Upload
megan
View
35
Download
0
Tags:
Embed Size (px)
DESCRIPTION
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 - PowerPoint PPT Presentation
Citation preview
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
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/
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
2007 - 2011http://tritium.nifs.ac.jp/
A01 Experimental studies on in-vessel tritium inventory in complicated environment of fusion reactors.
Yoshio Ueda (Prof. Graduate School of Engineering, Osaka University)
A02 Theory and code development for evaluation of tritium retention and exhaust in fusion reactor.
Kaoru Ohya(Prof. Institute of Technology and Science, The University of Tokushima)
B01 Study of clarifying tritium transfer in materials of fusion reactor blanket and developing new processes for tritium recovery from fusion reactor system.
Satoshi Fukada(Prof. Interdisciplinary Graduate School of Engineering Sciences, Kyushu University)
B02 The behavior of tritium in blanket with solid and liquid breeding materials; prevention of T leakage/permeation
Takayuki Terai(Prof. Graduate School of Engineering, University of Tokyo)
C01 R&D on effect of chemical behaviors of high level tritium in organic compounds and water on tritium confinement.
Toshihiko Yamanishi (Japan Atomic Energy Agency)
C02 Tritium permeation, contamination and decontamination.
Yuji Hatano(Prof. Hydrogen Isotope Research Center, University of Toyama)
Research groups and leaders
Budget (2007-2011)
19年度
191,642k\
総額
854,149k\
B group230,800k\
27%
2007 year
191,642k\ Total
754,149k\
B group65,700k\
34%
C group60,750k\
32%
Organizing6,600k\3%
A Group58,692k\
31% C Group249,900k\
29%
Open for application40,000k\5%
Organizing36,000k\4%
A Group237,449k\
28%
Total of 7 M$ for 5 years and 6 research gropes
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
W
Ta
Ti
Cu
Surface Contamination by gloves in safety boxMetal plates exposed to D plasma in TPL
and handled in a T handling glove box
Traces of glove fingers
Possible contamination by permeation
M. R. Louthan et al., Corrosion Science (1975)
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
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
The effects of such non uniform distribution on kinetics of hydrogen uptake and reemission are not well understood.
Non uniform tritium distribution on F82H surface
Barrier effect of surface oxide on hydrogen permeation
H2 + 1/nMmOn = m/nM + H2O – ΔGf
ΔGf = - RT ln(P(H2O)/P(H2))
Significant effect of surface oxidation on H diffusion
T(H) behavior at near surface layersTritium luminog
raphy
Tritium autoradiograph
y
Tritium evolution method
Tritium tracer technique is based on detection of -electrons emitted from T diluted in hydrogen.
Local tritium distribution (profile) at near surface layers with spatial resolution of m
Reduction of AgS to Ag by -electron energy (Spatial resolution of ~1 m)
Tritium evolution in a liquid scintillation cocktail
Conversion of -electron energy to stimulated luminescence (Spatial resolution of 50 m )
m
T accumulation in blisters on Al surface
Non-uniform T distribution
RAF/M(F82H) Cr 8 wt%, W 2 wt%, Fe valance
Tritium loading
T evolution measurement
By using Liquid Scintillation Counter
Electrochemical chargingin 0.1 N NaOH solutionT conc.: T/H=10-6
Current density: 1 A m-2
Temp.: RTChraging Time: 56 h
Immersed in the LSC cocktailContinuously measure for 40 h
LSC cocktail (Perkin Elmer, Ultima Gold)
Tritiated sample
Pt electrodes
Sample
0.1 NaOH solutionIncluding tritium
4 mm
0
0.2
0.4
0.6
0.8
1
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
0 20 40 60 80 100
Inte
grat
ed e
volu
tion
tri
tiu
m in
ten
sity
, Q /
-
Time / 106 s
Time / h
Calculated T ecolution curve
Initial condition: Fig. 2(b)D=5x10-14 m2s-1
T evolved-out from sample
0
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 1
Nor
mal
ized
tri
tiu
m c
once
ntr
atio
n, C
x / L
Calculated profile
D=5x10-14 m2s-1
Diffusing-in profile from both surface
Surface distributionTritium Profiling T evolution by scintillation method
A B
A B
Heterogeneous surface H(T) profile does not influence both diffuse-in and evolution-out processes, giving the same apparent diffusion coefficients.
