ML18005A717

LER 88-032-00:on 881030,manual Reactor Trip Upon Loss of Main Feedwater Occurred.Caused by Trip of Heater Drain Pumps Attributed to Plywood Cover Left Inside Feedwater Heater 3A Following Maint.Plywood Cover removed.W/881129 Ltr

ML18005A717
Person / Time
Site:	Harris
Issue date:	11/29/1988
From:	Jerrica Johnson, Watson R CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
HO-880241-(O), LER-88-032, LER-88-32, NUDOCS 8812050217
Download: ML18005A717 (7)

Text

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I fA 'ZESSION NBR:8812050217 DOC ~ DATE: 88/11/29 NOTARIZED; NO DOCKET ¹ QACIL:50-~400 Shearon Harris Nuclear Power Plant, Unit 1', Carolina 05000400 AUTHeN~E ~ AUTHOR AFFILIATION JOHNSON,J.R.

WATSON,R.A. ,

Carolina Power Carolina Power l'ight l'ight Co.

Co.

RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 88-032-00:on 881030,manual rea'ctor trip upon loss of main feedwater due to trip of heater drain pumps.W/881129 W/8 ltr.

DISTRIBUTION CODE: IE22D COPIES RECEIVED:LTR I ENCL j SIZE:

TITLE: 50.73 Licensee Event Report (LER), Incident Rptg etc.

NOTES':Application for permit renewal fiied. 05000400 RECIPIENT COPIES RECIPIENT COPIES h ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL ~

PD2-1 LA 1 1 PD2-1 PD 1 .1 BUCKLEYgB 1 1 INTERNAL: ACRS MICHELSON 1 1 ACRS MOELLER 2 2 ACRS WYLIE 1 1 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 1 . 1 ARM/DCTS/DAB 1 1 DEDRO 1 1

. NRR/DEST/ADS 7E 1 0 NRR/DEST/CEB 8H 1 4 1 NRR/DEST/ESB 8D 1 1 NRR/DEST/ICSB 7 1 1 NRR/DEST/MEB 9H 1 1 NRR/DEST/MTB 9H 1 1 NRR/DEST/ZSB 8D 1 1 NRR/DEST/RSB.8E l. 1 NRR/DEST/SGB 8K) 1 NRR'/DLPQ/HFB 10 1 1 NRR/DLPQ/QAB 10 1.

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TOTAL NUMBER OF COPIES REQUIRED: LTTR 43 ENCL 42

NAC Form 388 U.S. NUCLEAR REQULATORY COMMISSION (983)

APPROVED OMB NO. 31504104 EXPIRES: 8/31/88 LICENSEE EVENT REPORT (LER)

FACILITYNAME'(ll DOCKET NUMBER (2) PA Shearon Harris Nuclear Power Plant Unit 1 0 5 0 0 0 4 00 1 OFO 5

"".'"Manual Reactor Trip Upon Loss of Main Feedwater Due to Trip of Heater Drain Pum s EVENT DATE (5) LER NUMBER (SI REPORT DATE 17I OTHER FACILITIES INVOLVED (8)

YEAR SEQVENTIAL Srrr REVISION MONTH OAY YEAR FACILITYNAMES DOCKET NUMBER(S)

MONTH OAY YEAR gg 'UMBER NVMSER 0 5 0 0 0 1 030 8 8 8 8 0 3 2 0 0 2 9 8 8 0 5 0 0 0 OPERATINO THIS REPORT IS SUBMITTED PURSUANT T0 THE REQUIREMENTs oF 10 cFR g: /csece one'or more of tire follovt/no/ (11)

MODE (8) 1 20.405(cl 50.73(s)(2)(lv) 73.71(III POWER 20AOS(s)( I IO) SOM(c) (I) 50.73(s) (2)(vl 73.71(c)

LEYEL 0 9 8 20,405(sl(1)(el SOM(c)(2) 80.73(el(2)(vel OTHER /Specify In Abrtrect Oe/ore em/ In Text, HRC Form 20.405(sl(1) (lll) 50.73(s) (2)(l) 50.73(s)(2)(vLB)(A) 388A/

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LICENSEE CONTACT FOR THIS LER (12)

NAME s TELEPHONE NUMBER Joseph R. Johnson v AREA CODE Senior Specialist Regulatory Compliance COMPLETE ONE LINE FOR EACH COMPONENT FAILURE OESCRIBEO IN THIS REPORT 113) 919362-2083 Tr F5@.: MANUFAC.

