ML20029D101
| ML20029D101 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 04/20/1994 |
| From: | Rehn D, Taylor Z DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| LER-93-003, LER-93-3, NUDOCS 9405040033 | |
| Download: ML20029D101 (15) | |
Text
_ __ _ _ _ . . _ _ _ _ _ _ _ _ .
il l I Duke lhaer Company (8n3) K11,3000
, Ca:awba Nadear Statwn Ov0 Concord Rd.
Wrk, S C 29745
, DUKEPOWER April 20,1994 Document Control Desk U. S. Nuclear Regulatory Commission j Washington, D.C. 20555 l
Subject:
Catawba Nuclear Station Docket No. 50-414 LER 414/93-003, Revision 1 Gentlemen:
Attached is Licensee Event Report 414/93-003, Revision 1 concerning REACTOR TRIP DUE TO INADVERTENT CLOS'URE OF MAIN STEAM ISOLATION VALVE. This revision is being submitted to correct the sequential number and revision number on page 1 of the original report.
This event was considered to be of no significance with respect to the health and safety of the public.
Very truly yours, Y
D. L. Rehn xc: Mr. S. D. Ebneter Marsh & McLennan Nuclear Regional Administrator, Region II 1166 Avenue of the Americas !
U. S. Nuclear Regulatory Commission New York, NY 10036-2774 !
101 Marietta Street, NW, Suite 2900 l Atlanta, GA 30323 Mr. R. E. Martin INPO Records Center U. S. Nuclear Regulatory Commission Suite 1500 Office of Nuclear Reactor Regulation 1100 Circle 75 Parkway Washington, D.C. 20555 Atlanta, GA 30339 Mr. R. J. Freudenberger NRC Resident Inspector atawba Nuclear Station 9405040033 940420 l y /- [ 'h s, ~.% m. PDR ADOCK 05000414 S PDR
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSloN APPROVED BY OMfNO. 3150-0104 p 92) EXPlRES 5/31/95 EST; MATED BURDEN PEA AESPONSE TO COMPLY WITH THis LICENSEE EVENT REPORT (LER) E'CES nEEEEno"'N%EO /S J%C1 E AND AECORDS MANAGEMENT BRANCH [MNBB 7714L U S NUCLEAA AEGULATORY COMMtSSION, WASHINGTON, DC 20555-0001, AND TC THE PAPERWOAK REDUCTION PROsECT 13150-0104h OFFICE OF (See reverse for required number of dig'ts/ characters for each block) MANAGEMENT AND BUDGET. WASH:NGTON, DC 20503 FACILITY NAME 0) DOCKET NUMBER (2) PAGE(3)
Catawba Nuclear Station, Unit 2 05000414 1 oPL4 TITLE 14)
Reactor Trip Due To Inadvertent Closure Of 1%in Steam Isolation Valve EVENT DATE (5) LER NUMBER (6 t REPORT-NUMBER (7) OTHER FACILITIES INVOLVED (8)
SEQUENT;AL REV'SaON F AClurY NAME DOC *U NuMats MONTH DAV YEAR VEAR " ^"
NUMBEA NUMBER N/A 05000 F AGluTY NAME DOCKET NUMBER
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09 25 93 93 003 01 04 20 94 05000 OPERATING THIS REPORT IS SUBdlTTED PURSUANT To THE REQUIREl0W:TS OF 10 CFR i: (Check one or morel (11)
MODE (9) 1 20 402(b) 20 405tc) X 50.73(a)(2)tiv) 73.71(b)
POWER 20 405(a)(1)(i) 50 36(ci; O 50 73(a)(2)(v) 73 71(c)
LEVEL (10) 100 20 405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii) OTHER 20 405(a)(1)(m) 50.73(a)(2)(i) 50.73(a)(2)(viii)(A) Aj';'{
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LICENSEE CONTACT FOR THIS LER (12)
NAME rELEPHONE NUM8ER pnclude A<es Cocel Z.L. Taylor. Comraliance bhnager (803)831-3812
- COMPLETE ONE LINE FOR EACH COMPONENT FA. LURE DESCRIBED IN THIS REPORT (13)
CAUSE SYSTEM COMPONENT MANUFACTUREA CAUSE SYSTE M COMPONENT MANUFACTUREA O PRD SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MWM CAf YEAR YES NO SUBMISSION
(" v" ""p+'e EXPECTED SU2Y'S3!ON DATEl X DATE (15)
ABSTRACT (Limit to 1400 spaces, i.e , approximately 15 single spaced typewritten lines) (16)
On September 25,1993 at 0937 hours0.0108 days <br />0.26 hours <br />0.00155 weeks <br />3.565285e-4 months <br />, Unit 2 was operating in Mode 1, Power Operation, at 100% power. Instrument and Electrical (IAE) personnel were preparing to perform a functional test on Liquid Waste (WL) Sump Pump control circuits, when they improperly opened link A-5 in cabinet 2ATC16. The proper link was A-5 in cabinet 2ATC14. When determining the actions to be taken, IAE did not notice that the diagram legend for link A-5 showed it to be in cabinet 2ATC14. Opening this link caused Main Steam Isolation Valve (MSIV) 2SM7 to close.
