ML20078R046
| ML20078R046 | |
| Person / Time | |
|---|---|
| Site: | 05200004 |
| Issue date: | 02/15/1995 |
| From: | Quinn J GENERAL ELECTRIC CO. |
| To: | Boehnert P Advisory Committee on Reactor Safeguards, NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-NUREG-CR-2574 MFN-022-95, MFN-22-95, NUDOCS 9502220180 | |
| Download: ML20078R046 (1) | |
Text
C 1
O GENuclearEnergy J. E. Quinn, Projects Manager GeneralElectric Company LMR and SBWR Programs 175 Curtner Avenue, M/C 165 San Jose, CA 95125-1014 408 925-1005 (phone) 408 925-3991 (facsimile)
February 15,1995 MFN No. 022-95 l
Docket STN 52-004 Document Control Desk U. S. Nuclear Regulatory Conunission Washington DC 20555 t
Attention:
P. A. Boehnert-ACRS Staff Siuhject:
TRACG Separator Modeling
Reference:
- 1) GE letter A11WNo. 018-95,J. E. Quinn (GE) to R. W. Borchardt (NRC), "Apfnvach to Achieve Closure ofItems Related to the GE SBWR TAPD, " dated Febniary 14, 1995.
- 2) Report NUREG/CR-2574, "BWR Repll-Repood Program, Task 4.7-AfodelDevelopment, TRAGBWR Component Afodels",
Published September 1983.
i The attachment to this letter provides the GE response to item No. 9 of Attachment 2 to the Reference 1 letter. The attaclunent to this letter is a copy of Sections 4, Steam Separator Model Development, and 5, Steam Dryer Modeling, of the Reference 2 report, Copies of this information were requested by the ACRS Thermal Hydr;mlics
. Subcommittee at meetings held Decembcr 15 and 16,1994, andJanuary 10,1995.
Sincerely, i
~ ~/
df}
l f ';u es in, Projects Manager VgRintf BWR Programs
Enclosure:
Sections 4 and 5 of NUREG/CR-2574 l
cc:
- 1. Catton (ACRS)
S. Q. Ninh (NRC)
J.11. Wilson (NRC) 4 i
9502220100 950215 PDR ADOCK 05200004 1
A PDR 3)Y
Enclosure to MFN No. 022-95 NUREGICR 2574 l
EPRI NP-2376 GEAP-22052 l
l BWR Refill-Reflood Program Task 4.7 - Model Development TRAC-BWR Component Models l
I I
l 1
Prepared by Y. K. Cheung, V. Parameswaran, J. C. Shaug 1
l Nuclear Fuel and Special Projects Division Gxneral Electric Company Prepared for U.S. Nuclear Regulatory Commission and i
Electric Power Research Institute
{
l and G:neral Electric Company l
l g
lbl5 CC)] 6 3 ]ff, u
m NOTICE This report was prepared as an account of work sponsored by an agency of the United States Government, Neither the United States Government nor any agency thereof, or any of their employees, makes any warranty, expressed or implied, or assumes any legal liability of re-sponsibility for any third party's use, or the results of such use, of any information, apparatus, product or process disclosed in this report, or represents that its use by such third party would not infringe privately owned rights.
1 l
l 1
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1.
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NUREGICR 2574 EPRI NP-2376 GEAP-22052 R2 BWR Refill-Reflood Program Task 4.7 Model Development TRAC-BWR Component Models Manuscript Completed: April 1983 Da'e Published: September 1983 Prepared by Y. K. Cheung, V. Parameswaran, J C. Shaug Nuclear Fuel and Special Projects Division General Electric Company San Jose, CA 95125 Pr: pared for Division of Accident Evaluation Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission Wcshington, D.C. 20555 NRC FIN No. B5877 1
and Eltctric Power Research Institute 3412 Hillview Avenue Pals Alto, CA 94303
)
and Gsnsral Electric Company i
San Jose, CA 95125
LEGAL NOTICE This report was prepared by the General Electric Company as an account of work sponsored by the Nuclear Regulatory Commission, the Electric Power Research Institute, and the General Electric Company. No erson acting on behalf of the NRC, the Institute, or members of the institute, or General Electric Company:
A.
Makes any warranty or representation, express or implied, with respect to the accuracy, completeness, or usefulness of the information, contained in this report, or that information apparatus, method or process disclosed in this report may not intringe privately owned rights, or B.
Asst s any liabilities with respect to the use of, or for damages resulting fron.ne use of any information, apparatus, method or process disclosed in this report.
l l
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AESTRACT TRAC (Transient Reactor Analysis Code) is a computer code for best estimate
]
analysis for the thermal hydraulic conditions in a reactor system. The development and assessment of the BWR component models developed under the Refill /Reflood j
Program that are necessary to structure a BWR-version of IRAC are described in this report. These component models are the jet pump, steam separator, steam dryer, two-phase level tracking model and upper plenum mixing model. These models I
have been implemented into TRAC-B02.
