ML20085A478

Forwards Draft Repts on Small Break Scenarios to Be Used in Small Break Cooldown Procedure.Comments Requested. Descriptions of RCS Leaks W/Auxiliary Feedwater & W/O Feedwater & Small Breaks in Pressurizer Encl

ML20085A478
Person / Time
Site:	Davis Besse, Three Mile Island
Issue date:	05/02/1979
From:	Rosalyn Jones BABCOCK & WILCOX CO.
To:	Kane E BABCOCK & WILCOX CO.
References
TASK-03, TASK-07, TASK-3, TASK-7, TASK-GB GPU-0397, GPU-397, NUDOCS 8307060521
Download: ML20085A478 (13)

Text

- _ _-_______ _

4

. S i THE SAS'C0CK & alLCOX COMPANY ((6[Emli377f0310tN). I f PO'aER GENERATION GROUP g/ 7/p/ ig, g, hgji ,

To l l' '/~

[ 'L '

E.R. K.AKT., LICENSING {

From

• • • • • • 8 R.C. JN. ECCS .GA1.YSIS (2066) d3( ,

File no.

Cu st. f or Ref. ,

P

' Date -

Subj. ,'

4

,' SMMJ. mAK SCENARIOS  ?'.AT 2.1979

..-w  %

gn. ,

3 Attached are draft writeups on small break scenarios to be used in the l small break cooldown procedure. You are requested to cocument on these writeups and place them in a form suitable for the procedure. The en- N 2

closures are in three parts:

1. RCS leaks (non-FZR) with auxiliary feedvater.

2. P.CS leaks (non-PZR) without auxiliary feedvar er.

3. Smil breaka in pressuriser.

A 1

If you have any questions on these writeups, call either R.C. Jones (X-2066). R.J. Sala (X-2600), or R.m Dunn (X-2138).

.';i 1

RCJ/lc cc E.A. Vomac's 4 i B.M. Dunn R.J. Salm D.F. Hallman N.S. Elliott l

i i

I h  ;

.,g*. r' g

) p ,- [.-

UIj$ kNb5;5 g i l

l l  :

! i 8307060521 790502-PDR ADOCK 05000289 R HDL

(

i S .

.- 3.

m --

. .) c; . -- 7 a.' o . o >y. .

L'

~

i 0120 j il3 J- ' g s ,' ? w (, 3 ,' , 5 . - ~ .

l 4

. wh -

t i

i i DISCRIFTION OF Sv.U L EZI.U: TRANSIr;T BEHAVIOR

' i 1 ,

y The response of the prisary syste= to a s all breat v1.ll di".~ar great.ly ,

• L I depending on the break size, its location in the systen, operation of the [

$  ?-

? reactor coolant pumps, su=her of ECCS syste=s functioning, and availability of (

t~.1...

secondary side cooling. Figures 1 ar.d 2, plots of RCS pressura and pressurizar y* '

w.-

level histories for various combination of parameters, indicate the vide range "gr r.

of behavior. -

L r h

U CASES VITH AIDCTI.IART TEEDUATER a -

. N i Curves 1 and 2 of Figure 1 show the behsvior.of F.CS pressure to breaks that are large enough in combination with the ECCS to depressurize 3,

the systen to a stable low pressure. ECCS injection easily exceeds core boil-off. Curves 1 and 2 ef Figure 2 show the pressuriser level transier.t. Rapidly

'~

falling pressure causes the het legs to quickly saturate. C 'd les temperature reaches saturation sonevhat later as RC punps coastdown or the RCS depressurizes f.

1 J. '

belov the secondary side saturation pressure. Since these breaks are capable h, t .

of depressurizing t!.e RCS without aid of the stean generators, they are largely insensitive to the availebility of auxiliary feedvster. Operation of the re-

c. t actor coolant pumps also plays little role in the course of events. Other than T*

verifying that all ESTAS actions have been completed. *he entrator needw to do nothing to bring the systen to a safe stable coadition.

Curve 3 of Figure 1 shows the pressure transient for a break which is

.)

too s=all in combination with the operating HFI to depressurite the RCS. The I

steam generators are being relied upon to remove a portion of core decay heat.