The closing of the MSIV resulted in a Main Turbine / Reactor trip. This event is attributed to less than adequate self checking and independent verification. Corrective actions include communication of the event to allIAE personnel and revision of the troubleshooting procedure.
Following the Turbine / Reactor trip at 1705 hours0.0197 days <br />0.474 hours <br />0.00282 weeks <br />6.487525e-4 months <br />, Unit 2 was in Mode 3, Hot Standby, when Lo-Lo T-ave (P-12) actuated. P-12 actuated again at 2251 hours0.0261 days <br />0.625 hours <br />0.00372 weeks <br />8.565055e-4 months <br />. In both events the Main Steam system was in an unusual alignment due to a valve problem. An additional steam load of warming the Main Feedwater Pump Turbines (CFPTs) for start with the unusual steam alignment caused T-ave to drop below 553 degrees F. The root cause of the P-12 events is the failure to adequately evaluate the impact of the unusual sterim alignment on future evolutions.
The corrective actions include communication of the events to all Operations personnel through an Operator Update and further communication of the details through operator proficiency training.
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01 93 ~ 003 Catawba Nuclear Station, Unit 2 dj pT}
T EXT pt more space os reqwrea use comttonet cop es or wc Form 36 BACKGROUND i Controlling Procedure for Troubleshooting andfCorrect ve IAE procedure IP/0/A/3890/01, Maintenance, establishes munication controls for related and non-safety related equipment. The i liprocedure verificationprovides that directions with the operational control group, independent verification i If afor specific so at ons,
[ k then this correct parts are used, and verification that equipmen procedure is not used to perform corrective action. '
Main Steam Isolation Valves [EIIS:V] (MSIV) provide steam isolation f
[EIIS:HX] (S/Gs) during shutdown and accident conditions.
The Power Operated Relief Valves (PORVs) provide a flow path for i 10% Main Steam
[EIIS:AB] (NC) heat removal when the MSIVs are clos
[EIIS:SB] (SM) flow capacity.
The Main Steam Vent to Atmosphere System [EIIS:VL] 0% steam relief (SV) S/G safe pressure protection for SM. There are five valves per steam line and capacity.
i The Auxiliary Steam System [EIIS:SA] (AS)f provides h posite unitsteam to vario all modes of operation. During startup it is preferred that AS be supplied rom t SM header. AS can be supplied from the same unit SM d or the auxiliar AS supplies the Main Turbine [EIIS:TRB] Sea power. id Enclosure 4.3, Feedwater Pump Startup, prov es d
Opaaims procedure OP/2/A/6250/01, directions for starting CFPTs. This procedure aligns various Main St System Pump Turbine System [EIIS:SA] (SP) valves and Feedwater Valve Pump
[EIIS:SJ)
Checklist.
(TE) valves prior to start per Enclosure 4.1 warm the turbine for start are opened and then placed in Auto.
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Catawba Nuclear Station, Unit 2 93 003 01 7m w n. an. ., ,.w.us. .mcn., ac Fm o n The condenser and atmospheric steam dump valves are controlled by one of three controllers
[EIIS:KC] (steam pressure, load rejection, plant trip). The selected controller actuates to conttol NC loop T-ave at or near a set reference signal.
