Information Notice 1993-95, Storm-Related Loss of Offsite Power Events Due to Salt Buildup on Switchyard Insulators
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
December 13, 1993 NRC INFORMATION NOTICE 93-95: STORM-RELATED LOSS OF OFFSITE POWER EVENTS
DUE TO SALT BUILDUP ON SWITCHYARD INSULATORS
Addressees
All holders of operating licensees or construction permits for nuclear power
reactors located close to a large body of salt water.
PurDose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees to the potential for loss of offsite power due to
salt contamination of switchyard insulators. It is expected that recipients
will review the information for applicability to their facilities and consider
actions, as appropriate, to avoid similar problems. However, no specific
action or written response is required.
Description of Circumstances
On March 17, 1993, the Florida Power Corporation Crystal River Unit 3 experienced a loss of the 230 kV switchyard (normal offsite power to safety- related busses) when a light rain caused arcing across salt-laden 230 kV
insulators and opened breakers in the switchyard. At the time, the unit was
in cold shutdown during a maintenance outage. The 'Al emergency diesel
generator was used to power safety-related loads including shutdown cooling
until the 230 kV switchyard was restored.
The ABE emergency diesel generator
was unavailable due to maintenance. The 500 kV switchyard supplied nonvital
loads throughout the event.
On March 16 through 18, 1993, Carolina Power and Light Company's Brunswick
Units 1 and 2 experienced a loss of the 230 kV switchyards (all offsite power)
when light rain caused arcing across salt-laden insulators and opened breakers
in the switchyard. At the time, both units were in cold shutdown during an
extended outage. Emergency diesel generators were used to power safety- related loads including shutdown cooling until the offsite power was restored.
Since 1982, the Boston Edison Company Pilgrim station has also experienced
several loss of offsite power events when heavy ocean storms deposited salt on
the 345 kV switchyard causing the insulators to arc to ground.
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December 13, 1993 Discussion
Intense and unusual storms on March 13 and 14, 1993, produced high tides and
high winds (average of 80 to 97 kilometers/hour high winds (50 to 60
miles/hour], with gusts up to 160 kilometers/hour [100 miles/hour] blowing
ashore from the ocean i.e., Gulf of Mexico and Atlantic Ocean. These storms
caused an unusual buildup of salt on the switchyard insulators at
Crystal River Unit 3 and Brunswick Units 1 and 2. The storms were unusual in
that they included high winds but little or no precipitation. As a result, salt from ocean spray built up on the switchyard insulators and was not washed
away by rain.
Days later, light rain increased the electrical conductivity of the salt, resulting in arcing across the insulators at both sites. To remove the salt
from the insulators, Florida Power Corporation and Carolina Power and Light
Company deenergized the affected switchyards, washed the insulators with high
pressure demineralized water, then returned the switchyards to service. The
washing stopped the electrical arcing across the insulators.
The 500 kV switchyard for Crystal River Unit 3 is located adjacent to the
230 kV switchyard. It was relatively unaffected. The 500 kV switchyard is
used for main generator output when Unit 3 is operating and is used for an
alternate source of offsite power (i.e., backfeeding of nonvital loads) during
Unit 3 outages. The 500 kV switchyard experienced less arcing across the
insulators than the 230 kV switchyard and no tripped breakers. As a
precautionary measure, the licensee also deenergized and washed the 500 kV
switchyard insulators. Factors that may have reduced the storm inpact on the
500 kV switchyard included location (farther away from the shore) and higher
insulation level (the 500 kV insulators were designed for up to 700 kV
operation while the 230 kV insulators were designed for up to 242 kV
operation). In addition, the licensee observed that, of the two types of
230 kV insulators installed, the newer post type had less arcing than the
older cap and pin type.
Licensee followup action in response to these events, to improve the future
performance of non-safety switchyard equipment, included: investigating
available salt buildup monitoring systems, evaluating insulator washing
methods/capabilities, considering the use of room temperature vulcanized (RTV)
silicon rubber coatings, installing newer metal oxide gapless surge arrestors
to replace older silicon carbide gap type surge arrestors, and replacing
cellon-treated wood transmission towers.
The 345 kV switchyard insulators at Pilgrim were coated with RTV silicon
rubber (Sylgard) in 1987. It was expected that the RTV coating, when applied
in 1987, would be effective for a period of 15 years. However, actual
experience at Pilgrim indicates that the coating is effective for a much
`-
December 13, 1993
shorter period of time. Consequently, the Insulators at Pilgrim were cleaned
and coated with RTV again during the spring 1993 refueling outage. As a long- term option, the licensee is considering a replacement of the existing 345 kV
switchyard with a modern compactly designed switchyard which would be more
resistant to the coastal environment.
These events illustrate the significance of maintaining reliable offsite and
onsite power sources during outages as well as during operation.
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 Regulation (NRR) project manager.
Bran . Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts:
R. Schin, RII
(404) 331-5561
P. Fillion, RII
(404) 331-7288 P. Holmes-Ray, RII
(904) 795-7677
P. Kang, NRR
(301) 504-2779
R. Prevatte, RII
(919) 457-9531 Attachment:
List of Recently Issued NRC Information Notices
Attachment
December 13, 1993 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Informati on
Date of
Notice No.
