ML20079H157

Nonproprietary Evaluation of Revised Transfer to Cold Leg Recirculation Procedure,Hb Robinson Unit 2

ML20079H157
Person / Time
Site:	Robinson
Issue date:	09/30/1991
From:	Matt Young WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML14184A878	List: ML20079H155 ML20079H157
References
WCAP-13072, NUDOCS 9110100182
Download: ML20079H157 (47)

Text

..

,, .'. . . . ,[, y '[ " " ' , .

a . ' . , ;-' .. ' .. , , . . . * , , ,..- ay*- ' ' "

, . ,. Y, .

• r - -

• ,'E <

. . . ',,*, ..,p

• ...., t .? . '

.g  ;-

. i .

1 .,

• s, " . .

. . , . . g * , , ..- + . m. - 6 , , , ,. .

.. . .s. e

.g*,. , . .-. . , -],, ' . ' . i

. game,suqngmassa ,., , ..

,'g,v,n'..

y . , < ,'** ,.,'.(.-. , . j -' ' ' ' ,,

?

o - . .,

.! . ..., .i .

'...r

.,.g 4 , .

~, s -

m ,

' c ' ' $ * '. ...",. .. . ,~,.

t.

). : . 3 .. .. n .

u , _ 'e, , .ib t.l3,: p. . ... , . ' - ,.- .4 . .. . ., .

c'

, .. , .l - 'a ; - -, . .I--

3 . s. .',.,,: ..

. ,, y. $

, ,f,  ;.

at. . . ', p i ( 7:* . . ~ .f.i . . .s  ;'.'  ;; ,.' .s ; u t E *,. , ,l

.. n ,, - ,{,, .,e s ,. 1" .'.

. . '{, * .

. . .../A,,,

. . , *, .,,*.,a

.- ; , .'.M.f,...~.

,. .g o ,,,,?, *

• et , ..,. ... * - -

.. . c;d,f.

..'s

- 1...; y, b. se . . . . , . . , ; -

s, y,' , , .

y .~ ,- l .8.'; .3 ,.g - ,,.

. . !, ' s. -, .. .;[ . .'. . , :' f p.. . .::

.' - l v. . , b. ,,; ,; y li *

.._,..'s;._",,

}.- ,

, y ;. y,  ;. ;_. g...- . . ._ . ..

,.,e,'_'. .a s~. e,, . .. <;'. > t, y s

,(  ; -

a.

. &, . xc..

- t.- - . '

ll ' . .,_ -' . .i.,'.,' ,-. .. i ...,,..?*,h, .{ .g ,f.vb.(Af..k_ j,3..s.^.t

' ., . . - .6 3 N_r

' . -~

4. .

4R ;, 7'.-;. : * ,,.W

.. : >- + * . i . .;-, , .- .

o , .. .^; ,- i +.'; ,,

-

• d. '- - ,, m n - ,,

.,c,,

.. " .. m , . m W, y

.,,p'. ): ;. r.v;.;.., .

. f r_ i .- ,,...,,--+

. . , . ,'.,,.-(

," ._ .- . . , ' . . t..

,, ,, L,,...  : ,\ %c '

• ,i.

,h ..'

.p ,, , - . . , ; i, . . ~. 5 , ,, .,.,; ,

, . . .- ,, , -*;,,,,,..p..',..< , < j .,.g c* .y.3,,,;

gi ,. ,

a g,..* ,%,

, ;g ,. .g,+A, . 4 3 ,- - n, .e

t. . 'f,- ,, ,

2*

[

- . ' I, . . . .] '

Ah - ' '

h a .

,s.. .': . ,_ { .' * ' '

s. .. . . , . - s- . s';. ,; .. ,

..e*.

. - * .w y . +

.y. y. 3. ' -,; . ,.-

• • c C.., . ,y; ;

~y ,.p,,,4'

.s,. - i . ,

. s 3 ,.

g ,...r.Y;,,J.; * -W, x p > ,

,' '2 ',i,' . -

.s .

g \. ;. ... ?  ;, .

,'q-

,' :., .. * ,' .). ..- 1, '?, _ *..y, % * *; :. lg}**g.

V y ;n - . ;. -

,,, y _-

y' I

, ' .m(

u f.,.' .fs ,' .,.', , ; . , . .

. ....,; . , '.*. -s.*.

~., 6 . ' , . . , ' , ', ',"[ " .3 '. .k'.1:, ;., 5 f. hl ,.

y '. i . . .. '. ,'

b' '.h, 4.

..,'("

', ' ; .

b..gc .,

. ' ' . . .- , . ' s.9. .s. t.,/e ,%.

~

.~- ' . . . ,. . . , .n

.. ~ . ,q s ( ... .. . . a.; M g:., >, - .;; s g..g . r, .

r,,,..- q.

s

. ,. ...n... . ..

, . " .e'J * , . ~ . . .

9. ,

k, ;h

,m- e 3,&,

,*. ../.,','.,-. '. ,gg.p '{ .'4,:.,*.., , , . , , .

y. - .. : ~ ,,. .b,-. ; .j< .} ,g.., [fl

.  %' , 88] - .. . *.

pg- .,' .i'..,'j'

. ~i !. g.A [ [ ^ j 3 : ,

f:),'-Q:-); . '. '

> n. .~@ , . . } ?i'*, Q f }:.

, .v . .; - *

,.v: . M,7 'y e : . .. . 1.n . . .

y',' :. 4

'.*'e',

' . , ' * ,j : s ' .* ' -Q f' y'.,'.. ,7. c.',.,4

' .:+**'.a '.* *',' %Y ' ' . x

' .' .e

'q'.;

+s ...,:

.

• _. ,, . 'r ';i.-n., ;% , n .%'

.').1

p '

' . . ' . . . . .....p. ~ . . ' , . . , ' ~ ~ '- ' '*;' *; *..*).

