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
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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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