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Conf.67050/--/
MAY 1 8 1967
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H.C. 53.68 : .65
LEGAL NOTICE
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racy, complement, or untunut of the In suon conulaad la wis oport, or what he was
of any informelon, apparatus, method, or process disclosed laws report may not infringo
privily owned rights; or
D. AIMIMs way lar duas vu reopect to the use of, or for den peu roswung trou the
un of way talor nation, apparsti, mohod, or process din lowed in to report.
As word in the aboro, "persoa scutes on bekli ol the Commia.a" includes way one
ploys or contractor of the Connisolon, or owpicyue of sucha contracur, to the oment that
such omploys or contractor of the Conclusion, ur umployee of such coolructor preparos,
disuminaues, or provides access to, day !nformation pursuant to Na Jmploymnal or coatract
wild the Connissjon, or as employment will sucha contractor.
USE OF RESEARCH REACTORS IN RADIATION DAMAGE STUDIES
AND IN SOLID STATE AND METAL PHYSICS
D. S. Billington
Solid State Division, Oak Ridge National Laboratory
Oak Ridge, Tennessee, U.S.A.
The importance of radiation damage studies as an essential factor
in reactor technology will dictate concerted effort in this area of mate-
rials research for a long time to come. This is so because we do not have
at hand all the solutions to the radiation damage problems that are posed
by an advanced reactor technology. The advancing frontier of reactor de-
sign and development places ever-increasing demands on materials of reactor
construction, in the form of high temperatures, more corrosive environments,
higher flux and power levels, the need to achieve better neutron economy
and lower costs of construction. Hence, challenging new problems are ever
before those involved in radiation damage research.
Past successes in radiation damage research are attested by the
large numbers of reactors that are now in operation and are producing
* Research sponsored by the U. S. Atomic Energy Commission under contract
with Union Carbide Corporation.
DISTRIBUTOR OF THIS, DOCUMENT IS UNLIMITED
PRT
trouble-free operatior., both for economical power production and advanced
research. On the other hand, it is becoming clear that the use of nuclear
reactors in solid state and metal physics is becoming more important and
should play an ever-increasing role in many facets of research involving
the solid state. At Oak Ridge there are several reactors that are being
employed in fundamental and applied research. The High Flux Isotopes
Reactor (HFIR) is a recent example of a high flux rusearch reactor that is
operating routinely at fluxes above 1045 neutrons/cm? sec. It is uniquely
useful for transuranic isotope production (5 x 1015) and provides beam port
facilities for neutron scattering work (1 x 1015) unexcelled in any other
reactor (Fig. 1). The Oak Ridge Research Reactor (ORR) is another high-
power 140 MW) research reactor that is distinguished for its ability to ac-
commodate various experime:its simultaneously, for example, in-pile loops,
beam facilities, radiation damage facilities, ctc. In contrast to the gen-
eral purpose ORR, we have recently put into service a modernized version of
the Bulk Shielding Reactor (BSR), which is being devoted exclusively to
radiation damage research.
This reactor serves also as an example of some
of the advantages of a lower power reactor. As will be seen, a number of
experiments can be done easily that would be impossible or prohibitively ex-
pensive in a big reactor.
The BSR reactor was conceived by E. P. Blizard and was the first of
the "swimming pool" reactors. Although originally designed for shielding
studies of massive shield components, this type of reactor has found great
favor as a general research reactor. The original BSR has been superseded
by later models for shielding research, and we have therefore modified it
--.-
for radiation damage research. Figure 2 shows the general layout of the
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reactor system. The pool is 40 ft long by 20 ft wide by 22 ft deep. The
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reactor is light-water-moderated and cooled and consists of an array of
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MTR-type fuc! elements. The lattice is mounted on a bridge that can tra-
verse the entire length and width of the pool. The present power level is
2 Megawatt:s, and the reactor is uperated seven days a week, 24 hours a day.
An aluminum tank 46" x 30" x 32" containing hoavy water is mounted along-
side the reactor. The tank contains various vertical access tubes (2" in
diameter) that permit irradiation at several distances from the reactor
face (19", 29", 40") in a nearly pure thermal environment. One of these
access tubes can be shielded with bismuth to provide a gamma-ray-free en-
vironment. Samples can be removed from all these tubes while the reactor
is in operation. There is another bridge spanning the pool that provides
support for a liquid-nitrogen-cooled helium gas cryostat that can be placed
alongside or in a lattice position of the reactor. This arrangement permits
irradiation at 77°K with either thermal or fast neutiuns. Another facility
mounted on the bridge permits access to the lattice for fast neutron irra-
diation at pool temperature. A converter for providing fission spectrum
neutrons is mounted on the side of the pool and the reactor can be moved
into pasition for irradiation purposes. A helium cryostat (see Fig. 3) is
permanently mounted in the south end of the pool. This facility permits
irradiation at 3º-3.5°K with either thermal or fast neutrons. The fact
that the reactor can be moved away after irradiation permits long-time
annealing studies to be carried out in the absence of radiation, an import-
ant aspect in studying the motion energies and interaction kinetics of
radiatiun-produced defects at low temperature.
