2019/10/31 Session TUN-1 C2

19th International Conference on Fusion
Reactor Materials(ICFRM-19)
in La Jolla, California, U.S.A.

Thermal Diffusivity of IrradiatedTungsten and Tungsten-Rhenium alloys

Masafumi Akiyoshi (Osaka Prefecture Univ.)
Lauren M. Garrison, Josina W. Geringer, Hsin Wang, Yutai Katoh (ORNL)
Akira Hasegawa, Syuhei Nogami (Tohoku Univ.)Degradation of Thermal Conductivity
in Ceramics

Divertor of Fusion Reactor
未照射 SiC: 230 W/m・K
Unirradiated
930℃

10MW/m2

HeGas Cooling
ガス冷却500℃
厚さ1cm～15000℃

1cm

Neutron中性子照射後SiC:
Irradiated

7 W/m・K

Thermal diffusivity of Tungsten
Thermal diffusivity / mm2/s

Thermal diffusivity in Metal / Ceramics
In Tungsten, heat is mainly carried byelectron like typical metals, but several
part of heat is carried by phonon likeceramics.

Unirradiated pure tungsten showed
n～0.5 and have a constant term as
α= a/Tn + c.
Furthermore, fusion neutron inducestransmutation element such as
Rhenium or Osmium that reduce
thermal diffusivity drastically.

40
α= a/Tn + c
200a=913
b=0.517c=13.4|r|=0.9988

500

1000

1500

Measurement temperature / K

Thermal Diffusivity / mm2・s-1

In ceramics, high temperature increase
phonon-phonon scattering and thermal
diffusivity α is described as α= a/Tn ,where unirradiated specimens shown = 1 and irradiated them show n < 1.

Pure W D10T1 specimen
Measured by LFA-457

6060
40% drop

40
20
0300

Almost Flat
response

Unirradiated D6T2 specimens
4003: Pure W thick plate(//)
500H: Pure W thick plate(⊥)

3% Re

9003: K-doped W-3%Re(//)
A00C: K-doped W-3%Re( ⊥)400600

500700Measurement Temperature / K

800

RB-19J Irradiation in PHENIX Project

W → Re, Os

In light water fission reactor, most neutrons
are moderated to thermal neutrons that gives
larger amount of transmutations than theThermal diffusivity change;
fusion reactor at the same irradiation
Electrically? Phonon scattering?
induced damage.

In the PHENIX project, irradiation in HFIR have been
performed with the Gadolinium thermal neutron shield.
Location: RB*
Dose: 0.2~0.7 dpa, 4 cycles
Temperature regions
400℃, 406 specimens
800℃, 389 specimens
1100℃, 359 specimens

Separate effect oflattice defects fromtransmutations.
Compare with rapid irradiation without Gdshield or TITAN is important.

Pure W and W-3Re Irradiated specimen
・D6T2 specimens irradiated in 500℃ zone
→ Thermal diffusivity measurement using LFA-457
in LAMDA up to 500℃

Thermal Diffusivity / mm2・s-1

Irradiation dose is assumed to be 0.2-0.7dpa for hole 19J capsule, where in thecase of 500℃ zone, it may be close to 0.2dpa.

7060

Pure W・Furthermore, at elevated temperaturethermal diffusivity of irradiated pure W
were getting close to that ofunirradiated.

Unirradiated D6T2 specimens
4003: Pure W thick plate(//)
500H: Pure W thick plate(⊥)
9003: K-doped W-3%Re(//)
A00C: K-doped W-3%Re(⊥)
Irradiated 500℃ Zone D6T2 specimens
4000: Irr. at 662℃ Pure W thick plate(//)
5001: Irr. at 548℃ Pure W thick plate(⊥)
9000: Irr. at 532℃ K-doped W-3%Re(//)
A000: Irr. at 660℃ K-doped W-3%Re(⊥)

15%

5040
400

500・It showed that the transmutation
effect was relatively limited, and only
phonon scattering were increased.
・Irradiation effect on K-doped W-3%Re
specimens were quite limited. Irradiatedspecimens showed almost same
thermal diffusivity with increasing
temperature.

W-3% Re

30300

・Irradiated Pure W specimens showed
obvious degradation in thermal
diffusivity, while they were higher thanthat of unirradiated K-doped W-3%Re
specimens.

600700Measurement Temperature / K

800

・The difference in grain orientation was
not observed. Irradiated K-doped W3%Re specimens showed a little
difference, but it may be arisen from
irradiation condition (130℃ different).

