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Loads on RPV Internals in a PWR due to Loss -of-Coolant Accident consideringFluid -Structure InteractionDr. P. Akimov, Dr. M. Hartmann, L. ObereisenbuchnerFluid DynamicsStuttgart, May 24, 2012
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.3
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
Content
Motivation
Fluid-structure interaction
Introduction of computer codes used� STRAC / HAUPT
� LOCAFLEX
Sample LOCA calculations
Summary
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.4
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
Motivation
In the case of a LOCA (e.g. break at themain coolant line):
Allowable deformations of Control Rod Guide Tubes must not be exceeded
� ensure safe reactor shutdown
Integrity of the RPV internals(e.g. Core Support Barrel,Support Plates, Support Columns)
� ensure sufficient core cooling
RPV and internals
Core SupportBarrel
UpperSupport
Plate(USP)
UpperCore Plate
(UCP)
LowerSupport Plate
UpperSupportColumns
Control RodGuide Tubes
CoreDowncomer
Upper Plenum
Take into account the main effects of the fluid-structure interaction in the computational models
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.5
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
Fluid -structure interaction (FSI)FSI effects with regard to the
Core Support Barrel (CSB):FSI effects in the Upper Plenum:
buckling of the CSB
deflection of the CSB
bending of the tubularstructures in the Upper Plenum
HotNozzle
Core
Upper Support Plate
Upper Core Plate
Zone ofreducedpressure
Postulatedbreak
Downcomer
RPV
CSB
ColdNozzle
Strong reduction of incoming pressure waves due to FSI
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.6
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
Sequential vs. coupled FSI approaches
Fluid
Structure
Fluid Forces
Displacement &Stresses
Fluid Structure
Fluid Forces
Displacements
Stresses fromdisplacements
Assessment of the results
No FSI effects!
Sequential approach: FSI approach:
Covering global loads,not realistic
More realistic, load reduction effects due to structural reaction
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.7
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
Computer codes
Upper plenum internals
� Code STRAC / HAUPT
Lower internals, RPV, and FuelAssemblies (FAs)
� Code LOCAFLEX
RPV and internals
Core withFAs
Upper Plenum
Core SupportBarrel
Lowerinternals
Code STRAC / HAUPT(upper plenum internals)
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.9
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
STRAC / HAUPTMain features
1D and 3D componentsPIPE, TEE, VALVE, PUMP,STGEN, VESSEL, CORE
Non-homogeneous,non-equilibrium modelling2 fluid flow, 2 phase flow
Modifications and model extensionsEvaluation of forces, valve models,interface to structure programs, e.g., HAUPT
Fluid-structure interaction of the upper plenum internals is considered
STRAC is based on code TRAC (Transient Reactor Analysis Code) Loop 1
(hot)Loop 2(hot)
Loop 2(cold)
Loop 3(cold)
Loop 3(hot)
Loop 4(hot)
Loop 4(cold)
Loop 1(cold)
CSB RPV
Guide Tube forMeasurement
SupportColumn
Control RodGuide Tube
3D grid for the RPV(horizontal cross section)
Code LOCAFLEX(RPV, the core, and RPV internals)
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.11
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
LOCAFLEXMain features
Fluid: The whole primary coolant volume is included.Modeled are: the RPV with internals, the core,steam generators, pumps, etc
1D, 2 phase flow
Structure: The model consists of the RPV, the core, and the RPV internals (except for the upper plenum internals)
New object-oriented developments allow for complex structural models generated by ANSYS software with nonlinear couplings
Fluid-structure interaction in the downcomer is considered
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.12
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
LOCAFLEXFluid model of the RPV
RPV and internals
LowerSupport Plate
Down-comer
UpperSupport
Plate
UpperCore Plate
Core
= 2D Network
ColdNozzle
HotNozzle
Upper SupportPlate
Upper CorePlate
Lower SupportPlate
Downcomer
Core
R309
R308
R307
R306
R305
R300
R299
R298
R297
R9 – R144
R8 – R143
R7 – R142
R6 – R141
R5 – R140
R4 – R139
R3 – R138
R2 – R137
R1 – R136
R289 – R296R386 – R393
Cor
e B
ypas
s
R303
R302
R304
R310R328R346R364
