ML19225A202

LER 79-059/01T-0 on 790628:reactor Scrammed as Result of MSIV Closure.During Resulting Transient,Rcic & HPCI Isolated on Steam Line High Differential Pressure.Cause of RCIC Isolation Unknown.Hpci Switch Was Recalibr

ML19225A202
Person / Time
Site:	Hatch
Issue date:	07/06/1979
From:	Thomas Greene GEORGIA POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19225A194	List: ML19225A193 ML19225A202
References
LER-79-059-01T, LER-79-59-1T, NUDOCS 7907180551
Download: ML19225A202 (3)

Text

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,J11 LAt 1220 CDT, MSIV Fast Closure Starton test for Unit 2 wa_s initiated. Reactor [

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[scraved as a result of !'.SIV cl os u re.

During the resulting transient, RCIC and E'CI J

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7 ) I syste:"s were successfully started manually. At time of occurrence Unit 1 was in cold l o I shutdown condition for maintenance, hanger modifications, and refueling. (continued) l 83 ss COYP

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g l Closure startua test. Test shop ocrsonnel were instructed to check calibration of 1 TF1 [ switches 2E51 ','017 and M018 (PCIC) and 2E4J-ND0 '. and N005 (HPCI). Calibrations for l iTO 1 RCIC switches Pf 51 "Ol7 and N018 wore within acceatable rance. (continued) l 8 9 8J

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Evc- Dc,criptic, and Probable Co. sequences (continued)

There have not been any simultaneous system isolations previously on the sub-ject RCIC a.:d HPCI systems on either Unit 1 or U-it 2. There were no per-sonnel injuries, overexposures, or any release of radioactive materials to the environment as a result of this occurrence.

.

Cause Description and Corrective Actions (continued)

Cause of f<CIC isolation is not kncun at this . time and is under investigation by both utility and ::SSS supplier. Switch 2E41-:;035 setpoint was within acceptable range; however, switch '400'. was out of calibration. HPCI switch 2E41-l004 '.ms re-calibrated and returned to service. Opinion is diat switch calibration may not be sole cause of HPCI iso,latien and is also under in-vestigation. All switches involved are ITT Barton Model 253. Results of investigations and any followup testing will t;e reported in an updated LER.

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Narrative Report for LER 50-366/1979-59, Rev. 0

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9 On June 27,1979, at 1220 CDT, the MSIV Fast Closure startup test was init-iated for Hatch Unit 2. Initial reactor power das 975 (2365iMt). Reac-tor scram resulted due to MSIV clcsures. RCIC and IPCI systems isolated u.. steam line hirh differential pressure af Ler the reactor scram. Both systems were manually started by plant operatcrs. RCIC sys tem, af ter ran-ual start, ran throughout the duration of the M31V closure test. HPCI tras started at 1238 CDT to raise water level and was shut down at 1239 CDT by plant operator.

Immediate corrective actions initiated by plant operations personnel were to rianually start both RCIC and HPCI systems. Systems were successfully started manually. Redundant systems were available and capable of per-forming their intended functions. Test shop personnel were noti fied of the systers isolatien and were instructed to check calibration of steam line high differential pressure sJitches 2E51-N017 and N010 (RCIC)and 2E41-N004 and N005 (HPCI).

Test shop personnel found the calibration of the RCIC switchos to bc with-

-in an acceptable range per procedure requirements. Cause-pf the RCIC sys-tc., isclatien on high dP is unkncun at this time and is under invcstigaticn by both utility and the NSSS supplier.

Per the recocmendation of the NSSS supplier, instrurent piping for RCIC switches 2E51-N017 and N018 is being c.odified to correct piping gecaetry which could be a factor in the isolation of the systen The NRC resid;nt inspector was informed on 7-4-79, at 1010 CDT of the instrument piping mcd-ification.

HPCI high steam line differential pressure switches N004 and ND05 were checked for calibration. Switch 2Eal-N005 was found to be acceptable, hew-ever, switch N004 was out of calibration. Switch 2E41-N004 was recalibrat-ed and returned to service. Incorrect HPCI switch setpoint may not have been the sole cause of system isolation and will also be investigated.

Upon completion of investigation of HPCI and FCIC isolation problem by utility and NSSS supplier, sunplemntal corrective actions will be taken and reported in an update to this LER.

At the time of the occurrence, Unit 1 was in a cold shutdu.:n condii n for maintenance, hanger modi ficaf ions , and refueling. Results of the Unit 2 investigation and corrective actions will be considered for application to Unit 1 systems. Previous failures of HPCI and RCIC systems on Unit 1 ind 2 uill be re-evaluated.

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