Also a single channel option has been developed for individual fuel channel analysis following a system response calculation.
111
f 4
CONTENTS Section h
1 INTRODUCTION 1-1 2
JET PUMP COMPONENT DEVELOPMENT 2-1 2.1 Description of Jet Pump Flow Regimes 2-1 I
2.2 Model Development 2-4 2.3 Mixing and Nozzle Losses 2-9 2.4 Other losses 2-10 2.5 Verification 2-12 2.6 Conclusion 2-18 3
TWO-PHASE LEVEL TRACKING MODEL DEVELOPMENT 3-1 3.1 Model Design 3-1 3.2 Verification-Test Cases 3-10 4
STEAM SEPARATOR MODEL DEVELOPMENT 4-1 4.1 Steam Separator Model 4-1 4.2 Carryunder and Carryover 4-10 4.3 Checkout Calculations 4-16 4.4 Conclusion and Recommendation 4-19 5
STEAM DRYER MODELING 5-1 6
UPPER PLENUM MIXING MODEL DEVELOPMENT 6-1 6.1 Model Design 6-2 6.2 Verification 6-20 6.3 Conclusions 6-25 7
SINGLE CHANNEL OPTION 7-1 8
CONCLUSION 8-1 9
N0hENCLATURE 9-1 10 REFERENCES 10-1 v
r" ILLUSTRATIONS
_F,1 ure Pg 3
1-1 TRAC-BWR Structure 1-2 2-1 Jet Pump Operation under Normal Flow Conditions 2-2 2 2-2 Jet Pump Flow Regimes 2-3 N-M Characteristic of INEL Tested Jet Pump 2-6 2-4 Control Volume Around Mixing Region 2-7 2-7 2-5 Comparisons of Predicted vs. Measured Discharge Flows in Flow Regime 1 2-14 2-6 Comparisons of Predicted vs. Measured Discharge Flows in Flow Regime 2 2-7 Comparisons of Predicted vs. Measured Discharge 2-14 Flows in Flow Regime 4 2-8 Comparisons of Predicted vs. Measured Drive Flows 2-15 in Flow Regime 5 2-9 Comparisons of Predicted vs. Measured Suction 2-15 Flows in Flow Regime 6 2-10 Comparisons of Predicted vs. Mbasured MN Curves 2-16 f or INEL Tested Jet Pump 2-11 Comparisons of Predicted vs. measured MN Curves 2-17 for Steady-State 2-Phase Tests 2-12 Comparisons of Predicted vs. Measured MN Curves 2-19 l
for BWR full Scale Jet Pump 3-1 Two-phase Level in a normal void Profile Situation 3-3 3-3 3-2 Two-phase Level in a cell below e void fraction inversion 3-3 Two-phase level in a cell above a cell void fraction 3-6 inversion 3-8 3-4 Rising level approaching the cell boundary 3-5 Falling level approaching the cell boundary 3-8 3-6 PSTF Nodalization 3-11 vii
n ILLUSTRATIONS (Continued)
Figure Page 3-7 PSTF Level Swell Test, Axial Void Fraction Profiles 3-12 3-8 Simplified BWR/6 Nodalization 3-14 3-9 Void Fraction In Downcomer Levels 3-15 3-10 Steam Dome Pressure 3-16 4-1 Typical Types of Steam Separators 4-2 4-2 Schematic of the Separator Model 4-3 4-3 Comparison of Test Data and Mechanistic Model 4-13 Prediction on Carryunder for 2-State Separator 4-4 Comparison of Test Data and Mechanistic Model 4-14 Prediction on Carryover for 2-Stage Separator 4-5 Comparison of Test Data and Mechanistic Model 4-14 Prediction on Separator Pressure Drop for 2-Stage Separator 4-6 Comparison of Test Data and Mechanistic Model 4-14 Prediction on Carryunder for 3-Stage Separator 4-7 Comparison of Test Data and Mechanistic Model 4-15 Prediction on Carryover for 3-Stage Separator 4-8 Comparisons of Test Data, Mechanistic Model and 4-15 TRAC Results on Carryunder for 3-Stage Separator 4-9 Simplified BWR/6 Mode'. for separator test case 4-17 4-10 Void Fractions in downcomer Levels for the BVR/6 4-18 Steady-Stage Calculation 4-11 Steam Dome Pressure 4-18 4-12 Void Fraction in Downcomer Levels 4-20 4-13 Void Fraction at Separator Inlet 4-21 i
5-1 Dryer Separation capacity as Function of Inlet 5-3 Moisture and Steam Velocity 6-1 Fozzle Arrangement 6-3 6-2 Calculated Center Line Spray Trajectory 6-21 vili
(-
ILLUSTRATIONS (Continued)
Figure Page 6-3 Coeparison of Predicted vs. Measured Horizontal Spray 6-22 Distribution for vertical Nozzle 6-4 Comparison of Predicted vs. Measured Horizontal Spray 6-23 Distribution for horizontal nozzle 6-5 Accumulated Liquid in Outer Node (Upper Plenum Segment 6-26 Test 14) 6-6 TRAC Predicted Void Fraction Distribution Below the 6-27 l'pper Tie Plate (Test 14) after initiation of subcooled ECC 6-7 Accumulated Liquid in Outer Node (Upper Plenum Segment 6-28 Test 17) 6-8 TRAC Predicted Void Fraction Distribution Below the 6-29 Upper Tie Plate (Test 17) after initiation of subcooled ECC 6-9 Accumulated Liquid in Outer Node (Upper Plenum Segment 6-30 Test 21) 6-10 TRAC Predicted Void Fraction Distribution Below the Upper 6-31 Tie Plate (Test 21) after initiation of subcooled ECC 7-1 Single Channel Option 7-2 ix
r-m ll
,i 4
TABLES Table g
2-1 Jet Pump Model Development Test Summary Test Matrix 2-5 2-11 2-2 Summary of Mixing and Nozzle Losses 4-12 4-1 Summary of Parameters used in the Separator Model 6-24 6-1 Summary of Cenditions for the Selected Upper Plenum Segment Tests e
s I
l xi
?
