ML17207A771

Forwards Best Estimate Main Steam Line Break Analysis to Assess NSSS & Containment Response W/Automatic Auxiliary Feedwater Actuation,In Response to NRC 791221 Ltr

ML17207A771
Person / Time
Site:	Saint Lucie
Issue date:	01/24/1980
From:	Robert E. Uhrig FLORIDA POWER & LIGHT CO.
To:	Reid R Office of Nuclear Reactor Regulation
References
L-79-36, NUDOCS 8001310294
Download: ML17207A771 (42)

Text

REGULA I DRY IN'MATION DISTRIBUTION SYST (RIDS)

ACCESSION NBR!8001310294 'OC,DATE: 80/01/24 NOfARIZEO: NO DOCKET FACIE:50-335 St. Luc.)e Planti Uriit 1r F'lor ide Power Light 05000335 AO'fHsNAHE 'Ul'HOA AFFILTA'l'IOA 4 Co ~

UHH/t IN'D Florida Power 8 Light Co,.

HECIP",NAME AECIPIEAT." A'FF ELIATION RE Ibid s W ~ Operat'ing Reactors Branch 4 SUBJECT! Forwards best estimate main steam line break analysis to.

assess NSS8 8 containment'esponse'w/automatic auxiliary feedwater actuationiin 'response to NRL'91221 ltr.

oisrsisuvior>> coos: ao<<ss copiss sscsivso:cps > sscc > sizz:

TIft.t: Resp to t.esson Learn fast For ce Comb Eng R 50 I ~ I>> ~ 0 ~ 8 267

~ ~

NQ T O'r ES8 ~s wweeeemee~esweemeeee~wweeeawerwme E N ea~eeeewyaomw~eawee~mmoeweem~eoeeeeaomeee eeeseeeew~wmwmmmeees<<r<<w RECIPIENT COPIES RECIPIENT COPIES 10 CUD'/NAME l:lfTN ENCL ID CUOE/NAME L r YA"EACL ACT ION! 8 "8C

'~cf INTERNAL: 1 . L,-. 1 1 15 I LE 2 2 i7 A/EUU i i i8 CviiE PERP BR i 19 BAG &R '

.i 2 NAC PDR 1 20 Ak,AC'SFTY BR i 21 f CAAT- SYS BR i i 22 EEB" i i 2S &FLY TR L>> SY8 i i 3 LFDA 1 1 Nb 1 i i 5 C AELSON 2 2 6 C 'A'ADERSON i i 7 C CiRACYHa i i S EMSHO i i G IMBRO"" i i J ~ l' TELFORD 2 UELD i 0 EXl'ERNAL: 24 ACRS lb lb y S<$ 0

'l'OTAL NUMBER OF COPIES REQUIRED! Ll TR 45 ENCL

>> ~,

l C

C a ~

II P

II J W I H

~ II JC4 8

h II

P BOX 529100, MIAMI, FL 33162 FLORIDA POWER 4 LIGHT COMPANY January 24, 1980 L-79-36 Office of Nuclear Reactor Regulation Attention: Mr. R. W. Reid, Chief Operating Reactors Branch 84 Division of Operating Reactors U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Dear Mr. Reid:

Re: St. Lucie Uni t 1 Docket No. 50-335 Auxi liar Feedwater S stems The attached information is submitted in response to your letter of December 21, 1979 on the subject of auxiliary feedwater systems at St.

Lucie Unit l.

Please call if you have further questions on this subject.

Very truly yours, Robert E. Uhrig Vice President Advanced Systems 8 Technology REU/MAS/cph Attachments (2) cc: Mr, J. P. O'Reilly, Region II Harold Reis, Esquire 8001 810 ~~/

PEOPLE... SERVING PEOPLE

ATTACHYNNT Re: St. Lucie Unit Docket No. 50-335 l

Auxiliar Peedwater Systems BEST ESTItSTE t>SLB l'HALYSIS TO ASSESS HSSS MD COHTAIHHEttT RESPOi'ISE !IITH AUTOS'IATIC AUXILIMY FEED! STER ACTUATIOih

1.0 IWTRODUCTIOW A set of calculations has been performed on a generic basis with plant characteristics representative of CE operating plants to model containment building pressure and temperature response and overall WSSS behavior.

including core reactivity, following a Hain Steam Line Break (tiSLB) inside containment. The intent of these calculations is to determine if the containment building response (pressure) and the core reactivity response (return to power) are acceptable following a HSLB when auxiliary feed-water is added without regard to the identification of the affected steam generator. The auxiliary feedwater flow is assumed to be activated at the initiation'f the transient to maximize its effects. Hain feedwater flow including post trip rampdown is simulated. Wo isolation of main or, auxiliary feedwater is considered unless a high water level condition is reached.