P-12, Lo-Lo T-ave Interlock, is part of the Engineered Safety Features (ESP) Actuation System.
The purpose of the interlock is to block steam dump valve actuation to prevent excessive cooldown below the minimum temperature for criticality. The setpoint for P-12 is 553 degrees F on any two of four NC loops.
EVENT DESCRIPTION .
Turbine / Reactor Trio On September 25,1993, Unit 2 was operating in Mode 1, Power Operation, at 100% reactor power.
IAE technicians were troubleshooting the Liquid Waste System (EIIS:WD] (WL) Sump Pump 2A1 and 2A2 level control ~ circuits using procedure IP/0/A/3890/01 and the two appropriate electrical elementary diagrams (one for each pump). Using these diagrams the technicians determined that links A-5 and A-32 in cabinet 2ATC16 were to be opened. IAE technician A reviewed the diagrams to determine if their actions might affect other plant equipment. IAE j technician B verified that these actions were correct and would not affect other plant equipment. !
The IAE technicians did not notice that the diagram legend for link A-5 showed it to be in cabinet 2ATC14. IAE technician A listed the agreed upon steps in Enclosure 11.2 of the procedure. The technicians then used the steps in Enclosure 11.2 to identify, independently verify, and open link A-5 in cabinet 2ATC16.
At 0937:35 hours, IAE technician A opened link A-5 in cabinet 2ATC16. Opening this link closed S/G 2A MSIV 2SM7. !
l Level in S/G A began to decrease while level in S/Gs B, C and D began to increase. Steam flow increased from these S/Gs to meet total steam flow demand without S/G A. i 1
At 0937:41, Main Feedwater regulator valve 2CF-28 opened to increase level in S/G A. At the same time, S/G A safety reliefs 2SV-20 and 2SV-21 opened due to high S/G pressure (> 1175 psig and increasing).
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01 l ru, w .-. ,c.c. v.w.a ... .me- coo . .. mc r - x& o n At 0937:43, S/G A Power Operated Relief Valve (PORV) 2SV-19 opened due to pressure > )
1125 psig and increasing.
At 0937:48, S/G A safety relief 2SV-22 opened due to pressure > 1200 psig.
At 0937:59, Pressurizer [EIIS:VSL] (PRZ) heaters [EIIS:EHTR] groups A,B and D energized due to decreasing PRZ pressure of 2210 psig. l l
At 0938:00, condenser dump valves began opening due to increasing NC temperature.
At 0938:01, the Main Turbine tripped due to Hi-Hi S/G D level, P-14 interlock. The P-14. I interlock initiates a Main Turbine trip, initiates CF isolation and CF pump turbine trip when S/G l level reaches 77% in 1/4 S/Gs.
l At 0938:02, the Reactor tripped due to Main Turbine trip, P-9 interlock. The P-9 interlock I initiates a Reactor trip on a Main Turbine trip when Reactor power is greater than 69%. )
1 The Control Room Operators (CROs) immediately entered procedure AP/2/A/5500/02, Turbme Generator Trip and EP/2/A/5000/01, Reactor Trip or Safety Injection, to verify the plant responded properly and to assess plant conditions. The CROs then entered procedure EP/2/A/5000/01A, Reactor Trip Response, per EP/2/A/5000/01.
At 0938:05, The Main Feedwater System isolated due to the S/G D Hi-Hi level, P-14 interlock.
Auxiliary Feedwater [EIIS:BA] (CA) motor driven pumps auto started due to trip of the main feedwater pumps.
At 0938:23, The CA turbine driven pump started on 2 of 4 S/G Lo-Lo level. S/G A PORV 2SV-19 closed due to S/G pressure < 1092 psig and decreasing.
At 0938:29, condenser dump valves closed due to P-12 actuation.
At 0942:54, PRZ heaters A,B, and D deenergized due to pressurizer level < 17% and decreasing.
At 0943:04, Chemical and Volume Control System [EIIS:CB] (NV) letdown isolated due to pressurizer level < 17%. The CROs immediately entered procedure AP/2/A/5500/12, Loss of Charging or Letdown.