.. .' t,+, s . , .

t

. 4 h* .' l '~,.' ** f ^ . * " :

'^. .!

5

, h. b . , , . ; , '.

e

, - { ,,' - *. r.., .*

t egay. f. . ; i- 6eis. . . +c..i $ , * * > *

-'y..,.

.t

. .A 3 ..@ i

,-  :,l T. . .

.- - * . . *. , . . . , , J D_;" . .a ,t*r,f,f ,,9. ./g,.  % ,y,.

'2 .9. cs.,. s,*4. - . ' ..yl ,9,91. .), 'n.,'.,;'..4

., ., ..,,f1 qp .intg. ;,^ . ', .. '.

.y., .l

,, , .' .. .,. j '. . -:, ? .+. . . -,.s . . ' . . *

. ic ". , *,*; V.,. ,g,3.....,,,,..,.,c0.-

.. , . * ,.,, ,' ', .. . .'8 ... s .

, 4 y .s . s h,y , ;, 3 .'l4 ,- .,, ;-. . .

s

'..-[,

.' e- a*,

l .. ,.  ? .:i' 3' d. i , 's ,[ I.

p i ,

'.,*['.'.* [.;

'.'a. *#

,,g

. , ,

• b',f 'J ,*' ,'s f,',l.,,.e*<

t . ,,

t

~,y'_,: ,

• ,..'?',.  ;%, ,

j. , ..L t . , , . . . .. :. . . . , , * - ' . e e 1., , .j; .. .;. q <; ., ,. . . .; t . . . ; . l< .q,;.

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

• ,.:c.:..,.. 9...

- +

. , . -c

,y. .- i s ,,

.g',.,;-

.c , " , . .,

s,- . .,

,'g.,. ,.,1 ,

- . . . .- . , y . . y ,- .. \

, . , - ,?. ~ 'y ,. .=.'s.', . ;." ' s ,* '

' ' ' ' \"

..,g

• ._..>'..a.

, . -, st,-

. . ,[:*vi.' ,.*;, " , " . , ,

'> ' ' ' , .' - ,*- ' s . -' , '. . , ,-

- ~ ' - s'k ,t, ' . - *,-l,'.g' , ', t

..H ...,p.'.., * +, , f .i C . s ,*"s ['..y..-

.' . E

_"7-', } ' 8. . '..;... -

, . , . . 5 ,' , - *-

' '. 's,:.-.

,"g.. '.j t * . . . y*,..,, p ' "

f- . ',e*,[.,'.,'.,$5,.

.e.,', g,'

• - .. i .

. . ;, ; . ,;- . c .. *.' *

,- , , ' ' ' . .' . , . .9.. : 'h, '; (, , g,

• ' ,~I. , , .(. .'. - , -:/ -. g ' , ' 'e . ,

.. ,. , 8 . , ., -

' I. .[ ..,**- ,N '

'[ *e

, .. J,,, - * *-

• .,' " . . *v' '.

...' g

.g,{ ', ' , , , . ., }, ,-

S,',i.'- e..

s , , g. .

,e /s , . .. ..,e j, ., . .,

,?

' . \f .

. ,x*

• _ _ : . *

. .- .~ 4 . -

.

v.;

;. . ~ ,, ' , .'^: ': . ' ,

Z~* ' L <'_**',i

• ~

• .. - ,4. , .  ;

) %.. .k. , .. ." ,',. :., o f ...,., ..' $,

. ... .y

. ,ll;i. . ,, .-: .,:,, . > %' -',. =,

c. .., ' 4

. * .-,.;(:'.. ..

y. . * . . _ }. .. $ .. . . , _ . ..

. c..',4,- - ,1 ,p 3 ., .

g

, . , , g

.- .j' . - .-

. . .. % . - .'. .. , c, ..'.., .- . , , . . .-

.. -r . tr. ..

e. -' .. .. -

,..s . - - - .

's

',  ;*e,I- 'g. - <

, . ' Ys . , , ' . * , ,

'*g

,! "t,'.' 4 , ..,,a

,. ' [5 . ' ,

• l [' *

, ,..i '>

y - , .,' ~,:

'. ,.. . -. .' .. ~ ,......\b,.. -..-.

s .* ., -

.,+ .. * .;. e -

e.. .y e. .; .-

',j*,.,.,

Q ' , . 'J. * * . ; . . . -

• 4,,, N .,.,._. , ,, . ,8

- .,"; b.. *

'. . - - .. * + '*. *

..g. #

. i. * , ; , : " ,y ,.

. ,, s.

. . . . . . ,. . , ]

: _ ,[ . .. . y .4 J Q ' . j, :. 't. - -l .,e. .  :

_ . f.. :.: -. _ ' . -'

r,

.f ., . .;- , * . - ' - '

..,. s 6- d. +-

,; ; ' *. . . - . lf : v .

.

.[. ._. [ . ; ;;..  ;._. _, . _ , [ c ' _. " . ; .. . . ,; ':.,: -" , c . . . ,

.' .. .?.,. ;_. z. v. .

. : ..x; . ' . .r

.

• 3, . . '.'.: 4 . b. , # 1.. . . ,. - 4. .t. ,f.)

r -

. .,  : j- U,.5 ,,., : 1.(' r. '. ' .

e4 .

• ,,f','?

f .i

.5:.

.. . . . . . . '.- . . , .- .. o

,...,..~,c.h/.> . . . , .

..x.-.\.

..'.,. . , - .,..+..:'.,.--~

• . . . g . .. l . k- ,. .

l....*, .i l,...

. g%.a.%. ..a.,..... ....a.

. ,: ._ (,. * .r*-

.: ,. ':... . e v:, c ; ', ; _r.. ; .: . s,. ,; ,u  ;. ,.. .: ~--~ -a n % ~ '" ' ! ' ~ ' . ' , .-. , .: ' 1

, ./' , 7 i , . [ } !'

