United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 89-17: Contamination and Degradation of Safety-Related Battery Cells

                                  UNITED STATES
                          NUCLEAR REGULATORY COMMISSION
                      OFFICE OF NUCLEAR REACTOR REGULATION
                             WASHINGTON, D.C.  20555

                                February 22, 1989


Information Notice No. 89-17:  CONTAMINATION AND DEGRADATION OF
                                   SAFETY-RELATED BATTERY CELLS


Addressees:

All holders of operating licenses or construction permits for nuclear power 
reactors.

Purpose:

This information notice is being provided to alert addressees to reports of 
contamination and degradation of safety-related battery cells.  It is expected 
that recipients will review the information for applicability to their facili-
ties and consider actions, as appropriate, to avoid similar problems.  However, 
suggestions contained in this information notice do not constitute NRC require-
ments; therefore, no specific action or written response is required.

Description of Circumstances:

Several licensees for nuclear power plants have identified contamination and 
degradation of safety-related battery cells that resulted in decreased station 
battery voltages.  This information notice details such discoveries at the 
Peach Bottom Atomic Power Station, Unit 2; St. Lucie Plant, Units 1 and 2; and 
the Duane Arnold Energy Center.

Copper Contamination

On July 29, 1988, the Philadelphia Electric Company (PECo) reported to the NRC 
pursuant to 10 CFR Part 21 that it had discovered copper contamination on the 
negative plates of the station batteries at its Peach Bottom Atomic Power 
Station, Unit 2.  The station batteries at the Peach Bottom station are 
125-volt direct current (dc) Exide Corporation GN-23 batteries.  Similarly in 
1987, Florida Power & Light Co. (FP&L) personnel noted that approximately 97 
out of 240 safety-related battery cells at the St. Lucie Plant, Units 1 and 2, 
showed signs of discoloration and copper contamination.  The batteries at the 
St. Lucie Plant are 125-volt C&D Power Systems, Inc., type LC-33.  

The copper contamination at the Peach Bottom and St. Lucie plants was caused by
the battery electrolyte attacking the copper inserts in the cells' positive 
terminal posts.  The copper inserts improve the current-carrying capability of 
the posts and are normally isolated from attack by the electrolyte by a lead 
coating.  According to Exide and C&D, the copper does not remain isolated from 



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electrolyte attack throughout the design life of the cell if improper alignment 
or casting occurred at the time of manufacture.  For example, gases caught in 
the lead coating during the casting and freezing involved in the manufacturing 
process may later develop into perforations that become a path between the 
battery electrolyte and the copper inserts.

The battery electrolyte attacks all copper and cupric alloys, causing copper to 
deposit on the negative plates of the affected cell.  The first typical indica-
tion of copper contamination is the discoloration, a pinkish-red color, of the 
negative plates and straps, and as the contamination progresses, the discolora-
tion works its way down the negative plates.  This condition can quickly lead 
to loss of battery capacity and serious deterioration. 

At Peach Bottom, Unit 2, a total of 19 cells in four station batteries 
exhibited copper contamination.  PECo revised the Peach Bottom station battery 
surveil-lance tests to include checks for signs of discoloration on the negative 
plates during testing of cell voltages and specific gravity.

FP&L, based on C&D recommendations, augmented its Technical Specification 
surveillances for safety-related battery cells until replacement of all cells 
showing signs of contamination was completed.  The additional surveillances 
included (1) weekly visual inspections of each cell to monitor the extent of 
copper buildup on the negative plates; (2) weekly voltage monitoring and 
trending of all cells exhibiting signs of copper contamination, including 
recording the temperature, specific gravity, and electrolyte level of each of 
these monitored cells; and (3) weekly monitoring and trending of battery 
terminal voltages.

Degradation

In late 1986, personnel at the Duane Arnold Energy Center (DAEC) observed 
crumbling or eating away of the positive plates on 12 out of 120 cells in 
the station battery.  The degradation is believed to have been caused by a 
galvanic reaction from impurities in the plate weld materials.  The battery 
cells are 250-volt dc GNB Batteries, Inc. (formerly Gould, Inc.), Model FPS-17.  

The degradation consisted of crumbling or eating away of positive plates approx-
imately 1 to 2 inches below the welded connection of the positive plate to the 
cell's internal positive bus bar.  According to DAEC personnel, the crumbling 
appears to have originated at the edge of the plate and to have worked inward, 
thus reducing the plate-to-bus bar junction area.  The GNB representative noted 
that the severely degraded areas took on a brown appearance as opposed to the 
normal flat black color.  Sparkling was also noted when a light was shone on 
the degraded areas, indicating sulfation.  After the initial inspection, GNB 
deter-mined that 14 cells were significantly degraded.

