IEA Implementing Agreement on Nuclear Technology for Fusion Reactors

IEA Tritium and Safety Issues in LL Breeders, 11-12 June 2007, Idaho FallsO. GASTALDI

1Associationwith Euratom

IEA Implementing Agreement on Nuclear Technology for Fusion ReactorsLiquid Breeder Blankets Subtask

Coordinating Meeting on R&D for Tritium and Safety Issues in Lead-Lithium Breeders 11-12 June 2007, Idaho Falls, ID, USA

How could be foreseen the tritium mass transfer

F. Gabriel 1, O. Gastaldi 1(presenter), L. Sedano2

(1 CEA, 2 CIEMAT)



The TBM objectives

Demonstrate the capacity of tritium extraction while masteringits inventory

– efficient technological components– efficient remote control– understanding the physical and chemical phenomena and their

interactions– capitalize these knowledge in software tools

Knowledge modelling is required in order to represent in a reliable way the different phenomena (in particular T mass transfer phenomena)



Recall of the needs in term of tritium management

Prediction capabilities of tritium transport modeling tools for tritium transport simulation analyses is a major scientific technical goal of fusion nuclear technology for ITER-TBM:– To help the designer and optimize the technical choices– To better understand future experimental tests– To answer to safety concerns :

• Inventories prediction (help for accountancy methods)• Tritium release estimation



Understanding of T transport phenomena

Many phenomena could have an impact on tritium mass transfer from LLE to helium coolant:– Level of solubility– MHD impact of velocity profile, – Impact of He bubbles contained in PbLi (transfer to gas phase)– Boundary layer resistance– Diffusion under irradiation– Interface phenomena (sorption – desorption)– Isotopic swanping effect– …



Understanding of T transport phenomena

Many phenomena could have an impact on tritium mass transfer from LLE to helium coolant



Different levels of modelingTwo complementary type of tools

– System analyses (ODE system – component = 2 inlets, 2 outlets and a transfer function)

• loop control (main tritium rates, inventory)• global sensitivity analysis

– Component analysis (PDE system – multiphysics analyses)

• qualification of the transfer function• local analysis and component optimization• model validation

Development of reliable system tools, a good knowledge of phenomena is needed

In case of lack of knowledge, refined models associated with analytical experiments are needed



System approach tools developed in EU

Development of engineering tool (system approach) based on

– Steady state– Fick’s law– Simplified components

description– Using mean values

It allows to: – Lead sensivity studies– Determine what are the

major parameters (on which priority must be put in term of R&D)

FW

Helium circuit PbLi circuit

20 %

80 %

1

2

3FW F

f = Fuite

GV

Water

4

5

CPS

HéD

T E S

HéD

PbLiD

EauTC

2

SlipD

CPSD

HéMoyTC _

TESOUTTC _

TESINTC _

SP

3SP

CP

3CP



System approach tools developed in EU Example of result:

Except at the beginning of the range, quite progressive gain

0

5

10

15

20

25

0 50 100

PRF Blanket

Out

goin

g T

Flux

(g/

year

)

0.1

1

10

100

T in

vent

orie

s in

loop

s (g

)

Outgoing T flux (g/year)g/an

T inventory in PbLi (g) T inventory in He (g)



TRICICLO: system tool

Non –linear, (self)-coupled(self)-coupled, multiparametricmultiparametric problem. (at a larger scale)

System approach tools developed in EU: TRICICLO




))(5.4exp()5.4exp(1

5.4)( yLL

Lgyg

“Moving-slab” technique for tritium transport transient computation in HCLL channel (unit symmetry from BB segmentation)

SOURCESOURCE

DIFF. BALANCEDIFF. BALANCE

LOCAL FLUX EXPRESSIONLOCAL FLUX EXPRESSION

zzyxT

kTTQzyxc

zzyxc

D

zyx

CPSTCPST

CPST

CPST

CP

)0,,()()0,,(

)0,,(

)0,,(

,2,

,

,

dyAzyxdyzyxBdyygBA

xyxczdyyxcBAV

SPCP

),,0(2)0,,()(),,(),,(



System approach tools developed in EU: TRICICLOSimplified (reliability of the MODEL?) but TRANSIENT. Main hypothesis:– Diffusion (Fick’s law).– No bubbles in Pb-Li (possible to be taken into account by an

apparent Pb-Li higher T solubility in Pb-Li).– MHD drag transport take in a very simplified way (apparent

i.e.: reduced radial diffusivity).– Interfacial resistance (He-film) can be endorsed in the model

