ML20034F518
| ML20034F518 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 02/25/1993 |
| From: | Miller D PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| CCN-93-14025, NUDOCS 9303030346 | |
| Download: ML20034F518 (3) | |
Text
r CCN 93-14025 PHILADELPHIA ELECTRIC COMPANY PEACH BOTTOM ATOMIC POWER STATION
- p.
R.D.1, Box 208 1
Delta, Pennsylvania 17314
- %r t
rucu wrnou -int nvwi a (* i xcitirsci (717) 456-7014 D. B. Mdier, Jr.
Vce President February 25, 1993 Docket Nos.
50-277 50-278 U.S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555
SUBJECT:
156 Annual Report on Safety Relief Valve Challenges at Peach Bottom Atomic Power Station Gentlemen:
The following describes safety relief challenges for Peach Bottom Atomic Power 7tation (PBAPS) as required by the TMI Action
- Plan, Item II.K.3, and by the PBAPS Technical Specification, paragraph 6.9.1.c.
During 1992, there were three plant transients that resulted in 16 automatic actuations of the Main Steam Relief Valves in response to high reactor pressure.
There were no l
automatic actuations of the Main Steam Safety Valves.
The following are brief technical descriptions describing the three transients involving automatic actuation of the Main Steam Relief Valves:
LER 2-92-12:
l On 7/17/92, Unit 2 was in the RUN mode at 95% of rated thermal reactor power and Unit 3
was in the SHUTDOWN mode.
At approximately 1850 hours0.0214 days <br />0.514 hours <br />0.00306 weeks <br />7.03925e-4 months <br />, severe thunderstorms and lightning passed through the Peach Bottom area.
At 1858 hours0.0215 days <br />0.516 hours <br />0.00307 weeks <br />7.06969e-4 months <br />, the #3 startup feed was lost when its breaker (3435) tripped open.
Loss of the #3 startup feed resulted in Unit 3 Primary Containment Isolation System (PCIS) Group II 1II isolations during the 4 kV bus fast f
transfers.
At 1903 hours0.022 days <br />0.529 hours <br />0.00315 weeks <br />7.240915e-4 months <br />, a reactor scram occurred on Unit 2 when the Main Generator output breakers tripped open and caused a Main Generator power load unbalance trip signal.
This trip signal occurred during a
severe thunderstorm.
PCIS Group II/III isolations occurred as expected due to the reactor water level dropping below 0" as a result of void collapse upon insertion of 1
the control rods.
At this time, both Unit 2 Electro Hydraulic Control (EHC) pumps tripped and caused a loss of the EHC system.
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I 1992 NRC Annual Report Safety Relief Valve Challenges l
Page 2 of 3 l
Six Main Steam Relief Valves (MSRVs) lifted and the Alternate Pod l
Insertion (ARI) system actuated as reactor pressure increased (peak l
reactor pressure of approximately 1100 psig). Two MSRVs cycled two times, and four MSRVs cycled one time each.
The Reactor Core j
Isolation Cooling (RCIC) system was used to control reactor level and pressure.
Subsequently, reactor feed pumps were returned to l
service for level control.
The NRC was notified of the event via ENS on 7/17/92 at 2230 hours0.0258 days <br />0.619 hours <br />0.00369 weeks <br />8.48515e-4 months <br />.
The scram actuation and PCIS Group II/III isolations were reset.
LER 2-92-15:
On 8/17/92, Unit 2 was in the RUN mode at 97% of rated thermal reactor power.
At 0712 hours0.00824 days <br />0.198 hours <br />0.00118 weeks <br />2.70916e-4 months <br />, during the application of a i
Substation Load Dispatcher permit on a Circuit Breaker (CB-205), a reactor scram occurred following a Main Generator Lock Out.
CB-295 i
was being removed from service for maintenance activities.
The i
event occurred when the substation operator opened the "5014 Line Relay Block Switch" located on the Main Generator Output Breaker i
(CB-215) rather than "5014 Line Back Up Relay Block Switch" on CB-l 205.
The combination of the relay block switch open on CB-215 and l
the breaker open on CB-205 simulated a CB-215 breaker failure.
i With the CB-215 breaker failure signal and the breaker not open, a l
CB-215 failure signal was sent to the other Main Generator Output j
Breaker (CB-225) and to the Main Generator Lock Out circuitry which tripped CB-215.
i After the scram, PCIS Group II/III isolations occurred as 1
expected due to the reactor water level dropping below 0"
as a result of void collapse upon insertion of the control rods.
Three MSRVs momentarily lifted, and the ARI system actuated as reactor pressure increased (peak reactor pressure of approximately 1100 psig).
Three MSRVs cycled one time each.
The NRC was notified of i
the event via ENS at 0850 hours0.00984 days <br />0.236 hours <br />0.00141 weeks <br />3.23425e-4 months <br />.
The scram actuation and PCIS l
l Group II/III isolations were reset.
LER 3-92-08:
On 10/15/92 Unit 3 was in the RUN mode at 100% of rated thermal reactor power.
At 2112 hours0.0244 days <br />0.587 hours <br />0.00349 weeks <br />8.03616e-4 months <br />, an "A"
channel half PCIS Group I isolation occurred after the performance of a Surveillance Test, " Calibration Check of Turbine First Stage Pressure Switch PS-3-05-14C."
ST performance was immediately suspended until the i
t-l 1992 NRC Annual Report Safety Relief Valve Challenges Page 3 of 3 cause of the half isolation could be investigated.
While l
Operations personnel were scanning the PCIS relays to determine the cause of the "A" channel isolation, the "B" channel PCIS Group I i
actuated at 2116 hours0.0245 days <br />0.588 hours <br />0.0035 weeks <br />8.05138e-4 months <br />.
This resulted in a full PCIS Group I actuation which closed the Main Steam Isolations Valves (MSIVs).
l When the MSIV limit switches indicated that the valves were not full open, a reactor scram occurred.
PCIS Group II/III isolations occurred as expected due to reactor water level dropping below 0" as a result of void collapse upon insertion of the control rods.
The High Pressure Coolant Injection (HPCI) system, RCIC system, and the ARI system initiated when reactor water level dropped below the
-48" setpoint to -50". Three MSRVs lif ted on high reactor pressure (peak reactor pressure of approximately 1105 psig).
One MSRV cycled three times and two MSRVs cycled one time each.
The HPCI l
and RCIC systems were used in the Condensate Storage Tank (CST) to CST mode in conjunction with manual MSRV operation to control I
I reactor water level and pressure.
AT 2125 hours0.0246 days <br />0.59 hours <br />0.00351 weeks <br />8.085625e-4 months <br />, an Unusual Event was declared in accordance with the Emergency Plan due to the HPCI and RCIC injection to the reactor from a valid initiation signal.
The PCIS and the Reactor Protection System (RPS) scram logics were j
reset by 2150 hours0.0249 days <br />0.597 hours <br />0.00355 weeks <br />8.18075e-4 months <br /> and the affected systems were restored to the appropriate configuration.
The NRC was notified of the event via ENS at 2203 hours0.0255 days <br />0.612 hours <br />0.00364 weeks <br />8.382415e-4 months <br /> and the Unusual Event was terminated at 2300 l
hours.
If you have any questions regarding this matter, please call.
Sincerely,
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R.A.
Burricelli, Public Service Electric & Gas W.P. Dornsife, Commonwealth of Pennsylvania J.J. Lyash, USNRC Senior Resident Inspector R.I. McLean, State of Maryland T.T. Martin, Administrator, Region I, USNRC H.C.
Schwemm, Atlantic Electric C.D.
Schaefer, Delmarva Power INPO Records Center
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