'.) {, 0 , 0 p. ' ' .'l  ?.*2', .. . v _

N ,' ,

c , y' . ' . . '... ' ..-

N** ',' ,a'_

7,. ,a , . .

• g ..,,"i;...', . .- ,. ,. .. e, ,, ' . , . _ . .. '- ,.',4,=

. ; .' .J' .,'I t .-

t

.  ; . ;. p

'. ." ' , . 3 .;- ; [' { , ,.'.l l? .j j ,, ,; - g*j

",. -c;f . I .,* . , ( y ' * .., ,' ' f .'. ; ' M, , ,s.,

[ , z . .. . *..-  : .?

• . .' .'**, . ,' gj ,n >

c 'w: % .. 3 a

.- ,'g'.;,....t.',,.,pg.,

, p .: , -

,,....%(9 x .' n' 1.y..,.,.* . - *)

. .j; ' . '. *-

,f

• ,- . ': -  ? . .! L':[.h 5 % * ; .  ;; _ ' , L' .: - .-',". L * , . . ,.? ," . . - "...t

. *, c [?. '. . ' 'y.[ - - a'. f. ;. [ .. . !. . n,

.,: : : , 12 :

,

",'L{([ { . K' h*'&g. *..D . lY . . : . .. -

l < . [-s'[ 1 ..

'. 's N '

? ;.' . ' . . , ',.

• t , '., '

. , p *... ,* , .

.*..,g... ...f' ;1.,.Mp s.~ .. :- p r , ,,,a . ',.', -..f g* .* .[ ' ]*: ;, ' p. I,[ ;' '

, ,i .

'.s. W s9.; 2;c :p.c.1 :. S.%. g.3 5 +;2 .- .

....~.. .;  : .;'

4.y.. e.., n.t ; .c : ~.; ..3.L -

. : y ,. _'_....'_'t.o.u,af.:

M'...>. *.T v. ' .p. ':.,..

9.~

, i'. L .L.' ..,...;  ; . ~. . .' %y N,.k, . . :

g

• _'_a .

, r, .:p.

.- . ..r %,,s * :t ,.

. . 3- *N

,.e.

o

,o

,lys i 3 'i.L,*.i.: , q . /,, iw M',,,lt % . : . , y; *( i %e.'

., a.m; 4,% g W, W: iJ M o.... .; ,9%K,.r.<?. ,y; . , 1 ,...-W Ma . . W,.t,f .J.L4>' q , W

M - 4:

a ... ..:.

w g:n.4 wg@pW e:M L3ffg p ' 'f;FW,%

w p:L mf%';,@h.i,w%W my .m Y.W . . i,M. . , y'.,.

ss%y:n.?f4 ? M,.y:,?;, M W& .;l.-('.W &

g.uu m,,.g . s e.U Pvpp W,el1: .?. .g. N.  : ..e;'.. . %x

_ v c w_'~ A? s. '. :.thew.:v.a

. . 7.. mA. .-n . d c.c y . , ,:: Lnn;':fgye_y4; , .? .

k ;+w_^;w%s e o '.s &%~ /~:_::nr.:.,

%.. .~ w v. wc.r a.: <v.v ' -W.g.w c ~c"'-  : :', % _7.u?.:n*W__ ..

e ...w . ..:- . m ' -

Westinghouse Class 3 WCAP 13072 AN EVALUATION OF TILE REVISED TRANSFER TO COLD LEG RECIRCULATION PROCEDURE II. B. ROBINSON UNIT 2 September 1991 Westinghouse Electric Corporation Nuclear and Advanced Technology Divbion P. O. Box 355 Pittsburgh, Pennsylvania 15230-0355 C Westinghouse Electric Corporation 1991, All Rights Reserved

9 Westinghouse Class 3 WCAP 13072 AN EVALUATION OF Tile REVISED TilANSFEll TO COLD LEG REClitCULATION PitOCEDUllE II.11. ROlllNSON UNIT 2 September 1991 M. P. Kachmar Prepared for Carolina Power and Light Company by Westinghouse Electric Corporation Approvt.d:

/M[d'

,/

Westinghouse Electric Corporation Nuclear and Advanced Technology Divisica l'. O. Box 355 Pittsburgh, Pennsylvania 15230 0355 C Westinghouse Electric Corporation 1991, All Rights Reserved

9 Introduction Presently the tmnsfer to cold leg recirculation procedure for the H. B. Robinson Unit 2 requires

-that all safety injection (SI) pumps be popped simultaneously to allow switchover from the injection phase to the cold leg recirculation phase following a loss-of-coolant accident (LOCA).

Thus, there would be a period of time during which no Si flow would be delivered to the reactor coolant system (RCS). Immediately prior to the brief tennination of Si flow fmm the high head safety injection (HHSI) pump, a residual heat removal (RHR) pump injects to the reactor coolant system for a minimum of one minute. The present Emergency Opemting Procedures (EOP) pennit an intemiption in SI flow for as long as 3 minutes following a large break loss-of-coolant accident or as much as 10 minutes following a small break LOCA Following the intermption in How during the switchover procedure, a single HHSI pump is available for the delivery of i

Dow into the RCS for any size break. During the recirculation phase, the RHR pump is not injecting directly into the RCS but is taking suction from the containment sump and providing How to the single HHSI pump and the containment spray (CS) pumps.

In order to detennine if the termination of all SI pumps simultaneously during the switchover to recirculation procedure is justifiable with only a single HHSI pump available, calculations were perfonned for both the large and small break events. The calculations were based upon an intermption period of three minutes following a large break LOCA and as much as 10 minutes following a small break LOCA.

