Recent design developments in the EU HCPB TBM
F. Cismondi1, S. Kecskes1, B. Kiss2, F. Hernandez1, L.V. Boccaccini1
1Karlsruhe
3Budapest
Institute of Technology, Germany,
University of Technology and Economic, Hungary
Presented by:
Dr Fabio CISMONDI
Karlsruher Institut für Technologie (KIT)
Institut für Neutronenphysik und Reaktortechnik
e-mail: fabio.cismondi@kit.edu
www.kit.edu
Contest of the study
• Helium
Cooled Pebble Beds (HCPB) and Helium Cooled
Lithium Lead (HCLL) Test Blanket Modules (TBMs) are the
two DEMO blankets concepts selected by EU to be tested in ITER.
• The Test Blanket Systems (TBS) are developed by different Associations
throughout EU.
• The
European Joint Undertaking “Fusion for Energy” is in charge of
delivering the Test Blanket Modules System (TBS) to ITER.
• The
European partners developing the TBS are joint together into a
Consortium Agreement (TBM-CA).
• The TBM CA works under contracts with F4E
• KIT and CEA develop within TBM CA the design of the HCLL and HCPB
TBMs.
1 | Recent developments in the design of the EU HCPB –TBM, Fabio Cismondi
ITER section
Contest of the study
TBM test programme main objectives in ITER
• Demonstrate tritium breeding capability and verify on-line tritium recovery and control systems;
• Ensure high grade heat production and removal;
• Demonstrate the integral performance of the blanket systems in a fusion relevant environment;
• Validate and calibrate design tools and database used in the blanket design process.
DEMO relevancy for the TBMs:
• Maximum geometrical similarity between the design of the TBM and the corresponding DEMO blanket modules;
• Active cooling of the structure by Helium at 8 MPa with 300°C/500°C inlet/outlet temperatures,
• Same structural materials;
• Maximum structural temperature limited to 550°C;
• Same manufacturing and assembly techniques.
• Same functional materials and relevant Be and OSI temperatures.
Structural material
HCPB and HCLL TBMs structural material is the Reduced Activation Ferritic-Martensitic (RAFM) steel EUROFER97.
RAFM steels derive from the conventional modified 9Cr-1Mo steel eliminating the high activation elements (Mo, Nb, Ni, Cu and N).
Main advantages: excellent dimensional stability (low creep and swelling) under neutron irradiation.
Drawback: ductility characteristics considerably lower than austenitic steels and severely reduced following irradiation.
2 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
HCPB TBM design description
1660 mm (poloidal) × 484 mm (toroidal) × 710 mm (radial)
• Robust box (First Wall and Caps)
• Internal structure of Stiffening Grids (SGs)
• 5 backplates (BP) constitute the coolant manifolds
• Horizontal SGs crossing the TBM box to ensure the box
stiffness
First Wall
Plasma side
1660mm
Vertical
SGs
Manifold plates
Back plate
Breeder
Units
By pass
He outlet
He inlet
Caps
Horizontal
SGs
3 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
Purge gas
in/outlet
Breeder Units (BUs):
• Arranged in the space defined by the SGs.
• Filled by ceramic breeder pebbles (Li4SiO4) and Beryllium
neutron multiplier pebbles
• Based on U-shaped Cooling Plates (CPs) extracting the
heat
Helium at 80bar cools the TBM box components and the BUs CPs.
Helium at 4bar purges the Breeder Zone for tritium removal
Design development strategy
Objective: develop a design of the TBM
boxes maximizing the similarities.
FW: larger bending
radius (150mm) in
HCPB TBM
Strategy: synergies are maximized but
differences are kept in the most critical
points to investigate different design
options and minimize the risk.
Critical points:
• FW, fabrication issues
• Manifold, design different for the
different internal engineering of the
2 TBMs
Manifolds: Horizontal SGs
crossing the TBM box (HCPB),
Stiffening rods (HCLL)
4 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
Detailed view of BU design
MF.1 MF.3
MF.2
Radial-poloidal cut
and BU detail
Be
Li4SiO4
MF.4
He at 8 MPa, T 300 to 500 °C
5 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
Purge gas MFs
Detailed view of BU design
MF.1 MF.3
MF.2
First Wall
Be pebble bed
Be pebble bed
Li pebble bed
Be pebble bed
n
PLASMA
Li pebble bed
14,08 MeV
MF.4
Cooling/stiffening grid
Purge gas MFs
6 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
HCPB TBM design life cycle
Start
Structural
concept
Material selection
Neutronic
Nuclear
heating
rate
Tritium
breeding
Ratio
Support concept,
manteinance
Thermalhydraulics
Fabricability
Tritium
recovery
Temperature
of structural,
functional
materials
Coolant
velocity and
pressure
loss
Thermomechanics
Stress
evaluation
Overall performance evaluation
End
7 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
3D CFD model of the TBM box
t1=40s
600
t1=500s
Temperature
distribution
at t1=40s.