If the reactor coolant pu=ps are not operating, and the pressure has stabilized f.re*-=~'MMq*

- . .. ,.t.t 4

1 S T

-- -3.

0 1 2 O ol

< a

f. Q g.. ,2 ',;3, 6. [ ,

f i; Q ;; oo T h*

" ~

.. -r 7 7 .~. __ _ .

l' . .

I, I

near the seco dary side pressure, RCS pressure cay evesta. ally bes;in falling j again as the decay heat level decreases. If the RC pu=ps are operating, pressure j

4 1

nay, or may not decrease, it could eve =n 21 ty increase to sc=e stable level as h-s the E?I refill and repress =rize the 2CS. The assu=ption for this case is that i

,- r

~j secondary cooling is ~ainemined. Curre 3 of Figure 2 shows pressurizer level t 2 [-

Q W behavior. Curve 6 of Figure 2 shmrs refilling by the EPI. The hot leg tempers- h}.

?1 g' ture quickly falls to the saturated te=perature of the secondary side and controls v j_

] primary systen pressure at s.aturation. The cold leg f:emperature remains slightly 1.

subcooled. If the EPI refill and repressurize the RCS, c' s hot legs can once

= ore become subcooled. The operator needs only to verify ESyAS actions and, if

}0 RC punps have not failed, lexve one ru= sing in each loop.

e i

t 2

Curve 4 of Figure 1 sbcvs the be'.avior of a small break in which the te e r actor coolant purrps have been lost and the break is too s=all in combination  ;

.} with the EP1 available to depressuri=e the pri=sry syste z. Although auxiliary feedwater is available, loss of primary sys.te= coolant eventually leads to in-T ..

[

• terruption of circulation around the loop. This is followed by a gradual re-

pressurization of the primary systen. Although not likely, it is conceivable 2 2 '

that the pri=ary systen could repressurize as high as the pressurizer safety be valvss before the pressure stabi1*ses. This is shown by the dashed line in Figure 4 Once enough inventory has been lost from the primary system to allow >

1- ,

direct stvas condensation 1.s the r6gion of the secas generators adjacent to the secondary side coolant, t':e steam condensation forces a depressurizarfon of E

, the pri=ary systers down to the saturation pressure of the secoc.iary side.

l'l l

Since the cooling capabilities of the secondary side are =eeded to remove n.

! decay heat, pressure vill not fall below that on the secondary side. HPI is sufficient to exceed boil-off in the core, andcondensation in the steam generators -

renoves decay heat energy frc- the systes. The reactor. coolant system is in a ,

,i p......,.,,,,

2 '

25 .. , .. .h. h. s .lasi.f. 8

';.4.-

l .- .--  ; -

y-5

' ' , ' h. _ _

u .n . .- - -

c '

'O' '_Q's 'jOF'o' 1

gg , .

.- 012 0 k

j k

-_ - _ _. -- - . ~ . . . -. - _ . . -

- h 4

3. .

l stable condition and it util re-uf n there until the operator takes further i

q action. The pressurizer level transient is characterized by Curve 3 of Figure l

2 during the depressurf r.atiei. sed Curve 4 of Figure 2 dttri

y, the re~cra.y repre.ssurization phase. The dashed line indicates the icvel behavior if pressure

is forced up to the pressurizer safety valve setpoint. During this transient, w

p m

bot leg temperature vill rapidly approach saturation with the initial system W

9 depressurization and it vil.1 remain saturated during the vbole transient. Cold

) $

les temperature vill approach saturation as circulation is lost, but may remain slightly subcooled during the repressurization phase of the transient. Once i

direct steam condensation develops in the steam generator, ROS depressurization a

k vill cause the cold les ta=peratures to quickly reach saturation. Cold les f temperatures may once more subcool slightly once the primary systen has stabilized at secondary side pressure. Subsequent filling of the pri=ary system by the EFI may cause temporary icterruption of steam condensation in the stean generator

, as the primary side level rises above the secondary side level. If the de-

}

pressurizatiou capability of the break and the 3FI is insufficient to offset decay heat, the prir.ary systen vill once more repressurize until enough RCS i

coolant is lost to allow direct steam condensation in the steam generator. At

, this point the primary system will once again dep tessurize to secondary side 1

preasure. This cyclic behavior will stop once the HF; and break can balance 1

decay heat or the operator takes some a. tion.