(as a PRF of a barrier).– Radiation effects in the steel (as factors in Diff. & Solub.).– Accounting of isotopic swamping possible (Walbroek

theory).– Dynamic accounting of gas chemistry criteria (oxidation

threshold) on EUROFER and INCOLOY for surface characteristics.

– Precise sizing of INCOLOY 800 Steam Generator and dynamic transfers (in surface limiting regimes through).

– CPS, TES, TRS transfers in/out with system efficiencies (DF factors)




Example of results: – assessment of macroscopic behaviour

– But also sensitivity analysis




Illustration of potential discussions on hypothesis: basic controversial (unknowns ?) to write to express some fluxes.

ISOTOPIC SWAMPING:ISOTOPIC SWAMPING:

T-FLUXT-FLUXHCSHCSBBBB

T-p.p.T-p.p.H-p.p.H-p.p. H´-p.p.H´-p.p.

Does T-flux vary with H-pp. or H´-pp. ? Does T-flux vary with H-pp. or H´-pp. ? Quantit. dependences on T., H, H’ pp ? Quantit. dependences on T., H, H’ pp ?

Experimental data on isotopic swamping is poor. Dependencies from the Theory on Isotopic effect on transport in [F. Waelbroek, Jül 1966, Dez. 1984F. Waelbroek, Jül 1966, Dez. 1984 ] for gas-gas problems assumed.

Isotopic effects would play on BBIsotopic effects would play on BBPC and PCPC and PCSG fluxes SG fluxes



System approach tools developed in EU: TRICICLO ISOTOPIC SWAMPING EFFECTSISOTOPIC SWAMPING EFFECTS: DIFFERENT SITUATIONS: DIFFERENT SITUATIONS

CO-STREAM ISOT. SWAMP.CO-STREAM ISOT. SWAMP.

STEADY STATE ISOT. SWAMP. MODEL IMPLEMENTED IN TRICICLOSTEADY STATE ISOT. SWAMP. MODEL IMPLEMENTED IN TRICICLO

COUNTER-STREAM ISOT. SWAMP.COUNTER-STREAM ISOT. SWAMP.

[F. Waelbroek, Jül 1966, Dez. 1984F. Waelbroek, Jül 1966, Dez. 1984 ] pp. 109

HCLL HCPB• Large permeation numbersLarge permeation numbers (diffusion-limited regimes) (diffusion-limited regimes) for H and Tfor H and T

• Low permeation numbers Low permeation numbers (surface-limited regimes) for H and T co-/counter-stream (surface-limited regimes) for H and T co-/counter-stream

T-FLUXT-FLUX

T-FLUX swamped a factor T-FLUX swamped a factor

T-FLUXT-FLUX


• Large permeation numbersLarge permeation numbers (diffusion-limited regimes) (diffusion-limited regimes) for H and Tfor H and T


T-FLUX swamped factor T-FLUX swamped factor

GASGAS

GASGAS

GASGAS

GASGAS

4)()(

2 bHp

)()(2 fHp

1

• Low permeation numbersLow permeation numbers (surface-limited regimes) (surface-limited regimes) forfor T & large for HT & large for H

)()(2 fHp

4)()(

2 bHp

No effectNo effect




Uncertainties on Isot. Swamp. for TRICICLO

– Basic theory and experimental database for gas-gas mixtures.

– It is uncertain how a low solubility media (LM) in (f) position can reduce H flux- back minimizing isotopic swamping effects.

– Isotopic swamping effects if taken into account should be coupled with presence of permeation barriers and/or EUROFER oxidation conditions (as it is tentatively done in TRICICLO tools) .



General issue: The tritium concentration in the He and in the Pb-15.7Li are evaluated by solving partial differential equations governing the tritium balance, the thermal field and the velocity field in a simplified 2D geometrical representation of the breeder unit at the mid equatorial plan.

