05000346/LER-1978-055-01, /01T-0:on 780605,safety Features Actuation Sys Sequencer Failed During Test.Caused by Design Deficiency in Sys Mod.Electrical Slide Link Uses & Mgt Controls for Slide Links to Be Reviewed

/01T-0:on 780605,safety Features Actuation Sys Sequencer Failed During Test.Caused by Design Deficiency in Sys Mod.Electrical Slide Link Uses & Mgt Controls for Slide Links to Be Reviewed

ML19319B883
Person / Time
Site:	Davis Besse
Issue date:	06/16/1978
From:	Albert J TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19319B873	List: 05000346/LER-1978-055, Forwards LER 78-055/01T-0 05000346/LER-1978-055-01, /01T-0:on 780605,safety Features Actuation Sys Sequencer Failed During Test.Caused by Design Deficiency in Sys Mod.Electrical Slide Link Uses & Mgt Controls for Slide Links to Be Reviewed
References
LER-78-055-01T, LER-78-55-1T, NUDOCS 8001280743
Download: ML19319B883 (4)

LER-1978-055, /01T-0:on 780605,safety Features Actuation Sys Sequencer Failed During Test.Caused by Design Deficiency in Sys Mod.Electrical Slide Link Uses & Mgt Controls for Slide Links to Be Reviewed

Event date:
Report date:
3461978055R01 - NRC Website

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• . EVENT DESCRIPTICN AND PROSABLE CONSEQUENCES h The test failed due ]

I o 1: 1 l On 6/2/78, the "18 Month SFAS Surveillance Test" was conducted.'

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l to an SFAS sequencer failing to properly operate in SFAS Channel 1.

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l o 4.: i i revealed there was a design deficiency cocbined with the slide links being incorrect y Had an SFAS actuation occurred, and if there was a loss of offsite power, j left open.

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DAVIS-SESSE UNIT ONE HUCLEAR POWER STATION SUPPLEMENTAL INFORMATION TO LER NP-32-78-05 j

DATE OF EVENT:, June 5, 1978 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Safety Features Actuation System (SFAS) Sequ,encer Failure Conditions Prior tc Occurrence:

The unit was in Mode 6 with Power (MRT) = 0, and

. Load (MWE; = 0.

Description of Occurrence: On June 2,1978, the "18 Month SFAS Surveillance Test",

ST 5031.07, was conducted. The test failed due to an SEAS sequencer failing to properly operate in SFAS Channel 1.

Troubleshooting was performed supported by Power Engineering personnel.

Investigation of the problem continued until June 5, 1978, at which time the apparent cause(s) of the problem was determined.

On that date,' Region III of the. U. S. Nuclear Regulatory Commission was notified of the problem by telephone. This occurrence is being reported per Technical Specifica-tion 6.9.1.8.1.

J Cause of Occurrence:

The cause was a design error in a system revision. The chronological sequence which follows should best illustrate the sequence of events and what led to the events of June 2, 1978.

(1) 12/76 - Bechtel Power Corporation issued a System Revision Notice, 'SRN 221E, which was designed to provide sequencer operation for two additional design conditions:

(a) If a diesel were stopped during an SFAS actuation and later offsite power was lost, the sequencer would be restarted; (b) If diesel were supplying essential busses and then an SEAS actuation occurred', the sequencer would be started. There was a design deficiency in SRN 221E which would inhibit proper function-of the SFAS sequencers.

(2) 2/14/77 - SRN 221E was installed by construction personnel, scheme checked per Construction Wotk Permits 48-E-12, 13 and 24-E-51.

Apparently at least four terminal block connecting links (slide links) were lef t open, thus negating

- the condition (b) change of this SRN.

(3) 2/20 '- 2/23/77 - TP 310.02, "SFAS Integrated Test" was successfully. per-formed. This test procedure had been modified to test SRN. 221E changes.

It failed to detect the misapplication of the design due to the slide links being in the open position.

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(4) 2/23/77 - 6/2/78 - Sometime within this period all but two of the open ter-minal block slide links were closed enabling the design deficiency.

The actual date or reason for this event has not as yet been found.-

(5) 6/2/78 - SFAS 18 Month Test, ST 5031.07, was conducted. This test was a repeat of TP 310.02. The test failed when conducted on SA Channel 1, as a direct result of the slide links being closed and the design deficic'ncy j ;

1 in SRN 221E.

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'(6) 6/3/78 - In the course of troubleshooting, two SFAS relay contacts which h

were part of the circuitry described here, but not causing any test failures were found not to have wires going from the relays to the ' external connec-tions.

This'was a manufacturer's error that did not affect the test or the safety of the system because it was redundant wiring.

(7) 6/4/78 - Slide links in the open position were discovered in the channel il which appear.ed to function properly during ST 5031.07.

(8) 6/5/78 - Power Engineering personnel confirmed that a design, deficiency existed in both SA Channels 1 and 2.

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~~' Analysis of occurrence: Had an SFAS actuation occurred after the time when the slide links were closed, and if 'there was a loss of offsite power, the sequencer il would not have automatically sequenced emergency core cooling system loads onto il the essential busses. In all such cases, except condition (b), sequenced loads l

would not load onto the bus. The operators, however, in such conditions would have been able to manually load the emergency diesel generator.

In condition (b),

all normally sequenced loads could have immediately loaded onto the bus if they

!j received a simultaneous incident level 1, 2, 3 or 4 SFAS actuation.

The tripping il of various incident levels on SEAS is not calculated to occur simultaneously except for a major pipe break (28" or 36").

Incident levels 1 and 2 (high pressure injection pumps and containment air coolers) trip at a reactor coolant pressure less than 1600 psig. Incident level 3 (decay heat pumps)' trips at a reactor l.

coolant pressure less than 400 psig or a containment pressure less than 4 psig.

ll Incident level 4 (containment spray pumps) trips at a containment pre,ssure greater than 24 psig.

The component cooling water and service water pump would have

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been previously started when the loss of power occurred.

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Corrective Action

The corrective action taken will be a modification to correct the design and correct any hardware deficiencies (Facility Change Request 78-268).

ij Corrective actions include a review of slide link uses and =anagement controls for

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as specification drawings) to insure that.they properly reflect vendor supplied equip =ent.

,l Failure Data: This is not a repetitive occurrence.

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