Tests on irradiated magnet insulator materials

1381

Journal of Nuclear Materials 122 & 123 (1984) 1381-1385 North-Holland, Amsterdam

TESTS ON IRRADIATED MAGNET

R. E. SCHMUNK*,

INSULATOR MATERIALS

L. G. MILLER*,

and H. BECKER** 83415; **Plasma

*EG&G Idaho, Inc., Idaho Falls, Idaho Technology, Cambridge, Massachusetts

Fusion Center, Massachusetts

Institute of

Fusion reactor coils, located in areas where they will be only partially shielded, must be fabricated from materials which are as resistant to radiation as possible. They will probably Inorganic insulators incorporate resistive conductors with either water or cryogenic cooling. have been recommended for these situations, but the possibility exists that some organic Five insulator materials were investigated in this work, two insulators may be usable as well. containing E-glass cloth (contains B2O3) and three containing S-glass cloth (boron free). Disks of these materials were irradiated in two capsules in the Advanced Test Reactor at 325 K to a gamma dose of over 3.2 x log Gy, a fast neutron fluence of 3.5 x lo23 n/m2 (E > 1.0 MeV), Following and a total neutron fluence of 3.5 x lO24 n/m2 for the lower fluence capsule. irradiation, compressive fatigue tests were made at room temperature on all five candidate No failures were observed for the three insulators containing S-glass when cycled to materials. In comparison, the G-11CR a maximum stress of 345 MPa (50 ksi) for over 1.5 x 105 cycles. failed in a few cycles at the lowest stress level applied and the G-10 failed after a number of cycles which varied according to the applied stress level. Electrical resistivity measurements were also made; G-10 showed the largest decrease, and the materials containing S-glass showed the smallest decrease in resistivity due to irradiation. These insulators containing S-glass have given encouraging results for fusion magnet applications and should receive further consideration.

Irradiation

1. INTRODUCTION As fusion reactor designs continue

evolve, there appears to be a need for magnets that will function diation fields.

under moderately

Both conductors

high irra-

and insula-

tors used in the magnets must be able to withstand the damage produced Laminated mance

insulators

by these fields.

have their best perfor-

in configurations

perpendicular Designers possible

where the load is to the laminations. 192

have acknowledged

radiation magnets

that it should be

to design magnets

to take advantage 3 properties. Gamma

of these compression

doses predicted

are nominally

for fusion reactor

in the range of 1 x lo4

to 1 x lo7 Gy with neutron fluences 1 x 1O23 n/m2, depending intended function ally, stress

to

Addition-

levels for the insulators

up to approximately

range

275 MPa (40 ksi).

0022-3 115/84/$03.00 @ Elsevier Science Publishers (North-Holland Physics Publishing Division)

are reported

insulator materials.

include G-10 and G-llCR,

made with S-glass cloth.

on G-10 and G-11CR research

is an extension

at the Idaho National

Laboratory;4

The work

of previous

Engineering

the other three materials

were

selected based on lower dose irradiations testing

at Massachusetts

and

Institute of Tech-

nology.' Specimens Test Reactor

were irradiated

in the Advanced

(ATR) at 325 K followed

by test-

ing at room temperature.

Tests included

cycle compression

and electrical

nical properties was observed

fatigue

Less degradation and electrical

low-

in both mecharesistivity

for the three laminates made with

S-glass than for those containing

E-glass.

This indicates that all three S-glass

B.V.

They

both made with

E-glass cloth, and DGEBA, TGPAP, and KERIMID-601

resistivity.

on the design and

of the reactor.

and test results

here for several

to

insu-

1382

R. E. Schmunk

et al. / Tests on irradiated

magnet insulator materiab

lators should receive further consideration

an aluminum disk on one side.

for use in fusion reactors

was packed between the stack of disks and the

having moderate

exposure

that employ magnets

to radiation.

aluminum tube wall for a thermal bond. mal analysis predicted

2. INSULATOR SPECIMENS five different

insu-

sule and the specimen

lator materials

were included

in the work

to gamma heating

reported here.

A description

of the materials

was not monitored

The first four materials

blies.

the irradiation

made with a polyimide.

mentally

Specimens

3. SPECIMEN

assemblies

and testing.

irradiations.

were used to irradi-

ate the five insulator materials. laminates were loaded in capsule

ness of 0.89 mm.

5-2 and the

to determine

This position

has an acceptable

level of gamma heating,

but the neutron spec-

trum is well moderated.