Tmax FW
550
Temperature [°C]
Tmax vSGs
Tmax hSGs
500
Tmax Caps
Tmax BP
450
400
350
300
0
100
200
300
400
Time [s]
500
600
700
800
Primary + secondary
stress field on the TBM
at t2=500s
Design Description Document (DDD) of the
TBM box released (complete set of Build To
Print CAD drawings performed)
MPa
0
120
240
360
450
8 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
3D CFD model of the BU
Goal: determine helium coolant mass flow rate in the different
subcomponents and heat fluxes generated in BU and deposed on
the subcomponents.
Breeder Unit
CFD model
Improved modeling of pebble beds region:
•
thermal conductivity temperature and strain
(for Be) dependent
•
thermal
contact
resistance
temperature
dependent.
Thermal contact resistance between pebble beds and
structural material: correlations from Yagi & Kuni used to
define the HTC between pebble beds and structural
material:
 W 
2
h 2   2577 4.327T C   8.91 104 T C 
m K 
9 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
for Li4 SiO4
3D CFD model of the BU
Structural analyses: secondary stresses and structural deformation
∆x ≈ - 0,31mm
∆x ≈ - 0,5mm
∆sbed ≈ 0,4mm
∆x ≈ + 0,09mm
∆x ≈ + 0,17mm
z
y
x
10 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
∆y ≈ + 2,09mm
∆y ≈ + 1,96mm
3D CFD model of the BU
Beryllium:
k as a function of the temperature T and the pebble bed strain ε:
 W 
k
  1,81  0,0012  T  5 10  7  T 2 
 mK 
9,03  1,386 10  3  T  7,6 10  6  T 2  2,1 10  9  T 3  


values of ε=0.2%, 0,32% and 0,5% (corresponding respectively
to a pressure of 2.0, 1.0 and 0.5MPa) have been considered as
being characteristic for the three zones
OSI:
variation of the OSi thermal conductivity with the temperature :
 W 
3
k
  0,768  0,496 10  T
 mK 
The OSi thermal conductivity has the same order of magnitude than the purge gas one and its variation with the
temperature is limited.
11 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
3D CFD model of the BU
Transient analyses performed (typical ITER pulse).
Maximal temperatures:
•
•
•
Low strain region in Be 760˚C.
OSi pebbles 870˚C.
Helium outlet stable at 490˚C by the end of the pulse.
12 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
3D CFD model of the BU
Transient analyses performed (typical ITER pulse).
Maximal temperatures:
•
•
•
Low strain region in Be 760˚C.
OSi pebbles 870˚C.
Helium outlet stable at 490˚C by the end of the pulse.
13 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
3D CFD model of the BU
Transient analyses performed (typical ITER pulse).
Temperatures in Be and OSI at the end of the plasma pulse
Breeder Unit
CFD model
14 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
Transient thermo mechanical analyses of the BU
Goal: Evaluate thermo-mechanical performance of the BU. Design changes implemented to fulfill the design criteria.
The selected design C&S is RCC-MR 2007 completed by SDC-IC ITER rules (adressing irradiation damages).
SM2
Primary stress in base design. Equivalent Von Mises
15 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
Transient thermo mechanical analyses of the BU
Submodel 2: BU manifold center region
BU base design
Design improvement: 20mm thick BU backplate and
stiffeners
16 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
Transient thermo mechanical analyses of the BU
M-Tpe damages assessment
Immediate plastic collapse and instability
Path
3
T [°C]
Pm  Sm [MPa]
Creep
Pm  Pb  keff S m [MPa]
Pm  St (Tmax , t ) [MPa]
Pm  Pb / Kt  St (Tmax , t ) [MPa]
Value
Limit
Margin
Value
Limit
Margin
Value
Limit
Margin
Value
Limit
Margin
Line 1
427
24
167
86%
59
250,5
76%
24
356
93%
54
356
85%
Line 2
425
23
167
86%
27
250,5
89%
23
356
94%
30
356
92%
Line 3
441
131
164
20%
256
246
-4%
131
320
59%
244
356
31%
Line 4
493
167
148
-13%
277
222
-25%
167
250
33%
259
356
27%
Line 5
504
14
144
90%
62
216
71%
14
249
94%
53
249
79%
Line 6
502
24
145
83%
24
217,5
89%
24
249
90%
26
249
90%
Line 7
511
17
143
88%
64
214,5
70%
17
246
93%
58
249
77%
Line 8
504
23
144
84%
23
216
89%
23
249
1%
90
249
64%
Line 9
393
99
174
43%
381
261
-46%
99
NA
NA
377
NA
NA
Line 10
394
112
174
36%
373
261
-43%
112
NA
NA
395
NA
NA
4
17 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
9
10
Transient thermo mechanical analyses of the BU
M-Tipe damages assessment
C-Tipe damage assessment
Ratcheting
Immediate plastic flow localization
Path
Pm  Qm  Se [MPa]
T [°C]
Value
Limit
Margin
Path
T [°C]
(Pm  Pb )max  (P  Q)max  3Sm (T ) [MPa]
Value
Limit
Margin
Line 1
427
82
163
50%
Line 1
427
123
501
75%
Line 2
425
32
163
80%
Line 2
425
45
501
91%
Line 3
441
319
156
-104%
Line 3
441
569
492
-16%
Line 4
493
449
134
-235%
Line 4
493
761
444
-71%
Line 5
504
25
130
81%
Line 5
504
77
432
82%
Line 6
502
32
131
76%
Line 6
502
32
435
93%
Line 7
511
63
127
50%
Line 7
511
116
429
73%
Line 8
504
32
130
75%
Line 8
504
32
432
93%
Line 9
393
161
174
7%
Line 9
393
493
522
6%
Line 10
394
198
174
-14%
Line 10
394
511
522
2%
3
18 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
4
10
Progress in fabrication
•
•
•
•
•
•
Complexity of the BU
manufacturing is mainly in
the CPs: manufacturing
test mock-ups are
addressed to study the
CPs fabrication
techniques.
