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DAMAGING EFFECTS 
OF RADIATION... 
On Electronic Components 
By R. D. SHELTON and J. G. KENNEY 
Admiral Corporation, Chicago, Illinois 
AN EXPERIMENTAL approach to learning 
the effects of nuclear radiation on elec- 
trical systems can be divided into stud- 
ies of materials, components, and sys- 
tems. Opinions vary on the relative 
merits of the three approaches, but 
there is agreement that materials test- 
ing can be of great value in predicting 
the manner in which a component will 
fail, component testing will permit de- 
sign and fabrication of a system with 
reasonable survival potential, and only 
a systems test can provide assurance 
that system will function. 
Components testing has not been 
nearly as extensive as materials testing, 
and systems testing, because of greater 
complexity and lack of appropriate 
irradiation facilities, is practically non- 
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integrated Thermol—Neutron Flux (10'’n/cem?) 
FIG. 1. Two series of observations of in- 
sulation resistance under influence of re- 
actor radiation. Top chart shows resistance 
between aluminum drum and 14 ft of 
wire insulated with 149-in. polyethylene. 
Bottom shows similar experiment with poly- 
vinylchloride-insulated wire. Thermal neu- 
tron flux was 6 X 10!! n/cm?/sec 
92 
existent (1-3). This article is con- 
cerned with components testing. 
Rate and Integral Effects 
Deleterious effects can be divided 
roughly into two categories. Some 
occur immediately when the system is 
placed in the radiation field and are 
sensitive functions of radiation flux 
density; these are called rate effects. 
Long-term degenerative effects associ- 
ated with the total irradiation (the time 
integrals of the fluxes) are called inte- 
gral effects. The damage to a given 
component will depend on the mode of 
operation during irradiation, the mate- 
rials comprising the component, the 
spectrum of the nuclear radiation, the 
intensity and duration of the irradi- 
ation, and other environmental factors 
such as temperature and humidity. 
In-Pile Tests 
Under an Air Force contract, our 
company is investigating the effects of 
nuclear radiation on electronic compo- 
nents. From July of 1955 to July of 
1956 a variety of components have been 
irradiated in the CP-5 reactor of 
Argonne National Laboratory. Com- 
ponents were tested for performance 
before, during, and after irradiation, 
and ere withdrawn from the reactor 
after being subjected to an integrated 
thermal flux of 10!8n/em?. Associated 
gamma and fast-neutron fluxes varied 
with position in the reactor, but typical 
values were 5 X 10!* fast neutrons/cm? 
and 10!§ gammas/cm?. 
Standard military specifications were 
used as the guide in determining what 
tests should be performed. Compo- 
nents to be irradiated were given pre- 
irradiation tests at the Admiral Radi- 
ation Laboratory and then transported 
to the reactor for in-pile testing. Asa 
rule 18 components of a given type, but 
perhaps of different manufacturers, 
comprised a test. Six components 
were under active test and operating 
during irradiation; six were irradiated 
but not operated; six were not irradi- 
ated and served as a control group. 
Pre-irradiation testing was con- 
ducted at room temperatures, whereas 
in-pile testing was conducted at 50° C 
or above, depending on the amount of 
cooling and on the heat dissipated by 
the components being tested. The re- 
actor environment chosen for a particu- 
lar test was dictated somewhat by com- 
ponent size and availability of reactor 
space. Variations of reactor power 
were frequent enough to demonstrate 
the effect of different flux levels on 
component behavior. 
This article discusses the effects ob- 
served so far in conductors and insula- 
tors, resistors, capacitors, semiconduc- 
tors, and vacuum tubes. 
Conductors and Insulators 
Conductors are usually metals, which 
are relatively resistant to radiation 
damage, and insulators and dielectrics 
are chemical compounds with far less 
radiation resistance. A large volume 
of materials research has been accom- 
plished in the past few years and com- 
ponents manufacturers are becoming 
aware of the problems engendered 
by adding nuclear radiation to the 
environment (4-7). 
There are several ways in which 
wires and cables can be affected by 
nuclear radiation. , The entire space in 
a radiation field can be thought of as 
an ionization chamber with charges 
migrating wherever there are potential 
differences. Beta activity produced by 
neutron absorption may produce ‘‘nu- 
clear batteries” on a small scale, and 
