József Bánáti
Chalmers University of TechnologyDepartment of Nuclear Engineering
E-mail: [email protected]
Multi-Phase Modelling Capabilities of the
RELAP5 Thermal-Hydraulic System Code
J. Bánáti, SIAMUF Seminar 2005-10-21
Background• RELAP5: Reactor Excursion and Leakage Analysis Program• Originally developed by the US Nuclear Regulatory Commission• Started in the late ‘70s as a domestic project at INEL• Currently applied world-wide
• Users:• Regulatory bodies, safety authorities• Scientific and educational institutions• Power industry, plant and facility designers
• Fields of application:• Licensing audit calculations• Safety evaluation of NPPs• Simulation of transients or accidental scenarios• Design of small or large-scale experimental facilities
J. Bánáti, SIAMUF Seminar 2005-10-21
Features of RELAP5
• Use of nonhomogeneous, nonequlibrium, 6 equation, 2-fluid model• Effects of noncondesable gases and boron taken into account• Liquid: H2O, D2O, Gas: vapour + {air, N2, O2, H2, ...}• Essentially 1D thermal-hydraulics, but 2D or 3D is used in specific
components (crossflow)• 1D or 2D heat conduction in system structures• Convective & radiative heat transfer between fluid and structure• Specific flow models (default or user-selectable):
• Critical flow, abrupt area change, CCFL, thermal stratification, ...• Variety of pre-defined components:
• Pipe, branch, junction, valve, separator, pump, turbine, accumulator, con-trol system, ...
J. Bánáti, SIAMUF Seminar 2005-10-21
Spatial Discretisation
J. Bánáti, SIAMUF Seminar 2005-10-21
The Finite-Difference EquationsContinuity:
Momentum:
VL αg L,n ρg L,
n 1+ ρg L,n–( ) αf L,
n ρf L,n 1+ ρf L,
n–( ) ρg L,n ρf L,
n–( ) αg L,n 1+ αg L,
n–( )+ +[ ]
α· g j 1+,n ρ· g j 1+,
nvg j 1+,
n 1+ Aj 1+ α· g j,n ρ· g j,
nvg j,
n 1+ Aj–( )+ Δt
α· f j 1+,n ρ· f j 1+,
nvf j 1+,
n 1+ Aj 1+ α· f j,n ρ· f j,
nvf j,
n 1+ Aj–( )Δt+ 0=
αgρg( )jn vg
n 1+ vgn–( )jΔxj αfρf( )j
n vfn 1+ vf
n–( )jΔxj12--- α· gρ· g( )j
nvg
2( )Ln
vg2( )K
n–[ ]Δt+ +
12--- α· fρ· f( )j
nvf
2( )Ln
vf2( )K
n–[ ]Δt
12--- α· gρ· g( )j
nVISGj
n α· fρ· f( )jnVISFj
n+[ ]Δt–+
PL PK–( )n 1+ Δt– ρm( )jn[ Bx αgρg( )j
nFWGjn vg( )j
n 1+– αfρf( )jnFWFj
n vf( )jn 1+–+=
Γg( )jn vg vf–( )j
n 1+ ]ΔxjΔt– α· gρ· g( )jnHLOSSGj
nvg j,n 1+ α· fρ· f( )j
nHLOSSFj
nvf j,n 1++[ ]Δt–
J. Bánáti, SIAMUF Seminar 2005-10-21
Energy:
For closure relations, a large number of correlations are built into the code. These are based on well qualified experimental datasets.
The actual flow pattern is determined by using flow regime maps.
VL ρf L,n Uf L,
n PLn+( )– αg L,
n 1+ αg L,n–( ) αf L,
n Uf L,n ρf L,
n 1+ ρf L,n–( ) αf L,
n ρf L,n Uf L,
n 1+Uf L,
n–( )+ +[ ]
α· f j 1+,n ρ· f j 1+,
nU· f j 1+,
nPL
n+( )vf j 1+,n 1+ Aj 1+ α· f j,
n ρ· f j,n
U· f j,n
PLn+( )vf j,
n 1+ Aj–[ ]Δt+
hf*
hg* hf
*–----------------
⎝ ⎠⎜ ⎟⎛ ⎞
⎩⎨⎧
L
nPs L,
n
PLn
---------Hig L,n TL
s n 1+,Tg L,
n 1+–( )
hg*
hg* hf
*–----------------
⎝ ⎠⎜ ⎟⎛ ⎞
L
n
Hif L,n TL
s n 1+,Tf L,
n 1+–( )+=
PLn Ps L,
n–
PLn
---------------------⎝ ⎠⎜ ⎟⎛ ⎞
+ Hgf L,n Tg L,
n 1+Tf L,
n 1+–( ) 1 ε+
2------------⎝ ⎠
⎛ ⎞ hg L,′ n, 1 ε–
2-----------⎝ ⎠
⎛ ⎞ hf L,′ n,+– Γw L,
n Qwf L,n DISSf L,
n }VLΔt+ +
J. Bánáti, SIAMUF Seminar 2005-10-21
Flow Regime MapsHorizontal:
Vertical:
Horizontally stratified (HST)
Increasing void fraction αg
BBY-HST
SLG-HST
SLG/ANM-HST
ANM- MPR-HST
Mist(MPR)
Annularmist
(ANM)SLG/ANM
Slug(SLG)
Bubbly(BBY)vcrit
1/2vcrit
Increasingrelativevelocity|vg- vf |
αBS αSA αAM
HST
αDE
and massflux Gm
and 2500kg/m2-s
and 3000kg/m2-s
0.0 1.0
Vertically
stratified (VST)
Transition
Unstratified
Bubbly(BBY)
SLG/ANM
Annularmist (ANM)
Slug(SLG)
Mist(MST)
Invertedslug (ISL)
IAN/ISL
BBY-IAN
Invertedannular
IAN/ISL-
SLG
ISL-SLG/
ANM
Post-dryout
Transition
Pre-CHF
vTb
αBS αSA αAMvm
αBS αSA
(MPR
)
(MPO
)
Increasing