CAUSE SYSTEM COMPONENT MANUFAC. EPORTABLE CAUSE SYSTEM COMPONENT EPORTABLE )

TURER TO NPRDS +(I TURER TO NPRDS rA SUPPLEMENTAL REPORT EXPECTED (14) MONTH OAY YEAR EXPECTED SUBMISSION DATE (15I YES /lf yer, complete EIIPECZED SU84/ISSION DATE/ X NO

~ AB$TRAGT /Llmlt to /400 spec'et, I e., epproxlmetr/y fifteen r/no/ecpece typevrrltten liner/ (18)

ABSTRACT:

On October 30, 1988, the plant was operating in Mode 1 at 98/'ower. At 18:26:47 hours, the "B" Heater Drain Pump tripped causing an automatic turbine runback. Approximately 25 seconds 'later, the "A" Heater Drain Pump tripped.

Due to the rapid load reduction and sudden decrease in feedwater flow, the "B" Condensate Booster Pump tripped on high discharge pressure at 18:30:36. The control operator tripped the "B" Main Feedwater Pump at 18:31:00, and the "A" Main Feedwater Pump automatically tripped at 18:32:32, resulting in a loss of all feedwater flow. The control operator manually tripped the reactor at 18:32:44 and stabilized the plant in Mode 3.

The event was initiated by the trip of the Heater Drain Pump which was attributed to a plywood cover inadvertently left inside Feedwater Heater 3A following maintenance. In addition, the automatic turbine runback did not function as expected by the operators. This . hindered their ability to stabilize the plant and avoid a reactor trip. The turbine runbacks were investigated and the response was in accordance with the design. The operators were retrained with the information obtained from the investigation of the runback functions. The plywood cover was removed from the feedwater heater.

8812050217 881129 PDR ADDCN 05000400 8 PNU NRC Form 388 (84)3)

NRC Form 3SSA U.S. NUCLEAR RECULATORY COMMISSION

($ 83)

LICENSEE EVENT'REPORT {LER) TEXT CONTINUATION APPROVED OMS NO. 3'I50-010i EXPIRES: 8/31/88 FACILITY NAME (1 I DOCKET NUMSER (2) LER NUMSER (5) PACE (3)

Shearon Harris Nuclear Power Plant YEAR /gal SEOUENTIAL NUMSER REVISION jul NUMSSR Unit 1 0 5 0 0 0 0 0 2 OF 0 4 0 0 8 8 0 3 2 0 5 TEXT ///more s/roce*nqakwt, oee aA55ond /I/RC Forrrr 38SA Sl (1 3)

DESCRIPTION:

I The:plant was operating- normally in steady .state ..conditions:,at -'98X'hermal power and producing I8771 net MWE. All 'significant plant..control. systems were in automatic, and all,Digital Electro-Hydraulic (DEH) Control System (EIIS:TG) feedback loops were operational. The plant was in the process of returning to full power operation following refueling. The 90X thermal power level was reached about 1700 on October 29, 1988.. The .ascension to,-full power began about 1410 on October. 30. .As the power .-increase began, the "Low Delta P/Low Flow" alarm was periodically received for "B" .Heater"Drain Pump (EIIS'.SN:P).

r The "Low NPSH" alarm 'was actuat3.ng 'at regular intervals as power appr'oached 98X. By 1620, on October 30,,power was stabilized at. 98X. There was no readily apparent reason for the Heat;er Drain System( fluctuations. 'I This transient was the result of a serf.es of complex plant interactions. At 1826 the "Low Delta P/Low Flow"'larm actuated and "locked in." The "Low NPSH" alarm actuated, cleared, and actuated again. At 18:26:47 the "B" Heater

