ML19221A299

Natural Circulation Operation,Criteria & Conclusions

ML19221A299
Person / Time
Site:	Crane
Issue date:	04/19/1979
From:	Malahan G NRC COMMISSION (OCM)
To:
References
NUDOCS 7905210231
Download: ML19221A299 (6)

Text

-

J.* 4 7 lY

.iz N rr

~~

^

~

btvN 4/ttbf.

~

b y-

, Hry thiskw p :!.' !.! ; f. ' )

hh v'4 f cu fe.N 0}34 t.

I I

O i'

s.3 criteria and coaclusioas-t The transition from forted core cooling using one reactor coolant pump to the natural circulation model should be acccmplished with minimal risk of further core damage (zirconitrn oxidation, fuel melting or structural degradation) and mininul risk of unacceptable activity release. The functional criteria to accomplish these goals should be as follown (a) Avoid bulk boiling of core coolant (b) Avoid prolonged conditions where local tecperatures of core materials exceed 1000F (c) Avoid system conditions which could result in pressure instability -[

with susceptibility to large pressure pulses.

(d) Avoid operations which have the potential for relocation of fuel.

debris in a manner that would adversely affect core coolability.

(e) Avoid conditions which could result in bubble formation of hydrogen or other noncondensables which could inpact the natural circulation cooling.

(f) Avoid boren dilution and return to criticality.

(g) Avoid rapid or unneces.sary additions o' cold water to the RCS (i.e. through charging) because of the adverse effect on s9 +1W < h.JJ b ~MlYN]

gy The B&W criteria for avoidance c.'. bulk boiling is based on maintainin'g 100F subcooling in the hot leg P Ds.

The staff believes this to be adequate for operation with two steam generators.

However, the incore ther-ncouples at the core exit are a trore reliable indication of core O

boi,ing while bypass riew exists in an idle steam generater, we 111 1 59.052 D'

7905210 N I

s O

require that natural circulation be discontinued if the average

-i value of incnre thermoccuple readings should exceed the saturation

~

limit indicated on Figure 5.3.-

Additionally, the B&W criteria provide for a maximum coolant temperature rise of 150F across the core and require a hot leg 1

temperature rise indicated within the first hour during transition f

to natural circulation. The hot leg temperature is not to exceed 2bCF for pressure greater than 500 psia and 180F for pressure near atmospheric. The staff finds _ these limits acceptable.

Limits _

which require ten or more incore thennocouples to read lower than saturation are not.needed in view of the staff raquirement on aver age readings.

Lik ewise, local limits of 800F on two therm 6 -

couples appear arbitrary since local high temperatures are a.:ceptable, however, none of the thernoccuples should be permitteJ_

p cx r.bsve 1000F (the zirconium oxidation l{mit for more than one hour while restart of a reactor coolant puq is a viable option.

Operation with a solid primary system during transition to natural circulation.is undesirable.

pressure pulses due to unstable boiling t

. conditions could result in core structural damage.

The collection of debris in the bottom of the reactor vessel, as 6 w ei- ' bc Wv ed +c be. c( shdA5 described in section 5.2.2, tn. --

~ ' - ~ ~

+ -

e mm w (ct.

Cr1 transitten to natural circulation.

The staff is continuing 2

to review c-cooling s -f

'a by cellular con'/ection based on analytical O

aad expert =catel work at sendia-while the risk now arne rs minfrai.

159 053 7 11

=

\\

i 3_

O m --- :

., =_TgWp a :

9. '..-:_ %

uldlM h i

~

,,uG A -=.k our review of this problem 4s completep SCN A

t*

1 J

Minimum system pressure to prevent hydrogen bubble formation and.

an evaluation of the effects of a gas bubble on natural circulation j.

g ', _. ; '

are discussed in other sections of this report.

{. ",

z.

.n

.p...

It was noted in section 1 that the leakage rate during the TMI core -

):; -

damage incident was nuch uter (395,000 lbs/hr) than the capacity 1

'N *

~

(,

(112.800 lbs/hr) of the power operated relief valve.