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Catawta Nuclear Station, Unit 2 93 ~ 003 01 rixt ,,, . .ou. . ,. ,..m. .. . .... ., c w% o ri At 0944:33, the CROs throttled CA flow to control cooldown and closed valves 2SA2 (S/G 2B SM to CAPT) and 2SAS (S/G 2C SM to CAPT) stopping the CA turbine driven pump. The lowest NC loop temperature reached was 540.8 degrees F.
At 0946:29, PZR heaters A,B and D energized due to PZR level > 17%.
At 0957:02, NV letdown was reestablished.
At approximately 1010 hours0.0117 days <br />0.281 hours <br />0.00167 weeks <br />3.84305e-4 months <br />, the plant was stabilized in Mode 3, Hot Standby.
At 1130 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.29965e-4 months <br />, the required notifications for the Reactor trip and ESF actuations were made per.
RP/0/B/5000/13, NRC Notification Requirements.
P-12 Actuation 1705 Hours On September 25,1993 at approximately 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> Unit 2 was in Mode 3, Hot Standby. The CROs were in the process of returning Unit 2 to operation using the Unit Fast Recovery (OP/2/A/6100/05) procedure.
Prior to this event there were two unusual steam loads aligned to Unit 2 SM.
- 1) Valve 2TL-8 (AUX STM TO STEAM SEAL REG) was not passing steam flow and therefore the CROs had SM maintaining turbine steam seal header pressure through 2TL-2 (MAIN STEAM TO STEAM SEAL REG).
- 2) Unit 2 was aligned to the AS header through 2AS-1 (SM TO AS INLET) to troubleshoot the cause of the Unit 1 AS header relief lifting.
At 1529 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.817845e-4 months <br />, steam dumps automatically closed and remained closed throughout this event.
Prior to this time the steam dumps were modulating slightly open to closed.
At approximately 1629, the Operator At The Controls (OATC) began aligning TE valves (steam drains of the CFPT stop valves) per procedure OP/2/A/6250/01, Condensate and Feedwater l System, Enclosure 4.17, Feed Pump Turbine Steam Valve Checklist, in preparation to start the CFPTs. This checklist, in part, has the operator open 6 TE valves and ensure 4 TE valves are closed.
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At 1633, steam pressure and NC loop T-ave began to trend downward. NC temperature was approximately 558 degrees F. The OATC was monitoring steam pressure and expected the downward trend after opening the TE valves. The OATC was aware of the additional steam loads (SM to steam seal header and Unit 2 supplying AS header) and felt the temperature decrease was not abnormal and could continue for a limited time while warming CFPTs.
Between 1633 and 1705, in addition to monitoring steam pressure, the OATC was maintaining S/G level using the CA pumps, supporting IAE during their test of CF regulator valves, and filling out the reactor trip report.
Prior to 1705, the CROs noticed a decrease in Volume Control Tank (VCT) level and noted that temperature had decreased further than expected.
At 1705:34, the CROs began closing TE valves. The CROs also closed valves 2AS-1 (SM TO AS INLET), 2AS-2 (MAIN STM TO AUX STM), and 2AS-12 (AS TO CFPT ISOL) to turn temperature around.
At 1707:55, P-12 actuated sending a close signal to the steam dumps. However the steam dumps were closed prior to this actuation.
At approximately 1712, T-ave reached a low of 552.3 degrees F.
At approximately 1718, T-ave had increased to 553 degrees F.
At 1850, the required notifications of the ESF actuation were made per RP/0/B/5000/13, NRC Notification Requirements.
P-12 Actuation 2251 Hours On September 25,1993 at 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br /> Unit 2 was in Mode 3 Hot Standby. Operations day shift turned control over to Operations night shift. The night shift CRos continued to return Unit 2 to operation using the Unit Fast Recovery (OP/2/A/6100/05) procedure.
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FACILITY NAME 0) DOCKET NUMBER (2) LER NUMBER (4) pAGg q3) g SEQUENTA. AEWS60N 05000 414 07 oF 14 Catawba Nuclear Station, Unit 2 93 - 003 01 rw v,n.n.e.a,.n,.aa..m.,,. ..,,,mei., m on At shift turnover the night shift CROs and SRO understood that:
- 2) P-12 had actuated while the TE valves were being aligned to start CFPTs. The operators thought the probable cause was that Unit 2 SM had been aligned to the AS header at that time.
