied during recently performed electrical distribution system functional

inspections (EDSFIs). It is expected that recipients will review the informa- tion for applicability to their facilities and consider actions, as appropri- ate, to avoid similar problems. However, suggestions contained in this

information notice do not constitute NRC requirements; therefore, no specific

action or written response is required.

Description of Circumstances

During multidisciplinary inspections, the U.S. Nuclear Regulatory Commission

(NRC) has identified many deficiencies related to tWeelectrical distribution

system. To address these deficiencies, the NRC has developed an inspection to

specifically evaluate the electrical distribution system. During the last

year, the NRC completed eight EDSFIs, performing at least one in each of the

five NRC geographical regions. During these inspections, the staff found

several common deficiencies in the licensees' programs and in the electrical

distribution systems as designed and configured at each plant. These deficien- cies included inadequate ac voltages at the 480 Vac and 120 Vac distribution

levels, inadequate procedures to test circuit breakers, and inadequate determi- nations and evaluations of setpoints.

Discussion:

Inadequate Voltage

During inspections conducted at the San Onofre Nuclear Generating Station

(Inspection Reports 50-361/89-200 and 50-362/89-200), the Susquehanna Steam

Electric Station (Inspection Reports 50-387/90-200 and 50-388/90-200), and the

9104090124

'J

IN 91-29 April 15, 1991 Waterford Steam Electric Station (Inspection Report 50-382/90-23), the staff

found that, under certain conditions, the voltage available at the safety buses

would be inadequate to Operate safety-related loads and associated equipment.

These conditions could occur when the plan~t's electrical distribution systems

were being supplied from an offsite grid that had become degraded but that

continued to supply voltages that remained above the setpoints at which the

degraded grid relays would be activated.

At San Onofre, the numerous voltage drops throughout the system could cause the

voltage to 120 Vaciontactors to drop below the-voltage range for which these

contactors were certified as acceptable by their manufacturers. To resolve

this problem the licensee has performed testing that established a lower

acceptable voltage range for this equipment.

At Susquehanna, the degraded grid relay setpoint'was'set at 84 percent on the

4160 Yac buses. Th'i's setpoint could have allowed inadequate voltage to be

-delivered to numerous safety-related loads at both the 480 Vac and 120 Vac

levels. The licensee calculated that setpoints'of at least 93 percent would be

required to ensure adequate voTtage to all safety-related equipment. To

resolve this problem, the lice'isee has raised the setpoints of the degraded

grid relays and has initiated a modification to install 120 Vac regulating

transformers.

At the Waterford nuclear plant, the degraded grid relays were set at

87.5 percent'as sensed on the'4160 Vac buses. :Although this setting was found

to be marginally adequate-'for-equipment connected to the 4160 Vac buses, the

setting was too low to ensure that adequate v6ltage would'be maintained at the

480 Vac and 120 Vac levels. The licensee is 6e4aluating solutions to this

problem and has instituted a procedure- to manually'separate from the grid if

the voltage falls to unacceptable levels but remains above the relay setpoints.

The function of the degraded grid relays is to en'sure that adequate voltage is

available tooperate all Class lE loads at all distribution levels. In order

to ensure-that all required'Class E 'loads will remain operable during degraded

voltage conditions, some licensees are currently'reanalyzing the basis for the

degraded grid relay setpoints. The new analyses consider all required Class 1E

loads and include the assumption that the voltage on the buses being sensed by

these relays can remain at a level just above the relay setpoints.

Inadequate Circuit Breaker Testing Procedures

During recent EDSFIs ahd previously on other NRC inspections, the staff identi- fied repetitive deficiencies in licensees' programs to test circuit breakers.

These deficiencies included inadequate procedures, inadequate test acceptance

criteria, inadequate test equipment, and inadequate control of testing. At the

Susquehanna plant (Inspection Reports 50-387/90-200 and 50-388/90-200), the

staff found that the licensee was testing dc molded case circuit breakers with

a procedure written for testing ac breakers. The licensee had not established

specific acceptance criteria for the dc breakers.