It is also possible to irradiate in a magnetic field in the helium
cryostat. Small solenoids of Nb 25 at. % Zr alloy, giving a field of
10-15,000 koe operating in the persistent mode have been used successfully
in fluxes of 1012 neutrons/cm² sec. The important points to be emphasized
about this reactor are its mobility, its wide variety of irradiation facili-
ties, and the potential for new types of experiments such as ESR, creep,
and magnetic measurements. Other techniques for reactor experiments havo
been discussed elsewhere."
Table I summarizes the operating characteristics of the BSR.
Uses of a Reactor in Radiation Damage Research
If we lean by radiation damage research that research which contrib-
utes directly to the solution of the problems that are present because of
the nuclear environment of operating or proposed reactors, then it is clearly
evident that reactors must be used for the research, since the operating
conditions can be exactly duplicated only in a reactor. The material to be
studied must be subjected to the appropriate number of thermal neutrons,
fast neutrons, gamma rays, and nuclear lieating provided for in the reactor
design. In the case of fuel elements, the presence of fission fragments is
IIIII
an additional requirement. The impurities introduced by transmutation ef-
fects must also be considered. We are interested also in bulk effects,
that is, the damage must occur throughout the mass of the sample, since
this is the condition of nuclear reactor radiation damage and we do not want
to put ourselves in the position of having to extrapolate from surface to
volume effects as is often the case in the use of other nuclear machines.
On the other hand, if we are involved in research that requires an
understanding of some basic solid state phenomenon that takes place in a
nuclear environment and hence is important to our understanding of the mech-
anism of radiation damage, but need not duplicate the operating conditions
nor involve the same materials of construction (the study is to be considered
...
...
as supporting research), then we look at a reactor from a different view-
point. We ask, what are the unique aspects of nuclear irradiation that in-
cline us to utilize the reactor in our studies? Let me list a few of these
-
that appear to offer significant advantages for current research and for
possible future experiments. Many of these points are obvious to those
engaged in radiation damage research but may be of interest to those con-
templating research in metal physics or solid state physics who are not
fully aware of a nuclear reactor's advantages.
1) Homogeneous damage
The low nuclear cross section of most metals, particularly for fasz
neutrons, means that the damage in the sample will be uniformly distributed.
The mean free path for most materials in this class is of the order of sev-
oral centimeters. It is true that much of the knock-on damage will be in
the form of clusters of defects, and in this sense the damage is not homo-
geneous. However, the distribution of these clusters is random throughout
the entire volume of the sample, and on this basis the damage may be con-
sidered homogeneous. Thermal neutron damage will also be random in nature
except when high-cross-section materials are being studied, such as cadmium,
boron, lithium (°li), or gadolinium. Fission fragment damage can be simu-
lated by the (n,a) reaction in B and ºli. The stopping power for the re-
coil alpha particle is about the same as a fission fragment in aluminum.
2) Control of defect introduction
We have control of the amount of damage introduced into the sample;
we can irradiate for long times at low flux levels or for short times at
high flux levels; we can give minute exposures or massive ones. We can fur-
ther control the effective dose by the irradiation temperature employed.
Contrast this versatility with the uncontrolled nature of quenching for the
introduction of vacancies or cold work for the introduction of dislocations
into a metal or alloy.
2a)
Transmutation doping.
Recent trends in materials research have placed an increasing empha-
sis upon ultra-pure materials as being an essential prerequisite to the
undertaking of research into the nature of the interaction of defects with
one another or with the host lattice. The eventual procurement of these
high-purity solids will mean that the controlled introduction of impurities
by transmutation reaccions can be utilized to good advantage where impuri-
ties in parts-per-billion or less are desired. Crawford and Clelana
have studied the effects of transmutation doping in germanium.
This tech.
nique would appear to be particularly valuable in the case of elements hav-
ing 100 percent abundance of a single isotope such as gold where the intro-
duction of mercury could be studied. However, one need not restrict his
attention to these exclusively, since it is possible to obtain separated
isotopes of the various elements.
It is also possible to think of experiments that involve massive
transmutation effects. Wittels, Stiegler and Sherrill have irradiated
197
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Au82H80.18: An interesting feature of this study is the fact that the
alloy was formed at a temperature of 85°C. Conventional formation of the
alloy by melting requires temperatures in excess of 400°C (see Fig. 4).
Another interesting suggestion has come from T. S. Noggle, 14) who
has proposed that one might observe the continuous formation of the Ag-Cd
phase diagram by irradiating isotopically pure "Pa to obtain "Ag which
then decays to "lca. Again, it would be possible to follow the continuous
formation of the various phases in the system at low temperature. Consider-
ation of other high-cross-section elements could lead to amusing and instruc-
tive experiments.
