ML19319B766

RO NP-33-77-49:on 770803,loss of Containment Normal Sump & Total Flow Instrument String.Caused by Design Error.Sump Pump Discharge Piping Draining After Pumps Stop,Registering Nonexistentflow.Timers Put on Pump Starters

ML19319B766
Person / Time
Site:	Davis Besse
Issue date:	08/30/1977
From:	Hitchens D, Lingenfelter J TOLEDO EDISON CO.
To:
Shared Package
ML19319B662	List: ML19319B660 ML19319B766
References
NUDOCS 8001270231
Download: ML19319B766 (3)

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• EVENT DE SCRl*floM .

O gi ne 7 e, of the Reactor Coolant System Leakage Detection Systems, (the Contain d

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-'S g ; ment Normal Sump and Total Flow Instrument String, was inoperable. The n as .

] 'g; remaining two leakage detection systems were operable. (NP-33-77-49)

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• l CAU$f DESCRIPTION l ois ] There was a design error in the lines leadin;; from the flow totalizer,

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) TOLEDO EDISON COMPANY DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLEMENTAL INFORMATION FOR LER NP-33-77-49 l

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DATE OF EVENT: August 3,1977 FACILITY: Davis-Besse Unit l'

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IDENTIFICATION OF OCCURRENCE: Loss of Containment Normal Sump and Total Flow Instrument String.

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Conditions Prior to occurrence: The plant was in Mode 3, with Power (MWT) = 0, and Load (MWE) = 0. i l

Description of Occurrence: On August 3, 1977 at 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />, the Reactor Operator i

observed FQI-2801 (Electro-Mechanical Totalizer) recording a flow out of the Con- )

) tainment Normal Sump. The Containment Normal Sump Pumps aere not running, nor was j the sump level changing. The Containment Normal Sump Total Flow Instrument String  :

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j was declared ir. operable. The remaining two leak detection systems (Radiation Indi-l cating Switches (RIS) 5029 and RIS 5030) were verified as being operable by perform-ing Surveillance Test, ST 5099.05, the Radiation Monitoring System Channel. A work

\s ,)t request was prepared and issued to the Instrument and Control Section. This is the second such occurrence and entered the station into the Action Statement of Techni-cal Specification 3.4.6.1.

! Designation of Apoarent Cause of Ocet trence: The cause of this occurrence was a design error (improper application) in that the sump pump discharge piping drains after the sump pumps stop. In addition to the sump pump discharge piping draining,

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FT-2801 sensing lines drain also. As these sensing lines and piping drained, a

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differential pressure was sensed hy the flow transmitter. This in turn caused the F?I-2801 to indicate an out flow. Also, if the sensing lines drained different

amounts, as might ha ,e happened due to the flow orifice, a constant differential pressure would be seen by the flow transmitter, and the flow totalizer, FQI-2801, I would continue to count.

Analvsis of Occurrence: Since there was no Reactor Coolant System leakage, and the 4

remaining two leak detection systems were operable, there was no danger to the

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health and safety of the public or to station personnel.

! Corrective Action: -A Facility Change Request (FCR 77-165) was prepared at the time

of the first occurrence. At the second occurrence, the problem was identified as l

being the draining of the piping. A second Facility Change Request (FCR 77-213) was issued. The problem was resolved by putting timers on the pump starters in

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'~ the Motor Control Centers for the two sump pumps. These timers are energized every time the motor starters are and record total elapsed time that the pump runs.

q'- (Timers operate on an accumulative basis, and do not reset back to "0" by them-selves.) In addition, a work package is being prepared to change the piping at the

next outage so that it remains full of water when the sump pumps are stopped.

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TOLEDO EDISON COMPA!Ti

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DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPL? MENTAL INFORMATION FOR LER NP-33-77-49 PAGE 2

The r.'.owrate of the pumps was then determined and this multiplied by the elapsed j time yields the total volume of water pumped out of the sump. ST 3041.01, Con-tainment Normal Sump Level and Flow Monitoring System Calibration wa- revised to utilize the elapsed time that the pump (s) ran, and was successfully performed on August 10, 1977. This removed the station from the Action Statement of Technical Specification 3.4.6.1.

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Failure Data: On July 7, 1977, the Containment Sump Level and Flow Monitoring System was inoperable (NP-33-77-20) . The cause was, however, different.

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