]

! Curve 5 of Figure 1 shows the behavior of RCS pressure to a break in which RC ptraps are lost, but v'-ich don not lesd to intarruption of natural circula-tion. The high pressure injection is available and exceeds the leak flow before

/~. the pressurizer has e=ptied. The primary systen es=ains subcooled and natural circulation to the steam generctor removes core decay heat. As Curve 5 of Tigure 2 shows, the pressurizer never er.pties and continues to control primary system pressure.

!.q.;;3....;.

i .. ...

....,t s

-+ -

-  %.=. b

. Hv,.g2?D i o12o' # M..h-B .

1 4 )

I . _ _- - _

k

' - . .g OZIO 9:E. E' T4_ Ell ,-

i 2 (4r....

rI.n. b.rs-. .n e

__ g ,_ f'.?d . - -- - --

P i

I I

r

.q e i

i .

I

<- Jk  !,

xs t

& Y

% /

3 -

.,.. m - g

. . s I  !

lt  :

A I i

's l ,

3 I u ,

e s.

W h '

lN E

i l

3 g N

\

j l

, t L3

.g ,

A =

xy

, y \ - - -

s4 '

s k  !!

u, , ,,)4 '

.. 2 i

Vq - s - - - -

a I y s ~

• 4 O

~

l ..; .

,_ ~,

l

.l} s, i

• . 7.-

'd @ E Q + _

8 %

c 6 s% >

6

~

t - - . _,_C , , t v  !

I A P e s - -

4 4 $ S $2 6

,, c/ ' .v. . - .vg ...-...--

l

v> t

.B n-y (n

- . . ..-  ; o..4.C.,I

.e O Z T O__1 1

[.P..?>'ed,

.. . r.- r- -- Ell! -

C ..- .

. 1

$, l

-)} J. *. '\ c :

h 'l I .a s 3. = b 4 -

a-:. " Ci

• ~' f~ I. .I .'

h ed a e 3 e

1

I I e

, 3 l-t j

• 1 i

k _- ._ - -- -- -

t-- -4 2 3 g I I I

y Qt l S

1 y

(

C

i. ;

\

3 x ' -

G _ w b= 3 -

N . .- .

.t e [

a

\ s . .x s I i

d 1 -

N l'

. vS .

\

1 1

4 .

(? -

.s......  : _

g j

<4

,.N .. ..

.. s . .

$ - S~

3 i N . .

' ~

(

c.4

~ \ ,

.A N . O l

m' 3m

'Q1

.1 Q .

• .O I N, l

%)

l l . b .

f

.-; , , , _. e I ,I

• e. e

'~ -

C k g w + @ O

/ u'r7 e,eryn: n 7 g i

1 .

. i

_m....r,.. . ~ , ~ . - - _ ..

,m _ _ - - - - - - ,

3 SAI.L 375.AKS LTmot r ATI.* C r u ATOt 5 There are three basic c. lasses of break respense for small breaks without

.A.

9

> auxiliary feedvater. These are:

1 l  :

1. Those breaks capable of relieving all decay heat via the break. ,.

N IN

2. Breaks that relieve decay heat .rith bech the EPI injection and via the break. [F x-i h 3. Breaks which do not automatically act= ate t',e HPI and result in f3 system repressurizatica.

+..'

E 3

1 4

The system pressure transients for these breaks are depicted in Tigure 3. L.

