Www.kit.edu Presented by: Dr Fabio CISMONDI Karlsruher Institut für Technologie (KIT) Institut für Neutronenphysik und Reaktortechnik e-mail: [email protected]

www.kit.edu

Presented by:

Dr Fabio CISMONDIKarlsruher Institut für Technologie (KIT)

Institut für Neutronenphysik und Reaktortechnik e-mail: [email protected]

Recent design developments in the EU HCPB TBM

F. Cismondi1, S. Kecskes1, B. Kiss2, F. Hernandez1, L.V. Boccaccini1

1Karlsruhe Institute of Technology, Germany, 3Budapest University of Technology and Economic, Hungary

• 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.

Contest of the study

ITER section

2 | Recent developments in the design of the EU HCPB –TBM, Fabio Cismondi

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 .

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.

3 | Recent developments in the design of the EU HCPB-TBM, Fabio Cismondi

HCPB TBM design description

First Wall

Vertical SGs

Breeder Units

Horizontal SGs

Caps

Pla

sma

sid

e16

60m

m

710mm

Manifold plates

Back plate

He outlet

He inlet

Purge gas in/outlet

By pass Helium at 80bar cools the TBM box components and the BUs CPs. Helium at 4bar purges the Breeder Zone for tritium removal

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

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


Design development strategy

Objective: develop a design of the TBM boxes maximizing the similarities.

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

FW: larger bending radius (150mm) in HCPB TBM

Manifolds: Horizontal SGs crossing the TBM box (HCPB), Stiffening rods (HCLL)



Detailed view of BU design

Purge gas MFsB

ack

pla

te

MF.1

MF.4

MF.3 MF.2

Li4SiO4Be

Radial-poloidal cut

and BU detail

He at 8 MPa, T 300 to 500 °C


Detailed view of BU design

Be pebble bed

Be pebble bed

Be pebble bed

Li pebble bed

Li pebble bed

PLA

SM

A

First Wall

n

14,08 MeV

Cooling/stiffening grid

Purge gas MFsB

ack

pla

te

MF.1

MF.4

MF.3 MF.2


HCPB TBM design life cycle

Start

Structural

conceptMaterial selection

Neutronic

Tritium

breeding

Ratio

Nuclear

heating

rate

Thermal-

hydraulics

Temperature

of structural,

functional

materials

Coolant

velocity and

pressure

loss

Thermo-

mechanics

Stress

evaluation

Overall performance evaluation

End

Tritium

recovery

FabricabilitySupport concept,

manteinance


3D CFD model of the TBM box

300

350

400

450

500

550

600

0 100 200 300 400 500 600 700 800Time [s]

Te

mp

era

ture

[°C

]

Tmax FW

Tmax vSGs

Tmax hSGs

Tmax Caps

Tmax BP

t1=40s t1=500s

Primary + secondary stress field on the TBM at t2=500s

MPa

0 120 240 360 450

Temperature distribution at t1=40s.

Design Description Document (DDD) of the TBM box released (complete set of Build To Print CAD drawings performed)


3D CFD model of the BU

First Wall

Vertical SGs

Breeder Unit

CFD model

Horizontal SGs

Cooling Plates

Goal: determine helium coolant mass flow rate in the different

subcomponents and heat fluxes generated in BU and deposed on

the subcomponents.

Improved modeling of pebble beds region: •thermal conductivity temperature and strain (for

Be) dependent•thermal contact resistance temperature

dependent.

Thermal contact resistance Thermal contact resistance between pebble beds and

structural material: correlations from Yagi & Kuni Yagi & Kuni used to

define the HTC between pebble beds and structural

material:

4424

21091.8327.42577 SiOLiforCTCT

Km

Wh



∆x ≈ - 0,5mm

∆x ≈ - 0,31mm

∆x ≈ + 0,09mm

∆x ≈ + 0,17mm

∆sbed ≈ 0,4mm

∆y ≈ + 2,09mm

∆y ≈ + 1,96mm

Structural analyses: secondary stresses and structural deformation

y

x

z



Beryllium:Beryllium:k as a function of the temperature T and the pebble bed strain ε:

39263

27

101,2106,710386,103,9

1050012,081,1

TTT

TTmK

Wk

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:OSI:variation of the OSi thermal conductivity with the temperature :

TmK

Wk

310496,0768,0

The OSi thermal conductivity has the same order of magnitude than the purge gas one and its variation with the temperature is limited.



Transient analyses performed (typical ITER pulse).Transient analyses performed (typical ITER pulse).

Maximal temperatures: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.



Transient analyses performed (typical ITER pulse).Transient analyses performed (typical ITER pulse).

Maximal temperatures: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.



First Wall

Vertical SGs

Breeder Unit

CFD model

Horizontal SGs

Cooling Plates

Transient analyses performed (typical ITER pulse).Transient analyses performed (typical ITER pulse).Temperatures in Be and OSI at the end of the plasma pulse


Transient thermo mechanical analyses of the BU

Primary stress in base design. Equivalent Von Mises

SM1

SM2

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).



BU base designBU base design

Design improvement: 20mm thick BU backplate and Design improvement: 20mm thick BU backplate and

stiffenersstiffeners

Submodel 2: BU manifold center region



M-Tpe damages assessment

3 4 9 10



M-Tipe damages assessment

3 10

C-Tipe damage assessment


Progress in fabrication

• 4x Cooling plates (CPs)

• 2x U-shaped CPs

• 4x Lateral Wraps

• 2x U-shaped Lateral Wraps

• 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.

• 1 BU Backplate

• 1x Inlet + 1x Outlet pipes

• 2x Ditributor Frontplate

• 2x Distributor Backplate

• 2x Grill plate



Complete set of Build To Print CAD drawings performed and Design Description Document (DDD) of the BU released :Complete set of Build To Print CAD drawings performed and Design Description Document (DDD) of the BU released :



Qualification of fabrication techniquesQualification of fabrication techniques

• BU bending radius (Uni Stuttgart)BU bending radius (Uni Stuttgart)

• Cooling channels with Spark Erosion Cooling channels with Spark Erosion (industry)(industry)

Slight bump, poor

torch orientation

Qualification in welding laboratories of CEA Saclay to Qualification in welding laboratories of CEA Saclay to

obtain welding parameters for BU TIG2 (purge gas obtain welding parameters for BU TIG2 (purge gas

pipe with backplate manifold, RCC-MR and ISO pipe with backplate manifold, RCC-MR and ISO

starndards)starndards)

Manufacturing of CP mock-ups Qualification of TIG orbital welding


BU mock-up testing program in EU

BU cell, 1 to 1 BU dimensions

BU container, optimal shape for:– the interface with Heblo facility– leak tightness– instrumentation– access to the testing zone– experimental plan flexibility

Instrumentation access from the

mock up side: high testing

possibilities and flexibilityPossible access for the

instrumentation from the

back side

Goal: Design and Procurement of a BU Mock-up


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);Neutronic performances for T self-sufficiency (TBR, Tritium Breeding Ratio);•Temperature control;Temperature control;•Long Blanket lifetime;Long Blanket lifetime;•Tritium extraction;Tritium extraction;•Material compatibility;Material compatibility;•Low tritium inventory in materials;Low tritium inventory in materials;•Low activation (for waste management and recycling).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.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. 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).


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

26 | Thermo-mechanical performance of the EU TBMs under a typical ITER transient; Fabio Cismondi

Documents

Www.kit.edu Presented by: Dr Fabio CISMONDI Karlsruher Institut für Technologie (KIT) Institut für Neutronenphysik und Reaktortechnik e-mail: [email protected]