Regular testing of the diesel generators leading to electrical components failing in both. God only knows how many components will failed under the stress of a big accident.
This is where we are heading and the NRC knows it. We are going to have LOOP at a nuclear plant and both DGs are going to trip on junk Chinese untraceable electrical components. They don't even tell us when this components were put in?
I telling you, our nuclear industry is having big troubles with non traceable junk Chinese mechanical and electrical components getting into our nuclear plants.
Both Emergency Diesel Generators Declared Inoperable
On August 26, 2015, both Emergency Diesel Generators at
Waterford Steam Electric Station, Unit 3 (Waterford 3) were declared inoperable,
causing entry into Technical Specification 3.8.1.1 action f.
On August 26, 2015, at 0111 CDT, EDG
[DG] 'A' was declared inoperable following a trip of EDG 'A' on Generator Differential
[87]. TS 3.8.1.1 actions b. and d. were entered. EDG 'A' was being run in
accordance with OP-903-115, "Train A Integrated Emergency Diesel
Generator/Engineering Safety Features Test," Section 7.4, "24 hr EDG ‘A’
Run with Subsequent Diesel Start" to satisfy TS Surveillance Requirement (SR)
4.8.1.1.2.e.6. EDG 'B' was subsequently started per TS 3.8.1.1 action b.(1)
which requires the demonstration of Operability of the remaining Operable EDG
to preclude common mode failure of the remaining EDG. At 0740 CDT, EDG 'B' was
declared inoperable and TS 3.8.1.1.f. (restore one of the inoperable EDGs to
Operable status within 2 hours or be in at least Hot Standby within the
following 6 hours) was entered due to the EDG ‘B’ room exhaust fan [FAN] not
starting when the diesel engine was started. Troubleshooting determined that
the EDG ‘B’ room exhaust fan did not start due to HVR-501B (EG B ROOM OUTSIDE
AIR INTAKE DAMPER) [DMP] not opening. Action was taken to isolate air and fail
HVR-501B to its open safety position. At 1001 CDT, EDG 'B' was declared operable
and TS 3.8.1.1.f. was exited following verification of proper operation of the
EDG 'B' room exhaust fan. The station remained in TS 3.8.1.1.b. and d. with EDG
‘A’ remaining inoperable.
The amount of time that both EDGs were
inoperable was 2 hours and 20 minutes. During this time, a brief was conducted
and preparations for a plant shutdown were completed. Prior to exceeding the
allowed outage time, EDG 'B' damper HVR-501B was failed open and the room
exhaust fan started.
EDG ‘A’ Generator Differential
EDG 'A' was being run in accordance with
OP-903-115, "Train A Integrated Emergency Diesel Generator/Engineering Safety Features
Test," Section 7.4, "24 hr EDG ‘A’ Run with Subsequent Diesel
Start" to satisfy TS SR 4.8.1.1.2.e.6. The EDG function of supplying
standby electrical power on receipt of a “test” or “emergency” command signal
are different in that during an Emergency Mode start of the EDG, all Test Mode
trips and alarms are bypassed with the exception of overspeed and generator
differential.
The direct cause for EDG ‘A’ tripping on
GENERATOR DIFFERENTIAL was the internal shorting of EG ECT2316 C TRANSF, NB8
Current Transformer, due to insulation failure.
The EG ECT2316 C TRANSF is a
Westinghouse type KIR-60 current transformer style 7524A01G16 with serial number
28218571. There are no lot or date codes printed on the current transformer or
its nameplate. The current transformer is only energized when EDG ‘A’ is
supplying the 3A bus.
A vendor performed a failure analysis of
the failed EG ECT2316 C TRANSF, current transformer and issued a failure
analysis report dated October 9, 2015. The report concluded that the failure
was due to a manufacturing defect. Specifically, there were voids found in the
insulation and the thickness of the insulation material around the fault area
appeared reduced when compared to the other areas of the current transformer.