- 3) The TE valves that were opened from the control room had been closed and that Unit I was now supplying the AS header. .
At 2207, steam dumps automatically closed and remained closed throughout this event. Prior to this time the dumps were modulating slightly open to closed.
At 2230, the operator opened the TE valves (steam drains of the CFPT stop valves) per procedure OP/2/A/6250/01, Condensate and Feedwater System, Enclosure 4.17, Feed Pump Turbine Steam Valve Checklist, in preparation to start the CFPTs. The operator knew about the P-12 actuation that had occurred on the previous shift and was monitoring temperature. The operator saw no decreasing trend in temperature.
At 2232, the operator opened valves 2SP-40, 29, 99 (CFPT A HP DRNS) and 2SP-37,19 (CFPT A LP DRNS) per procedure OP/2/A/6250/01, Condensate and Feedwater System, Enclosure 4.3, Feedwater Pump Startup. These valves are required to be opened for five minutes prior to turbine start and then placed in AUTO.
At 2234, the operator opened valves 2TE-3 (CFPT A LP S/V ABOVE SEAT DRN) and 2TE-7 (CFPT A HP S/V ABOVE SEAT DRN), per the procedure.
Prior to 2237, the operator noticed an unacceptable downward trend in NC temperature from approximately 558 degrees F.
At 2237, the' operator closed the SP valves per the procedure and saw temperature begin an upward trend from a low of approximately 554 degrees F.
At 2243, the operators determined NC temperature (approximately 555 degrees F and increasing) to be acceptable and continued with feedwater pump startup procedure by resetting both CFPTs.
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THE PAPEAWOAK REDUCTION PAOJECT (3:504104. OFFICE OF M ANAGEMENT AND BUDGET. WASHtN3 TON. DC 20503 FACILITY NAME (1) DOCKET NUMBER 12) LER NUMBER (Sp PAGE(4 LEQ ENT.A., REMON YDR NUMBER NUMBEA 05000 414 08 OF 14 Catawba Nuclear Station, Unit 2 93 003 01 Tut or mv w c, e w a . moon coo.., or wc rw.,, m, o n Resetting the CFPTs opens the high and low pressure CFPT stop valves. NC temperature began to trend downward.
At 2250, the operator began closing the TE valves on both CFPTs in response to the downward trend in temperature.
At 2251, P-12 actuated sending a close signal to the steam dumps, however the steam dumps were closed prior to this actuation. T-ave reached a low of 553 degrees F.
On September 26,1993 at 0032 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br />, the required notifications of the ESF actuation were made per RP/0/B/5000/13, NRC Notification Requirements. .
CONCLUSION Turbine / Reactor Trio The Turbine / Reactor trip was the result of MSIV 2SM-7 closing while Unit 2 was at 100%
power. IAE technicians inadvertently closed 2SM-7 while troubleshooting the WL Sump Pumps 2A1 and 2A2 level control circuits. The technicians were using IP/0/A/3890/01 and the two appropriate electrical elementary diagrams (one for each pump). Using these diagrams the technicians determined that links A-5 and A-32 in cabinet 2ATC16 were to be opened. IAE technician A reviewed the diagrams to determine if their actions might affect other plant equipment. IAE technician B verified that these actions were correct and would not affect other plant equipment. The IAE technicians did not notice that the diagram legend for link A-5 showed it to be in cabinet 2ATC14. IAE technician A listed the agreed upon steps in Enclosure 11.2 of the procedure. The technicians then used the steps in Enclosure 11.2 to identify, independently verify, and open link A-5 in cabinet 2ATC16. Opening link A-5 in 2ATC16 closed 2SM-7.
The contributing factors which may have led the technicians to misidentify link A-5 to be in cabinet 2ATC16 are:
- 1) The technicians had begun troubleshooting the WL sump pump circuits in cabinet 2ATC16 the previous day.
- 2) The majority of the components and circuits for these pumps were located in 2ATC16.