For Class 1. it is seen that the RC system 7tess.

re decraases rather smoothly o -

,3 "

throughout the transient. For the larger breaks in this class. CFT actuation and 1.PI injection will probably occur. For the s= aller breaks of this class

I' s only. CFT actuation vill occur. Auxiliary feedwater injection is not necessary for the shert tern stabilization of these breaks.

j Tor Class 2 breaka, the MC pressure vill rapidly reach the ESTAS trip f 1 .

signal 62 to 3 min). With e.he RPIs on, a slev systen depressurization vill f be established coincident with the decrease in cere decay heat. No CFT actua-T tion is expectsd. Auxiliary feedwater is not necessary for the short tera \,

stabilir ation of these breaks.

t Autotatic ESTAS actuation vill not occ*ar fer Class 3 *oreaks. Once the

. SC second

.ry side inventory is boiled off, systa=s repressurization vill occur V a

l as the break is not capsble of removing all the f.ecay heat being generated in -

the core. Systes repressurization to the POEr er the pressurizer safety L

valves will occur for snaller breaks in this cla.ss. For the "zero" break t

?

d case, repressurization to the POK7 vill occur i= the first 5 sinutes. Operator

• J 1

. .A P ,.rgg l '! ' , , .

• 7 8. f l, g y

.c....: :: u, '

o 1

,~-

y.. .:

~

f

~

3-

@#6 V

- . , - - . . . . - ~

i: 1[ ip3<.

, f4.'.11 ., __

, ,i o12o -

l

g . ,

[

action is required within the first 20 =inutes to ensure core coverage through-out the transient. For the 177-TA lowered-loop plants, this action can be

either manual actuation of the auxiliary feedwater cystem or the EPI systes.

The establishment of auxiliary feedvater vill rapidly depressurize the a

RCS to the T. STAS actuation pressure, and system pressure vill stabilize at 2 eitber the secondary side SG pressure or at a pressure where the EFI equa.ls W J'

[? the leak rate. ,

[

C I

Tor the Davis-Besse plants (raised loop design) operator action is J

~

necessary at some time greater than 20 rtinutes (probably 40 ninutes) due to the increased inventory in the loops that is available to drain into the re-  ;

L ,

actor vessel. However, due to the low shutoff head on the HPI system, the "

a operator nist establish auxiliary feedwater in order to depressurize the RCS. '

t Pressurizer level response for the first two classes of breaks will be ,

similar to that depicted for Case 1 and 2 breaks discussed in the previous ]

M -

section. For the Class 3 breaks, pressuriz.er level response vill be as shown '

r I (

in Figure 4 The minious refill time for the pressuriser 1, that for the "zero"

}~

l break and is shovu on Tigure 4. Af ter initially drawing inventory from the

.c

pressurizer, the system pressurization vill cause the pressurizer level to 1 '

increase, pessibly to full pressurizer level. Once the operator action to re-i store auxiliary feedwater has been taken, the system depressurizatica vill result in outsurge from the pressurizar, probably resulting in a couplete loss

?

, of pressurizer level. For the smaller breaks of Class 3 which results in a system repressurization following the actuation of the !IPI systen, pressuriser (J

level vill increase and then stabilize. -

j t'ithout auxiliary feedvater, both the hot les and cold icg te=peratures vill saturate early in the transient a d, for the Class 1 and 2 breaks, vill remain saturated. For the Class 3 breaks, once auxiliary feedwater is established.

b e#- ,.r ~ -**. . :- r y t i,;', ' '. i ! , I i

v.

• a !.'11.

9 f- - -

^

! 0120 hO ' UP' 0

! R3fMP-id[P-~  : 3

\

5

• i ,. ,

I -

3 i

i che cold leg te=peratures vill rapidly decrease to approxi=ately the saturation .

I g temperature corresponding to the SG secondary side pressure and vill re=aia b

$ there throughout the re=ainder of the transient. Het leg te=peratures will -

I i re=ain saturated throughout the event.

. 1.

< 9 i

6...&A 5 s k-

! .=

t ~

etll c .

r 7

o. .

i b,

M y

1 i.

1 _.

.i p i _

F.

t s -

4 J  ;

a.i r. - - ; ' .. m. . ,*., i,

=-

1 .

2

, m . .e ._. _ . . .. . -

l l

( ' _ _

1 , ,. .

.. f . ..s- > --

a ,- ,-

e  : ~

. n"L g 3 r r .,* p~. , g ~. .

't y ' . ' -- s' 1-

~ ,7 012 0 :' )"C')' I'i x ~ - -

6 i

. I l

. , . . . . . . . _. ....se

...... . . - n . ._. .. ., ,. . ;.

N -

P  % 5 y

1 o - = . k: 1

t. - i i , .

?