Excess leakage m'y have been to Steam Generator B.

Caution should be exercised r

P to avoid bcron dilution or primary coolant activity release when comencing operations with the isolated steam generator.

.~.-

O Based on thermocouple / trending data, local temperatures could s

,-s r exceed Me? if transition to natural circulation is attempted prior

/79 (see Tables @C'and f 1- __).

The high tecperature ~ ~

toA

-- w will not necessarily be indicated on core exit thermocouples since them -

n N.km Q

marrer of debris which ee prcducing the high temperature ray drop A

A further from the thermocouple locations under the low ficw natural e -o:k T

circulation conditions.

c i,J e -n planned c =-

-m m-cl u.n.i m n M r b n t Y u W 33 cf transition to natural circulation A n = o =

=1 r e J m. >

hy G wi A4 uA +k & cf e c.a yf._ _ d Gn. lel clc hi s oms k.c tJ J

&.+

.o A

-m_

n. z - = _- w m

7%ge measured or unrcasured temperatures in exceess of 1000F and will 4

minimize potential restarts of the coolant pumps which could lead to further core damage.

O 159 05A

s The staff has concluded t_ hat the ECC injection nodes (HPI and k4R) do not offer any significant advantages over a natural circulation cooling.Inode Amt in._facLhavrseveral..diusivanhnen. nemfoce.,.....

we would not recoerend abandoning the natural circulation mode'in

't

..n favor of HPI or RHR, unless the abov.e criterta are e.xceeded and im-

-E proved, conditions can be reasonably be expected fin the alternative cooling rode.

4 In addition to the stated criteria, systematic failure of thermo-t couples in a given region should be viesed as a" danger signal of gj high local temperatures and a warning that effective cooling "-

-[

is not being accomplished under natural circulation.

{'.

The limitations on process parameters to assure adequate core ~~

"~

TIds%O ccoling in natural circulation are sumarized in TablfW> =_ 4

//

dFigure MP It is recommended that provisions for continuous monitoring A

of incore thermocouples be included in the plant modifications for

~

natural circulation.

It is concluded that the proposed transition to natural circulation can be accomplished with minf al risk to the public health and safety.

and that natural circulation is the preferred long tenn cooling mode.

T lr R &

-w=~m&

• -2 planned transitione--, N w o b h \\v. S a.y h M c_: _ u;E ~~- z

-- - 5."::: minimize the probability of local fuel temperatures in excess of 1000F. The staff evaluation of cellular convection cooling of debris which could accu ulate in the lower plenum will also be completed in the interim.

J 159 055 v.c

s Table 5.3 Criterit for _ Core CoolinY O

Operating Modes 1.

One Reactor Coolant Pu.p (RCF) Operating 2.

Transition to Natural Circulation During First Hour Following RCP Trip 3.

Natural Circulation Thru One Steam Generator 4.

Natural Circulation Thru Two Steam Generators 5.

Decay Heat Removal High Pressure Jqpeci!ce r.w-)ec.k.

6.

Operatina Limits "

2clicability A

1.

Local Temperature c 1000F 1,374,5, A 6' 3

2.

Average of 4*tw Incore 1 h%, w 3 < Tm4 1,2,3,5, & 6 h

3.

Hot Leg Tecperature > 100F Subcooled 1.3,4,5, & 6 2

~

4.

Nt Leg Tempcrature < 250F All Modes when P>500 PSIA 5.

Hot Leg Temperature > 180F All Modes when Pc15 PSIA 6.

Core AT < 150F All Modes 7.

Hot Leg Temperature Increasa Within One Hour After Reactor Coolant hs p Trip 3

c-Fbnitor Limits Operating Limit Action

~..

1.

Average Incore Themo-couples > Tsat (. Figure 5.2) 2 1

' ~

2.

One Incore Thernoccuple > 1000F 1

2

~ ~

3.

Two Incore Thermocouple > 1000F 1

1 4.

