EU-PWI Meeting Madrid 29 - 31 October 2007 Tritium_ release_ Be _materials1 Assessment of tritium retention and release from plasma facing materials under

EU-PWI Meeting Madrid 29 - 31 October 2007

Tritium_ release_ Be _materials

1

Assessment of tritium retention and release from plasma facing

materials under separate and simultaneous action

of temperature, irradiation and magnetic field

J. Tiliks, G. Kizane, A. Vitins, E. Kolodinska, G. IvanovV. Tilika, J. Jansons, I. Reinholds

Laboratory of Radiation Chemistry of SolidsInstitute of Chemical Physics

University of Latvia



2

TW5-TTBB-006-D8. Assessment of the effects of magnetic field,

radiation and temperature on the tritium release from beryllium pebbles

Task JW6-FT-2.27Investigation of the effect of magnetic field on

detritiation of beryllium tiles from JET

UT06-TTBBreeder.System for preparation of beryllium samples for

tritium release



3

• In the years 2004-2006 investigating tritium release from neutron irradiated pebbles and tiles a novel effect – increase in the tritium release at thermoannealing under simultaneous action of radition and magnetic field was observed.



4

• Problem• Samples• Experimental • Results –• I Chemical forms of tritium• II Sorption of tritium• III Detritation of irradiated materials• Conclusions• Outlook



5

Problem

• Considerable amounts of T and He accumulate in Be materials of fusion device and may cause technical and environmental problems. Tritium release from materials (Be pebbles, tiles etc.) is impeded.

• Materials will be under the simultaneous action of temperature (700-1000 K), radiation (up to 1018 neutrons·m-2·s-1), and magnetic field (MF, up to about 7-10 T).



6

The originality of the laboratory is a radiation thermomagnetic (RTM) rig developed on the basis of a linear electron accelerator ELU-4.

The RTM rig enables investigations of both -

• separate

• simultaneous action

of the 3 different factors –

1. Radiation

2. Temperature

3. Magnetic field

on different processes, e.g., tritium release, corrosion, etc.



7

Be pebbles • 1.0 non-irradiated - from FZK - 2006 • 0.5 g BERYLLIUM - from FZK - 2004• 0.6 g EXOTIC-8-3/13 - from FZK - 2007

Be tiles • 2 upper belt limiter tiles - irradiated JET - 2006• 1 toroidal limiter tile - non-irradiated JET - 2006

Planned • Be pebbles PBA (NRG) 2007• Be pebbles HIDOBE (FZK, NRG) 2008• Carbon tiles JET 2008 • other PFM 2009 >>

Organizational arrangements



8

Tiles JET (D+T) Pebbles BERYLLIUM Pebbles EXOTIC 8-3/13

Beryllium samples



9

No. Parameter/ The materialinvestigated

Be pebbles from experiment BERYLLIUM

Be pebbles from experiment EXOTIC 8-3/13

Be tiles from JET

1. Material type Brush Wellman FRP pebbles, 2 mm

Brush Wellman, IGA pebbles, 0.1 to 0.2 mm

Brush Wellman, Vacuum Hot Pressed,250×80×40mm

2. Grain size 40-200 μm 40-200 μm

3. Main impurities 3125 ppm BeO,1200 ppm Mg

3400 ppm BeO, 100 ppm Mg

4. Irradiation 97.4 days in 1994. HFR, Petten, fission spectra

449.8 days in 2000. HFR, Petten, fission spectra

D+D, D+T, T (1989-1996)

5. Irradiation fluence 1.24·1025 m-2 (E>0.1 MeV)

2.70·1025 m-2 (E>0.1 MeV)

6. Irradiationtemperature

780 K 800-900 K

7. Content of radiolytic gases: Helium Tritium

480 appm (1994)12 appm (1994) 7 appm (2004)

285 appm (2000)1,16 appm (2000)

8. Specific activity:tritiumgamma-impurities -(Co-60, Zn-65, etc.)

(1.2±0.4) GBq·g-1

(5±2) MBq·g-1

(0.034±0.004) GBq·g-1

(0.5±0.2) MBq·g-11.13 kBq/g



10

Experimental methods

• Lyomethod for analysis of tritium chemical forms and its distribution in Be samples - by measuring simultaneously the amount of H2

evolved and the tritium activity during dissolution.

