SSINS No.: 6830 Accession No.: 8002280662 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 May 13, 1980 IE Circular No. 80-11 EMERGENCY DIESEL GENERATOR LUBE OIL COOLER FAILURES Description of Circumstances: Within a two week period (August 27 to September 11, 1979), the tube sheets failed in the lube oil coolers of both emergency diesel generators for Arkansas Nuclear One (ANO) Unit No. 1. The introduction of water into the diesel lube oil system resulted in trips of both diesels during surveillance testings. The diesels were not considered capable of sustained operation. These events were previously identified to all operating license and construction permit holders by Information Notice 79-23, Emergency Diesel Generator Lube Oil Cooler on September 26, 1979. The emergency diesel generators involved were manufactured by the Electro-Motive Division (EMD) of the General Motors Corporation and the failures occurred on engines 71-A1-1117 and 71-A1-1130. The failed lube oil coolers were manufactured by the Young Radiator Company. An analysis of the failed coolers performed by EMD resulted in the conclusion that the failures were caused by severe corrosion of the solder which sealed the tubes to the tube sheets. The corrosion inhibitor in use at ANO was Calgon CS, a borate-nitrite type inhibitor. The manufacturer of this type of inhibitor has recommended the use of hard solder in CS treated systems. EMD does not recommend the use of the Calgon CS since the puddle solder used in EMD radiators and oil coolers is considered to be soft solder of a lead-tin composition. Recommended Action for Licensee's Consideration: Based on the above, it is recommended that licensees: 1. Verify that the corrosion inhibitor used in cooling water systems of the emergency diesel generators is compatible with all materials wetted by the cooling water and the engine manufacturer's specific recommendations. Also, by means of the engine maintenance history, verify that the system corrosion inhibitor has been properly monitored and maintained at the recommended concentration. 2. If Item 1 cannot be successfully performed, the affected components should be inspected in accordance with the manufacturer's recommendations. . IE Circular No. 80-11 May 13, 1980 Page 2 of 2 No written response to this Circular is required. If you desire additional information regarding this matter, contact the Director of the appropriate NRC Regional Office.
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