United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 91-46: Degradation of Emergency Diesel Generator Fuel Oil Delivery Systems

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF NUCLEAR REACTOR REGULATION
                           WASHINGTON, D.C.  20555

                                July 18, 1991


Information Notice No. 91-46:  DEGRADATION OF EMERGENCY DIESEL 
                                   GENERATOR FUEL OIL DELIVERY SYSTEMS 


Addressees:

All holders of operating licenses or construction permits for nuclear power 
reactors.

Purpose:

This information notice is intended to alert addressees to potential 
inoperability of multiple emergency diesel generators (EDGs) resulting from 
common cause degradations:  (1) degraded fuel oil delivery systems and (2) 
failure to meet Technical Specification (TS) testing requirements intended 
to detect potentially degraded quality of the fuel oil stored on site.  It 
is expected that recipients will review the information for applicability to 
their facilities and consider actions, as appropriate, to avoid similar 
problems.  However, suggestions contained in this information notice do not 
constitute NRC requirements; therefore, no specific action or written 
response is required.

Description of Circumstances:

Over the past four years, several licensees have submitted licensee event 
reports (LERs) describing degradations in EDG operability or other 
safety-related equipment attributable to problems with the fuel oil system.  
Descriptions of selected LERs are presented below to illustrate three 
classes of problems.

I.   Inappropriate painting of fuel injection assemblies

     McGuire Unit 1:  On June 25, 1990, while the unit was operating at full 
     power, the licensee, Duke Power, declared two EDGs inoperable on 
     discovery that paint had been inappropriately sprayed on the exciter 
     commutator rings and on the back side of the fuel rack pivot points.  
     This condition prevented the EDG output from attaining the TS-required 
     4160 volts in the allotted time (11 seconds).  (LER 50-369/90-17-01)

     Palo Verde Unit 3:  On March 28, 1990, while the unit was operating at 
     full power, the licensee, Arizona Public Service, discovered paint in 
     the ports for the EDG fuel pump fuel oil metering rods, making the EDG 
     inoperable, because the paint would most likely have prevented 
     operation of the fuel oil injection system.  (LER 50-530/90-03)


9107110017 
.

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     Byron Unit 1:  On March 28, 1989, while the unit was operating at 80 
     percent of full power, the licensee, Commonwealth Edison, discovered 
     that an EDG failed to start during the monthly surveillance test 
     because inappropriately applied paint was binding the fuel oil metering 
     rods and thus preventing the EDG from getting enough fuel oil to start.  
     (LER 50-327/89-25)

II.  Fouling of fuel oil filters or strainers 

     Dresden Unit 2:  On December 24, 1988, while the unit was shut down, 
     with all the reactor fuel removed from the reactor vessel, and with 
     both reactor protection system (RPS) buses being powered from one EDG, 
     the EDG frequency decreased below the setpoint of the underfrequency 
     relays associated with the motor-generator sets.  When the relays 
     actuated, the RPS buses were deenergized, resulting in a scram signal 
     on both RPS channels.  The standby gas treatment system was 
     automatically initiated and the reactor building ventilation system was 
     automatically isolated.  The licensee, Commonwealth Edison, determined 
     the root cause to be a fouled fuel oil filter.  (LER 50-237/88-20)

     Turkey Point Unit 3:  On September 20, 1988, while the unit was 
     operating at full power, the licensee, Florida Power and Light, 
     declared its B EDG inoperable due to high fuel oil pressure.  At the 
     time of the event, Unit 4 was shut down and the A EDG was out of 
     service for maintenance.  The licensee determined the root cause to be 
     an excessive interval between fuel oil filter replacements that allowed 
     gradual accumulation of particulate matter in the filter.  
     (LER 50-250/88-22)

     Ginna:  On February 20, 1987, while the unit was shut down and with all 
     station electrical power being supplied by the EDGs, the licensee, 
     Roches-ter Gas and Electric, discovered low fuel oil levels in both day 
     tanks because the fuel oil transfer pump suction strainers were 
     partially plugged.  The particulate contamination was analyzed as weld 
     flux from plant construction activities and fibrous material from 
     either cleaning rags or filter media.  The licensee had to drain and 
     flush the fuel transfer pump suction piping several times to prevent 
     plugging of the strainers when the fuel oil from the storage tanks was 
     recirculated.  (LER 50-244/87-01)

