MCNP-4C2 and TRIM 98.01 based calculations of radiation damage

in copper

V. Slugeň, G. Farkas, P. DomonkošSlovak University of Technology Bratislava, Ilkovicova 3, 812 19 Bratislava, Slovakia,

e-mail:slugen@elf.stuba.sk

Aims•Simulation of the defects movement based on the Embedded Atom Method (EAM) potentials

and ab initio method in combination with Monte Carlo technique.

•Irradiation of specimens with neutrons and protons.

•Measurement of microstructure changes in materials using Positron annihilation techniques

compared with TEM.

•Heat treatment, measurements and evaluations of results from microstructutal point of view.

GB

[210]

<110>

The interatomic potential used in the simulation is based on the Embedded Atom Method (EAM).For additional simulations we usedAb initio method in combination withthe usual copper pseudopotential.

0 5 10 15 20 25 30 35 40 45-0.01

0.00

0.01

0.02

0.03

Relative graindisplacement (CLS cell%)

∆EGB

(J/m2 )

0 5 10 15 20 25 30 35 40 45-0.01

0.00

0.01

0.02

0.03

Relative graindisplacement (CLS cell%)

∆EGB

(J/m2 )

0 5 10 15 20 25 30 35 40 45-0.01

0.00

0.01

0.02

0.03

Relative graindisplacement (CLS cell%)

∆EGB

(J/m2 )

0 5 10 15 20 25 30 35 40 45-0.01

0.00

0.01

0.02

0.03

Relative graindisplacement (CLS cell%)

∆EGB

(J/m2 )

V acuum vessel

F irs t wall

Distribution of neutron fluency, atomic displacement, nuclear heating and nuclear reactions in copper alloys

foreseen for ITER first wall were calculated using Monte Carlo N-Particle Transport code MCNP-4C2.

Geometrical model consists of the slab with dimensions 12 x 12 x 0.5 mm, divided into 50 layers which create elementary cells with thickness 10 µm to provide detailed spatial distribution of the nuclear parameters. The shape of the modeled specimen correlates with the shape of samples used in the foreseen experiment - PAS measurements.

Arealneutron source

0.5 mm

12 mm

12 mmAlloy specimen

Vacuum

Specimens chemical composition and implantation dose.

Specimen Material Implantation dose[C/cm2]

SS CuCrZr – 98.95w.%Cu; 0.6-0.9w.%Cr; 0.07-0.15w.%Zr NoneSA CuCrZr 0.4SM CuCrZr 1.1TT CuAl25 – 99.5w.%Cu; 0.25w.%Al as Al2O3; 0.22w.%O as Al2O3;

0.025w.%B as B2O3

None

TA CuAl25 0.4TM CuAl25 1.1

MATERIAL CHARACTERISTICS OF THE SPECIMEN.

Material Mass density(g/cm3)

Isotope fraction (%)

Cu 8.93 63Cu 67.1765Cu 30.83

Distribution of primary knock-out atoms in the specimen

PARTICLE PRODUCTION IN THE SPECIMEN

8,3E-02

8,4E-02

8,5E-02

8,6E-02

8,7E-02

8,8E-02

8,9E-02

1 4 7 10 13 16 19 22 25 28 31 34 37 40

layer

nu

mb

er o

f P

KA

[at

om

s/(s

ou

rce

neu

tro

n.c

m3 )

]

Particle Total normalized production in the specimen

[1/(source neutron⋅cm3)]

Total unnormalized production in the specimen

(1/cm3)Photon 2.539E-01 7.842E11

Proton 1.324E-02 4.090E10

Deuterium 5.578E-04 1.723E09

3He 2.002E-07 6.184E05

The decreasing of the specimen activity in the time dependence

NUCLEAR REACTION IN THE SPECIMEN. Target isotope

Reaction Product Number of reactions[1/(source neutron⋅cm3)]

63Cu

(n,2n) 62Cu → 62Ni stable (st.) 1.82378E-02

(n,n´p) 62Ni st. 1.06331E-02

(n,n´α) 59Co st. 5.10850E-04

(n,p) 63Ni → 63Cu st. 1.86386E-03

(n,d) 62Ni st. 3.84324E-04

(n,3He) 61Co → 61Ni st. 1.55531E-07

(n, α) 60Co → 60Ni st. 1.70658E-03

(n,γ) 64Cu → 64Ni st. (61%)→ 64Zn st. (39%)

