the coupled trab-3d-smabre code for 3d transient and accident analyses

THE COUPLED TRAB-3D-SMABRE CODE FOR 3D TRANSIENT AND ACCIDENT ANALYSES

J. Miettinen & H. RätyVTT Processes

SAFIR mid-term seminar, January 20-21, 2005, Espoo

VTT TECHNICAL RESEARCH CENTRE OF FINLAND2

VTT PROCESSESH. Räty & J. Miettinen, SAFIR mid-term seminar, 20.-21.1.2005

Coupled TRAB-3D - SMABRE code

GOAL OF DEVELOPMENT

CODES– TRAB-3D– SMABRE

COUPLING– parallel– Internal

TRAB-3D - SMABRE STATUS, January 20, 2005



Basic nuclear data

Nuclear data processing

Nuclear data libraries(25 - 70 energy groups)

Calculation ofassemblywise twogroup constants

Calculation of reactivities,power and burnupdistributions etc.

Data transfer andcondensation for one-dimensional group constants

One-dimensional dynamicscodes

Three-dimensionaldynamics codes

ENDF/B, JEF

NJOY

CASMO libraries

HEXBU-3DVVER

SMATRAPWR

HEXTRANVVER

CASMO-HEXhexagonal

TRABBWR

TRAB-3D

ENIGMA,FRAPCON

SIMULATE

Steady state fuel rod behaviour (alsoprobabilistic analyses)

Fuel rod behaviourduring RIAsand LOCAs

Square hexagonal

square

BWR, PWR

CASMO-4

SCANAIR,FRATRAN

FRAPTRAN- GENFLO

= codes developed by VTT= codes partly developed by VTT= codes applied by VTT

CROCO

ARES

Reactor analysis calculation system of VTT Processes



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



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



Validation summary of TRAB-3DCase Code system Reactor type Year

OECD LWR Core transient benchmarks

TRAB-3D (core) PWR, BWR 1996-

1997 OECD PWR MSLB benchmark

TRAB-3D-SMABRE PWR 1998-

2000

OECD BWR TT benchmark

TRAB-3D (core) BWR

2001- 2002

Olkiluoto pump trip TRAB-3D BWR 1998

Olkiluoto 1 pressurization transient 1985 TRAB-3D BWR 1999

Olkiluoto 1 instability incident 1987 TRAB-3D BWR 2000

Olkiluoto 1 load rejection test 1998 TRAB-3D BWR

2001- 2003



TRAB-3D applications

separation zone

riser

upper ends of corechannels

by-pass channels

beginning part ofcircuit

core channels

lower ends of corechannels

control offeed water

control ofpump speed

control ofsteam flow

pumps

slave channel

feed water flow

steam dome

steamlines

• Olkiluoto BWR typically 500 channels in the core, 25 axial nodes, 11 radial mesh points in the fuel pellet

• Olkiluoto 3 EPR

(coupled to SMABRE)

• SWR1000 concept

• BWR90+ concept

• Best estimate or conservative analyses, stability studies • Accurate calculation of core with actual fuel types of the loading• Reasonable computing effort



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



SMABRE VALIDATION OF THERMOHYDRAULICS

Reference plant

Volume Scaling

Experiments carried out

LOFT Westingh. 1:50 2.5 % cold leg SBLOCA, RCP on

LOBI/Mod1

KWU 1:712 0.4 % cold leg SBLOCA

LOBI/Mod2

KWU 1:712 1.0 % cold leg SBLOCA

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



SMABRE TYPICAL APPLICATION

108-112,118 108-112,118

7-12 1-6

48-53

FW

125

120

826124827828

824823122822821121

123825

54,56 58

55,57

LETDOWN

CHARGING

13-18

1023-1073(10)

1022-1072(10)

1021-1071(10)

102-107962-1012(10) 961-1011(10)

96-101

1171-1176

411-416

251 -256

261 -266

271-276

281-286

381-386

371-376

361-366

351-356

341-346

331-336

321-326

401-406

113

114

115

116

301 -306

291-296

811 -816

311- 316

39

19-24

42-

47

19261

381386

385

384

383

382

23

22

24

21

266

265

264

263

262 20

39

PRESSURE VESSEL

716-766(10)

7160-7660(100)SPRAY

Loviisa VVER-440 SBLOCA and ATWS Loop seal effects Multilayer steam

generator Reactor vessel with

parallel channels



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



HYDRAULICS HEAT CONDUCTIONIN FUEL ROD

HEAT TRANSFERFROM CLADDING

TO COOLANT

Power to coolant

Heat transfermechanisms

Heat flux

PowerDirectly

to coolant

Dopplertemperature

Power infuelDIFFUSION

PARAMETERSWITH FEEDBACKS

NEUTRONICS

Coolant andsoluble poison

properties

Surfacetemperatureof fuel rodNew coupling of

TRAB-3D and SMABRE cores,= INTERNAL COUPLING

Coupling of physical processes in the core calculation



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



Local fueltemperature

Localpower

HydraulicsHeat TransferNeutronics

to circuit

from circuit

TRAB-3D

CORE CHANNELCOUPLED CORE

SMABRE

Localcladding temperature

Local- coolant density- soluble poison density- coolant temperature

Local powerdirectly to coolant

Local- pressure- mass flux- coolant temperature- heat flux





Options in thermal hydraulics geometryStandard TRAB features for describing BWR bundle geometry are maintainedEach 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



TRAB-3D - SMABRE, STATUS January 20, 2005

=> A working steady state solution has been createdand 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



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



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

the coupled trab-3d-smabre code for 3d transient and accident analyses

Documents

d transient

vtt processesh

dsmabre code

d corebwr2001

d corepwr

d bwr2001

coupled trab

d smabre status