Information Notice 1991-51, Inadequate Fuse Control Programs
_1 I 4 UNITED STATES NUCLEAR REGULATORY
COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555 August 20, 1991 NRC INFORMATION
NOTICE NO. 91-51: INADEQUATE
FUSE CONTROL PROGRAMS
Addressees
All holders of operating
licenses or construction
permits for nuclear power reactors.
Purpose
- _This information
notice is intended to alert addressees
to potential
problems caused by inadequate
programs to control activities
related to fuses. 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 do not constitute
NRC requirements;
therefore, no specific action or written response is required.Description
of Circumstances:
-During recent inspections, the U.S. Nuclear Regulatory
Commission (NRC) has identified
numerous deficiencies
involving
fuse control programs.
These deficiencies
included inadequate
root cause evaluations
of blown fuses, inadequate
verification
of design information
for installed
and replacement
fuses, inadequate
identification
and labeling of fuses, and lack of coordina-tion between fuses and circuit breakers.Other fuse control problems, especially
those resulting
from personnel
errors, have been reported in licensee event reports (LERs). As reported in the LERs, these personnel
errors have caused inadvertent
operation
or loss of vital plant equipment
and, in some cases, have resulted in a loss of offsite AC power and the spurious actuation
of engineered
safety features (ESF).Discussion:
The main function of a fuse is to prevent or minimize damage to the electrical
distribution
system (EDS) and related components
and to limit the effect and extent of service interruptions
whenever any portion of the system is subjected to a fault. Fuses are relied upon to isolate electrical
faults to ensure minimum disturbance
to the system. Fuses are also uses as electrical
isolation devices between a class 1E power supply and non-class
1E electrical
equipment.
Proper protection
is achieved through the careful selection
of the type and the rating of the fuse. If an oversized
fuse is selected that has a higher capa-city than the upstream fuse or breaker, the oversized
fuse could make the entire S4 2T~ , 7:V /16'
IN 91-51 August 20, 1991 -bus unavailable
in case of a fault within the circuit. In addition, a faulted circuit with an oversized
fuse can degrade the voltage of a bus and impart excessive
heat to adjacent cables. On the other hand, .if an undersized
fuse is selected, the undersized
fuse could lead to a loss of the safety.function
of equipment
by prematurely
opening the protected
circuit. Therefore, when selecting
fuses, it is important
to consider the voltage, current, interrupting
rating, fuse type, and coordination
with other fuses and circuit breakers.Common deficiencies
identified
during recent NRC inspections
of fuse control programs are as follows: Inadequate
Root Cause Evaluation
of Blown Fuses During an NRC inspection
at Zion Nuclear Power Station, Unit 2 (NRC Inspec-tion Report 50-295/90-13)i
the staff noted that on July 7, 1990, Unit 2 personnel
declared an alert condition
because of a partial loss of the annunciators
in the control room for the nuclear steam supply system (NSSS)and the balance-of-plant (BOP) systems. The loss of the annunciators
apparently
resulted from blown fuses in the power supplies for the annun-ciators. On 11 different
occasions
between July 1 and July 7, 1990, fuses blew in various NSSS and BOP annunciator
power supplies.
The licensee's
electrical
maintenance
personnel
and operators
continued
to replace-the
blown fuses without contacting
the technical
staff engineers
to determine the root causes of the excessive
fuse failures until after the event on July 7, 1990. Subsequently, the licensee determined
that some of the fuses installed
in 125 VDC power supplies were rated for 32 VOC.Inadequate
Verification
of Design Information
for Installed
and Replacement
Fuses In June 1990, during an NRC maintenance
team inspection
at Kewaunee Nuclear Power Plant (NRC Inspection
Report 50-305/90-11), the NRC identi-fied a number of discrepancies
between design documents
and fuses in-stalled in AC and DC safety-related
fuse panels. In addition, the NRC found that many design documents
did not contain information
regarding
the size, rating, type, or manufacturer
of the fuse. The discrepant
fuses and the lack of design information
could have caused inadequate
system and component
protection.
Inadequate
Identification
and Labeling of Fuses In July and August 1990, during an electrical
distribution
system func-tional inspection (EDSFI) at the Trojan Nuclear Plant (NRC Inspection
Report 50-344/90-200), the NRC determined
that tbL licensee did not have an adequate program to control the identification, labeling, and replace-ment of fuses. The NRC also determined
that the lack of a fuse control program had contributed
to past problems with incorrectly
installed
fuses.
K 9<_ IN 91-51 August 20, 1991 Improper Coordination
of Fuses and Circuit Breakers In May 1990, during a routine inspection
at the Palisades
Nuclear Generat-ing Plant (NRC Inspection
Report 50-255/90-10), three examples were found in which fuses and breakers did not coordinate
in all regions on the coordination
curves. This, in turn, might have resulted in a disturbance
to the system under fault conditions
not being minimized.
