05000251/LER-1981-015, Forwards LER 81-015/03L-0.Detailed Event Analysis Encl

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Forwards LER 81-015/03L-0.Detailed Event Analysis Encl
ML19301A480
Person / Time
Site: Turkey Point NextEra Energy icon.png
Issue date: 12/28/1981
From: Williams J
FLORIDA POWER & LIGHT CO.
To: James O'Reilly
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19301A481 List:
References
NUDOCS 8201060519
Download: ML19301A480 (4)
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LER-1981-015, Forwards LER 81-015/03L-0.Detailed Event Analysis Encl
Event date:
Report date:
2511981015R00 - NRC Website
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Mr. James P. O'Reilly Regional Administrator, Region II U.S. Nuclear Regulatory Commission 101 Marietta Street, Suite 3100 Atlanta, Georgi a 30303 Dear Mr. O'Reilly; REPORfABLE OCC,URRENCE 294-81-15 TURKEY P0ild UNIT 4 DATE OF OCCUR:hNCE:

NOVEMBER 28, 1981 TECHNICM SPECIFICATION 6.9.2.b.1 R.CS PRESSUR.E TRANSIENT The attar.hed Licensee Event Report 's being submitted in accordance with Technical Specificat ico 4.9 to provide 30 day notification of the subject occurrence.

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~If h.,t Repertnle Occurrence 251-81-015

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Additional Event Description and Probable Consequences A.

Conditions Prior to Occurrence (ofdydEiEwith a temperature of approximately[ystem (RCS) was in a w The reactor was shutdown and the Reactor Coolant S 1((ind a pressure of approximate @ 10ysig ~ Pressure control was being maintained by charging into and letting down r'6thlhe RCS. The letdown path was via the Residual Heat Removal System (RHRS) and the Chemical Volume Control System (CVCS) letdown Pressure Control Valve (PCV-4-145). Reactor Coolant System filling and venting operations were completed and preparcti.;ns were underwcy te start RCS

'heatup.

B.

Descriptica of O currence

1. November 28,1981,10:55 p.m.

The 4B Reactor Coolant Pump (RCP) was started to begin RCS heatup. The Reactor Control Operator (RCO) r.oticed that RCS pressure was approximately PCV-4345las in the fu!!y i

500 psig and increasing. He also noticed thatg closed position and attempted to open i}gauto}bf lowering the setpoint, When this attempt failed, the valve was opened in manual, 4B RCP, 4 A charging pump and the pressurizer control heaters were also secured. One Power Operated Relief Valve (PORV-4-455C) was manually opened to reduce RCS pressure. The other PORY (PORV-4-456) was isolated on a clearance. An pHR~ isolation valve (MOV-4-750) was found in the closed positiori'and iiiiinediately 'r6Liu' ally 8p~e'nid'.'PCVl42145 was ret'Orned tdTut'6Aontrcl and

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4 A charging pump was restarted. The RCS pressure was maintained constant at approximately 335 psig.

overpressure condition was approximatelggi(u@psigpDuration of the The RCS peak pressure during the transient was/1100"

  • The problem was initia!!y diagnosed as misoperation of PCV-4-145. When PCV-4-145 was returneJ to auto control with a pressure setpoint of 6.5 and RCS pressure maintained constant,4B RCP operation was again attempted by the next shif t.

Subsequent investigation indicates that the RCS pressure transmitter PT-4-403 had closed MOV-4-750, due to the pressure interlock at 465 psig, thus resulting in the overpressure condition._lt_is common for the RCS pressure to surge during RCP startup ffdV 4-751 did not close, apparently due to PT-4-405 failing to reach the 46Y siQ interlock. It was later found 7. hat the instrument Efso'taatRvtwmr2:inssosssagstfWese.gynasteriMiesed;4 allowing a hycrostatic test by constructio'HKrsonnel.

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Re;>r-table Occurrence 251-81-015 Litu see Event Report Page three g.;.: -

2. November 29,1981,12:55 a.m.

The 4B RCP was restartede An overpressure condition reoccurred with peak pressure reachinff50$g? Again the RCP and the charging pump in operation were secured. PORV-Tt35C was manually opened to decrease RCS pressure.

Duration of the overpressure condition was approximatelygri,'e i]n'gi g Investigation of this condition found MOV-4-750 and MOV-4-751 closed, thus isolating letdown. It was found that RCS pressure transmitter PT-4-405 was,

reading higher than the others. It is believed thatPTr4 405 triu Thye76s~t itsf<s 8etpoint du'e'16 hydrostatic tnstinf'oi the sensing fineVitFthe b'l*6ciTVsTvP ~

' leaking through the7eai'.9fnce PT-4-405 was reading about 130 psig higher than the others, starting the RC' could have caused PT-4-405 to pren aturely close MOV-4-751 thus resulting in the overpressure condition.

During these two overpressure transients, thefiKffEIM57c3tdPAfter the first event, the block valve to PT-4-iO5 waW80)~ErTidf'fn ad' itTon, d

attempts were made to release the redundant OMS loop from clearance and restore it to operating conditions, but this was..et accomplished by the time the second overpressure event occurred.

Additional Cause Description and Corrective Actions The primary cause of the overpressure conditions is considered to be the automatic closure of the RHRS suction isolation valves coupled with the malfunction of the OMS while operating in a water solid condition. The reason the OMS did not operate as designed was found to be agaiTEdYtfrrim~a~fo'rpn the 40'5Tasis'61at'6dMThis electronic circuitry coupled with the fact that<PTJy$itry to aut53atida*lly open

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pressure transtnitter provides input to the OMSTirct

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PORV-4-455C on high pressure conditions. The two devices which malfunctioned hadfieviously,been tested and calibrated _.

g p p 4 _4o5-CD rp s u m mam-During both occurrences, the operators took action to stop the charging pumps which were providing the source of rapid pressurization. However, once the letdown flow was significantly reduced or terminated by closure of the RHRS isolation valves, timely operator action was precluded by the rapidity of the transient.

A fracture mechanics analysis based on the methods of Appendix G to Section Ill of the ASME Boiler and Pressure Vessel Code was performed by Westinghouse.

The analysis showed that the integrity of the reactor vessel was not impaired by these transients. It was further judged that the fatigue life of the vessel was not significantly affected. An independent Florida Power and Light Co. consultant reviewed the analysis and concurred with its conclusions. The fact that there was no thermal stress present was a beneficial factor in the analysis.

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Reportable Occurrence 251-81-015 Licensee Event Report Pageihr.

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The immediate corrective action consisted of reducing the RCS pressure to a value within the Technical Specification limits and obtaining an evaluation of the events from the Nuclear Steam System Supplier (Westinghouse).

As part of the long term corrective action, procedure changes will be rnade to include additional equipment checks as well as to insure proper valve line up following any tests prior to releasing the systems to operations. These actions will minimize the probability of component failures similar to the ones that resul+cd in the OMS operational anomalies.

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