ML19220C362
| ML19220C362 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 07/18/1978 |
| From: | Taylor J BABCOCK & WILCOX CO. |
| To: | Varga S Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19220C361 | List: |
| References | |
| NUDOCS 7904300476 | |
| Download: ML19220C362 (12) | |
Text
Babcock &V!!!ccx m e cem m ocnc,cuo P.O. Ecx 1250. Lynchburg Va. 245C5 Tefe::ncne:(SC4) 254 5111 July 18, 1973 Mr. S. A.
Varga, Chief Light Water Reactors Branch #4 Division of Project Management Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Mr. Varga:
Attached is additional ECCS small break analyses for 35N's 177 Fuel Assembly Lowered-Loop NSS.
These analyses are in accordance with the small break model as approved in BAW-10104A, Rev.
3, "35N's ECCS Evaluation Model," except for two of the proposed modifications in my letter to you of May 26, 1973.
These analyses differ frem those in my letter to you of June ir, 1978, in that the proposed Zaloudek Corre-lation modification was not utilized and two additional breaks were analyzed.
These analyses, therefore, are intended to
. replace those of June 19, 1978.
A power level of 2772 MNt is assumed in these analyses.
Credit is assumed for operator action as described in my letter to you of May 1, 1973.
Break sizes of.04,
.055,
.07,
.085, 2
.10 and.15 ft am examined.
These attached analyses, along
. ith the break analyses in BAN-10103A, Rev.
3, "ECCS Analysis w
of 35W's 177-FA Lowered-Loop NSS," constitute a complete-spectrum of small break analyses which we believe to be wholly in conformance with 10 CFR 50.46 and 10 CFR 50, Appendix K.
Your expeditious review of this submittal is requested.
If vou have any questions, please contact me or Henry Bailey (Ext. 267S) of my staff.
Very,truly yours,
/
a/
,u Jae.es H. Taylor Manager, Licensing JHT:dsf Attachment
~
cc:
R. B.
Borsum (35W)
'7 8 0 4 3 0 0 q s 91
- O ',
Tre e3ec ck & w.ic:x cemes, I n:a::Lwee 19s7
1.
Introduction Analysis of a spectrum of small breaks at the pucp discharge has been performed for B&W's 177-FA lowered loop plants. The small break evaluation model described in BAW-10104, Rev 3, "B&W's ECCS Evaluation Model," along with two of the pro-posed codifications described in the report of May 26, 1978 (J.H. Taylor to S.A.
Varga) was utilized for this study. Operator action is used to achieve suffi-cient and balanced flow through~ all four high pressure injection (HFI) lines.
The operator action is described in detail in the report of May 1, 1978 (J.H.
Taylor _ to R.L. Baer).
The analysis contained herein, coupled with the analyses of BAW-10103A, Rev 3, "ECCS Anal,ysis of B&W's 177-FA Lowered Loop NSS," provide an appropriate spec-trum of breaks for the evaluation o'f a s=all leak transient. The results of the analyses show that the piants can be operated'up to a power level of 2772 ISt within the criteria of 10 CFR 50.46 and Appendix K of 10 CFR 50.
2.
Method of Analvsis The analysis =ethod used for this evaluation is that described in Chapter 5 of EAW-10104, Rev 3, "B&W's ECCS Evaluation Model," along with' two of the modi-
~
f$ cations described in the report of May 26,1978 (J.H. Taylor to S. A. Varga).
The two =cdifications utilited were the tuo node inner vessel st=ulation and the phase distributional cultipliers for bubble rise in all control volumes
' within the reactor vessel. The CRAFT 2 code is used to develop the history of the reactor coolant syctes hydrodynamics. The CRAFT =odel uses 20 nodes to simulate the reactor coolant syste=, 2 nodes for the secondary systen, and one node for the reactor building. A sche atic diagras of the =odel is shown in Figure 1 along vith the node descriptions. Control volumes (nodes) in and around the vessel are.all connected by a pair of flow paths to permit counter-current flow. The breaks analyzed in this report are assuced to be located at the bottom of the cold leg piping between the reactor coolant pump discharge and the reactor vessel. The Wilson, Grenda, and Patterson average bubble rice model is used for all nodes. Within the reactor vessel, however, cultipliers of 2.38 and 2.0 are applied to the calculated bubble rise velocity in the core node and the remaining vessel nodes, respectively. The justification for the use of 2.38 cultiplier value in core node is given in Appendix F of BAU-10104 The report of May 26, 1978 (J.H. Taylor to I.A. Varga) justifies the usa of a cultiplier of 2.0 in the downconer, lower plenum, and the upper plenu regiona.