Hot Leg RTD Exceeds l'OF Subcool Limit of Figure 5.2 3

1 5.

Hot Leg Temperature > 250F 4

1 6.

Hot Leg Temperature Minus Cold Leg Te perature >150 6

1 7.

Two or hare Incore Therroccuples Bad Uithin 30 minute interval 1

3 Actions 1.

Return to Pode 1 if possible.

If already in Mode 1, start additional RCP.

Otherwise transfer to an alternative cooling rode.

2.

Validate incdre therinocouple operability by cccparison to otner close therroccuples and by other available means.

If valid, return to Mode 1 if possible.

3. Danger of Local te peratures high enough to melt incor.e instrument structurer.

Evaluate and take Action 1 or other e argency actions as werranted.

O

_l59 056 y,y

W r

= ~

--m.m~ ~ = -

_. _ + -,.,

g

..*.--1' _.-' :.

I.. - '. ' _.g

,,g,.

!..;'.-.**_..=..'t';.'.

....1._...

}

^

_ g e e'

...,.__,2.-*'_'

. L

_-nm

= r= :

--1 m__.

• ..= :r wc : -_.

.r-11. ---n..c ruc -- -

m ---: n.

. r --- n : =_ -. _......

I _ r- _ :

- m, - --- * - t - - ; g.._

. ;(m. E, t t. '_ C k C. h.!~ & *S b5 e-.;

.A

_._ n... _ :

___..!..-.r

_ +

. : n.... f * -- :: -- -

r_-------

. Y. Z_;

. ^ * '..L

. Lt.h*. l* C.A 'ai. S l_.

5t

• t Dn.Y Y q, 5 5 M.

,L,*,t*_.5.

? * ;._ -.

-.? '

^

,';*- n -_. ;: -+ ;_ J; I* +: '- -.---

n'.. _... *... ;

.-l C'  ;-

T..l.^_*

+

..w= !=.. A... ';._ la. -.. _ : :: --.

_,,,;_;;-------+

g; __

j

,g.

. t.-+. _... L. o _ p r ~

^

na

. : ~. :

- b H g-L, W -n T, e_m..c_

r_ _

D_ ;.. :

__ =. _.y m u. u z u =_;=..:. - -_.

.7 c

.r...n = =- '.m : - *

• a ll C L_

2.

a_ ;= t

. _. r= =

! __. f.- ; -

?--

?

~ ~. _ *. _. _^.':._._._::.' *. _..;; : ;.:

y. * *

, * - - - - - -._;_^ * - * *. - - _. ' ' - * - ' *. -.N ~ I'1

- _. o

~ ~ 1 - b 22 : --. m -_ _^* *~ * * ;: d ; ' - - -.

.p.

..; ;'. 4: : ;- :._._,---'..'.g....-_.

-%"7*-'--~;-._

+

..n

==

f l

: ~ ** Q--*". ;rt :..

~ :_ : nid - -.,.

--- Q.~. : :----. u -

y7 :- ---.

- - - - rt_

__: __r

. ap *: : -

_. 9

__. M : :

n g:...

..% : _ - ~ - -

. O :.

~

2

_ q-_,- - t _-

g ;. - e - - -. 4 -. - - -

-r x :::r ;:n.

~ m - -- - %

_V

\\

2_

+

1 f. - + -. : ! ~~ *

~.M - b-h =* "7-- A --.. _ ' U: ~5 Jiu-i.. - 4 *1:'IC _T Ci

-_M -=:

I-

.r.5

• L, " U*- *T T

=

---- - : : - -* _~ :

L

_T? !.. a._ c:.,;.= ;

m n = : =:._:2_'

.= - =

u. ;.==.=-- _:a

^==

-- = =_** : I.n T.;;

. := =.x ; -. _.. -*..

,?..

i r--

g-;-

_;=_.=

- ^

=..c..-

--i..=

• =:*....

• --T-*_

. _... n :- -

--T--. _.._..--*--:';

r ~'.

