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Page 1: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

"Jožef Stefan" Institute,Dept. of Surface Engineering and Optoelectronics

Slovenian Fusion Association (SFA). MHEST

Deuterium retention in

ITER -grade: stainless steel, Be and W

Vincenc Nemanič, Bojan Zajec, Marko Žumer

Ljubljana, Slovenia

Cadarache, 15th June 2009

Page 2: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

2) Experimental methods:

• general description • selection and adaptation for our work.

3) Results on ITER - grade stainless steel, Be and W

1) Motivation for the work

Outline of the talk:

Page 3: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Motivation: tritium retention prediction

Basic concepts to predict tritium retention data for metals

applied in future fusion reactors:

1) Deuterium data obtained in experiments simulating and

approaching conditions in ITER post mortem analysis

2) Refined classical experiments for more accurate

interaction data (equilibrium & kinetics) of gaseous

hydrogen (H/D) with ITER relevant metals = our

approach

An important fact: Most of solubility, diffusivity and

permeability data obtained decades ago.

Page 4: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

EFDA Technology Work Programme:

TW6-TPP-RETMET

The purpose of our study was to determine deuterium

retention in 24 hour-expositions in D2 at p = 0.1 mbar

and below

• ITER grade AISI316 at T = 100, 250 and 400 °C• ITER-grade Be T = 100 °C and 250 °C• ITER-grade W T = 250, 400 and 1000 °C

Sample metals provided by

EFDA Close Support Unit - Garching

Page 5: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Experimental: Basic interaction of hydrogen (H/D/T) with

bulk material is expressed by diffusivity and solubility,

experimentally determined by:

1) infusion/outgassing technique

or

2) membrane technique

A careful selection of all experimental details is needed to

get reliable results. W. G. Perkins, J. Vac. Sci. Technol. 10 (1973)

543

Page 6: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

The principle of infusion/outgassing technique:

equilibrium between gas phase (H/D/T) and metal sample

achieved at specified conditions (high p, high T) gas

pumped off transient to a new equilibrium observed

(low p).

* * * *

The principle of permeation technique:

Transient flow observed from t = 0 when pupstream is set

until steady downstream flow is achieved

Page 7: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Hydrogen detection mode applied in any of both techniques:

1) Dynamic method, ion current of characteristic mass

number applying mass spectrometer is recorded at

constant pumping speed

or

2) Static method (gas accumulation), pressure recorded by

non-ionizing gauges in valved-off system followed by mass

spectrometry, instrument located in a separate UHV system

Page 8: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Both techniques types require low hydrogen background since

it influences the sensitivity (and discrimination limit when

deuterium is applied).

The most troublesome is outgassing of the sample holder and

its potential simultaneous interaction with hydrogen (H/D).

Isotope exchange interaction difficult to distinguish since it

runs: in the sample and in the sample holder.

Best option for H.metal interaction is applying both

techniques ifusion/ourgassing and permeation, since they

give complementary data.

Page 9: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Materials most suitable for sample holder:

Kovar glass: almost ideal up to 450 °C, no detectable

interaction with H/D. (used in our lab for ITER-grade

stainless steel and Be)

Silica: wide range of T, thermal shock resistance, used for

RF heating, but exhibits anomally, noticed in:

A.Farkas, L.Farkas, Trans.Farad. Soc. 31, 821 (1935)

and quantified inR.W.Lee, R.C.Frank, D.E.Swets, J.Chem.Phys., 36, 4 (1962).

A minor part of hydrogen is “diffusive”, isotope exchange

in silica or quartz using D2 unpredictable, quantified work

with metal samples troublesome or impossible.

Page 10: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Materials most suitable for sample holder:

Pure alumina: at present, the only candidate for W sample

holder from 500 °C to 1000 °C.

Several exposures of empty thimble to deuterium showed

some isotope exchange, too. Resolving the difference

when the sample in hot zone or cool zone, still

troublesome.

Page 11: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Experimental setup

(3 UHV chambers) for

infusion/outgassing or

for permeation method

using H2 or D2

Page 12: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Exposure section with calibrated cell, CM and SRG gauges

Page 13: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Exposure section – thimbles: glass or alumina

Page 14: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

The ultimate sensitivity determined by the background

outgassing rate of H2 and small volume (~1.3 L).

Inner sources of H2 are:

• UHV system walls (at R.T.)• metal sample (elevated T)• sample holder i.e. extension tube (elevated T)

•QMS (ionization cell itself)

The achieved detection limit ~ 2109 molecules/(cm2s)

Various schedules used to convert QMS signals of H2, HD

and D2 into the absolute units by calibration H2/D2 mixtures.

