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