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3) Removal of damage
Most of the changes caused by n'iclear irradiation can be completely
annealed and the sample used over and over without any significant altera-
tion of the original properties. Exceptions to this are to be noted in the
case of high-cross-section materials and for excessively long irradiations
where the nuclear transmutations may begin to yield a significant effect.
In most cases the original purity of low-cross-section material is
such that £ very long irradiation is required before the level of transmu-
tation impurity approaches the original impurity content and hence for basic
studies poses no significant problems.
However, we must be careful to irradiate under those conditions that
are favorable to the formation of simple damage only (low temperature, for
example; high temperature can cause some problems. This is discussed in a
later section.). Furthermore, we should study only metals or simpie solids
and not alloys, since the possibility of radiation-induced phase changes
taking place must be considered. It is true chat the hardening caused by
cold work can be removed by an appropriate heat treatment, but in most cases
a certain amount of preferred orientation is retained. The effect of alloy-
ing, of course, cannot be removed.
4) Inert gas doping
It is usually not possible to introduce an inert gas into a metal or
alloy by the usual diffusional techniques because of the extremely low solu-
bility of the gas in the metal. However, if one is willing to allo; the
metal with appropriate amourts of ºli or ''B followed by irradiation in a
thermal neutron facility, the reaction B(n,a) will yield helium dispersed
throughout the sample, and as uniformly as the dispersion of the boron was
originally. This technique is not unique to reactors, since the use of
appropriate ions from an accelerator, if of sufficient energy, will introduce
the desired gas. However, in this case all of the ions will be found at
the end of the range unless special pains are taken to interpose absorbers
of varying thickness between the beam and the sample to achieve different
ranges of the ions in the sample under study. It requires an extremely
high-energy accelerator to achieve ranges of ions in solids that are com-
parable to the mean free path oi neutrons in solids.
To many workers in radiation damage the above discussion may be amus-
ing, since the presence of helium in reactor materials has been considered
a serious problem, being responsible for the reduced high temperature duc-
tility of stainless steel and Inconei, for example, rather than a useful
research technique. It may be of interest to note thać Weir and Martino
have found that the introduction of small amounts of titanium into the stain-
less steel causes the formation of stable titanium borides which are dispersed
homogeneously throughout the grains of the alloy rather than being concentra-
ted at the grain boundaries, as is the case in the absence of titanium. The
titanium additions significantly reduce the radiation-induced grain boundary
fracture. It is believed that this improvement in properties is caused by
the retention of the helium in the titanium boride so that it does not mi-
grate to the grain and a much smaller portion of the boride is to be found
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at the grain boundary. The above solution, which appears promising for
nickel and iron-base alloys contaminated with boron, does not appear adequate
for the problem of the fast neutron (n,a) reactions that take place in most
materials of reactor utility, at rates that approach the quantities of helium
generated by 5-10 ppm of boron in stainless under thermal neutron conditions.
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5
Nuclear heating
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This phenomenon that originates in the attenuation of nuclear radia-
tion in the sample is usually considered a problem that one must learn to
live with, but it is possible to take advantage of the effect to provide a
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-9-
uniform heat source that may be useful in controlling the temperature dur-
ing irradiation ?) or for use in calorimetry. 18The chief advantages lic
in the fact that one can really achieve uniform bulk heating under controlled
conditions.
6) Experimental space
A nuclear reactor, even the smallest ones, provides ample space for
irradiation purposes. Numerous sanples can be irradiated simultaneously,
under identical flux conditions or under conditions of varying flux.
it is
in this area that the smaller research reactors become particularly valuable.
The BSR, for example, provides sufficient space for varicus experimental con-
ditions and a!so provides adequate shielding for storage of radioactive mate-
rial in certain areas of the reactor pool. Thus, not only is it possible to
accommodate a large number of radiation damage experiments simultaneously,
but other programs, such as neutron scattering, activation analysis, isctope
production, nuclear physics, and radiation chemistry.
?)
Irradiation temperature
Again referring to the BSR, it can be seen that it is possible to ir-
radiate simultaneously at pool temperature, 3°K, 77°K, or any elevated tem-
perature, either in thermal neutrons or fission spectrum neutrons. This
versatility in this or other swimming-pool-type reactors is unnatched in any
other nuclear machine.
8) Enhanced diffusion
Another technique for studying phase diagrams by the use of nuclear
reactors comes about because of the fact that neutron irradiation leads, in
certain temperature ranges, to an increase in the defect (probably vacancy)
concentration above that of the equilibrium concentration, with a correspond-
ing increase in diffusion rates where the mechanism is vacancy controlled,
-10.
i.e., some reactions in alloy systems take place at such a low rate at room
temperature, for example, that no reaction is discernible in times nearly
infinitely long, but irradiation will supply the excess of vacancies required
to cause the reaction to proceed at a visible rate. Room temperature aging
in Cu-Be, Ni-Be, 19) and Fe-Cu; £10) order-discrder reactions in Cu,Au; [11]
short range order in Cu-Zn;12) and many other examples are available to
demonstrate the validity of this technique. Precipitation of minor constitu-
ents such as carbides and nitrides from iron has also been accelerated by
irradiation.
