ML19282B998

Provides Answers to Questions Raised at 790227 Meeting & Documents Info Presented Re Calculation Analysis of Min Voltage Levels & Offsite Electric Power Sys

ML19282B998
Person / Time
Site:	Arkansas Nuclear
Issue date:	03/13/1979
From:	Reuter D ARKANSAS POWER & LIGHT CO.
To:	Reid R, Stolz J Office of Nuclear Reactor Regulation
References
1-039-7, 1-39-7, NUDOCS 7903190241
Download: ML19282B998 (14)

Text

r  ;- -

't,*I ARKANSAS POWER & LIGHT COMPANY POST OFFICE BOX 551 LITTLE ROCK. ARKANSAS 72203 (501)371-4000 March 13, 1979 1-039-7 2-039-3 Director of Nuclear Reactor Regulation ATm: Mr. Robert W. Reid, Chief Division of Operating Reactors Branch #4 ATm: Mr. John F. Stolz, Chief Lightwater Reactory Branch #1 U. S. Nuclear Regulatory Ca mission Washington, D. C. 20555

Subject:

Arkansas Nuclear One-Units 1&2 Docket Nos. 50-313, 50-368 License Nos. DPR-51, NPF-6 GDC-17, Millstone (File: 1510, 2-1510)

Gentlenen:

The following information is provided to document the information presented in our meeting with the Staff on February 27, 1979, and to answ r questions that arose during the neeting.

Iten 1. Show by calculational analysis the muumum voltage levels that muld exist on each 4160V and 480V ESF bus if a IfXA wre to occur, paying special attention to the voltage transients during the starting of each ESF load. State all assumptions, describe the calculational schene, and evaluate the significance of the calculational results.

Item 2. Repeat Question el with the assumption that ST-1 is not available ard all ANO-1 loads are automatically transferred to ST-2.

Iten 3. Repeat Question #1 with the assumption that ST-3 is not available and all A!O-2 loads are autanatically transferred to ST-2.

9 790319 0 9'// f MEMBEA MCOLE SOUTH UTIUTIES SYSTEM

2-039-3 Mr. Robert W. Reid

• '* Mr. John F. Stolz m rch 13, 1979 Response: The initial conditions for the voltage studies are shown on Attachnent 1. Conservatism incorporated in the analyses is shown on Attachment II. The calculational method is s own on Attachment III. The Acceptance Criteria for voltages at the safety busses is shown on Attachnent IV. AttachTnt V shws the results of the analyses for A!D-1.

Upon a Full House Transfer of A!O-l loads to Startup TransfonTr

1. 2 (SU2) the resulting Steady State Imds muld be as snown on the first line. If a postulated IOCA (generating an ES signal) were to occur before, during or after the transfer to SU2, the resultant transient voltages would be as shown on the T=5-20 second portion of the Attachnent V. The T=S.S.

line represents the steady state voltages camprised of house loads and safety loads. These voltages are within the acceptance criteria.

Attachnent VI represents the results of the same analyses for AFD-2.

Iten 4. Justify, in tenns of human factors engineering cancepts, the desire that NRC allow credit for manual operator actions to overcame the apparent design inadegaacy of ST-2 to accarmodate its function for the present configuration and the proposed configuration.

Response: General Design Criteria #17 states in part:

". . .an offsite electric guer systen shall be provided to pennit functioning of structures, systens, and caponents important to safety."

" Electric power fran the transmission network to the onsite electric distribution systen shall be supplied by two physically indepmdent circuits . . . one of these circuits shall b3 designed to be available within a few seconds following a loss of coolant accident. ..

Our understanding of GDC-17 is that only one of the two required offsite circuits must be available by a " fast transfer" and that the second source is considered a delayed source (e.g. manual access) . We further understand that the GDC is concerned only with safety loads.

Based on this, we believe our current manual access to SU2 is allowed by the GDC. We further state that since SU2 will prnvide aderpate prer, with m unacceptable voltages, while supply both AfD-1 and ANO-2 full safety loads cimaltancer/:ly, that the transfonner design is not inadegaate.

1-039-7 2-039-3

. .. Mr- Robert W. Reid Mr. John F. Stolz March 13, 1979 It s 5. An interlock between MD-1, and NO-2, and Sr-2 has been proposed.

(a) can the operation /maloperatioWfailure of any part of the interlock (including each sensor) cause both RD-1 and N O-2 loads to be applied to ST-2?

(b) Can the operatioWmaloperation/ failure of any part of the interlock (including each sensor) prevent the manual loading of A!D-1 or NO-2 ESP loads onto Sf-2?

Response: Attachnent VII shJws our conceptual design for the interlocking mechanism. The interlock only affect the autmatic portion of the systs. Manual overide is always available. Tha specific answer to each of the above itms is "no."