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TEXT CONTINUATION CH V BB nt4 QSygS MAcoyAGEM s gor w,, S jC E THE PAPEAWOAK AEDUCtON PACLECT (31So4iodh OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON. DC 20503 F ACluTY NAME (t) DOCKET NUMBER (2) LER NUMBER (4) PAGE13) ygg SEQvENT6A. AEvis C4 NUMBE9 NUMBEA l 05000 414 09 oF 14 Catawba Nuclear Station, Unit 2 93 003 01 rw on,,w. sc.c v.w.a a. .m. m.., e unc ram sem o n These two factors tended to put the technicians in the mind set that all of their work would be l in this cabinet.
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- 3) Beneath both links on the diagrams, *2 was listed as the legend reference for the links' l location. On the diagram for pump 2A2, *2 referred to 2ATC16 in the legend. On the diagram for pump 2A1, *2 referred to 2ATC14 in the legend. This difference was not l
noticed by the technicians.
- 4) When viewing the diagrams, the technicians laid one diagram on top of the other diagram. This caused the technicians to view both diagrams as one. This may have contributed to the technicians not noticing the difference in the two legends. ,
The root cause of this incident is inadequate self checking and independent verification of the intended actions. To help prevent similar mistakes, IAE communicated the details of this event to IAE personnel through electronic mail and through discussions with their supervisors. In addition, the troubleshooting procedure will be revised to have an additional sign-off for self checking and independent verification of the written action steps. Also the procedure steps will be enhanced to more clearly identify the actions to be taken. Because of the amount and simlarity of id:ntifiers on electrical diagrams, there is the potential for problems to occur when using these diagrams. IAE distributed a bulletin to IAE personnel that listed some good practices for when electrical diagrams are used.
IAE will evaluate similar type procedures to determine if changes are warranted.
During the Reactor trip systems responded as expected. One significant anomaly was the loss of the C-9 permissive signal. The C-9 signal allows steam to be dumped to the condensers. The initial investigation indicates that C-9 was lost because a steam supply was not aligned to the l steam seal header while at power. A steam supply has been aligned to the steam seal header l with the unit at power until this issue is resolved. Operations has initiated the Problem i Investigation Process (PIP) by writing PIP 2-C93-0336. Operations also informed all operators about this problem through an Operator Update.
A review of operating experience data for the 24 months prior to this event identified five events involving a reactor trip. None of these five events are similar to this event, in that they do not involve the same equipment, administrative controls or personnel actions. Therefore this is not l a recurring event.
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NRC FORM 366A U.S. NUCLEAR REGULATORY CoMMISSloN APPROVED BY oMB NO. 3150-0104 (5 921 EXPIRES 5/31/95 EST1 MATED BURDEN PER RESPONSE To COMPLY W'N THIS LICENSEE EVENT REPORT (LER) 2
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P-12 Actuations The P-12 actuations were an actuation of the interlock circuit and did not cause the steam dumps to close. The steam dumps were closed prior to the actuation. The P-12 actuations were reported because they were an unexpected actuation of an engineered safety feature.
In both P-12 actuations the operators had not realized how great of an effect the startup of the CFPTs would have on NC temperature with the additional demands on the steam system and without automatic temperature control (steam dumps closed). In both events the CROs knew of the additional steam load demands and were aware that the steam dumps had been modulating, but did not realize the potential of additional steam loads to significantly reduce NC -
temperature. In neither event did the CROs discuss how the 90sition of the steam dumps relative to T-ave and the unusual alignment of SM to the AS header might affect future evolutions. The CROs are expected to evaluate these types of operating conditions. The root cause of this event is the failure to adequately evaluate the impact of unusual operating conditions on future evolutions. A subsequent corrective action was to communicate this event to the Operations shifts through an Operator Update. The planned corrective action is to communicate the details of this event to licensed operators through operator proficiency training.
This training will emphasize the need to discuss and evaluate the impact of unusual alignments on future evolutions.
The reason SM was unusually aligned to the steam seals was because valve 2TI-8 was not working properly. This additional steam load on SM caused the steam dumps to be closed further than normal. Problems with 2TL-8 had been identified in 1992 and a deficiency tag had been hung on the valve. However, the work request written to repair the valve could not be found. Operations has written PIP 2-C93-0839 to investigate why 2TL-8 was not repaired.
Work Request 93033950 has been written to repair this valve.