1.28033E-04

65Cu

(n,2n) 64Cu → 64Ni st. (61%)→ 64Zn st. (39%)

1.62292E-02

(n,n´p) 64Ni st. 3.02890E-04

(n,n´α) 61Co → 61Ni st. 1.39880E-05

(n,p) 65Ni → 65Cu st. 4.37881E-04

(n,d) 64Ni st. 1.73503E-04

(n,3He) 63Co→ 63Ni → 63Cu st. 4.66784E-08

(n, α) 62Co → 62Ni st. 1.82165E-04

(n,γ) 66Cu → 66Zn st. 1.47605E-05

1 MeV cascade accelerator at STU Bratislava

1 MeV cascade accelerator at STU Bratislava

Technical specificationTotal accelerating voltage: 0 - 1 MVRipple factor: < 1%Energy rangefor singly charged particles: 5 keV to 1 MeV Energy spread: 70 keV – 1 MeV: ≈ 2 keV

< 70 keV: < 0,1%Beam current: 1 - 100 µA

Ion implantation and measurements using PLEPS

• For the simulation of radiation stress of neutron flux, the ion implantation of protons has been applied.

• The proton mass is approximately identical as the neutron mass

• The energy of protons of about 95 keV was found out with the help of program TRIM 98.01

• Two implantation doses 1,1 and 0,4 C/cm2 were chosen

• Pulsed Low Energy Positron System PLEPS seems to be optimal technique for the evaluation of defects structure and concentration in Cu-alloys

• This system enables to study the micro structural changes in the region from 20 to 500 nm

Reasons for application of PAS• Mechanical tests give not enough information about changes in

material microstructure. Therefore, additional methods should be applied.

• PAS technique is a well-established method for studying open-volume type atomic defects and defect’s interactions in metals

• Ability of PAS to detect very small defects as well as very low defects concentration

• PAS can give additional information about • radiation induced defects,• thermal annealing of these defects.

SLUGEŇ, V. et. al.: Positron annihilation investigations of defects incopper alloys selected for nuclear fusion technology. In: Fusion Engineering and Design, 70/2, 2004, p.141-153

Non-destructive techniques for defects investigation

General overview of applicability range for some spectroscopy techniques [Howell, R., Physics Space Technology, 1987].

(OM – optical microscopy, TEM - transmission electron microscopy, nS – neutron scattering, STM/AFM – scanning tunnelling microscopy/atom probe ion microscopy).

PAS Theory

Scheme of positron experiments (A),

Quantitative illustration of positron annihilation γ-rays from different environments (B)

PAS Theory (PAS LT)

Lifetime spectra (PAS LT).Scheme of Lifetime measurement system

Three detector set-up of PALSrealization

BaF2 detectors and samples with 22Na source

PALS – electronic part

Start detector

Stop detector

2nd Stop detector(Energy)

Samples withpositron source

Distribution of vacancies in Cu-alloys after irradiation (calculated by TRIM)

0,00

0,20

0,40

0,60

0,80

1,00

0 100 200 300 400 500 600 700 800

Target depth [nm]

Vaca

ncie

s [v

ac/im

plan

ted

ion]

PLEPS

• Schematic view of the latest version of the pulsed low energy positron system.

PAS results10

0

300

500

457 37

8 305 238 178 124 78 41

140

160

180

200

220

240

260

280

300

MLT [ps]

Temperature [°C]

Depth [nm]

SS non-irradiated sample

•Non-irradiated CuCrZr sample (0 C/cm0 C/cm22)•There have not been observed any defects

100

250

400

550

457 34

1 238 15

0 78

26

140160180200220240260280300320

MLT [ps]

Temperature [°C]

Depth [nm]

SM proton irradiated sample (1,1 C/cm2)

•Irradiated CuCrZr sample (1,1 C/cm1,1 C/cm22)the shape of voids is spherical with diameter from 2 to 15nm

PLEPS Results for ITER

370

380

390

400

410

420

430

440

450

460

470

480

Ta u 2 [ p s ]

Te m p e r a t u re [ °C ]

En e rg y [ k e V] . Fo r C u 18 k e V~ 4 5 7 n m

S M s a mp le

470-480

460-470

450-460

440-450

430-440

420-430

410-420

400-410

390-400

380-390

370-3800

10

20

30

40

50

60

I2 [ %]

Te m p e r a t u re [ °C ]