PREVIOUS REPORTS IN BWR REFILL-REFLOOD SERIES BWR Refill-Reflood Program Task 4.1 - Program Plan, G. W. Burnette, General Electric Company, NUREC/CR-1972, August 1981.
BWR Refill-Reflood Program Task 4.2 - Core Spray Distribution Experimental Task Plan, T. Eckert, General Electric Company, NUREC/CR-1558, November 1980.
BWR Refill-Reflood Program Task 4.2 - Core Spray Distribution Final Report, T.
i' Eckert, General Electric Company, NUREC/CR-1707, March 1981, BWR Refill-Reflood Program Task 4.3 - Single Heated Bundle Experimental Task Plan, D. D. Jones, L. L. Myers, J. A. Findlay, General Electric Company, NUREC/CR-1708, March 1981.
BWR Refill-Peflood Program Task 4.3 - Single Heated Bundle Experimental Task Plan, Addendum I, Stage 3 - Separate Effects Bundle, D. D. Jones, General Electric Company, NUREG/CR-1708 - Add. I, March 1981.
BWR Refill-Reflood Program Task 4.3 - Single Heated Bundle Final Report, W. A.
Sutherland, J. E. Barton, J. A. Findlay, Caneral Electric Company, NUREG/CR-2001, April 1983.
1 BWR Refill-Reflood Program Task 4.4 - CCFL/ Refill System Effects Tests (30 Sector) - Experimental Task Plan, D. G. Schumacher, General Electric Company, NURFG/CR-1846, July 1981.
BWR Refill-Reflood Program Task 4.4 - CCFL/ Refill System Effects Tests (30 Sector) - Experimental Task Plan, Addendum A, SSTF CCFL/ Refill Shakedown Plan, D.
G. Schumacher, T. Eckert. General Electric Company, NUREG/CR-1846, Add. A, September 1981.
BWR Pefill-Reflood Program Task 4.4 - CCFL/ Refill System Effects Tests (30 Sector) - Experimental Task Plan, Addendum B, 30 SSTF CCFL/ Refill Separate Effect Test Plan, D. G. Schumacher, General Electric Company, NUREG/CR-1846, Add.
E, September 1981.
BWR Refill-Reflood Program Task 4.4 - CCFL/ Refill System Effects Tests (30 Sector) - Fxperimental Task Plan. Addendum C, 30 SSTF CCFL/ Refill BVR/6 System Response Test Plan, D. G. Schumacher, General Electric Company, NUREG/CR-1846, Add. C. January 1982.
PWR Refill-Reflood Program Task 4.4 - CCFL/ Refill System Effects Tests (30 Sector) - Experimental Task Plan, Addendum D. SSTF CCFL/ Refill with ECCS Variation Test Plan (BWR/4 ECCS Geometry), D. G. Schumacher, General Electric Company, NUREG/CR-1846 Add. D, January 1982.
BWR Refill-Reflood Program Task 4.4 - 30 SSTF Description Document, J. E.
Barton, D. C. Schumacher, J. A. Findlay, S. C. Caruso, General Electric Company, NUREG/CR-2133, May 1982.
BWR Refill-Reflood Program Task 4.4 - CCFL/ Refill System Effects Tests (30 Sector) - Evaluation of Parallel Channel Phenomena, J. A. Findlay, General Electric Company, NUREG/CR-2566, November 1982.
EWR Refill-Reflood Program Task 4.4 - CCFL/ Reft 11 System Effects Tests (30 Sector) - SSTF System Response Test Results, D. G. Schumacher. T. Eckert, J. A.