III. Potential degradation of fuel oil quality, as measured by licensees' TS 

     Susquehanna Unit 1:  On July 26, 1990, with both units operating at 
     full power, the licensee, Pennsylvania Power and Light, declared an EDG 
     inoperable because a sample of fuel oil from a storage tank exceeded 
     its TS limit for the concentration of insoluble matter (2 mg/100 ml, 
     using the ASTM-D2274-70 oxygen accelerated stability test), indicating 
     a loss of stability of the stored fuel oil.  (LER 50-387/90-15)

     Perry Unit 1:  On April 5, 1990 (LER 50-440/90-05-01), and on January 
     11, 1989 (LER 50-440/89-01-01), the licensee, Cleveland Electric 
     Illumination, declared safety-related equipment inoperable because a 
     sample of fuel oil from a storage tank exceeded its TS limit for the 
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     concentration of insoluble matter (2 mg/100 ml, using the ASTM-D2274-70 
     test).  In April 1990, the licensee declared its high-pressure core 
     spray system inoperable while the unit was operating at full power and 
     in January 1989, the licensee declared an EDG inoperable while the unit 
     was operating at 70 percent of full power.  In the April 1990 event, 
     the licensee attributed the degradation to a contaminant found in the 
     biocide additive and to degradation of the material coating the storage 
     tank.  In January 1989, the licensee believed the fuel oil aging was 
     accelerated by the addition of new fuel oil a few days before the 
     event.  

     WNP Unit 2:  On January 3, 1990, while the unit was operating at full 
     power, the licensee, Washington Public Power Supply, declared all three 
     of its EDGs inoperable, because an EDG fuel oil test of samples drawn 
     on December 27, 1989, indicated that the fuel oil in all three storage 
     tanks did not meet the oxygen accelerated stability criterion, and 
     entered the limiting condition of operation (LCO) for TS 3.0.3.  At the 
     time of this report, the licensee's TS required that EDG fuel oil be 
     tested in accordance with the standard ASTM-D2274-70, with particulate 
     contamination not exceeding 2 mg/100 ml.  The licensee reviewed past 
     surveillance results, which were typically half the TS limit, found no 
     discernible trends, and consulted two fuel oil experts, who indicated 
     that no reason existed for a step increase in the stability measure.  

     The licensee believes the root cause of this event to be the fuel oil 
     analysis method.  The licensee submitted an emergency amendment, which 
     included the substitution of a filter cleanliness test based on the 
     standard ASTM-D2276-78, Method A, with particulate contamination not 
     exceeding 10 mg/l, for the oxygen accelerated stability test based on 
     ASTM-D2274-70.  On March 30, 1990, the NRC temporarily approved the 
     amendment.  On June 4, 1990, the NRC permanently approved a revision of 
     the amendment that included changes in addition to this test 
     substitution.  The filter cleanliness test is designed to measure 
     particulate contamination existing in the fuel oil whereas the oxygen 
     accelerated stability test is designed to measure the potential of the 
     fuel oil for forming gums, varnishes, and tars in the future.  The 
     filter cleanliness test results for the samples of fuel oil drawn on 
     December 27, 1989, were acceptable.  Results of both the oxygen 
     accelerated stability test and the filter cleanliness test for samples 
     drawn from both tank bottoms and transfer pump discharges on January 2, 
     1990, and on January 3, 1990, were acceptable.  (LER 50-397/90-01)

     Diablo Canyon Unit 1:  On May 5, 1988, while the unit was shut down, 
     the licensee, Pacific Gas and Electric, observed the power output of an 
     EDG to decrease below the licensee's acceptance criterion for a 24-hour 
     load test.  The licensee determined that the primary fuel oil filter 
     had become clogged with a fungus growing in the day tank supplying that 
     EDG.  The licensee also found fungus and spores in the other day tanks 
     and in the fuel oil storage tanks.  The licensee added a biocide and 
     filtered the fuel oil in the day tanks until its acceptance criteria 
     were met for flash point, gravity, viscosity, and particulate 
     contamination (10 mg/l, using the ASTM-D2276-78, Method A, particulate 
     contamination test).  (LER 50-275/88-14)
.

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Discussion:

The lessons to be learned from the LERs that deal with inappropriate 
painting incidents are self-evident.  Similarly, the LERs that deal with 
partially plugged fuel oil filters or strainers show that regular and 
careful maintenance of these components is important to reliable EDG 
operation.  In particular, these LERs show that the period of time between 
replacement of filters and strainers should not be excessive and that 
cleanliness of maintenance operations performed on the fuel delivery system 
is important.  The subject of filter maintenance was previously discussed in 
Information Notice No. 87-04, "Diesel Generator Fails Test Because of 
Degraded Fuel."  Some of the LERs on TS testing problems are concerned with 
actual degradations of fuel oil quality but primarily address the particular 
test used in the TS.  