Equal procedure steps applied for all investigated metals

Page 15: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Results:

Stainless steel ITER grade

(AISI 316, Co (<0.05 wt. %); Nb (<0.01 wt. %)

25 mm O.D tube,

50 mm high

A = 74.6 cm2

V = 4.66 cm3

wet cleaning, drying

1) sample preparation

2) cut from a massive 45 kg block 62340 cm3

Page 16: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Experimental steps applied for stainless steel

(similar for Be and W (glass replaced by alumina))

"blank run" steps (sample at R.T.):

• UHV system after bake-out: dp/dt= 910-9 mbar/s

• UHV system + hot tubular extension

• exposure (0.1 mbar D2, 400°C, 24 h) no observable

isotope exchange detected

• sample in a tubular extension moved into the oven and

heated to 400°C for 8 days outgassing rate (H2) below

dp/dt = 910-8 mbar/s (i.e. 9.2×1010 molec. H2/(cm2s)),

registered C0 = 1.76 1019 /cm3

Page 17: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Pressure vs. time curve composed from several cycles,

the importance of low outgassing is evident.

0 5000 10000 15000 20000 25000 300000.0

0.2

0.4

0.6

0.8

1.0

C

t / s

measuredDLM RLM calc exponential

The observed kinetics is governed by the RLM rather

than by the DLM

0 20 40 60 80 100 120 140 160 180 200109

1010

1011

1012

1013

1014

RLM calculatedmeasured

q / m

olec

. H2 /

(s c

m2)

t / h

Devation from the RLM noticed after 20 h when

hydrogen from strogly bound sites became prevalent

Page 18: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

p t N/A C mbar h atom D/cm2 at D/cm3 1 0.1 24 1.8×1016 2.9×1017

2 0.1 24 2.6×1016 4.2×1017

3 0.01 24 1.9×1015 3.0×1016

4 0.01 24 1.9×1015 3.1×1016

Deuterium retention in ITER-grade stainless steel

during 24 h exposure at 400 °C

No detectable level of HDO was formed.

Page 19: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Deuterium retention in ITER-grade stainless steel

during 24 h exposure at 250 °C

p t N/A C mbar h atom D/cm2 at D/cm3 1 0.01 24 6.2×1014 1.0×1016 2 0.01 24 5.5×1014 8.9×1015 3 0.1 24 4.3×1015 7.0×1016

More details: V Nemanič, M Žumer, B Zajec, Nucl. Fus., 48, 11,

115009 (2008)

Page 20: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Beryllium Brush Wellman (S-65C VHP, Ti film on one side)

tile size: 2.42.00.4 cm3

A = 26.24 cm2

V = 3.84 cm3

Ti film removal,

wet grinding,

cleaning, SEM,

EDXS, XPS

Page 21: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

X-ray photoelectron analysis -XPS• XPS: very surface sensitive technique

• XPS depth profiling (by Ar ion sputtering) => in-depth distribution of elements

Be covered by Be-oxide BeO film thickness ~ (3 ± 1) nm

Page 22: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Beryllium – hydrogen (H,D,T) interaction

• published data on diffusivity and solubility very

scattered and almost useless for prediction of results

(A.A. Pisarev, Fusion Techn., 28, (1995) 1262)

• no data about hydrogen amount in our sample available

• a few reports on the same Be quality found as a rough

guidance for scheduled measurements

Page 23: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Be "Sample 1" investigated for hundreds of hours by the

same procedure as well proved on Stainless steel

• The amount of hydrogen extracted at 250°C in 72 h

was low, C ~ 21016 H/cm3.

• No clear evidence of interaction with D2 at 250°C in 24

h and 0.1 mbar

• Temperature increased to 400 °C for 420 hours

resulting in C ~ 7.31017/cm3 (6.5 appm) of hydrogen

• Kinetics perturbed presumably by traces of Ti film

deuterium retention data could be innacurate

• Further precautions introduced for "Sample 2"

Page 24: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Some results taken on Be "Sample 2" at 400°C for 570 h

1) The amount of hydrogen extracted C ~ 5.51017 H/cm3 (~

4.9 appm) i.e. ~ 81016 H/cm2

2) Recombination limited kinetics – 2 types of sites present

a minor part ~1.11017 H/cm3 released in the first 20 h (fast)

could be analog to “diffusive” H in silica?

the major part ~4.41017 H/cm3 released 550 h (slow) could be

analog to slowly releasing H in silica at high T

3) retention reconstructed from QMS analysis

Page 25: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

24 h averaged H2, (D2,HD) flux

0.E+00

1.E+10

2.E+10

3.E+10

4.E+10

5.E+10

6.E+10

0 100 200 300 400 500 600

t / h

H2(

D2,

HD

)/cm

2 s

extraction

D2 exposure

24h, 0.01

mbar

48h, 0.05

mbar

their ratio determined by QMS at the end of cycle

Page 26: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

p t N/A C mbar D2 h atom D/cm2 atom D/cm3 1 0.01 24 2.7×1015 1.8×1016 2 0.01 24 2.5×1015 1.7×1016 3 0.05 48 1.7×1016 1.2×1017 4 0.05 48 1.3×1016 8.7×1016

The amount of retained deuterium at specified exposures

What could be the amount of H(D) still contained

in the sample that makes isotope exchange possible?