IN 91-29 April 15, 1991 At the Shearon Harris Nuclear Power Plant (Inspection Report 50-400/90-200),

the staff identified that the licensee was.testing molded case circuit breakers

against National Electrical Manufacturers Association (NEMA),acceptance crite- ria, which were less stringent than the manufacturer's time-current curves for

these breakers. In addition, the staff identified that the licensee was

testing 480 V air circuit breakers with test equipment that applied a test

signal (secondary injection) to the solid state trip units in the circuit

breakers. Although this method adequately verified that the trip units func- tioned properly, it did not verify that the breaker's current transformer

functioned properly or that the wiring and connectors were adequate between the

current transformer and the solid state trip units. Other licensees have

performed testing by primary current injection or by individually checking each

component of the circuit breaker, including the wiring and connectors to

demonstrate that the circuit breaker functions properly.

Inadequate Determinations and Evaluations of Setpoints

Many of the findings identified during recent EDSFIs were related to inadequate

setpoint determinations. Useful guidance for determining setpoints is provided

by Instrument Society of America Standard 67.04-1982, "Setpoints for Nuclear

Safety-Related Instrumentation used in Nuclear Power Plants," which the NRC

staff has endorsed by Regulatory Guide 1.105 Revision 2 - 1986, "Instrument

Setpoints for Safety-Related Systems." This guidance applies both to process

instrumentation and, in part, to certain relays that perform a safety function.

Some licensees have operated equipment outside of acceptable limits because

they did not determine proper setpoints and did not evaluate and account for

instrument drift. Operating the equipment under these conditions could

compromise the safety functions of the equipment. The staff has identified

these circumstances primarily for those instruments in which the licensee has

determined the setpoints as opposed to those instruments for which the

setpoints were determined by the architect/engineer or the nuclear safety

system supplier. Those setpoints not contained in the plant technical specifi- cations were also more frequently found to be deficient. During recent EDSFIs, the staff identified deficiencies in setpoints for diesel day tank level

indicators, diesel air start compressor controllers and alarms, inverter low

voltage shutdown circuitry, degraded grid relays, and diesel overcurrent

relays.

In addition to identifying deficiencies in the setpoints themselves, the NRC

has determined that not all the licensees are typically verifying that the

magnitude of instrument drift that was assumed in the original setpoint calcu- lation coincides with the magnitude of drift observed in the plant. Some

licensees have corrected this deficiency by verifying the magnitude of instru- ment drift by trending, (comparing "as found" calibration data to previous "as

left" data). This is particularly important for the degraded grid relay

setpoints, which often require very tight calibration tolerance bands, and for

which very low drift values are often assumed.

v- IN 91-29 April 15, 1991 This information notice requires no specific action or written response. If

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

technical contact listed below or the appropriate NRR project manager.

Charles E. Rossi, eirector

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Jeffrey B. Jacobson, NRR

(301) 492-0996 Attachment: List of Recently Issued NRC Information Notices

i

Attachment 1 IN 91-29 April 15, 1991 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

91-28 Cracking in Feedwater 04/15/91 All holders of OLs or

System Piping CPs for pressurized

water reactors (PWRs).

91-27 Incorrect Rotation of 04/10/91 All holders of OLs or

Positive Displacement Pump CPs for nuclear power

reactors.

89-90, Pressurizer Safety Valve 04/10/91 All holders of OLs or

Supp. 1 Lift Setpoint Shift CPs for nuclear power

reactors.

91-26 Potential Nonconservative 04/02/91 All fuel cycle licensees

Errors in the Working Format and other licensees, in- Hansen-Roach Cross-Section cluding all holders of

Set Provided with The Keno operating licenses for

and Scale Codes nuclear power reactors, who use physics codes to

support criticality

safety in the use of

fissile material.

91-25 Commercial-Grade Structural 04/01/91 All holders of OLs or

Framing Components Supplied CPs for nuclear power

As Nuclear Safety-Related reactors.

Equipment

91-24 Recent Operating Experience 03/26/91 All holders of OLs or

Involving Reactor Operation CPs for nuclear power, Without A Licensed Reactor test, and research re- Operator or Senior Reactor actors, and all Part 55 Operator Present in the licensed operators.

Control Room

91-23 Accidental Radiation Over- 03/26/91 All Nuclear Regulatory

exposures to Personnel Due to Commission (NRC) licens- Industrial Radiography Acces- ees authorized to use

sory Equipment Malfunctions sealed sources for indus- trial radiography.

OL = Operating License

CP = Construction Permit

IN 91-29 April 15, 1991 This information notice requires no specific action or written response. If

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

technical contact listed below or the appropriate NRR project manager.

O6ginal agen& by

Charles E. Ross!