Increasing αg
αDE
(IAN)
αCD
ANM/MSTSLG/ISL
αAM0.0 1.0
0.0 1.0
Incr
easi
ngT g
- Ts
1 vTb2
J. Bánáti, SIAMUF Seminar 2005-10-21
The SNAP Graphical User Interface for RELAP5
J. Bánáti, SIAMUF Seminar 2005-10-21
Animation Mask for a Typical PWR
J. Bánáti, SIAMUF Seminar 2005-10-21
Application of RELAP5 at Chalmers: Power Uprate of the Ringhals-3 Nuclear Power Plant
• Increase of power from 100% to 113.5% in 2 stages:• Steam generator replacement• High burnup fuel + hardware changes
• Project granted by SKI (Swedish Nuclear Inspectorate)• Acting as a TSO (Technical Support Organisation)• Methodology to perform independent safety analysis with TH coupled to
neutron kinetics:• Development of a steady-state model• Analysis of the consequences of higher power• Selected limiting transients:
• Steam line break• Unintentional control rod withdrawal, • Feedwater disturbances• LOCA
J. Bánáti, SIAMUF Seminar 2005-10-21
Nodalization of the Ringhals-3 NPP
11 12 13
440
205 206 207
5
3
15
20 21
25
30
35
6162
65 60 41 40
5068
6770
71
72
75
330
326 331
320 340
305
383390 385386 381
906 928 495
497
498
441
350
380
496
905
461
463
462
460
945
941
942
940
918
916
915
910
943
932
930
931
933
405
435
220 240
226
226
431
231
231
230
283
290
285
286
281 280
904
925 493 250947
924
903
120 140
130
105
450
948
927
316346
216
246
116146
150491922902
180185 181183186190
492
901
946
921
451
494
911
66
RELAP5 Nodalization of the
Primary Side of Ringhals-3
Loop 3
Loop 2
Loop 1
SG 3
SG 2
SG 1
Pre
ssu
rize
r
Accu 3
Accu 2
Accu 1
Bo
ron
Tan
k
Ch
arg
ing
Lin
e
Do
wn
co
mer
Co
re
RHR 2
RHR 1
Normal Letdown
Safety Valve
ECCMixECCMix
ECCMix
ECCMixECCMix
ECCMix
PORV
4
J. Bánáti, SIAMUF Seminar 2005-10-21
Steady-State Results
0 50 100 150 200Time (s)
4400
4500
4600
4700
4800Fl
ow R
ate
(kg/
s)
mflowj-105010000mflowj-205010000mflowj-305010000
Primary Side Mass Flowrates
J. Bánáti, SIAMUF Seminar 2005-10-21
Steady-State Results
0 50 100 150 200Time (s)
500
520
540
560
580
600Fl
ow R
ate
(kg/
s)
mflowj-561000000mflowj-661000000mflowj-761000000
Steam Mass Flowrate
J. Bánáti, SIAMUF Seminar 2005-10-21
Steady-State Results
0 50 100 150 200Time (s)
550
560
570
580
590
600V
olum
e L
iqui
d T
empe
ratu
re (
K)
tempf-120010000tempf-220010000tempf-320010000tempf-190010000tempf-290010000tempf-390010000
Hot and Cold-Leg Temperatures
J. Bánáti, SIAMUF Seminar 2005-10-21
Benchmark Case: IAEA SPE-4
• Standard Problem Exercise No. 4 (SPE-4)• Supervised by the International Atomic Energy Agency (IAEA)• Transient: 7.4% Small-Break Loss of Coolant Accident (LOCA) in VVER-
440 type reactor simulated in a 1:2000 scaled-down model• Test facility: PMK-2 (Budapest, Hungary)• Focusing on prediction of the dry-out phenomenon• RELAP5 performed very well: good simulation of the rod temperatures and
system pressure
J. Bánáti, SIAMUF Seminar 2005-10-21
Results of IAEA SPE-4
420
440
460
480
500
520
540
560
580
600
620
640
0 200 400 600 800 1000 1200 1400 1600 1800
TE
MP
ER
AT
UR
E [K
]
TIME [s]
Rod surface temperature (h=2.954 m)
RELAP5TE12
J. Bánáti, SIAMUF Seminar 2005-10-21
Results of IAEA SPE-4
0
2
4
6
8
10
12
14
0 200 400 600 800 1000 1200 1400 1600 1800
PR
ES
SU
RE
[MP
a]
TIME [s]
Pressure in upper plenum (h=3.754 m)
RELAP5PR21
J. Bánáti, SIAMUF Seminar 2005-10-21
Concluding Remarks
• RELAP5 is an excellent tool for analysis of complex TH processes• The code is applicable in many fields beyond nuclear (e.g. chemical,
pressurised tank blowdown, 2-phase flow analysis in pipelines, etc.)• Continuous improvement is provided by the CAMP agreement• User feedback is taken into account in new versions• Coupling to CDF and neutron kinetic applications is established
Thank you for your attention!
J. Bánáti, SIAMUF Seminar 2005-10-21
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