Pyrex glass tube(Geissler tube)
DC glow discharge
H2Pressure: 40 PaWith T/H=10-6
Applied Voltage: 350 VTime: 30 min
Electrode(SS316)
Sample(4 x 1 x 10 mm3)
1 mm
4 mm
Tritium loading surface
Tritium loading by Glow discharge methodfor profiling of Tritium diffusing in
Liq. N2
0
100
200
300
400
500
0 5 10 15 20 25 30
Act
ivit
y /
DP
M
Time / h
0 h (15min)
1 h
3 h 10 h
Liquid scintillation cocktail (Perkin Elmer, Ultima Gold)
Tritiated sample
Tritium evolution from F82H anddiffusing profiling at 0h, 1h, 3h,10h after loading
Tritium diffusion profile determined by IP for the cross-section of F82H steel
1 hour after H(T) loading by DC glow discharge method
0
5
10
15
20
25
30
-2 -1 0 1 2
Surface(Tritium loading side)
Tri
tiu
m a
cti
vit
y,
PS
L /
mm
2
Depth, x / mm
He gas F82H steel
0
0.5
1
1.5
2
2.5
0 0.5 1 1.5 2
Tri
tiu
m a
cti
vit
y,
PS
L /
mm
2
Depth / mm
x
y Sample
T loading by DC glow
0
10
20
30
40
50
0 0.2 0.4 0.6 0.8 1
1h3h10h
0h(15min)
Tri
tiu
m a
cti
vit
y,
PS
L
Depth / mm
0
10
20
30
40
50
0 2 4 6 8 10
Tri
tiu
m a
cti
vit
y,
PS
L
Time / h
Surface tritium retention
0
0.5
1
1.5
2
2.5
3
0 0.2 0.4 0.6 0.8 1
1h3h10h
0h(15min)
Tri
tiu
m a
cti
vit
y,
PS
L
Depth / mm
Tritium profiles in the bulk
T accumulated at surface are released but the release is completely separated from that in the bulk.
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 release from surface and bulk diffusion are separated
10-14
10-13
10-12
10-11
10-10
10-9
10-8
1.5 2 2.5 3 3.5 4Ap
par
ent
dif
fusi
on
co
effi
cien
t, D
, m
2 s
-1
1000 T-1 / K-1
F82H (Serra et al., Permeation method)
Temperature / K323 298473573
Previous study (T. Otsuka, Tritium evolution method)
353
Present study
H diffusion coefficient in F82H steelComparison
H Chemical potential
Surface Hydrogen
Trapped Hydrogen
H dissolubedin lattice
Permeation
Steady state H permeation with trapping
Permeation rate
is not influenced by trapping dxxD
Small gradient in concentration
RTEEC
Ci
i
tst
s /exp
Con
cent
ratio
nC
hem
ical
po
ten
tial
Tritium (Hydrogen) accumulated on the surface does not seem to influe
nce hydrogen release from bulk at near RT. This support easy isotopi
c exchange at the surface.
Probably surface T is strongly trapped or bounded on the surface or sur
face impurities (most likely oxides) and separated from hydrogen mo
ving interstitialy.
Summary
With increasing the temperature, the surface hydrogen becomes to int
eract with the interstitial ones and reduce the apparent diffusion coef
ficients, 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!
Tritium (Hydrogen) does accumulate on F82H surface very non-
uniformly near RT
Why new research projects for tritium in fusion?
• 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
Limited resource requires safety T breeding system compatible with power production
Production of hazardous inorganic tritium
Contamination by permeation and leakage Multi step contamination
ITER at France and a Test reactor in Japan
require large numbers of tritium experts
Reacto
r
(Reg
ulatio
n
)
(Ph
ysical &
Ch
emical
)
Safety C
on
finem
ent