It is believed that the thinner insulation in combination with voids increased
the electrical stresses causing the insulation to break down. This eventually
resulted in a fault. The insulation breakdown and resultant fault created a
ground condition on the Diesel Generator bus.
10 CFR 21 IDENTIFICATION
On October 9, 2015, Waterford 3 received
information from the external evaluation concerning the Generator Differential
Current Transformer. The evaluation concluded that a manufacturing defect
internal to the current transformer was the cause of the failure. On October
22, 2015, engineering evaluation determined the manufacturing defect could
create a substantial safety hazard, as defined in 10 CFR 21, and provided the
site vice president information of the defect the same day. Additional
information identified in the report is as follows: Constructor - Westinghouse
Type KIR-60 current transformer, style 7524A01G16, serial number 28218571; Defect
and safety hazard - There were voids found in the insulation, and the thickness
of the insulation material around the fault area appeared reduced when compared
to the other areas of the current transformer. There is only one transformer of
this type remaining installed in the plant. Scheduled replacement is no later
than November 15, 2015.
EDG ‘B’ HVR 501B failure
On August 26, 2015,
EDG 'B' was started per TS 3.8.1.1 action b.(1) which requires the
demonstration of Operability of the remaining Operable EDG to preclude common
mode failure of the remaining EDG. At 0740 CDT, EDG 'B' was declared inoperable
and TS 3.8.1.1.f. (restore one of the inoperable EDG's to Operable status
within 2 hours or be in at least Hot Standby within the following 6 hours) was
entered due to the room exhaust fan not starting when the diesel engine was
started. Troubleshooting determined that the EDG ‘B’ room exhaust fan did not start
due to HVR-501B (EG B ROOM OUTSIDE AIR INTAKE DAMPER) not opening. The solenoid
on HVR-501B was replaced and tested satisfactorily. The solenoid was inspected
on site both externally and internally and it was determined that there was
mechanical wear on the inside of the solenoid, the air inlet valve plug was
bound up inside the solenoid coil, and that the solenoid coil itself appeared
to be good. Photographs of the condition were sent to an offsite vendor who
concluded that rapid cycling of the solenoid valve might be the cause of the
excessive wear and damage to the components...
These guys had some big LER recently. Obviously this is a direct offshoot of my "Mike Mulligan River Bend special inspection. Basically a inability to control reactor water level over long periods of time. This is identical to River Bends problems. It is really sickening...
Licensee Event Report (LER)2015-004-01, Emergency Feedwater System Flow Oscillations and LER 2015-005-01,
Manual Reactor Trip due to Low Steam Generator Levels Waterford Steam Electric
Station, Unit 3 (Waterford 3)
The safety function of the
EFW system is to provide sufficient supply of cooling water to one or both SGs for
the removal of decay heat from the Reactor Coolant System (RCS) [AB] in
response to any event causing low SG level coincident with the absence of a low
pressure trip.
INITIAL CONDITIONS
On June 3, 2015, Waterford 3
was in Mode 1 at approximately 100% power. There were no structures, components,
or systems that were inoperable at the start of the event that contributed to
the event.
The manual reactor [RCT]
trip due to low SG levels is reported in LER-WF3-2015-0005.
EVENT DESCRIPTION At 1704 on
June 3, 2015, Waterford 3 experienced a loss of the “A” Main Feedwater Pump. At
1705, the reactor was manually tripped when SG levels were continuing to lower.
At 1707, an EFAS [JE] was automatically actuated to both SGs as SG level
decreased. Flow initially stabilized at 250 gpm with the Primary Flow Control
Valves (PFCVs) [FCV] providing flow and the BFCVs [FCV] closed. Both SG levels continued
to decrease and the EFW [BA] control logic shifted the operation of the BFCVs
to flow control mode to maintain flow to each SG. EFW flow stabilized and then
SG levels began recovering. At 1709, the EFW AB pump [P] reached rated speed
and EFW header discharge pressure increased. Shortly afterward, wide, frequent
fluctuations in EFW flow were observed which was not in accordance with the expected
system response.
