05000414/LER-1999-001, :on 990115,relay Failure Occurred Which Resulted in Degradation of Auxiliary Feedwater Sys.Caused by Inadequate Single Failure Analysis.Maint Repaired Relay
| ML20209H809 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 07/08/1999 |
| From: | Glenn J DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML20209H780 | List:
|
| References | |
| LER-99-001, LER-99-1, NUDOCS 9907210073 | |
| Download: ML20209H809 (10) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(iii) |
| 4141999001R00 - NRC Website | |
text
e LPP10VED OND NO. 3150-0104 U
N POULATORY COMMISSI %
ESTIMATED BURDEN PER.ES ONSE PLY W11H THIS INPORM3 TION COLLECTION REQUEST: 50.0 HRS. FORWARD ION RDS MA (MNBB LICENSEE EVENT REPORT (LER)
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04 FFICE OF MANAGEMENT FACILITY NAME (1)
DOCMT NUseER G)
FAGE di Catawba Nuclear Station Unit 2 05000414 1 of 10 TITLE (4)
Unanalyzed Condition Associated with a Relay Failure in the Auxiliary Feedwater System due to an Inadequate' Single Failure Analysis EVENT DhTE (5)
LER NUMBER (6)
REPORT DETE (7)
OTHER R"#'ILITIES INVOLVED (8) auffM DAV YEAA VEAA 3B AL.
KEV GW bHTTH LAV YEAR FACILITY hAME Doc)(ET NUMBER (Si 1
1 15 1999 1999 001 01 7
8 1999 Catawba Unit 1 05000413 OFBkhTIIMB YNIS REPORT IS SUBMITTED PDASUANT TO THE REQUIREMENTS OF 10 CFR (Check one or more of the foJ10w2ng) (11)
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- 20. 22 03 (a' (3) (ii) 50.73(a)(2)(iii) 73.71
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- 20. 2203 (a) (2) (iii) 50.36(c)(1)
- 50. 73 (a ) (2) (v)
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- 50. 73 ( a ) (2 ) (vii)
- 286A, LICENSEE CONTACT FOR THIS LER (12)
NAMJ TELEPHONE NUMBER AREA CODE J.W. Glenn, Regulatory Compliance (803) 831-3051 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)
CDUSE SYSTEM COMPONENT AANUFACWMR REPORTMLE CA9SE SYSTEM COMPONENT MANUFACWRER REPORTABLE P2h BA Relay C-770 Yes W
tv SUPPLEMENTAL REPORT EXPECTED (14)
EXPECTED MONTH DAY YEAR IYES XINO SUBMISSION l
(f yes, complete EXPECTED SUBMISSION DATF)
DATE 115) l AROTRACT (1,ini t to 1400 spaces, i.e. approximately fif teen single-space typewritten lines) (16)
On January 15, 1999 at 0630 hours0.00729 days <br />0.175 hours <br />0.00104 weeks <br />2.39715e-4 months <br />, with Unit 2 operating in Mode 1, Power Operation, at 100% power, a relay failure occurred which resulted in degradation of the Auxiliary Feedwater System.
The Turbine Driven Auxiliary Feedwater Pump Train A controls were degraded and the 2A Train of Motor Driven Auxiliary Feedwater was inoperable. A similar event occurred on January 25, 1999 at 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> with Unit 2 operating in Mode 1, Power Operation, at 100% power. In the second event the same relay failed. The cause of both events was determined to be equipment failure (shorted relay coil). After the first event the relay coil was replaced and after the second event the entire relay was replaced. A failure analysis was performed to determine the root cause of the failures. The relay failures were determined to be an isolated event. Additional testing and analysis was determined not to be necessary.
Although there was no operation prohibited by technical specifications, this event is being reported as a voluntary LER due to its similarity to an unanalyzed condition which was reported in LER 413/97-009.
The unanalyzed condition is the inability to terminate Auxiliary Feedwater flow to a ruptured Steam Generator from the Control Room.
A compensatory measure which was developed and implemented for LER 413/97-009 is adequate for this event also.
The compensatory measure is to limit specific activity in the reactor coolant system to ensure that offsite doses are bounded by previous analyses. The root cause determined for LER 413/97-009 was a less than adequate single failure analysis.
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.m, Catawba Nuclear Station, Unit 2 05000414 1999 3 001 b
01 2 of 10
Background
Catawba Unit 2 is a four loop Westinghouse Pressurized Water Reactor.