The main concern with degraded EDG fuel oil (particulate contamination) lies 
in its potential for clogging filters, strainers, and fuel injection 
equipment through which the fuel oil must flow and thus causing engine 
failure.  All fuel oil tends to degrade in two general ways during extended 
storage.  The first way is oxidation and polymerization of the fuel oil to 
yield soluble and insoluble gums.  The second way is clustered 
microbiological growth of bacteria, fungi, or yeasts at the interface of the 
fuel oil and water present at the bottom of the storage tank.  Through 
chemical processes, the bacteria produce solids and additional water.  The 
bacterial solids may accumulate in the bottom of the fuel storage tank and 
not pose a problem for EDG operability until the fuel transfer pump draws 
them into its suction pipe.  All these solid materials, the gums, the 
microbiological growth, and the bacterial sludge, as well as foreign debris, 
are collectively called particulate contamination.  

Focusing on the question of degraded fuel oil quality, note that several 
standards are used in individual plant TS requirements for testing EDG fuel 
oil.  Most plants use the American Society for Testing and Materials (ASTM) 
"Standard Specification for Diesel Fuel Oils," ASTM-D975-XX, where XX repre-
sents the year of the modification used, for testing the quality of fuel 
oil, both freshly delivered and stored.  It includes tests for a number of 
fuel properties, including flash point, cloud point, distillation 
temperature, water and sediment content, carbon residue, ash content, sulfur 
content, viscosity, corrosive potential, and Cetane number (ignition 
quality).  Some plants' TS only require the water, sediment, and viscosity 
tests.  Some plants' TS contain a requirement for the oxygen accelerated 
stability test described in "Standard Test Method for Oxidation Stability of 
Distillate Fuel Oil (Accelerated Method)," ASTM-D2274-XX, and some plants' 
TS contain a requirement for the particulate contamination test described in 
"Standard Test Methods for Particulate Contaminant in Aviation Turbine 
Fuels," ASTM-D2276-XX.  The American Nuclear Society (ANS), in its standard 
approved by the American National Standards Institute (ANSI), "Fuel Oil 
Systems for Emergency Diesel Generators," ANSI/ANS-59.51-1989, recommends in 
Appendix C the ASTM-D2276-XX particulate contamination test.

The ASTM-D975 standard is intended as a statement of permissible limits of 
significant fuel properties used for specifying the wide variety of 
commercially available diesel fuel oils.  As such, it most readily applies 
to determination of the quality of new fuel oil, but does not readily apply 
to the question of 
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particulate contamination in stored fuel oil.  The oxygen accelerated 
stability test of the ASTM-D2274 standard predicts the potential for future 
degradation of fuel oil but does not show the existing state of degradation. 
On the other hand, the particulate contamination test of the ASTM-D2276 
standard readily applies to the question of particulate contamination in 
stored fuel oil.  

Revision 4A of the Westinghouse Standard TS (STS) contains comprehensive 
requirements on testing and monitoring the condition of stored EDG fuel oil, 
in which the salient features are (1) use of the ASTM-D2276 particulate 
contamination test and (2) testing for and removal of water.  Some nuclear 
power plants, such as McGuire Units 1 and 2, Wolf Creek, Limerick Units 1 
and 2, and WNP Unit 2, have voluntarily adopted this revision of the STS in 
their individual plant TS.  In the LER for WNP 2 (above), the licensee 
determined that incorporation of this total program in its plant TS was an 
effective corrective action for its problems in determining the quality of 
its stored fuel oil.  The Electric Power Research Institute (EPRI) has 
provided additional guidance on this point in "Storage and Handling of Fuel 
Oil for Standby Diesel Generator Systems," EPRI NP-63140, August 1988.  

This information notice requires no specific action or written response.  If 
you have any questions about the information in this notice, please call one 
of the technical contacts listed below or the appropriate NRR project 
manager.




                                   Charles E. Rossi, Director
                                   Division of Operational Events Assessment
                                   Office of Nuclear Reactor Regulation


Technical Contacts:  Vern Hodge, NRR         Frank Witt, NRR
                     (301) 492-1861          (301) 492-0767

                     Ed Tomlinson, NRR       Pete Prescott, NRR
                     (301) 492-3150          (301) 492-1011


Attachment:  List of Recently Issued NRC Information Notices 
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