05000395/LER-1995-001, :on 950210,potential Loss of Automatic Engineered Safety Features Actuation Due to High Energy Line Break in Turbine Bldg Occurred.Nonconformance Notice Was Written to Address Degraded Condition

:on 950210,potential Loss of Automatic Engineered Safety Features Actuation Due to High Energy Line Break in Turbine Bldg Occurred.Nonconformance Notice Was Written to Address Degraded Condition

ML20081B465
Person / Time
Site:	Summer
Issue date:	03/10/1995
From:	Fowlkes R, Gabe Taylor SOUTH CAROLINA ELECTRIC & GAS CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-95-001, LER-95-1, RC-95-0067, RC-95-67, NUDOCS 9503160194
Download: ML20081B465 (5)

LER-1995-001, on 950210,potential Loss of Automatic Engineered Safety Features Actuation Due to High Energy Line Break in Turbine Bldg Occurred.Nonconformance Notice Was Written to Address Degraded Condition

Event date:
Report date:
3951995001R00 - NRC Website

text

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South Carolina Electric & Ga3 Company Gary J. Taylor

,,. y P.O. Box 88 Vice Preside.it J:nkinsville, SC 29065 Nuclear Operations (803) 345-4344

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March 10, 1995 Refer to: RC-95-0067 Document Control Desk U. 5. Nuclear Regulatory Commission Washington,DC 20555 Gentlemen:

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Subject:

VIRGIL C. SUMMER NUCLEAR STATION DOCKET NO. 50/395 OPERATING LICENSE NO. NPF-12 LICENSEE EVENT REPORT (LER 950001)

Attached is Licensee Event Repor t No. 95-01 for the Virgil C. Summer Nuclear Station.

This report is submitted as a voluntary LER.

Should you have any questions, please call at your convenience.

Very truly yours, i

Gary J. Taylor MJZ/GJT/nkk Attachment c:

O. W. Dixon R. R. Mahan (w/o attachment)

R.L White S. Dembek S. D. Ebneter NRC Resident inspector J. B. Knotts Jr.

S. R. Hunt S. F. Fipps J. l. Byrd NSRC Central File System RTS (ONO 950009)

Files (818.05 & 818.07) 1 " oo 7{k 95o3160194 950310 a

PDR ADOCK 0500o395 S

PDR NUCLEAR EXCELLENCE-A SUMMER TRADITIONI J

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This LER report provides additional followup in the form of a voluntary LER.

On February 7,1995, V. C. Summer Nuclear Station (VCSNS) determined that a potential loss of automatic Engineered Safety Features actuation could result from a High Energy Line Break in the Turbine building. The condition was determined to be bounded by the Main Steam Line Break accident analysis.

Based on Generic Letter 91-18, Section 6.7, the Solid State Protection System (SSPS) was determined to be acceptable with credit taken for manual operator actions. Manual operator action necessary to mitigate the effects of degraded condition were emphasized. The plant was at approximately 100 percent power throughout the occurrence. The cause of this condition was determined to be a nonconformance of the SSPS circuitry because it did not account for this particular failure scenario. On February 11,1995, repairs fully restored automatic actuation features of SSPS.

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PLANT IDENTIFICATION-Westinghouse - Pressurized Water Reactor i

EQUIPMENTIDENTIFICATION:

Solid State Protection System Ell 5 System Code -JE 1

1 IDENTIFICATION OF EVENT:

j An evaluation of Industry Operating Experience information was performed by VCSNS.

Engineering Staff.

EVENT DATE:

February 10,1995, at 1652 hours0.0191 days <br />0.459 hours <br />0.00273 weeks <br />6.28586e-4 months <br />.

REPORT DATE: March 12,1995 This report was initiated by agreement between VCSNS Licensing Staff and USNRC to provide cdditional followup information in the form of a voluntary LER. Off-Normal Occurrence Report 95-009 documents the voluntary nature of this report..

l CONDITIONS PRIOR TO THE EVENT:

MODE 1 - 100% Reactor Power

DESCRIPTION OF EVENT

q On February 7,1995, VCSNS Engineering Staff determined from an evaluation of Industry Operating Ex serience information that a potentialloss of automatic Engineered Safety Features (ESF) actuation could result from a High Energy Line Break (HELB) in the Turbine building (TB). The plant continued to run at approximately 100 percent power throughout the occurrence.

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'CAUSE OF EVENT:

VCSNS Enclineering Staff determined that a HELB in the TB could create a failure (short to _

2 ground) o circuits which provide inputs to the SSPS. Failure of these circuits could result in the degradation of the SSPS d ue to loss of power supplies to logic circuitry which provide automatic actuation of ESF equipment from the system. The cause of this condition was determined to be a nonconformance of the SSPS circuitry because it did not account for this particular failure scenario.

ANALYSIS OF EVENT

An evaluation of the plant's design basis accidents with respect to this degradation concluded that the Main Steam Line Break (MSLB) safety analysis is the bounding condition for this event end is met without reliance on manual operator actions for at least 10 minutes. After the 10 minute delay, manual operator actions are credited with isolation of the MSLB, initiation of emergency feedwater for long term cooling, and establishing charging alignment for restoration of shutdown margin.

3 The success of the manual operator actions was verified through simulator scenarios utilizing established Emergency Operating Procedures.

The potential for a MSLB in the TB causing a loss of both trains of ESF was evaluated using the VCSNS Probabilistic Risk / Safety Analysis model. The increase in Core Damage Frequency remained well below the generally accepted threshold of 1.0E-6 for the time required to take

corrective action

This condition was evaluated with respect to the guidance provided in GL 91-18 for resolution of a degraded or nonconforming condition, and was determined to be acceptable with credit taken for manual operator actions as allowed in Section 6.7. Station Order 95-03 was promatly issued to emphasize manual operator action necessary to mitigate the effects of the degrac ed condition.

IMMEDIATE CORRECTIVE ACTIONS

- A Nonconformance Notice was written to address the degraded condition.

Station Order 95-03 was promptly issued to emphasize manual operator action necessary to mitigate the effects of the degraded condition. The Station Order also required that:

1)

The TB crane be red tagged to prevent heavy loads over the steam piping to the turbine.

2)

Both trains of ESF equipment be maintained fully operational.

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UCENSEE EVENT REPORT (LER) TEXT CONTINUATION

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The success of the manual operator actions was verified through simulator scenarios utilizing established Emergency Operating Procedures.

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The station promptly completed repairs on February 11,1995, to the SSPS which eliminated its susceptibility to failures from inputs that could be affected by HELBs in the TB.

A followup to the initial February 10,1995, voluntary telephone report was made on Februaiy 11,1995.

All actions necessary to address the degraded condition for the automatic actuation of ESF components have been completed. The automatic actuation features of SSPS linve been fully restored.

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ADDITIONALCORRECTIVE ACTIONS:

No additional corrective actions are necessary to address the degraded condition, however, changes to additional channels of logic circuits which do not affect the SSPS power supplies will i

b3 made during the next scheduled p. ant outage. These changes do not affect the automatic i

actuation features of ESF components but are,ncluded in the Nonconformance Notice due to i

their identification during the evaluation of this issue.

PRIOR OCCURRENCES:

None

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