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THE COUPLED TRAB-3D-SMABRE CODE FOR 3D
TRANSIENT AND ACCIDENT ANALYSES
J. Miettinen & H. Räty
VTT Processes
SAFIR mid-term seminar, January 20-21, 2005, Espoo
2
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
Coupled TRAB-3D - SMABRE code
GOAL OF DEVELOPMENT
CODES
– TRAB-3D
– SMABRE
COUPLING
– parallel
– Internal
TRAB-3D - SMABRE STATUS, January 20, 2005
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
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VTT TECHNICAL RESEARCH CENTRE OF FINLAND
Reactor analysis calculation system of VTT Processes
Basic nuclear data
ENDF/B, JEF
= codes developed by VTT
= codes partly developed by VTT
Nuclear data processing
= codes applied by VTT NJOY
Nuclear data libraries
CASMO libraries
(25 - 70 energy groups)
Calculation of
Steady state fuel CASMO-4 CASMO-HEX
assemblywise two
rod behaviour (also Square hexagonal hexagonal
group constants
probabilistic analyses)
Calculation of reactivities,
ENIGMA, SIMULATE HEXBU-3D
ARES power and burnup
FRAPCON square VVER
distributions etc.
Data transfer and
CROCO
condensation for one-
Fuel rod behaviour dimensional group constants
during RIAs
and LOCAs TRAB SMATRA
One-dimensional dynamics
BWR PWR
SCANAIR, codes
FRATRAN
TRAB-3D HEXTRAN Three-dimensional
FRAPTRAN-
GENFLO BWR, PWR VVER dynamics codes
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
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VTT TECHNICAL RESEARCH CENTRE OF FINLAND
Goal of TRAB-3D - SMABRE development
Replace the hydraulics solution in the 3D core with SMABRE
Quick remedy to known deficiencies in the model
=> calculation of transients with flow reversal in core and by-pass
General SMABRE thermal hydraulics possibly not as accurate in the
core as with the present model of TRAB-3D or with a future application
using the accurate PLIM hydraulics solver
SMABRE solution allows new features into the circuit modelling
May act as a reference for a later TRAB-3D - PLIM calculation
Opens options to model an open core or couple to other system
codes
High priority, high uncertainties
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
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VTT TECHNICAL RESEARCH CENTRE OF FINLAND
TRAB-3D transient and accident analysis code
3D neutronics with quadratic core geometry
A fast two-level iteration nodal method with only one
solved variable for each node in the outer iteration
Implicit time-discretization methods allow flexible
time-step choices
1D parallel channel hydraulics for the core
Includes for a BWR circuit: the main circulation
system inside the pressure vessel, steam lines,
pumps and control systems
Core and circuit thermal hydraulics iterated together
with neutronics during each time step
Separate core model can be coupled to the fast-
running SMABRE system code for PWR calculations
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
6
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
Validation summary of TRAB-3D
Case Code system Reactor type Year
OECD LWR Core TRAB-3D 1996-
PWR, BWR
transient benchmarks (core) 1997
OECD PWR MSLB TRAB-3D- 1998-
PWR
benchmark SMABRE 2000
OECD BWR TT TRAB-3D 2001-
BWR
benchmark (core) 2002
Olkiluoto pump trip TRAB-3D BWR 1998
Olkiluoto 1 pressurization
TRAB-3D BWR 1999
transient 1985
Olkiluoto 1 instability
TRAB-3D BWR 2000
incident 1987
Olkiluoto 1 load rejection 2001-
TRAB-3D BWR
test 1998 2003
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
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VTT TECHNICAL RESEARCH CENTRE OF FINLAND
TRAB-3D applications
• Olkiluoto BWR
typically 500 channels in the core, steam dome
control of
25 axial nodes, 11 radial mesh steam flow
points in the fuel pellet
steam
• Olkiluoto 3 EPR lines separation zone
control of
feed water
(coupled to SMABRE)
riser
• SWR1000 concept feed water flow
upper ends of core
channels
• BWR90+ concept slave channel
by-pass channels
core channels
• Best estimate or conservative lower ends of core
channels
control of
analyses, stability studies pump speed beginning part of
• Accurate calculation of core with circuit
actual fuel types of the loading
• Reasonable computing effort pumps
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
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VTT TECHNICAL RESEARCH CENTRE OF FINLAND
SMABRE circuit model
A node-junction hydraulic circuit code similar to RELAP
Solution method non-iterative
Five flow equations
Very fast
Used coupled to core codes for modelling PWR circuits
Includes a point kinetics neutronics model
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
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VTT TECHNICAL RESEARCH CENTRE OF FINLAND
SMABRE VALIDATION OF THERMOHYDRAULICS
----------- Reference Volume Experiments carried out
plant Scaling
LOFT Westingh. 1:50 2.5 % cold leg SBLOCA, RCP on
LOBI/ KWU 1:712 0.4 % cold leg SBLOCA
Mod1
LOBI/ KWU 1:712 1.0 % cold leg SBLOCA
Mod2
PIPER-ONE GE BWR 1:2200 2.6 % recirculation line break, ISP-
21
DOEL real plant 1:1 Real plant SGTR accident, ISP-20
SPES Westingh. 1:427 Loss of feedwater, with core heatup,
ISP-22
ROSA-IV Westingh. 1:48 5 % cold leg SBLOCA,
ISP-26
PMK VVER 1:2070 7.4 % cold leg SBLOCA
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
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VTT TECHNICAL RESEARCH CENTRE OF FINLAND
SMABRE TYPICAL APPLICATION
125
828
827
124
SPRAY 7160-7660(100)
826
825
113
123
824 716-766(10)
Loviisa VVER-440
823
CHARGING
SBLOCA and ATWS
114
122
822
115
821
FW
121
116
120
Loop seal effects
1023-1073(10)
108-112,118
1171-1176 108-112,118
54,
56 58
1022-1072(10)
96-101
Multilayer steam
7-12 1021-1071(10)
411-
416
251 -
256 55,57
1-6
102-107
961-1011(10)
generator
13-18 42 962-1012(10)
-
401-
406 19-24
47
48-53
Reactor vessel with
LETDOWN
381-386
261 -
266 parallel channels
371-376
361-366
271 PRESSURE VESSEL
-
276
351-356 39 24
341-346
266
281 23 19
331-336 - 386
286 265 261
321-326 385 381
39
311- 316
384 382
811 -
22 264 383 262 20
816
263
291- 21
296
301 -
306
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
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VTT TECHNICAL RESEARCH CENTRE OF FINLAND
Present coupling of TRAB-3D and SMABRE cores,
= PARALLEL COUPLING
Totally independent codes
coupled together
Thermal-hydraulics of the
core is calculated with
both codes.
