Contents of the presentation

12008 RELAP5 Users Seminar, 18-20 Nov, Idaho Falls, USA

Towards the development of Thermal-Hydraulic Models aimed

at the Auxiliary Systems Design in Nuclear Fusion Technology

1L. Batet, 2L. Sedano, 1C. Queraltó, 1E. Mas de les Valls, 1J.Fradera and 1F. Reventós

1Technical University of Catalonia2Association Euratom-Ciemat for Fusion


Contents of the presentation

• Introduction• Background and context• LM Breeding Blanket designs in EU• BB channels CFD modeling• Auxiliary Systems for BB• Auxiliary systems modeling• EU experimental facilities• Conclusions


Introduction

• As for Gen IV Programmes, the developments in Nuclear Fusion Technology (NFT) are today demanding advanced computational capabilities for simulation and modeling of thermal-hydraulics of liquid metal systems.

• Attending to its functional requirements (DEMO Fusion reactors are today functionally conceived), breeding blanket (and auxiliary systems) is probably the most complex component developed today by energy technology. It represents a key component/system in the way to fusion power production (DEMO).

Breeding Blanket modules are just behind the first-wall, facing plasma. They perform three challenging key functions:

• Coil shielding from plasma radiation• Heat recovery from neutron flux• Tritium breeding


Introduction

• EU plan to test HCLL and auxiliary systems as Test Blanket Module (TBM) in ITER. The development of predictive tools aimed to the simulation of the behavior and to the analysis of those systems and components will be a key issue to licensing and to take advantage of the results from ITER experimental programmes.

• As DEMO breeding blanket, EU is developing diverse liquid metal (Pb15.7Li)-based concepts:– Helium-Cooled Lithium-Lead (HCLL), – Dual-Coolant/Dual-Functional Helium/Lithium-Lead (DCLL), and– Self-Coolant Lithium-Lead Concepts (SCLL).

Water-coolant (WCLL) concept is developed at the French National Programme. A Spanish National Programme (TECNO_FUS) is starting in Spain for Dual-Coolant concept development.


Introduction

• The Thermal-Hydraulic Studies Group (THSG) of the Technical University of Catalonia (UPC), in collaboration with CIEMAT, is trying to reach computational simulation capabilities in relation with breeding blanket liquid metal auxiliary systems for EU ITER TBMs (ITER Test Blanket Modules) and beyond (design of auxiliaries for DEMO HCLL and advanced modular DCLL-like named DRM He/LiPb) .

• A system TH code, like RELAP5-3D, will allow the formulation of the main mass and energy balances.

• The detailed analysis capabilities of a CFD code (UPC is using OPENFOAM) will provide support to the modeling of tritium diffusion and permeation, form-losses evaluation, etc.


Background and context

• Currently foreseen fusion reactors relay on the D+T reaction, which implies achieving tritium self-sufficiency.

• While deuterium is abundant in nature (30g/m3 of water), tritium is not.

• For a 1000 MWe reactor, the mass of tritium needed is some 360 g/day (compare with the production of one CANDU reactor, close to 2 kg/year).

• The Breeding Blanket is the solution proposed to produce tritium inside the reactor facility.

MeV6.17nHeHH 10

42

31

21



MeV

MeV

47.2nHHeLin

78.4HHeLin10

31

42

73

10

31

42

63

10

• Tritium can be produced from Lithium:

• Probability of first reaction is orders of magnitude larger than the second one.

• Natural lithium has 92.44 % 6Li: isotopic enrichment is needed.

• Neutron multiplier needed (Pb or Be) to achieve the necessary Tritium Breeding Ratio (TBR) of about 1.15



• Tritium cycle is complex and tritium control is difficult. • Diffusive properties of hydrogen isotopes are very large

compared with other elements. Permeation is a key issue regarding tritium inventory.