,Drain Pump (HDP) tripped. This started a turbine runback. The control operator expected the runback to stop at 86X turbine power. r Approximately 25 seconds'fter, the trip of the "B" HDP, the "A" HDP also tripped. The initial runback was still in progress due to overshoot caused by the turbine's (DEH) Control System'(EIIS:TG)P Reactor power at the time of the'A" . HDP trip was'pproximately 93X as indicated by the Nuclear .

Instrumentation System, and -approximately 70X turbine power. The turbine runback stopped when turbine power was approximately 54X at 18:27:32. As a result of the turbine load rejection, the Steam Dump Control System load rejection controller was armed and attempting to limit the increase in Reactor Coolant System average temperature caused by the mismatch'etween reactor power and turbine load. The Steam Dump valves to the condenser closed at 18:27:17 indicating that Reactor Coolant System average temperature was within 3 degrees of the reference value from turbine first stage pressure. Reactor power remained near 70X for approximately the next 3 minutes.

During the transient, the Condensate Booster Pumps speed controller shifted to manual control due to discharge pressure increasing above a preset pressure.

This was caused'y the decrease in feedwater flow and apparent overshoot by the Condensate Booster Pumps speed controller. The control operator's were controlling steam generator water level by manually controlling the feedwater regulating valves, and were controlling the Main Feedwater Pump (EIIS:SJ:P) suction pressure by manually adjusting Condensate Booster Pump speed.

However, the "B" Condensate Booster Pump (CBP) (EIIS:SG:P) tripped on high discharge pressure at 18:30:36. The operator expected the corresponding Main Feedwater Pump (MFP) to trip. When it did not, the operator. then manually tripped the "B" MFP at 18:31:00, because'he operators were trai.'ned that an automatic MFP trip should have resulted.

NRC FORM 34OA oU.S.GPO:1888 D82i.538/i55 (883)

NRC ForoI 388A U.S. NUCLEAR REOULATORY COMMISSION (9431 LICENSEE EVENT REPORT ILER) TEXT CONTINUATION APPROVEO OMS NO. 3150&ICE EXPIRES: 8/31/88 FACILITY NAME (1 I DOCKET NUMSER (ll LER NUMBER (Sl PACE (3) 1IAo EEOVENTIAL zlIN AEYIEION Shearon Harris Nuclear Power Plant YEAR >p% NVM EA >><: NVMSEA Unit 88 03 0 1

0 5 0 0 0 4 0 0 2 0 0 30F 0 5 m(T //F IIKoo OOoco /o Ioyo/CAE ooo aAWarW HRC Fom/355l3/ (IT(

DESCRIPTION (continued)

/

Based on reactor power, the operators were expecting another-turbine runback upon, the trip of the "B",MFP,'ut it did not;.occur. The runbackI did not occur

'ecause the runback is based on turbine load, and it was already low enough to prevent the runback. An operator, believing that the automatic runback failed to occur, began a manual turbine runback, and started both motor driven Auxiliary Feedwater Pumps (EIIS:BA:P). Steam Dump to 'the condenser was agpin actuated, and the manual runback caused a reactor power change from approximately'0X to 60X 18:32:18.

'he Steam ,Dumps actuated During this runback, the output of the "ALE CBP 'was controlled from 18:32:02 tb manually to maintain discharge pressure. The "A" MFP suction decreased to approximately 314 psig, and at 18:32!32, pressure'ubsequently automatically tripped resulting in a loss of all main feedwater flow.

Following these events, the reactor was manually tripped at 18.:32:44, and the plant was stabilized in Mode 3. Reactor power at the time of the trip was approximately 585.

CAUSE There were two causal factors for this event. The loss of the heater drain pumps initiated the event, and the unexpected response of the DEH Control System during the turbine runback contributed to'the event.

