05000280/LER-1979-008-01, /01T-0 on 790323:during Load Study of 480 Volts Ac Emergency Bus,Discovered That an under-power Condition Could Exist for Postulated LOCA with or W/O Loss of Offsite Power. Caused by Design Deficiencies During Const

/01T-0 on 790323:during Load Study of 480 Volts Ac Emergency Bus,Discovered That an under-power Condition Could Exist for Postulated LOCA with or W/O Loss of Offsite Power. Caused by Design Deficiencies During Const

ML18114A422
Person / Time
Site:	Surry
Issue date:	04/05/1979
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML18114A421	List: 05000280/LER-1979-008, Forwards LER 79-008/01T-0 05000280/LER-1979-008-01, /01T-0 on 790323:during Load Study of 480 Volts Ac Emergency Bus,Discovered That an under-power Condition Could Exist for Postulated LOCA with or W/O Loss of Offsite Power. Caused by Design Deficiencies During Const
References
LER-79-008-01T-01, LER-79-8-1T-1, NUDOCS 7904100282
Download: ML18114A422 (3)

LER-1979-008, /01T-0 on 790323:during Load Study of 480 Volts Ac Emergency Bus,Discovered That an under-power Condition Could Exist for Postulated LOCA with or W/O Loss of Offsite Power. Caused by Design Deficiencies During Const

Event date:
Report date:
2801979008R01 - NRC Website

text

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LICENSEE EVENT REPORT

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(?LEASE PRINT O.'PE ALL REQUIRED INFORMAT!ONi lo I-10

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~~~~~~ ~J@lo Is 10 10 10 12 1s ~0L~I 2 I 3 I 1*.L2.J©I o I L+ I o I s 1 7 l.1JG) 60 61 DOCKET NUMBER 68 69 EVENT DATE 74 75 REPORT DATE 80 EVENT DESCRiPTION AND PROBABLE CONSEQUENCES@*

!During a load study of the Unit 1 480 VAC Emergency Bus, the Architect Engineer dis-

[TITI 1coyered that an under power condition could exist for a postulated loss of coolant J

[o 14] 1accident with or with __ out the loss of off-site power.

This under power condition could J [ill] 1prevent the proper functioning of engineered safeguards equipment.

This condition j

IT.))] 1would exist until loads on the emergency bus w_ere manually shed to a point where the Io !TI !bus could be re-energized. __!!1-i~~ an~~-ent contrary to the intent of Technical Speci::-j

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[~JI] L£_~cation 3.16 and is reportable as per Technical Specification 6.6.2."A.9.

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CAUSE

CAUSE CODE CODE SUBCODE COMPONENT CODE [ill]

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20 l=1 31 REVISION NO.

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32 COMPONENT ACTION FUTURE EFFECT SHUTDOWN

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ATTACHMENT NPRD-4 PRIME -::;OMP.

TAi<:EN ACTION ON PLANT METHOD HOURS SUBMITTED FORfv1 SUB.

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36 37 40 41 42 43 1 1 o 1o 1s l CAUSE DESCRIPTION AND CORRECTIVE ACTIONS @

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\\!he under power condition developed as a result of design deficiencies during. construe:.!

OJI] ltion.

The proposed corrective ar.tion is to install an additional Category I, Class lE J [J]Ij t_80 V load cente:.: on each emergency bus.

Alternative solutions are *being investigatedj r::ITIJ I for Unit /12 switchgear.

• The health and safety of the general public were not-affecte(H [ill]

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9 FACILITY STATUS

% POWER OTHER STATUS IT.TI] ~@- L.? I O.j ~J@l,_____1_-JA ____ __.

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RELEASED OF RELEt,SE AMOUNT OF ACTIVITY

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(Attachment, paw. of 2)

Surry Power Station, Units 1 & 2 Dockat Nos:

50-280/281 Report No: 79-008/0lT-0 Event Date:

3/23/79 Under Power of 480 V Emergency Bus

1.

Description of Event

During a load study of the Unit 1 L180 VAC emergency bus, the Architect Engineer discovered that an under power condition could exist for a postulated loss of coolant accident (LOCA) with or without loss of off-site power.

The projected maximum load following a LOCA for Emergency Bus lH.l was 1661 KVA, or 125;; of rated capacity of the 4160 to 480 VAC transformer and output line circuit breaker 14Hl.

The projected maximum

• 1oad.for bus lJl and output line *circuit breaker is 1737 KVA, or 130%

• of

• -rated capacity.

A load study of Unit !!2 480 VAC emergency bus has not been completed, but it appears a similar under power condition exists.

This event is contrary to Technical Specification 3.16 and is repor-table as per Technical Specification 6,6,2.A.9.

2.

Probable Consequences and Status of Redundant Systems:

The probable consequences of an under power condition would be the*

loss of vital engineered safeguards due to the tripping of the output breaker o:f the 4160 to 480 *vAc transformer.

This condition would exist until loads on the emergency bus were manually shed to a point where the bus could be re-energized.

An under power condition was projected to exist on the redundant emergency bus..

The health and safety of the public rwere not affected.

3.

Cause

The LOCA under power condition developed as a result of design defi-ciencies during construc.tion.

4,

Immediate Corrective Action

Unit Ill and Unit //2 were in the cold shutdown mode, and will remain in this mode until this deficiency is corrected.

5.

Subsequent Corrective Action:

An additfonal Class lE 480 V load center will be established for*each of the emergency buses (lH, lJ),

This will *allmv* the redistribution of sufficient load to eliminate the under power condition on each.bus, and provide the capability for future expansion.

'1, (Attachment, page 2 of 2)

Surry Power Station, Units Docket Nos:

50-280/281 Report No:

79-008/0lT-0 Event Date:

3/23/79 1 & 2*

Under Power on Lf80 V Emergency Bus (Continued)

5.

Subsequent Corrective Actions:

(Cont'd:)

Alternate solutions are being investigated for Unit 112 under power conditions ou 480 V emergency load center, due to room restraints and a long lead time for new equipment.

This modification will be accomplished prior to departing cold shutdown.

6.

Actions Taken to Prevent Recurrence:

Existing administrative and procedural controls to review any proposed change to the loading scheme of the emergency load centers will be followed.

In addition, a load study will be conducted as a part of the Emergency Bus modification to verify adequate load capability.

7.

Generic Implication~:

A load study is being conducted on Surry Unit #2 to determine load and possible corrective actions.

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