• Inventory control is of utmost importance:– Environmental impact: authorized release (it will depend on the

chemical form of the emissions) 1g/year (27 Ci/day) in front a production of some hundreds of grams/day.

– Self-supplying guaranty (very small margin between the maximum achievable TBR and the TBR needed)


• To demonstrate the tritium self-sufficiency capability, along with licensing requirements, a detailed study of tritium inventory in the channels of the breeding blanket is mandatory.

• Tritium analysis require an exact knowledge of the hydrodynamic profiles in the surface layers, which can only be obtained through CFD simulation.

• CFD codes should be validated under the BB working conditions.

• First full experiment for TBM will be ITER.



Joaquín Sánchez

Test Blanket Module (TBM) : mock-up of a DEMO blanket in ITER test portTBM System : TBM + various associated systems in Tokamak & other buildings

CPS = Coolant Purification System, TWCS vault

HCS = (He) Coolant System, located in TWCS vault, connected with ITER heat rejection system

TES = Tritium Extraction System, located in Port Cell, connected Tritium building

EU ITER-Test Blanket Module


► Structures: RAF/M Steel (HCLL,WCLL) and (DCLL) or SiCf/SiC(SCLL) ► Multiplier/Breeder: Eutectic Pb-Li ► Coolant: He at 8 MPa, 300/500°C (only) or with LiPb at ~460-480°C/650-700°C

► EUROFER He-cooled steel box, highly modular, radial He-cooling plates► T steel: 350°C/550°C► T interface (steel) < 520°C► LiPb velocity < 1 mm/s ► Need of T-perm. Barr.,

► 6Li 90%

► Water-cooled FM steel box, large banana shape modules, poloidal tubes► T steel: 350°C/550°C► T interface (steel) < 520°C► LiPb velocity ~ mm/s ► Need of T-perm. Barr.

► 6Li 90%

► EUROFER/ODS+ SiC/SiC flow channel inserts as el./th.Insulator►LLE breeder & coolant► T steel: 350°C/550°C►T interf. SiC/SiC< 700°C► LLE velocity ~0.1 m/s► 6Li 90%

Water-Cooled LLEblanket (WCLL)

Self-Cooled LL blanket (SCLL)

Helium-Cooled LLE blanket (HCLL)

► SiC/SiC large banana-like structures, ► LLE breeder & total coolant► T interface (SiC/SiC) < 700°C

► LiPb velocity ~ 1 m/s► 6Li 90%

Dual-Coolant LLEblanket (DCLL)

LM Breeding Blanket designs in EU


• CIEMAT and UPC are dealing with HCLL (ITER TBM) and DRM (for DEMO)

LM Breeding Blanket designs in EU

Helium- Cooled Lithium-Lead ½ V port size

.

• In cooperation with ENEA and CEA, a PbLi database compiled.

J.Nuc.Mat: E.Mas de les Valls et al., Lead-lithium eutectic material database for nuclear fusion technology. 2008


BB channels CFD modeling

• THSG (UPC) is developing a CFD tool (based on the open source OpenFOAM code) to simulate the complex phenomena occurring in the liquid BB modules channels, including HCLL and the Dual Coolant Concept.

• Steps to follow:– MHD implementation– Validation using cases with analytical solution– Preparation of the post-processing for tritium– Validation and analysis of numerical diffusion (DT~10-9 m2/s)– Temperature coupling – Validation (?)– Application to the BB modules



• To adapt and validate OpenFOAM it has been necessary to implement a suitable numerical algorithm to simulate the TBM working conditions, i.e. MHD advection coupled to the tritium diffusion/permeation under an intense magnetic field (high Hartmann, high Interaction Parameter) and large thermal loads (neutron radiation).

• The implemented MHD code has been satisfactorily validated.

