The effect of neutron and gamma radiation on magnet components

LOW TEMPERATURE PHYSICS

The effect of neutron and gamma radiation on magnet

components

Michael Eisterer, Rainer Prokopec, Reinhard K. Maix, H. Fillunger, Thomas Baumgartner,

Harald W. Weber

Vienna University of TechnologyAtominstitut, Vienna, Austria

RESMM Workshop, Fermilab, 14 February 2012

LOW TEMPERATURE PHYSICS

ACKNOWLEDGEMENTS

Work on the superconductors started at ATI in 1977 and was done partly at Argonne, Oak Ridge and Lawrence Livermore National Laboratories as well as at FRM Garching.

Work on the insulators started in 1983 and in systematic form in 1990.

Many graduate students and post-doctoral fellows have been involved.

Substantial support by the European Fusion Programme (EFDA) and by the ITER Organization (IO) is acknowledged.

The contributions of the ATI crew are gratefully acknowledged.

Senior scientists: H. Fillunger, K. Humer, R.K. Maix, F.M. Sauerzopf

Post-docs: K. Bittner-Rohrhofer, R. Fuger, F. Hengstberger, R. Prokopec, M. Zehetmayer

PhD students: T. Baumgartner, M. Chudy, J. Emhofer

LOW TEMPERATURE PHYSICS

Outlook

• Radiation environment in a fission reactor– Neutron and - spectrum

• Damage production– neutrons, - radiation

• Scaling: Prediction of behavior in other radiation environments

• Superconductors: NbTi, Nb3Sn, MgB2, cuprates– Transition temperature, critical current

• Insulators: epoxy resin, cyanate ester, bismaleimides– Dielectric strength– Mechanical properties

• Ultimate tensile strength, iterlaminar shear strength, fatigue behavior

– Gas evolution

• Conclusions

LOW TEMPERATURE PHYSICS

Fission of 235U

+ ~200 MeV

kinetic energy of fission products: ~165 MeVprompt gamma rays: ~7 MeV kinetic energy of the neutrons: ~6 MeVenergy from fission products (-decay): ~7 MeVgamma rays from fission products : ~6 MeV anti-neutrinos from fission products : ~9 MeV

http://www.atomicarchive.com/Fission/Fission1.shtml

LOW TEMPERATURE PHYSICS

Neutron Energy Distribution

Intense Pulsed Neutron Source, Argonne National Laboratory

Atominstitut, Vienna

Rotating Target Neutron SourceLawrence Livermore National Laboratory

LOW TEMPERATURE PHYSICS

Fission: prompt emission

F.C. MaienscheinR.W. PeelleW. ZobelT. A. Love

Second United Nations International Conference on the Peaceful Uses of Atomic Energy 1958

7 photons/fission, 7 MeV/fission, ~100 keV to ~8 MeV, peak at 300 keVIn addition: radioactive decay, e--e+ annihilation (511 keV), n-capture, Bremsstrahlung

Total: 1 MGy/h

LOW TEMPERATURE PHYSICS

Damage Production: Neutrons

“Elastic” collision with lattice atoms:

n

nL

nLp E

mm

mmE 2

4

11

4

LnL

n

mEm

E (Hydrogen)

Minimum energy to displace one atom: (epithermal and fast neutrons)

Bp EE ~4 eV C-H~few eV in metals~5-40 eV in ionic crystals Stable?

pE 1 keV: Displacement cascades

Stable in HTSDisintegrate at room temperature to small clouds of point defects in LTS

LOW TEMPERATURE PHYSICS

Damage Production: Neutrons

Nuclear reactions: (n,), (n,), (n,) ,fission

Example: 10B + n → 7Li (1 MeV) + 4He (1.7 MeV)

Neutron caption cross sections are most often largest at low neutron energies.

(n,), (n,): point defects

LOW TEMPERATURE PHYSICS

Damage Production: Gamma rays

Interaction via electronic system:

Compton scattering:

Photoelectric effect:

Pair production:

Emc

EEp 2

42

2

EEe

MeV 1.022E

Ionization!

• Breaks chemical bonds in organic molecules. (plastic deteriorates in sunlight.)

• Little effect in crystalline materials (superconductors).

LOW TEMPERATURE PHYSICS

Damage Calculation: Neutrons

Superconductors:

Insulators:

Fast neutron fluence: 4×1022 m−2 (E > 0.1 MeV)

LOW TEMPERATURE PHYSICS

Other Radiation Environments?

(E) neutron cross sectionT(E) primary recoil energy distribution(E) neutron flux density distributiont irradiation time in the neutron spectrum (E)

tTE

dEdEd

dEdEd

ETET

D

)()(displacement energy cross section

damage enegy

Superconductors:

Insulators:

Dose (total absorbed energy) [Gy]=[J/kg]

Scaling

Prediction of property changes in other radiation environments (?)

