United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 87-04: Diesel Generator Fails Test because of Degraded Fuel

                                                        SSINS No.: 6835 
                                                          IN 87-04        

                                UNITED STATES
                           WASHINGTON, D.C. 20555

                              January 16, 1987

                                   DEGRADED FUEL 


All nuclear power reactor facilities holding an operating license or a 
construction permit. 


This notice is to alert recipients to a potentially significant problem 
pertaining to long-term storage of fuel for diesel engines for emergency 
service. This problem highlights the importance of a carefully structured 
inspection, sampling, and test program to verify continuing acceptability of 
the fuel for emergency use. The NRC expects that recipients will review this 
notice for applicability to their facilities and consider actions, if 
appropriate, to preclude a similar problem occurring at their facilities. 
However, suggestions contained in this notice do not constitute NRC 
requirements; therefore, no, specific action or written response is 

Reference Documents: 

     1.   Licensee Event Report No. 50-368/86-14, "Emergency Diesel 
          Generator Failure Due to Fuel Supply System Fouling as a Result 
          of Fuel Oil Degradation," November 18, 1986 

     2.   IE Circular No. 77-15, "Degradation of Fuel Oil Flow to the 
          Emergency Diesel Generator," November 23, 1977 

Description of Circumstances: 

On June 27, 1986, at Arkansas Nuclear One Unit 2 (ANO 2), one of the two 
emergency diesel generators (EDGs) failed to complete a prescribed 24-hour 
endurance test because of fuel starvation (Reference 1). The licensee found 
the screen element in the Y-strainer between the day tank and the engine 
severely fouled (component B in Figure 1), restricting flow of fuel to the 
engine. Cleaning the element required using a hand-held torch to remove a 
hard carbonaceous coating. The licensee cleaned the tank and piping and 
successfully completed the endurance test. 


                                                           IN 87-04        
                                                           January 16, 1987 
                                                           Page 2 of 3 

The corresponding strainer for the redundant EDG was found to not be as 
severely fouled. The redundant EDG successfully performed a 24-hour 
endurance test begun after the faulted EDG was made operable. 


The licensee visually inspected and cleaned the fuel supply system for each 
EDG as short-term corrective action. In addition, the licensee installed 
temporary piping, pumps, and filters to recirculate and clean the fuel 
inventory. The interior surfaces of the day tanks and underground vault 
tanks had coatings of sludge that were easily removed. The fuel suction line 
foot valves and strainers (component A in Figure 1) did not appear to be 

During the evaluation of the event, the licensee determined that the day 
tank strainers (components A and B in Figure 1) had not been routinely 
inspected and cleaned because the station procedures did not address this 
action. Although these components are identified on the fuel supply system 
piping drawings, they had not been considered in station procedures. The 
licensee also determined that the function of the component B strainers was 
adequately served by the engine mounted strainers (Cuno-type; component C in 
Figure 1), which are capable of removing particulates smaller than the rated 
removal size of the component B strainers and are readily cleaned in 
service. In addition, the Cuno-type strainers are equipped with differential 
pressure indication. Subsequently, in accordance with 10 CFR 50.59, the 
licensee removed the screen element from the component B strainers for both 

The licensee engaged a contract laboratory to analyze the fuel. The 
contractor reported that a high concentration of particulates existed in the 
fuel as a result of oxidation and biological contamination. The licensee 
instituted a program to enhance fuel quality by periodic inspection and 
cleaning of the storage tanks and frequent sampling of the fuel. The 
laboratory strongly recommended use of a proprietary additive to prevent 
oxidation and to inhibit biological growth; however, a decision has not been 
made on the use of any additive. Further, the licensee is considering design 
modifications to include dual filters and strainers and a permanent storage 
tank recirculation system to facilitate filtering of the complete inventory 
each refueling outage. 

It should be noted that the fuel supply systems differed between Unit 1 and 
Unit 2 in the absence on Unit 1 of the day tank strainers (components A and 
B in Figure 1). 

On July 14, 1977, at Cooper, a clogged strainer had caused an EDG to 
similarly starve of fuel oil. This event was described and discussed in 
Reference 2.

                                                            IN 87-04 
                                                            January 16, 1987
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No specific action or written response is required by this information 

If you have any questions about this matter ease contact the Regional 
Administrator of the appropriate regional office or this office. 

                         Edward L. Jordan, Director
                         Division of Emergency Preparedness
                          and Engineering Response
                         Office of Inspection and Enforcement

Technical Contacts: Vern Hodge, IE
               (301) 492-7275

               Jim Henderson, IE
               (301) 492-9654

1 Figure l - Schematic Fuel Supply System for Emergency 
     Diesel Generator at Arkansas 2 
2. List of Recently Issued IE Information Notices 
Page Last Reviewed/Updated Friday, May 22, 2015