The Auxiliary Feedwater System [EIIS:BA) is designed to provide a nuclear safety related source of emergency feedwater to the steam generators [EIIS:SG) to maintain secondary side level when the normal feedwater [EIIS:SJ) source is not available. The system consists of one turbine [EIIS:TRB] driven pump [EIIS:P) and two motor [EIIS:MO) driven pumps, several suction sources and associated piping.
Technical Specification 3.7.1.2 " Auxillary Feedwater System" requires three independent steam generator auxiliary feedwater pumps and associated flow paths to be operable with:
a. Two motor-driven auxiliary feedwater pumps, each capable of being powered from separate emergency busses, and b. One steam turbine driven auxiliary feedwater pump capable of being powered from an operable steam aupply system.
Action a. states that with one auxiliary feedwater pump inoperable restoration is required within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or the unit must be placed in Hot Standby within the next six hours and in Hot Shutdown within the following six hours.
Action b. states that with two auxiliary 'eedwater pumps inoperable the unit must be placed in at least Hot Standby wi sin six hcurs and in Hot Shutdown in the following six hours.
Unit 2 was operating in Mode 1, Power Operation, at 100% power immediately before each event began.
Other nuclear safety related equipment not available at the time of the first event was Train 2B of Safety Injection [EIIS:BQ] and Train B of Control Room Ventilation [EIIS:VI). These items were out of service for maintenance. No other nuclear safety related equipment was unavailable during the second event.
The Auxiliary Feedwater System has several suction sources which provide non safety grade condensate quality water. The assured (emergency) suction source is the Nuclear Service Water System [EIIS:BI] which is a raw water system. 'witchover to the emergency suction source occurs when low suction pressure is detected in the common suction header to t.he three auxiliary feedwater pumps.
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{l Catawba Nuclear Station, Unit 2 05000414 1999 s
001 4
01 3 of 10 LER 413/97-009-01 was submitted on 1/19/98. It addressed a more limiting Steam Generator (S/G) Tube Rupture (SGTR) accident scenario than previously analyzed in the Updated Final Safety Analysis Report.
In this scenario, the most limiting single failure is loss of one of the 125 Volt DC Vital Instrumentation and Control System [EIIS:EJ) Distribution Centers, EDE or EDF, resulting in the loss of control power to two S/G power operated relief valves [EIIS:RV) (which was previously identified as most limiting) as well as inability to remotely isolate auxiliary feedwater flow to two S/Gs.
Local manual action within a short time frame would be necessary to prevent S/G overfill. An administrative control on reactor coolant specific activity was implemented to ensure that offsite doses are bounded by previous analyses.
On 1-16-1999 Catawba Nuclear Station implemented the Improved Technical Specifications.
The Improved Technical Specification for the Auxiliary Feedwater System is 3.7.5.
It specifies a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> action statement for one inoperable Auxiliary Feedwater Pump and a six hour action statement for two inoperable Auxiliary Feedwater Pumps.
Event Description
First Event 1-15-1999 Catawba Nuclear Station Unit 2 was operating in Mode 1, Power 0630 Operation, at 100% power immediately before this even" began.
The Control Room received annunciator 2AD5,G/3, " Auxiliary Feedwater Pump Turbine Control Panel in Local Control".
Indications for valve 2SA2 " Steam Generator B Main Steam to l
Auxiliary Feedwater Pump Turbine Isolation Valve", 2SA5 " Steam Generator C Main Steam to Auxiliary Feedwater Pump Turbine IsolatioI. Valve" and 2SA145 " Trip and Throttle Valve" were losc. The A Train Auxiliary Feedwater Reset light went out.
Auxiliary Feedwater Tempering Isolation Valves 2CA185, 2CA186, 2CA187 and 2CA188 went closed. All A Train indications for the Auxiliary Feedwater System were lost (swapped from the Control Room to the Auxiliary Feedwater Pump Turbine Control Panel).
A Non-licensed Operator (NLO) was dispatched to the Auxiliary Feedwater Pump Control Panel to investigate.
1-15-99 The NLO at the Auxiliary Feedwater Pump Control Panel reported 0637 that the switches were in the " Control Room" position.