Larre Break Analysis The methodology used to address this issue for the large break LOCA was originally presented I

in reference 1. The analysis methodology developed there relies upon a simple model (see Ggure 1) of the reactor coolant system to alculate the combined natuml circulation / boiling flow l depletion of the core inventory during .. period of SI tennination. The model is capable of calculating the vessel inventory as liquid is boiled off, entrained into the loops, and subsequently replaced by the SI flow. In addition, the model relics upon a simple steam cooling model to

2 I

f t- _ predict the clad heat-up behavior of a fuel rod during that period in which the' rod is predicted -

to experience dryout. The previous model (reference 1) assumed that the rate of change of t iie collapsed liquid level depended primarily on the rate of change of steam flow rate msulting from changes in the decay heat level. That is, a mass balance between the- flow into the core and that into the loops yielded zero:

H'c - II't = 0 . (1)

Subsequent to the development of the model documented in reference 1, a change was made to the code to account for the rate of change of 7,in the mass balance. This change was made to justify the original simplifying assumption (equation 1) that the core Dow equals the loop l flow, By incorporating this term in the mass balance, the co'. lapsed liquid level could be more j

- accurately predicted. In order to account for this change, the following equations were .j developed and incorporated into the original models of reference 1. l l

i Let:

dhi' TV c - 15'1 = (2) dt i

where

H'c a pow into the core lVi a pow into the loops hice mass in the core Approximating Afc as:

hic

• PLAZ ce l

yields:

dZC IVc -TVt = ptA (3) c dt I

3

T where Zeis the core collapsed liquid level. Noting from reference 1 that the collapsed liquid level may be expressed as:

Ze

- [ #'(1 -n)dZ (4) and appropriately applying the { }3,a yields the collapsed liquid level as a function of the average linear heat rate (O'):

{ } ta.c) (5) when :

( } (a.c). (6)

Equation 5 above may be differentiated to yield:

{ } (a.c) (7)

From reference 1, it is recalled that the driving force for the hop flow during the period of natural circulation following a LOCA may be calculated by equating the pressure differential due to the density diffen nees between the downcomer and the core, to the loop pressure drop as follows:

K I W[ = (2 3 -Z) c (8) 19yAE PiR 4

l t

-4 :

By setting:

2 psp S iA' l A2= Ki ,

yields:

lif c Zp -Z e '(9) l

)

Equation 9 may be then be differentiated with respect to time: l l 2 II'idWt dZo _ dZe A2 dt dt dt dZ Since: u_ 11's- 1l'c dt ptA p substitution yields:

3 11'idW, 1Ys -1Yc _ dZ c ,

A2 dt ptA y dt Recalling equation 3, manipulation and substitution yields:

if's 1 dZ c dZc W.t + pt A .

(10)

PtA p PtAp r c' di , dt 5

I Ws 'A ' dZ 2 WdW i t :WL c

- - - c+1 (11)

-A 2 dt . ptA p piA v Ap ,

dt Solving equation 7 for dZe/dt, and equation 11 for Wt , allows the core Dow (Wc) to be determined from equation 2:

dM dZ l H'c " WL

• dt

• WL

• PL ^c dt l

, ( 3,- )

I This definition pennits the downcomer level, location of the 90% quality line (29), the core Reynolds number, and subsequent vapor temperature calculations to be {

} (a.c), and not solely on the now into the loops as in the previous model, Furtheimore, since the revised modelling explicitly calculates the change in core mass as a function of time (actually dZc/dt), the integration given by equation 4 may now be carried out over the entire core height (Z,.) and not just to the elevation of the 90% quality level (Z9) as in the previous model. That is:

{ ' } ta.c) (13) l l

where:{ .}(a,e)

The downcomer height is still calculated as:

l l {- } (a c) .(14) 6

9-when:: We e flow into the core W, e flow provided by SI Transient Descrin!!st The revised switchover procedure n:sults in a sequence of Si nows to the RCS as given in Figure 2. The switchover pmcedure for the large break LOCA may begin as early as .

approximately .21 mint.tes (time = 0 on figures 2 - 8) when the RHR pumps are tenninated to take suction from the containment sump. At this point, flow to the RCS is pmvided by only a sirgle high head safety injection (IIHSI) pump for another 21 minutes (1260 seconds) at a flow rate of approximately 45 lbm/s. During the time period between 500 and 1200 seconds, the loop

- flow is seen to equilibrate at approximately 43 lbm/s. As the loop Dow (Hgure 3) equilibrates to near the boil-off rate, the core exit quality (X9) (figure 4) increases to 90% such that dryout is predicted to occur. The 90% quality level was chosen as a predictor of dryout since void fractions indicative of the critical heat flux (as predicted by Griffith's modification of the Zuber equation (references 2 and 3)), would be obtained at core exit qtkalities above this value. Once dryout has been predicted, the simple steam cooling model described in reference 1 is then utilized to calculate the rod heat-up tmnsient. The results of the clad heat-up transient are as given on Figure 6. Here it is seen that during the period following initial swit. hover (500 -1200 seconds), the rod heat-up occurs until approximately 21 minutes (1260 seconds) when the RHR pump is restarted for a minimum of one minute while the HHSI pump is realigned. As a result of the injected RHR Dow, the rod heat-up transient is mitigated at a peak rod temperature of approximately 1380*F and the downcomer inventory is quickly irplenished resulting in a corresponding increase in the overall h)op flow. The core exit quality drops rapidly during this period until 22 minutes (1320 seconds) following switchover when the Si is tenninated completely for a maximum of three minutes. The tennination of Si results in a rapid increase in the core exit quality and an ensuing second period of clad heat-up. However, once SI is 7

• :- reestablished in the fonn of a single IIIISI pump delivering flow to the RCS, the heat up transient is mitigated over the next 750- seconds. From an inspection of Figure 6, it is interesting to note that the 10.5 - elevation is the last rod location to recover fmm the temperature excursion. The reason for this, as stiscussed more fully in teference 1, is because l of the skewed to the top pe.<er shape chosen for this analysis. A review of reference I reveals that the actual power shape is peaked between 9.5' and 10.0'. A justiGcation of the power shape selected for this analysis may be found below.