To provide a greater

to the damage dose, the inside the fuel plate

5-4.

experimental

arrangement

is shown in Figure 1,

and a plot of the measured trum is shown in Figure 2.

disks 0.25 mm thick

disks were positioned

The

neutron flux specThe insulator

axially

in the capsules

at about 600-650 mm to take advantage

cimen stack in the capsule to enhance

enhanced

heat

Pairs of insulator disks were

gamma doses and neutron fluences the irradiations

that each insulator disk was in contact with

total fluences were calculated,

DESCRIPTION

Designation G-10 G-11CR DGEBA TGPAP KERIMID-601

of the

fast neutron flux in that region.

placed between aluminum disks in the stack so

TABLE 1.

obtained

are listed in Table 2.

in

based on the

DIGLYCIDYL ETHER OF DIGLYCIDYL ETHER OF DIGLYCIDYL ETHER OF TRIGLYCIDYL P-AMINO BIS-MALEIMIDE AMINE

BISPHENOL BISPHENOL BISPHENOL PHENOL

a. Similar to the resin used for G-1OCR except epoxy.

Woven Fabric Reinforcement

Hardener

Name of Resin A Aa A

ALIPHATIC AMINE AROMATIC AMINE ANHYDRIDE ANHYDRIOE __

it is formulated

The

The

OF INSULATOR MATERIALS

Chemical

in

experi-

fluences.

by 11.1 mm in diameter were added to the spe-

transfer.

assem-

neutron fluxes

assembly of another experiment. 5

of 15.9 mm and a wall thickAluminum

capsules

capsules were irradiated

were made of aluminum with an

outside diameter

Temperature

in the irradiation

neutron contribution

The E-glass

laminates were loaded in capsule

These capsules

in the capsule.

The I-9 hole in the ATR was used for the

IRRADIATION

Two capsule

differ-

center of 1 K (2°F) due

both fast and thermal

and consequent

(see Table 1) were cut from each of

the laminates for irradiation

S-glass

11.1 mm in

and ranging from 0.46 to 0.65 mm in

thickness

Ther-

Cobalt and nickel foils were placed

were made with epoxies while the fifth was

diameter

a temperature

powder

ential between the outer surface of the cap-

As stated previously,

is given in Table 1.

Aluminum

E-Glass E-Glass S-Glass S2-Glass S-Glass

with a lower molecular

Specimen Thickness (mm) 0.53 0.46 0.56 0.65 0.50

weight

1383

R.E. Schmunk et al. / Tests on irradiated magnet insulator materials

Test frame

-Fuel

10’6~

plates

Fast (E>l

A": 125

-Fusion irradiation capsule

MeV)

I

I

380

635

Axial position

(mm)

FIGURE 2 l-9 hole flux measurements

specimen FIGURE 1 Irradiation assembly showing the capsule containing the insulator specimens surrounded by the fuel plate assembly

disks placed between hardened

disks in the specimen

cartridge.

run in load control cycling the specified maximum

measured

2200 m/s and E > 1 MeV fluences,

include the contribution trons.

from epithermal

and

four of the materials.

neu-

for the material

4.1

4.4 x 10' Gy

stress level applied.

in both capsules.

The procedure reported

tested simultaneously

TABLE 2.

Fatigue in these tests was Five specimens

Thus, further compres-

The number of cycles at which

failure occurred

applied 4

previously.

were

in G-10 was determined

load-deflection

recordings

cedure reported

previously.

following

with the individual

maly occurred

In all tests for

in the continuous

Neutron Fluence

5-2 5-4

3.2 x 109 3.1 x 109

2200 m/s 7.2 8.0

X X

lO23 lo23

E > 1 MeV 3.5 x 1023 4.0 x 1023

an ano-

recording

(n/m2)

Gamma Dose -_.-W_-

from

the pro-

which a specimen failure was observed,

GAMMA DOSES AND NEUTRON FLUENCE DATA

Capsule

after only

sion fatigue testing of the G-11CR was not

TESTING

Compression

The other material,

a few cycles of a 207 MPa test, the lowest

attempted. 4. SPECIMEN

load.

in Table 3 for

G-llCR, showed rapid deterioration

The total dose to the organic component

of the laminates was approximately

between zero and

compression

Test data are summarized

steel

Tests were

Total

of

1384

R.E. Schmunk

TABLE 3.

COMPRESSION

et al. / Tests on irradiated

FATIGUE TEST DATA

magnet insulator materials

7.93 mm; D3, 11.1 mm; and Do, 7.14 mm. Silver conducting

Material

max (MPa)

(CycNles)

Resultsa

207 276 345

13,210 6,275 440

One disk failed Two disks failed One disk failed

G-10

KERIMID-601

DGEBA

TGPAP

a. Cartridge each test.

and guard ring.