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PAGF (31 gg SEQUENTIAL e
REVISION YEAR NUMRFR NUMRFR r
N Catawba Nuclear Station, Unit 2 05000414 1999 c'
001 01 3 of 10 LER 413/97-009-01 was submitted on 1/19/98. It addressed a more limiting Steam Generator (S/G) Tube Rupture (SGTR) accident scenario than previously analyzed in the Updated Final Safety Analysis Report.
In this scenario, the most limiting single failure is loss of one of the 125 Volt DC Vital Instrumentation and Control System [EIIS:EJ) Distribution Centers, EDE or EDF, resulting in the loss of control power to two S/G power operated relief valves [EIIS:RV) (which was previously identified as most-limiting) as well as inability to remotely isolate auxiliary feedwater flow to two S/Gs.
Local manual action within a short time frame would be necessary to prevent S/G overfill. An administrative control on reactor coolant specific activity was implemented to ensure that offsite doses are' bounded by previous analyses.
On 1-16-1999 Catawba Nuclear Station implemented the Improved Technical Specifications.
The Improved Technical Specification for the Auxiliary Feedwater System is 3.7.5.
It specifies a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> action statement for one inoperable Auxiliary Feedwater Pump and a six hour action statement for two inoperable Auxiliary Feedwater Pumps.
Event Description
I First Event 1-15-1999 Catawba Nuclear Station Unit 2 was operating in Mode 1, Power 0630 Operation, at 100% power immediately before this event began.
The Control Room received annunciator 2AD5,G/3, " Auxiliary Feedwater Pump Turbine Control Panel in Local Control".
Indications for valve 2SA2 " Steam Generator B Main Steam to Auxiliary Feedwater Pump Turbine Isolation Valve", 2SAS " Steam Generator C Main Steam to Auxiliary Feedwater Pump Turbine Isolation Valve" and 2SA145 " Trip and Throttle Valve" were lost. The A Train Auxiliary Feedwater Reset lighc went out.
Auxiliary Feedwater Tempering Isolation Valves 2cA185, 2CA186, 2CA187 and 2CA188 went closed. All A Train indications for the Auxiliary Feedwater System were lost (swapped from the Control Room to the Auxiliary Feedwater Pump Turbine Control Panel).
A Non-licensed Operator (NLO) was dispatched to the Auxiliary Feedwater Pump Control Panel to investigate.
1-15-99 The NLO at the Auxiliary Feedwater Pump Control Panel reported 0637 that the switches were in the " Control Room" position.
No
.v
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YEAR SEQUENTIAL REVIPON NUMllFR NUMBFH 3f Catawba Nuclear Station. Unit 2 05000414 1999 001 01 4 of 10 personnel were working in the area.
Valves 2SA2 and 2SAS were found closed and the Auxiliary Feedwater Pump Turbine was not running. Operations declared the Unit 2 Auxiliary Feedwater Pump Turbine inoperable and entered Action a. of Technical Specification 3.7.1.2.
(Technical Specification Action Item Log (TSAIL) Entry C2-99-75).
Work Request 98061012 was written to investigate and repair.
1-15-1999 Maintenance found a blown fuse [EIIS:FU] in the Auxiliary 0820 Feedwater Pump control circuitry (in the Auxiliary Feedwater Pump Turbine Control Panel). It was determined that the circuitry which controls the Auxiliary Feedwat r System suction source swapover to the emergency source was affected for the 2A Motor Driven Auxiliary Feedwater Pump. Motor Driven Auxiliary Feedwater Train 2A was declared inoperable and action b. of Tech Spec 3.7.1.2 was entered (TSAIL Entry C2-99-77) allowing six hours to place the Unit in Hot Standby.
Since the original failure was known to have occurred at 0630 hours0.00729 days <br />0.175 hours <br />0.00104 weeks <br />2.39715e-4 months <br />, Operations started the six hour clock from 0630 hours0.00729 days <br />0.175 hours <br />0.00104 weeks <br />2.39715e-4 months <br />.
1-15-1999 Operations began reducing power per procedure AP/2/A/5500/09 0944 "Papid Downpower".
1-15-1999 Station Management determined that the six hour shutdown clock 1103 should have started from 0820 hours0.00949 days <br />0.228 hours <br />0.00136 weeks <br />3.1201e-4 months <br /> (the time when it was discovered that the 2A Motor Driven Auxiliary Feedwater Pump circuitry was affected). The new time to be in Hot Standby was 1420. Operations halted the power decrease temporarily at 38% power.