In order to ensure that the_ models used in the analysis of the large break (nmsient were l l

accurately predicting the mass balance between injected flow and that flow boiled off as a function of decay heat, enhancements were inade to the code to calculate the actual boil-off rate as a function of time and the elevation of the 90% quality level. As alluded to above, the 90%

quality level was used as an indicator of dryout. Therefore, the trackin;; of the location of the 90% quality elevation m:y be used as a conservative estimate of the mixture level in the core.

' Above the location of the 90% quality level, the rod was assumed to be dried out, while below this elevation, mixture was available to be boiled off. The amount of fluid predicted to be boiled-off was calculated as follows:

g,na , (QP)(P1)(29)(NRODS) yh (15) where: QP = 5.69 BTU /ft-sec ,

P1 = P/Po (Decay heat 1971 +20%)

.Z9 = Elevation of Dryout (i.e., rods are dried out above 29)

L l NRODS = total # of rods = 32028 8

h,, = hr, (30 psia) = 945 BTU /lbm Utilizing a control volume around the core yields the following:

A2 C It'c - li'gu = ptA c d'

(16)

Re-arrangement of equation (16) yields:

A Z = (11',,- Wuy)At

~

e PL^c where: 5f'c n flow into the core Wua e boil-offflow pt a liquid density Acn Core Flow Area _

As seen on figure 8, the collapsed liquid level calculated in this manner is greater than that predicted by equations 7,11, and 12. This is because these models conservatively assume that 10% of the water entering the core is lost and cannot contribute to the removal of decay heat.

As such, the models used to predict the response of the LBLOCA to a tennination of Si flow are conservative with respect to the prediction of the callapsed liquid level.

A summary of the LBLOCA transient results is given in the following figures:

9

. .. . . . - . - -- - - . - - - . - - - .. .. . - - ~ ~ . - - - .

9 Ejgts Title 3 Loop Flow 4 Core Erit Quality (X9) 5 Down ner and Core Collapsed Liquid Level 6 Rod Tempemture 1- Location of 90% Quality Line (29) 8 Core Collapsed Liquid Level Companson .

t i

A.s part of the analyses perfonned previously to justify the use of this model, an investigation  ;

was performed into the effects of the initial core average power shape. A spectnim of shapes was considered ranging from triangular based shapes skewed to either the top or the bottom of the core to trapezoidal based shapes similarly skewed, in addition, the traditional cosine based

. shape was postulated for the core wide average rod. The results of these. studies indicate that the core exit quality is relatively insensitive to the initial power shape and as such, the resultant rod temperature is maximized via the use of the original (teference 1) skewed-to-the-top power shape.

In addition, a brief investigation into the capability of the vapor flow at the top of the mixture level to entrain more than 10% of the liquid was performed. As discussed previously, it is noted that the void fraction calculated near the top of the core ranged from 80 to 90 percent. At these void fractions, the flow regime may be considered to be in a churn-turbulent to annular transition. Steen (reference 4) derived the following expression for the onset of entrainment:

f '

Ju#

8 2p ' : > 2.46 x 10" (17) 0 ( Pij f

where: ), - steam volumetric flux u, = steam viscosity 10

9 p,. = sicam density pt = liquid density Based upon equation 17, the critical gas velocity ( j, ) was found to range from 75 to 120 ft/see, for the pressure range of interest (40 to 20 psia). At the time of initial switchoser, the steam generation rate may be calculated by equation 15 as approximately 50 lbm/s. This generation rate is approximately 2.5 times lower than those steam flowntes wheih occur during the inital renood phase when entrainment mtes are relatively high Since the corresponding volumetric flux ranges from 12 to 24 ft/sec in the pressure mnge of interest, the critical gas velocity for liquid entrainment is not attained and the vapor flow at the top of the mixture level will not entmin more than 10% of the liquid.

Omdpsion - LBLOCA Analysis In consideration of the discussion provided above and the L.tached figures, it may be concluded that ahhough the analysis perfonned in consideration of the natural circulation and core boil off has shown that although the vessel liquid inventory is reduced during the 3 minute internqaion period, the calculated PCT is still well below the 10 CFR 50.46 limit of 2200 F.

Small Break Analysis The results of the H. B. Robinson Unit 2 ECCS perfonnance analysis in response to a SBLOCA are documented in reference 5. A spectnim of small break LOCA events ranging from a 1.0" break to a 3.0" break were postulated as part of these analyses. Each case was perfonned using the Westinghouse NOTRUMP Evaluation Model (references 6 and 7) and calculated the PCT results based upon the perfonnance of only a single HHSI pump. In order to address the termination of the single available HHSI pump for as much as 10 minutes during switchover, analyses of both a 1.5" break case and a 3.5" break case were perfonned. These analyses 11 ,

l modeled a tennination of SI for a period of 10 minutes at a time in the transient before the actual calculated switchoves time. For the 1.5" hreak case, the Si termination was modeled at -

10,000 seconds following break initiation, while for the 3.5* break case, Si tennination was l

modeled at 5,500 seconds. As un below, the actual calculated switchover times were on the order of 10,800 seconds and 5,930 seconds for the 1.5" and 3.5* break cases respectively.