Findlay, General Electric Company, NUREG/CR-2568. April 1983.
xiii
n-4 BWR Refill /Reflood Program Task 4.4 - CCFL/ Refill System Effects Tests (30 Sector) - Evaluation of ECCS Mixing Phenomena, J. A. Findlay, General Electric Company, NUREG/CR-2786 June 1983.
BWR Refill-Peflood Program Task 4.7 - Model Development Task Plan, J. C. M.
Andersen, B. S. Shiralkar, General Electric Company, NUREG/CR-2057, September, 1981.
BWR Refill-Fefinod Program Task 4.7 - TRAC /BWR Component Development, M. M.
Aburomia, Cencral Electric Company, NUREC/CR-2135, December 1981.
BWR Refill-Reflood Program Task 4.7 - Constitutive Correlations for Shear and Heat Transfer for the BWR Version of TRAC, J. C. M. Andersen, K. H. Chu, General Electric Company, NUREG/CR-2134, November 1982.
BWR Rcfill/Reflood Program Task 4.7 - Model Development: Basic Models for the BWR Version of TRAC, J. G. M. Andersen, K. H. Chu, J. C. $haug, General Electric Company, NUREG/CR-2573, September 1983.
BWR Refill-Reflood Program Task 4.8 - Model Qualification Task Plan, J. A.
j Findlay, G. L. Sozzi, General Electric Company, NUREC/CR-1899, August 1981, i
xiv
SECTION 4 STEAM SEPARATOR MODEL DEVELOPMENT In a boiling water reactor (BWR), separation of the steam-water mixture generated in the core is performed in the steam separators. Figure 4-1 shows two typical types of steam separators used in GE BWR's.
The primary measures of separator performance are: carryover (entrained liquid) in the steam leaving the separator, carryunder (entrained steam) in the water leaving the separator, and pressure drop of separator. The carryunder is of particular interest in plant analyses, since the amount of steam entrained in the water returning to the downcomer would affect the water subcooling at the reactor core inlet. The water subcooling, in turn, affects the thermal hydraulic performance of the fuel bundles, and the moderator-to-fuel ratio in the core.
A mechanistic steam separator model has been developed to calculate the carryunder, carryover, and separator pressure drop. The mechanistic model is
}
implemented into TRAC by modifying the PIPE component.
i 4.1 STEAM SEPARATOR MODEL
~
?
l I
Under normal operating conditions, the steam-water mixture enters the separator from standpipe, and passes through a set of stationary swirl van'es into the separating barrel. Thet a vanes produce a high rotational veloci,ty component in the fluid flowing through the separating barrel. The resultant centrifugal force separates the steam-water mixture into a water vortex on the wall of the separating barrel and a steam vortex cote.
Figure 4-2 shows the geometries and flows in the separator.
4.1.1 Mechanistic Model - Assumptions and Equations I
in this model, the following assumptions are made for the axial location near j
i the pick off ring:
(
l 1
1 4-1 l
l TERTIARY STAGE
)
r l
i l l
l SECONDARY STAGE j f PICKOFF RING b8' DISCHARGE j j PASSAGE STR AIGHTENING y
d VANES SEPARATING BARREL W:
PRIMARY SKIRT l
STAGE f* LOW RESTRICTION F
j e
i SWlRL VANES f
i II
~
STANDPIPE g
Y q
2 STAGE SEPARATOR 3 STAGE SEPAR ATOR Figure 4-1.
Typical Types of Steam Separators 4-2
I PICKOFF RING g,,
~I I
DISCHARGE PASSAGE l
l Po rg g
ul u
l l
l af l
veg l
l l
l l
l l
l l
l uouio tAvsR j
l VAPOR l/
gcoRe Hd JI i
I I
I
\\
l
\\
l
\\
!=
\\
\\
\\
I
\\
I cu
\\
In HUS Van i
U i
i Hik II v3. P.,,ni l'
,,p I
O
~
Figure 4-2.
Schematic of the Separator Model 4-3
k 1
There is one uniform axial velocity in each flow region, i.e.,
a.
o<r<r
- V
=V uniform in vapor core g
V, = V,g, uniform in water layer r<r<r g
y where r is the inner radius of the water layer.
g b.
The tangential velocity in each region is proportional to C which is related to the vortex strength, and is a function of r as follows:
{
rc 0<r<r
- V g
t 3/2 rf (4-1)
C r < r< r : V
=
f E
/r (4-2) c.
The void profiles are assumed as follows:
0<r<r a=1-b (4-3) g rW r < r < r, : a=a w
(4-4) g
,3
.r and
?)72 h 0.5 2
- M X
for Xg < 0.15
(
j i
!d r I.5 0.75 0
a = AA g
I w
(0.09335)
X for Xg >0.15 g
1
\\
C l
/
2 h 0.5
/gr b = BB i
w l
(1. y )3
\\
C l
A where X is the inlet quality, AA and BB are parameters to be g
fitted with data.
4 -
l d.
