IE Circular No. 80-11, Emergency Diesel Generator Lube Oil Cooler Failures

                                                            SSINS No.: 6830 
                                                            Accession No.: 

                                UNITED STATES
                           WASHINGTON, D.C. 20555

                                May 13, 1980

                                                     IE Circular No. 80-11 


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 

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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