LOW TEMPERATURE PHYSICS

Transition Temperature Tc

- through disorder

Normal state resistivity n

- through the introduction of additional scattering centers

Upper critical field Hc2

- through the same mechanism: n 1/l Hc2

Critical current density Jc

- through the production of pinning centers

Changes of Superconducting Properties

LOW TEMPERATURE PHYSICS

Changes in Transition Temperature

maximum fluence around 7-10 x 1023 m-2 (E>0.1 MeV)

Decrease at a fast fluence of1022 m-2: • NbTi: ~ 0.015 K• A-15: ~ 0.3 K• Cuprates: ~ 2 K• MgB2: ~ 4 K (n,)!

LOW TEMPERATURE PHYSICS

Changes of the Critical Current

H.W. Weber, Int. J. Mod. Phys. E 20 (2011) 1325

NbTi, 4.2 K

RTNS (14 MeV)IPNS (distr.)

Damage energy scaling:

LOW TEMPERATURE PHYSICS

Changes of the Critical Current

H.W. Weber, Int. J. Mod. Phys. E 20 (2011) 1325

NbTi, 4.2 K

Irradiation temperature is rather unimportant! (intermediate warm-up)

LOW TEMPERATURE PHYSICS

Changes of the Critical Current

H.W. Weber, Adv. Cryog. Eng. 32 (1986) 853

Nb3Sn, 4.2 K

I C /

I C0

EM Nb3Sn at µ0H = 12 T RHQT Nb3Al at µ0H = 16 T

fast neutron fluence (m-2)

6 T

LOW TEMPERATURE PHYSICS

J

T

H

TCHC2(T)

JC

LOW TEMPERATURE PHYSICS

J

T

H

TC

JC

HC2(T)

LOW TEMPERATURE PHYSICS

4 6 8 10 12 14

107

108

109

unirradiated

1022 m-2

J c(A/m

2 )

B (T)

MgB2 4.2 K

fast neutron fluence: 1022 m-2

Changes of the Critical Current

Maximum at around 1-2×1022 m-2 depending on Tcunirr.

MgB2, 4.2 K

LOW TEMPERATURE PHYSICS

• Decrease of JC at low fields• Increase of JC at higher field• Start of (overall) degradation

depends on temperature (1-2×1022 m-2 at 77 K)

Crossover field (mT) 2x1021 m-2 4x1021 m-2 1x1022 m-2

77 K 244 382 630

64 K 114 219 440

50 K 130 195 334

Changes of the Critical Current

Y-123

LOW TEMPERATURE PHYSICS

14 mConductor (35

tons)

Coil Case(200 tons)

Winding(7 double pancakes)

Radial Plate (RP)(60 tons)

9 m

Structures

Insulation (glass and resin) ∼ 5 tons

7 RP

ITER TF coil design

TF Coil (300 tons) Boeing 747: ~185 tA380: ~280 t

LOW TEMPERATURE PHYSICS

Impregnation of TF Model Coil

LOW TEMPERATURE PHYSICS

Dielectric strength at 77 K after reactor irradiation

1021

1022

0

20

40

60

80

100

120

0

Laminate

Sandwich

Die

lect

ric

Str

eng

th (

kV

mm

-1)

Neutron Fluence (m-2

, E>0.1MeV)ITER

LOW TEMPERATURE PHYSICS

Radiation effects on insulators

Neutrons directly deposited energy by the entire neutron spectrum

(via computer codes and damage parameters foreach constituent of resin, i.e. H, C, O, N, ...)production of H, He → gas production

-rays Dose rate (Gy/h) times irradiation time (h)

Total absorbed energy (Gy)

Scaling quantity ?

LOW TEMPERATURE PHYSICS

Damage calculations

Examples: ZI-003 (Epoxy Resin) ZI-005 (Bismaleimide Triazine) 15 wt% H, 75 wt% C, 3 wt% N, 7 wt% O 5 wt% H, 73 wt% C, 10 wt% N, 12 wt% O

irradiated to 5x1022 m-2 (E>0.1 MeV) in: irradiated to 7.8x1021 m-2 (E>0.1 MeV)

TRIGA Vienna: IPNS Argonne:

ZI-003: from neutrons: 186 MGy (50 %) 16.3 MGy (39 %) from gamma rays: 182 MGy (50 %) 25.9 MGy (61 %) ------------------------ ------------------------- 368 MGy (100%) 42.2 MGy (100%)

ZI-005: from neutrons: 76 MGy (30 %) 6.5 MGy (20 %) from gamma rays: 182 MGy (70 %) 25.9 MGy (80 %) ------------------------ ------------------------- 258 MGy (100%) 32.4 MGy (100%)

LOW TEMPERATURE PHYSICS

Mechanical Tests

MTS 810 test facility Tensile test specimen geometries

0,00 0,05 0,10 0,15 0,200,00

0,25

0,50

0,75

1,00 = 0.8 max

u

l=

u*0.1

R=0.1

/

max

Time (s)

Fatigue measurements

LOW TEMPERATURE PHYSICS

TRIGA Vienna

2 MeV electrons

60-Co -rays

IPNS Argonne

Influence of radiation environment and resin composition

Irradiation at ~340 KTests at 77 K

Epoxy

Bismaleimide

Epoxy

Scaling works well!