• Thermosorption of tritium in samples of unused Be tiles.

• Thermoannealing of irradiated or 3H sorbed Be samples under action of Radiation and MF separately or simultaneously.

•Preparation of Be samples from irradiated and non-irradiated tiles.



11

Determination of chemical forms of T by lyomethod

1. Irradiated Be samples (To, T2,T+) in 2 M H2SO4

• Beo + 2H+ 2Ho

• Ho + Ho H2 (g. phase) =1.1010mol-1 s-1

• Ho + To HT (g. phase) K~1.1010mol-1 s-1

• To + To T2(doesn’t go, because [To] ,< 10-6 M)

• T2 (solid) T2 (g. phase)

• T+ (solid) T+ (solution)

• A =(AT2 +ATo)gas ph. + AT+solut.



12

• Beo + 2H+ 2Ho

• Ho + Ho H2 K=1.1010 mol-1 s-1

• Ho + Cr2O7-2 H+ + 2Cr+3 K=2.6.1010 mol-1 s-1

• Ho + To HT K=1.1010 mol-1 s-1

• To + Cr2O7-2 T+ + 2Cr+3 K~1.1010 mol-1 s-1

• T2 (solid) T2 (gas ph.)

• T+ (solid) T+ (solut.)

• Asum =(AT2 +0,10 ATo)gas ph. + ( AT+ + 0,90 ATo)solut.

Lyomethod with scavenger of To

2. Irradiated Be samples (To, T2,T+) in 2 M H2SO4and 0.5 M Na2Cr2O7



13

Determination of chemical forms of tritium



14

A setup for dissolution experiments.



15

Beryllium dissolution system

1999.-2002.

2002.-2007.



16

Tritium monitor behind safety wall

Thermomagnetic rig on the bases of electron

accelerator LINAC-4

Possible planned experiments - 5.4 T mobile superconducting solenoid magnet (Institute of

Physics of University of Latvia)

Tritium release experiments



17

A scheme of radiation thermomagnetic rig

1 – P-10; 2 - He + 0.1% H2 3 – a needle valve and a rotameter; 4 – a quartz tube or ampoule +

sample inside + thermocouple +heater;

5 –Zn+ thermocouple + heater; 6 –tritium monitor TEM 2100A + DDH

32 7 –tritium collecting; 8 – temperature control device; 9 – an analog-to-digital converter

ADC-212/310 – poles of an electromagnet; 11 – a beam current detecting grid; 12 – a current-to-voltage transducer; 13 – a Hall-effect transducer;14 – radiation shielding; LINAC – a linear electron accelerator

ELU-4.



18

Parameters of the radiation thermomagnetic (RTM) rig

Thermo-annealing of samples with and without radiationsimultaneous action of magnetic field in the isothermal regime or with a constant rate of temperature increase in a continuous system of tritium measuring.

• Temperature range - up to 1123 K , rate 1-10 K/min.• Duration of experiment - up to 10 hours.• Ionizing radiation – fast electrons ( E = 5 MeV, max run in material

up to 2.55 g/cm2), the dose rate up to 14 MGy/h.• The magnetic field where the sample is placed – up to 2 T.

• Sample volume 7 cm3, size (with the oven) - thickness 20 mm, irradiated area – up to 30 mm2 (diameter of the electron beam through the pole 20 mm).

• Interpolar distance – 15 mm.• It is possible to register also the electrical and optical

(radioluminescence) parameters during the experiment.



19

Thermal sorption of tritium. 555 mm cube-shaped Be samples from the non-irradiated limiter tile were used. A Be pebble irradiated in the

BERYLLIUM experiment was used as a tritium source. Tritium sorption was performed at 773 K for 3 h under 5 MeV fast electron radiation of 14 MGy/h and/or

magnetic field of 1.7 T.