The'initial problems relating to the Heater Drain Pumps NPSH were attributed to an abnormal pressure drop across Feedwater Heater 3A, caused by a plywood cover that had been'inadvertently left inside the heater following maintenance activities during the previous refueling outage. The cover had been used to partially cover the feedwater inlet to the heater to allow workers a platform to stand on. Generally, individuals are allowed to follow good work practices on non-safety 'systems without detailed work procedures or inspection hold points. The failure to remove the plywood cover was a personnel error in failing to implement proper work practices. Procedure MMM-011, "Cleanliness and Housekeeping," recommends a written record of the entry and exit of personnel and tools. The use of the record, however, is elective based on the judgment of the job supervisor. The basic thrust of MMM-011 is to assure that the conduct of a specific job does not degrade the cleanliness of a system.

The cover partially blocked the feedwater flow through the 3A & 4A heaters, and in turn, increased the flow through the 3B & 4B heaters. The increased flow through 3B & 4B heaters caused increased condensed steam flow on the 4B heater shell si.de and decreased shell pressure. The "B" HDP takes suction from the 4B heater shell side. The heater level control system controls to a fixed level in the heater. The combined result was increased flow through the "B" HDP and decreased NPSH which caused the trip of the pump.

NAC FOAM 3OOA *U.S.OPO:(988&828 538/455 (983 I

NRC Form 3EEA U.S, NUCLEAR REGULATORY COMMISSION (84(3 I LICENSEE'EVENT REPORT (LER) TEXT CONTINUATION APPROVED OMB NO. 3I SOMI04 EXPIRES: 8/31/88 FACILITY NAME (1 I DOCKET NUMBER (2I LER NUMBER (8) PAGE (3I Shearon Harris Nuclear Power Plant YEAR SEOVENTIAL NVM ER REVISION NVMEER Unit 1 TEXT //F more epece CAUSE

/r /el/rkerL INe (continued)

~ HRC

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3RL/ l lTI o s o o o 40 088 0 3 2 00 04 OF 0 5 The:DEH Control System is designed such"that when the plant is operating above 90K <<thermal power, as sensed. by the turbine first,'.stage";impulse. pressure, loss of either HDP will result in a turbine runback until turbine power is reduced to less than 86X. When the runback occurs, the DEH Control System removes the feedback loops from service and ramps down the reference counter (desired=

load) at .1900 MW/min. until the runback signal.'has cleared, at wh'ich time it pill place the feedback loops back in service. The DEH Control System also

, ramps the turbine governor valves shut using'alculated vaI.ues'valve management program) at a rate that should match the reference counter.

However, experience has shown that, the governor valves will ramp shut at a slower rate than the reference counter. When the runback signal clears, and the feedback l,oops are placed back in service, the DEH Control System will continue closing the turbine governor valves until the reference counter and feedback signals match. This caused the DEH Control System to overshoot the turbine runback setpoints and create a 45X load rejection. \

The analysis of the event determined. that the DEH Control System functioned properly as designed. However, "the -control operators were not trained to expect this response during a turbine runback with feedback loops in service. In addition, th'e operators did not recognize the magnitude of the load rejection. These facts, coupled with- the rapid occurrence bf 'events, hirfdered the operators'bility to, stabilize the condensate and feedwater system pressures to prevent the trip of the "B" CBP and "B" MFP.

The operator expeCted the MFP to automatically trip after the trip of the "B" CBP, but it did not trip. However, the pump did function as designed.

Present plant design does not cause hn automatic MFP trip upon high CBP discharge pressure. The pump will trip upon low flow or low suction pressure as a result of the loss of the CBP, but these trips have time delays of 5 & 30 seconds respectively. Plant operators are trained to manually trip an MFP following a CBP trip, if it does not occur immediately.

