ML20126H910

Safety Evaluation Re Adequacy of Electric Distribution Sys Voltages.Voltage Analyses Demonstrate That Class IE Equipment Terminal Voltages Remain within Acceptable Operating Limits for Postulated Worst Case Conditions

ML20126H910
Person / Time
Site:	Zion  File:ZionSolutions icon.png
Issue date:	04/09/1981
From:	Office of Nuclear Reactor Regulation
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ML20126H907	List: ML20126H902 ML20126H910
References
NUDOCS 8104220397
Download: ML20126H910 (4)

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, i ENCLOSURE i 9  ;

. SAFETY EVALUATION f ZION STATION - UNIT NOS. 1 AND 2 DOCKET NOS. 50-295 AND 50-304 l l

1 s ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES I

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INTRCDUCTICN AND

SUMMARY

Comraonwealth Edison' Company (Ceco) was requested by NRC letter dated Augast (

8,1979 to review the electric pcwer system at Zion Station Units 1 end 2.

The review was to consist of:

(a) Detennining analytically the capacity and capability of the offsite r pcwcr system and the :nsite distribution system to automatically start s

as well as operate all required safety leads within their required

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voltage ratings in the event of (1) an anticipated transient, or (2) an accident (such as LOCA) without manual shedding of any electric loads.

(b) Detennining if there are any events or conditions which could result in the simultaneous or, consequential loss of both required circuits from

- the offsite network to the onsite electric distribution system thus violating the requirements of 'iDC 17.  ;

The August 8,1979 letter included staff guidelines for perfonning the required  ;

voltage analysis and the licensee was further required to perform a test in ,

. order to verify the validity of the analytical results. CECO responded by lettars dated September 17, 1975, November 1,1979, 'Cecember la,1979, June 23,  !

1980, August 13, 1980 and February 17, 1981. A detailed review and ecnnical l

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sva14ation of the submittal was performed by EG&G under contract to NRC, and with general supervision by NRC staff. This work was reported in EG&G's 7t:nnical Evaivatien Reperts (TER), " Adequacy of Station Electric Distribution 3 -stem Voltages, Zion Station" dated Cecember 1980 (attached). We have reviewed  ;

-rese reports and concur in the conclusions that the offsite power system and

nsite distribution system are capable of providing acceptable voltages at the treinals Of the Class lE equipment for <cest case station electric icad and

rid v ltages.

El'L*;4 !?! C?ITERLA

~he :riteria used by E38G in this technical evaluatien of the analysis S:1. des 3CC 5 ( Sharing of Structures, Systems, and Components"), 3CC 13

":nstrumentati:n and Centrol"),.and 3DC 17 (" Electric power Systems") of 1::endix A to 10 CFR 50; IEEE Standard 203-197a (" Class 1E P:wer Systems for Nu: lear hwer 3enerating Statiens"); ANSI C34.1-1977 (" Voltage Ratings for Elt: ri Nwer Systams and E:;uipment -SCH:)"; and the staff positions and guidelines in :ne NRC letter to CECc dated August 3,1979.

IULY3*3 AND TEST FEA URE3

~~,e analysis was perf:rmed using the reserve auxiliary transformer wi n the  ;

.axicum and minimum switchyard (grid) voltage (254 ky and 343 kv respectively).

M mas been established that emergency a kv leads would operate within alicw-1: e limita f:r -ne wors: case ::nditions noted acove. AC c:ntacters used 1

': _li!C y switchgear could potentially drop out during transient vc1: age  !

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t potential deficiency was not considered significant as the contactors are f f

rated for 70% and the worst transient was calculated at 69.1% of nominal voltage. Therefore any margin associated with the 70% voltage rating would

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prevent the contactor from dropping out. Should any of the contactors. drop out during this postulated worst case transient, they would reenergi:e momentarily as the voltage recovered.

A voltage analysis is not provided for the Z winding (dreserve feed") of one  ;

unit station auxiliary transformer supplying power to more than one class IE bus of the other unit. However, there are procedures as well as an j automated restriction via auxiliary contacts to prevent paralleling Class 1E  ;

buses by the " reserve feed" except when the unit is in cold shutdown. The l procedures also require that parallel " reserve feed" be discontinued pricr to leaving cold shutdown. 'de consider these provisions acceptable. .

l The voltage analysis was verified by measuring, on both units, the grid and station distribution bus voltages, and the actual lead of the buses and selected equipment while both units were snutdown. The c:mparison showed

na: calculated voltages for the Class 1E buses are witnin -0.5a and -0.55:

of the measured bus voltages f:r both units. This close ::rrelation verifies )

the adequacy of the analysis submitted.

CONCL'JS!CNS l

We have reviewed :ne EG&G Technical Evaluati:n Reports and concur in :ne j findings that:

(1 ) CE o nas :rovided verified voltage analyses is demonstrate :na: :ne Class 1E e:vi: ment terminal vo': ages remain 41:hin ac:eptsole

erating l'aits f:r :se ;os ulated .ces: case ::nciti:ns.

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'2) "he test used to verify the analyses was valid and showed the analyses - I to be accurate. .

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l3) OE2's reaffi:-r.atien of compliance witn GDC 17 requirements is acceptacle.

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FCRM EC&G W '

(me,. H 731 ' r INTERIM REPORT ,

Accession No, f

R& port No. EGG-EA-5306 j Centract Program or Project

Title:

f Electrical, Instrumentation and Control System Supperc j i

I Subject of this Documents i e

Adequacy of Station Electric Distribution System Voltages, Zion Station, Unic 2, j Docket No. 50-304, TAC No. 13008 Type of Document: l

- Informal Report l

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' Author (s): I i

A. C. Udy  ;

i Date of Document:

December 1980  !

Responalble NRC Individual and NRC Office or Division:

Paul C. Shemanski, Division of Licensing  ;

l 1

This document was prepared primarily for preliminary or internal use. it has not received full review and approval. Since there may be substantive changes,this document should not be considered final.

t EG&G laaho, Inc.  !

Idaho Falls, Idaho 83415 l l

l Prepared for the  !

U.S. Nuclear Regulatory Commission l Washington, D.C.

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Under DOE Contract No. DE AC07 761001570 '

NRC FIN No. A6256 )

INTERIM REPORT 03 9 T

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. n.n, 7 INTERIM REPORT  !

Accession No. I e

Report No. ECC-EA-5305 i

Contract Program or Project

Title:

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. t Electrical, Instrumentation and Control System Support l

l Subject of this Documents l

Adequacy of Station Electric Distribution System Voltages, Zion Station, Unit 1, j Docket No. 50-295, TAC No. 13007 }

l Type of Document: , j

-Informal Report f

f Author (s): f A. C. Udy Date of Document: {

Oecer.ber 1930  :

. t Pesponsible NRC Individual and NRC Office or Division: . -

[

Paul C. Shemanski, Divisica of Licensing l i

This document was prepared primarily for preliminary or internal use. it has not received full review and approval. Since there may be substantive changes this document should j

not be considered final.  :

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EG&G Idaho. Inc. ,I idaho Falls. Idaho 83415  !

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Prepared for the l U.S. Nuclear Regulatory Commission j Washington, D.C.  !

Under DOE Contract No. DE AC07 761D01570 i NRC FIN No. A6256 INTERIM REPORT hlA 20 - ,

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