Operations personnel
observed that the controller [FIK] outputs for both BFCVs were oscillating
frequently and widely. Both PFCVs operated correctly in automatic (the
controller outputs remained steady and the valves remained in their fixed
position). To prevent further oscillations, both BFCV controllers were taken to
manual and then closed at 1715. The oscillations stopped concurrent with taking
the valves to manual control. Operations personnel cycled both BFCVs in manual
with no further flow oscillations noted. After confirming that they could
control both BFCVs in manual, the operators closed the PFCVs. EFW flow to the
SGs was controlled by operation of both BFCVs in manual for the remainder of
the event, until EFW was secured.
The EFW flow control logic
[JB] and both BFCVs were declared INOPERABLE due to the FCV oscillation and
actions per TS 3.3.2.b and 3.7.1.2.d were entered, respectively. The EFW system
functioned adequately to fill the SGs and maintain the specified safety function
(Reactor Coolant System Heat Removal).
This event and the manual reactor
trip were immediately reportable (reference EN # 51116) under 10 CFR 50.72(b)(3)(iv)(A),
Specified System Actuation, and 10 CFR 50.72(b)(2)(iv)(B), RPS Actuation
(scram), respectively. Investigation has revealed that the components
comprising the EFW flow control system were not configured to appropriately
respond to the changes observed in the system operating parameters. Both EFW
BFCVs cycled more than assumed in the nitrogen accumulator [ACC] sizing
calculation. The excessive cycling has the potential for exhausting the
accumulators prior to their 10 hour analyzed mission time in the event of a
loss of Instrument Air (IA) [LD]. These accumulators also supply backup
nitrogen to the ADVs. Periodic testing
to confirm the stability of the BFCVs in the automatic flow control mode has not
been performed. It is therefore reasonable to assume that this condition has
likely existed within three…
CAUSAL FACTORS
A root cause evaluation was
completed for this condition. The direct cause of this condition was an
instability in the control system setup of the EFW BFCVs that occurred when the
valves were operating in the flow control mode. This resulted in the continuous
cycling of the EFW BFCVs.
The root cause of this event
was that the components comprising the EFW flow control system were not configured
to appropriately respond to the changes observed in the system operating
parameters.
Analysis has concluded that
the unstable behavior seen in the flow control mode is explained if the valve gain
or controller gain was improperly selected for both loops. With the gain
improperly selected, a perturbation in EFW flow would have caused a feedback
effect that would have setup a varying output signal to the FCVs. The analysis
eliminated all other potential causes except the following all tied to system
gain:
Controller
proportional gain and reset interval
Valve
trim (linear) results in greater than desirable flow when the valve is
operating close to its seat
Valve
stroke time set too fast
Volume
booster setup improper for both valves.
Follow on corrective actions
are assigned to determine the sensitivity of the control system to these parameters
and to determine if the potential identified causes may have shifted the system
to unstable operation. These actions are also directed to determine
One contributing cause of
this event was that there is no periodic testing that confirms the stability of
the BFCVs in the automatic flow control mode. No startup test exists where the
system was allowed to shift the BFCVs to the flow control mode and control in
this mode. Calibration checks of the flow control loops and actuator are
periodically performed; however, these tests do not provide sufficient
intrusiveness to determine instabilities in system operation in all modes.
A second contributing cause
of this event is that previous corrective actions were ineffective at determining
the cause of the EFW flow instabilities and confirming the oscillations were
corrected. EFW flow oscillations of similar magnitude and frequency were
observed following a plant trip on January 21, 2013. There were missed
opportunities noted in response to this event that may have led to earlier discovery
of the causes.
Entergy spent a lot of money
on this violation getting them to downplay it. Basically NRC inspectors walked to
the roof and found it before Entergy did.
During a walkdown of the Emergency Diesel Generator Feed Tank A and B vent lines on October 22, 2014, an NRC Component Design Basis Inspection inspector identified corrosion on the Emergency Diesel Generator Feed Tank A and B vent lines where the vent lines pass through the roof. A visual inspection was performed and revealed that the corrosion had created through wall holes that could allow water into both the train A and B Emergency Diesel Generator Feed Tanks.