In the case of the enhanced precipitation of nitrides from
iron solid solution by neutron irradiation, the important factor appears to
be the production of additional nucleation sites. Electron irradiation does
not create nucleation sites, showing that individual lattice defects are not
sufficient to generate nucleation sites. 1157 See Fig. 5.
9) Dislocation pinning
D. 0. Thompson and D. K. Holmes 114) evolved a novel technique for
studying the pinning of dislocations by lattice defects. This technique,
which involves the measurement of internal friction and apparent elastic con-
stants in high-purity single crystals of copper, demonstrated that the pinning
and unpinning of dislocations could be studied reproducibly many times on the
same sample without any alteration of the original properties of the sample.
This is not really a radiation damage experiment, because of the extremely
small doses required. It would appear that this technique may have wide
applicability in metal physics.
10) Hardening
The ability of neutron irradiation to harden ultra-pure, hence ultra-
soft, single crystals has been employed by F. W. Young to good advantage.
His studies involve the preparation of high-purity single crystals of copper
-11-
with dislocation densities as low as 1-10/mm'. In this condition the slight-
est stress results in the introduction of additional dislocations. It was
found that exposing the crystals to an nvt of 1017 hardened the crystals
sufficiently to permit handling without altering the original dislocation
concentration.
11) Radiation-induced crystal structure changes
Another area of study that has uncovered a unique aspect of reactor
research involves irradiation of such compounds as BaTi0g, which are ferro-
electric compounds and possess a tetragonal crystal structure stable at room
temperature and a cubic perovskite structure at 120°C (the ferroelectric
point). Heavy irradiation converts the tetragonal phase to an expanded
cubic structure. Annealing at 1000°c, according to Wittels, et al.,!15
recovers much of the expansion, but recovery is more pronounced in co and
very little in an, so that the structure remains cubic and does not return
to the original room temperature structure. This technique appears to war-
rant a great deal of research in similar systems as a means of producing new
crystalline forms stable at room temperature.
Nuclear machines other than reactors have been useful in radiation
damage research. For example, the electron Van de Graaff is uniquely suited
for measurements of the threshold for atomic displacement by elastic colli-
sions. In addition, W. A. Sibley and Y. Chen have demonstrated that F cen-
ters can be formed under electron irradiation. There are other noteworthy
examples. However, it is the intent, here, to indicate the great versatility
and wide range of applicability of research reactors to radiation damage and
other solid state problems. A detailed study of the relative merits of the
various nuclear machines is in the literature.
-12-
I should now like to mention a few recent results of radiation dam-
age experiments that may be of interest. These are experiments that have
been done in Oak Ridge utilizing the BSR and the ORR, and are not meant to
be a survey of the entire field.
1) The effect of neutron dose rate on the increase in yield stress of
vacuum melted iron has been studied 18] for dose rates varying from 2 x 10"
to 3 x 10's neutrons/cm sec (E > 1 MeV) at 45°C. The total exposure for
each dose was 5 x 1018 neutrons/cm². In all cases a three-fold increase in
the yield stress occurred and no variation with dose rate could be observed.
This is a result of considerable engineering significance, since it
gives some validity to the concept of accelerated testing, of reactor compo-
nents. That is, most steels will be exposed to low flux levels for long
periods of time in an operating reactor, whereas it is desired to perform
radiation damage tests in short times at high dose rates.
It has been learned further that the stability of the radiation dam-
age increases with tutal dose.
2)
Another solution of interest to reactor technology has already been
mentioned above, in regard to the problem of helium bubbles in stainless
steels.
3) W. A. Sibley and Y. Chen (16] in their recent studies of both electron
and neutron radiation damage in Mgo have come to the conclusion that the
primary damage mechanism in Mgo is elastic collisions, i.e., similar to the
mechanism in metals.
They base this conclusion on the relative damage rates
between electron and neutron damage in MgO and copper. It, therefore, appears
that the ionicity of the crystal may make a difference in the damage mechan-
ism.
con
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-13-
4) Kernohan and Sekula119) have recently studied the effect of neutron
irradiation on the superconducting behavior of niobium. They found that by
irradiating niobium wires at room temperature the magnetization curve at
4.2°K was changed in the direction of improving the current carrying capacity
of the niobium. However, no change in the upper critical field or the transi-
tion temperature was observed (see Fig. 6). This technique may prove to be
of technological interest.
5)
Coltman and Klabunde 120% have continued their studies of thermal
neutron damage in metals. Their attention has been confined chiefly to ob-
servation of the damage caused by recoils from capture gamma ray emission.