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Jeffrey B. Jacobson, NRR

(301) 492-0996 Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES

• C/OGCB:DOEA:NRR*RPB:ADM *C/SICB:DST:NRR *C/SELB:DST:NRR

CHBerlinger TechEd SNewberry FRosa

04/ fI9 04/08/91 03/20/91 03/18/91 03/18/91 OGC :DOEA: RR *RSIB:DRIS:NRR *SC/RSIB:DRIS:NRR*C/RSIB:DRIS:NRR *D/DRIS:NRR

PCWen JBJacobson:bt EVImbro WDLanning BKGrimes

04/ /91 02/08/91 02/08/91 02/19/91 02/27/91

• - I IN 91-XX

April xx, 1991 If

no specific action or written response.

This information notice requires information in this notice, please contact the

you have any questions about the the appropriate NRR project manager.

technical contact listed below or

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Jeffrey B. Jacobson, NRR

(301) 492-0996 Notices

Attachment: List of Recently Issued NRC Information

• SEE PREVIOUS CONCURRENCES *C/SICB:DST:NRR *C/SELB:DST:NRR

T*RPB:Ad SNewBerry FRosa

D/DOEA:NRR C/OGCB:DO

CERossi Y- CHBerling rjw TechEd 03/18/91

03/20/91 03/18/91

04/ /91 04/8/91 *D/DRIS:NRR

,cCB:DOEA:NRR *RSIB:DRIS:NRR *SC/RSIB:DRIS:NRR*C/RSIB:DRISNRR

WMLanning BKGrimes

JBJacobson:bt EVImbro 02/27/91

4CvPvWen 02/08/91 02/19/91

04/cl/91 02/08/91

IN 91-XX

March xx, 1991 Inadequate Determinations and Evaluations of Setpoints

Many of the findings identified during recent EDSFIs related to inadequate

setpoint determinations. Useful guidance for determining setpoints is provided

by Instrument Society of America Standard 67.04-1982, "Setpoints for Nuclear

Safety-Related Instrumentation used in Nuclear Power Plants," which the NRC

staff has endorsed by Regulatory Guide 1.105 Revision 2 - 1986, "Instrument

Setpoints for Safety-Related Systems." This guidance applies both to process

instrumentation and, in part, to certain relays that perform a safety function.

did

Licensees have operated equipment outside of acceptable limits because they

not determine proper setpoints and did not evaluate and account for instrument

drifts. Operating the equipment under these conditions could compromise the

safety functions of the equipment. The staff has identified these circum- stances primarily for those instruments in which the licensee has determined

the setpoints as opposed to those instruments for which the setpoints were

determined by the architect/engineer or the nuclear safety system supplier.

Those setpoints not contained in the plant technical specifications were also

more frequently found to be deficient. During recent EDSFIs, the staff

identified deficiencies in setpoints for diesel day tank level indicators, diesel air start compressor controllers and alarms, inverter low voltage

shutdown circuitry, degraded grid relays, and diesel overcurrent relays.

NRC

In addition to identifying deficiencies in the setpoints themselves, the

has determined that licensees are not typically verifying that the magnitude

of instrument drift that was assumed in the original setpoint calculation

coincides with the magnitude of drift observed in the plant. Licenseefound" can

verify the magnitude of instrument drift by trending, (comparing 'as

calibration data to previous 'as left" data). This is particularly important

for the degraded grid relay setpoints, which often require very tight calibra- tion tolerance bands, and for which very low drift values are often assumed.

If

This information notice requires no specific action or written response. contact the

you have any questions about the information in this notice, please

technical contact listed below or the appropriate NRR project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Jeffrey B. Jacobson, NRR

(301) 492-0996 Attachment: List of Recently Issued NRC Information Notices

RPB:ADM C:OGCB:UOEA D:DOEA *See previous concurrence

TechEd* i m Ja CHBerlinger CERossi

03/20/91 P 1 03/l/91 03/ /91 SC:RSIB:DRIS C:RSIB:DRIS D:DRIS C:SELB:DST C:SICB:DST

RSIB:DRIS

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02/08/91 02/08/91 02/19/91 02/27/91 03/18/91 03/18/91

- IN 91-XX

January xx, 1991 Inadequate Setpoint Determinations and Evaluations

to inadequate

Many of the findings identified during recent EDSFIs were related appropriate

setpoint determinations. In order to properly determine an

be

instrument setpoint, all associated inaccuracies and tolerances must by ISA

accounted for. Useful guidance for determining setpoints is provided

in

67.04-1982, "Setpoints for Nuclear Safety-Related Instrumentation used 1.105 Nuclear Power Plants' which has been endorsed by Regulatory Guide