Subject
Issuance
Issued to
93-94
93-93
93-92
91-21, Supp. 1
89-77, Supp. 1
93-91
Unauthorized Forced
Entry into the Pro- tected Area at Three
Mile Island Unit 1 on
February 7, 1993
Inadequate Control of
Conditions During Shutdown
Plant Improvements to
Mitigate Common Depend- encies in Component
Cooling Water Systems
Inadequate Quality
Assurance Program of
Vendor Supplying
Safety-Related Equipment
Debris in Containment
Emergency Sumps and
Incorrect Screen
Configurations
Misadjustment Between
General Electric 4.16-KV
Circuit Breakers and Their
Associated Cubicles
Unisolatable Reactor
Coolant System Leak
Following Repeated
Applications of Leak
Sealant
12/09/93
12/08/93
12/07/93
12/07/93
12/03/93
12/03/93
12/01/93
All holders of OLs or CPs
for nuclear power reactors.
All holders of OLs or CPs
for nuclear power reactors.
All holders of OLs or CPs
for nuclear power reactors.
All holders of OLs or CPs
for nuclear power reactors
and all recipients of
NUREG-0040, "License Con- tractor and Vendor Inspec- tion Status Report" (White
Book).
All holders of OLs or CPs
for nuclear power reactors.
All holders of OLs or CPs
for nuclear power reactors.
All holders of OLs or CPs
for nuclear power reactors.
93-90
OL - Operating License
CP - Construction Permit
IN 93-95 December 13, 1993 shorter period of time. Consequently, the Insulators at Pilgrim were cleaned
and coated with RTV again during the spring 1993 refueling outage. As a long- term option, the licensee is considering a replacement of the existing 345 kV
switchyard with a modern compactly designed switchyard which would be more
resistant to the coastal environment.
These events Illustrate the significance of
onsite power sources during outages as well
maintaining reliable offsite and
as during operation.
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 Regulation (NRR) project manager.
OgItf Ognefw
5
Brian K. Grimeg
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts:
R. Schin, RII
(404) 331-5561
P. Fillion, RII
(404) 331-7288 P. Holmes-Ray, RII
(904) 795-7677 P. Kang, NRR
(301) 504-2779
R. Prevatte, RII
(919) 457-9531 Attachment:
List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
OFFICE
- RII
- TECH ED
- EELB
- C:EELB:NRR
NAME
RSchin
JBeeson
PKang
CBerlinger
DATE
_07/13/93
08/09/93
11/03/93
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IN 93-XX
December xx, 1993
shorter period of time. Consequently, the insulators at Pilgrim were cleaned
and coated with protective RTV coating again during the spring 1993 refueling
outage. As an alternate long term option, the licensee is considering a
replacement of the existing 345 kV switchyard with a modern compactly designed
switchyard which would be more resistant to the coastal environment.
These events illustrate the significance of maintaining reliable offsite and
onsite power sources during outages as well as during operation.
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 Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts:
R. Schin, RII
(404) 331-5561
P. Fillion, R11
(404) 331-7288 P. Holmes-Ray,
(904) 795-7677 RII
P. Kang, NRR
(301) 504-2779
R. Prevatte, RII
(919) 457-9531 Attachment:
List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
OFFICE
- RII
- TECH ED
- EELB
- C:EELB:NRR
NAME
RSchin
JBeeson
PKang
CBerlinger
DATE
07/13/93
-08/09/93
,11/03/93
11/03/93 D: DE
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IN 93-XX
November xx, 1993
NRC review of these events concluded that the safety-related equipment at the
affected units performed as designed and there were no increased risks to the
public.
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 Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts:
R. Schin, RII
(404) 331-5561
P. Fillion, RII
(404) 331-7288 P. Holmes-Ray, RII
(904) 795-7677
P. Kang, NRR
(301) 504-2779
R. Prevatte, R11
(919) 457-9531 Attachment:
List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
OFFICE
- RII
- TECH ED
- EELB
- C:EELB:NRR
NAME
RSchin
JBeeson
PKang
CBerlinger
DATE
J07/13/93 o08/09/93 i11/03/930,
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DOCUMENT NAME: SWITCHIN.NEC
IN 93-XX
November xx, 1993
NRC review of these events concluded that the safety-related equipment at the
affected units performed as designed and there were no increased risks to the
public.
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 Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts:
R. Schin, RII
(404) 331-5561
P. Fillion, RII
(404) 331-7288
P. Kang, NRR
(301) 504-2779 P. Holmes-Ray, SRI, Crystal River
(904) 795-7677
R. Prevatte, SRI, Brunswick
(919) 457-9531 Attachment:
List of Recently Issued NRC Information Notices
- SEE PREVIOUS CANCUIRRFNCr
-
OFFICE
- RII
- TECH ED
- EELB
- C:EELB:NRR
NAME
RSchin
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November xx, 1993
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 Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts:
R. Schin, RII
(404) 331-5561
P. Fillion, RII
(404) 331-7288 P. Holmes-Ray, SRI, Crystal River
(904) 795-7677
R. Prevatte, SRI, Brunswick
(919) 457-9531 Attachment:
List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
OFFICE
- RII
- TECH ED
- EELB
- C:EELB:NRR
NAME
RSchin
JBeeson
PKang
CBerlinger
DATE
1 07/13/93
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August xx, 1993 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 Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts:
R. Schin, RII
(404) 331-5561
P. Fillion, RII
(404) 331-7288 P. Holmes-Ray, SRI, Crystal River
(904) 795-7677
R. Prevatte, SRI, Brunswick
(919) 457-9531 di
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IN 93-XX
August xx, 1993 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 Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts:
R. Schin, RII
(404) 331-5561
P. Fillion, RII
(404) 331-7288 P. Holmes-Ray, SRI, Crystal River
(904) 795-7677
R. Prevatte, SRI, Brunswick
(919) 457-9531 Attachment:
List of Recently Issued NRC Information Notices
- SFF PREVIOUS CONCURRENCE
OFFICE
RII
- TECH ED
EELB
C:EELB:NRR
NAME
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