Table II illustrates the relative sensitivity of typical elements to this
type of nuclear reaction. Several ir:teresting conclusions can be drawn from
their work. For example, they call attention to the relative amount of dam-
age that may be caused by thermal neutrons in a typical reactor environment
(see Table III). In an element like cadmium or gadolinium, it may be feas-
ible to study saturation effects using only modest fluxes (2 x 1012 neutrons/
cm´ sec). An important aspect of this study is that one can examine radia-
tion damage caused by low energy primaries which will produce from one to a
few Frenkel pairs and thus avoid some of the complications resulting from
radiation damage clusters or thermal spikes that are present from high-energy
knock-on recoils that result from fast neutron bombardment. Some elements,
such as aluminum and beryllium, have very low capture cross sections and as
a consequence do not show any thermal neutron damage. However, it is pos-
sible to create the conditions for thermal neutron damage in such elements
by alloying with appropriate amounts of a high-cross-section element. It
is possible to introduce 15/Gd into aluminum in such small amounts that no
appreciable effect on the properties of the aluminum can be noted (for exam-
ple, 0.01% Gd). Nevertheless, this amount of 1576d will result in an effec-
-14-
tive cross section for capture gamma damage in the aluminum of approximately
25 barns. Hence, appreciable damage will result when this alloy is irradia-
ted. Figure 7 summarizes some of their data on thermal neutron damage.
لسا
6) It has recently been observed by Hulett and coworkers12that when
copper single crystals are irradiated with fast neutrons in the temperature
range of approximately 450°C, the stability of the radiation damage is much
greater than when the irradiation is performed at or near room temperature.
The effect is observed in polycrystalline samples as well as single crystals.
Room temperature irradiation produces damage in the form of small, uniformly
distributed dislocation loops, of order 100 Å in diameter, which can be re-
moved by annealing at 300°-400°C. However, when the irradiation is performed
V 11
slightly above this latter temperature range, large dislocation loops and
tangles approximately 2000 Å in diameter are produced in distinct groups or
regions separated by relatively undamaged crystal. These regions caused
large, irregularly shaped etch pits on (111) surfaces (see Fig. 8). Borrmann
topography indicated the possibility of ultra-long-range order among the de-
fect regions. Moreover, the defect regions anneal non-homogeneously. The
closer the defect regions are to grown-in dislocations, the greater the tem-
perature stability. The significance of these observations is not entirely
understood, but since the effect is observed in a highly pure metal, it does
not seem possible to attribute it to an impurity effect, and hence it may
turn out to be an intrinsic aspect of high temperature radiation damage in
metals. Research is continuing on this phenoinenon.
I should like to mention briefly now two areas of research that have
evolved as a consequence of radiation damage investigations. The techniques
are not in themselves uniquely useful in radiation damage studies but rather
are finding will application in other areas of solid state research. They
-15-
do demonstrate the deep involvement of reactor research in many areas of
physics.
Anomalous Transmission
The recent utilization by F. W. Young and colleagues 122) of anomalous
X-ray transmission for the characterization of perfection in metal crystals
is an indirect product of the study of the effect of radiation damage on
surface reactions of metals. The need to provide defect-free surfaces led
to techniques for preparing high-purity, low-dislocation-density copper
single crystals, which eventually were of such high quality that for the
first time anomalous x-ray transmission was demonstrated in a plastic metal,
a feat previously thought impossible. The technique employs the diffracted
beam and not the direct transmission component. Later the effect was demon-
strated in high-purity zinc, niobium, and gallium. When the anomalous trans-
mission effect is combined with stereoptic techniques, the position of dis-
locations can be located within the bulk of the metal.
The fact that appre-
ciable transmission of x-rays through thicknesses of metal as great as 1.5
to 2 mm can be achieved provides a powerful tool in the study of defects
within the bulk of the metal. Figure 9 provides an example of what can be
achieved with this technique. The figure shows the low dislocation content
of the crystal and also the location of the dislocations as revealed by
topographs taken using different sets of diffracting planes. Its usefulness
was also demonstrated in uncovering the aspects of high temperature radia-
tion damage in copper mentioned earlier. This technique need not be used
only in radiation damage research, but in many aspects of metal physics.
Channeling
Another interesting aspect of radiation damage research that has led
to interesting applications in other fields is the concept of channeling,
-16-
first conceived vy M. T. Robinson and studied by Robinson and Oen123) in
connection with theoretical studies of the radiation damage cascade model
for the production of defects by neutron irradiation. The basic idea is
that along certain crystallographic directions there is more open space in
many crystal structures, hence a neutron or a knocked-on atom will suffer
fewer collisions, therefore resulting in a lower rate of defect production
along these channels. This idea has been verified experimentally. 124)
Figure 10 gives an excellent example of the observations made when T. s.
Noggle and 0. S. Oen125) studied radiation damage in thin Au films by ener-
getic iodine and bromine ions as a function of orientation of the film.
The effect of channeling in reducing radiation damage is quite pronounced.