1-15-1999 Maintenance determined that the failed component was 1130 relay [EIIS:RLY]
"AG" in the Auxiliary Feedwater Pump Turbine Control Panel and isolated it from the rest of the circuit.
1-15-1999 Maintenance gathered parts for the repair of relay "AG",
1200 disassembled the relay in situ without determinating field wiring to the contacts, and began to replace the relay coil.
1-15-1999 Operations restarted the power reduction.
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,y NovRrR NouRrR f
Catawba Nuclear Station, Unit 2 05000414 1999 d
001 1
01 4 of 10 personnel were working in the area.
Valves 2SA2 and 2SAS were found closed and the Auxiliary Feedwater Pump Turbine was not running. Operations declared the Unit 2 Auxiliary Feedwater Pump Turbine inoperable and entered Action a. of Technical Specification 3.7.1.2.
(Technical Specification Action Item Log (TSAIL) Entry C2-99-75).
Work Request 98061012 was written to investigate and repair.
1-15-1999 Maintenan-e found a. blown fuse [EIIS:FU) in the Auxiliary 0820 Feedwater Pump control circuitry (in the Auxiliary Feedwater
)
Pump Turbine Control Panel). It was determined that the
{
circuitry which controls the Auxiliary Feedwater System j
suction source swapover to the emergency source was affected for the 2A Motor Driven Auxiliary Feedwater Pump. Motor Driven Auxiliary Feedwater Train 2A was declared inoperable and action b. of Tech Spec 3.7.1.2 was entered (TSAIL Entry C2-99-77) allowing six hours to place the Unit in Hot Standby.
Since the original failure was known to have occurred at 0630 hours0.00729 days <br />0.175 hours <br />0.00104 weeks <br />2.39715e-4 months <br />, Operations started the six hour clock from 0630 hours0.00729 days <br />0.175 hours <br />0.00104 weeks <br />2.39715e-4 months <br />.
1-15-1999 Operations began reducing power per procedure AP/2/A/5500/09 0944
" Rapid Downpower".
1-15-1999 Station Management determined that the six hour shutdown clock 1103 should have started from 0820 hours0.00949 days <br />0.228 hours <br />0.00136 weeks <br />3.1201e-4 months <br /> (the time when it was discovered that the 2A Motor Driven Auxiliary Feedwater Pump circuitry was affected). The new time to be in Hot Standby was 1420. Operations halted the power decrease temporarily at 38% power.
1-15-1999 Maintenance determined that the failed component was 1130 relay [EIIS:RLY]
"AG" in the Auxiliary Feedwater Pump Turbine Control Panel and isolated it from the rest of the circuit.
1-15-1999 Maintenance gathered parts for the repair of relay "AG",
1200 disassembled,the relay in situ without decerminating fi ald wiring to the contacts, and ben 2n o replace the relay coil.
1-15-1999 Operations restarted the power 1 + ction.
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- k Catawba Nuclear Station, Unit 2 05000414 1999 E
001 01 5 of 10 1-15-1999 operations stopped the power reduction at approximately 24%
1306 power when it became clear that the problem would be fixed before the Technical Specification action statement expired.
1-15-1999 Maintenance reinstalled a new coil on the "AG" relay, 1335 reassembled the relay in the cabinet without connecting the new coil, and re-energized the balance of the circuit.
Operations declared the Turbine Driven Auxiliary Feedwater Pump operable since the AG relay affects only the Reset Function for the Turbine Driven Auxiliary Feedwater Pump. Operations exited the six hour action statement and remained in the 72 hcur action statement.
1-15-1999 A plan was developed for reconnecting the relay coil wiring.
About 1500 Engineering determined retest requirements.
l 1-15-1999 Operations reentered Tech Spec 3.7.1.2 action b (six hour l
1735 action statement) so Maintenance could restore the relay coil wiring and perform the retest.
l 1-15-1999 The coil of relay "AG" was electrically connected into the 1900 circuit and a retest was successfully performed.
l 1-15-1999 Unit 2 Turbine Driven Auxiliary Feedwater Pump was declared l
1944 operable. (TSAIL Entry C2-99-75 was cleared).
l 1-15-1999 Unit 2 Motor Driven Auxiliary Feedwater Pump 2A was declared 1946 operable. (TSAIL Entry C2-99-77 was cleared).
Second Event 1-29-1999 Unit 2 Turbine Driven Auxi'.iary Feedwater Pump was declared 1415 inoperable for testing to verify operability of the pump since a governor adjustment was found out of its normal position.
