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of Japanese PbLi-T Research Activities
         and Related Topics

                Takayuki Terai

              University of Tokyo

         Coordinating Meeting on R&D for
Tritium and Safety Issues in Lead-Lithium Breeders
                    (PbLi-T 2007)
          Japanese PbLi-T Research Activities
                 and Related Topics
•   Japan has not proposed a specific Pb-Li TBM design, but plans to contribute to TBM test
    by collaboration with other parties.

•   Tritium Behavior in Pb-Li
    - Diffusivity, Mass-transfer and Permeability by in-pile test (University of Tokyo)
    - T recovery by permeation window method (University of Tokyo)
    - Diffusivity and solubility of H and D (Kyushu University)
    - Permeability in a loop (Kyoto University)

•   Permeation Barrier Coating
    - Al2O3, Y2O3 coating (University of Tokyo)
    - Er2O3 coating (NIFS, University of Tokyo, JUPITER-II)

•   Related Topics
    - Advanced blanket concept based on PbLi – SiC – He combination
      with a LiPb-He dual coolant loop (Kyoto University)
    - Conceptual design of ICF reactor “KOYO-F” using PbLi as a coolant and breeder
      (Osaka University)
    - Q hehavior in SiC (Shizuoka University)
      Tritium Release Behavior from Liquid breeders under a Blanket
   -Simulated Condition (under Neutron Irradiation at High Temperature)

                                   Silica gel    Water Bubbler
          Gas supply   He +                                      He + H2
                       H2                                        (HT)

Reactor                                                   Polyethylene
 core                                                     Blocks                        (Tokyo)
                                                        Container with heater

           Schematic diagram of the irradiation
 Fast neutron source : 108~109n/cm2s                              Pb-17Li, LiF-BeF2(Flibe), Sn-20Li
                                                                  673-973 K
                          ("YAYOI" of the University of Tokyo)
                                                                  Tritium chemical species (HT, HTO, TF, etc.)
 Tritium generaton rate : ~40Bq/g-Li,s
                                                                  Tritium diffusivity
 Purge gas : pure He, He + 0.001-10%H2 pure H2 He+2%HF            Tritium release rate
 irradiation time : for about 150 minutes                         Tritium permeation through piping materials
Diffusion Coefficient of Tritium in Liquid Pb-17Li

  Under the condition of He-H2 (pH2 > 103 Pa) purge gas,
  Diffusion of T in liquid Pb-17Li is dominant, and
      D / m2s-1 = 2.50 x 10-7 exp ( -27.0 kJmol-1 / RT)

                      (Terai et al., J. Nucl. Mater. 187 (1992), 247.)
      Mass-transfer Coefficient of Tritium from
       Liquid Pb-17Li to environmental gas

Mass-transfer coefficient increases with pH2 in He-H2 purge gas,
and at pH2 > 103 Pa, it is almost constant and given by
    KD / ms-1 = 2.5 x 10-3 exp ( -30.7 kJmol-1 / RT)
This process is governed by the T diffusion in liquid-film, and the film
thickness is 0.2 mm in this condition.
          (Tokyo)        (Terai et al., Fus. Engng. and Des. 17 (1991), 237)
 Tritium Permeation through Piping Materials
            Facing Liquid Pb-17Li

In case of a-Fe, no stable oxide film cannot formed on the surface, and T
permeation behavior is described by the T diffusion in a-Fe,
while in case of SS316, a stable oxide film of Cr2O3 and FeCr2O4 decreases
T permeation rate with a reduction factor of 30 – 300 depending on pH2.

                     (e.g. Terai et al., J. Nucl. Mater. 191-194 (1992), 272)

 Experiments of recovery of hydrogen isotopes from Pb-
-Measurement of diffusivity, solubility and isotopic exchange rate constant-
                                                                                                                                                   L2      9L2      25L 2   
                                                                                                 JL                                        L2                       
                                                                                                                                                  4 Dt  e 4 Dt  e 4 Dt    
                                                                                                                                  2              e
                                                 c LiPb DLiPb H K S                             p   H 2 up    p H 2 down         DLiPb H t 

                                                     Concentration of hydrogen [ppm]
                                                                                                       973K                           100%-H2
                                                                                       250             773K



                                   Li-Pb                                                50

                                                                                             0                 2              4             6            8          10
                                                                                                                                      Time [h]

 Experimental apparatus for LiPb-H2(D2) system           Comparison between experiment and calculation

                                                                                         S. Fukada, Kyushu University group
           Dependences of DH and SH on temperature for Pb-17Li-H
             system and comparison with previous researches
                                         Temperature [ C]                                                                          o
                                                                                                                       Temperature [ C]
                             700 600    500    400        300                                             700 600    500    400         300
                                                                                                                                           10 Pa
 Solubility [1/Pa ]

