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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C. 20555 July 2, 1992 NRC INFORMATION NOTICE 92-48: FAILURE OF EXIDE BATTERIES Addressees All holders of operating licenses or construction permits for nuclear power reactors. Purpose The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to inform addressees of failure of a Type GC battery manufactured by Exide used in safety-related applications and the potential failure of Type GN batteries used in safety-related applications. It is expected that recipients will review the information for applicability to their facilities and consider actions, as appropriate. However, no specific action or written response is required. Description of Circumstances On October 7, 1991, Omaha Public Power District reported cracking on the face of Exide's Class 1E Type GC-23 battery jars installed in February 1980, at the Fort Calhoun nuclear station (Fort Calhoun), causing leakage of electrolyte and subsequent inoperability of the battery. The root cause was attributed to inadequately designed battery terminal post seals. The terminal post radial gland seal cracked due to corrosion buildup which led to cracking on the jar cover and face and subsequent leakage of electrolyte. Discussion Exide discovered the cracking problem in 1982 when the Southern New England Telephone Company informed Exide that the terminal post seals had cracked on a Type GW battery purchased from Exide. Exide's battery Types GC, GN (nuclear grade) and GW had identically designed terminal post radial gland seals. Exide evaluated the problem and determined that the seal between the cover and terminal posts was inadequately designed. Corrosion builds up over time in the seal area at the positive post because electrolyte enters, becomes trapped, and reacts with the post material. The corrosion buildup stresses the seal area and the plastic nut around the seal, and, ultimately, the cell cover cracks. Consequently, in 1983, after notifying all holders of Type GN cells, Exide corrected the design of the seals at the battery terminal. However, due to a time lag in the supply chain, batteries received prior to 1985 may still have been of the old design. The old design is characterized by an eight-sided nut around each battery terminal post. 9206260043. IN 92-48 July 2, 1992 Page 2 of 2 On March 24, 1983, the licensee for the Palo Verde nuclear plant notified the NRC staff of a deficiency in Exide GN batteries involving cracking of the plastic seals/covers at the terminal posts and electrolyte leakage. The notification was based on Exide's service bulletin which addressed this issue for Type GN batteries and suggested three levels of optional field modifications (Levels I, II, and III) to repair batteries installed in nuclear plants. Fort Calhoun had a Level III repair performed because of numerous cracks on the battery covers. The Level III repair technique creates an all-enveloping secondary cover over the cracked cover. However, this repair tends to mask any further cracking until catastrophic battery failure occurs, as was the case at Fort Calhoun when one-third of the electrolyte leaked out and the battery had to be replaced. The NRC wants to inform the nuclear industry that Exide Type GC and GN batteries received prior to 1985 with an eight-sided nut around each battery terminal post may be susceptible to corrosion buildup and subsequent cracking at the positive terminal posts; this condition could ultimately render the battery incapable of performing its intended safety function. This phenomenon could occur regardless of whether or not the batteries had the optional field modifications installed. 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 Reactor Regulation (NRR) project manager. Charles E. Rossi, Director Division of Operational Events Assessment Office of Nuclear Reactor Regulation Technical contacts: Randolph N. Moist: NRR (301) 504-2945 Frederick H. Burrows: NRR (301) 504-2901 Attachment: List of Recently Issued NRC Information Notices .
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