R327R345R363R381
Loop Level
R301
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.13
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
LOCAFLEXStructural model (RPV)
Rigid beam model of the RPV
1
10
2
3
15
4
5
11
6
7
12
8
13
14
9 26
27
28 29 30 31
32
33
18
19
20 21 22 23 24
25
17
Parts of the RPV and internals that are in this model
Coupling to the Lower Support Plate
Coupling of the RPV supportto the building fixpoint
Coupling to the CSB Flange
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.14
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
UCP
USP
CRGA-C
USP
UCP
Controlassemblies
LOCAFLEXStructural model (Lower internals)
Extended FE-model with over 2000 MDOFs *)
Parts of the RPV and internalsthat are in this model*) MDOFs = Master Degrees of Freedom
CB
HR
UCP
CRGA-C
USP
HOLD-DOWN-SPRING
Coreschroud
LSP
CSB
UCP
USP
Hold-Down Spring
Hold-DownSpring
Controlassemblies
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.15
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
LOCAFLEXStructural model (Upper plenum internals)
RPV and internals
UpperSupport
Plate
UpperCore Plate
Control RodGuide Tubes
Fluid forceson the tubular
structures
The fluid forces due to the pressure waves (from STRAC/HAUPT) are applied in LOCAFLEX directly to the tubular structures
Realistic coupling mechanism between the UCP and the USP thanks to the detailed FE models of the upper plenum internals
UCP
USP
CRGA-C
USP
UCP
Controlassemblies
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.16
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
LOCAFLEXStructural model (Core)
Horizontal row models of Fuel Assemblies (FAs)(5 row models for 1 direction are shown with colors)
Loop 1(cold)
Loop 2(cold)
Loop 2(hot)
Loop 1(hot)
Loop 3(hot)
Loop 4(hot)
Loop 4(cold)
Loop 3(cold)
Core-X
Core-Y
Core-X
Core-YCoupling to UCP
Couplingto LSP
Impact couplings Shroud / FA and FA / FA
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.17
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
LOCAFLEXCoupling between fluid & structure models
RPV and internals
Core SupportBarrel
UpperSupport
Plate
UpperCore Plate
LowerSupport Plate
UpperSupportColumns
Control RodGuide Tubes
CoreDowncomer
CoreShroud
Fixpoint
► Downcomer
► Downcomer
► inside CSB
► …
CSB
RPV
CSB
► CSB Flange
► LSP
► UCP
► RPV
► …
RPV
FAs
FAs
Building fixpoint
By means of
Structure
By means of
Fluid
Sample LOCA calculations
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.19
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
0.0 0.1 0.2 0.3 0.4 0.5 0.6TIME (S)
-1.0
-0.5
0.0
0.5
Sca
led
forc
e (C
SB
/CS
Bm
ax)
without FSI
Y directionX direction
LOCA calculation: Cold leg breakResults
Total Force on the CSB
Deflection of the CSB due torapid decompression
RPV with 4 loops
X
Y
Loop 1(cold)
CSBRPV
Loop 4(cold)
Loop 4(hot)
Loop 3(hot)
Loop 3(cold)
Loop 2(cold)
Loop 1(hot)
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.20
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
LOCA calculation: Cold leg breakFSI effects
With FSI � more realistic analysisas to peak loadings & frequencies
0.0 0.1 0.2 0.3 0.4 0.5 0.6TIME (S)
-1.0
-0.5
0.0
0.5
Sca
led
forc
e (C
SB
/CS
Bm
ax)
without FSI
Y directionX direction
Y directionX direction
0.0 0.1 0.2 0.3 0.4 0.5 0.6TIME (S)
-1.0
-0.5
0.0
0.5
Sca
led
forc
e (C
SB
/CS
Bm
ax)
with FSI
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.21
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
Summary
Accurate and reliable numerical tools —STRAC / HAUPT and LOCAFLEX — for loads analyses in the assessment of safety for nuclear power reactors
Allowing for Fluid-Structure Interaction and a complete consideration of dynamics lead to more realistic analyses of loads on the RPV internals
New developments in LOCAFLEX allow for more realisticand accurate calculations
Jahrestagung Kerntechnik 2012 – Loads on RPV Internals in a PWR due to LOCA considering Fluid-Structure Interaction – Dr. P. Akimov – May 24, 2012 - p.22
Property of AREVA NP GmbH, all rights are reserved. Liability restricted, see notice.
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Loads on RPV Internals in a PWR due to Loss -of-Coolant Accident consideringFluid -Structure InteractionDr. P. Akimov, Dr. M. Hartmann, L. ObereisenbuchnerFluid DynamicsStuttgart, May 24, 2012
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