Setup for tritium sorption in the RTM rig



20

Preparation of samples from Be tiles



21

Cutting of samples from tooth17 of Be tile “A”



22

Results – I Chemical forms of tritium and distribution in Be materials



23

Chemical forms of localized tritium

Pebbles BERYLLIUM (1994)0.6 -1.6 GBq/g (2007)

Pebbles EXOTIC – 8 -3/13 (2000) < flux 4 -18 MBq/g (2007)

JET tileA (10-60 kBq/cm2)B (2.4-4.8 kBq/cm2)

DT campaign



24

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 0.2 0.4 0.6 0.8 1

RL/R0

Tri

tiu

m s

pec

ific

act

ivit

y A

, G

Bq

/g

12

Distribution of the tritium (T2+To) localised in BERYLLIUM pebbles

1 - without treatment, 2 – 1123 K 2 h



25

0

0.5

1

1.5

2

2.5

3

3.5

0 0.2 0.4 0.6 0.8 1

RL /R0

Tri

tiu

m s

pe

cif

ic a

cti

vit

y A

L, G

Bq

/g

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

m /

m0

1

2

4

3

5

Distribution of the tritium (T2+To) localised in BERYLLIUM pebbles after treatment: 1 – none, 2 –1123 K 2 h, F dif.=25%; 3 –1123 K 2 h,1.7 T P=14 MGy·h-1, F dif=52%; 4 – the same treatment as for the curve 3, Fdif = 53.2%.



26

Inhomogeneous distribution of gaseous tritium in beryllium tile “B” annealed for 0.5 h under different conditions :

T – temperature 773 K, R – radiation 14 MGy/h, M – magnetic field 1.7 T.



27

Results – IISorption of tritium under action of

3 external factors



28

Thermosorption of tritium in non-irradiated beryllium tile

(3h, 773 K)T+

39%

To

30%

T2

31%

Chemical forms of the tritium sorbed in non-

irradiated beryllium tile (3h, 773 K)



29



30

Results – III Degree of detritiation of Be

materials



31

3025

40

54

0

10

20

30

40

50

60

1

Tri

tium

re

lea

se d

uri

ng

th

erm

oa

nn

ea

ling

,%

fro

m t

ota

l am

ou

nt

T=1123K, 2 h for all cases T=1123K, B= 1,7TT=1123, P = 14 MGy·h-1 T=1123, B=1,7, P = 14 MGy·h-1

T T+M

v

T+R

T+R +M

Tritium release from BERYLLIUM pebbles (2 mm)



32

y = -7.7614x + 35.926

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

0.00 0.50 1.00 1.50 2.00 2.50

Magnetic field, T

Trit

ium

rel

ease

, %

Influence of MF on the tritium release from BERYLLIUM pebbles at thermo-annealing 2 h, 1123 K



33

Tritium fractional release at annealing of samples of Be tile “A” in a continuous flow of He + 0.1 % H2. Curve labels denote: T – action of the given temperature; M – magnetic field of 1.7 T; R – 5 MeV fast-

electron radiation of 14 MGy/h.

-40

0

40

80

120

160

200

240

280

320

360

0 30 60 90 120 150 180 210 240 270 300 330

Time / minutes

Tri

tiu

m f

rac

tio

na

l re

lea

se

ra

te /

(pp

m o

f th

e t

ota

l T /

s)

-62.5

0

62.5

125

187.5

250

312.5

375

437.5

500

562.5

Tri

tiu

m f

rac

tio

na

l su

m r

ele

as

e /

(5 *

% o

f

the

to

tal T

); T

em

pe

ratu

re /

oC

TRMTRTM

T

TRM TR

TM

T

TRM

TR

TM T

Temperature

Tritium sum release

Tritium release rate



34

Facilitating influence of 3 factor action – T- temperature, R - radiation 14 MGy.h-1 , MF magnetic field 1.7 T on tritium release

from JET beryllium tile “A” 500 oC 0.5 h

1418

71

87

0

20

40

60

80

100

MF=0, R=0 MF=1.7 T, R=0 R=14 MGy∙h-1,MF=0

R=14 MGy∙h-1,MF=1.7T

Rel

ease

d t

riti

um

, %



35

Comparison of degrees of detritiation of JET Be tiles and BERYLLIUM pebbles



36

•The main diffusing particle of tritium in Be is To. T2 is trapped in structural defects in a Be pebble

(25 %)T …..T (singlet) T2 (recomb.)