The cause of the 'rip of the "B" CBP was attributed to high discharge pressure. Although the highest discharge pressure recorded by the plant computer was 607 psig, (the CBP trip setpoint is 625 psig), the pressure switches that actuate the pump trip could have seen a momentary spike not recorded by the pressure transmitter that feeds the computer. The trip was found to be within the tolerance of the applicable pressure switches'he cause of the trip of the "A" MFP was attributed to incorrect calibration of the pressure switch for the low suction pressure trip. A post trip review found the switch set at 305 psig instead of the required setpoint of 250 psig.

A NRC FORM 34EA 4 U.S.GPO:18804<< 024.838/4SS (843 l

NRC ForrmI 344A U mL NUCLEAR REOULATORY COMMISSION I94LTI LICENSEE EVENT REPORT ILER) TEXT CONTINUATION APPROVED OMB NO. 3160&194 I EXPIRES: 8/31/88 FACILI'TY NAME Ill DOCKET NUMBER ISI LER NUMBER (Sl PACE IS)

Shearon Harris Nuclear Power Plant YEAR Sl SEOVENTIAL Pm REVISION

.3 QI., NVMSER NVM ER Unit 1 o s o o o 40 088 0 3 2 0 0 0 5 QF 0 5 TEXT //amore epece ie /I1/reed See //I/Ooe///RC Forer 34843/ (ITI ANALYSIS OF EVENT:

There were no adverse safety .consequences- resulting. from this -event. All plant systems responded as intended, and.'he:.plant'as stabilized in Mode,3 at normal no load temperature and pressure. Normal steam generator water levels were restored with the Auxiliary Feedwater System (EIIS:BA).

This event is being reported in accordance with .10CFR50.73(a)(2)(iv) as an actuation of

~ '

an Engineer'ed Safeguards Feature and Reactor Protection System.

Previous similar events associated with the loss of Heater Drain Pumps and resulting in reactor trips were reported in LERs 87-019-00, 87-024-00, 87-025-00, and 87-031-00; however, these events are, not directly related to

'."his LER because of different root causes for the heater drain pump 'trip and the concurrent large turbine load decrease.

CORRECTIVE ACTION.

I

.1. Feedwater Heater 3A was opened and .inspected. m.,A .plywood,.cover'as found inside the heater pnd'as removed. The heater was restored to service, To prevent the overshoot of setpoints during a turbine runback, a design to the DEH Control System wi11 be considered, which'ill ensure change that the feedback loops, once taken out of service will not 'e automatically placed back in service.

3~ Plant operators will be provided training on the event and the effect of feedback loops on turbine runback conditions.

4. An operations night order was issued that requires the feedback loops to be taken out of service before exceeding 90% power. A change to applicable procedures will be made.

5. Disciplinary action was taken for the personnel responsible for leaving the cover in the 3A Feedwater Heater.

6. A review of the current controls and closure inspections of systems will be conducted.

7. Retraining of applicable maintenance personnel on proper work practices for system cleanliness will be conducted.

NRC SORM 344A *U.S.OPO;19884-834 d38/4dS 1983l

@&54 Carolina Power 8 Light Company.

HARRIS NUCLEAR PROJECT P.O. Box 165 New Hill, NC 27562 NOV 29 1988' File Number. SHF/10-13510C Letter Number: HO-880241 (0)

U.S. Nuclear Regulator/ Commission ATTN: NRC Document Control Desk Washington, DC 20555 SHEARON HARRIS NUCLEAR POWER PLANT UNIT 1 DOCKET NO. 50-400 LICENSE NO. NPF-63 LICENSEE EVENT'REPORT 88-032~00 Gentlemen:

In accordance with Title 10 to the Code of Federal Regulations,

'he enclosed Licensee Event Report is submitted This the requirement for a written 'report within thirty (30) report'ulfills days of a reportable occurrence and is'n accordance with th' format set forth in NUREG-1022, September 1983.

Very truly yours, R. A. Watson Vice President Harris Nuclear Project JRJ:dj Enclosure cc: Mr. W. H. Bradford (NRC SHNPP)

Mr. B. Buckley (NRR)

Mr. M. L. Ernst (NRC RII)

>r,.

MEM/LER-88-032/1/Osl