05000368/LER-1979-022-99, Changes in Control Circuitry of Containment Cooling Fans Discovered Inadvertently Omitted.Caused by Oversight.Mods Completed

Changes in Control Circuitry of Containment Cooling Fans Discovered Inadvertently Omitted.Caused by Oversight.Mods Completed

ML19345B486
Person / Time
Site:	Arkansas Nuclear
Issue date:	11/19/1980
From:	Shively C ARKANSAS POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19345B473	List: 05000368/LER-1979-022, Forwards Updated LER 79-022/99X-1 05000368/LER-1979-022-99, Changes in Control Circuitry of Containment Cooling Fans Discovered Inadvertently Omitted.Caused by Oversight.Mods Completed
References
LER-79-022-99X, LER-79-22-99X, NUDOCS 8012010381
Download: ML19345B486 (4)

LER-1979-022, Changes in Control Circuitry of Containment Cooling Fans Discovered Inadvertently Omitted.Caused by Oversight.Mods Completed

Event date:
Report date:
3681979022R99 - NRC Website

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Mf,OH,0.T8 80 EVENT Of SCRIPTION AND PROBASLE CONSEQUENCES h gp] lDuring a review of the Millstone Design Modifications, it was discovered i tthat changes in the control circuitry of the Containment Cooling Fans i

um Iwere inadvertantly left out of the design package. When safety equipment 1 o 4 tsequenced onto off-site power following an ES signal, the Containment I

e s ICooling Fans would be energized at T=0 seconds as opposed to T =20 secondst o e, m iper Millstone Syndrome design intent.

No similar occurrences.

Reported i i c i.a ifor infonnation only.

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Evaluation of the consequences of past operation indicates E g]Ithat voltages on the ESF buses would not drop below the permissible mini-i Eg] Imum voltage. Assuming the ESF buses had deteriorated, the transfer to thei i mergency Diesel Generators would have occurred and the fans sequenced i

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Reportabic Occurrence Report No. 50-368/79-022/01X Rev. 1 2.

Report Date: 11/19/80 3.

Occurrence Date:

3/22/79 4

Facility: Arkansas Nuclear One - Unit Two Russellville, Arkansas 5.

Identification of Occurrence:

Millstone-Syndrome related design modification not completed.

Reported for Infonnation Only.

6.

Conditions Prior to Occurrence:

Steady-State Power Reactor Power 0

Wth flot Standby Net Output 0

we Cold Shutdown X

Percent of Full Power 0

g Refueling Shutdown Load Changes During Routine Power Operation Routine Startup operation Mode 5 Routine Shutjown Operation Other (specify) 7.

escription of Occurrence:

During a review of the Millstone Design Modificatior,s, it was discovered that changes in the control circuitry of the containnent cooling fans were inadvertantly left out of the design change package.

When safety equipment sequenced onto off-site power following an Engineered Safety Feature (ESF) signal, the containment cooling fans would be energized et T=0 seconds as opposed to T=20 seconds per Millstone Syndrome design intent.

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Reportable Occurrence Report No. 50-368/79-022/01X Rev. 1 8.-

Designation of Apparent Cause of Occurrence:

Design X

Procedure' Manutacture Unusual Service Condition Including Environmental Installation /

Const ruction Component-Failure (See Failure Data)

Operator Other (specify) l i-i r

i 9.

Analysis of Occurrence:

i The design change omission was due to an oversight.

Evaluation of the safety-related-consequences of operation without start sequencing of the containment cooling fans was completed, concluding the safety of the plant was not affected.

The purpose of the omitted design modification j

was - t'o sequence start (20 seconds after the initiation of ESF signal with preferred power source available) the containnent cooling fans which otherwise would start immediately on the onset of an ESF signal.

The existing load flow studies indicate that the voltages on the ESF buses would not have dropped below the permissible minimum'vol.tages (had these fans started at T=0) as defined per the Millstone study.

In the event the voltages on the ESF buses had deteriorated below the acceptable ~' levels, the transfer to the on-site power (Emergency Diesel Generator) would have occurred and the cooling fans would have started in sequence (T=20 seconds),

an existing design feature.

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50-368/79-022/01X Rev. I 10.

Corrective Action

Immediately upon discovery, a Design Change Package was initiated to correct the omission.

These design modifications have been completed.

11.

Failure Data:

There have been no previous occurrences similar to this one.

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