Figure 11 illustrates channeling effects in another fashion. The discrete
energy loss peaks shown for the slightly misaligned beam experiment (b) is
presumably due to the transverse oscillation of the beam in the (111) planar
channel. If the appropriate equations can be formulated to account for
these oscillations, then a technique for measuring interatomic potentials
may become available. [20] The concept appears to have significance in cross
section studies, nuclear reaction yields, 127) and nuclear detector 120) per-
formance.
The above discussion makes it clear to me that reactors are indeed
unique research tools that have an essential role not only in radiation dam-
age studies but in defect solid state research, and when this is coupled
with the reactors' capability in neutron scattering studies and those tech-
niques that support solid state research, such as isotope production and
activation analysis, one can hardly afford not to have a reactor for research
purposes. It has been my pleasure to have been involved in the use of su-
clear reactors for radiation damage research for the past twenty years. I
find that my interest and enthusiasm is as high now as it was when I was
first introduced to the subiect.
ORNL DWG. 67-4212
TABLE I
FLUXES IN BSR IRRADIATION FACILITIES AT 2 Mw
Fast
(n/cm sec)
Thermal
(n/cmº sec)
Thermal/Epithermal
Ratio*
mal
«r>Dr)
y Heat
(watts/ gm)
(r/hr)
(waits time)
Liquid Helium
Cryostat
9.4 x 108 (S)
2.7 x 1042
91
Liquid Nitrogen
Cryostat
1.3 x 102 (N)
1.1 x 104
Core Position-15
Tube
1.7 x 1042 (N)
1.3 x 1048
0.2
Thermal Neutron
Irradiation Facility
Sample Tube Position:
E
CL
N,S
NW,SW
Planned Fission
Spectrum Facility
.50 x 10? (s)
9.6 x 10?
7.0 x 10?
140 x 10?
.39 x 1012
1.9 x 1012
1.5 x 102
5.5 x 1042
9.9 x 102
8.5 x 10
17 x 102
2.0 x 10°
1.5 x 109
2.8 x 109
7.3 x 105
27 x 105
2 1042
(F)
Fast Neutron Detectors: S = Sulfur, N = Nickel, F = Fission Spectrum.
*Ratio of activation of bare gold to cadmium covered gold.
UNCLASSIFIED
ORNL-LR-DWG. 75730
TABLE II
Zr
36.2
440
26
435
76
MEAN ATOM RECOIL ENERGIES FROM THE (n, y) REACTION
ELEMENTE Ēo
ELEMENT
ELEMENT Ē ĒO
(ev) (ev barns)
(ev) (ev barns)
1,319.0 438
201.0
6,909.0
3.1
Mo
148.5
407
3,611.7 256,000
87.6 13,700
1,831.2
124.1 7,820
1,003.8
3.4
134.4 330,000
1,161.3
12
83.3 16,300
870.8
212.3
133
415.0
76.3
770.6
177
103.3 723
473.2
79.0
2,290
644.3
129
76.9 431,000
621.7 323
81.3 350,000
716,1 24,100
91.3 4,200,000
547.6 1,134
61.8 59,000
639.1 281
55.7 3,620
391.9
9,406
114.4 19,800
427.6 2,480
63.1 8,010
433.0
2,210
69.0 7,250
389.1 1,210
54.8
1,151
371.1 4,900
60.8 1,170
387.2 985
55.3
4,760
305.0 711,300
61.5 27,700
567.0 2,722
381.9
1,440
81.0
8,000
295.2 325
97.4 37,000
168.9 473
93.2
317
186
456
161.4
27.4
179.4 2,210
44.2
1.50
214.3 1,440
25.7
237.4 287
38.8 105
187.8 246.0
ID3 Uuž žiüanŪxov >UŽUOZONO O on a
Tm
HE
Ta
56.8
500
Au
На
Th
U238
.
-
..
-.
-.
TABLE III
· THE RELATIVE IMPORTANCE OF THERMAL AND FAST NEUTRON DAMAGE
IN ELEMENTS IRRADIATED AT 4.5°K IN THE ORGR

% Thermal
| Ag
64
| 36
64
A1
-0*
-100
Au
67
33
67
95
Cd
95
5
Cu
22
78
Pt
27
73
27
% Fast
Not detected.
REFERENCES
[1] BILLINGTON, D. S., and THOMPSON, D. O., Programming and Utilization of
Research Reactors (IAEA), Vol. III, p. 223, Academic Press (1962).
CRAWFORD, J. H., Jr., and CLELAND, J. W., The Use of Radioisotopes in
the Physical Sciences and Industry, vol. I, p. 269, IAEA, Vienna (1962).
(3] WITTELS, M. C., STIEGLER, J. O., and SHERRILL, F. A., J. Appl. Phys.
33 (1962) 241.
[4] Private communication.
[5] HINKLE, N. E., ASTM Special Technical Publication No. 341 (1962) 344.
[6] WEIR, J. R., and MARTIN, W. R., "Solutions to the Problems of High-
---
Temperature Irradiation Embrittlement," ORNL-TM-1544, to be published
in Proc. of 3rd Intern. Symp. on Effects of Radiation on Structural
Metals, ASTM, Atlantic City, N. J. (1966).