Complex mounting
sequence: TIG orbital
welding adressed.
19 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
4x Cooling plates (CPs)
2x U-shaped CPs
4x Lateral Wraps
2x U-shaped Lateral Wraps
•
•
•
•
•
1 BU Backplate
1x Inlet + 1x Outlet pipes
2x Ditributor Frontplate
2x Distributor Backplate
2x Grill plate
Progress in fabrication
Complete set of Build To Print CAD drawings performed and Design Description Document (DDD) of the BU released :
20 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
Progress in fabrication
Manufacturing of CP mock-ups
Qualification of TIG orbital welding
Slight bump, poor
torch orientation
Qualification of fabrication techniques
•
•
BU bending radius (Uni Stuttgart)
Cooling channels with Spark Erosion
(industry)
21 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
Qualification in welding laboratories of CEA Saclay to
obtain welding parameters for BU TIG2 (purge gas
pipe with backplate manifold, RCC-MR and ISO
starndards)
BU mock-up testing program in EU
Goal: Design and Procurement of a BU Mock-up
Instrumentation access from the
mock up side: high testing
possibilities and flexibility
BU cell, 1 to 1 BU dimensions
22 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
BU container, optimal shape for:
– the interface with Heblo facility
– leak tightness
– instrumentation
– access to the testing zone
– experimental plan flexibility
Possible access for the
instrumentation from the
back side
TBM design requirements
Several functional requirements for the HCPB Blanket are related to the Solid Breeder performances. They concern:
• Neutronic performances for T self-sufficiency (TBR, Tritium Breeding Ratio);
• Temperature control;
• Long Blanket lifetime;
• Tritium extraction;
• Material compatibility;
• Low tritium inventory in materials;
• Low activation (for waste management and recycling).
Most of these requirements have been quantified for the design of DEMO and FPP, e.g. a calculated TBR not lower than 1.12 is
requested for DEMO and FPP or a blanket lifetime compatible with a neutron fluence of ~15 MWa/m2 is assumed in the FPP.
These requirements are the basis on which sets of specification for the pebble production have been generated.
The connection among these general functional requirements and specification of the pebble (e.g. density, Li-6 enrichment, etc.)
and pebble beds (e.g. effective thermal conductivity, packing factor, etc.) can be reconstructed for some of them, but can be very
complicated in other case.
E.g. the nuclear analyses can correlate well properties like material density, pebble bed packing, ceramic composition with the TBR,
allowing to determine the required properties for the pebble production. More complicated is to state the impact that e.g. the crash
load value has on functional requirements like the T extraction or lifetime; fragmentation of pebble (that can impact the purging
functionality) should be minimised, but a quantification of an upper limit necessitate further R&D.
Then ITER TBM has specific functional requirement. The specifications of the pebbles for TBM are oriented to the specification
generated for DEMO/FPP. I.e. in TBM relevant reactor pebble beds will be tested trying to reproduce the most relevant reactor
conditions. Deviations are introduced to cope with specific ITER relevant requirement; e.g. Li-6 enrichment in the ceramic is used at
the “maximum” enrichment level of 90 in order to compensate the lower T and heat production related to lower neutron wall load in
ITER (0.78 vs. 2.5 MW/m2 in a FPP).
23 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
Conclusions
Main results achieved:
• Definition of C&S for TBM design and analyses
• Definition and analyses of main TBM specific loading conditions
• Transient thermo mechanical analyses of a standard ITER pulse.
• Release of DDD for TBM box and Bus.
Important outcomes of the TBM transient analyses:
• Several junctions present peak stresses : design optimization is on-going.
Open issues:
• Design rules developed mainly for austenitic-type steels (i.e. 316L(N)-IG ITER shielding steel)
• Limited experience with martensitic-type steel in a fusion relevant environment,
• Concerns regarding the validity/degree of conservatism of the C&S rules when taking into account Eurofer97 mechanical properties.
Next priorities:
• Develop dedicated models and studies addressing design issues
• Assess possible requirements and operating scenarios limiting the margins under which the design can evolve.
• Experiments validating FE modeling: pebble beds thermo mechanics, fluid dynamic, structural material behavior
24 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi
25 | Thermo-mechanical performance of the EU TBMs under a typical ITER transient; Fabio Cismondi