2.0 ASSUHPTIOWS AWD CASES Assunptions for the analyses are given in Table 1. The four cases analyzed are listed in Table 2.

3.0 DISCUSS IOW OF RESULTS Haximum containment pressure and least negative core reactivity for the four cases are listed in Table 3. Both the containment pressure and the reactivity (return to power) values are within 'acceptable limits.

Hain feedwater flow, auxiliary feedwater flow, core reactivity change, core power, containment'pressure, primary loop temperatures, and steam generator secondary temperatures for the four cases are detailed in Figures A-1 through A-7, B-l through B-7, C-1 through C-7, and D-1 through D-7, respectively.

The results of the analyses using best estimate models for steam generator moisture carryover and containment passive heat sink heat transfer demonstrate that the additional auxiliarv feedwater has a negligible

'impact on containment peak pressure. The containment peak pressure is determined primarily by the initial inventory in the ruptured unit- This

inventory is released within the first few minutes, depending .upon the break size, so that the contribution of auxiliary feedwater flow to the ruptured unit over this time frame is small. Over the lonqer tim frame, the secondarv inventorv is boiled off at essentiallv the decay heat rate which the containment active heat removal'vstems can accommodate while reducing containment pressure. Th'e excess,feedwater which is not boiled off remains in the steam generator, causing the secondary level to rise.

The containment peak pressure is essentially an initial inventory limited phenomenon.

The results of the analyses also show that the additional auxiliary feed-water has a negligible impact on core reactivitv. Cases h and C assume no stuck rods and a best estimate moderator cooldown curve. For comparison, Cases B,and D assume that the most reactive rod is stuck and that the

-moderator cooldown curve is a licensing curve. All case took credit for boron injection via three charging pumps; however, safety injection boron credit was not taken. These cases do not have a return to power for the following reason. The initial primary loop temperature decreases are linited by the two-phase blowdown process associated with large break P'2 ft),

2 since much of the break flow is saturated liquid which has not absorbed significant amounts of energy from the primary loop. For smaller break areas ((2 ft ), the blowdown is pure steam which does require large amounts of energy per unit mass to boil via primary to secondary heat transfer; however, the rate of primary-to-secondary heat transfer is controlled by the blowdown flowrate which in turn is limited by the small break area. The net result is that over. approximately the first 100 seconds of the event, the amount of core and loop cooldown is about the same regardless of break size. This time frame is most important since .the presence of delayed "

=neutrons minimizes the amount of cooldown needed to produce a core criticality problem.

without a return to power (via primary loop cooldown and delayed neutrons),

the remainder of the .transient is a gradual increase in reactivity <<9 <<

. loop cooldown which is coupled to the containment pressure, plus a decrease in reactivitv due to boron injection. In time (approximatelv 300 second ),

the reactivitv decrease due to boration overtakes the reactlv'Itv increases due to loop cooldown; thereafter, the total reactivitv steadil<<<<<<>>es and "" th The ruptured steam generator is at the containment backpress<<e

RCps 0

operating the sensible heat from the non-ruptured unit is quickly removed resulting in RCS and SG secondary temperatures essentially in equilibrium with the containment conditions in about.10 minutes.

With licensing assumptions, the peak in the reactivity transient is calculated to be within the first two minutes of the event. A two minute time delay, if added to the automatic actuation circuit, would justify a statement that automatic auxiliarv feedwater actuation will not impact existing SAR core cooldown HSLB analyses.'.0 COMPARISON 1lITH LICEHSItlh CALCULATIOllS The following items are important in comparing. the results contained herein with those'obtained with traditional licensing models and assumptions.

1. The moisture carryover model used is a best estimate model which gives a two-phase blowdown for large break areas. The two-phase blowdown-results in a lower containment pressure and less initial primary loop cooldown than a pure steam blowdown. Chapter 15 analyses assume a pure steam blowdown regardless of break size.

. 2. Chapter 15 analyses assume that the most reactive rod is stuck.

tloreover, the remaining rod worth is assigned a conservative value in conjunction with a conservative moderator cooldown curve.

3. A best estimate containment heat transfer model provides containment pressurization results significantly lower than those provided in Chapter 6 analyses.