• Future improvements include:– Implementation of thin wall boundary condition for finite

conductivity walls [Müller,2001]– Implementation of wall functions [Muck,2000][Pothérat,2002] for

Hartmann surface layers (work in cooperation with Alban Pótherat and Vincent Dousset of Coventry University)



• Tritium post-processing as a passive scalar has been implemented and is in a validation process. One difficulty is the low diffusion coefficient (DT~10-9 m2/s) which makes numerical diffusion to be dominant.

• Appearance of lateral surface layer MHD instabilities must be analyzed in detail.

• In general the results obtained with OpenFOAM as a MHD tool are satisfactory.

• Work performed to date is key to future development that should allow the full CFD simulation of liquid metal TBM.




BB channels CFD modeling• 3D application (4 nodii in Hartmann surface layer, 10 in

lateral surface layer), total 777600 control volumes• Re=480 Ha=1740 Gr=2.3·107 and Sc=134• Purely hydrodinamic case

Some instabilities appear that are damped when a magnetic field is introduced

• Temperature-MHD case (not shown):Due to buoyancy, vortices appear, further analysisi needed

U (m

/s)

U (m

/s)

C (m

ol/m3)

C (m

ol/m3)

ST = 6.64·10-12 r -1.2473 mol/m3 s


• Currently there do not exist experiments considering all the phenomena (MHD, heat transfer, tritium and helium)

• Experimental data for uncoupled phenomena (MEKKA, LIBRETTO irradiation tests)

• This fact makes code validation difficult .• An international effort exists (F4E) aiming to

the development of computational tools able to simulate the TBM channels.



Auxiliary Systems for BB

Pb-Li Ancillary System for HCLL TBM

Main goals:• To develop PbLi Ancillary System for the HCLL TBM

• To develop PbLi Purification System to be incorporated in the PbLi ancillary system (e.g. cold trap, magnetic trap,…)

• Study of underlying processes (e.g. PbLi purification, corrosion products transport – dissolution & deposition, impurities behaviour, transmutation products formation and behaviour,…)

• Development and testing of suitable components (e.g. PbLi pump, connecting flanges, valves, diagnostics,…)


Specification for the PbLi ancillary system

• PbLi mass flow in the range: 0.1-1 kg/s (0.3 kg/s is approx. 10 recirculation per day)

• PbLi temperature range: 300-550°C• PbLi mass flow through the purification unit: TBD (estimated approx. 10% of

total flow)• Inert atmosphere: Argon• Maximum pressure in the system: 8 MPa (He leak from HCS)• System structure material: ferritic steel (Cr 10-12%) • PbLi composition:

– Pb-15.7at%Li eutectic alloy– Intermetallic compounds (e.g. PbLi)– Structure material corrosion products (e.g. Fe, Cr, Mn, Ni)– Impurities (e.g. Bi, Sn, Si, Al,…)– Impurities transmutation products (e.g. Po, Tl, Hg,…)

Auxiliary Systems for BB


Pb-Li ancillary system flow diagram

Tank

LDT

CT

TBM

TC

TC

TC

TC

TC

TC

TC

TC

TC

TC

TC

TC

TC

TC

TC

Q1

P

20 kW

20 kW

TC

max. 0,6 m3

Gas injection

Gas injection

Pb-17Li

Flow diagram of the Pb-17Li ancillary circuit

LEVEL

Q2

Q3

TC

TC

TC

TCHe purge TC

V1

V2

V3

V4

V5

V6

V11

V7

V8V10

V12

V9

V15

V13

V14

1 Ro1 Ro2

Ro3Ro4

Ro5

Ro6

Ro7

Ro8

To1

To1

Ch

MCP

Gas

Pb-Li system box

HCLL TBM

Pb-Li tank

Mechanical circulation pump

Heating

Cold trap

Detritiation unit

Sampling

Connection flanges

CT draining

Pb-Li draining

HCLL TBM Pb-Li auxiliary system (1)

PbLi filling

Flow diagram of Pb-17Li ancillary circuit

Conceived and designed NRI-IPP. Chek Rep.