                                                                                                                                           10 Pa


                                                                           Diffusivity [m /s]
                                                                                                     -8                                        3
                      10                                         5
                                                               10 Pa                            10                                         5x10 Pa

                                                                 4                                                                           3
                                                               10 Pa                                                                       10 Pa
                                                               5x10 Pa                                                                     F.Reiter
                                                               10 Pa                                                                       T.Terai
                                                               F.Reiter                                                                    Okamoto
                       -7                                                                            -9
                      10                                       Chan and                         10

                       -8                                                                        -10
                      10                                                                10
                            1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0                                   1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9
                                          1000/T [1/K]                                                                 1000/T [1/K]

                            Hydrogen solubility in Li0.17Pb0.83                                            Hydrogen diffusivity of Li0.17Pb0.83

                                                 618700                                                                    8   11590
                      K LiPb H     2.110 exp(        )                                DLiPb H              1.8  10 exp(        )
                                                    RT                                                                            RT
                                                                                                S. Fukada, Kyushu University group
    Li activity of LiXPb1-X-H2 system eutectic alloy

                                       Pb         Pb




•   When xLi>0.5, electric charge of Li+ is not shielded by Pb atoms, and Li+-H- ionic
    binding is major in LiXPb1-X eutectic alloy.        Activity of Li is higher.
•   When xLi<0.5, electric charge of Li+ is shielded by Pb atoms, and Li+ and H- ions
    are not combined directly.         Activity of Li is the lowest.

                                                       S. Fukada, Kyushu University group
 Design of He-LiPb counter-current extraction tower
                for tritium recovery
            He out
                                  •   Material balance equation
LiPb in                                Ldy  Gdx
                                       kL av S y  yi dz kG aV ct x xi dz
                                  •   Gas-phase mass-transfer 3    2 coefficient
                                                   G 0.32   G 
                                      H G  3.07 0.51           
                                                    L  G DG 
                                                              Cited from He-water system
                                  •   LiPb-phase mass-transfer coefficient
                                                      0.22        0.5
LiPb out             He in                  1  L    L 
                                      HL                  
                                                               Cited from He-water system
                                           430  L   L DL 
                                  •   Tritium concentration profile in tritium extraction
                                                  K L  z  KC L
                                           exp   C 
                                                   1               
                                        y       
                                                    G H 0, L  G
                                       yin        K L  h  KC L
                                             exp   C 
                                                   1               
                                                    G H 0, L  G

                              Example of calculation of tritium concentration
                              in a counter-current extraction tower (Flibe case)
                              S. Fukada et al., Fusion Science and Technology, 41 (2002) 1054.)

                                                 S. Fukada, Kyushu University group
         Ceramic Coating R&D for Pb-17Li
Properties of ceramic coating for Pb-17Li blanket
• Tritium permeation resistance
• Electrical resistance
• Corrosion resistance

Fabrication and properties of ceramic coatings
• Al2O3 coating fabricated by hot-dipping followed by
  oxidation (Tokyo)
• Y2O3 coating fabricated by plasma spray (Tokyo)
• Al2O3 and Y2O3 coating fabricated by plasma CVD (Tokyo)
  (Terai et al., Surf. Coat. Tech. 106 (1998), 18.)
• Er2O3 coating fabricated by Arc-source deposition (NIFS,
  Tokyo, JUPITER-II)
Al2O3 Coating Fabricated by Hot-Dipping
     Followed by Oxidation (Tokyo)

                   (Terai et al., SOFT-1994, p.1329)
                   (Terai, J. Nucl. Mater. 248 (1997), 153)
Phase Change of the Coating Fabricated by
   Hot-dipping Followed by Oxidation
Er2O3 coating as tritium permeation barrier
               (NIFS, Tokyo)
Selection of Er2O3 coating as tritium permeation barrier
    Thermodynamic stability, corrosion-resistance to liquid
    breeder, and high compatibility with structural materials
           → permeation barrier at multi-conditions
    Fabrication of Er2O3 coatings by several PVD methods

Observation on characteristics of coating,
    (1)Surface observation for cracks and holes (microscope)
    (2)impurity (XPS, EDS)
    (3)density (weight change + SEM)
    (4)crystallinity (XRD)
→ Selection of coating methods and conditions

Hydrogen permeation test
    (5)Coatings with different grain size and thickness
→ Evaluation of ability and mechanism for improvement on
   Er2O3 as a tritium permeation barrier.
                     Characteristics of coatings
                   RF sputtering        Reactive sputtering
                       many                  medium                few
  & Holes
 Impurity               low                    low                 low
  Density               low                  medium                high
                  medium to good                              Medium to good
Crystallinity     (depending on the          medium           (depending on
                  distance between                             temperature)
                target and substrate)