These actual switchover calculatiot s were based unon variot.s cornbinations of 1111S1 pump,  !

containment spray pumps, fan cooler operation, as well as RCS back-pressure. Only the most emscrvative calculations are reported in me followmg table and were utillied in the actual anv; sis. f i

SEltdtnei Dltak LlutSthats LQ3mW 1111SLElow RGAnunc _Ilme 3.5 " 1 2/1 525 ppm 100 psig 5,930 seconds 1.5" 1 1/1 525 ppm 100 psig 10,88 9 seconds

• Since both analyses modeled the Si tennination well before the actual switchover time, they have i conservatively captured the effects of the ufety injection interniption on the resultant clad temperature transient, in each case, while a second clad heat up period ensued follow!ng the termination of safety injection now at the time indicated above, t;.e second clad temperature

.- ccursion was less limhing than the peak-cihd temperature calculated in reference 5. A comparison of these results is given in the following table.

Breakfanc Pf.I NO SI FCT 1.5" 1991 'F' 1936'F 3.5" 1453 'F NA *F isce concia, ion)

The results of these two cases are c,picted graphically in Figures 9 through 30. A description ,

of each of these 6gures follows:

12

1 EJue Thle i 3.5" Case 1.5" Casg 9 20 RCS Pressure 10 2l Core Aft.tture Level l1 22 Downcomer Afhture Level 12 23 Total Afbture Afass ofRCS ,

'l3 24 Core Outlet Yapor Flow 14 25 Break Vapor Flow 15 26 Pumped Sqfety in' n Flow l

16 27 Core Top Node Vold Fraction i 17 28 Top Core Vapor 7'emperature 18 29 Upper Flenutn Node Vapor Temperature 19 30 Clad temperature

• This PCT differs from that of rrference 5 as a result of modiGeations made to the clad heat up Small11reak LOCTA computer code. These modifications were reponed in reference 8, The use of this code version ensures consistency with the calculations perfonned in suppon of the Si tennination analyses.

Conclusion - SBLOCA Analysis As seen from these figures and the discussion provided above, the second clad temperature transient results in a NT which is less than the PCT calculated before the initiation of the switchover procedere. In panicular, inspection of'je core mixture level plot (Agure 21) of the 3.5" break reveals that a second core uncovery does not occur during the period of SI

- tennination as a result of the very high mixture levels pmceeding switchover. For this panicular case then, the clad heat-up tmnsient calculations were not perfonned beyond the 4000 seconds.

In the case of the 1.5" break, approximately 55'F of margin was calculated between the Erst clad temperature peak and that which occured during the ten minute interruption period. As 13

such, in each instance the termination of the single lillSI putup for no inore than 10 ininutes at the tirne of initial switchover is acceptable froni the penpective of the S11LOCA analysis.

1 3

I l

l 1

r i

14

Refettu m

1) CPL-87 582, " Carolina Power and Light Conipany, IL B, Robinson Unit 2 - LOCA  !

Evaluation for Revised Cold 1xg Switchover Procedure", July 6,1991.

2) Zuber, et. al., "The liydrodynamic Crisis in I ool Bolling of Saturated and Subcooled Liquids", Part II. No. 27, littenlationall2erdenttients.ittikat Transfer,1961.

3) E if0th, et. al. , "PWR Blowdown llent Transfer", Ihenitalatld.lb11ralditAHEtu2Mudcar Erae .r Saffely, ASME, New York, Volume 1,1977.

4) Steen, D. A., and Wallis, G. B., AEC Report NYO 3114-2,1964.

5) WCAP 12034, "Sniall Break LOCA Analyses with One liigh llead Safety injection Pump-Available for the II. B. Robinson Plant", October,1988.

6) hieyer, P. E., "NOTRUMP - A Nodal Transient Small Break and General Network Code",

WCAP-10079-P A, August,1985,

7) Lee, N., et. al., " Westinghouse Srnall Break ECCS Evaluation Model Using the NOTRUMP Code", WCAP-10054 P-A, August,1985.

8) CPL-91-039, Carolina Power and Light Company, ll.B. Robinson Unit 2 - ECCS Evaluation Model Changes", June 20,1991.

15

! - "dkes

' ~

l'[(

'~

s }

lJ =

a  :: -

=

m pla*1!a n 5

, \ f

• b

!CD k i<

g ,

,j L4 r:

O h m

8, f --'t D v

llei(

g ..

1. h a; s s' ,

e h

FIGURE 1-RCS MODEL FOR POST LOCA LONG TERM CORE COOLING

lk{ r ,

1

.. i i

6 Flow to RCS During LBLOCA l Switchover Procedure i

360 c-

! I l  ! .i .

.4  !

i h

'i Flow to RCS l l

(Ibnteec)  ! i I

I i i i I i i

i

! MHR f

! -o' i 45 r ,

l i {

l I

L _ __

0 21 22 25

~j t (minutes)  ;

Time Following Switchover 21 minutes '

following event FnURE 2-FLOW TO RCS DURING LBLOCA SWITCHOVER PROCEDURE ,

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

! !1 O

O 0

0 0,

3 2 S E TSY I

I M

I T

NL A 0 0)

S V

U N '

0, C W N AR 2E S

(

O L

F OEV E o SO NHC I

f M I

T O

O L-3 BI T E R

OWS q U G

RI S I F

H .

B. H 0 0

H1 '

0, 1

\ .

0 0 0 0 0 0 0 0 0 0 8 6 4 2 0 8 6 4 2 1 1 1 1 1

_Ou J h 9 3 9 w a.O 9 Ilill lll

i H.B. ROBINSON UNIT 2 1 HHS1 SWITCHOVER ANALYSIS 1

0.9 -

I 1

Cg 0.8 f

D a

<t 0.7 -

3 O

F-

]0.6 E

O0.5 0.4 -

3 i  !

0.3 0 1,000 2,000 3,000 TIME (SEC)

FIGURE 4-CORE EXIT OUAUTY VS. TIME

H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS 16 q DOWNCOMER l 14 ,

COLLAPSED UQUID r 12 -

v L

Z O -

<- 10 w

l _J W 8 -

~-"""~""~""~~~

6 .._....____._-_ ----,,,,,,,_ ,,,,,,____________________-_--- - --- -----~ ~-

4 O 1,000 2,000 3,000 TIME (SEC)

FIGURE 5 - DC/ CORE COUAPSED LEVEL VS. TIME

ll)ll!!l

~

~ _'

'0.