Follow up analysis has determined that some rainfall amount less than the postulated Probable Maximum Precipitation event could have resulted in water intrusion into the Emergency Diesel Generator A and B Feed Tanks that exceeds the 0.1 percent water content allowed by the vendor technical manual. This could have potentially affected the operability of both the A and B Train Emergency Diesel Generator Feed Tanks and subsequently both trains of the Emergency Diesel Generators. It is unknown how long this corrosion has existed. Compensatory measures were put in place to prevent water ingress should a large rainfall event occur.
Junk plant operators and maintenance people. The operators inspect that room at least every 8 hours. They didn't find filter housing on the floor in two days. They should have tested their assertion of operability in trying to start up DG without the filter housing attached?
Just saying over a few years...these guys got a amazing record of unreliability with their DGs!!!! Amazing record...
Licensee Event Report (LER)2014-002-00 Inadequate Tightening of
Starting Air Filter Housing results in Inoperable Train A Emergency Diesel
Generator During an operator tour of the
train A Emergency Diesel Generator (EDG) room on March 1,2014 at approximately 12:39,
it was discovered that the filter housing cover on the EDG A Starting Air
Filter had unfastened from its base and was lying on the floor. The last
successful start of the EDG A that demonstrated its capability to meet its
safety function was on February 27, 2014 at 11:33 and it is postulated that the
cover became unfastened during that run. Therefore, EDG was potentially
inoperable for 2 days as a result of this condition. Since the condition was
unknown at the time, the Technical Specifications required test of EDG B was
not performed within 8 hours and the requirement to demonstrate the operability
of the remaining A.C. circuits at least once per 8 hours or to be in Hot
Shutdown within the next 6 hours was not performed. The cause was insufficient
tightening of the filter housing cover during maintenance on April 8, 2013. The
insufficient tightening had not been preventing the EDG A’s ability to start
within the required times prior to its becoming unfastened. EDG A was returned
to OPERABLE condition by refastening the filter housing cover to its base. The
other filter housings on EDG A and EDG B were verified to be properly fastened.
An evaluation is being conducted to determine if a torque requirement is
necessary for the filter housing covers…
Basically
been inop since poor maintenance in 1999. They had a data point in the computer
for low DG room ventilation flow, but nobody looked at it. No direct alarm on
the control room annunciators. It is poor plant design like the emergency
feedwater supply. Another big issue with the NRC.
So long term emergency feedwater supply to the steam generator (core cooling and the long term unreliable of the diesel generators...it is a bad mix.
What else are they hiding on us?
Emergency Diesel Generator Inoperable Due To Room Exhaust Fan Failure Waterford
3 declared Emergency Diesel Generator B (EDG-B) inoperable on May 22, 2013 due
to inability to maintain room temperature within design limits. Subsequent
trouble shooting revealed that the variable pitch room exhaust fan had failed
due to separation of the fan hub from the hub sleeve. Examination of recent operating
data showed that the first evidence of fan failure had been during a
surveillance test the previous month. An apparent cause evaluation determined
the probable cause of the failure to be the result of repairs made during a
previous (1999) fan motor replacement. These repairs caused additional stresses
on the fan hub components which eventually resulted in fan hub separation from
the hub sleeve. On
4/25/2013, hydramotor replacement retesting was completed by satisfactorily
operating EDG-B per OP-903-068. A later review of trends indicated the fan LO
FLOW computer point (PMC point D60417) was indicating abnormal (LO) for the
duration of this run; the LO FLOW condition had not occurred prior to this
4/25/2013 run.The LO FLOW PMC point does not alarm in the control room and was
not detected by Operations or Engineering at this time. This point is for long
term trending and is not necessarily monitored during each EDG run. Computer trends
indicated the fan motor current was approximately 64 amps and ambient
temperature was approximately 60 deg. F.