The degradation at DAEC progressed rapidly after its discovery.  In one in-
stance, a cell noted to be 50 percent to 75 percent degraded was reexamined 
less than 72 hours later and was found disconnected from the bus bar.  Although
the exact root cause of the degradation was not determined, it is believed that 
impurities introduced into the plates during the welding process, combined with 
aging, resulted in the galvanic reaction.  GNB noted that high temperatures may 
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accelerate the degradation.  DAEC indicated that the degraded cells were 
located in the upper tier of the two tier-rack, approximately 2 feet higher 
than the cells in the lower rack.  In addition, the ventilation in the battery 
cell room may not have been sufficient and may have contributed to the 
degradation rate.

DAEC augmented its battery cell inspections after the initial degradation was 
identified to include daily visual inspections of degraded cells and biweekly 
inspections of non-degraded cells.  Periodic cleaning of all the battery termi-
nals also was incorporated into the preventive maintenance program.

Discussion:

Station batteries provide a reliable source of dc current for many safety-
related functions.  Degradation and contamination, as described above, can 
render the station batteries incapable of delivering sufficient capacity to 
perform these functions.  In most instances, normal battery surveillance pro-
grams including total battery voltage, individual cell voltage, electrolyte 
specific gravity, level and temperature, and visual inspections, are the best 
indicators of the overall physical condition of a battery and are capable of 
identifying cell degradation or contamination.  In cases in which degradation 
or contamination occur, the battery vendor plays an important role in providing 
the appropriate recommendations and in determining the root cause of a problem.  
Once degradation or contamination is identified, an augmented surveillance 
program may be necessary to monitor the battery condition and to estimate when 
replacement of cells may be needed. 

Additional guidance on battery surveillance requirements is provided in the 
Institute of Electrical and Electronics Engineers (IEEE) Standards 540-1975 and 
1980, "IEEE Recommended Practice for Maintenance, Testing and Replacement of 
Large Lead Storage Batteries for Generating Stations and Substations."                 

No specific actions or written response is required by this information notice.  
If you have any questions about this matter, please contact the technical 
contact listed below or the Regional Administrator of the appropriate regional 
office. 




                                   Charles E. Rossi, Director
                                   Division of Operational Events Assessment
                                   Office of Nuclear Reactor Regulation

Technical Contact:  Jaime Guillen, NRR
                    (301) 492-1170

Attachment:  List of Recently Issued NRC Information Notices
..                                                            Attachment 
                                                            IN 89-17
                                                            February 22, 1989
                                                            Page 1 of 1

                             LIST OF RECENTLY ISSUED
                             NRC INFORMATION NOTICES
______________________________________________________________________________
Information                                  Date of 
Notice No._____Subject_______________________Issuance_______Issued to_________

89-16          Excessive Voltage Drop        2/16/89        All holders of OLs
               in dc Systems                                or CPs for nuclear
                                                            power reactors.

89-15          Second Reactor Coolant Pump   2/16/89        All holders of OLs
               Shaft Failure at Crystal                     or CPs for nuclear
               River                                        power reactors.

89-14          Inadequate Dedication         2/16/89        All holders of OLs
               Process for Commercial                       or CPs for nuclear
               Grade Components Which                       power reactors. 
               Could Lead to Common Mode
               Failure of a Safety System

89-13          Alternative Waste Management  2/8/89         All holders of NRC
               Procedures in Case of Denial                 specific licenses.
               of Access to Low-Level Waste
               Disposal Sites

89-12          Dose Calibrator Quality       2/9/89         All NRC medical
               Control                                      licensees.

89-11          Failure of DC Motor-Operated  2/2/89         All holders of OLs
               Valves to Develop Rated                      or CPs for nuclear
               Torque Because of Improper                   power reactors.
               Cable Sizing

89-10          Undetected Installation       1/27/89        All holders of OLs
               Errors In Main Steam Line                    or CPs for BWRs.
               Pipe Tunnel Differential
               Temperature-Sensing Elements
               at Boiling Water Reactors.

89-09          Credit for Control Rods       1/26/89        All holders of OLs
               Without Scram Capability                     or CPs for test and
               in the Calculation of the                    research reactors.
               Shutdown Margin

89-08          Pump Damage Caused by         1/26/89        All holders of OLs
               Low-Flow Operation                           or CPs for nuclear
                                                            power reactors.

______________________________________________________________________________
OL = Operating License
CP = Construction Permit 
..
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