Information Notice 1991-51, Inadequate Fuse Control Programs
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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
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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
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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
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 of Emergency
Diesel Generator 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
. .
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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
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07/26/91
07/29/91
07/31/91 DOCUMENT NAME: IN 91-51
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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
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07/26/91
07/26/91
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08/06/91
08/05/91
- SELB:DST:NRR*C/SELB:DST:NRR
FHBurrows
FRosa
07/29/91
07/31/91
-
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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
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