ML20085G406
| ML20085G406 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 12/13/1974 |
| From: | Eric Thomas TENNESSEE VALLEY AUTHORITY |
| To: | Case E US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20085G410 | List: |
| References | |
| NUDOCS 8308290077 | |
| Download: ML20085G406 (3) | |
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ABNORMAL OCCURRENCE REPORT 3.*
Report Iio.:' BFAO-50-260/7431W Report Date: Dece=ber 13, 1974 Occurrence Date: Dece=ber 3, 1974 Facility: Browns Ferry Nuclear Plant unit 2 i
Identification of Occurrence l
HPCI auto-isolation.
1 Conditions Prior to Occurrence l
l A relief valve, =anually actuated following unit trip from 745 We, was experiencing excessive blowdown and reactor pressure was decreasirg. High level indications were present on the HFCI gland seal condenser and turbine exhaust drain pot while repairs were in progress on the HPCI gland seal 4
condensate pu=p =otor.
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Descriution of Occurrence N
Approxirntely 30 minutes after the unit trip, HPCI auto =atically initiated due to low reactor water level. The turbine cane up to speed and flow and then auto-isolated. The isolation was 4 ediately reset and the turbine vnually initiated. HECI perforced satisfactorily until shut down cannally. The visible j
annunciation was 4 ediately. reset, and any alarm that would indicate the cause 3
of isolation cleared at that ti=e.
One operator, howcVer, did report observing an excessive sten = flow alar =.
Designation of Antarent Cause of Occurrence j
At this time the definite cause of the HPCI auto-isolation has not been determined.
Analysis of Occurrence Following the auto-isolation, EPCI was = anum 11y initiated and. performed satis--
factorily to restore vessel inventory. If EFCI had failed to start, safe shut-down of the reactor would have'been acco=plished with the remaining engineered
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safeguard systc=s. The failure caused no damage to any systers, structuresj or-co=ponents. There were no adver::e effects to the health and safety-of the public, and there were no personnel injuries or exposures.due to this occurrence..
Corrective Action Extensive effort has been exerted to deter =ine the exact cause of'the HPCI4 isolation. Each area that will cause an auto-isolation has been investigated.
The time delay in the excessive steanflow logic was verified'and found to.be satisfactory.. The calibration end operation of the PdIS switches for excessive steamflow wereverified and found to be satisfactory. Calibration of thei G308290077 741213 PDR ADOCK-05000260 S
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(j j r;' rrective Action (continued) pressure switches indicating a ruptured turbine exhaust diaphragn was verified satisfactory and the diaphragns were not n:ptured. The alarm for the stea=line space te:rerature high did not alarm. This alarm setpoint is lower than that required for an isolation and has to be reset at another panel before the annunciator can be cleared.
It is believed that the high level in both the gland seal condenser a*.d the turbine exhaust drain pot was an indication of water in the turbine exhaust line. As a result, a surge in the steamline as the exhaust line blev free probably initiated the isolation by high stecnflow si nal.
Tnis condition did not exist during the manual start of HPCI i cdiately 6
following the auto-isclation.
The motor for the gland seal condensate pu=p has been repaired and returned to service.
s Failure Data Previous auto-inclations for units 1 and 2 were reported in Abnormal occurrence Fieports3FAO-733Si,EFAO-7414W,EFAO-7435W,andEFAo-So-260/744W.
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Decenber 13, 1974 l'a'-
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I;,s, Mr. Edson G. Case
'{'N' 4,,e Acting Director of Licensing Office of Re8ulation
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U.S. Atonic Energy Connission Washinyon, DC 20545
Dear l'r. Case:
TE iESSEE VALLEY AUT:iORITY - BRO',CS FERRY ITUOLEAR PL4IiT UIIIT 2 -
DOCKET 170. 50-260 - FACILITI OPE?aTII.", LICEIISE DPR A31M/.AL OCCURRE:iCZ REPORT 3?AO-50-260/7431W The enclosed report is to provide details concerning HPCI auto-isolation and is subnitted in accordance with Appendix A to Regulatory Guide 1.16, Revision 1, October 1973 This event occurred on Bro as Ferry liuclear Plant unit 2 on Decenber 3, 1974..
Very truly yours, TE:IUESSEE VALLZY AUTHORITY
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Director of Power Production Enclosure CC (Enclosure):
Mr. Iiornan C. Ibseley, Director Region II Re5ulatory Operations Office, USAEC 230 Peachtree Street,IiW., Suite 818 Atlanta, Georgia 30303 l
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