Association with Euratom IEA Tritium and Safety Issues in LL Breeders, 11-12 June 2007, Idaho Falls...

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

Associationwith 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

LiPb specifications and the chemistry control

O. Gastaldi 1, L. Sedano2,

(1 CEA, 2 CIEMAT)



What are the main issues ?

Two kinds of problem must be solved in the field of LLE chemistry control:

– All teams involved in LLB studies must work with the same PbLi eutectic

specifications of the common eutectic %Li specifications of maximum impurities content

– During operation of TBM, the chemistry must be controlled



Summary Li-Pb eutectic (LLE) characteristics should be established according

to nuclear material QA requirements (ISO3131/- 1, /-5, Light Metals and light alloying metal: methods for processing and treatment) … as it will be demanded for the tons of TBM needs in ITER

QA demands to (LLE) refer to Constitutive and to Compositional characteristics

QA constitutive specifications apply for accurate Li title and control of Li structural micro-aggregation

Compositional specifications apply for impurity levels

Some key materials Fusion Technology properties can largely change through deviations (ex.: Li aggregation or Li in excess in an supposed eutectic can have a large effect on tritium solubility)

Production and material testing routes should be fixed according to QA standards

Lead-Lithium Eutectic QA as Nuclear Material



ElementContent (ppm)

Ag <1

Al 1

As 40

Au <1

Cr <3

Cu <1

Cd <1

Fe 13

Ga <1

Hg <1

In <1

Li 0.68%

Ni 7

P <10

Pb Balance

Sb <10

Su <5

Ti <10

Bi 0.02%

Some impurities typically linked to Lithium (1 ppm Al) might be used for a fast homogeneity test

Major interest is of course to minimize Bi content (below tenths ppb).

Compositional specifications apply for impurity levels



Figure 1: Phase diagram of Pb-Li system [Tegze and Hafner, 1989]

Y Ref. at.% Li Alloy origin T-control Analysis Uncertainties

88 [5] 16.98 CEA, Li(99.5) and Pb(99.994)

-- -- --

91 [6] 16.55 Alloyed at home Poor detail N.S.

91 [3] 16.98 laboratory, Li(99.4) from Metallgesellschaft with 0.5 Na, 0.01 K, 0.03 Ca,

<0.01 Al, <0.03 Si and Pb(99.99) from Ventron

Thermal analysis (Ni-

CrNi-thermocouples

) and thermal differential

analysis with a Netzsch DTA

AAS 0.01 wt.%, oxygen

impurities were below

the hot extraction

method (0.01%)

92 [7] 15.7 laboratory, use of an electromagnetic pump to ensure the homogeneity

measurement of electrical

resistance as a function of T

--

05 [10] 15.8 laboratory, use of a three-phase MHD stirrer. Comparison with a

sample from METEAUX-SPECIAUX (1993) and

another from Jost-Hinrich Stachov Metallhandel

(2003)

X-ray phase study,

AAS

1.3 at.%

06 [11] 16.97 laboratory, Li(99.8) and Pb(99.99)

-- 0.20 wt.%

LEAD-LITHIUM EUTECTIC TITTLE

Li chemical activity determine LLE activity: title has large impact on NFT.

Tritium solubility in LLE would largely depends on Li-disproportioning by bad mixing or local aggregation. Other properties less modified

2at% Li deviations are unacceptable from QA of LLE as Nuclear Material



- Errors in estimation depend on the experimental protocol for production and for its determination

-T data for a total of 52 points {0 < xLi (at%) <22.2}, show to decrease smoothly from the melting point of pure Pb to the eutectic point (15.7(2) at% Li, 235(1)°C, [P. Hubberstey et al, JNM (1992)],

- a single liquid phase maintained over the composition range from 13.7 to 18.0 at% Li, (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)

- Mixing light Li with heavy Pb and large homogeneity is not an easy technical mater

eut

LieutLiPbs Ks

KsLiatLiatLnK

)()).(..(1)( 17

LEAD-LITHIUM EUTECTIC TITTLE

Uncertainty in the eutectic eutectic composition (composition ( T-soly) T-soly)

Disproportioning by badDisproportioning by bad mixing (mixing ( T-soly) T-soly)

Disproportioning effects can be like this



It is the J-H Stachow GmB commercial alloy. Test performed by Freibergs (UPUL, Latvia) 2005 This eutectic has been used for solubility determinations (!!!!)

The practical situation when homogenity is checked !!!:

This eutectic is used in present irradiations LIBRETTO -4 (!!!!)



Li dosage control and MHD stirring technology seems needed for mixing

Feasibility at semi- industrial scale ?

Mixing drawbacks:

fast alloying rates and very difficult local temperature control

possibility of formation of hard melting Li5Pb2, LiPb, Li3Pb ( Higher Li activity so Tritium solubility higher than in the eutectic !!!! )

Different commercial production



Roadmap for Pb-Li eutectic QA guarantees

Revision of set of ISO norms (ISO3131/- 1, /-5, Light Metals and light alloying metal: methods for processing and treatment) in force for Nuclear Materials and IAEA Regulations.

Fixing Material specification in terms of: (1) maximum allowable impurity contents, (2) Li contents global deviations (ex. < ± 0.2 Li at%) and (3) homogeneity criteria (ex. maximum size and distribution of Li and other Li-Pb phases aggregates),

Establishment of a production route (with specification of endorsing ISOs) according to previous material QA criteria.

Establishment of set of certification tests for Material QA (fine calorimetry at eutectic, x-ray phase study, Atomic Absorptions Technique, …)

Lack of database reproducibility for key FT properties can not even more potentially be justified in terms of material uncertainties



During operations

What has to be controlled in LLE? – Control of impurities must be insured:

• In order to guarantee tritium inventory

• In order to allow a good analysis of experimental tests

• In order to avoid precipitations

– Dynamic control of Li content

– Follow-up of tritium concentration



During operations

What is needed in term of measurement tools:– For oxygen: Technology is known (electrochemical

probes): validation in real conditions (flow rate mainly, magnetic field,…) must be checked

– For tritium:• Specific constraints:

– Small variation of tritium in LiPb at each pass in the TBM

– Short duration of pulses• Then dynamic measurement is needed (with good time

response)



During operations

Measurement tools:– For tritium:

• Existing tools:

– Use of permeator sensors

– Time response is too slow to insure dynamic follow-up of tritium content in TBM (need to

reach equilibrium)• What are the alternative solutions?



During operations

For impurities control what are the main issues:

– Li title adjustement (mainly for DEMO application) - Without doing agregates in order to guarantee homogeneous mixture

– Cold trap optimisation (mainly for DEMO application)



Main points to treat

Define a reference specifications for LLE composition (EU can propose it)

Define a production route with associated QA

Define develop and test tritium measurement tools (with short time response) efficient in realistic conditions (dynamic loop)



References

[33, Schulz,1986]

[55, Fauvet st Sannier, 1988]

[66, Reiter, 1991]

[77, Hubberstey, 1992]

[1010, Freibergs, 2005]

[1111, Stankus 2006]

Association with Euratom IEA Tritium and Safety Issues in LL Breeders, 11-12 June 2007, Idaho Falls...

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