The pressure in the vapor core (P ) is assumed to be uniform g
radially and axially, and the pressure at the separator wall (P ) 13 relatad to P by centrifugal force across the water y
layer.
For ".ne first e. age et the separator, a total of 6 unknowns are introduced in this model.
These are V V,g, C,
r, P,
and P.
The required g
y equations are formulated from conservation of water mass, vapor mass, axial momentum, and angular momentum entering and leaving the separating barrel, from centrifugal pressure drop across the water layer, and from pressure drop in the discharge passage. The above unknowns can now be solved for given conditions of
)
at the nozzle inlet.
pressure P. total flow rate wg, and quality X g
The mass and momentum conservation equations for flows entering and leaving the separating barrel are as follows:
l Water Mass w
(1 - X ) w 3
g f V, (1-c) 2 nr dr
=
p o
2 "I (
2:s V 1
f b) r
=
3 r,
g (4-5) f V,f
( *)
I# ~#h)~"A 2 rp I#
~#)
+
w f -
2 l
Vapor Mass W
X W.
p V a23rdt
=
g 1 g a o
(4-6)
- f ) rf 230 V
( - 1 b
=
3 r,
(r,- r )*
27c v a.
+
f 8 af Angular Monientum r,
V r ( 2r dro Van) r in mi r
(4-7) h r"
V r ( 2rrdrcV,) + F
=
t t w O
4-5
r __
6 Axial Momentum 2
tr p.
c,{ v, + P ) 2nrdr o
- h (4-8) i
- w r
(pV:
=
+ P) 2ntdr + F, f
i Assuming that the flow through the swirl vane passage is homogeneous, the pressure and velocity entering the separating barrel are related to the conditions at the standpipe as follows:
i"Emi i ^i
- Omi an n
^
4 P
V g+
p,g
= P, +
pg (V
+Vtn ) (1 + CN0Z}
}i and V*"
tan 0
=
y tn where 8 is the angle between the swirl vane and the horizontal plane, and C
is the contraction loss coef ficient defined as:
N0Z C
= 0.5 N0Z A is the n zzle fl w area and A is the standpipe flow area.
N g
F, and F in Equations (4-7) and (4-8) are the axial and tangential j
components of the frictional force on the swirling water layer,
(
I I
t k
~
V F, = Ff A V
i w
i I
- I t
t w
I I
where V is the tangential velocity on the wall, tw 4-6
~...
C V
Y N
w and V is the resultant swirling velocity on the wall.
V
+V V
=
w tw af F is the resultant frictional force, g
o C V (2 Er ) H F
=
f f p y
y D
For turbulent flow over a flat plate, 0.455 C
=
F (log R,t)
R where et is defined as DY H Y R
=
w d
w-
- L p
y af The radial pressure drop across the water layer due to centrifugal force is r,
w Y
dP =
p P
r r
g f
or P -
'o
+ a (0
-c )
C f
)
P
=
I f
8 Y
r, (4,9) f
+ a(cf -p ) C
(#w 1
1) g f
r w
4-7
. ~ -.
1
?
The pressure drop in the discharge passage is r
8
( pV + P) dA dA 7
r 1
r
('
}
- hD Vh 1 + d$ Cp ( "_D+ EFFLD) + C g,p k
DD (P
+p h
E~O h
I)
+
j SUB D 12 i
where O and V are the mean discharge density and velocity to be defined.
MD D
H and D are the length of the separator barrel and hydraulic diameter of the D
D discharge passage, EFFLD is the ef f ective L/D coef ficient at the pick off ring, and C is the total loss coefficient in the discharge passage.
g
! l For the discharge passage, i
t 0.079 C
=
p
.5 R
e The steam and water flows discharged through the discharge passage are calculated as follows:
e,
r I
"g,cu *,
8p, V, 2"rdr r
r I
fi r
mfr N
W (1 -a) o V, 2ntdr f,cu f
r f<t i
For r r
i W
- no V,f a(r,- r )
g,cy g
r t
f cu f af
~
r ) ~
- I#w ~ #r)2-t 2
2 c
"P Y
-r W
w 1
r f
r
[
4-8 I
l
For' r
r f
2 W
= X. W - 2rp V I b -
Ir r
g,cu 1 i g ag y
r
- wl 2
f,cu = (1-X.) W. - 2ro V r
b -
W r
1 1
f ag r
- w The steam and water flows leaving the present stage and entering the next stage are:
L'
= (steam flow)in ~
g,cu f,co "
(** ' *"}in ~ f,cu The total discharge flow is D"
g.cu f,cu Assuming homogeneous flow in the discharge passage, the mean void fraction is:
Wg,cu g
cu g,cu f,cu (O !E )
g f the mean discharge density is fI~
P Om,D *
"cu O
- g cu f and the mean discharge velocity is D
y
=
0
- m,D b i
2 4-9
i In summary, for given nozzle inlet conditions, P,
X, and W, the -
g g
unknowns V V,g, C,
r, P,, and P, are calculated by solving Equations g
(4-5) to (4-10) simultaneously.