•Diff. To + To To ....To

Uncorrelatated (75 %)T …..T (triplet) To + To (further diff.)

The MF can affect singlet-triplet transformation and also change the ratio of To / T2 (decrease of the tritium release is observed experimentally )

•The dissociation of the T2 is going under irradiation

• T2 (T2)* To ……To (E dissoc.= 4.6 eV, G (To) = 17.6 at./100 eV) Correlated pair

•A pair To ……To is created in singlet state with life time >10-9 s always, MF transforms it into triplet state and increases To amount.



37

Conclusions1. Simultaneous additional action of MF and radiation considerably

increases tritium release from Be tiles and pebbles at annealing: • by about a factor 2 for Be pebbles • by about a factor 6 for beryllium tiles

2. The main form of tritium localized in the pebbles and tiles is T2. The

main diffusing form is T0. Action of radiation and MF stimulate

transformation of T2 into T0.

3. Irradiation and MF separately increases tritium thermo sorption in beryllium. Irradiation with fast electrons increased the sorption of tritium by about 80% at about 1 Pa of T2 at 773 K for 3 h in the unused beryllium, magnetic field increased the sorption of tritium by about 30%, but the simultaneous action of magnetic field and radiation did not change the amount of the tritium sorbed.

4. The most part of the tritium sorbed was localized in subsurface layers up to depth of 80 μm of the beryllium samples.



38

OUTLOOK 2008-2012

• To implement project “Determination of tritium and analysis of carbon-based plasma-facing components before and after their detritiation with different methods” - EFDA JET TWP 2008

• Detritiation of PBA and HIDOBE beryllium pebles, Be12Ti pebbles under separate and simultaneous action of temperature, radiation and magnetic field. Cooperation with HFR (Petten, the Netherlands) and FZK (Karlsruhe, Germany).

• To investigate magnetic field effects on detritiation of PFM using mobile superconducting solenoid of 5.4 T of the Institute of Physics of the University of Latvia on other irradiation devices in the EU.

• To determine tritium retention in metals using lyomethod for assessment of efficiency of developed tritium removal technologies.

• To begin exploration of new fuel removal technologies targeted at tritium retention in metals (for ITER with all metal divertor)

• To investigate possible effects of radiation and magnetic field on structure of very small lithium orthosilicate pebbles (FZK )



39

Liekie slaidi



40



41

To test and estimate 3H release Simulate disruption on neutron irradiated Be decrease Be radioactive waste up to Low Level Waste (Tritium 12 kBq/g )from different materials in the RTM rig under action of temperature, radiation and MF separately and simultaneously

MaterialsContinue to investigate :Be and BexTiy pebbles (HIDOBE, PBA)Be tiles (JET) Start to research:Carbon tiles (JET) Other plasma facing materials (Inconel, CFC, W,)

Thermoannealing conditions:Temperature – a) up to 850 C with rate 5 – 10 C /min

b) in isothermal regime 600, 700, 800, 850 CMagnetic field - step by step up to 2 T,Dose rate - step by step up to 14 MGy/h

3H release from materials at 5 T magnetic field ( at Insitute of Physics)Further - 3H release under action of neutrons, magnetic field - Salaspils – Cyclotrone

Tritium sorption and desorption in different materialsTo obtain Li4SiO4 and Li2TiO3 pebbles with little grain size from their nanopowders by sol gel method`



42



43

Tritium release from Be tile “B” under different conditions of thermoannealing

912

45

63

0

10

20

30

40

50

60

70

1

Tri

tium

re

lea

se d

uri

ng

th

erm

oa

nn

ea

ling

,% fr

om

tota

l a

mo

un

tT=773K T=773K, B= 1,7T

T=773, P = 14 Mgy·h-1 T=773, B=1,7, P = 14 Mgy·h-1

T

T+R

T+M

T+R+M



44

No. Sample Ratio of the tritium released with MF and/or R

to the tritium released only with temperature

T+M T+R T+M+R

1. Be pebblesBERYLLIUM

0.8 1.3 1.8

2. Be tiles JET “A” and “B”

1.3 5.0 7.0



45

Tritium release from Be tile “B” under different conditions of thermoannealing



46

Non irradiated sample

Thermo sorptionAmpoule

(Temperature, radiation, magnetic field)