~

'5. ~- '0 '5 _

0 _

1 0-1

~

1 1

1 1 _

0 i

0 0,

3

,l ,s ' ' i 8 i I ! E M

I 2 S

- T.

S TSY I

I 0

V E

NL A -

0) 0, C R

U UNA  ;*!hl I!i!!

ii i 2E T

A R

- S N R

- ( E P

OE V f!:

-:i-::::

E M

M -

SO f [' I T

t i

NHC I O D

BT I R

6 OW S yI ll' iigIli} E R

RI S U H 0 G s \s \' ' '

0 I

F B. H _ '

0, H1 1

.r'"

~

,v "~ j /

if i#

5-(( y g/

f I. I; ' : :;

ifi l O

~ ~ -

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 6, 4, 2 0, 8 6 4 2 1 1 1

~ m[3Q mn_2mF OOm l  ;;l!1l:ll 1 ' l

1 H.B. ROBINSON UNIT 2 1 HHSISWITCHOVER ANALYSIS 13 12

=

A 11 -

O u.

O z 10 -

9 ~

!E

>j u g -

m 8 -

i l

7 O 1,000 2,000 3,000 TIME (SEC)

Note: When ZJ>12*, Z9=12' FIGURE 7-90% QUALITY UNE VS. TIME

H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS 12 NOSI PREDICTION MASS BALRJCE 10 1.

v c ****.... -

O * .

g- _.....

<C ...

m 8 -

._s ....

m ...-

m ._

ti- ...

O *.

O __...

6 -

4 600 800 1,000 1,200 TIME (SEC)

FIGURE 8-COLLAPSED UQUID LEVEL VS. TIME

I -

H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS 2400.

2200.

2000.

_ 1900.

E m

S 1600.

d h1400. r U

c.

g 1200.

O ce 8 1000.

O \

E 200. \

600, 400' N

, N 200 N N 1000. 2000, 5000. 4000. 5000. 6000. 7000.

TIME (SEC)

FIGUR&9-PRESSURIZER PRESSURE (PSIA) 3,5' BREAK l l

. H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS 54 52.~

50.

29.

.; 2 6 . ]' idI" hoJJan F

j I '[' [ rr[ {ip y 2a.  !

l 1 ,-l rr '

g x

5 22.

• /

20. /^^b v - -

(

I 18.

f f

16.

14 D. 1000. 2000. 5000. 4000. 5000. 6000. 7000.

TIMC i3CC)

FIGURE 10-CORE MIXTURE LEVEL (FO 3.5' BREAK

. H.B. ROBINSON UNIT 2 i HHSI SWITCHOVER ANALYSIS 54, i

$2.

50.

C 29.

b d

J

26. t g i} kii 2 24 hY k j# a 4

x l vg r I k.,

/

5 22.  % , >'W

• i i

(

g 20. /

k le. ,

16.

V 14 D. 1000. 2000, 5000. 4000. 5000. 6000. 7000.

TIME (SEC)

FIGURE 11-DOWNCOMER MIXTURE LEVEL (FT) 3.5' BREAK

H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS 45E*C6 4E 06

-. .EEE 06 E

d h .5E 06 e i w

f.25E06 ,

U 2

y .2E.Os E

5

~ .15E 06 -

- ^

/ \ /

/ <-

_-1

.lE*06 -

50000 l I D. 1000. 2000, 5000. 4000. 5000, 6000. 7000.

TIME (SEC)

FIGURE 12 TOTAL MIXTURE MASS OF RCS (LDM) 3.S' BREAK I

,,,,,,,,,,,,,,o

H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS sea.

250.

O M

$200.

d E '

d

@ 150. -

i 5 ,

=

5 ICO. l) d 8

A

50. kmk4 a - -

'T AwWW 0

D. 1000. 2000. 5000. 4000. 5000, 6000. 7000.

TIME ISEC)

Fl-URE 13 CORE OUTLET VAPOR FLOW (LBM/SEC) 3.5' BREAK

. _ _ _ _ _ = _ _ _ _ _ _ _ - _ _ _ _ _ _ - _ _ _ _ _ _ _ - _ - - _ - _

H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS 160. _

I 140.

120.

C d

j 100. -+-

d >  !

a d 90.

E c.

11 u 60.

40' A 1-D Q' [V'Qwn 5 20.

D. 1000, 2000, 5000. 4000. 6000. 6000, 7000.

TIME istc)

FIGURE 14 BREAK VAPOR FLOW (LBM/SEC) 3.5' BREAK 1

H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS

.: s . ,

I

~ u, .

,s

~ . #9 P <

55.

O d

il 50. -

5 25.

2 S 20. i b l 5 l c.

O I5.

5 d

10, 5.

O 5000, 6000, 7000.

D, 1000. 2000. 5000, 4000, TIME (SEC)

FIGURE 15-IL LOOP PUMPED SI FLOW (LBM/SEC) 3.5' BREAK

H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS

.e- t i

7 N

.6 5 \

C i y ~e "1 .,

i 3 Vdd,ggg$

0 i E ,

WN f+I.bW "O,YN

$.5 bd 0 1 I

.2

.1 B. 1000. 2000. 5000, 4000. 5000, 6000. 7000.

TIME (SEC)

FIGURE 16-CORE TOP NODE VOID FRACTION 3.S' BREAK

H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS

00.

1000. fy -:

l ,

i t C00. ,

U e

a 600, 6

h W

700, y 5

i 8 i S 600. ,

u i a .

8 i

i s00. -

?x 400. -

~  %

E00 6000. 7000.