Objective: evaluate the sensitivity effect of the Pb-15.7Li velocity profile on engineering outputs 3, and Cf for the inboard and outboard equatorial modules

Blower

Tritium extractionfrom LiPb

FW3

5

He purificationGHe

LiPb

He

mHe

GPbLi

1

2

4

Steamgenerator

Secondary circuit

HCLL Blanket modules

LiPbpurification

Pump

air purification

QHe

mLiPb

Blower


FW3

5

He purificationGHe

LiPb

He

mHe

GPbLi

1

2

4

Steamgenerator

Secondary circuit


LiPbpurification

Pump

air purification

QHe

mLiPb


FW3

5

He purificationGHe

LiPb

He

mHe

GPbLi

1

2

4

Steamgenerator

Secondary circuit


LiPbpurification

Pump

air purification

QHe

mLiPb

Refined models – an illustration




Heat source and tritium source from Monte Carlo analysis, Boussinesq approximation, Inductionless MHD approximation, Inboard magnetic field = 10 T, Outboard magnetic field = 5 T, Toroidal magnetic field, Perfect conductor side walls, Limited diffusion regime for the tritium, Permeation Reduction Factor = 1, Steady state.

B0

inlet a)

radial

poloidal

outlet b)

outlet a)

inlet b)

He

LiPb

B0

inlet a)

radial

poloidal

outlet b)

outlet a)

inlet b)

He

LiPb

A’

A B’

B

B0

inlet a)

radial

poloidal

outlet b)

outlet a)

inlet b)

He

LiPb

B0

inlet a)

radial

poloidal

outlet b)

outlet a)

inlet b)

He

LiPb

A’

A B’

B

( , )

( , )( , )

( , )

minminminmin

r p

r pu r p u

c r p C

aa

a

( , )( , ) 0

( , )

( , ) (1 )

maxmaxmaxmax

r pr p

u r p u

c r p C

in

f

( , )min

freeor

u r p uInlet a)Outlet a)

Inlet b) Outlet b)( , )min

freeoru r p u

( , ) 0 ( , )c r p r p ar b

( , ) 0 ( , )c r p r p ar b

( , ) 0 ( , )c r p r p ar b

0C CK Kl wl w

0C CK Kl wl w

( , )

( , )( , )

( , )

minminminmin

r p

r pu r p u

c r p C

aa

a

( , )( , ) 0

( , )

( , ) (1 )

maxmaxmaxmax

r pr p

u r p u

c r p C

in

f

( , )min

freeor

u r p uInlet a)Outlet a)

Inlet b) Outlet b)( , )min

freeoru r p u

( , ) 0 ( , )c r p r p ar b

( , ) 0 ( , )c r p r p ar b

( , ) 0 ( , )c r p r p ar b

0C CK Kl wl w

0C CK Kl wl w

3w

w

wall

CD dy

y

Engineering Outputs:1

3

r

LiPb inlet

Horizontal stiffening plate

Breeding zone cell

Breeding zone

column

LiPb distribution

box

LiPb outlet

boutlet

f

boutlet

f

fdyC

dyCu

C




FW

A

A’

B’

B

FW

A

A’

B’

B

Temperature distribution (°C) – B = 10 T

FW

A

A’

B’

B

FW

A

A’

B’

B

FWFW

A

A’

B’

B

Tritium concentration (at m-3) – B = 10 T

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04-1.2

-1

-0.8

-0.6

-0.4

-0.2

0x 10

-4 u upper channel velocity profile

meter

m s

-1

NE 2 - 10 TNE 2 - 5 TNE 4 - 10 TNE 4 - 5 T

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04-2

0

2

4

6

8

10x 10

-5 u lower channel velocity profile

meter

m s

-1

NE 2 - 10 TNE 2 - 5 TNE 4 - 10 TNE 4 - 5 T

a) along AA’ b) along BB’

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04-1.2

-1

-0.8

-0.6

-0.4

-0.2

0x 10

-4 u upper channel velocity profile

meter

m s

-1

NE 2 - 10 TNE 2 - 5 TNE 4 - 10 TNE 4 - 5 T

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04-2

0

2

4

6

8

10x 10

-5 u lower channel velocity profile

meter

m s

-1

NE 2 - 10 TNE 2 - 5 TNE 4 - 10 TNE 4 - 5 T


Radial velocity

Sensitivity analysis based on the identification of the parameters of the response surface 31 2