(TSAIL Entry C2-99-213).
1-29-1999 During a second start (the first start was successful) of the 1500 Unit 2 Turbine Driven Auxiliary Feedwater Pump, the Control Room received the same indications as were received during the event of 1-15-1999.
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$q 2
Catawba Nuclear Station, Unit 2 05000414 1999 001 01 6 of 10 1-29-1999 Train 2A of Motor Driven Auxiliary Feedwater was declared 1634 inoperable. (TSAIL Entry C2-99-214). This placed Unit 2 in a six hour action statement.
1-29-1999 Maintenance isolated relay "AG" from the rest of the circuit 1820 and the Unit 2 Turbine Driven Auxiliary Feedwater Pump was declared operable (TSAIL Entry C2-99-213 was cleared). This placed Unit 2 in a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> action statement.
1-29-1999 A failure investigation team was formed.
The team reviewed through the failure of 1-15-1999, investigated possible causes of 1-30-1999 the failure and developed plans for restoring the 2A Train of Motor Driven Auxiliary Feedwater.
1-31-1999 Operations declared the Unit 2 Turbine Driven Auxiliary 0205 Feedwater Pump inoperable and reentered the six hour action l
statement for two inoperable Auxiliary Feedwater Pumps.
(TSAIL Entry C2-99-219). Maintenance replaced relay "AG".
l The entire relay was replaced. In the first event only the I
relay coil was replaced.
1-31-1999 Operations exited the six hour action statement after the 0227 relay was replaced. The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> action statement remained in effect.
1-31-1999 The breaker for the 2A Motor Driven Auxiliary Feedwater Pump 0243 in the 4KV Essential Power System Switchgear was racked to the test position to support testing of the AG relay replacement.
1-31-1999 Testing of the AG relay replacement per PT/2/A/4350/02E I
0255
" Relay AG in 2AFWPTCP Retest" began. 2AFWPTCP is the Unit 2 Auxiliary Feedwater Pump Turbine Control Panel.
1-31-1999 Operations declared the Unit 2 Turbine Driven Auxiliary 0333 Feedwater Pump inoperable in preparation for running the pump.
A manual start of the pump closes the Auxiliary Feedwater Flow Control valves which renders the pump inoperable. This placed Unit 2 in a six hour actien statement.
1-31-1999 Testing of the AG Relay replacement per PT/2/A/4350/02E was 0344 successfully completed.
t
l.
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Catawba Nuclear Station, Unit 2 05000414 1999 001 01 7 of 10 1-31-1999 Functional testing of the Unit 2 Turbine Driven Auxiliary 0356-0409 Feedwater Pump was successfully completed.
l 1-31-1999 The Unit 2 Turbine Driven Auxiliary Feedwater Pump was l
0417 restarted to gather data on the AG Relay.
1-31-1999 The 2A Motor Driven Auxiliary Feedwater Pump was started for 0431 breaker verification.
(
1-31-1999 The Unit 2 Turbine Driven Auxiliary Feedwater Pump was 0435 declared operable.
TSAIL Entry C2-99-220 was cleared. Unit 2 exited the six hour action statement and remained in the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> action statement.
1-31-1999 The 2A Motor Driven Auxiliary Feedwater Pump was secuted.
0436 l
l l
1-31-1999 Train 2A of Motor Driven Auxiliary Feedwater was declared 0954 operable. TSAIL Entry C2-99-214 was cleared.
Conclusion During these two events the Turbine Driven Auxiliary Feedwiter Pump was never inoperable.
The design of the Catawba Auxiliary Feedwater System I
ensures that the system is capable of providing feedwater to the Steam Generators in the event of a loss of normal feedwater. All four steam generators will receive flow despite the loss of any one pump. During thase events, the 2A Train of Motor Driven Auxiliary Feedwater was inoperable.
The Turbine Driven Auxiliary Feedwater Pump, however, was still fully capable of supplying feedwater to four steam generators via the B Train auto start circuitry and the B Train assured suction supply from the Nuclear Service Water System. Applying single failure logic, during the time the 2A Train of Motor Driven Auxiliary Feedwater was in the Technical Specification Action statement, no additional failures are assumed. Therefore the Turbine Driven Auxiliary Feedwater Pump was operable during these events.
During these events, the Control Room did not have control of valves 2CA50A and 2CA38A, which are the motor operated isolation valves to Steam Generators C and D respectively.