It m 6. What is the equivalent undervoltage setpoint at the 4160V buses coordinated witn your proposed mtpoint at a value of 92% of rated voltage on the 480V buses?

Response: With no load on the 480V bus, the voltage on the 4160V bus necessary to maintain 92% of 460V on the 480V bus, is 91.69%

of 4000V. As the load is increased on the 480V, the voltage on the 41607 bus must increase to maintain 92% of 460V on the 480V bus. This is shJwn on Attachnent IX.

It s 7. Describe how the proposed undervoltage sensor on the 480V buses will detect all faults on the station service transformer, the 480V ESF systms, and unacceptable voltage degradation on the 4160V ESF systes.

Response: As shown on Attachaent VIII, 92% of 460V is the minimum acceptable for continuous operation of the 480V system. The 4160V bus nust be at or above 91.69% of 4000 V to assure acceptable voltage at the 480V busses. 91.69% of 4000 V is ab]ve the mininun required for the 4160V systs. Tharefore, for any fault upstream of the 480V syst s , degraded voltage muld first be e/idenced on the 480V systs. Placing the undervoltage relay on the 480V system therefore provides direct protection at the point at which an undervoltage would first occur if an undervoltage condition was to occur.

Item 8. Provide the results of your analyses which supports your letter of October 25, 1978, for ANO-1.

Response: Attachnent X shows those results. All the voltages (S.S. and transient) are acceptable.

1-039-7 1-039-3

. .. Mr. Pobert W. Reid Mr. Joh F. Stolz March 13,1979 Iten 9. Can Startup Transformer #2 provide adequate pcwcr with acceptable voltages for a shutdcun of one unit cancurrent with a postulated IDCA on the other unit?

Response: The actual loads necessary to safely sh.It dcun ND-1 or 2 are a subset of the total safety loads. SU2 will provide full safety loads for Inth units simultaneously. Therefore, the response to the question is "yes."

Iten 10: Is the rating assumed, for Startup Transfomer #2, in the analysis the N A rating and if so justify?

Response: The thermal ratings assumed in the analyses are FOA ratings.

Power for transformer cooling is available fran both units, one source fran MD-1 and the other fran Ato-2. The transfer fran one source to the other is autanatic on loss of voltage of either source. Only one source is needed at any time.

Itan ll: Do your plant operating procedures provide adequate information to prevent accidental manual overloading of startup transformer #2?

Response: Our current procedures address reanual loading of the startup transformers under certain conditions. We are currently reviewing those procedures for their adequacy and will revise then as appropriate slruld our review dete_mine they are inadequate.

Very trul yours, 4

,. / v/ . ' gd u?

W d A. Rueter DAR:JTE:nak Attachments 4

a n. w .

_lWTI AL CONDITIONS FOR VOLTAGE STUDY

1. AUTO TRANSFORMER IS OUT

2. TIE EETWEEN 500 KV AfD 161 KV SYSTEMS IS OUT

3. 161 KV SYSTEM IS If1 TACT

4. MILLSTONE MODIFICATI0flS ON ANO-1 ARE COMPLETE

5. FAST TRANSFER TO ST 1/ST 3 IS NOT SUCCESSFUL

6. MINIMUM VOLTAGE ON 161 KV SYSTEM OF 1 P.U.

7. MINIMUM ACCEPTABLE VOLTAGE AT MOTOR TERMINALS RUNNING - 90% (MOTOR BASE)

STARTING - 8f.l (MOTOR BASE)

8. INTERLOCKS INSTALLED TO KEEP BOTH UNITS FROM ACCESSING ST 2 AUTOMATICALLY

a C;0EIT II CONSERVATISM

1. ASSlFED AtJTO TRAtJSFORMER REf0VED

2. PATm H.P. VICE OPERATING H.P.

3. USED HIGHER THAN MEASURED LOADS Ori 480 V. SYSTEM

4. USED ARITH 4 ETIC SlJi VICE VECTORIAL SUM FOR 480 V. SYSTEl1.

. f  :. .JL II VOLTAGE CALCULATIOf4S COMPUTER ANALYSIS BECHTEL PRCGRAM FCR DATA COINERSION #4D COMPILATICil BECHTEL, GE, NO PHIL. ELEC. CO. POWER FLOW PROGRAM FOR PROBLEM SOLUTION RESULTS #4ALYZED, EVALUATED NO QAD

ATTAC1cmIT IV MINIMUM ACCEPTABLE VOLTAGES ON BUSSES SYSTEM t'OTOR RUNNING STARTING BASE LOAD LOAD 6.9 Kv eus 6.6 Kv 0.91 P.u. 0.82 P.U.

4.16 xv Bus 4.0 Kv 0.91 P.U. 0.82 P.U.

430 v Bus 460 v 0.92 P.U. 0.86P.U.