ASSUNPTIOllS t<SSS Ini ti al Conditions Power 2700 H';lt Core Inl.et Temperature 548'f Primary Pressure 2250 PSIA Secondary Pressure 875 PSIA Secondary Temperature 529'F Containment Data CESAR Free Volume 2.5 x 10 ft Design Pressure 44 psig Heat Sinks values Heat Transfer Hodel Best estimate model Number of Fan Coolers 4 (no single failure) 6 Fan Cooler Capacity, each 68 x 10 B/hr at 280 F containment temperature 100'F CCH Temperature Fan Cooler Actuation Setpoint Fans are operational 9 t= 0 tlumber of Sprays 2 (no single failure)

Spray rate, each 2700 GPf1 Spray Actuation Setpoint 10 PSIG + 60 seconds Other Data Steam Generator Isolation Signal (t<SIS) setpoint 500 psia Decay Heat Curve AHS-5 Hain Feedwater Flow Ruptured Unit: Pamped to 10'.l over 60 seconds following Reactor !rip: (10,.

represents twice the bypass nominal value or 5':, this accounts for purp run-out wi" reduced backpressure),

temperature is r=duc=d to lo" to account for turbine off-Flow terminated

'vel if the elevation of upper tao.

is reached. See Figures A-l, B-l, C-l, and D-l.

'BLE 1 continued Hain Feedwater Flow continued Unaffected Unit: Same as ruptured unit except that flow is ramped to 5~. See Figures A-l, B-l, C-1 and O-l.'

Auxiliary Feedwater Flow Ruptured Unit: Initiated at t = 0.. Flow rate is a function of unit pressure. All control valves assumed to be fully opened.

Unaffected Unit: Wo flow; all flow i,s totally diverted to the ruptured unit.

Reactor Coolant Pumps Operating during the transient.

CEA Insertion Worth All rods in (API) -8.9Ã (no stuck rod) ttost reactive rod stuck -7.12~ (best estimate) t'1oderator Worth SAR Yalue See Figure 1 Best Estimate Yalue See Figure 2

. Doppler 'Worth See Figure 3 Noisture Carryover On Steam Generator Secondary Side Best Estimate Hodel Boron Injection Parameters Safety Injection Credit !1ot Taken Charging Pumps f(umber of Pumps 3 Flow Pate 44 GP!1 per pump Actuation Time SIAS Boric Acid Concentration 8Ã bv weight Boron llorth 00 PP!1/"

Boric Acid Conversion Factor 1709 PP!1 boron/;l by weight boric acid Hixing Model Used Slug Flow l1odel Loop Transi" Time 10.5 seconds

TABLE 2 CASES Case CEA Scram worth ., ttoderator Curve Break Area Ft 2

-8.9 Figure 2 6.63

-7.12 Figure 1 6.63

-0. 9 Figure 2 1.99(2)

D -7.12 Figure 1 (1) Double-ended severance of main steam line (trio-phase blovIdovin).

(2) Largest break area corresponding to pure steam bio@down.

~ ~

f ~ t VP

~ ~

~ i%I A 0 4 ~ )'I ~ t~ ~ f yt

4

'TABLE 3 RESULTS 1east'f/egative Case Peak Pressure (PSIh) Core Reactivitv" '"'ontainnent 29.7/83.0 (sec.) -0.31 29.7/83.0 (sec.) '2.34 35.0/231.9 (sec.) -3.54 (sec.) '5.0/231.9

<<1.55

~ V

. ~ ~ (

1

~is FIGURE t

,REACTIVITY VS f'ODEfQTOR TEtlPERATURE 0

(SW, VnLUE)

Q.

~o Q

V-

. C/7 K,

300 350 400 450 . 500 5'- ilk'll y-'

)uV Ill'-t~>

~n n~Z I -I ~

r

~

-~:

a ih ~

i~"

~~

t Olla

<< ~ ~ ~

FIhuPE 2 PEACTI YITY VS tiODEPATOP. TEt(PEfMTUPE e

(OEST ESTI!!W E VaLuE)

~ )

Il<<L

~

g r CL.

f

<<'0O 35 0 coo neo 55 0

~ ~Qf) <<t g ~ ~

0) p) 1W ) l I I ol u

O L)Q))t 1 I L' l I I ~ t ~ I Lese ~~ Ltll+)

FIG'JKy

~

) 1.0 DOPPLER ROiCTIVITY VS F UEL TE.~PERaTURE 1.6

~

T

~ -. 12 ~ I 1.0 ~ ~

I I ~

.- 0.8 T

~ I 0.6 q

0.4 0.2 -,.