Contributing to the P-12 actuation at 1705 was the fact that the OATC had opened 4 TE valves ;
on the checklist that were required to be closed. The OATC was aware that he had opened these i valves and expected and saw a decrease in steam pressure. At this time the operator felt that the decrease in steam pressure was normal and could be continued for a limited time while ,
warming the CFPTs. Opening these 4 valves was not the root cause of the P-12 actuation, but l caused the P-12 to occur earlier in the startup of the CFPTs. The procedure checklist was !
reviewed and it states that these valves should be in the closed position. The OATC did not !
adequately self check his actions. As a subsequent corrective action, Operations management discussed the need to perform adequate self checking with the individual. The Human 1
1 NAC FCEIM 366A 45-92) 1
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'NRC FORM 366A ' U.S. NUCLEAR REGULATORY COMMISSloN APPROVED BY oMB NO. 3150-0104 I is n I EXPlRES 5/31/95 ESDMA4D BURDEN DER RESPONSE TO COMPLY W!TH THiS LICENSEE EVENT REPORT (LER) $$ "ECEaWlo"s"RDE8$E ATho Z' ,dfu"ES l TEXT CONTINUATION QSg A sgANAps e uu E
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,.o.. .-~ co... ., Nac F,,, % o n Performance Enhancement Systems (HPES) Team is investigating this event and will make I recommendations based on their findings.
Operations monitors the highest T-ave when at power and during no load conditions. When at power the highest T-ave is the most limiting. However, when at no load Operations should be cognizant of both highest and lowest T-ave. The best estimate of the difference between highest and lowest T-ave during these events is 1 - 1.5 degrees F. It is not certain if this fact contributed to these events. Operations will discuss methods of monitoring T-ave during no load conditions as part of the planned operator proficiency training.
A review of operating experience data for the 24 months prior to this event identified two LERs '
reporting engineered safety feature actuations involving the Lo-Lo T-ave interlock (P-12). In both cases the P-12 actuations were caused by the inadvertent opening of the steam dumps. The root cause was linked to the process control cards for the steam dumps. Since the root cause for this event is different than these past events, this event is not considered recurring.
CORRECTIVE ACTIONS Turbine / Reactor Trip IMMEDIATE
- 1) CROs entered procedure AP/2/A/5500/02, Turbine Generator Trip and EP/2/A/5000/01, Reactor Trip or Safety Injection, to verify the plant responded properly and to assess plant conditions.
- 2) CROs entered procedure EP/2/A/5000/01A, Reactor Trip Response, per EP/2/A/5000/01.
- 3) CROs entered procedure AP/2/A/5500/12, Loss of Charging or letdown, upon NV letdown isolation.
- 4) CROs throttled CA flow to control cooldown and stopped the CA turbine driven pump.
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NRC FORM 366A (S-02)
INRc FORM 366A U.S. NUCLEAR REGULATORY COMMISSloN APPROVED BY oMB No. 3150-0104
- '2 EXPIRES 5/31/95 EstrMATED BURDEN PEA AESPONSE TO COMPL.Y W'TH TMIS
, LICENSEE EVENT REPORT (LER) '
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SEQvE TiA. HEv@QN YEAR 05000 414 12 oF 14 Catawba Nuclear Station, Unit 2 93 - 003 -
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SUBSEQUENT
- 1) IAE notified the control room that they had inadvertantly closed valve 2SM7.
- 2) Operations investigated the loss of the C-9 permissive signal and initiated PIP 2-C93-0836 to further investigate this problem.
- 3) Operations personnel were informed of this event through an Operator Update.
- 4) Details of this event were communicated to IAE personnel through electronic mail and through discussions with their supervisors.
- 5) IAE distributed bulletin to IAE personnel that listed some good practices for when electrical diagrams are used.
PLANNED
- 1) IAE will revise IP/0/A/3890/01, Controlling Procedure for Troubleshooting and Corrective Maintenance, to include a separate sign-off for self checking and independent verification to verify the written action steps agree with the drawings. Also the procedure steps will be enhanced to more clearly identify the actions to be taken.
- 2) IAE will evaluate similar type procedures to determine if changes are warranted.
P-12 Actuations !
IMMEDIATE
- 1) CROs responded to the cooldown by isolating steam loads on SM. !
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SUBSEQUENT i
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- 1) Information concerning ti.e P-12 actuations was communicated to Operations personnel l through an Operator Update.