Annealing measurement procedure
RT 100℃

Specimen irradiated at 500℃
150℃ 200℃

Next day・・・・・・
500℃

As-irradiated measurement

Cool down in LHA-467HT
RT 100℃

150℃ 200℃

Next day・・・・・・
600℃ (60shot)

Isochronal annealing up to 600℃ andalso isothermal annealing at 600℃

Cool down in LHA-467HT
RT 100℃

150℃ 200℃

Next day・・・・・・
700℃ (60shot)

Cool down in LHA-467HT
These treatment will be continued up to 1100℃
At each step, NO Rad-Work is required.
(Liq. N2 must be supplied)

Isochronal annealing up to 700℃ andalso isothermal annealing at 700℃
At each isochronal annealing
temperature, dependence on
measurement temperature isobtained.

Thermal Diffusivity / mm 2・s-1

Annealing effect in irradiated specimens
70
D6T2 Specimens M easurement up to500, 600, 700, 800, 900(1), 900(2) ℃
5001 Pure W(⊥) T Irr 548℃

60

A000 K-doped W-3Re(⊥) T Irr 660℃

50・Now try to continue it up to1100℃ but a technical problem is
not resolved for high temperature
measurement using LFA-467HT.
・It looks that only a few pointdefects such as vacancies wereinduced. → Validate using positronannihilation lifetime measurement.

4030・Slight annealing recovery wasobserved at 900℃.

400

600

800

・It is required to compare

1000

1200 transmutation effects with Rapid

Measurement Temperature / K

specimens or TITAN specimens.

If only a few point defects that we can ignore are induced, we canforecast a thermal diffusivity after an irradiation with a calculation oftransmutation amount (and its distribution).

6Oscillation
at high temperature
measurement(LFA-467HT,tungsten at 900℃)
54Signal/V

32

10Calculation range

-1-50

050

100

150

Time /msSensor signal : shot: 96, step: 12
Identity : Novenver30th-Task1-Annealing-upto90
Temperature : 900.0 °C
Sample : 5001
2018-11-30 23:09:42
Date/Time :Material : --Instrument : LFA 467 Remark (measurement) : ---Thickness : 2.0390 mm
Diameter : 9.800 mm
Operator : HW
Remark (shot) : ---Model :
Cowan + p.c.
Diffusivity : 40.942 mm^2/s
Ampl. gain : 2002562.5 (1000x2003)
Created with NETZSCH Proteus softwareIRsignal curve
温度上昇曲線
試料： タングステンSpecimen:
Pure W (polished, Graphite spray coating)
温度：

グラフ中に記載

800℃

900℃

1000℃

Topic of presentation | Analyzing & Testing | Date created8Oxidation

K-doped W-3%Re and Pure W after themeasurements up to 500℃ in vacuum via RP
using LFA-457.

Pure W (ITER-G) and tungsten side of W/SiC
after a measurement up to 500℃ and 800℃
with Ar flow using LFA-457.

Pure W up to 800℃

K-doped W-3%Re up to 1100℃

Using LFA-467HT with a Turbo Pump

Ar leak from a valve insideof LFA-467HT cabinet givesa slight oxidation after ameasurement up to 800℃
on Pure W.

NETZSCH Japan reported there is NO oxidation with Arflow using LFA-467HT (without turbo pump)

Ar gas valve

To achieve high vacuum, Ar valve
at wall must be closed manually
after purge treatments.

Irradiation effect in tungsten
To separate electron conduction and phonon conduction,
electrical resistibility measurement at elevatedtemperature using specimen with different concentrationof Re must be performed.
In addition, positron annihilation lifetime measurement isrequired to estimate phonon conduction.
Electrical resistibility

ORNL(Using miniature specimens)

John Echols

Positron annihilation lifetime

Osaka Pref. Univ.

(Using miniature specimens)

H. AndoMiniature specimens
PHENIX Project: 2013-2018 6Year
PIE cannot wait the cooling.

Small specimen for thermal diffusivity
measurement is strongly required toreduce radio activity and volumetricheating during the neutron irradiation.

D10×T2Standard Specimen

D3×T0.5
Miniature Specimen→ TEM Disk Size

1/44 Volume → 1/44 Radio-Activity

In the PHENIX project, irradiation in HFIR have been performed with the specimen formof Diameter 3mm ×Thickness 0.5mm (D3TH) for thermal diffusivity measurement.
Specially manufactured specimen holders enable the measurement of this D3TH miniature
specimens.
10mmInSb IR Detector
Put InRadiated IR

Rear aperture

As D10Specimen
D3 Specimen holder manufactured by Mo-TEM alloy.