In addition, the NRC found that the licensee's
fuse procedure
specified
voltage and current ratings for fuse replacements
but did not include the model and type. Without all of the proper information, such as the time/current
characteristics
of the fuse, proper coordination
and protection.
may not have been obtained.Personnel
Errors Although personnel
errors cannot be totally eliminated
from routine, emergency, or corrective
plant maintenance, a review of LERs indicates that most errors are caused by either the plant staff not being adequately
trained or plant procedures
not being adequately
detailed.
Some examples of these LERs are included in Attachment
1. A well designed fuse control program along with trained personnel
and clear procedures
could reduce errors in fuse control significantly.
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
NRR project manager.Charles E. Rossi, Director Division of Operational
Events Assessment
Office of Nuclear Reactor Regulation
Technical
Contacts:
Zelig Falevits, RIII (708) 790-5772 Roger Mendez, RIII (708) 790-5589 Fred Burrows, NRR (301) 492-3260 Attachments:
-<1. Examples of LERs Related to Fuse Problems Caused by Personnel
Errors 2. List of Recently Issued NRC Information
Notices
Q Attachment
1 IN 91-51 August 20, 1991 Examples of LERs Related to Fuse ProblemsCaused
by Personnel
Errors Facility:
Dresden Unit 2 LER No.: Abstract: Facility: LER No.: Abstract: Facility: LER No.: Abstract: Facility: 50-237/88-023 On December 31, 1988, with the unit in the refueling
mode, an ESF actuation
occurred and subsequently
caused initiation
of the standby gas treatment
system and isolation
of the reactor building ventila-tion system. The ESF actuation
occurred-when
the wrong fuses were pulled after an operating
shift foreman erroneously
changed the fuse numbers on the equipment
outage checklist.
The operating
shift fore-man believed that the fuse numbers originally
listed on the equipment outage checklist
were incorrect.
He changed the fuse numbers but failed to have a second operator independently
verify the change. As a result of this error, the wrong fuses were pulled and an unexpected
ESF actuation
occurred.Peach Bottom Unit 2 50-277/88-006 On March 3, 1988, the unit experienced
an actuation
of the primary containment
isolation
system as the result of a loss of power to then"A" residual heat removal system logic bus. The loss of power was caused by an improperly
filled out blocking permit which directed the individual
performing
the block to remove a fuse from a wrong panel.Zion Unit 1 50-295/87-009 On April 30, 1987, with the unit in hot shutdown, the unit experi-enced a safety injection
and opening of the main steam isolation valves which pressurized
the steam line to approximately
800 psig (from approximately
80 psig). The event occurred because an elec-trical equipment
operator failed to pull fuses in the required sequence.Fort Calhoun Unit 1 LER No.: Abstract: 50-285/87-009 -WCA On April 4, 1987, the unit experienced
an unplanned
loss of all offsite AC power because of personnel
error. The loss of offsite AC power occurred when electrical
maintenance
personnel
were performing
maintenance
on a transformer's
secondary
side non-segregated
bus duct. They inadvertently
pulled the wrong transformer
fuses, resulting
in the tripping of an on-line transformer, the opening of the secondary
side breakers and, ultimately, the temporary
loss of all offsite AC power to the plant.
e Attachment
2 IN 91-51 August 20, 1991 LIST OF RECENTLY ISSUED NRC INFORMATION
NOTICES Information
Date of Notice No. Subject Issuance Issued to 91-50 91-49 91-48 91-47 89-56, Supp. 2 91-46 91-45 A Review of Water Hammer Events After 1985 Enforcement
of Safety Requirements
for Radiog-raphers False Certificates
of Con-formance Provided by West-inghouse Electric Supply Company for Refurbished
Com-mercial-Grade
Circuit Breakers Failure of Thermo-Lag
Fire Barrier Material to Pass Fire-Endurance
Test Questionable
Certification
of Material Supplied to the Defense Department
by Nuclear Suppliers Degradation
Fuel Oil Delivery Systems Possible Malfunction
of Westinghouse
ARD, BFD, and NBFD Relays, and A200 DC and DPC 250 Magnetic Con-tactors 08/20/91 All holders of OLs or CPs for nuclear power reactors.08/15/91 All Nuclear Regulatory
Com-mission (NRC) licensees authorized
to use sealed sources for industrial
radiography.
08/09/91 All holders of OLs or CPs for nuclear power reactors.08/06/91 All holders of OLs or CPs for nuclear power reactors.07/19/91 All holders of OLs or CPs.for nuclear power reactors.07/18/91 All holders of OLs or CPs for nuclear power reactors.07/05/91 All holders of OLs or CPs for nuclear power reactors.91-44 Improper Control of Chemicals
in Nuclear Fuel Fabrication
07/08/91-441 nuclear fuel facilities.
OL = Operating
License CP = Construction
Permit..
IN 91-51-August 20, 1991 Improper Coordination
of Fuses and Circuit Breakers In May 1990, during a routine inspection
at the Palisades
Nuclear Generat-ing Plant (NRC Inspection
Report 50-255/90-10), three examples were found in which fuses and breakers did not coordinate
in all regions on the coordination
curves. This, in turn, might have resulted in a disturbance
to the system under fault conditions
not being minimized.
