The effect of neutron and gamma

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Nov 15, 2013 (3 years and 8 months ago)

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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 Technology

Atominstitut, 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
g

-

spectrum


Damage production


neutrons,
g

-

radiation


Scaling: Prediction of behavior in other radiation environments


Superconductors: NbTi, Nb
3
Sn, MgB
2
, 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
235
U

+ ~200 MeV

kinetic energy of fission products: ~165 MeV

prompt gamma rays: ~7 MeV


kinetic energy of the neutrons: ~6 MeV

energy from fission products (
b
-
decay): ~7 MeV

gamma 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 Source

Lawrence Livermore National Laboratory

LOW TEMPERATURE PHYSICS

Fission: prompt
g

emission

F.C. Maienschein

R.W. Peelle

W. Zobel

T. 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 keV

In 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
n
L
n
L
p
E
m
m
m
m
E
2
4


1
1
4



L
n
L
n
m
E
m
E
(Hydrogen)

Minimum energy to displace one atom:


(epithermal and fast neutrons)


B
p
E
E

~4 eV C
-
H

~few eV in metals

~5
-
40 eV in ionic crystals

Stable?



p
E
1 keV: Displacement cascades

Stable in HTS

Disintegrate at room temperature to small clouds of point defects in LTS

LOW TEMPERATURE PHYSICS

Damage Production: Neutrons

Nuclear reactions: (n,
g
), (n,
b
), (n,
a
) ,fission


Example:

10
B + n


7
Li (1 MeV) +
4
He (1.7 MeV)



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

(n,
g
), (n,
b
)
: point defects

LOW TEMPERATURE PHYSICS

Damage Production: Gamma rays

Interaction via electronic system:




Compton scattering:





Photoelectric effect:



Pair production:

g
g
E
mc
E
E
p
2
4
2
2


g
E
E
e

MeV

1.022

g
E
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
×
10
22

m

2

(E > 0.1 MeV)

LOW TEMPERATURE PHYSICS

Other Radiation Environments?


(
E
)

neutron cross section

T
(
E
)

primary recoil energy distribution

F
(
E
)

neutron flux density distribution

t

irradiation time in the neutron spectrum
F
(
E
)

t
T
E
dE
dE
d
dE
dE
d
E
T
E
T
D
F

F
F






)
(
)
(
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
T
c


-

through disorder

Normal state resistivity
r
n


-

through the introduction of additional scattering centers

Upper critical field
H
c2


-

through the same mechanism:
r
n



1/
l



k



H
c2

Critical current density
J
c


-

through the production of pinning centers

Changes of Superconducting Properties

LOW TEMPERATURE PHYSICS

Changes in Transition Temperature

maximum fluence around

7
-
10 x 10
23

m
-
2

(E>0.1 MeV)

Decrease at a fast fluence of1
0
22

m
-
2
:




NbTi: ~ 0.015 K



A
-
15: ~ 0.3 K



Cuprates: ~ 2 K



MgB
2
: ~ 4 K (n,
a
)!

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

Nb
3
Sn, 4.2 K

I
C
/ I
C0

EM Nb
3
Sn
at µ
0
H = 12 T
RHQT Nb
3
Al
at µ
0
H = 16 T


fast neutron fluence (m
-2
)
6 T

LOW TEMPERATURE PHYSICS

J

T

H

T
C

H
C2
(T)

J
C

LOW TEMPERATURE PHYSICS

J

T

H

T
C

J
C

H
C2
(T)

LOW TEMPERATURE PHYSICS

4
6
8
10
12
14
10
7
10
8
10
9


unirradiated
10
22
m
-2
J
c
(A/m
2
)
B (T)
MgB
2
4.2 K
fast neutron fluence: 10
22

m
-
2

Changes of the Critical Current

Maximum at around 1
-
2
×
10
22

m
-
2

depending on T
c
unirr
.

MgB
2
, 4.2 K

LOW TEMPERATURE PHYSICS


Decrease of J
C

at low fields


Increase of J
C

at higher field


Start of (overall) degradation
depends on temperature

(
1
-
2
×
10
22

m
-
2

at 77 K)


Crossover field (mT)

2x10
21

m
-
2

4x10
21

m
-
2

1x10
22

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 m

Conductor (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 t

A380: ~280 t

LOW TEMPERATURE PHYSICS

Impregnation of TF Model Coil

LOW TEMPERATURE PHYSICS












Dielectric strength at 77 K after reactor irradiation

10
21
10
22
0
20
40
60
80
100
120
0
Laminate
Sandwich
Dielectric Strength (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 for



each constituent of resin, i.e. H, C, O, N, ...)



production of H, He


gas production




g
-
r慹a


䑯獥a牡瑥⡇礯栩瑩浥猠楲牡摩瑩潮t瑩浥t⡨F






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 5x10
22
m
-
2
(E>0.1 MeV) in:

irradiated to 7.8x10
21
m
-
2
(E>0.1 MeV)



TRIGA Vienna:



IPNS Ar
gonne:




ZI
-
003:

from neutrons:

1
86
M
Gy

(50 %)

16.3
M
Gy

(39 %)


from gamma rays:

1
82
MGy

(50 %)

25.
9
M
Gy

(61 %)



------------------------

-------------------------



3
68
M
Gy

(10
0%)

42.2
M
Gy

(100%)



ZI
-
005:

from neutrons:

76
M
Gy

(30 %)

6.5
M
Gy

(20 %)


from gamma rays:

1
82
M
Gy

(70 %)

25.9
M
Gy

(80 %)



------------------------

-------------------------


2
58
M
Gy

(100%)

32.4
M
Gy

(100%)

LOW TEMPERATURE PHYSICS

Mechanical Tests

MTS 810 test facility

Tensile test specimen geometries

0,00
0,05
0,10
0,15
0,20
0,00
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
g
-
rays

IPNS Argonne

Influence of radiation environment and resin composition

Irradiation at ~340 K

Tests at 77 K

Epoxy

Bismaleimide

Epoxy

Scaling works well!

LOW TEMPERATURE PHYSICS

Garching ~ 5 K

Ekaterinburg 77 K

ATI ~340 K


Tests at 77 K

Influence of irradiation temperature and of annealing to RT

Epoxy

Bismaleimide

Epoxy

LOW TEMPERATURE PHYSICS

0
1x10
21
1x10
22
0
10
20
30
40
50
60
70
80
90
100
110
Cyanate ester
Cyanate ester/epoxy (40:60)
Epoxy


Mechanical strength (%)
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
C
H
3
H
C
N
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
UTS
irr
/UTS
unirr
(%)
1*10
22
m
-2
2*10
22
m
-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 % CE

T1 (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
ILSS
irr
/ILSS
unirr
(%)
1*10
22
m
-2
2*10
22
m
-2
4*10
22
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)

(10
21

m
-
2
)


Total absorbed

Dose


(MGy)


Gas Evolution


Mean
±

Sdev

(mm
3
)


Gas Evolution Rate

Mean
±

Sdev

(mm
3
g
-
1
MGy
-
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
-
404

CTD
-
404


Cyanate Ester


1

5


4.04

20.18


68
±

11

200
±

9


47.0
±

7.4

30.4
±

1.1


ER
Baseline


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 MgB
2
)


Decrease of transition temperature


Critical current initially increases (except NbTi) then decreases
(1
-
2x10
22

m
-
2
)


Scaling by damage energy


Insulators


Defects caused by (nearly) all neutrons and
g

rays


Degradation of mechanical properties


Gas evolution


Scaling by total absorbed energy (dose)