φ3mm specimen

Specimen holder

Netzsch LFA-467HT
Standard Specimen Holder(For 12.7mm specimen,

Pre aperture
Buffer ringwith 10mm Conversion ring)

Laser Flash
φ10 mmRequired thickness of specimen
Pulse width of Laser Flash in LFA-457: Tf = 330μs
LFA-467: Tf ≧ 20μs

for quality guarantee

ASTM E1461, JIS R1611, Netzsch recommend. → Require Tf < T1/2 / 10
α = 0.1388 t 2 / T1/2
α: thermal diffusivity, t: thickness, T1/2: half time

NETZSCH LFA-457
T1/2 > 3.3ms ( Tf×10)

NETZSCH LFA-467
T1/2 > 0.2ms → t > 0.31mm

Tungsten (unirradiated), α=66.0mm2/s→ Thickness t > 1.25mm
must be larger thanPure W, D3 t=0.598mm

Zoom Optics: IR sensor can focus
within D 2.7mm small area
Half time (T1/2)
0.87msec

25℃

Thermal diffusivity / mm・s-1

Validation of measurement using variousspecimen form using LFA-467HT
10080InSb sensor shows
rather noisy signal
around RT

Thermal diffusivity ofBridgestone Pure-beta
β-SiC samples
D10T2
D10TH
D3TH
4x4TH

D10T2, D10TH, D3TH, 4x4TH
different form Bridgestone Purebeta β-SiC specimens weremeasured using NETZSCH LFA467HT at ORNL.

60
40The results were analyzed withCowan Model (only one axis
thermal diffusion is considered).

200300400500600700Measurement temperature / K>150℃, all specimens showed
quite good agreement

800

SiC specimen does not needto prepare surface coating.

Thermal diffusivity / mm2 ・s-1

Importance of surface treatment
807060with Graphene spray
D10T1 ITER-G W
D3TH ITER-G W
with Graphite spray
D6T2 ITER-G W
D10T1 ITER-G W
D6T1 ITER-G W
D10TH ITER-G W (Oct26)
D10TH ITER-G W (Oct17)

50
4030

400
600
800
Measurement temperture / K

The measurement method was
already established. On the otherhand, measurement of PHENIXspecimens during 2018 was quite
limited because of NETZSCH US
sold conventional GRAPHITE
spray as GRAPHENE spray, and it
take a little long time to clarify it.
The spray bottle is treat as1000 dangerous object and cannot shipby air, and surface transport byship takes about 2monthes.

For 1mm thick W specimen, graphite spray is good enough.
On the other hand, 0.5mm thick specimens sometime showed smaller
value and we cannot use graphite spray for unknown specimen.

Surface Preparation

Very sparse black coating performed byGraphene nanoplatelets coating agent is required.
Density change of the black dots did not affects
the obtained thermal diffusivity.

Additional splay gives larger absorptions of flash lightand IR radiation that improved the S/N of the profile.
→ But too thick carbon layer cause additional time on
the measurement profile.

Data Fitting
Fit with full range

decline from themeasured data

TD: 104.6mm2/s

Fit within 5×T1/2 period

Thermal diffusivity was obtained
based on Cowan model fitting +Flash Pulse Collection.

leak flash

TD: 100.6mm2/s

The fitting range was fixed with 5times of the half time (T1/2) and theterm during leak flash was avoided
at the previous paper. Additional
work showed 6-7×T1/2 range gives
better matching confirmed byreference specimens.

Validation of measurement for D3TH tungsten
specimens with graphene spray using LFA-467
Polished metal surface was covered with brand new graphene nanoplatelet spray.

Thermal diffusivity / mm2 /s(Using LFA-467 in Japan (Prof. Kasada))
Extrapolation from datameasured at high temperature
D10T1: 66.6mm2/s
D3TH: 68.2mm2/s→ Only 2.3% error

80
D3TH ITER-G W→ at low temperature (ignored)
D10T1 ITER-G W

70605040300

400 500 600
700
Measurement temperture / K800

Measurement methodof thermal diffusivity
for D3TH specimen
using LFA-467 isestablished
M. Akiyoshi, et al., Fusion Engineering and Design,
136 Part A (2018) 513-517