[7] BERGGREN, R. G., private communication.
[8] COLTMAN, R. R., BLEWITT, T. H., and NOGGLE, T. S., Rev. Sci. Instr. 28
(1957) 375.
[9] KERNOHAN, R. H., BILLINGTON, D. S., and LEWIS, A. B., J. Appl. Phys. 27
(1956) 40; MURRAY, G. T., and TAYLOR, W. E., Acta Met. 2 (1954) 52.
(10) BOLTAX, A., Symposium on Radiation Effects in Materials, ASTM, Phila-
delphia (1957).
[11] SIEGEL, S., Phys. Rev. 75 (1949) 1823; BLEWITT, T. H., and COLTMAN,
R. R., Phys. Rev. 85 (1952) 384.
(12] ROSENBLATT, D. B., SMOLUCHOWSKI, R., and DIENES, G. J., J. Appl. Phys.
26 (1955) 1044.
(13) WAGONBLAST, H., and DAMASK, A. C., J. Phys. Chem. Solids 23 (1962) 221;
STANLEY, J. T., Diffusion in Body Centered Cubic Metals, ASM, Metals
Park, Ohio (1965).
S
[14] THOMPSON, D. O., and HOLMES, D. K., J. Appl. Phys. 27 (1956) 191;
J. Appl. Phys. 27, (1956) 713. ..
[15] WITTELS, M. C., and SHERRILL, F. A., J. Appl. Phys. 28 (1957) 606.
[16] SIBLEY, W. A., and CHEN, Y., Bull. Am. Phys. Soc. 12 3 (1967) 411.
[17] BILLINGTON, D. S., and CRAWFORD, J. H., Jr., Radiation Damage in
Solids, Chap. 4, Princeton University Press (1962).
(18) HINKLE, N. E., OHR, S. M., and WECHSLER, M. S., to be published in
Proc. of 3rd Intern. Symp. on Effects of Radiation on Structural
Metals, ASTM, Atlantic City, N. J. (1966).
(19) KERNOHAN, R. H., REED, R. E., and SEKULA, S. T., Bull. Am. Phys. Soc.
12 3 (1967) 310.
[20] COLTMAN, R. R., KLABUNDE, C. E., MCDONALD, D. L., and REDMAN, J. K.,
J. Appl. Phys. 33 (1962) 3509; COLTMAN, R. R., KLABUNDE, C. E., and
REDMAN, J. K., to be published in The Physical Review (April 1967).
[21] HULETT, L. D., Jr., BALDWIN, T. O., CRUMP, J. C. IIỊ, and YOUNG, F. W.,
Jr., Bull. Am. Phys. Soc. 12 3 (1967) 303.
[22] YOUNG, F. W., Jr., SHERRILL, F. A., and WITTELS, M. C., J. Appl. Phys.
36 (1965) 2225.
[23] ROBINSON, M. T., and OEN, 0. S., Appl. Phys. Letters 2 (1967) 31.
[24] PIERCY, G. R., BROWN, F., DAVIES, J. A., and McCARGO, M., Phys. Rev.
Letters 10 (1963) 399.
[25] NOGGLE, T. S., and OEN, O. S., Phys. Rrv. Letters 16 (1965) 395.
[26] LUTZ, H. o., DATZ, S., MOAK, C. D., and NOGGLE, T. S., Phys. Rev.
Letters 17 (1966) 285.
[27] THOMPSON, M. W., Phys. Rev. 15 (1964) 756.
[28] MOAK, C. D., DABBS, J. W. T., and WALKER, W. W., Rev. Sci. Instr. 37
(1966) 1131.
N
FIGURE CAPTIONS
Fig. 1
This Drawing Shows the Shield at a Beam Port of the HFIR Which
Encloses the Monochromating Crystal That is Used for Obtaining
Monoenergetic Neutrons for Neutron Diffraction or Inelastic
Scattering.
Fig. 2
Schematic Layout of Irradiation Facilities Associated with the
Bulk Shielding Reactor.
Fig. 3
Irradiation Cryostat. A continuously operating, closed-circuit
helium liquifier supplies liquid which flows around the thin-
walled copper sample chamber of the cryostat. During irradiation,
helium condensed in the sample chamber serves to maintain sample
irradiation temperatures of 3.5°K.
Fig. 4
(400) Reflections of Single Crystal Au before and after Thermal
Neutron Exposure (2.0 x 1021 n/cm²).
Fig. 5
Aging of the Nitrogen Peak in Iron-Nitrogen Alloy at 65°C.
Fig. 6
Effect of Fast Neutron Irradiation at 40°C on the Isothermal
Superconducting Magnetization of Niobium.
Fig. 7
Isochronal Recovery Rate Curves Obtained by the Measurement of
Resistance Changes after Thermal Neutron Irradiation at 3.5°K.
Peaks indicate the temperatures at which various damage recovery
processes become active.
