Information Notice 1991-46, 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
NRC INFORMATION NOTICE NO. 91-46: DEGRADATION OF EMERGENCY DIESEL
GENERATOR FUEL OIL DELIVERY SYSTEMS
Addressees
- .
All holders of operating licenses or.construction permits for nclear -power
reactors..
Purpose
This information notice is intended to alert addressees to otential
i
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 Pubiic Service, discovered paint in the
ports for the EDG fuel pump fuel oil metering rods, making the. EDG inoper- able, because the paint would most likely have prevented operation.of the
fuel oil injection system.
(LER 50-530/90-03)
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IN 91-46 July 18, 1991 Byron Unit 1:
On March 28, 1989, while the unit was operating at
80 PeFiFof 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 ventila-tion 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 w'as operating
at full power, the licensee, Florida Power and Light, declared its B.
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 particu- late matter in the filter.
(LER 50-250/88-22)
Ginna: On February 20, 1987, while the unit was shut'down- and with all
sfalton electrical power being supplied by the EDGs, the licensee, Rochester 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: OnJuly 26, 1990, with both units operating at full
power, te Tcensee, Pennsylvania Power and Light, declared an EDG. inoper- able 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
, 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
IN 91-46 July 18, 1991 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 aIccor- dance 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 forka
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
yrevision of
the amendment that-included changes in addition to this test substitution,,
The' filter cleanliness test is designed to measure particulate contamina-,'.:
tion 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, 1'990, 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 50-275/88-145
IN 91-46 July 18, 1991 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 opera- tions performed on the fuel.deli'very system is important. The subject of
filter maintenance was previously discussed in NRC 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
icontamination) lies in
its potential for clogging filters, strainers, and fuel injection equipment
through which the fuel oil. must flow and thus..causing 'engine fai'lure.
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 yieldsoluble and.'
insoluble gums.
The second way is clustered microbiological growth of.bacte- ria, fungi, or yeasts.ot the interface of the fuel oi.l 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 mate- rials, 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 requiriements 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-rrepre- sentsthe year of the modification used, for testing the quality qf 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, viscos.ity, 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 Contam- inant ian Aviation Turbine Fuels," ASTM-D2276-XX. The American Nuclear Society
(ANS) in its standard approved bythe American National Standards Institute
(ANSIS, "Fuel Oil Systems for Emergency Diesel Generators," ANS.I/ANS-59.51-1989, recommends in AppendixtC 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
IN 91-46 July 18, 1991 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 st-Ne 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 contami- nation 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 individ- ual 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.
harles ~E.Ross
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
Attachment 1
-
July 18, 1991
Page 1- of 1
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
91-45
Possible Malfunction of
Westinghouse ARD, BFD, and
NBFD Relays, and A200 DC
and DPC 250 Magnetic Con- tactors
07/05/91 All holders
for nuclear
power reactors.
91-44
91-43
91-42
91-41
Improper Control of
Chemicals in Nuclear Fuel
Fabrication
Recent Incidents Involving
Rapid Increases in Primary- to-Secondary Leak Rate
Plant Outage Events
Involving Poor Coordina- tion Between Operations
and Maintenance Personnel
During Valve Testing and
Manipulations
Potential Problems with
The Use of Freeze Seals
High Radiation Hazards
from Irradiated Incore
Detectors and Cables
Contamination of Non- radioactive System and
Resulting Possibility for
Unmonitored, Uncontrolled
Release to the Environment
Compliance with 10 CFR
Part 21,
"Reporting of
Defects and Noncompliance"
Thermal Stratification in
Feedwater System Piping
07/08/91 All nuclear fuel facilities.
07/05/91
All holders of OLs or CPs
for pressurized-water
reactors (PWRs).
06/27/91
All holders of OLs or CPs
for nuclear power reactors.
06/27/91
All holders of OLs or CPs
for nuclear power reactors.
06/25/91
All holders of OLs or CPs
for nuclear power reactors, research reactors, and
test reactors.
06/19/91
All holders of OLs or CPs
for nuclear power reactors.
06/17/91
All Nuclear Regulatory
Commission (NRC) material
licensees.
06/13/91
All holders of OLs or CPs
for nuclear power reactors.
88-63, Supp. 2
91-40
91-39
91-38 OL = Operating License
CP = Construction Permit