Dissolution

T2, HT residual

T2, HT, H2 distribution

H2SO4 Cr2O72-

LSM LSM

T+ T+, To



47

Thermosorption of tritium in non-irradiated beryllium tile (3h, 773 K)

0

1

2

3

4

5

6

7

8

ML=0; P=0 ML=1.7T; P=0 MF=0; P=14MGy∙h-1 MF=1.7 T;P=14MGy∙h-1

Ab

sorb

ētā

trit

ija

dau

dzu

ms

ber

ilij

a vi

rsm

ā, k

Bq. cm

- 2

T

T+M

T+R

T+M+R



48



49

Thermosorption of tritium in Be tiles

• Ionizing radiation (fast electrons, P=14 MGy.h-1) considerably facilitates T2 sorption, that may be connected with radiolysis of sorbed tritium molecules in a surface of Be and with increase a concentration of To, which diffuses easily.

• MF (1.7 T) increase tritium sorbtion up to 40 %. Possible mechanism – formation of radical pair (To... To) in singlet state from tritium sorbed on a surface of Be under thermodissociation. MF transforms radical pair in singlet state to triplet state and thus decreases recombination and increases To concentration.

• At present, decrease of sorption under simultaneous action of temperature, MF and radiation is not understandable. Possible reason could be the life time of different To radical pairs (thermodissociated and radiolysed) in comparison with the spin transformation time in the presence of MF.



50

Possible MF effect on the T release from a Be pebble

• T is localised in Be pebbles as atomic gas To (gas dynamic solution), as T2 (intergranular and intragranular bubbles), as chemically bound T+

(example, OT-).•

T diffusion in a Be pebble takes place by To (faster) or T2 (slower).



51

•Tritium diffusion go in 2 kinds as To (faster) and T2 (slower) in the Be pebble

(25 %)T …..T (singlet) T2 (recomb.)

•Diff. To + To To ....To

Uncorelatated (75 %)T …..T (triplet) To + To

(further diff.)

The MF can affect singlet-triplet transformation and also change the ratio of To / T2 (decrease of the tritium release is observed experimentally )

•The dissociation of the T2 is going under irradiation

•

• T2 (T2)* To ……To (E dissoc.= 4.6 eV, G (To) = 17.6 at./100 eV)• Correlated pair

•A pair To ……To is created in singlet state with life time >10-9 s always, MF transforms it into triplet state and increases To amount.



52

Conclusions1. Simultaneous action of temperature, MF and

radiation sufficiently increases tritium release from Be tiles and pebbles.

2. The main form of tritium localized in the pebbles and tiles is T2. The main difusing form is T0. Action of radiation and MF stimulate transformation of T2 into T0.

3. Irradiation and MF separately increases tritium thermo sorption in beryllium. Increased sorption as the result of simultaneous action of those factors was not observed, must be tested in next experiments.



53

Experiments planned for the nearest next period

• to investigate the detritiation of real irradiated Be tiles and pebbles at kinetic thermo annealing process at different temperatures, radiation conditions and MF intensities

• to optimize working parameters for such detritiation technology and to obtain improved statistics

• to investigate the complex action of different factors on the T2 sorption in non-irradiated Be samples.



54

Outlook

• To determine distribution of tritium in CFC tiles

• To investigate properties of T

• To estimate T release and retentioin under action of T T+R T+R+M

• To develop detritiation method



55

OUTLOOK 2008-2012

• To implement project “Determination of tritium and analysis of carbon- based plasma-facing components before and after their detritiation with different methods” - 2008

• To investigate magnetic field effects on detritiation of PFM using mobile superconducting solenoid of 5.4 T of Institute of Physics of University of Latvia on other irradiation devices of EU.