0.0 500 1000 1500 2000 2500 T~

~ ~ ~ I I '

~

-0.2- 'I ~

~ ~ ~ I T

-0.4 ~ ~

~ ~

~ ~

-0.6 ~

I

~ t.

I ~ ~

'-<<0 0

'I I

-1.0 FUEL TEtlPEMTURE

'F

~ ~

1800 C3 L'J FIGURE A-1 V3 140" )NIt( FEEOllATER FLO>l VS TIllE 1 2QG Cx I~~i C:

n

~t

~

ta .10GC 8+1 fl 600 COG 200 AFFECTEO UilIT Ut(AFFECTEO UtlIT 1

P 0 200 4GG 6CG BGG T I h:.

360.

FIGURE A-2 320 ErKRGErlcY FEED;NTEp, FLotl vs TIr',E HO FLOtl TO UfNFFECTED UfrIT 280 UJ (Q

CO 240 l- 200

~r 160 120 80 40 0

0 200 > 00 . 6GG 800 'GGC r"G" T>ixE l SE.C )

F I CiURE. A-3 REACTIVITY CHA!lhES VS.

TItlE

!<OOERATOR DOPPLER OOROr>

TOTAL CEA 200 . 700 600 'GOO '. 2C' TIt'lE (SEC)

o.g FIGURE A-4 0.8 0 COPE POHEP. VS TIffE o.7 0 o.6 0 0 ~rp o.4 0 o.3 0 0.1 0 o.n 0 0 200 400 600 8r.r TINE (Si C )

FIGURE A-5 COHTAIHt1EffT PPESSUPE VS TIflE 5G 40 30

,25 20 15 10 0 200 400 6GC 8GG 'GCC TII'lF. (SEC)

600.

FICiUPiE A-6 I

PPItNPY LOOP TEl1PEPATURES 540 VS

, TIt'lE COLD LEG OF UfNFFECTED Ut( IT 420 LIOT LEG t:) 360

.M C3 r

'300 COLD LECi OF AFFECTED UNIT 2.10 r'80 120 0

0 200 400 't' 600 BOG wt- ~ <:r. C'

FIGUPE R-7 540 STEAl1 GEllERATOR TEl1PERATURES VS TI!1E 480 420 UNAFFECTED UflIT 300 AFFECTED u>tIT 240 180 120 0 200 .400 600 800 T I '1E ' E'

)

Ph AW(V

~ V 'y ~ ~ '4

1800 16GO

~ e LJ FIGURE 8 -1 (D

140C tNIH FEEDilATER FLOH YS TItiE C3 1200 CL C3 0

lOGG 8 f1 fl 2 0Q AFFECTED UilIT UNAFFECTED Ut'IT 0 200 400 6GG

360 0

FIGURE 8-2 320 Et1ERGEttCY FEE01IRTEP,'LOll YS TIt1E HO FLOll TO U!NFFECTED 280 Ui"tIT 240 200 160 120 80 0

0 200 400 'GG 8GO iGOO 1'Il'LE l SE.C )

Fl()UPE 0-3 REACT IV ITY CklhflGES VS Tlt1E t IODERATOR DOPPLER TOTAL TOTAL BORON CEA 200 400'00 T INE ('SEC j J

800 1000

\I I

I Fit.u~E ~-4 o.90 COP,E Pot(EPi VS TI!1E;

o. GO o.7 0 0.6 Q

0. r0

~-

0 QQ C) 0.3Q 0 20 O.]0 o-,o 0 0 200 ~i 00 600 T I t1F. ( SEC J

FIGURE 0-5 55 COf'ITAIHf1EllT PRESSUPE-VS T I11E, 40 35 30 ~

25 20 10 >GQQ 0 200 400 GGG 80G T I f'lE ( SEC )

'l

~ C

~ ~ t ft

FIGURE 8-6 540 P(IttARY LOOP TEl1PERATURES

'.VS

, TIt1E 48G COLD LEti OF UMFFECTED Utt IT 420 HOT LECi 360 300 COLD LEG OF AFFECTED UtiIT>~

LU 2.40 18G 120 0 I 0 200 400 600r 800 C~~p hM 7 P hey g

~ 1 FIGURE 8-7 540 STEAfl GEHERATOP. TEtlPEPATUPES VS TItlE.

