ML19208B460

LER 79-059/01T-1:on 790628,after Reactor Scrammed as Result of MSIV Closure,Reactor Core Isolation Cooling & HPCI Both Isolated on Steam Line High Differential Pressure.Caused by Switch Out of Calibr.Switch Recalibr

ML19208B460
Person / Time
Site:	Hatch
Issue date:	09/14/1979
From:	Coggin C GEORGIA POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19208B458	List: ML19208B457 ML19208B460
References
LER-79-059-01T, LER-79-59-1T, NUDOCS 7909200343
Download: ML19208B460 (4)

Text

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lo l2 l lAt 1220 CDT,11SIV Fast Closure Startup test for linit 2 was initiated. Reactor scranmd1

, las a result of MSIV closure. During the resulting transient, RCIC and HPCI both iso- l o . l lated on steam line high differential pressure. Technical Specifications 3/4.7.3.b I lojsl [and 3/4.5.1 Action A were met for both RCIC and ilPCI respectively. The ADS system l lo K l lwas operable and capable of performing its intended function. Both the RCIC and HPCI l o y [ systems were successfully started manually. At time of occurrence Unit I was in cold j o a [ shutdown condition for maintenance, hanger modifications, and refueling. (con tiywed) l 7 16 9 "

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s o l RCIC and HPCI systens isolated en steam line high differential pressure. As systems I y l isolated, they were manually started and later secured upon comnletion of MSIV fast I h 1 [ closure startup test. Test shop personnel were instructed to check calibration of l I suitches 2E51-N017 and N018 (RCIC) and 2E41-H004 and UC05 (HPCI). Calibrations for l j[n 1 l RCIC switches were within acceptable range Icdever suitch 2E41-H004 was (continued) 1

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Georgia Power Company -

Plant E. I. ilatch Baxley, Georgia 31513 ,

Event Description and Probable Consequences (continued) .

There have not been any simultaneous systems isolations previously on the subject RCIC and HPCI systems on either Unit 1 or Unit 2. There were no personnel injuries, overexposures, or any release of radioactive materials to the environment as a result of this occurrence. This is a non-repetitive occurrence.

Cause Description and Corrective Actions (continued) found to be out of calibration. Switch was recalibrated and returned to ser-vice. At the. time of the isolations, cause vias not entirely determined and was under investigation by both utility ani !!SSS supplier. Cause has since been determined to be high steam line differential pressure. Review of prev-

'ious failures by system confirmed this as t;eing the chief cause of system

.inoperability. RCIC was modified by re-designing the instrument line piping and installing time delay relays. HPCI system codification included the ad-ditionof time delay relays ihich are being deleted at the request of flRC as addition did not affect system and could provide another node of failure if retaincd. Vendor ep.made various adjustments to the stop valve on HPCI turbine system prio- to returning Unit 2 to service. Testing program was conducted consistinj of hot and cold quickstarts at various pressure levels for each system anc' was monitored using IISSS supplied Startrec system. All testing was successful and problems with high steam line differential pres-

• sure resolved. Unit 1 RCIC and HPCI systems were reviewed for similar problems but. previous failure history did not indicate similar problems to that of Unit 2. Testing was scheduled, hwavor, to prove operability and conducted during return to service after maintenance / refueling outage. All additional testing on_ Unit 1 is complete and satisfactory.

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Narrative Report for LER 50-366/1979-059, Rev. 1 On June 27, 1979, at 1220 CDT, the MSIV Fast Closure startup test was initiated for Hatch Unit. 2.

Initial reactor nower was 97%

(2365 Mwt).

and HPCI Reactorisolated systens scram resulted due to MSIV closures. Recire on steam line high differential pressure after the reactor scram. Both systems were manually started by plant operators.

throughout the . duration of the RCIC system, after manual start, ran MSIV cl os u re test. HPCI was start.ed at 1238 CDT to raise water leve) 1239 CDT by plant operator. and was shut dovn at Inmediate corrective actions ini.tiated by . plant personnel were to manually start both RCIC and ooerations Systems were successfully started manually. HPCI systems.

were available and Redundant systems capable of per for min r; their functions. Test shop personnel intended were notified of the systens isolation and uere instructed to check calthration of steam line high differential pressure switches 2 Fi l - U 017 and N018 (RCIC) and 2E41-N004 and N005 (HPCl).

Test nhop personnel found the calibration of the RCIC switches to be within an acceptable range, however, HPCI switch 2B41-N004 was found out of calibration. Suitch was subsequently re-calibrated and returned to service. Initial cause of the stcau line high differential pressure was unknown at the time of the occurrence and required investigation by both utility and NSSS supplier.

An extensiveUSSE;'c.oncluded u ti.li ty . and revieu of the Unit 2 previous failure history by the

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• [p r.c s s u r e .wa s the clii b f cau se of previous system inoperability and was deenc'd the cause of the occurrence on Junc 27, 1979.

Corrective actions to the RCIC system included modification of the instrument piping for switches 2E51-NO17 and N018 to correct piping geometry which the NSSS supplier considered as a factor in the system isolation.

installation of time delav An additional relays. nodification included the HPCI modification included the addition of time delay relays which are now be in o; removed at the request of NRC as addition did not affect system performance and turbino could provide another mode of failure if retained. The HPCI vendor was contacted and service representative made various Unit 2 adjustments to service.

to valving on the system prior to returning Testing plans for both systens were formulated and shall be discussed in a subsequent paragraph.

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The Unit 2 testing program for RCIC and !!PCI consisted of hot and cold quick starts at various pressure levels for each system and was monitored using the NSSS supplier Startrec system used du r i rig startup testing. Testing for each system consisted as follows: one (1) hot quick start at 150, 500, and 800 psig; three (3) hot quick starts at 950, 975, and 1000 psig; one (1) cold quick start (CST-to-CST) at 1000 psig; one (1) cold quick start (vessel injection) at 975 psig; and threc (3) additonal cold quickstarts (CST-to-CST) within 30 days of the vessel injection. All testing una successful and problems .

with st. cam line high differential pressure resolved.

At the Line of the June 27 occurrence on Unit 2, Unit 1 was in a cold shutdown condition for maintenance, hanger modification, and refueling. Prior to returning the unit to service, previous failure history uas r e v i c u a rt for any similar problens. The Unit 1 previous failure history for RCIC and llPCI did not indicato similar problems to those of Unit 2.

Te s tin t; was, however, conducted to ;) c ov e systen opernbilit.y and scheduled during return to s.c r y i c e follouing uaintenanec/ refueling outage. The testing consisted of starts for each syst' at 15i0 psig per technical s p e c i f i c a t, t on requirenents and in addition, tuo (2) h o t- quick starts (CST-to-CST) and one (1) cold quick start ucre perforned. All testing for Unit 1 is conplete and satisfactory.

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