Q1
'OO,I idu
.. ~,
~
The fo11s ing assu=ptions are made for conditions and syste= responses during the acciwot:
The : 4 actor is operating at 102*: of the steady-state power level of 2772 a.
Wt.
b.
The leak occurs instantaneously, and a discharge coefficient of 1.0 is used far the entire analysis.
Bernoulli's equation was used for the sub-c6cid portion of the transient, while' Moody's correlation was used in the tva-phase portion.
No of ilte power is available.
c.
d.
The :cactor trips on low pressure at 1900 psia.
The so.fety rods begin enter ng the core af ter a 0.5 second delay from the e.
ti=e rhe reactor trip signal is reached.
f.
The R'T pu=ps trip and coast down coincident with reactor trip.
g.
One complete train of the e=ergency safeguards system fails to operate, leavi..A two CFTs and only one HPI and one LPI system available for pumped injee : ton to mitigate the consequence,s of a cold leg break.
' h.' The 37.x Lliary feedwater (FW) system is assu=cd to be available during the trans.. c n t.
Its =ain function is to re=ove heat from the upper half of the sten generator during the initial stages of. the transient. When the sec-enda r
side of the stean' generator beco=es a source of heat to the pri=ary system. the assu=ption of auxiliary R =axi=1:es the energy that must be relie ned.
1.
ESFAS signal error band is considered in the analysis to signal the actua-tion M the HPI systes.
J.
The /e ak linear heat generation rate in the hot pin is the =axi=um allowed by tN technical specifications at the 10.5 ft level.
- x.. Opera rar action is taken to increase the HPI flows to the intact cold legs at 10 minutes folj ovi: g the ECCS initiacion signal. This action is ex-plai:. I more fully in the Pay 1,1973, report (J.H. Taylc r to R.L. Eaer)
Since the.: RAFT calculations showed partial core uncovery for so=2 of the 2 breaks, a FOA'd analysis breaks, 3P 'ifically the 0.055, 0.07, and 0.0SS-ft was perf re rd to deter =ine the inner vessel =1xture height. The FOAM t i p, ]
iVs
void fraction in the lower regions of the core and, similarly to the dis-cussion in ites b above, will result in a conservative mixture height.
The heat-up calculation was performed using the TEETA code in the manner de-scribed in section 5 of BAW-10104. The following additional assu=ptions are utilized in the THETA evaluation:
The power shape of Figure 2 was used with a radial power factor of 1.67.
a.
This maximizes steam superheating and sets the peak local power at 10.5 f t at the technical specification LOCA limit.
- b. ' Coolant floc and mixture level were taken directly from the FOAM calcula-tions. As discussed above, the =ethods utilized in the FOAM calculations result in consertative values for these parameters.
End of, life pin pressures were us,ed to conservatively predict the inci-c.
dence of fuel pin rupture.
3.
Break Soectrum and Results Topical report BAW-10103A, Rev 3, presents the analysis of a CFT line break, the.0.5 ft2 break at the RC pump discharge and the spectrum of breaks at the
.RC pump suction. As s'hown in that report, the results of those analyses are wh'olly in compliance with the criteria of 10 CFR 50.46 and Appendix K of 10 CFR 50.
Those analyses are still valid and conservative in light of the i=-
pact of the model odifications.
The report of May 26, 1978 (J.H. Taylor to S. A. Varga), describes the i= pact of the nodifications.
In the present analysis, breaks of 0.04, 0.055, 0.07, 0.085, 0.10, and 0.15 ft2 at the RC pump discharge are evaluated.
Figure -3 shows the RC presaure response for each break. As shoun, each accident initiates CFT flow within 2000 seconds except the 0.04 ft2 break.
Figure 4 shows (CRAFT) mixture height as a function of time for each break of the spec tru=.
As can be seen from the figure, minor core uncovery was calcu-2 breaks.
For the 0.04, 0.1, and laced for the 0.055, 0.07, and 0.035-ft 0.15-ft2 breaks no core uncovery was calculated and, thus, no temperature ex-cursions occur.
The 0.04 ft2 break achieves a match up of ef fective ECCS (the H?I injected into the intact cold legs) with the core decay heat and the RCS retal heat at 3000 seconds.
The core has a mixture height of 13.5 feet at this time.
After g1 4
i U 'i.
..n..:-.m..
n~ w ~ _ _.
calculation included all sources of steam production within the vessel, i.e.,
steam production due to decay heat, flashing, and pri=ary =etal heat.
To ex-pedite the FOAM analysis, the distribution of the stea= sources was chosen to minimi:e the ec=plexity of the input calculations and, as described in the sub-sequent paragraphs, results in an underprediction of the swell level. By un-deresti= sting the core mixture heigt., the core stea=ing rate will also be un-deresti=ated; thereby resulting in an overestimation of the s' team superheating
~
and the peak cladding te=perature.
