05000341/LER-1991-001, :on 910116,HPCI Inboard Steam Supply Valve E41-F002 Unexpectedly Closed During Surveillance.Caused by Malfunction of Transistor Q8 on Rosemount 510DU Trip Unit. Trip Unit Replaced
| ML20066H812 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 02/15/1991 |
| From: | Catola S, Pendergast J DETROIT EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| CON-NRC-91-0010, CON-NRC-91-10 LER-91-001, LER-91-1, NUDOCS 9102220001 | |
| Download: ML20066H812 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| 3411991001R00 - NRC Website | |
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February. 15, 1991 NRC-91-0010:
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Reference:
Fermi _2 NRC Docket No. 50-341 NRC License No.-NPF-43 s
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Subject:
. Licensee Event Report (LER) No.91-001'
'Please find enclosed LER.No.91-001, dated February 15, 1991, forJa reportable eventi that occurred on January -16,1991.
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'A (copy of;.this'LER is also being sent to the Regional-Administrator,;USNRC Region-III.
'If you have any' questions, please contact Joseph Pendergast,-
j Compliance Engineer,'at:(313) 586-1683.-
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on January 16,.1991, at 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br />, the High Pressure Coolant Injection (HPCI) inboard steam supply valve, E41-F002, unexpectedly closed during surveillance 44.020.219, "NSSSS HPCI Turbine Exhaust Diaphragm Pressure Division I Functional Test." 'The surveillance was
. stopped, a Limiting Condition for Operation (LCO) was entered with the l
HPCI systen and the associated ~ containment isolation valves were l
' declared inoperable.
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l The HPCI isolation resulted from a malfunction of transistor Q8-on a Rosemount.510DU trip unit.
The= trip unit supplies an-isolation signal L
to valve Ell 1-F002.
1 The failed Rosemount 510D0 trip unit was replaced with.a Rosemount 710DU trip unit,-as recommended in General Electric-Service Information Letter (SIL-) 520, " Transistor Degradation in Rosemount 510DU Trip Units." The recommendations of the SIL were being evaluated at the time of this event. The HPCI system was declared operable, and the LCO was removed at 2312 hours0.0268 days <br />0.642 hours <br />0.00382 weeks <br />8.79716e-4 months <br />, on January 16, 1991.
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Initial Plant Conditions
Operational Condition:
1(Power Operation)
Reactor Power: 80 Percent Reactor Temperature: 540 degrees Fahrenheit Reactor Pressure:
975 psig Description or the Event:
On January 16, 1991, at 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br />, the High Pressure Coolant Inject. ion (HPCI) (BJ) inboard steam supply valve (ISV), E41-F002, unexpectedly closed during surveillance 44.020.219, "NSSSS HPCI Turbine Exhaust Diaphragm Pressure Division I Functional Test." The surveillance was stopped, a Limiting Condition for Operation (LCO) was entered with the HPCI system and the associated containment isolation valves were declared inoperable.
The trip relay (RLY), E41K204C, was energized although the trin unit indicated normal. The trip unit, E41-N655C, had failed and was keeping relay E41K204C energized.
Isolation logic was unexpectedly completed for the HPCI steam supply valve, E41-F002, by energizing contact E41K204A during performance of the surveillance.
The isolation lo,11c requires both contacts E41K204C and E41K204A to be closed for isolation to occur.. The HPCI pump suction valve (ISV)',
E41-F042, had also received an isolation signal, however it was closed prior to the surveillance.
The failed Rosemount 510DU trip unit was replaced with a Rosemount 71000 trip unit. The HPCI system and isolation valves were declared operable, and the LCO was removed at 2312 hours0.0268 days <br />0.642 hours <br />0.00382 weeks <br />8.79716e-4 months <br />, on January 16, 1991.
Cause of the Event
The root cause of the HPCI isolation was a malfunction caused by resistive leakage across the Darlington Transistor 2N6296/08 for the Rosemount 510DU trip units. This failure was the same type of failure described in General Electric Service Information Letter (SIL) 520,
" Transistor Degradation in Rosemount 510 DU Trip Units."
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Analysis of the Event
In the event of a postulated accident scenario requiring the actuation of HPCI for water injection into the reactor vessel, the system would have been able to perform its' safety function. - Also an actual / valid.
high steam pressure signal would have caused an isolation.
In the case where the full isolation signal already existed at the time of the postulated accident, the operator would have been required to manually reset the isolation'(after removal of the test signal) and manually initiate HPCI.
In this case, the Reactor Core Isolaticn Cooling (BN) system would also have been available for use as a reactor water make-up system.-
The-logic' of the isolation valves requires both contacts, E41t'204A and E41K204C, to be closed for closure / isolation to occur. The c:osurs "
these valves is annunciated in the control room.
Therefore, operations personnel were aware of the valve closure / isolation when it occurred and initiated.the appropriate corrective actions.
Corrective Actions
The E41N655C Rosemount 510D0 trip unit was replaced with a 710DU trip unit as recommended in SIL 520. The recommendations of the SIL,-which was received in August 1990, were being evaluated under the Fermi corrective action (DER) program at the time of this event.
General Electric (GE) Nuclear Energy-Division recommended that GE BWR owners examine their plants' Rosemount Model 510DU Trip Units to determine the date code that appears on the Darlington Transistor.
If a date code lower than "8052" is found, GE recommended that either of the follr ng corrective actions be implemented:
L Replace the Rosemount 510DU trip unit with a Rosenount Model 710DU
~ tp Unit.
.eplace the suspect traasistor using replacement kit number J0710-0001 available from Rosemount.
1 2 will be evaluating the application of these trip units in vtrious systems during the second refueling outage. This activity requires field inspection of the trip units. Based upon our review cf these system applications, any further actions, such as transistor or trip unit replacement, will be considered as appropriate.
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Previous Similar Events
There have been no previous Licensee Event Reports (LER) concerning the malfunction of Darlington Transistors. There was one previous LER,'88-024, which described the isolation of the HPCI steam line during the performance of a surveillance.
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Failed Component Data:
o Rosemount Model 510DU trip unit o
Manufacture's Part/Model Number 510Du237020 o
Darlington Transistor:2N6296/Q8 r
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