Fig. 8
A Composite of Etch Pit Patterns, X-Ray Topograph, and Electron
Micrograph of Low Dislocation Density Copper Single Crystals
Irradiated with 1018 fast neutrons/cm“ at about 500°C. The upper
left and right photographs show etch pits formed at 20 micron
"defect regions" in areas of a crystal without and with grown-in
dislocations (etch pits), respectively. The lower left photo-
graph is an X-ray topograph taken of a sample prepared for elec-
tron microscopy by a jet polishing technique. The 10-200 micron
black spots are the "defect regions' representative of the high
temperature damage. The photograph at the lower right is an
electron micrograph showing the complicated structure of a single
"defect region" observed in the x-ray topographs and etch pit
patterns.
Fig. 9
Borrmann X-Ray Topographs of a Portion of a Copper Lamella -0.2 mm
Thick and with Dislocation Density 50/mm². The surface of the
lamella was (111) and the corresponding directions are indicated
in the figure. The dislocations exhibit contrast if their Burgers
vector does not lie in the ; lane being used for topography. Note
that the topographs are projections so their appearance may vary
between topographs.
Fig. 10
Transmission Electron Micrographs of 2200 Å Thick Single-Crystal
Gold Films Irradiated with 4.3 x 1010 51-Mev 1271 ions/cm². Cap-
tions under individual micrographs refer to the nominal misalign-
ment of the ion beam with [011]. Damage due to irradiation appears
as dark spots, variable in size and contrast, while large dark
regular-shaped areas are microtwins, and dark lines are disloca-
tions. Control micrograph is typical of unirradiated films.
Fig. 11
Energy Spectra of 60-MeV 1271 Ions after Passing through a 7000 Å
Thick Au Single Crystal. (a) (111) plane aligned with the beam
direction, (b) (111) plane tilted 0.5º from the beam direction.
The peak of the spectra in (a) corresponds to about one-half
the normal energy loss in this crystal of about 16 Mev. The
structure in (b) is interpreted as arising from the transverse
oscillations of the ions in the (111) planar channel of the
crystai.
.
.
..
MK
1.**
COMETCAL

STATIONARY WILD
MAN KA NDOD
MOCAMDA
SED
QUATRACTER KAM
OUTER CANIBACK
MTHONEAMERON MEIL
MOTATING SHELD
120° SWEEP
IVANTA E
MONOCHROMETER SHIELD FOR HFIR
DIAMETER - 7 FEET -8 INCHES
HEIGHT - 7 FEET
WEIGHT - APPROX. 70,000 POUNDS

FACILITY-
THERMAL NEUTRON
she.
MA.
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.
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TI
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III
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ORNL-DWG 67-4044
2
UNCLASHNICO
ORLDWG 6-7743

SAMPLE TUBE
- STAINLESS STEEL
HEAT TRAP, 8 in. LONG
THIN COPPER
REFRIGERATED HEAT
TRAP, 12 in. LONG
180K
18
TOTAL
SYSTEM
STAINLESS STEEL
HEAT TRAP, 2 in. LONG
THIN-COPPER
REFRIGERATED
SHIELD
- LIQUID HELIUM
3.5 TO 50K
REFRIGERATED SHIELD,
DU
THIN-WALLED COPPER
SAMPLE CHAMBER,
i-in. ID 8V2 in. LONG
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16-in:00 COPPER
TUBING
INCHES
wwwwwwwww
- REFRIGERATED SHIELD SUPPLY
- LIQUEFIER SUPPLY
'LIQUEFIER RETURN
ORNL-LR-DWG 60080
(400) REFLECTIONS
- Au CONTAINING
18 at. % Hg 198
INTENSITY (orbitrary units)
Au BEFORE
NEUTRON EXPOSURE
-
96.2

96.4
96.6
96.8
97.0
97.2
97.4 97.6
20
97.8
98.0
98.2
98.4
98.6
98.8
ORNL-DWG 63-6902R
FRACTION OF NITROGEN REMAINING
IN SOLUTION
O UNIRRADIATED
O IRRADIATED 23 days
AT TS-120°C
10
1000
.
YRN

100
TIME AT TEST TEMPERATURE ( min )
Aging of the Nitrogen Peak in Iron-Nitrogen
Alloy at 65°C.
ORNL-DWG 67-1937
NIOBIUM A
T= 4.2 °K
.
...
-47M (KG)
..-
• INITIAL ZONE - REFINED CONDITION
O IRRADIATED 2.6 x 1010 nvt (FAST)
A IRRADIATED 1x 1099 nvt (FAST)
---.

O
0.2
0.4
0.6
0.8
1.0
1.2
1.4
2.0
2.2
2.4
2.6
2.8
1.6 1.8
H (kOe)
3.0
3.2
ORNL-DWG 66-301
-
-
-
-
-
FCC
Cd
HCP
.
--
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ISOCHRONAL
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7 / 12 / 167
DATE FILMED
END







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