Electrical Resistivity Changes withNeutron Irradiation and Implications

for W Stabilizing Shells

Electrical Resistivity Changes withNeutron Irradiation and Implications

for W Stabilizing Shells

L. El-GuebalyFusion Technology Institute

University of Wisconsin-Madison

With input from:C. Kessel (PPPL)

ARIES Project MeetingBethesda, MD

July 29 - 30, 2010

2

Why Tungsten Shell?

• Per Kessel: (Shell thickness (in cm) / Resistivity (in Ohm.cm) ) > 15,000

• Tungsten: preferred material for ARIES stabilizing shells:• Reasonable resistivity (ρ) and shell thickness (~0.08 cm for ρ= 5.4 micro Ohm.cm @ RT)• High temperature operation (800 - 1200oC)• No active cooling

⇒ radiate heat to surrounding blanket and shield ⇒ simple shell design.

• Impact on tritium breeding depends on shell location within blanket.

CuAl

Fe

W 80 cm OB Blanket

SOL

3.8

cm F

W

5 cm

Bac

k W

all

Blan

ket-I

Blan

ket-I

I

W Vertical Stabilizing ShellW Kink Shell

Potential Locations forW Stabilizing Shells

3

Concerns

• W resistivity increases with:– Temperature– Neutron irradiation.

• Higher resistivity means thicker stabilizing shell.

• Concerns:– Impact on TBR– Temperature gradient within shell– Thermal stresses– Feasibility of radiative cooling?

4

Unirradiated W:Variation of Resistivity with Temperature*

• Electric resistivity of unirradiated W is well established.• W resistivity (in micro Ohm.cm):

ρW = 4.8 (1 + 4.8297e-3 T + 1.1663e-6 T2) for 25oC < T < 625oC

Ref: M. Billone’s memo to ARIES Team on “Electrical Resistivity of Tungsten,” (5/27/1996). Available at: http://www-ferp.ucsd.edu/LIB/PROPS/w.html

0

50

100

150

0 200 400 600 800 1000 1200

Res

istiv

ity(m

icro

Ohm

.cm

)

Temperature (oC)

ARIESW

At 1000oC, ρW increases 6 times,requiring ~0.5 cm thick W shell(> 0.08 cm thick shell at RT).

5

Tungsten Composition Changeswith Neutron Irradiation

• Some W atoms transmute into Re, Ta, Os, and other radioisotopes (see my5/2010 presentation).

• Transmutation level depends on irradiation time and neutron spectrum (hardnear FW or soft behind blanket).

• Example of W transmutations: W armor of ARIES divertor :

• Main transmutation products (Re, Ta, and Os) will increase W electricalresistivity further, requiring thicker W shell.

0

1

2

3

4

5

0 5 10 15 20 25

Hf-180Os-188W-181W-185Ta-180mHHf-179Re-186mOs-187Ta-182He Re-184

Ato

mic

Den

sity

(1019

ato

m/c

m3 )

Fluence (MWy/m2)

< 10% of W Transmutation Products

Divertor Armor

0

50

100

150

200

0 5 10 15 20 25

Ato

mic

Den

sity

(1019

ato

ms/

cm3 )

Fluence (MWy/m2)

> 90% of W Transmutation Products

Re-185

Ta-181

Re-187

Os-186

Divertor Armor

6

Variation of Resistivity ofTransmutation Products with Temperature*

• W, Re, Os, Ta resistivities (in micro Ohm.cm):W ρW = 4.8 (1 + 4.8297e-3 T + 1.1663e-6 T2) for 25oC < T < 625oCRe ρRe = 17.7 (1 + 4.5585e-3 T + 1.2447e-6 T2) for 25oC < T < 900oCOs ρOs = 9.49 (1 + 4.425e-3 T) for 0oC < T < 100oCTa ρTa = 12.45 (1 + 3.83e-3 T) - Ref. 2 - for 25oC < T < 100oC

Note errors in

Billone’s memo:

marked in red

Refs.: 1- M. Billone’s memo to ARIES Team on “Electrical Resistivity of Tungsten,” (5/27/1996). Available at: http://www-ferp.ucsd.edu/LIB/PROPS/w.html 2- CRC Handbook of Chemistry and Physics - 66th Edition (1985-1986).

0

50

100

150

0 200 400 600 800 1000 1200

Res

istiv

ity(m

icro

Ohm

.cm

)

Temperature (oC)

ARIES

Re

W

OsTa

W and Re exhibit parabolic variationswith temperature.

Linear variations assumed for Ta and Osat T > 100oC. Parabolic variation yieldshigher resistivity.

Q: How much Re, Ta, and Os in W shell?

