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IEA Implementing Agreement on Nuclear Technology for Fusion Reactors

IEA Implementing Agreement on Nuclear Technology for Fusion Reactors Liquid 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

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IEA Implementing Agreement on Nuclear Technology for Fusion Reactors

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  1. IEA Implementing Agreement on Nuclear Technology for Fusion Reactors Liquid Breeder Blankets Subtask Coordinating Meeting on R&D for Tritium and Safety Issues in Lead-Lithium Breeders11-12 June 2007, Idaho Falls, ID, USA LiPb specifications and the chemistry control O. Gastaldi1, L. Sedano2, (1 CEA, 2 CIEMAT) O. GASTALDI

  2. 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 O. GASTALDI

  3. Lead-Lithium Eutectic QA as Nuclear Material 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 O. GASTALDI

  4. Compositional specifications apply for impurity levels • 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). O. GASTALDI

  5. LEAD-LITHIUM EUTECTIC TITTLE Figure 1: Phase diagram of Pb-Li system [Tegze and Hafner, 1989] • 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 O. GASTALDI

  6. LEAD-LITHIUM EUTECTIC TITTLE • Uncertainty in the eutectic composition ( T-soly) • - Errors in estimation depend on the experimental protocol for production and for its determination • W-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, (3) eutectic disproportioning () • Disproportioning by bad • mixing ( T-soly) 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 Disproportioning effects can be like this O. GASTALDI

  7. The practical situation when homogenity is checked !!!: • It is the J-H Stachow GmB commercial alloy. • Test performed by Freibergs (UPUL, Latvia) 2005 • This eutectic has been used for solubility determinations (!!!!) • This eutectic is used in present irradiations LIBRETTO -4 (!!!!) O. GASTALDI

  8. Different commercial production • 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 !!!! ) • Li dosage control and MHD stirring • technology seems needed for mixing • Feasibility at semi- industrial scale ? O. GASTALDI

  9. 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 O. GASTALDI

  10. 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 O. GASTALDI

  11. 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) O. GASTALDI

  12. 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? O. GASTALDI

  13. 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) O. GASTALDI

  14. 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) O. GASTALDI

  15. O. GASTALDI

  16. References [3, Schulz,1986] [5, Fauvet st Sannier, 1988] [6, Reiter, 1991] [7, Hubberstey, 1992] [10, Freibergs, 2005] [11, Stankus 2006] O. GASTALDI

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