Additionally, the Turbine Driven Auxiliary Feedwater Pump could not have been fully reset from the Control Room, which would not allow the closure of the flow control valves nor the shutdown via
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Catawba Nuclear Station, Unit 2 05000414 1999 [
001 9
01 8 of 10 the "ON-OFF" switch of Turbine Driven Auxiliary Feedwater Pump.
The motor operated valves wou2d have had to be closed manually via operator action (procedurally driven) to stop the flow from Turbine Driven Auxiliary Feedwater Pump to these steam generators. This overfill vulnerability is bounded by the " Operable But Degraded" Evaluation associated with LER 413/97-009.
The cause of this event was the failure of normally energized relay "AG" in the Auxiliary Feedwater Pump Turbine Control Panel.
Relay AG is a Cutler Hammer Model D26MRD704A1.
The failure mechanism was shorting of the relay coil. After the first event, Engineering considered this to be an isolated failure since trending data indicated that of 4584 applications of this type relay at Catawba, there had been a total of three failures in 1995, two failures in 1996, one failure in 1997 and zero failures in 1998. Since these devices have proven so reliable, failure trending is performed on a yearly frequency. After the second failure the entire relay was removed and sent offsite for failure analysis.
Failure analysis determined a "most likely" root cause and a second "possible" root cause.
The most likely root cause was that the first failure was precipitated by a long term short circuit of the pickup and/or holding coils which caused excessive current consumption on the pickup phase of operation and resulted in damage to the pickup relay coil drop out switch.
The degradation of the drop out switch then directly caused the second failure. The second failure was a direct result of the switch degradation and failure to release.
The "possible" root cause is that the pickup drop out switch failed prematurely either due to a defect or misapplication.
The refuting evidence for this root cause is that the circuit operated as designed over the long term.
The conclusion of the failure analysis is that additional testing and analysis is not warranted since there is no hisucry of premature failure of the site population of these relays (as noted in the discussion of failure trending above).
In the past twenty four months there have been four reportable events caused by degraded subcomponents.
These were:
LER 414/97-006 Two reactor trips caused by optical isolator failure LER 413/97-010 Manual reactor trip caused by rod position indication system circuit card failure
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- d 01 9 of 10 Catawba Nuclear Station, Unit 2 05000414 1999 LER 413/98-01S Security Event LER 414/98-006 Reactor Trip due to a circuit card failure None of the previous events involved components similar to the one that failed in these events. Corrective actions taken for the previous events f
would not have prevented this event.
This event is not considered to be j
recurring.
]
This failure is EPIX reportable.
Corrective Actions
Immediate None Subsequent
- 1. Maintenance repai ad the relay per Work Order 98123327 for the first event and Work Or er 98128164 for the second event.
Planned 1.
Engineering will determine if any changes to the Auxiliary Feedwater System are required as a result of this event.
If changes are required a modification will be initiated.
- 2. Engineering will perform a failure analysis on the relay.
- 3. A revision to this LER will be submitted to document the results of the relay failure analysis.
Safety Analysis
During these events the 2A Train of Motor Driven Auxiliary Feedwater was inoperable. Although the controls for the Turbine Driven Auxiliary Feedwater Pump were degraded, the pump could have been started from the B Train controls and supplied water to the Steam Generators.
The ability to isolate flow to two of the four steam generators was degraded such that flow could
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}p Catawba Nuclear Station, Unit 2 05000414 1999 E 001 01 10 of 10 s
not have been terminated without manual action to close valves in the plant.
This affects the Steam Line Break, Feedwater Line Break and Steam Generator Tube Rupture accidents.
The Steam Line Break and Feedwater Line Break are not a concern since there is adequate time to mitigate these accidents through manual action.
This scenario is a concern for the Steam Generator Tube Rupture accident since flow needs to be terminated quickly to prevent Steam Generator overfill.
This problem has been previously recognized and reported in LER 413/97-009.
The scenario described in this LER is equivalent to the loss of distribution centers EDE and EDF of the 125 Volt DC Essential Power System as described in LER 413/97-009. An " Operable but Degraded" operability evaluation with a compensatory action is already in place for the scenario described in LER 413/97-009.
That Compensatory Action, which involves limiting specific activity in the Reactor Coolant System, is an adequate Compensatory Action for the scenario described in this LER.
The health and safety of the public were not affected by this event.
i