• The coating fabricated by arc-source method is considered to be
  sutable for tritium permeation barrier coatings.
→ Hydrogen permeation experiment for the coating fabricated by arc-
  source method.
  Hydrogen permeation rate coefficient (NIFS, Tokyo)
      • Permeation reduction factor to the vanadium substrate: 1/106~1/108
      • PRF to iron or stainless steel : 1/100~1/10,000 (comparable with
        Al2O3 coatings)
      • Permeation rate coefficient was affected by the thickness of coatings
        than crystallinity or grain size
                    10Pa~105Pa             Vanadium           Iron
        10                                 SUS304

             -9                            非加熱
                                           Room temp.         700℃
              1.2     1.3   1.4     1.5      1.6        1.7          1.8

                                  1000/T                                Double layered coating
          Activity in Kyoto University
                Institute of Advanced Energy, Kyoto University

         Kyoto University pursues advanced blanket concept based on
        LiPb – SiC – He combination
        to be opearated at 900 degree or above.
  Research objective includes,
    -to Establish a possible advanced blanket concept with supporting technology
    -to Demonstrate the attractiveness of fusion energy with safety and effectiveness
       i.e. high temperature efficient generation and hydrogen production,
            minimal waste generation and tritium release,
            technical feasibility, adoptability to attractive reactor designs.

Research Items
  Current researtch efforts are on the following tasks
    Conceptual design with neutronics and thermo-hydraulics, MHD
    LiPb-SiC-hydrogen system study: compatibility, solubility, permeability
    LiPb technology : Loop experiment, purity control, high temperature handling
    SiC component development : cooling panel, tubings, fittings and IHX
    Mockup development : heat transfer, -tritium recovery and control
SiC-LiPb Blanket Concept
        Outer blanket           •Module box temperature made of
      calculation model          the RAFS must keep under 500 ºC.
       1.RAFS module
         box (~500ºC)           •Li-Pb outlet temperature target
                                 900 ºC.
       2.SiC/SiC active
         cooling panel
                                •We propose the new model of
    Li-Pb Flow                   active cooling in Li-Pb blanket.
                                •This concept is equipped He
 3.High temp. outlet (~900ºC)
                                 coolant channels in SiC/SiC
                                 composite and provides more
                                 efficient isolation between the
                                 RAFS and high temperature Li-Pb.
                                •We evaluate the feasibility of high
                                 temperature blanket in this model.
         Activity in Kyoto University
              Institute of Advanced Energy, Kyoto University
LiPb loop
         operational for heat exchanger with SiC composite development
        Upgrading for LiPb-He dual coolant loop started in 2006.
        900 degree He secondary loop will be added in 2007.

  LiPb loop was installed and started operation
  Major parameters:
     LiPb inventory : 6 liter
     flow rate      : 0 – 5 liter /min
     temperature : 250 – 500 degree C
                      (~900 deg C at SiC section)
  MHD , heat exchange, compatibility, hydrogen
  permeation studied.

                                                        LiPb loop in Kyoto University

                                                                        15.12 mm
SiC cooling panel structure
  channel structure unit with NITE composite                         17.89 mm
developed for He-LiPb cooling panel.                          6 mm
                                                    NITE SiC cooling panel channel
At Osaka University, brush up of conceptual design reactor
KOYO-F and elemental experiments are continued with
other universities collaborately
                                Basic specifications
                                                 4 Modular reactors + 1
                                                 laser system
                                                 1.1 MJ/pulse, 32 beams,
                                  n laser
                                                 Cooled Yb:YAG ceramic
                                  Heating        0.1 MJ/pulse, 16Hz,
                                  laser          Cooled Yb:YAG ceramic
                                   Wall load at 200 200 MJ/pulse,
                                  Fusion yield MJ fusion yield 4 Hz
                                  Chamber         3m radius, 12m high at
                                  size           inner surface

                                             Pulse    Peak     Average
                                             load     load     load
                                  Neutro     1.4      50       5.6
 Fast ignition KOYO-F             ns         MJ/m2    PW/m2    MW/m2
                                             0.7      2        2.8
                                             MJ/m2    TW/m2    MW/m2
Features of KOYO-F to deal with high a heating
                                                      •   Vertically off-set
                                                          irradiation to simplify
                                                          the protection scheme
                                                          of ceiling

                                                      •   Cascade surface flow
                                                          with mixing channel
                                                          to enhance pumping
                                                          by cryogenic effect.