Connection by data
exchange once in a time-step
First applications with 3-D
neutronics in 1991 - 1992,
with 1-D neutronics 1988
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
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VTT TECHNICAL RESEARCH CENTRE OF FINLAND
Power to coolant
HYDRAULICS HEAT CONDUCTION
IN FUEL ROD
Heat transfer
mechanisms
Coolant and Surface
soluble poison temperature
New coupling of properties
Heat flux
of fuel rod
TRAB-3D and SMABRE cores,
= INTERNAL COUPLING HEAT TRANSFER
FROM CLADDING
TO COOLANT
Power Doppler
Directly temperature
to coolant
Power in
Coupling of physical processes DIFFUSION
fuel
PARAMETERS
in the core calculation WITH FEEDBACKS
NEUTRONICS
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
13
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
New coupling of TRAB-3D and SMABRE cores,
= INTERNAL COUPLING
Core hydraulics with SMABRE for each assembly
Heat transfer, neutronics with TRAB-3D
Connection by data exchange in every node
Iteration during a time-step
Connection analogous to that of TRAB-PLIM application
New approach at VTT, used in other organizations but usually with only
a few channels in hydraulics and heat transfer by the system code
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
14
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
New coupling of TRAB-3D and SMABRE cores,
= INTERNAL COUPLING
COUPLED CORE CORE CHANNEL
TRAB-3D SMABRE
to circuit
Neutronics Heat Transfer Hydraulics
Local power
directly to
coolant
Local
- pressure
- mass flux
Local - coolant
power temperature
- heat flux
Local
Local fuel cladding
temperature temperature
Local
- coolant density
from circuit - soluble poison density
- coolant temperature
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
15
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
New coupling of TRAB-3D and SMABRE cores,
= INTERNAL COUPLING
Options in thermal hydraulics geometry
Standard TRAB features for describing BWR bundle
geometry are maintained
Each bundle described with its own core channel
Different zones with different core inlet pressure drops
(illustrated with colours in the picture)
Axial subregions in core with different characteristics (for
describing part length rods)
New SMABRE features allowing to include some
three-dimensional phenomena in the lower and upper
plena
lower plenum, core and upper plenum divided into
circumferencial sectors and radial zones
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
16
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
TRAB-3D - SMABRE, STATUS January 20, 2005
=> A working steady state solution has been created
and is being tested
Challenges in modelling:
Two basically different modelling philosophies coupled together:
TRAB-3D solutions designed for coupled iterations
SMABRE solution non-iterative
Especially in steady state: SMABRE proceeds into a "steady state"
by calculating forward in time, while TRAB-3D iterates
The coupled processes themselves are complex
TRAB-3D includes 20 years of reactor dynamics experience inside
the integral model
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
17
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
TRAB-3D - SMABRE, STATUS January 20, 2005
Hydraulics solution separated from TRAB calculation
SMABRE's matrix solution has been developed to allow solutions
of a large number of channels with a reasonable computing time
Interface created: connection at node level inside iterations
Macro for generation of SMABRE core geometry has been
completed
A platform created for running different coupling schemes
Output routines for core hydraulics from SMABRE being tested:
radial and axial core distributions, inlet, outlet and averaged
variables
Steady state procedure and converge criteria completed and being
tested
Connection options in heat transfer being tested
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
18
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
19
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
20
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
TRAB-3D - SMABRE, STATUS January 20, 2005 cont.
Next steps:
Once the steady state is found adequate, dynamics is more
straightforward
An iterative matrix solution looks effective and will probably be applied
Testing of flow reversal
Validation
Further possibilities in later development:
Use existing porosity model PORFLO for full 3D core thermal hydraulics in
the open core
Connecting TRAB-3D to other system codes
VTT PROCESSES
H. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005
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