The axial power shape shown in Figure 2 was used in the FOAM calculation and was i=plemented with a radial peaking factor of 1.0.
Thus, the resultant =ix-ture_ height is representative of the average channel conditions and is con-servative relative to that for the hot channel. To utilize the power shape in FOAM, the shape was divided into 26 axial nodes.
Steam production due to pricary =etal heating and flashing within the inner vessel was assu=ed to have a distribution similar to that for decay heat.
As such, the co=plexity in the input generation for FOAM was reduced to finding an " equivalent decay power" which would generate the same amount of steam as that which is produced from all sources. Use of this steam production shape results in conservative core mixture heights for the follcuing reasons:
a.
When the core is uncovered, some of the steam production due to primary
=etal heating and flashing would not be used in calculating the cixture level. Thus, the cixture height would be underesti=ated.
b.
By using this shape, the void fraction at the core inlet is zero.
In ac-tuality, due to steam production in the icwer plenum and the subsequent bubble rise into the core, a void fraction will exist at the core inlet.
Furthermore, this initial core void fraction results in additional bubbles rising throughout the core =ixture and increases the entire core void fraction. Since the assumed shape underestimates the core void fraction, the mixture height is underesti=ated.
c.
Since the axial power distribution is skewed towards the top of the core, (see Figure 2) the =ajority of the steam production will be calculated to occur towards the outlet of the core. Realistically, the total steam I
production due to primary metal heat and flashing would be skawed towards I
the bottom of the core. The distribution analyzed will underestimate the I
i hk l,
i i
3000 seconda the mixture level vill rise in the core due to e.tcess HPI.
For breaks s= aller than 0.04 ft2, the match up will occur at approxi=ately the same ti=c and the core =ixture levels will drop slower; thus, for all snaller breaks the core will re=ain covered cnd the it?I alone can =itigate the tran-sient.
In perfor=ing the analysis, the historical small break spectrum (0.04, 0.07,
2 0.1, and 0.15-ft breaks) was perfor=ed first.
As shown by Figure 4, only the 0.07-ft2 break resulted in core uncovery. To further assure that the 2
worst case had been obtained, the 0.055-and the 0.0SS-ft breaks were analyred.
These cases resulted in some core uncovery but less than that for the 0.07-ft2 break. All three cases were analy:ed for temperature response by utilising the THETA cede; Figure 5 shows the cladding te=perature responses. The peak 2
cladding temperature for the worst case break, the 0.07-f t break, was only 1092F which is well below the 2200F criteria of 10 CFR 50.46.
Thus, the analy-sis de=enstrates that-BrJ's 177-FA lowered loop plants can be operated at pcuer lavels up to 2772.'27t and satisfy the ECCS acceptance criteria.
9 Iy1 i -) lv L..-
Figure 1.
CRAFT 2 Noding Diagram for S=all 3reaks
&l cri 3
21 V
7.
13 i
16
[
4 Ss t
D Q
tr M
22
.._ s s
_gg
\\
P f
.hs 6 lC@ '
@g 7,
u.La2 '.
G G
{,_
"IU:
w la-f 9
.3 is i
E T
O
"' -f)
@T g;)
.unes., : n.. : n..
7 a.e u e,. m..i_
0 _I C b
@ ::.t::. :J:::...
@J l
Q
,,,,, i.....
- t... i. a n
r.
c i.in
- i.
a...a
_ _w
- cd a h.
Identification Path No.
Identificarfen 1
Downer,er 1,2 Core 2
Lcuer Plent=
3,4.13,19.
Hot Leg Piping 3
Core 5,20 Hot Leg, Upper 4,14 Eat Lag Piping 6.21 SG Tubes 5,15 SG & Upper Head 7,22 SG Lover Head 6,16 Steam Generator Tubes 3
Core Eypass 7,17 Secondary. SC 9,13,24 Cold Leg Piping 8,13 SG Lower Head 10,14.25 P u=e s 9.11,19 Cold Leg Piping 11,12.15,16,26,27 Cold Leg Piping 10,12,23 Cold Les Piping 17.31 Dc.mccmer 13 Upper Devncocer 23 LPI 21 Pressurizer-28,29 Upper Downce=er 22 Centairmen t 30 Pressuri:er 23 Upper Plenum 32 Vent Valve 33,34 Leak & Return Path 35,36 EPI 37 Contain=ent Sprays
/
iL, A
.. -.. - -. -. -... _.... ~. -
e n
V OU s
~
N i
6 A
\\ s
's s
s:
' 'b..
t-)
N 9
N s-]
B l
D 5
) v
~
- b.,'.3
(
w s
-g k
y q n Nl S
-3 sN ts
\\.s p
\\
N \\
N
,s' 1.
e N
I N
's h
s W
+s N N
.y d
S Y'
W
%g n
s y-g t
x
,n.