Page 27: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

9.0E+179.5E+171.0E+181.1E+181.1E+181.2E+181.2E+181.3E+181.3E+181.4E+181.4E+18

0 100 200 300 400 500 600

t / h

del

ta C

/ (

H/c

m3)

2.E-27

3.E-27

4.E-27

5.E-27

6.E-27

7.E-27

8.E-27

9.E-27

1.E-26

KL /

cm

4 /s

C estim

KL

A slow decreasing in H2 (HD, D2) kinetics and intense isotope

exchange could be only explained when C in 560 h represents a

minor part (35%?) of all H(D) assuming j = KLC2.

determined

C ~ 5.51017 H/cm3

Page 28: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Tungsten Plansee

rod size:

O.D.= 2.5 cm

h = 20 cm

machined to

a tube:

I.D. 2.2cm

h = 5 cm

V = 5.31 cm3,

A = 76.0 cm2

Page 29: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Initial experiments in silica using RF heating gave

unreliable results due to:

• simultaneous outgassing of hydrogen and

• isotope exchange during deuterium exposure,

manifested in high HD ratio

• HD could not be attributed to W only

Page 30: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Hydrogen solubility from 400 °C to 1100 °C calculated from trusted (?) data.

Alumina data: Serra, J. Am.Ceram. Soc., 88 (2005) 15-18

Tungsten data: Frauenfelder, JVST, 6 (1969) 388-397

Silica data: RW Lee, RC Frank, DE Swets, J Chem.Phys., 36 (1962) 1062-1071 (diffusive H)

0.0007 0.0008 0.0009 0.0010 0.0011 0.0012 0.0013 0.0014 0.0015

1013

1014

1015

1016

1017

C /

H/c

m3

1/T / 1/K

alumina W silica

800°C

Page 31: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

0.0007 0.0008 0.0009 0.0010 0.0011 0.0012 0.0013 0.0014 0.00151E-11

1E-10

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

D /

cm2 /s

1/T / 1/K

alumina W silica

Hydrogen diffusivity from 400 °C to 1100 °C calculated

from trusted reported data.

800°C

Page 32: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

For ~ 2 mm thick materials, 24 h at 800 °C means:

Fo = 0.04 for alumina – will not come to equilibrium

Fo = 9.5 for silica

Fo = 130 for tungsten

In 48 h at 800 °C, alumina released dN/dA = 6.71015 H2/cm2

leading to dN/dt 1.31010 H2/(s cm2), low

W sample inserted intense outgasing

in 45 h C = 1.051018 H/cm3.

Residual outgassing at the end: H2 80%, CO 20%

deuterium exposures

Page 33: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Deuterium retention in ITER-grade tungsten

during 24 h exposure at 800 °C in alumina

1 2 3 4 5 6 7 8 9

p m/e m/e m/e m/e dN/dA C dN/dA

mbar 2 3 4 28 (CO) 1015D/cm2 1016D/cm3 1014D/cm2 1 0.0110 0.26 0.49 0.25 <0.01 3.0 4.3 3.8 2 0.0095 0.20 0.48 0.33 <0.01 2.9 4.2 3.6 3 0.0094 0.14 0.44 0.42 <0.01 3.3 4.7 3.9 4* 0.0102 0.64 0.32 0.05 <0.01 1.1* 1.6* 2.2 5 0.0098 0.45 0.44 0.12 0.26 4.1 5.9 4.2

Table 3: Retention of deuterium in tungsten at p = 0.01 mbar and T = 800 °C in 24 hours. The amount is reconstructed from the total pressure change and gas composition at the end of exposure. The number in the first column is exposure number. Exposure No.4 with * was done in hydrogen, but the released deuterium comes from the sample and the thimble loaded previously. Retention of deuterium is expressed as number of atoms per unit area in column 7 and as number of atoms per unit volume in column 8. The amount of deuterium released in the first 24 h after exposure is given in column 9.

Page 34: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Conclusions

An UHV system with the ultimate sensitivity of detecting ~

2109 molecules/(cm2s) from (into) the sample (A~30 cm2)

was built to measure deuterium retention during the low

pressure isothermal exposure of ITER grade stainless steel,

beryllium and tungsten.

High amount of H2 extracted in long term extractions from all

three metals prior exposures were feasible.

Page 35: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

The setup is prepared now also for:

• complementary permeation measurements (Stainless steel,

Be, W) or tritium permeation barrier films

• “post mortem” analysis of suitable shaped D loaded samples.

We are interested for cooperation.....

Page 36: "Jožef Stefan" Institute, Dept. of Surface Engineering and Optoelectronics Slovenian Fusion Association (SFA). MHEST Deuterium retention in ITER -grade:

Acknowledgement

This work was supported by MHEST and SFA and by

(EFDA), W6-TPP-RETMET.

Thanks for your attention.