Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
SSINS No.: 6835
IN 87-04
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
January 16, 1987
Information Notice No. 87-04: DIESEL GENERATOR FAILS TEST BECAUSE OF
DEGRADED FUEL
Addressees:
All nuclear power reactor facilities holding an operating license or a
construction permit.
Purpose:
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
required.
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.
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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.
Discussion:
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
fouled.
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
EDGs.
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.
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IN 87-04
January 16, 1987
Page 3 of 3
No specific action or written response is required by this information
notice.
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
Attachments:
1 Figure l - Schematic Fuel Supply System for Emergency
Diesel Generator at Arkansas 2
2. List of Recently Issued IE Information Notices
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