480 420 UtNFFECTED Utl IT 360 300 AFFECTED UtlIT 240.

180 120 0

0 200 400 600 800 !000 TI)IE lGKC)

180G FIGurE C i tNIW FEEPlATEr, FLO';l ~S TIlfE 1C00 C3 1200 1000 Q

CC C3 I~ 800 M

U 600 400 AFFECTED UtlIT Ul'lRFFECTED UtlIT 0

200 400 I=.

6GC BGO I

'. COG TinE tsLC

FIGURE C-2 320 EaarnnraanM rrrne aq~Lp FLpll VS TThlc 280 HO FLP)l TO UtlAFFECTED UtlIT UJ (0

CO 210 C)

U 200 i'

C3 160 UJ UJ X"

UJ 120 80 40 0

0 200 400 6GG 80u T>VV (SEC'

0 FIr'APE C-3 REACTIYITY CfIAtf"ES VS TIf)E HODEPATOR DOPPLEP.

OOROn TOTAL CEA J

200 400 600 BOG 'OGG T I i'lE l SFC )

FIfiURE C-4 o.90 CORE PollEA YS.

'TIflE o .00 o.70 o.60 o.s 0 Q

M Q

C7 O.C o.30 o.20 o.>0 o.o0 0 200 400 600 8GQ 1 000 Tlt<E (,SEC)

FIGURE C-5

~y COllTAIfttlEttT PRESSURE YS TI/1E x

40 30 20 10 L 0 200 400 GCG 80G i nor g

C.vv T I NE ( St=C )

FIGUP,E C-6 PPItSPY LOOP TE<lPEPRTUPES VS

. TIt>E

~y 480 COLD LEG OF UtNFFECTED Uil IT ls ttOT LEg o

~s 360 C3 300 COLD LEG OF AFFECTED UIIIT ~

240 180 120 60 0

0 200 400 . 609 800 '0"0 T I I'iF. ( SF.L )

FIGURE C -7 STEAt) GEttERATOR TE>)PERRTURES VS.

i . TIt)E 420 Cb UtNFFECTED UttIT 360 300 LLI AFFECTED U)JIT-CL C3 I

2~'0 QJ LLt 180 120 60 0

0 200 cOO 600 8GG !OQG T I YiE < SE.C )

FIt'iURE D-l 1800 fSIN FEED'llATER FLOll VS TIt1E 16CG UJ (A

1200

~r u 1000 0

~0 CC C3 LU

.900 U

40 200 AFFECTED UllIT UNAFFECTED Ui'l IT 0 L 0 200 400 6GD QGO TINE (Sf C j .

Fr%PC D-"

Ef'IEPGEWCY FEEDHATEP, FLO!J VS TItK HO FLOtl TO 280 VI(AFFECTED UlJIT L)

M lD CQ n,I 0 200 C3 M

0 160 QJ 120 80 40 0

0 200 400 6GC 800 T IHE ( SLC )

FIt;UVE D-3 REACTIYITY CIWtrES VS TIt'lE r<OOEV.STOP

~ ~

DOPPLER TOTAL TOTAL BOROtt CEA 200 ~00 600 800 1000 12"0 TI lE ( SEC.)

',, l'h

o.90 FI(iURE 0-4 CORK POWER YS TIf/E 0.70 0.6Q

~f 0.5Q UJ 0.40 n

L) o.30 0.20 o.lg o.oQ iCGG 120r 0 200 400 600 8GQ T I f'IE ( SEC )

FiturE o-S CONTR I ti't1EtlT PRESSurE VS TItFi 40 25 20 15 10 0 400 . GGG 8GC Tlt-1E (5" C)

4

~ l FIGUPE D-6 540 'PRItQRY LOOP TEt1PERATURES VS i TIt/E 480 COLD LEG OF UtNFFECTED Uf1 IT 420 U flOT LE~G o

~s C3 (Q

LU COLD LEG OF 300 AFFECTED UHIT CC 0

M Q

O~

240 r'80 CL C)

C3 I20 h

(

0 0 200 400 600 80G 1 QQQ TI Yi E ( 5 F. C )

UUU FIGURE D-7 540 STEN1 GE!(EPATOR TE! IPERATUPES YS TIl/E 420 C.')

U."lAFFECTED Utl IT C3 360 CC Q

300 AFFECTED 4J I UtlIT C3 l

CC LU 2" 0 LLl (3

O:

180 CO 120 0

0 20G 400 , GCC 8CG !0CG 4V w T ICE f Sf'..C )