                                                      •   Tilted first panels to
                                                          make no stagnation
                                                          point of ablated vapor

                                                   Critical issues are:
                       Target is enlarged by 150
                                                   1) Protection of beam ports
           3) Tritium flow                         2) Aerosols and particles
           Elemental study at ILE and
      collaborations with other universities
•   At ILE, Osaka
     – Ablation by alpha particles
        was experimentally
        simulated with punch-out
        targets driven by back
        lighted laser.
•   At Kyushu University
     – With Dr Y. Kajimura, beam
        port protection
     – With Dr. S. Fukada, tritium
•   At Kyoto University
     – With T. Kunugi, stability of
        cascade flow
     – With S. Konishi, ablation,
        aerosols, LiPb loop
                       Hydrogen isotope behavior in SiC for
                          the insulator in Pb-Li blanket
                                                          Si-D C-D                                      Y. Oya and K. Okuno
                                                                                                        Shizuoka University

                                2.0                                   Ion fluence
  Desorption rate / 10 D2 m s

                                      Heating rate: 0.5 K s

                                                                           22   +  -2
                                                                       / 10 D m
                                1.5                                           0.50



                                       400       600      800      1000    1200
                                                                                        Implantation temperature dependence on D
                                                   Temperature / K                      retention in graphite, SiC and WC

     D2 TDS spectra for SiC at room temperature

In the initial stage, D was trapped by C and after the saturation of C-D, D was
trapped by Si.
D retention in SiC is reached more than 0.7 D/SiC at room temperature.
He implantation effects on hydrogen isotope trapping in SiC
                                                                         +                                                         1.5
                                                              Non-He imp.
 D2 desorption rate / a. u.

                                                                                                       He desorption rate / a.u.
                                                                    +                                                                      Pre-He imp.
                              3                               Pre-He imp.                                                                         +
                                                                      +                                                                    Post-He imp.
                                                              Post-He imp.


                              0                                                                                                    0.0
                              300    500     700    900      1100        1300                                                        300   500        700   900   1100   1300
                                           Temperature / K                                                                                       Temperature / K

                              1.0                                         4
                                                          D/Si                                       Only D bound to Si was influenced
                                                                              He retention / a. u.
                              0.8                         D/C             3
                                                                                                     by He+ implantation.
          D/SiC, Si, C

                                                          He retention
                              0.6                                                                    By He+ implantation, the damaged
                              0.4                                                                    structure would be introduced. In
                                                                          1                          addition,   He     retention   was
                                                                                                     observed, although D retention was
                                      D+         Pre +      Post +
                                                                   0                                 decreased.
                                 Non-He imp. Pre-He imp. Post-He imp.
          TITAN Task 1-2:
Tritium Behavior in Blanket Systems

     T. Terai, A. Suzuki, H. Nishimura (U. Tokyo)
            S. Konishi, T. Kamei (Kyoto U.)
 S. Fukada, K. Munakata, K. Katayama (Kyushu U.)
 T. Nagasaka, M. Kondo, T. Uda, A. Sagara (NIFS)
         T. Norimatsu, K. Homma (Osaka U.)
               T. Sugiyama (Nagoya U.)

        P. Sharpe, P. Calderoni, D. Petti (INL)
                 D-.K. Sze (UCSD)

                     and others
Key technical items for tritium in liquid blanket systems
 •   Solubility in Pb-Li
     - typical measurements performed at relatively high hydrogenic partial pressure
       (~101-104 Pa) are extrapolated to much lower partial pressures required for
       tritium inventory control
     - deviance from Sievert’s Law is possible (based on other LM results, e.g. Li)
     - measurements at extremely low concentrations require tritium

 •   Recovery methods from Pb-Li (and other liquid breeders) and He
     - inadequate mass transport across liquid-vapor interface for vacuum
       disengagement or window permeators in PbLi
     - oxidation or cryogenic systems for He, with structural and power implications
     - ingenious techniques for high recovery efficiencies are needed

 •   Transport barriers resistant to thermal cycling and irradiation
     - minimum required PRF ~ 100, needs robustness or self-healing attributes
     - success (or lack thereof) greatly influences direction of blanket system design

 •   Permeation behavior at very low partial pressures over metals
     - linear vs. Sievert’s behavior? transport related to dissociation/recombination
       rates becomes non-equilibrium?
     - influence of surface characteristics and treatment
Proposed Research Project Areas for TITAN Task 1-2

 Selected to provide the basis for the Tritium Behavior in Liquid
 Blanket Systems of interest to US and Japan
 Solubility of T in Pb-Li at Blanket Conditions
     - Low pressure region of hydrogen isotopes using tritium
     - Confirmation of Sieverts’ Low, Phase diagram of Pb-Li and T system

 Concentration Effects of T Permeation in Structural Materials and
  TPB Coating
     - Wide T pressure range covering several kinds of liquid breeders
     - Performance test on SM as well as TPB coating (to be developed in Japan)

 Tritium Extraction from Pb-Li and Other Liquid Breeders at Blanket
     - Mass transfer kinetics
     - Permeation window, gas engager, etc.
     - Performance test on a loop which is constructed inside or outside the budget

 Modeling and System Design for Tritium Behavior at Blanket

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