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9 th International workshop on H isotopes in FRM, Salamanca, Spain, 2008 June 2-3

9 th International workshop on H isotopes in FRM, Salamanca, Spain, 2008 June 2-3. Role of surface hydrogen on absorption, solution and diffusion in stainless steels (Title changed). T. Otsuka and T. Tanabe, Kyushu University. Surface segregation of tritium - Contamination and accountancy

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9 th International workshop on H isotopes in FRM, Salamanca, Spain, 2008 June 2-3

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  1. 9th International workshop on H isotopes in FRM, Salamanca, Spain, 2008 June 2-3 Role of surface hydrogen on absorption, solution and diffusion in stainless steels (Title changed) T. Otsuka and T. Tanabe, Kyushu University Surface segregation of tritium - Contamination and accountancy How much retained How easy/difficult to remove How influence on tritium take-up or reemission - Interactions with surface contaminants or segregated elements

  2. 9th International workshop on H isotopes in FRM, Salamanca, Spain, 2008 June 2-3 Just a small news! In Japan, a new scientific research project related to tritium has started; Grand in Aid for Scientific Research, MEXT for Priority Area, for 5 years from 2007 to 2011 “Tritium Science and Engineering for Fusion” http://tritium.nifs.ac.jp/

  3. http://tritium.nifs.ac.jp/ 2007 - 2011 DT fusion reactor (Ignition and continuous burning) D + T = 3He (3.7MeV) + n (14MeV) To establish reliable and safe tritium fuel cycles and safe tritium confinement to build economic and safety fusion reactorEncouraging yang scientist and students

  4. Research groups and leaders

  5. Budget (2007-2011) Total of 7 M$ for 5 years and 6 research gropes Open for application 40,000k\ 5% Organizing 6,600k\ 3% Organizing 36,000k\ 4% A Group 237,449k\ 28% A Group 58,692k\ 31% C group 60,750k\ 32% 総額 854,149k\ １９年度 191,642k\ 2007 year 191,642k\ C Group 249,900k\ 29% Total 754,149k\ B group 65,700k\ 34% B group 230,800k\ 27%

  6. 9th International workshop on H isotopes in FRM, Salamanca, Spain, 2008 June 2-3 Role of surface hydrogen on absorption, solution and diffusion in stainless steels (Title changed) T. Otsuka and T. Tanabe, Kyushu University Surface segregation of tritium - Contamination, Inventory and Accountancy How much retained How easy/difficult to remove How influence on tritium up-take or release How similar to bulk traping - Interactions with surface contaminants or segregated elements

  7. Cu Ta W Ti Surface Contamination by gloves in safety box Metal plates exposed to D plasma in TPL and handled in a T handling glove box Traces of glove fingers Possible contamination by permeation

  8. Very old work clearly indicating different surface treatments results in different tritium uptake Charging condition: 20% tritium gas, under 60 atm, after 6 years storage M. R. Louthan et al., Corrosion Science (1975)

  9. Our knowledge - Significant amount of Hydrogen is always absorbed on surface. - Surface oxides work as barrier for hydrogen penetration (or absorption and permeation) into bulk at intermediate temperatures . - Surface oxides trap hydrogen with chemical forms like M-OH Non uniform tritium distribution on F82H surface The effects of such non uniform distribution on kinetics of hydrogen uptake and reemission are not well understood.

  10. Barrier effect of surface oxide on hydrogen permeation

  11. Significant effect of surface oxidation on H diffusion H2 + 1/nMmOn = m/nM　＋　H2O– ΔGf ΔGｆ= － RT ln(P(H2O)/P(H2))

  12. Tritium tracer technique is based on detection of b-electrons emitted from T diluted in hydrogen. Local tritium distribution (profile) at near surface layers with spatial resolution of mm Reduction of AgS to Ag by b-electron energy (Spatial resolution of ~1 mm) Tritium autoradiography T accumulation in blisters on Al surface T(H) behavior at near surface layers Tritium evolution method Tritium luminography Non-uniform T distribution Tritium evolution in a liquid scintillation cocktail Conversion of b-electron energy to stimulated luminescence (Spatial resolution of 50 mm ) 5mm

  13. Tritium loading RAF/M(F82H) Cr 8 wt%, W 2 wt%, Fe valance Sample Electrochemical charging in 0.1 N NaOH solution T conc.: T/H=10-6 Current density: 1 A m-2 Temp.: RT Chraging Time: 56 h Pt electrodes 0.1 NaOH solution Including tritium T evolution measurement By using Liquid Scintillation Counter Immersed in the LSC cocktail Continuously measure for 40 h Tritiated sample LSC cocktail (Perkin Elmer, Ultima Gold)

  14. Heterogeneous surface H(T) profile does not influence both diffuse-in and evolution-out processes, giving the same apparent diffusion coefficients. T evolution by scintillation method Tritium Profiling Surface distribution T evolved-out from sample B A 4 mm Diffusing-in profile from both surface B A

  15. 1 mm 4 mm Tritium loading surface Tritium loading by Glow discharge methodfor profiling of Tritium diffusing in Pyrex glass tube (Geissler tube) Sample (4 x 1 x 10 mm3) DC glow discharge H2Pressure: 40 Pa With T/H=10-6 Applied Voltage: 350 V Time: 30 min Electrode(SS316) Liq. N2

  16. Tritium evolution from F82H and diffusing profiling at 0h, 1h, 3h,10h after loading 3 h 10 h 1 h 0 h (15min) Tritiated sample Liquid scintillation cocktail (Perkin Elmer, Ultima Gold)

  17. Tritium diffusion profile determined by IP for the cross-section of F82H steel 1 hour after H(T) loading by DC glow discharge method y Sample T loading by DC glow x

  18. T release from surface and bulk diffusion are separated T release behavior is well interpreted by simple diffusion model. Surface does not seem to work as barrier for the release of bulk hydrogen. T accumulated at surface are released but the release is completely separated from that in the bulk. Surface tritium retention Tritium profiles in the bulk

  19. H diffusion coefficient in F82H steel Comparison

  20. Steady state H permeation with trapping H Chemical potential F Permeation rate is not influenced by trapping Concentration Chemical potential Small gradient in concentration Permeation H dissolubed in lattice Trapped Hydrogen Surface Hydrogen

  21. Summary Tritium (Hydrogen) does accumulate on F82H surface very non-uniformly near RT Tritium (Hydrogen) accumulated on the surface does not seem to influence hydrogen release from bulk at near RT. This support easy isotopic exchange at the surface. Probably surface T is strongly trapped or bounded on the surface or surface impurities (most likely oxides) and separated from hydrogen moving interstitialy. With increasing the temperature, the surface hydrogen becomes to interact with the interstitial ones and reduce the apparent diffusion coefficients, determined from the absorption or desorption transient, but not much at the steady state. The barrier effect of surface oxide layers would be separated from this . Needs more experiments!

  22. Safety Confinement （Regulation） （Physical & Chemical ） Production of hazardous inorganic tritium Why new research projects for tritium in fusion? Limited resource requires safety T breeding system compatible with power production • Recycling of fugue amount of T • Safety confinement and possible contamination • Difficulty of extrapolation of limited experience of T • handling to fusion system • Poor understanding of isotope effect Reactor Contamination by permeation and leakage Multi step contamination ITER at France and aTest reactor in Japan require large numbers of tritium experts

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