In addition, the NRC found that the licensee's
fuse procedure
specified
voltage and current ratings for fuse replacements
but did not include the model and type. Without all of the proper information, such as the time/current
characteristics
of the fuse, proper coordination
and protection
may not have been obtained.Personnel
Errors Although personnel
errors cannot be totally eliminated
from routine, emergency, or corrective
plant maintenance, a review of LERs indicates that most errors are caused by either the plant staff not being adequately
trained or plant procedures
not being adequately
detailed.
Some examples of these LERs are included in Attachment
1. A well designed fuse control program along with trained personnel
and clear procedures
could reduce errors in fuse control significantly.
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
NRR project manager.Charles E. Rossi, Director Division of Operational
Events Assessment
Office of Nuclear Reactor Regulation
Technical
Contacts:
Zelig Falevits, RIII (708) 790-5772 Roger Mendez, RIII (708) 790-5589 Fred Burrows, NRR (301) 492-3260 Attachments:
1. Examples of LERs Related to Fuse Problems Caused by Personnel
Errors 2. List of Recently Issued NRC Information
Notices*SEE P VIOUS CONCURRENCES
_NEEI "<t/OGCB:DOEA:NRR
- RPB:ADM *D/DRIS:NRR
- D/DST:NRR
CHBerlinger
TechEd BKGrimes AThadani 08/1 08/ /91 08/07/91 08/06/91 08/05/91*OGCB:DOEA
RR *RIII *RIII *SELB:DST:NRR*C/SELB:DST:NRR
PCWen ZFalevits
RMendez FHBurrows
FRosa 07/26/91 07/26/91 07/26/91 07/29/91 07/31/91 DOCUMENT NAME: IN 91-51
(0 IN 91-XX August xx, 1991 Improper Coordination
of Fuses and Breakers In May 1990, during a routine inspection
at the Palisades
Nuclear Generat-ing Plant (NRC Inspection
Report 50-255/90-10), three examples were found in which fuses and breakers did not coordinate
in all regions on the coordination
curves. This, in turn, might not have minimized
the distur-bance to the system under fault conditions.
In addition, the NRC found that the licensee's
fuse procedure
specified
voltage and current ratings for fuse replacements
but did not include the model and type. Without all of the proper information, such as the time/current
characteristics
of the fuse, proper coordination
and protection
may not have been obtained.Personnel
Errors Although personnel
errors cannot be totally eliminated
from routine, emergency, or corrective
plant maintenance, a review of LERs indicates that most errors are caused by either the plant staff not being adequately
trained or plant procedures
not being adequately
detailed.
Some examples of these LERs are included in Attachment
1. A well designed fuse control program along with trained personnel
and clear procedures
could reduce errors in fuse control significantly.
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
NRR project manager.Charles E. Rossi, Director Division of Operational
Events Assessment
Office of Nuclear Reactor Regulation
Technical
Contacts: Zeli Falevits, RIII (708) 790-5772 Roger (708)Mendez, RIII 790-5589 Fred Burrows, NRR (301) 492-3260 Attachments:
1. Examples of LERs Related to Fuse Problems Caused by Personnel
Errors 2. List of Recently Issued NRC Information
Notices Document Name: IN FOR FUSE CONTROL INSPE*SEE PREVIOUS CONCURRENCES
D/DOEA:NRR
C/OGCB:DOEA:NRR
- RPB:ADM CERossiod
CHBerlinger!
TechEd 08/ /91 08/12491 ¶ 08/07/91*OGCB:DOEA:NRR
- RIII *RIII PCWen ZFalevits
RMendez 07/26/91 07/26/91 07/26/91*D/DRIS:NRR
- D/DST:NRR
BKGrimes AThadani 08/06/91 08/05/91*SELB:DST:NRR*C/SELB:DST:NRR
FHBurrows
FRosa 07/29/91 07/31/91
--vt @* 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
NRR project manager.?'i Charles E. Rossi, Director Division of Operational
Events Assessment
Office of Nuclear Reactor Regulation
Technical
Contacts: Zelig Falevits, RIII (708) 790-5772 Roger Mendez, RIII (708) 790-5589 Fred Burrows, NRR (301) 492-3260 Attachments:
1. Examples of LERs Related to Fuse Problems Caused by Personnel
Errors 2. List of Recently Issued NRC Information
Notices Document Name: IN FOR FUSE CONTROL INSPECTION
D/DOEA:NRR
CERossi 07/ /91 OGCB:DOEA:N
R PCWen 07/9b/C/OGCB:DOEA:NRR
RPB:ADM CHBerlinger
7flw TechEd 07/ /91 p07/ /9: RI I I ?J RIIIiCV Faldvits 4vpMendez 8 7/ab6/91 1 07/9/9 KR aCA~~s pER -,W. E, 0J I