Coordinating Meeting on R

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Overview of Japanese PbLi-T Research
Activities and Related Topics
Takayuki Terai tera_at_n.t.u-tokyo.ac.jp University
of Tokyo
Coordinating Meeting on RD forTritium and
Safety Issues in Lead-Lithium Breeders (PbLi-T
2007)
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Japanese PbLi-T Research Activitiesand 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)

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Tritium Release Behavior from Liquid breeders
under a Blanket -Simulated Condition (under
Neutron Irradiation at High Temperature)
(Tokyo)
Pb-17Li, LiF-BeF2(Flibe), Sn-20Li 673-973
K Tritium chemical species (HT, HTO, TF,
etc.) Tritium diffusivity Tritium release
rate Tritium permeation through piping materials
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Diffusion Coefficient of Tritium in Liquid Pb-17Li
Under the condition of He-H2 (pH2 gt 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.)
(Tokyo)
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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 gt 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.
(Terai et al., Fus. Engng. and Des. 17 (1991),
237)
(Tokyo)
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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)
(Tokyo)
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Experiments of recovery of hydrogen isotopes from
Pb-17Li-Measurement of diffusivity, solubility
and isotopic exchange rate constant-
Li-Pb
Fe
Experimental apparatus for LiPb-H2(D2) system
Comparison between experiment and calculation
S. Fukada, Kyushu University group
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Dependences of DH and SH on temperature for
Pb-17Li-H system and comparison with previous
researches
Hydrogen solubility in Li0.17Pb0.83
Hydrogen diffusivity of Li0.17Pb0.83
S. Fukada, Kyushu University group
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Li activity of LiXPb1-X-H2 system eutectic alloy
Pb
Pb
Li
H-
Pb
Li
Pb
H-

• When xLigt0.5, 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 xLilt0.5, 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
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Design of He-LiPb counter-current extraction
towerfor tritium recovery

• Material balance equation
• Gas-phase mass-transfer coefficient
• LiPb-phase mass-transfer coefficient
• Tritium concentration profile in tritium
  extraction tower

Cited from He-water system
Cited from He-water system
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
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Ceramic Coating RD 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)

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Al2O3 Coating Fabricated by Hot-Dipping Followed
by Oxidation (Tokyo)
(Terai et al., SOFT-1994, p.1329) (Terai, J.
Nucl. Mater. 248 (1997), 153)
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Phase Change of the Coating Fabricated by
Hot-dipping Followed by Oxidation
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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.
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Characteristics of coatings
RF sputtering Reactive sputtering Arc-source deposition
Cracks Holes many medium few
Impurity low low low
Density low medium high
Crystallinity medium to good medium Medium to good
Crystallinity (depending on the distance between target and substrate) medium (depending on temperature)

• 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.

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Hydrogen permeation rate coefficient (NIFS, Tokyo)

• Permeation reduction factor to the vanadium
  substrate 1/1061/108
• PRF to iron or stainless steel 1/1001/10,000
  (comparable with Al2O3 coatings)
• Permeation rate coefficient was affected by the
  thickness of coatings than crystallinity or grain
  size

? Double layered coating
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Activity in Kyoto University
Objective 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
- 9 -
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SiC-LiPb Blanket Concept
Outer blanket calculation model

• Module box temperature made of the RAFS must keep
  under 500 ºC.
• Li-Pb outlet temperature target 900 ºC.
• We propose the new model of active cooling in
  Li-Pb blanket.
• This concept is equipped He 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.

1.RAFS module box (500ºC)
2.SiC/SiC active cooling panel
3.High temp. outlet (900ºC)
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Activity in 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
SiC cooling panel structure channel structure
unit with NITE composite developed for He-LiPb
cooling panel.
NITE SiC cooling panel channel
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At Osaka University, brush up of conceptual
design reactor KOYO-F and elemental experiments
are continued with other universities
collaborately
Basic specifications
Electric output 1283MW
System 4 Modular reactors 1 laser system
Compression laser 1.1 MJ/pulse, 32 beams, 16HzCooled YbYAG ceramic
Heating laser 0.1 MJ/pulse, 16Hz, Cooled YbYAG ceramic
Fusion yield 200 MJ/pulse, 4 Hz
Chamber size 3m radius, 12m high at inner surface
Wall load at 200 MJ fusion yield
Pulse load Peak load Average load
Neutrons 1.4 MJ/m2 50 PW/m2 5.6 MW/m2
Alpha 0.7 MJ/m2 2 TW/m2 2.8 MW/m2
Fast ignition KOYO-F
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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 channelto
  enhance pumping by cryogenic effect.
• Tilted first panels to make no stagnation point
  of ablated vapor

Critical issues are
Target is enlarged by 150
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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 flow
• At Kyoto University
• With T. Kunugi, stability of cascade flow
• With S. Konishi, ablation, aerosols, LiPb loop

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Hydrogen isotope behavior in SiC for the
insulator in Pb-Li blanket
Si-D
C-D
Y. Oya and K. Okuno Shizuoka University
Implantation temperature dependence on D
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.
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He implantation effects on hydrogen isotope
trapping in SiC
Only D bound to Si was influenced by He
implantation. By He implantation, the damaged
structure would be introduced. In addition, He
retention was observed, although D retention was
decreased.
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TITAN Task 1-2 Tritium Behavior in Blanket
Systems

• Participants
• 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

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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 Sieverts 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 flows
• - 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. Sieverts behavior? transport
  related to dissociation/recombination rates
  becomes non-equilibrium?- influence of surface
  characteristics and treatment

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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 Conditions
• - 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 Conditions