00 0 0

( , ) (1 )BC NC BC NC BC NCaa a

y X X a X X X Xa a a

a0 a1/a0 % a2/a0 % a3/a0 %

3 (g.m-2d-1) – 5 T 2.93 10-3 -0.08 -0.66 -0.10

Cf (mol m-3) - 5 T 0.0454 -0.10 0.26 -0.08

r (%) – 5 T 21.16 -0.08 -0.66 -0.10

3 (g.m-2d-1) – 10 T 2.94 10-3 0.015 -0.21 -0.005

Cf (mol m-3) - 10 T 0.0453 - 0.023 0.066 -0.013

r (%) – 10 T 21.25 0.014 -0.21 -0.005

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.040

0.5

1

1.5

2

2.5

3

3.5x 10

22 lower channel concentration profile

meter

at m

- 3

NE 2 - 10 TNE 2 - 5 TNE 4 - 10 TNE 4 - 5 T

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.040

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2x 10

22 upper channel concentration profile

meter

at m

- 3

NE 2 - 10 TNE 2 - 5 TNE 4 - 10 TNE 4 - 5 T


0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.040

0.5

1

1.5

2

2.5

3

3.5x 10

22 lower channel concentration profile

meter

at m

- 3

NE 2 - 10 TNE 2 - 5 TNE 4 - 10 TNE 4 - 5 T

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.040

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2x 10

22 upper channel concentration profile

meter

at m

- 3

NE 2 - 10 TNE 2 - 5 TNE 4 - 10 TNE 4 - 5 T


Concentration profile

XBC = choice of the fluid boundary conditionXNC = choice of the natural convection




Results:– In the inboard and outboard equatorial HCLL modules

within the above listed assumptions, the permeation rate towards the He circuit, the mean outlet tritium concentration and the ratio of the permeation rate to the production rate are almost insensitive to the magnetic field

– A concentration boundary layer is developed and could be regarded as an equivalent Permeation Reduction Factor of 30 (which was not considered in the previous tritium permeation estimations).

– Such results can be integrated in the system approach tools as PRF

But even with refined model it is needed to solve some persistent lacks of knowledge and uncertainties by experimental campaign



Many uncertainties and persistent lacks

Data lacks (persistent)– Materials databases:

• Pb-15.7Li properties (like T solubility), • Radiation spectral effects on T-transport properties in

EUROFER (& coatings)

– Base phenomena with large potential effect on T-transfers in IBTC

• He-cavitation issues (bubble nucleation impact on tritium)• Validation (or not) of isotopic swamping mechanisms• Soret effect quantification• Trapping models• Coatings impact and associated representation• (He chemistry effects)



Many uncertainties and persistent lacks

Data lacks (persistent)– Systems definition and system parameter unknows.

• Key technological choices: Power Conversion System (SG) for the IBTC

• Unknown dependencies: Do TES/LM efficiencies depend on T p.p. ? - H-dopping effect ??? - (CPS, TRS) scaling & DFs dependencies on (Q2, Q2O) stream p.p. ?



(1) wall impact on solubility ()(2) uncertainty in the eutectic composition ()(3) impact of eutectic disproportioning ()(4) role of M-impurities (¿ ? ?)(5) Other ? LM hydrodynamics (¿--??)

Li vapors and pressure gauge performances (--)

Pb-Li eutectic alloy proposed in the 70´s70´s with intensive characterization of base properties work during 80´s in EU labs (JRC, CEA, KfK) on eutectic (assumed as 83at%Pb-17at %Li).Practical experience determining H-isotope´s solubility in Pb-Li alloys shows how the measurement is potentially full ofpotentially full of parasitic effectsparasitic effects:

Many uncertainties and persistent lacks – illustration (Ks)



- See previous presentation

(11) wall impact on solubilitywall impact on solubility(())- confirmed for some early data

(corrected > 90´s > 90´s measure: by coating capsules: Al2O3, W,..),

- [ 2 o.o.m. values ] & wall material solution activation -Es

(22) uncertainty in the eutecticeutectic composition (composition ())

(33) eutectic d) eutectic disproportioningisproportioning ( ())

Deviation from theoretical eutectic composition [15.7(2)at%Li] at liquid phase and solubility

impact with Li aggregation.