4' s
s s.
~
">y,' A=' ' /.,W P t"//,? t-f 3 -
% _w.
O
- i, ?!
A
/
t us
a
)
i l
i l
a-I t
n
/
8 i
..t
?
I
~k k kk.
/
.I I
nu n
,a u*
Akt
~t l
i TES$3b i
< =c o., s t
I 5.'
)
'3 I;i.f ll.
I
~~
I
/
.R A
ll l
I Il 1
e
,f I!
j c
W i
.I i :
[
I
\\1 i
s I
l o%
W 1
.e '
.I 5
l
/ :
s m
g rqx 1 :
l
\\
//
/
,D x
y I.j I
% y,
3 C! N Ns f *-
./
N k n
/
e s
N
-a~
C n
l l *l ll i
I:
k 4k i.:
I 8
/:
'4
/.*
[
ll 1:
f I.
A e
g.
g l
s:
~r I:
-. i.:./
llo.;'
Cs r
C
)
5 e
&'f/
~
t
~
m
"< 5x>n.w !
g 91
] Q ~>
9 f"
I ag t \\.
I I\\
'\\
l I
I I
\\
I I
{
l
, f I
\\
q r
.I l
l
. R I
m-I l
9
'l
(
o s
c y
i
\\
n u n
~,e,N n
u~~
i
/
A s s%g l
\\
R
,224ev w
/
s
= cae I
I 0 *i 4 Q^(
4' I
n I
- I
/
l l ll
/
/
I
.l -
/
,.h
[
I l1
,/
i v
~
.f
.)
l l
I i
I
/\\
l I.
/
l l
/
./ : J l
n l
/ \\/
l
./
.i pu i
/
/
/':
"s4 I
i
/
i f
k%
i j j
t/
/
/ </
O t
m o
w i,
M n
,4 x
./ b
I kE\\
0 g
l \\/
/
W.
k.s
\\/\\/
\\
% ?' R
. i I
I h $
^4 2 V d. -
A./
t.
/
b x kk ll\\;*
I
! ' \\ 'i
./ D f\\ M /
0
~%
i
!N N.W Y.A
,t
.7. O F
.y_
4
.e i
2.4 9
q h
_ _ +.
-C~
.- p A
'~~ T_. :_-.f D
Q S
g N
n,
,,n isow no.uw 7I i.v
e
_ _ - ~.......
/
N.,r
.i
/
s
,.A O
s Jj
~%
/.
/
l s -
t e
\\
1.
-..p.
, N.*.
i4
.. ~
s
.!""'""*==._..'m.
l t
/
I
/
- q q-
/
,.f 6
v a
9 i
s M
s I
k.
l t
i s
N
.p l o'
- e J
j s.,
E
. _. f g
e, l
I
. 5
'r%
o.
t
(-..._.
s y
s
~.
.\\*
.~
g i l ^%
f.
r 1,
~
,~
n s.
w s.
.e g...
a b -
i t
L.
I..
.....h a.'
1 i
e.
n
%/
,i
,s e
. G 2.-
. ~
" ' - ~ ~ ~
.g
~
~_
-^
0
.-s t
~.
-e
,.* % r.g.,,., ^ :!,.
a g.*,.
,4
,'{\\~ ; ~^f s '. ' I:j j
' s 4
a
-M.3 '/,-j.i i 4 [N k.,'.-
9 J.4 A
l 2,
,j
/
'p f. : :.
., [..
.3.
5 '
5 d i b dh'h c n
4 3 1
'l f
I a
- 0 0
8
-.-==.-e.,-
_m..
- = - -
.e a
6 he
-.6
,q y
3 4
1 i
.\\
l I - - - -
g
/
i l
N
/
i N
f l
j l-...........K.,
I i.
I
~
i.
F-l t
,I i N.,.
~%
i f
j
=
%).. -.i~,.
i..
/
,I
'. -.. M.
l
+%
ma"'"'"
l, n - - -
g-g
~ -"**
g g
j.
l i
"s.
~,.
w
. s s
l?
}
. 4...- -
l l' 0 s
9
**
'u' f
6 i
Q,
~ --
6 4
- o jf'
.b..-
t N
i L
i.
.o e
Y'$
h t
t
__. h o
.-~
c.
/
,7 s
t n
i 1 )
o f
y. L m',-"
/
i e y
o. d ).$ l
)'
- '
- ) A f' ' ? y
'. FlD (a Q q
(
^ft$l'.,. 7l.u.. Q,y;p l
m, e
e