LOW TEMPERATURE PHYSICS

Garching ~ 5 KEkaterinburg 77 KATI ~340 K

Tests at 77 K

Influence of irradiation temperature and of annealing to RT

Epoxy

Bismaleimide

Epoxy

LOW TEMPERATURE PHYSICS

0 1x1021

1x1022

0

10

20

30

40

50

60

70

80

90

100

110

Cyanate ester Cyanate ester/epoxy (40:60) Epoxy

Mec

hani

cal s

tren

gth

(%)

Neutron fluence (E>0.1 MeV)

Radiation Effects on Different Resins Tested for ITER

• Costs of CE up to 10 times higher than for epoxies

• CE can be mixed with epoxies for reducing costs

CE/epoxy blends

O

O

O

O

H

H

epoxy

O

O

CH3

H

CN

C

N

cyanate ester

LOW TEMPERATURE PHYSICS

T1 (100) (90°)

T2 (40) (90°)

T8 (30) (90°)

T10 (20) (90°)

Alstom (90°)

Ansaldo (90°)

0 10 20 30 40 50 60 70 80 90 100

UTSirr/UTS

unirr (%)

1*1022m-2

2*1022m-2

ultimate tensile strength after irradiation @ 77 K

DGEBF

20 % CE

DGEBA

30 % CE

40 % CE

100 % CE

0°

90°

286 MPa

265 MPa

387 MPa

269 MPa

313 MPa

250 MPa

Influence of CE content

LOW TEMPERATURE PHYSICS

DGEBF

DGEBA

20 % CE

30 % CE

40 % CE

100 % CET1 (100) (0°)

T1 (100) (90°)

T2 (40) (0°)

T2 (40) (90°)

T8 (30) (0°)

T8 (30) (90°)

T10 (20) (0°)

T10 (20) (90°)

Alstom (0°)

Alstom (90°)

Ansaldo (0°)

Ansaldo (90°)

0 10 20 30 40 50 60 70 80 90 100

ILSSirr

/ILSSunirr

(%)

1*1022

m-2

2*1022

m-2

4*1022

m-2

Interlaminar shear strength after irradiation @ 77 K

59 MPa

42 MPa

77 MPa

57 MPa

74 MPa

63 MPa

62 MPa

48 MPa

0°

90°

81 MPa

75 MPa

45 MPa

41 MPa

Influence of CE content

LOW TEMPERATURE PHYSICS

No significant influence of the irradiation!

Fatigue measurements @ 77 K

LOW TEMPERATURE PHYSICS

Bonded Glass/Polyimide tapes

Radiation resistant bonding agent necessary!

Delamination caused by weak bonding between resin and polyimide

LOW TEMPERATURE PHYSICS

Material 

Chemistry Neutron Fluence

(E>0.1 MeV)(1021 m-2)

Total absorbed

Dose (MGy)

Gas Evolution Mean ±

Sdev(mm3)

Gas Evolution Rate

Mean ± Sdev(mm3g-1MGy-

1)CTD-422

Cyanate Ester/Epoxy

1 4.19 105 ± 0 68.9 ± 2.4

CTD-10x

Cyanate Ester/Epoxy/BMI

1 4.05 83 ± 11 57.1 ± 6.8

CTD-101K

Epoxy/Anhydride

1 4.14 165 ± 0 108.4 ± 1.9

CTD-7x Cyanate Ester/Epoxy/PI

1 3.90 75 ± 0 48.2 ± 0.4

CTD-15x

Cyanate Ester/BMI

1 4.46 60 ± 0 38.9 ± 0.3

CTD-101

Epoxy/Anhydride

1 4.11 165 ± 21 114.3 ± 10.3

CTD-HR3

Cyanate Ester/PI

1 4.31 60 ± 0 33.9 ± 0.5

CTD-404CTD-404

Cyanate Ester 15

4.0420.18

68 ± 11200 ± 9

47.0 ± 7.430.4 ± 1.1

ER Baselin

e

Epoxy/Anhydride

1 4.15 263 ± 11 176.2 ± 10.3

Gas Evolution Rates

LOW TEMPERATURE PHYSICS

Conclusions• Minor influence of irradiation temperature• Superconductors

– Defects mainly caused by high energy neutrons (except MgB2)

– Decrease of transition temperature– Critical current initially increases (except NbTi) then

decreases (1-2x1022 m-2)– Scaling by damage energy

• Insulators– Defects caused by (nearly) all neutrons and rays– Degradation of mechanical properties– Gas evolution– Scaling by total absorbed energy (dose)