The PbLi auxiliary system should ensure feeding and circulation of PbLi liquid metal in the breeding blanket and removal of tritium produced by a nuclear reaction in TBM.


HCLL TBM Pb-Li auxiliary system (2)

Views of Pb-Li ancillary system box

The PbLi circuit is a closed loop with a slow forced circulation of PbLi. Main components are:• a PbLi feeding and storage tank, • a liquid metal pump (variable flow velocity 0.1 to 1 kg/s),• a detritiation unit to remove Tritium from PbLi (R&D still ongoing),• a cold trap to remove corrosion products and impurities (R&D still ongoing).

The container with the PbLi auxiliary system (dimensions H x L x W: 2.315 m x 2.19 m x 1.6 m) will be placed in the port cell

Conceived and designed NRI-IPP. Chek Rep.


DCLL power extraction system (interest of Sp. Nat. Program)

• A system TH code, like RELAP5-3D, will allow the formulation of the main mass and energy balances.

• Interest on advanced HEX 2 (LM 2ry SC-CO2).

•Interest on compact permeators against vaccum

• Interest on two phase models (helium bred in LiPb)


Auxiliary systems modeling

• Challenges– Tritium and helium transport– Magnetic field– Complex geometries

• A RELAP5-3D model has been developed at UPC of a hypothetic two-fluid experimental facility (partially inspired in Mekka)

• Double loop: NaK/He



Heat up during initial transient



• Difficulties:– MHD head losses (it seems like RELAP5-3D should

compute them, but it does not) have been not considered at the moment. They could be introduced as Re dependent form losses.

– NaK used instead of PbLi, not only because it is the fluid in Mekka but because PbLi property tables are not available in our Athena version.

– No axial fluid conduction.


Compatibility of EUROFER with Pb-Li• Compatibility tests at different Pb-Li temperatures 480-550°C and

flow velocities 1-30 cm/s; HCLL TBM conditions• Various test facilities used (Picolo at FZK, LIFUS-2 at ENEA

Brasimone, Pb-Li facility at NRI Czech Rep.)• Effect of magnetic field (1.7 T) on EUROFER corrosion in flowing Pb-

Li (Latvia)

PICOLO loopEMP = Electromagnetic PumpFM = FlowmeterTS = Test SectionEH = Electrical Heater AC = Air coolerCFHE = Counter Flow Heat Exchanger

MT = Magnetic Trap

LIFUS-2 loop

ENEA-Brasimone

FZK

EU experimental facilities


MHD experiments with a HCLL Mock-Up in the MEKKA

laboratory at FZK

Form-closed barriers

Design of the experiment4 breeder units, poloidal manifold, access tubes

MEKKA laboratory



The TRIEX Facility: test of Tritium extractor, ENEA Brasimone- Nominal mass flow

rate: 0.2 kg/s

- Maximum temperature: 500°C

- Minimum temperature: 350°C

- Stripping gas: Argon

- LM inventory in the loop: about 25 l + 80 l in the circulation tank



Conclusions

• If nuclear fusion has to be a major source of energy in the future it is necessary to overcome some important challenges facing the international scientific community today.

• Several areas of technological knowledge are involved in the design of presently conceived fusion reactors, and brought to their limits.

• One of the most technology demanding components is the Breeding Blanket Module, together with the associated Tritium Extraction System.


Conclusions

• UPC and CIEMAT, together with other Spanish organizations, are trying to acquire de simulation capabilities needed to design and to analyze such complex systems.

• Simulation efforts focus in two lines:– MHD modeling of the BB channels (involving

tritium transport and heat transfer)– System code modeling of the whole BB

system (power extraction + ancillary systems)


Conclusions

• CFD modeling is progressing at good pace, and results to date are encouraging. Though much effort still needs to be devoted to it.

• System code simulation is just starting. The success will depend on our ability to take advantage of the existing code capabilities, and the possibility of improving the existing codes.

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Contents of the presentation