C ~. ..

~ s e 7 (

)- _

N .an s. ..

b E, Er.

N,, e l H

m ..:

a. , ,

. s.

i N, -

1  :

h03  ?.

Mg hE 4 =

sab g a

- L' C .

Q '

9"u y

\ O b 8 s

- c-- .

4

\ Fi i a 4

\ 4; q i s >-

"y. ,

\ g I

l '

ai.

da e s ,

A I 1 5

- 8 g I e

> e.

1 2

• E P i  ::

1..

8 l

0 l 1 .

u u

& - ) .

8 i 4

i l 1 _

9-

t. -

l 3 .,, . .3

- - . . 9 .~ ,

0120 jo,gosJg...6.

iHipi9-260/ ( .

)_ __

_ ._ -  :~ - _ _ -

. - r.  ;

-~

)+e:.run t, frir 8

e, s -

}3 o $ .

• 9  :.

m 0 , g

, . ~~.-

o

-p -

' @ ] I' I

N "e .3 i

7 0,  !

D . l k E.U

. . , o g ...

l 1 z. .

.I .

n.

, j '-

p

'l

).

N s

• L y  %

s - i, s. .

,a.  :'

w i b s- C .

4 s w N -

h v 0 3 A .. -

N Di .)

hI

! N g i -

L hh s s

. \ -

e i

bg 1 h r

-7-'

H 3 he.m. <-i dl,P  %.. ... ._

t ,

\

> 1

4

. s

'i ,e I

i t

Sv.AI.I. 3RFJJtS T.T P!JESSGIZIR i

9- The systen pressure transient for a < mil brea in the pressurizer vill be.have in a sinf1=r ranner to that previously discussed. The in.icM d= pres- ~

surization, bovever, vill be core rapid due to scez= relief out the break.  ;-

a y) The pressurizer level response for these accidents will initially behave '

4 like a verf small break without auxiliary feedvater. As shout on Yigure 5. an i 2

initial rise in pressurizer level vill occur doe to the pressure reduction in y.

3

' the pressurizer and the subsequent insurge into the pressurizer from the RCS.

i once the reactor tripw. system contraction results in a decreasing level in 1

the pressurizer. Tlashing vill ultimately occur in the hot leg piping causing e an insurge into the pressurizer and vill rapidly fill the pressurizer. For ,

the rer.ainder of the transient, the pressurizer will renzin solid. Towards .

the later stages of the transient.' the pressurizer vill be filled by a two-phase nizture. However, the indicated level vill show that the pressuriser ,

is only partially full.

4 k

c

,\

! p 4  ?

l  :

s

,;,inI

. . . n. . , 3 e :.

.:=

.J

e. 3 _.

. . -- .::r == -

~ -.. .

- - - . - - . - - _;=  ; g'. .'g':';t'3~

,_.2 c -

3 , O120 .

!._}{3__J ; 4 vg.., A. .

. 1

.. o .

t .

i ,

I . .

1 . . . . . .

3 -

I t - so o . . -

... .. + -. . -.-...- ..:- - ..

a .

m%

't . . . . - . . . . . . , . . .

I

. . . e, 39 .- .

n =..'

• 15 . . . . . .

p j

i .

I y

Y r'

~ a.

3  % .

.; g ,

q o FtcruRE -S -

. ~

PREstuRozER LEVEL V.t 'DM E t

(, .?

se .%  ;-

GREAK ZW 1 M FCR SM At. t. .

4-4;. tu u v R e ss u s tata .

I -

\

l ex,. r

~i-l w '

l. '

tu r" A

l l

L 25 i

l

( .

l *

\ ,

g  ;.

l

. o . . .

o 200 4ca ico 4

-[cc Icce ,

i 2

t TIME , $Ec. . . . . . . . . . . .\. t. . . . .

' c. * . n ..; r 1 ; ~ o

.,. .e t u s.s s e s4 . L 4

I1 -

. ~ .. . . . ~ ..

. ; i 2 c.

o12o oo-oc.-u.-

.. . ., i

a. -

g i

e H 3,c e. . p- .r. /.. -

I

) . - . _ _ - _ , . _ _ . -.

- _ . , _ _