• To determine tritium retention in metals using lyomethod for assessment of efficiency of developed tritium removal technologies

• To begin exploration of new fuel removal technologies targeted at tritium retention in metals (for ITER with all metall divertor)

• To investigate possible effects of radiation and magnetic field on structure of very small lithium orthosilicate pebbles (FZK )

To test and estimate 3H release Simulate disruption on neutron irradiated Be decrease Be radioactive waste up to Low Level Waste (Tritium 12 kBq/g )

from different materials in the RTM rig under action of temperature, radiation and MF separately and simultaneously

MaterialsContinue to investigate :Be and BexTiy pebbles (HIDOBE, PBA)Be tiles (JET)

Start to research:Carbon tiles (JET) Other plasma facing materials (Inconel, CFC, W,)

Thermoannealing conditions:Temperature – a) up to 850 C with rate 5 – 10 C /min

b) in isothermal regime 600, 700, 800, 850 CMagnetic field - step by step up to 2 T,Dose rate - step by step up to 14 MGy/h

3H release from materials at 5 T magnetic field ( at Insitute of Physics)Further - 3H release under action of neutrons, magnetic field - Salaspils – Cyclotrone

Tritium sorption and desorption in different materialsTo obtain Li4SiO4 and Li2TiO3 pebbles with little grain size from their nanopowders by sol gel method• `



56

Lyomethod for determination chemical forms of tritium



57

Kinetics of the dissolution of a non-treated Be pebble in 2 M H2SO4

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0 500 1000 1500 2000 2500 3000 3500 4000

Time / s

Tri

tiu

m r

ele

ase

ra

te /

[M

Bq

/(g

*s)]

; H

yd

rog

en

ev

olu

tio

n r

ate

/ (

arb

. u

nit

s)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

Tri

tiu

m s

um

re

lea

se

/ (

GB

q/g

);

Ev

olv

ed

hy

dro

ge

n /

(m

ol_

H2

/ato

m_

Be

)

TritiumH2

Tritium

H2



58

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0 500 1000 1500 2000 2500 3000 3500 4000

Time / s

Tri

tiu

m r

ele

ase

ra

te /

[M

Bq

/(g

*s)]

;

Hy

dro

ge

n e

vo

luti

on

ra

te /

(a

rb.

un

its

)

0

0.2

0.4

0.6

0.8

1

1.2

Tri

tiu

m s

um

re

lea

se

/ (

GB

q/g

);

Ev

olv

ed

hy

dro

ge

n /

(m

ol_

H2

/ato

m_

Be

)

Tritium

Tritium

H2H2

Kinetics of T2 and H2 release at the dissolution of non treated Be pebbles 2 M H2SO4 + 0.5M Na2Cr2O7.



59

Possibilities of the RTM rig• Continuous investigations of tritium release in different

materials – Be, BeTi12, ceramics, Li17Pb83 etc.

• The RTM rig can be supplemented with a special additional system for investigations of corrosion of structural metal materials in liquid lithium.

• A special setup for investigations of mechanical strength of polymer composite materials.

• Investigations of formation of radiation-induced defects in solids by radioluminescence.



60

• Kāda purge gas to liberate tritium labāka?/



61

• Pebbles

• JET tiles• Tritium is localized mostly in gas form ( T2 + To),

amount of T+ form is insignificant. In the Be surface melted as the result of plasma exposure, tritium is found as small amounts of T+. In the side part of Be tile amount of tritium is insignificant, mostly in the form of T2.

Simultaneous action of temperature, MF and radiation increase tritium release from Be tiles considerably.

• Irradiation and MF separately increases tritium thermo sorption in beryllium. Increased sorption as the result of simultaneous action of those factors was not observed, must be tested in next experiments.



62

T release from irradiated Be tiles in different thermoannealing proccesses

• By increasing temperature of thermoannealing up to 835 C, 34 % of tritium releases in 0.5 h (without MF and radiation).

• Thermoannealing 0.5 h at 835 C in the presence of MF (2.34 T), but without radiation increase tritium release by 6% (up to 40 %)

• Temperature is a main factor influencing tritium release rate, MF without radiation slightly increases it.

Documents

EU-PWI Meeting Madrid 29 - 31 October 2007 Tritium_ release_ Be _materials1 Assessment of tritium retention and release from plasma facing materials under