~

I.---.. - __ - * --

• M ; ;. _._ ; _.,. a' :f",.. -,

* * ' ; r b......

~!

- * - ~.:.:1

--.:2;:n C;:.

'1-"

!".'

=

===.4

--: ===:==. ;

..;. =;. ;;;;- - -

.- ~: _=:.-:=...-..

.. _ :==zz : _-

- =.=-

- m-c. _ - + _

.r ;' *

n_I_7__ :

. _... n ~.~ A *

• n:c.

1 ; : ;- :-*r*;; *;.

g-y+I _- u-- n:.--

• n.; if._..... _. -. r '_

n._; ;. * - * :.' n r.. _ _.. :. J -*: - --t---

.- * -

• _- :

• 1

-O

- - ~

- 1 ! ' * ;';.;*

C** T*- h.* _ - - * ' - - - * ~ _ -- :--- - -..

. rw. -..' y.. :--1.

_. ;. _.z.

=: ;

-.*.*n:.-4-*~~~.

{

-._ _ _ c *. -'.:2n

.1_: _.

_. =. n.u. t n_*'.:rt. -.**... r ;r ;c- :.

._._; -_ r... r.: _.... -.... U }

• 1'

_ _ =.

4 q..

=.

_ _ ; =.;.; _ _ - = cn - - - - : : __2_.-. : _ = _ _ :.1._;.c _

. c r 2-

,._2.

. un - - - - --.r n... * +-: _;___..--_=-t 1.: _ :-. :.n z:*'

.. * *... ;_; ' ^.;.

, *. ^ ~ *.

..: -- ' _.i _ _ L-e - _._ ; --* ~~.. * ::_ _ :'_ TJ. Z *

.n _. _ _-

• n m.

_ _ _..... _ _..... ' * ~ *

-^:f-**..-

I- - *

_.J.

• "- ? *n*.:._w 1

- L ~ T: 2!

.___ ~.. _;- *

.;"*C*:;_'-*---_'*_~~-r=

_ _...::-~*_ :~' ~ *:;'"';r T.;;.::

+--

1-__._

'^ *.._:_-_

..:..~.~~~4

~

• ?_.*

.. * ~ * "

g f

_ f y_ _L C L - ! * -.:-==:--=--

"--:...**'*r*

• ^ ' - - ' *^':"

-_.J__-.;._.

.. - -, -=, = -. :

-- -* *- ** ^* 'J 9:: ~~. '* =':: ^*.: -, -- m : :

=-: ; :=.

-- = :.-

.=t r

.. _. =2-,-

n' f.

3

..MI.:. ::Z -'

_.~ * :.*

.. d C '* -' r***. !i

.E I

- _'.:.- * ~ L :=

__ t : -* : - * * * ^

~7-

-r==-....

arr -

. = - ::_... _..27L1

= -_.. _ _.. _. -.. $ aa_

{% - _. -

_ m.; y "*: ',' **.

1 L;u;**:

- -D I

• ^~:.^ * ; *.*:1..: ' '_LL

_..._.::ur.=_-----....

... " ': ' - T"u* : : ~ : **_3 4_2 ;.~'~' : ',.' : ^-^

_-. m,-- m.

. n._

2

":*.;._*.~-*,'---*J-*-~:

- ^ ' * * * * ^ *

.M

_ f. : -...,. ^_ ! : '. * *. -* :--~; ;

iC __ _ _'_--

• m_-.

=*J-

'**^!*

u =. "- * ; _.~m. - _

.=. y

=- :=..:

-,_._. _; - - - -- -- ---- = t._ : = : =,= r : --==_.r--

. = _..

. n:_

.=- c : t-

..m

- - = v.:.:..:.._ _ _

u._._

~

...z

. ;G = _.~ * - * *. * ^.-- * --.C--*

z L ; ::.. ? \\ ^ :_. _..: n :

• c ;~

.n

.. n unt-* n;* r..!

-* : *.- ^ ^ - ^ ~ ~ ~ ~ - * ~ - *_.

