Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
SSINS NO.: 6835
IN 83-11
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
March 14, 1983
Information Notice No. 83-11: POSSIBLE SEISMIC VULNERABILITY OF OLD
LEAD STORAGE BATTERIES
Addresses:
All nuclear power plant facilities holding an operating license (OL) or
construction permit (CP).
Purpose:
This information nctice informs you that lead-acid storage batteries
approaching their end of operational life may be vulnerable to seismically
induced failure.
Description of Circumstances:
A series of events involving spontaneous battery failure or degradation over
the past few years, not related to seismic events, has caused concern in the
NRC staff regarding the potential vulnerability of old batteries to a
seismic event. In each of several events, spontaneoUs battery failure or
degradation has been attributed to swollen positive plates and/or cracked
cases. Even for those plants that have seismically qualified batteries, the
batteries are rarely qualified by prototype testing of aged cells.
Consequently, a pattern is developing of spontaneous failure of old
batteries that suggests a seismic event could cause a common-mode failure of
the plant DC systems.
One such example occurred at the Haddam Neck plant on September 19, 1982.
While in Mode 2 (startup) the emergency DC Battery Bank B, cell 42, was
discovered to be leaking eletrolyte through a seam crack. Further inspection
revealed eleven other cells with casing cracks, that did not extend through
the wall. If cell 42 were jumpered out, battery bank voltage would have been
125.3 V DC, only just above the technical specification limit of 125 V DC.
Consequently, the licensee decided to declare the Battery Bank B inoperable
and completely replace it.
The occurrence on September 19, 1982, was preceded by a similar instance on
June 18, 1982, when Battery Bank B, cell 23, was discovered leaking and was
jumpered out.
After removing Battery Bank B, some of the failed cells were sent to the
manufacturer for a determination of the failure mechanism.
The original "B" train battery that failed was composed of Gould FTA-15
cells each with a rated capacity of 840 ampere-hours. The "A" train battery
was
8212060378
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IN 83-11
March 14, 1983
Page 2 of 3
composed of Gould FTA-17 designed cells with a rated capacity of 960 ampere-
hours. Haddam Neck obtained Gould NCX-1500 cell from Calvert Cliffs as a
temporary replacement for "B" battery. Haddam Neck is purchasing Gould
NCX-1200 cells as a permanent replacement for the "B" battery.
The FTA design has not been manufactured by Gould for more than ten years.
The FTA cells used at Haddam Neck comprised the original battery and were
therefore about 15 years old at the time of their failure. (Operating
license date is June 30, 1967.)
Other examples of cells failing because of swollen positive plates or
cracked cases have been identified. An Licensee Event Report (LER) search
revealed six other instances of battery case cracking.
LER# Plant Date(s) Battery Manufacturer
81-5 Diablo Canyon (10/81) C & D, Div. of ELTRA
82-16, 82-7 Indian Point 2 (4/82) and (2/82) Not described
81-42 Browns Ferry (7/81) C & D, Div. of ELTRA
77-55 FitzPatrick (9/77) Gould
74-5 Turkey Point 4 (10/74) Not described
Although it is impossible to tell in every instance from the LER alone what
precisely caused each failure, 5 of these LER's bear some similarity to the
Haddam Neck battery failure. The battery failure at Diablo Canyon is
attributed to a design flaw of the battery case and is not similar to the
Haddam Neck failure.
Like the Gould FTA batteries at Haddam Neck, most batteries now used in
nuclear power plants are not qualified to withstand a seismic event at their
end-of-life condition. Even those batteries that are qualified in accordance
with Regulatory Guide 1.100 "Seismic Qualification of Electric Equipment for
Nuclear Power" are not necessarily brought to their end-of-life condition
prior tb seismic testing. Regulatory Guide 1.100 endorses IEEE Std. 344
"Recommended Practices for Seismic Qualification of Class IE Equipment for
Nuclear Power Generating Stations." At the end-of-life condition, the
battery plates are more vulnerable because they are brittle. Also material
can slough off the plates, shorting out the battery, or reducing its
capacity.
Discussion:
Surveillance tests required by technical specifications will detect a
degradation in a battery's ability to deliver it's rated charge but will not
detect those degradations of a battery's structure making it vulnerable to
even a mild seismic event.
The structure of a battery is weakened as it becomes old because the
positive plates crack ahd swell or because of a wide variety of other
failure mechanisms. Usually, degradation of the positive plate is the
limiting factor in the life
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IN 83-11
March 14, 1983
Page 3 of 3
of a properly maintained battery. As the positive plate becomes more cracked
and embrittled it becomes less able to resist seismic motion and to retain
its mechanical integrity. For this reason the NRC staff suspects that the
useful electrical life of a large lead storage battery may be longer than
its seismic-qualified life. The NRC staff does not yet know of any
definitive surveillance test for identifying incipient seismic vulnerability
of an old battery other than seismic testing of selected cells.
Batteries not maintained at proper float voltage, stored or used at high
temperatures, or subject to improper maintenance may undergo accelerated
aging processes reducing the life of the battery and increasing its seismic
vulnerability.
The Institute of Electrical and Electronics Engineers has published IEEE
Std. 535-1979, "IEEE Standard for Qualification of Class 1E Lead Storage
Batteries for Nuclear Power Generating Stations." This standard requires, as
part of a qualification process, bringing a prototype cell to its
end-of-life condition prior to seismic testing. Battery cells qualified in
accordance with IEEE Std. 535 will have a qualified life reflecting the
increased seismic vulnerability of old batteries.
Although no seismically induced battery failure has occurred to date, the
serious consequences of such a failure are worthy of concern. Several
postulated examples follow: A seismic event might accelerate cracking of the
case resulting in loss of electrolyte and complete loss of the battery. A
seismic event might cause accelerated cracking of embrittled plates or loss
of lead-dioxide coating of plates resulting in substantial drop in battery
capclcity almost instantly. A complete loss of the DC system would put the
plant in a unanalyzed condition.
The NRC staff is considering research that will define the seriousness of
agerelated seismic vulnerability of lead storage batteries. Further
regulatory guidance on the issues raised in this information notice may be
forthcoming.
No written response to this information notice is required. If you need
other information regarding this matter, please contact the Regional
Administrator of the appropriate NRC Regional Office.
Edward L Jordan, Director
Division of Emergency Preparedness
and Engineering Response
Office of Inspection and Enforcement
Technical Contact: Eric Weiss, IE
(301) 492-4973
Attachment:
List of Recently Issued IE Information Notices