Similar equations can be written for the second and third stages. f,ince it is assured that P is uniform axially, i.e.,
the vapor core pressure drop in the axial direction is small, as a result the axial momentum equations can be neglected in the calculations.
For these stages the unknowns are reduced to V
V,f, C,
r, and P,,
and the equations are the conservation of water g
mass, vapor mass, and angular momentum, the pressure drop across the water layer, and the pressure drop in the discharge passage.
The right hand sides of Equations 4-5, 4-6, and 4-7 represent the water flow, vapor flow, and angular momentum entering the separating barrel. For the second and third stages, these terms are modified as follows:
(Water flow)in
,f,co previous stage
. =
W (Steam flow)in
. g,co, previous stage W
=
r r
(Angular momentum)in =
V r(23r dr pV,)
previous stage g
o 4.2 CARRYUNDER AND CARRYOVER The total vapor flow that is carried under consists of two parts:
the steam flow through the first discharge passage and the steam flow entrained by the water discharged from higher stages.
It is assumed that the second part is proportional to the square of the total water flow discharged from higher stages, i.e.,
"N 2
( g.cu} TOTAL g,cu 1
{
i,cu)i 22 whete:
N = 2 for 2-stage separator
= 3 for 3-stage separator and CC is a proportional constant to be fitted with data.
i 4-10
The total water that is carried over consists of two parts: the water flow through the last stage and the water flow entrained by the steam discharged from the higher stages through the discharge passage. Similarly, the second part is assumed to be proportional to the square of the total steam flow discharged from higher stages, i.e.,
s
~N
=2
, f,co TOTAL f,co N + DD.,
g, cu i,
(W l
I where DD is a proportionality constant to be fitted with data.
l The carryunder and carryover are defined as follows:
CU =
g.cu TOTAL Total downward water flow j
CO =
f,co TOTAL Total upward steam flow The parameters AA, BB, CC and DD are tuned to fit the available test data for 2-and 3-stage separators. Table 4-1 summaries the values for these parameters.
i Figures 4-3 and 4-4 show the comparison of the test data (15) and values calculated by the model of carryunder and carryover for a 2-stage separator.
Figure 4-5 shows the comparison of measured (16) and calculated pressure drop for a 2-stage separator. Figures 4-6 and 4-7 shows the comparison of measured (17) and calculated carryunder and carryover for 3-stage separators. Results of these comparisons indicate that the mechanistic model with the tuned parameters is adequate in predicting the available test data.
It should be noted that all available test data are around a limited range of inlet quality at a typical pressure and flow rate. The parameters used in the i
model could be verified further if more data at wider range of operating conditions becomes available in the future.
4-11
l i
1 Table 4-1 i
SUW.ARY OF PARAMETERS USED IN THE SEPARATOR MODEL 5
t 2-Stage Separator 3-Stage Separator Parameter let 2nd 1st 2nd 3rd AA 110.
20.
110.
20.
20.
BB 0.5 0.25 0.5 0.25 0.55 CC 0.0004 0.0004 DD 0.009 0.I1 4-12
10 TOTAL F LOW RATE = 450000 lb/hr (568 ko/s)
P 08 SEP WATER LEVEL 22 m.
=
r_';
i f
/
E I
- $~' 0 6 DATA f
-- O -- MODE L
/
I
/
?
I
/
T O4 g
/W v
- "* O = -== C = = """ O "
0.2 j
8 I
8 i
1 1
0 2
4 6
8 10 12 14 16 18 INLET OUALITY {%)
Figure 4-3.
Comparison of Test Data and Mechanistic Model Prediction on Carryunder for 2-stage Separator 25 TOTAL FLOW RATE - 500000 lb/hr (63.1 ks/s) 20 SEP WATER LEVEL 10 m
=
\\
r _,
f
\\
@ DATA y
,g c
n
- D es MODEL 8
g 10 K
5 4
N
\\
5
\\k-
_n.___ p -
I I
I I
I 0
6 8
1; 12 14 16 18 20 22 4NLET OUALITY (%)
Figure 4-).ComparisonofTestDataandMechanisticModel Prediction on Carryover for 2-stage Separator 4-13
100 a
/
O
/
3 a
E A
8
/
1 10
/
N d
F i
2 E
i i
DATA
- D = MODEL g
1 i
103 104 106 INLET VOLUMETRIC FLOW RATE (cu h/ht)
Figure 4-5.
Comparison of Test Data and Mechanistic Model Prediction on Separator Pressure Drop for 2-stage Separator 3
1 0.7 I
i I
08 TOTAL F LOW R ATE = 640n00 lb/hr
[
(80.8 kg/s)
SEP WATER LEVEL 106n.
I 0,
I
_a O4 g c
0.2
,?
C) -
3 02 A DATA O uOoEL I
I I
I 8
0 6
8 10 12 14 16 18 20 INLET QUAllTY {%)
Figure 4-6.