- 2) Operations managemen. discussed the need to perform self checking with the operator j who failed to self chec'x when completing the Feed Pump Turbine Steam Valve Checklist.
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NAC FOAM 366A (5 92)
,NAC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION ~~ APPROVED BY oMB NO. 3150-0104 EXPIRES 5/31/95 l EStMATED BURDEN PER RESPONSE TO COMPLY WITH TH'S LICENSEE EVENT REPORT (LER) # R s AN N "'
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- 3) Operations investigated problems with valve 2TL-8 and initiated PIP 2-C93-0839 to I further investigate this problem. l
- 4) Work Request 93033950 was written to repair valve 2TL-8.
1 PLANNED
- 1) Operations will communicate the details of these events to licensed operators through operator proficiency training. This training will emphasize the need to discuss 'and I evaluate the impact of unusual alignments on future evolutions. Also, methods of ,
monitoring T-ave during no load conditions will be discussed. . l l
- 2) HPES will complete their investigation of the P-12 event. i SAFETY ANALYSIS Turbine / Reactor Trio This event was initiated on the inadvertent closure of a main steam isolation valve 2SM7 which resulted in a main turbine / reactor trip. These events are bounded by the Safety Analyses documented in the FSAR Sections 15.2.4, Inadvertent Closure of Main Steam Isolation Valves, and 15.2.3, Turbine Trip.
l Upon closure of 2SM7 the S/G A safety relief valves and power operated relief valves opened to control pressure. The level in S/G A began to decrease and the level in S/Gs B, C, and D began to increase. Subsequently the level in S/G D reached the Hi-Hi level setpoint of 77% and l the P-14 interlock actuated to trip the main turbine, isolate main feedwater and trip the main ;
i feedwater pump turbine. The condenser dump valves opened to control NC temperature. Upon the main turbine trip with reactor power greater than 69% the P-9 interlock actuated and tripped the reactor. All rods inserted as expected to control reactivity. The Auxiliary Feedwater motor driven pumps and turbine driven pump auto started to remove residual heat from the core.
Subsequently, NC loop T-ave reached 553 degrees F and the P-12 interlock actuated closing the steam dumps to prevent excessive cooldown. The operators properly responded by threttling auxiliary feedwater flow to control cooldown. The cooldown of the NC system experienced ,
during this event is bounded by the Safety Analysis documented in the FSAR Section 15.1.5, 1 Steam System Piping Failure.
NRC FORM 366A (5-92)
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. NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 l 15 82)
EXPIRES 5/31/95
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LICENSEE EVENT REPORT (LER) f "
5*JSkG$'N?Cn0 ensuA!!?O usu Ts ANO REC R S MANAGEMENT BMNCH (MNB9 nut U S. NUCLEAR TEXT CONTINUATION REGULATORY COMM SSION. WASM:NGTON.DC 20555-0001. AND TO THE PAPEDWORK REDUCTION PRCUECT (315041043 OFFICE OF MANAGEMENT AND BUOGET WASHINGTON, DC 20$03 l F ACILITY NAME 0) DOCRET NUMBER Q) LER NUMBER (S) PAGE0) q SEQUE NT . A. RE'v)S>ON NUMBER NUMBER 05000 414 14 oF J4 Catawba Nuclear Station, Unit 2 - -
01 93 003 rExT vi n. so.c. ., r.w.a a. .u.w,. coo, , or nRc Fn xa, o n After a review of this event all systems responded as designed to shutdown the reactor and maintain it in a safe shutdown condition. There were no unusual releases of radioactive material.
The health and safety of the public were not affected by this event.
P-12 Actuations The P-12 actuations were an actuation of the interlock circuit and did not cause the steam dumps to close. The steam dumps were closed prior to the actuation. The operators had noticed the decreasing trend in NC temperature and had taken action to prevent any further cooldown before.
the actuations occurred. The P-12 interlock did function properly in each case when NC loop T-ave reached 553 degrees F. This cooldown of the NC system is bounded by the Safety Analysis documented in the FSAR Section 15.1.5, Steam System Piping Failure.
The health and safety of the public were not affected by this event.
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J l NAC FCRM 368A (5-92) .
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