This

Revision 2 - 1986, "Instrument Setpoints for Safety Related Systems". for

guidance is applicable not Just for instrumentation but is also applicable

certain relays and other control oriented pieces of equipment.

in

The setpoint problem has been identified primarily with those instruments setpoints

which the licensee has determined the setpoints as opposed to those

the plant

determined by the NSSS vendor. Those setpoints not contained in EDSFIs, technical specifications are also likely to be suspect. During recent

level indicators, diesel

deficiencies in setpoints related to diesel day tank

low voltage shutdown

air start compressor controllers and alarms, invertor been

circuitry, degraded grid relays, and diesel overcurrent relays have

identified.

the NRC

In addition to the deficiencies identified in the setpoints themselves, magnitude of

has determined that licensees are not typically verifying that the

calculation is indeed

setpoint drift that was assumed in the original setpoint by comparing

correct. This verification can be performed by trending, i.e., particularly

"as found" calibration data to previous "as left" data. This is

important for the degraded grid setpoints where very tight calibration are often

tolerance bands are often required and where very low drift values has led to the

assumed. Failure to evaluate and account for instrument drifts

which could compromise the

operation of equipment outside of acceptable limits

safety functions of the equipment.

response. If

This information notice requires no specific action or writtenplease contact the

you have any questions about the information in this notice, technical contact listed below or the appropriate NRR project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Jeffrey B. Jacobson, NRR

(301) 492-0996 Attachment: List of Recently Issued NRC Information Notices

• See previous concurrence

RPB:ADM C:OGCB:DOEA D:DOEA

TechEd CHBerlinger CERossi

02/ /91 02/ /91 02/ /91 Xrt"

RSIB:DRIS SC:RSIB:DRIS C: S C:S C:SI

WD ng mes FRoV-rW SNe rry

JBJacobson*:bt EVImbro*

02/08/91 02/08/91 024 7/91 02/t7/91 "- / 91O/91

IN 91-XX

January xx, 1991 Inadequate Setpoint Determinations and Evaluations

Many of the findings identified during recent EDSFIs were related to inadequate

setpoint determinations. Inorder to properly determine an appropriate

instrument setpoint, all associated inaccuracies and tolerances must be

accounted for. Guidance for setpoint determinations is given inANSI Standard

S67.04-1988, 'Setpoints for Nuclear Safety-Related Instrumentation." This for

guidance isapplicable not Just for instrumentation but isalso applicable

certain relays and other control oriented pieces of equipment.

The setpoint problem ismost prevalent for those instruments inwhichdetermined the

licensee has determined the setpoints as opposed to those setpoints

by the NSSS vendor. Those setpoints not contained in the plant technical

specifications are also likely to be suspect. During recent EDSFIs,diesel defi- ciencies in setpoints related to diesel day tank level indicators, air

start compressor controllers and alarms, invertor low voltage shutdown

circuitry, degraded grid relays, and diesel overcurrent relays have been

identified.

Inaddition to the deficiencies identified inthe setpoints themselves, the NRC of

has determined that licensees are not typically verifying that the magnitude is indeed

setpoint drift that was assumed in the original setpoint calculation

correct. This verification can be performed by trending, i.e., by comparing

"as found" calibration data to previous "as left" data. This isparticularly

important for the degraded grid rely setpoints where very tight calibration

tolerance bands are often required and where very low drift values are often

assumed. Failure to evaluate and account for instrument drifts has led to the

operation of equipment outside of acceptable limits which could compromise the

safety functions of the equipment.

This information notice requires no specific action or writtenplease response. If

you have any questions about the information in this notice, contact the

technical contact listed below or the appropriate NRR project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Jeffrey B.Jacobson, NRR

(301) 492-0996 Attachment: List of Recently Issued NRC Information Notices

RPB:ADM C:OGCB:DOEA D:DOEA

TechEd CHBerlinger CERossi

02/ /91 02/ /91 02/ /91 RSIB: SC:RX RIS C:RSIB:DRIS D:DRIS C:SELB:DST C:SICB:DST

JBJac 6n:bt EVIm 'J>' WDLanning BKGrimes FRosa SNewberry

020 A' 02/djz1 02/ /91 02/ /91 02/ /91 02/ /91