D. 1000, 2000, 5000, 4000. 5000, TIME (SEC)

FIGURE 17 TOP CORE NODE VAPOR TEMPERATURE (F) 3.S' BREAK

H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS

^20.

I lp I -

GE' I i.

I 600. ,

. i 2 l. l

-a, '

u I  !

S j700.

~

e h}

650. -

u N O

h

e00.

ib i v-  ;

^  !

g C; 5 5 0 . .

/\y 1 c

" 500' i

(

3 3 450.

400.

, [N v

$ 0 '0 . 1000. 2000. 5000. 4000, 5000, 6000. 7000.

TIME (SEC)

FIGURE 18-UPPER PLENUM VAPOR TEMPERATURE (F) 3.5' BREAK

H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS

, t

1 i )

I i

! i  !

,2 ,. --_.-

{

2  : i l

--  ; i i O~  ! l f I i i

I

- I i i

5 l  :

../.. -

I W

L--

400. --'

500. 1000. 1500. 2000, 2500. 3000, 3500 4000.

Tlf1E (S)

FIGURE 19 TEMPERATURE (F) 3.5' BREAK

1 1

I

H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS 24ce.

22C0.

2000.

l G tec0.

t u

h1600.

O E

$ i4e0.

b s

w 0 12c0.

t (4,s T ;_ _ --

1000. '

600.

g D. 2000. 4000. 6000. 6000. 10000. 12000.

TIME (SEC)

FIGURE 20 PRESSURIZER PRESSURE (PSIA) 1.5' BREAK

i l

l H.B. ROBINSON UNIT 2 1 HHSt SWITCHOVER ANALYSIS 54 --

1 52, 58.

u

.a 26. .

Y '

M u 24 5

E 22.

W )

8

29. (

18. ,

16.

9. 2000. 4988. 6000. 9898. 19908. 12888.

TIME ISCCI FIGURE 21 CORE MIXTURE LEVEL (FT) 1.5' BREAK

H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS E4 52.

E0.

_ 2b.

b 26.

f b

w 24 -

L^.

X E 22.

m i W '

f; 20.

- i is. ___

\ g yf\ -

/

l 1

n. /

D. 2000, 4000. 6000. 8000. 10000. 12000.

TIME (SEC)

FIGURE 22 DOWNCOMER MIXTURE LEVEL (FT) 1.5" BREAK

H.B. ROBINSON UNIT 2 1 HHS1 SWITCHOVER ANALYSIS 45E 06 4E 06

~

E .5EE 06 d

a b .EE 06 8

E w

E .2EE 06 E

=

5 .2E 06

. LEE 06 L

'I '

N.

w_ ' \/

2000. 4000, 6000, 8000. 10000. 12000.

1IME (SEC)

FIGURE 23-TOTAL MIXTURE MASS OF RCS (LBM) 1.5" BREAK

H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS 220. --

000. _

160. -

- 160.

S O

$140, d

g,120.

d b 100, b l ll i

60. [-

'j -d$[  :

jl  !

G 60. l b'd Y 0 40. . 4 00.

7 hp)h' k k%"Tr [

0. -- -

' \

14 2000, 4000. 6030, 6000. 10000, Tiece.

TIME i$ECi FIGURE 24-CORE OUTLET VAPOR FLOW (LBM/SEC) 1.5" BREAK

H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS

50. ,

25'

' \I ^

11 ll 'k /)

Mmt

\

C 20.

d l 8 I l

d is. l l $

e E

, g 10. .

o 1

l l

5.

D. 2000, 4000. 6000. 6000. 10000. 12000.

l TIME (SEC)

FIGURE 25-BREAK VAPOR FLOW (LBM/SEC) 1.5" BREAK

H.S. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS 50.

' ~

25.

C M

$20.

d '

r,)k sa G 15.

S b

S 10. - '

S V d

5. --

0

0. 2000. 4000. 6000. 8000. 10000. 12000.

TIME ISEC)

FIGURE 26-IL LOOP PUMPED SI FLOW (LBM/SEC) 1.5" BREAK

j H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS i.

9

.8 s .,

~

I _

E E .6 e

o I

.5 l 8 ,  !

? l a 4

)\ L .

It i U '

l .

l 8 .s --

s L.-

.2 l

) -

I 3 l -

.1 -

D. 2000. 4000. 6000.

I 6000. 10000. 12000.

TIME ISEC1 FIGURE 27-CORE TOP NODE VOlD FRACTION 1.5" BREAK

0 H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS is00.

1400. -

1500. l\ '

M 1200. f

? \ l e

{1100.

\ l W

$ 1000, f j

i

> I

$ 900.

=

I sJ . -

1 u i

'\

- b 800.

S 700.

g 600.

L - /

D. 2000. 4000. 6000, 8000. 10000. 12000.

TIME (SEC)

FIGURE 28-TOP CORE NODE VAPOR TEMPERATURE (F) 1.5" BREAK

1 H.B. ROBINSON UNIT 2 1 HHSI SWITCHOVER ANALYSIS 1200.

1100.  % b

/

a

]1000. -

E

$ C00. -

N ,)

S

~00' C

5 / NJ C3 .

d b 700.

l S

2 l

600. \

=, I' 500 D. 2000. 4000. 6000. 8000. 10000. 12000.

TIME ISEC)

FIGURE 29-UPPER PLENUM VAPOR TEMPERATURE (F) 1.5" BREAK

H.B. ROBINSON UNIT 2 1 HHSI S'NITCHOVER ANALYSIS

^

i. .

i  !  !

i i i '

i l

j i  !

Z  !

i  :

_  ! , i j E ,.. i l l I

l 2 . 2 .' ' . .

I t

w G

'~ I  ! i

3, I

.. i e i. U .

400.

3000. 5000. 7000. 9000. .llE+05 i I t1E t5)

FIGURE 30-TEMPEFiATURE (F) 1.5" BREAK 1

. _ _ _ .