- not systematically checked & driving potentially to incorrect overestimated solubility (in connection with Li-aggregation by clustering)

eut

LieutLiPbs Ks

KsLiatLiatLnK)(

)).(..(1)( 17




Solubility limits for FM corrosion components (Fe, Ni, Mn, Cr) in Pb-Li

(44) role of M-impuritiesimpurities (¿ (¿?)?)

However, tritium solubility in dominant (Fe) is comparable (10-8 at.fr. Pa-1/2) to lower reference solubility data in Pb15.7Li [Reiter], i.e.: amount of impurity comparable to that of measured eutectic.

Steel corrosion products show high solubility limits in Pb15.7Li (Ni > Mn > Fe > Cr).

In this sense, even for unprotected samples and conservatively high corrosion rate values for (cm s-1) thermo-convection velocities (10-100 mg m-2 h-1), impurity impact can be assumed as negligible.




Results: Results: HA-gHA-g (o.o.m higher than actual solubility values and no Sievert´s law) ABANDONED. First HA-p HA-p measurements shown first Sievert´s dependencies and lower values (> 1 o.o.m) ID techniques seem to be as most performant methode for measuring Sievert´s constant and a refinement of HA-p methodes. Allows Allows checking reversibility between absortion & desorption (key issue)

can neutralize possible role of LM hydrodynamics


Two kinds of techniques Two kinds of techniques have been used: have been used:Hot AbsorptionHot Absorption (HA) techniques: gravimetric (HA-g) or pressure drop (HA-p) versions, Isovolumetric Desorption (ID) (desorbed gas pressure evolution after absorption)



Development plan

First step:– Exchange on the way to represent the main transport

phenomena of tritium in LLE

– Establish a common basis of knowledge

– Prioritize the main issues in order to cover the lacks of knowledge

– Develop experimental program in order to solve them (using shared procedure and/or using cross checking)

Second step :– Develop one (or several (depending on the objectives)) open

tool(s) for T transfer modeling



Development plan of the tool – What is the need?Potential users :

Design Engineer component simulation (validated models) sensitivity analysis

complex meshing important CPU time user-friendly interface

Physicist model validation experiment design

interpreted language (easily model implementation) numerical tools access

Numerician software improvement

basic programming level object-oriented language



Development plan of the tool- How could we built it?

Basic facts

not really a commercial tool not that much users quite complex physics

Shared development

open access CFD based tools development divided among partners A team will integrate all developments in a QA version



Development plan - Preliminary road map for the 1st tool

needs specification analysis of needs specification of criteria

selection of a software research of potential software assessment of bests

development of our application model implementation benchmark evaluation

Experimental program in order to reduce data lack qualification of codes



Conclusion (1/2)

Main issues to solve are:– Permeation modeling

• isotopic swamping• surface model• trapping model• coating and interface models• He chemistry effects• experimental validation

– Multiphysic analysis and validation– He bubbling effect– Constitutive law [C = f(P)]



Conclusion (1/2)

Main issues to solve are:– Permeation modeling


– Multiphysic analysis and validation– He bubbling effect– Constitutive law [C = f(P)]

With or without irradiation



Conclusion (2/2)

Main points to treat within the collaboration program:

– Definition of common way to describe phenomena in modeling tools (benchmarking of the different available codes)

– Definition of specific experimental tests in order to obtain main parameters of models





Support to the discussion

Fundamental points:– Establishment of a common database

– Definition of common LLE specifications with QA procedure for its manufacturing – EU can propose some specifications (to be discussed)



Support to the discussionFor each issues what could proposed:– Permeation modelling


– Multiphysic analysis and validation– He bubbling effect– Constitutive law [C = f(P)] – Sievert constant determination

What are the reference laws for these phenomena?– What is the level of reliability?– Which kind of experiments do we need to complete it?– Is there existing facility or analytical bench able to do so?

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