100,000 165,701

No failure No failure

made.

241 345

195,413 257,444

No failure No failure

meter with a voltage of 100 V and a charging

disks while the resistance The measurements

Hewlett-Packard

Since this anomaly,

surements

specimen

groups.

Average

and values

are given in Table 4.

ELECTRICAL

RESISTIVITY

Electrical

we have

of failure was con-

of the specimens

of the cyclic

DATA

of a test.

Testing on the other three materials arbitrarily

at the indicated

The load-deflection

those tests suggested

was

recordings

that the specimens

were

copper with dimensions, of:

1.1 x 10'6

3.8 x lo7

G-1lCR

4.1 x 10'5

5.6 x 10'

KERIMID-601

1.4 x 10'5

7.9 x 10"

DGEBA

8.9 x 1015

1.6 x 1012

TGPAP

2.2 x 10'5

6.6 x 10"

5. DISCUSSION

received

were made on confor each of the

The electrode

con-

used was based on Figure 4 of All electrodes

G-10

The gamma doses and neutron fluences

specimens

five insulator materials.

Irradiated (n-cm)

for

Resistivity

measurements

trol and irradiated

Unirradiated @*cm)

Material

number

appreciably.

Electrical

Resistivity

either

loading process

during a test or at the conclusion

specification,

TABLE 4.

Duplicate mea-

were made for unirradiated

irradiated

were

Model 4329A high resistance

only in those tests for

failure occurred,

Verification

by interruption

figuration

measurements

were made using a

as a shift in the deflection

firmed by inspection

ASTM D 257.

against the

time of at least two minutes.

red as the point in the test at which failure

Resistivity

of

310 345

to hold the copper electrodes

taken the cycle number where the anomaly occur-

4.2

pressure

No failure No failure No failure

trace, was observed

not degrading

Hydraulic

0.70 MPa (100 psi) was applied

63,750 83,377 226,676

which a specimen

of cycles.

to the

gap between the center electrode

207 310 345

load versus deflection.

terminated

a con-

a gap on the other side corresponding conducting

obtained

took place.

to be measured:

tinuous coating on one side and a coating with

approximately

loading included five disks for

which appeared

paint was applied to both

sides of the specimens

u

were made of

per the referenced

D,, 6.35 mm; D2,

same.

by the two capsules were nearly the

The total dose to the materials

taining E-glass,

higher due to thermal which was present

con-

however, was considerably neutron fission

in 'OB

as B 0 in the E-glass. 218 B (n , o) 7Li

Each fission event via releases

2.8 MeV as kinetic energy to the

reaction

products

resulting

in an added dose

R.E. Schmunk

This added damage may be reflected

in the fact

fatigue failures

occur-

laminates made with S-glass.

sure of the damage to material

observed

in thin sheets,

by the fact that no failures were

Comparison

in fatigue. of the resistivity

trol versus irradiated

material

gests that the materials have fared better.

data for conagain sug-

containing

S-glass

The larger resistance

change for G-10 than for G-11CR compared the compression materials

by the U.S.

of Energy under DOE Contract

REFERENCES 1. E. A. Erez and H. Becker, in Nonmetallic Materials and Composites at Low Temperatures-2, eds. G. Hartwig and D. Evans, (Plenum Press, New York, 1982) pp. 59-71.

tests, even including G-11CR which

failed rapidly

suggests

that rather complex changes have occurred

in the two

materials. All three insulator materials

containing

have shown good resistance

ation and warrant

to irradi-

further consideration

fusion magnet application.

2. R. R. Coltman, Jr., J. Nucl. Mat. -108 and -109 (1982) pp. 559-571. 3. Meeting of the Task Force on Testing Organic Insulators for Fusion Reactor Magnets, Department of Energy Headquarters, Germantown, Maryland, September 8 and 9, 1982.

with

fatigue results for the same

due to irradiation

S-glass

mea-

for any of the single disk static

compression

This work was supported Department

The static

strength test is not a sensitive

as evidenced

1385

materials

No. DE-AC07-76ID01570.

red in G-10 and G-11CR but not in the three

compression

magnet insulator

ACKNOWLEDGMENTS

1 x 10 lo Gy.

to the E-glass of approximately

that early compression

et al. / Tests on irradiated

for

4. R. E. Schmunk, G. R. Imel, and Y. D. Harker, J. Nucl. Mat. 103 and 104 (1981) pp. 723-728. 5. L. G. Miller and J. M. Beeston, "Fuel Plate and Fusion Insulator Irradiation Test ProNovember 1980. gram," Report-EGG-FT-5273,