United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 83-11: Possible Seismic Vulnerability of Old Lead Storage Batteries

                                                            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  
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                                                           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 
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                                                           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 

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