Comparison of fest Data and Mechanistic Model Prediction on Carryunder for 3-stage Separator 4-14
F 60 TOTAL F LOW RATE = 450000 lb/hr (56.8 kg/s) 50 SEP WATER LEVEL
- 22 m.
40 f
' 7
\\
?
\\
E N
DATA
-O-uooEL g%
10 g
- O _ _ -.
i I
I I
t t
Y N
o 2
4 6
8 10 12 14 16 18 INLET OUALITY (%)
Figure 4-f. Comparison of Test Data and Mechanistic Model Prediction on Carryover for A-stage Separator 0.7 i
TOTAL FLOW RATE = 80 8 kg/s 1
f 06 - SEP WATER LEVEL 10 m.
=
I I
i 0.5 g
i i
h
$ 04 g O
% N E O3 m
... o- -
o 5
02 O DATA
.- O - MECHANISTIC MODEL RESULTS 01 Q
I I
I I
I l
6 8
10 12 14 16 18 20 INLET OUALITY (%)
Figure 4-8.
Coniparison of Test Data, Mechanistic Model and TRAC Results on Carryunder for 3-stage Separator 4-15 1
t 4
4.3 CHECKOUT CALCULATIONS FOR STEAM SEPARATOR MODEL 4.3.1 Simple Check Cases A series of checkout calculations for the steam separator model were performed using a simple TRAC model.
e Four cases with different inlet quality to the separator were run with this simple TRAC model to a quasi-steady state.
As a checkout calculation, mass balances were performed for the steam and water flows entering and leaving the separating cell from the last output edit of these runs. Then the carryunder and carryover were calculated based on the mass balances.
j i
The carryunder and carryover calculated with TRAC output agree very well with those calculated by the stand alone separator mechanistic model before implementing into TRAC. Figure 4-8 shows the comparison on carryunder calculated by the mechanistics model and from mass balance on TRAC output with test data for the first three cases.
4.3.2 SIMPLIFIED BWR/6 MODEL f
A simplified BWR/6 medel simulating the recirculation line break was used as another check case for the steam separator model. Figure 4-9 shows the schematic i
of this model. The vessel component consists of 2 concentric rings and 8 axial levels. The separating cell of the separator is connected to vessel cell 1 at level 6.
Initially the water level outside the separator is located in level 7.
Both steady-state initialization and transient calculations were performed with the Icvel model option on.
Figure 4-10 shows the void fractions in the downcomer and in the lower plenum.
The void fraction decreases in the lower downcomer levels as the returning water is mixed with the subcooled feedwater.
As the downcomer water f
flows into the recirculation loop, the remaining void residual completely collapses due to the large pressure rise across the pumps. As a result, the void fraction in the lower plenum remains essentially zero.
In comparison for calculations performed using the the old separator model with perfect separation, the void fractions in all downcomer levels are practi-cally zero because there is no steam discharged as carryunder into the downcomer.
4-16
l I
i FILL w
E i
ed 3
4w I
I l
l l
I I
STEAM DOME l
I I
I I
I I
I I
I i
l l
I i
8 l
i I
l "g _w I
(
m g
FILL UPPER PLENUM i
F EEowATER E
E
-r w
w
____.______g__.
_ _. _ g3
[
0 l
.J O
w t
23(
_ _ _\\
[_ _ __
w SROCEN o
4 LOOP g
g INTACT g
y g
h 4
i LOOP m
4 m
g
,i O,
l f
l LOWER PLENUM I
[
I e
T I
ro r
i oi l
I Q
k
+
i Figure 4-9.
Simplified BWR/6 Medel for separator test case 4-17
. ~..
0.06 1 LEVEL 1 2 LEVEL 2 3 LEVE L 3 4 LEVEL 4 5 LEVEL 5 6 LEVEL 6 0 04 5
5 N
E 9
O
-- 4 0 02 3
0.00 I1 O
2 4
6 8
TIME (s)
Figure 4-10.
Void Fractions in Downcomer Levels for the BWR/6 Steady-State Calculation 75 f
7.0 5
?.
E D
E t! 65 t
O NEw SEPARATOR MODEL O OLD SEPARATOR MODEL 60 I
I I
O 2
4 6
8 10 12 TIME (s)
Figure 4-11.
Steam Dome Pressure 4-18
r--
e A transient calculation was run for about 10.5 seconds by initiating a break at the suction side in one of the recirculation lines. The results are shown in Figures 4-11 and 4-12.
On these figures the results from two check cases for the level model are also shown for comparison. The two check cases for the level model were run using the old separator model, with and without the level model option.
Figure 4-11 shows the comparisons of steam dome pressures of these two cases.
The initial water mass and steam volume outside the core and separator were maintained the same for the two cases, so that the steam dome pressure responses are similar.
Figure 4-12 shows the comparison of void fractions in the downconer levels.