I

an sa EUS v0LTAGES (MOTOR PASE) m0-1 6900v .ALSO v ul60 v 480v 480v FULL HOUSE - S.S. 1.032 1.006 1.006 1.009 1.009 (NO ES)

ES T=5 1.028 0.977 0.977 0.877 0.919 T = 10 1.028 0.978 0.978 0.917 0.930 T = 15 1.031 1.000 1.000 0.941 0.954 T = 20 1.029 0.9828 0.9828 0.927 0.940 T = s.s. 1.031 1.000 1.000 0.945 0.962

ATTACHMENT VI BUS VOLTAGES (MOTOR BASE)

_Au0 - 2 6900v 4160 v 4160 v 480 v 480v FULL FOUSE - S. S.

(NO ES) 0.972 0.965 0.%5 0.926 0.926 ES T=0 0.998 1.011 1.011 0.929 0.929 T = 10 0.992 0.951 0.951 0.918 0.918 T = 15 0.993 0.959 0.956 0.928 0.926 T = 25 0.992 0.953 0.953 0.908 0.903 T = 50 0.993 0.993 0.993 0.904 0.904 T = 70 0.996 0.998 0.995 0.930 0.906 T = 80 0.996 1.000 1.000 0.959 0.937 T = 90 0.993 0.948 0.91 0.897 0.929 T = s.S. 0.996 1.00 1.003 0.958 0.957

ATTACliMENT VII I ?: l.. -

aLU SU2

, p ps cq-) )Y  !

, J

'w i

G ,9 K V 4.l G K V I I I b (

'! '1 1 1 '1 [> 1 [1

13. 23 13 '

23 ill Eli Ill 2 11 9

1 c el l c l l l c l HI H2 2HI 2H2 AI A2 2A l 2A2 UNIT I UNIT 2 UNIT I UNIT 2

I A P l .2 A F I t1.( . CON TA C T .E IN S E RIES WITH

--_ I l

l C LC S E AtJ l C MA l lC TRANSFER LEG OF EACH Hg Hg A% A2f ERCAKFR I N UtilT TW0-

, i l /. R M '

> /. P AP r~ ~N

--~ -

(IA A Pi t '_t.11 T I - S II.I I L A I- F cc r; p Ut1iT I U f. I T 2

A I

> 6 >

C e

2 5

U N

k e

3 5 e i M a e

=

i

~

9

A TACH!E.*;T IX r . r- 4 Tl

) l b

"I Arkansas Power & Light Generation & Construction I

I I 2 . . _ _ _

$o of 4'000 V LD A.b]Po C C R .F AC.70 R. . _ .--. - N _ - - - - -

• N WN#U b bECRE456. i --_. - - - - . ---

B tts \

. _ [._ _ _

90s, j '

j k N i O & 47.0 %

I

_ _ _ . , g _ _ _ _ _ _ .__ .- .

g 7, . - - i N 4 + 4 7 5'd 7 '

s '

^( s

. _ . ~ . - . _ _

g ") . . _ . . . . _ . _ . - - . - . _ y _ N . . - - - - - - - - - - -

g i r,  % . I q(, .9 7/ moq n) **%.$, . _ . - - - - - . . .

1. o gg . - . . . . - . .. - L W 0 __ Lo A b _. Po e & RfAc top g* r ue R t A S L- . . _ ,

'l _

' ~ ~

o + *15" . 3 o 9 .. ,

gg, 44, O __ _.

A 44/. rs'9 - - - - -

qqg o + 94.e7/e

~~~~ ~

9 3. z t,4 s o ,

939, - _

a -.. ..9 --_ 3. Il-&_. _ -. . . UOL.TA G G s s new n A x t. TH C %.AE.-.Mp_ce

• ~ O' 0 0 A?SLE SSA R V A f" T H E t//too o B u 5 To .. _ _ _1 At A INrA tav 9 0e 0 -f 'llo O J 6 N . T t+ G. .

490 V B LL S YoR LO A b (NG 40 & pt T!O NS... l AS S ho W M - i l

JJf,

--_.---.4 O + RI b4 . . . _ _ .

I gj p, . _. _ _ _ _ _ _ _

O at(7, 307o 75?e M7o .

i

ATTI C C TT X RD-1 FULL IDUSE TRMEFER FOLIO.TD BY ES SIGAL TDE (SEC) VOLTAGES GJ BUSSES 6900 4160FS 4160 10N-ES 480ES 480ES 480 I m -ES T= 0 (S . S . ) 1.0298 0.9963 0.9963 0.9159 0.9404 0.9350 T=5 1.0328 0.9732 0.9732 0.8745 0.9168 0.9099 T=10 1.0327 0.9742 0.9742 0.9138 0.9262 0.9110 T=20 1.0320 0.9790 0.9790 0.9231 0.9356 0.9161 T=S.S. 1.0300 0.9940 0.9940 0.9385 0.9555 0.9323

,