En e r g y [ k e V] . Fo r C u 18 k e V~ 4 5 7 n m

S M s amp le

50-60

40-50

30-40

20-30

10-20

0-10

130

140

150

160

170

180

190

200

210

220

Ta u 1 [ p s ]

Te m p e ra t u re [ °C ]

En e rg y [ k e V] . Fo r Cu 18 k e V~ 4 5 7 n m

S M s a m ple

210-220

200-210

190-200

180-190

170-180

160-170

150-160

140-150

130-140

Decomposition of PASLT spectrum in two components

PAS and TEM results are useble for microstructural evalution of new materials

100120140160180200220240260280300320

MLT [ps]

Te m pe ra ture [°C ]

Ene rg y [ke V] . F o r C u 18 ke V~ 4 5 7 nm

SM sample

300-320280-300260-280240-260220-240200-220180-200160-180140-160120-140100-120

SLUGEŇ, V. – KURIPLACH, J. - BALLO, P. – DOMONKOŠ, P.: Hydrogen Implantation Effect in Copper Alloys Selected for ITER Investigated by Positron Annihilation Spectroscopy. Nuclear Fusion 44, 2004, p.93-97.

The calculated dependence of the positron lifetime on the size of the vacancy cluster in Cu.

PLEPS Results for ITER

Annealing behaviour of irradiated CuAl25-sample (TM)

18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3100120140160180200220240260280300320

MLT [ps]

Te m pe ra ture [ °C ] Ene rg y [ke V] . F o r C u 18 ke V~ 4 5 7 nm

TM sample

300-320280-300260-280240-260220-240200-220180-200160-180140-160120-140100-120

Conclusions I• The distinction between the two studied materials consists –

in accordance with TEM observations – in the fact that the microstructure of CuAl25 material is almost intact to irradiation contrary to CuCrZr.

• In CuCrZr material positron annihilation characteristics are apparently changed due to irradiation.

• Annealing up to 600 °C seem to result to a state similar to annealed non-irradiated sample.

• It is important to be very precise by sample preparationand by excluding of contributions from oxides, source, back-diffusion, etc.

Neutron irradiation at BR2 reactor

Nominal power 60-120 MWMaximum neutron flux (at 600 W/cm2)thermal neutrons 1.2×1015 n.cm-2.s-1

fast neutrons (E>0.1 MeV) 8.4×1014

n.cm-2.s-1

Days of operation per year 168 to 240Irradiation positions up to 100Cannel diameter up to 200 mm

Dose dependence, measured on PA samples irradiated to different dose levels at Tirr=50°C. Experimental values are compared with the

trapping model value τcalc, using trapping rate κ values.

PA sample Tirr=50ºC

141 ps

112,3 ps

93 ps 91ps ± 34ps

206,4 ps

192,08 ps

168,7 ps

178,5 ps

0

50

100

150

200

250

0 0,001 0,01 0,1

Dose [dpa]

Life

time c

ompo

nent

s [ps

]

tau1tau2MLTtau1calc

The intensity I2 of the long-lived component in dose dependence for neutron irradiated prime aged CuCrZr

(Outokumpu) alloy.

PA sample Tirr=50ºC

79,9%

54,3%

64,6%

96,0%

0

10

20

30

40

50

60

70

80

90

100

110

0 0,001 0,01 0,1Dose [dpa]

Inte

nsity

I 2 [%

]

Trapping rate κ into the defect (trapping site) in neutron irradiated PA sample at Tirr=50°C for three different

irradiation doses.

PA sampleTirr=50ºC

3,58

16,8

9,43

83,7

0

10

20

30

40

50

60

70

80

90

0 0,001 0,01 0,1Irradiation dose [dpa]

Tra

ppin

g ra

te

[ns-1

]

• In all neutron irradiated samples from dose 1×10-1 dpaup to 3×10-1 dpa the values for the positron mean lifetime increased and the defect lifetime of 175±5 pswas observed. Thus, compared to the non-irradiated state an additional trapping site was observed, probably in the form of Stacking Fault Tetrahedra.

• In all the positron lifetime measurements on neutron irradiated samples no lifetime component longer than 206 ps was observed, implying that no voids are created in the neutron irradiated CuCrZr (Outokumpu) alloy.

Results from PAS experiment at neutron irradiated samples (collaboration with Risoe N.L. and SCK.CEN Mol)