7

Re, Ta, Os Atomic Fractions Estimatedusing ALARA Activation Code

• Two locations examined for W shells in ARIES-DB:I- 0.5 cm thick W shell behind OB FWII- 0.5 cm thick W shell between OB blanket segments.

• Two lifetimes considered: 3.4 FPY and 40 FPY.

Ave. OB NWL ~ 4 MW/m2

30

SOL

Skel

eton

Rin

g

Plas

ma

5 2080 cmOB Blanket

Vac

uum

Ves

sel

Gap Gap

> 2 27

Win

ding

Pac

k

Coi

l Cas

e

Coi

l Cas

e

3 3

3.8

cm F

W

5 cm

BW

W S

hell-

I

W S

hell-

II

Kappa = 2.2 Kappa = 1.8Potential Locations forKink Shell

(discrete toroidally)Potential Locations for Vertical Stabilizing Shell

(continuous toroidally)

8

Transmutation Products inARIES-DB W Shell

0

5

10

15

20

0 10 20 30 40 50

Ato

mic

Fra

ctio

n (%

)

W Shell-I Lifetime (FPY)

Re

Os

Ta

W Shell-I Behind FW

0

5

10

15

20

0 10 20 30 40 50

Ato

mic

Fra

ctio

n (%

)

W Shell-II Lifetime (FPY)

Re

Os

Ta

W Shell-II Between Blanket Segments

• W Shell-I (behind FW) generates highest transmutation products.• Transmutation products build up with irradiation time.

9

Change of W Electrical Resistivitywith Transmutation Products

• Experimental data for irradiated W with 14 MeV neutrons does not exist.

• Per Billone, electrical resistivity of irradiated W can be estimated bylaw of mixtures:

ρ = fW ρW + fRe ρRe + fTa ρTa + fOs ρos

where f = atomic fraction.

10

Change of W Shell Resistivitywith Irradiation and Temperature

W Shell-I behind OB FW W Shell-II between OB Blanket Segments

0

10

20

30

40

50

400 600 800 1000 1200

W S

hell-

I Res

istiv

ity(m

icro

Ohm

.cm

)

Temperature (oC)

3.4 FPY

40 FPY

Unirradiated W @ RT

Unirradiated W@ 500-1000 oC

0

10

20

30

40

50

400 600 800 1000 1200W

She

ll-II

Res

istiv

ity(m

icro

Ohm

.cm

)Temperature (oC)

3.4 FPY40 FPY

Unirradiated W @ RT

Unirradiated W@ 500-1000 oC

11

Impact of Change in W Resistivity onW Shell Thickness

W Shell-I behind OB FW W Shell-II between OB Blanket Segments

Δshell = 15,000 ρshell

0.0

0.2

0.4

0.6

0.8

400 600 800 1000 1200

W S

hell-

I Thi

ckne

ss(c

m)

Temperature (oC)

3.4 FPY

40 FPY

Unirradiated W @ RT

Unirradiated W@ 500-1000 oC

0.0

0.2

0.4

0.6

0.8

400 600 800 1000 1200

W S

hell-

II Th

ickn

ess

(cm

)

Temperature (oC)

3.4 FPY40 FPY

Unirradiated W @ RT

Unirradiated W@ 500-1000 oC

12

Could LiPb Serve as Stabilizing Shell?

• At 700 oC, ρLiPb ~150 micro Ohm.cm* ⇒ 2-3 cm LiPb

120

130

140

150

160

170

200 400 600 800 1000

LiPb

Res

istiv

ity(m

icro

Ohm

.cm

)

Temperature (oC)

Liquid LiPb235 oC < T < 1100 oC

_____________________* U.Jauch, G.Haase, B.Schulz, Thermophysical properties of Li(17)Pb(83) eutectic alloy, KFK 4144 (1986).

40

60

80

100

120

140

200 400 600 800 1000

LiPb

Res

istiv

ity(m

icro

Ohm

.cm

)

Temperature (K)

Solid LiPb293 K < T < 508 K

Liquid LiPb508 K < T < 933 K

•Options:–Encase 2-3 cm thick LiPb in FS structure to serve as stabilizing shell–Cool FS structure with He to remove nuclear heating–Place LiPb Kink shell behind FW to enhance physics–T removal in batch process–Flowing LiPb?–Start with solid LiPb?

•UW experimental Na loop at Forest’s lab could assess feasibility.

13

Conclusions

• W shell thickness should reflect change in resistivity with temperature andirradiation.

• Change due temperature is dominent .

• Kink shell behind FW offers physics advantages, but exhibits largest changein resistivity.

• TBD: Impact of shell on ARIES-DB TBR. Need location and thickness of both shells.

• Q: Could “2-3 cm LiPb encased in FS structure” serve as stabilizing shell?