=:-. -. r : r --

=1:_.

c.=

x

- - -- --- ;:-r :.r : ;:=. -: --

--~n =. :. - t q

}.,r.-

4-:_2-

_22=uu-nx :.c nme=2

= :=: 7r -

nxu.2:: c r:7.n : -.

r x.u*c-mr=_rx:=2

..y

- *:--.; 1; : ; ~ - --* ]*# q..___r{.- :':::

. _ _, T -- - !

! _ : : : i;' l'i% J~ ;** T_. O J - 7 _.. _

- - - : -~ 1: r J--* * : r \\. ~~~*:^..

,u, x = -

....m.

n' *=. :r.: :._._ _ _ y: by^

• C *:s

• ._:L T

g;. n--e. c -- ; = : __.. -== =:=: ::==;:n. _ '

-2.==.

tv

- - - = =.

ua. =

r:.n ;h;= b '1__._._

~*~

.== : * =;=

r*u;.-*****---*

r ;r u"

n ;_ _.

-- - ' iz n.--

• ~*

E r

2--'*.-~C'._r--

> n: r = r f'A.s-4.

---

qn_ :

nr: = _

-- - ~. n nr - -- -

. - L__.

- u. _=r,2,= ;:

.. r;.c : : =

n

== w

..: nwd: :w_.#.. __ _==s% :m.3 %1:r.41

_.m.=

== := = :==.===2.

=== =-r P s.

... tr.+

:::r=

=r===:=-:=,r:1... _.. _ _ _.-======:

. 7 :_ : :__.._ _ _ _..... _. n a

_ =_=.

-- : - 1,./ =: %= 1__--*._..a

= :_ - __ - _A ;1

=-

1

% "=

ur

~ ~ ~ -

==:

m u * - J r :.__=".; _- : J.

a. :

Y'

w=.,, m=: u.a -. _M :9=.:j 7:-. ~ ~

-- - * - ".~- : =2 * : 7-*. r _ _ * ;t * -: =

a== r.L'20~.:;:--::*-

-^--

tt -

..._ g

_: =u _:

-.== c..

=

,=n::=. =_.r c_uc =t

_=-=r-

.\\-...-..._..== m;m f-.

r =.t:

~

u:_

m r

%*-j rr;m= :2_

.....=.;_p2. a: 1_. _ -

_ - c :=c n

_ __; 2 rr u ___..

._..w

n ya::=:__.__=_ 2.:c_ : _ p--:u c__a_- - --. --c

nne -

= urr := rz:, n =- ---

=um a n.e,$_ -3

.a

_-.-= u =:_= = :=.r-~ =.c 2.:

rr/ :. m e __::-.;=c; n =r r -. b_r n,r.,

_

n nn a: - :ena

. c =r:

- : =n a 22n--.: rrn~E=:r =n=+r--

_.m

.c::

.R: _ ;p. 2 _--=_ :

n_.

Q :, p n =_ = a

-.:r

= =t=_n n-m -- r -

1: cz- ::r:_: : : :

c.

__ _ _ - _. __ - : m c :

---.,. ~

r-n.; _. _. :

.o_

_. =. _ _.. -. _.. = u=,=_=.=_.:=._ ~.. :.. :,n = : =._...

=_r.._a,====_.,

.=p. e= = 3 _ : =_. : :, r. _ :. x _.

3

.7

. m. m.._m. = := -.2; p.:.

y

.y

n~ ? ' ;*_ _ - : M-*-' t -' 4 : ---' + _~.~ :!:

,w Z :-

• _;C A

'7.L F G Ls. s ~ f - - ".-_ _ ~- u n __. ZC

;

--- C:n- *-- : ~ ! ! *.* T r **:-~:1.

g:-.r:.:g n n: _

Car m % :---~ r

-2

+m

__.: 2

. - rx-t em. ;rr a ; n ;;: c= 2 = n c- -- W-

• .u a c :-

n = = :. --_ 3.r_:_..c. _ a.- :.r=- W..