Figure 4-13 shows the void fraction at the separator inlet for the present check The void fraction changes from about 0.8 to above 0.8'8 at around 2 seconds.
case.
As seen in check case of the previous section, high inlet void fraction will lead to larger carryunder, and in turn, higher void fraction in the water pool surrounding the separator. In this case, the void f ractions in the downconer levels as shown in Figure 4-12 remain almost constant for the first two seconds, they then increase gradually until the water level crosses the vessel cell boundary.
4.4 CONCLUSION
AND RECOMMENDATION Based or the results of the checkout calculations, it can be concluded that the separator rodel has been properly implemented into the TRAC computer code.
In using the separator model, the initial water level outside the separator should be located at least one level above the discharging axial level where the separating cells are connected.
Otherwise, the discharged steam will rise directly to the steam dome and will not appear as carryunder in the downcomer.
4-19
... - ~
\\
1.0 3
0 O.6 y
a 9
?
/
/
15:::
M
'A J
m y
.0 (
l i
~
0 2
4 6
10 12 1.0 LEVEL 3 O NEW SEPARArog
[
%CEL O o.o sePARAron MODEL 8
5 0.s g
9 f
0.0 t-p f
a 0
7 4
8 10 12 TIME h)
Figure 4~12 Void Fraction in Downcomer Levels 4-20
T 1
i 1.0 a
~
N 0.9 bc k
E e
f 0.8 0.7 f
f f
O 2
6 8
10 12 TIME is)
Figure 4.}3-Void Fraction at Separator Inlet 4-21
i h
b 4
i i
Section 5 STEAM DRYER MODELING t
The steam dryer is structured as an integral part of the pressure vessel as j
shown in Figure 1-1.
The chsracteristics of the steam dryer to be model are the dryer pressure drop and further separation of moisture in the steam flow from the steam separator.
r The pressure drop is simulated by a flow resistance to the steam flow at the l
cell boundary between the steam dome and dryer. By imposing the appropriate loss factor on the vapor phase in the axial direction, the pressure drop in the dryer
)
is correctly determined. The loss factor K for the dryer can be calculated as.
i i
i SD U
~~
l 0
v SD K
~
2 I
ASD 7
where p is the vapor density, W is the steam flow through the dryer, A y
y SD i
is the dryer flow area, and AP is the pressure drop in the dryer.
f gp The separation of moisture from the steam flow in the dryer is simulated by i
imposing a large liquid resistance in the axial direction at the cell boundary i
between the steam dome and the dryer.
The separation capacity of the dryer depends on the steam velocity and the moisture content of the steam flow entering the dryer, as shown in Figure 5-1.
For a given inlet steam velocity, there correwponds a critical dryer inlet moisture. Good moisture separation is achieved for inlet moisture lower than the critical value.
If the inlet moisture is above the critical value, the dryer i
i capacity in exceeded and the moisture would pass through the dryer.
The dryer capacity is simulated by a capacity factor GDRY which is defined in the following. For a given steam velocity (V) at the cell boundary between the l
5-1 l
4 e
, i.
-. ~,, - -
9
^
dryer and the steam dome, the critical dryer inlet moisture (CDIM) is calculated as (see Figure 5-1),
CDIM = 1.
- V<VDRY1 CDIM = 1. - V-VDRY1
- VDRY 14V< VDRY2 VDRY2 - VDRY1 CDIM = 0.
- VDRY2<V and the dryer inlet moisture (DIM) in the steam flow is.
DIM
- 1. -
a
=
a + (1-a) (pg /py',
where a, p
and o are the void fraction, liquid and vapor densities at the g,
y dryer cell.
The capacity factor is defined as, GDRY
=1
- DIM <CDIM CDRY = 1. + CDIM - DIM
- CDIM< DIM <(CDIM + DELDIM)
, DELDIM CDRY = 0.
- (CDIM + DELDIM)< DIM The capacity factor (GDRY) is then used to adjust the appropriate liquid resistance to simulate the dryer separation capacity.
p 5-2
n t
100 i
I E
A80VE DOTTED LINE i
w 0% SEPARATION E
k BELOW SOLID LINE DELDIM
!2 50 - 100% $EPARATION f
_f t
CDIM U
E I
8ETWEEN LINES LINE AR INTERPOLATION I
I I
.[
lV VORY1 VDRY2 i
la 0
g g
g, 0
1 2
3 4
6 6
7 g
ORYER INLET STEAM VELOCITY (m/sec)
I Figure 5-1.
Dryer Separation Capacity as function of Inlet Moisture and Steam Velocity l
i i
f i
+
i 5-3
- a
.=
$$ e N
h2.b a4 Ze 5<5m aY
'U 73Ui4m $O3bc0 > o15g z
"g R
Ez u E
$abEo& z o d
- ! =.
G
/
C Ca$ $?$J a R
- 6<b "s
$#3 25 74 BW R
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TO R O A D C
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