% r ----

_-,c -- : -: :

.--u r ra r a _.___

.-.--s._..

q - -- m-- - : E.: 23.i.: =,:.s. : ::;r :.au

= = = = - -

=o tu___

..u...

22:= =:=:x.

-= n.cc:n na -_ =- n.__

n-

n wt.------

-- u _ -- c _:

r-- -. Luu =

2. = =n an__.u w -

_:s

1= t = ---

2 :a rn. _ n : c r : rn - :r===- r-m.;;maan:1

.a

-- = -

t r2-m a;;

r

=====-=====:===.-=ru===__;==.

ro 4.

_. _ =.=. =u c -- = : =...- --

- - --: -::=.

. : : : --=.. _ a= r ~.._n : aa

--- -- r p -

.;w: * - +

.a p-c

. y-

_ : y. n -==j -

2-.2_

-~ ; n :- y : a:.:- + u _. 1r: ::_2q n;_: _ +: 2..

r:

ru u_

.1.

2 2 = r - : m _ _:

1

. _., ~ ~ ~ -

' ~ ~ *

.u 2 _a u.. _. - - - - -.ac. :n 2.3 - r":1;.' r:,.

2

. :. --. n _- ;c.'.h~ *~~ * ' ::]-j

.;___.-_=U

f:;*

! ;-~

• rr.. _.1.-* ~. = n - : _.- --[

.-*--__.._r-L

- n ~_ g.r

+c--

( e/* l r-r

.f

-m._.'_.r' :. b. :. =- " ". _.. _ -. 1 a_--

• : 2.

c;.

--:- m m _

-=

-

i M *

=== _ = m. = = = ~ ={ -

• _- ::m.-

... _4 _m== = r_c~ f A*'. q.{ %."..

k "T;6...

^-

r -- ! L ' -

4 3

}

?---

.:1

... __ c. -.

+.g

.s

. : x.-

a r =.

.m __.= _ m - - _-

m g.a. e$a.

,;a

. 2 2 :- =r -- -

rn e -

• Tl?

---4 L;;;.-

_ ; P_ _. y -* -' *- ;

.- r 7, - -

-_ ; : _-- 1 -* ::' -

. ' - " -.._.._v.1.'..:..-

rg-

_ -- m

__r.

--- n ::.-

_ =. -.. r. _ a w :

,. t :. _..::-.:u. =__ _3

_ _ ~--- - ___

- -_nu..m... _...._m_ {* r. h.

..u._

_. r - - (g. -

r g

_,,, _, rey:.

~a; p.

,....-....- n_2-c -

.. _. - _. - +, m : = n _ r h.

.nt*. _ _ _.;2 m_. 7 >g & ~ i r.:r~ r

..n=.

H,.~ - ! -

.._.x--.g._.

O ".)-

. _.r.__-r_=_.._..._:

t

u u

• 2 4 ^

Q--

^ L ' ' -

(n ;..

--..;_.7._.

-';7 J

.:._ -- L - ;

n ' >.

r. g.- ?

.1".,-

P"

._n.-. _ _.. -... - O.,y -

..(-

U r

3 t

= 'q - d -- - k: - - __ g = x = t:3 i.- Q-. Q = M h:

== - t

.. _.. _ _ - -, _,- wt._._ q

=._.=r-- t_ 3

_?-^- a h

.., =.

pn

-f]

- ( --

g _

j_

.h

' '...-f

..g*

. ' - - ~.

s

• [

.[ "'

_ - ~ _ - '

2

.--r-

= * -

---

[-*

t g _

_j[

...?;

.- -- -. mg.r r,

(T (

.. f,.

,._---;_n_...

-- J /,.

! 'l a.

I

J

\\

r.

h

~ - - -

.m.

• m}

,T 4

A

.a

. - +

d

!.?

(4 4

<3 s

=. _ ~

e "

~~

+.

-.,-a-.

..--.e e" - - " " ' - ' - ' ^

~'

" - ' ' - -