ASTM E521-96
(Practice)Standard Practice for Neutron Radiation Damage Simulation by Charged-Particle Irradiation
Standard Practice for Neutron Radiation Damage Simulation by Charged-Particle Irradiation
SCOPE
1.1 This practice provides guidance on performing charged-particle irradiations of metals and alloys. It is generally confined to studies of microstructural and microchemical changes carried out with ions of low-penetrating power that come to rest in the specimen. Density changes can be measured directly and changes in other properties can be inferred. This information can be used to estimate similar changes that would result from neutron irradiation. More generally, this information is of value in deducing the fundamental mechanisms of radiation damage for a wide range of materials and irradiation conditions.
1.2 The word simulation is used here in a broad sense to imply an approximation of the relevant neutron irradiation environment. The degree of conformity can range from poor to nearly exact. The intent is to produce a correspondence between one or more aspects of the neutron and charged particle irradiations such that fundamental relationships are established between irradiation or material parameters and the material response.
1.3 The practice appears as follows: Sections Apparatus 4 Specimen Preparation 5-10 Irradiation Techniques (including Helium Injection) 11-12 Damage Calculations 13 Postirradiation Examination 14-16 Reporting of Results 17 Correlation and Interpretation 18-22
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: E 521 – 96
Standard Practice for
Neutron Radiation Damage Simulation by Charged-Particle
Irradiation
This standard is issued under the fixed designation E 521; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
This practice is intended to provide the nuclear research community with recommended procedures
for the simulation of neutron radiation damage by charged-particle irradiation. It recognizes the
diversity of energetic-ion producing devices, the complexities in experimental procedures, and the
difficulties in correlating the experimental results with those produced by reactor neutron irradiation.
Such results may be used to estimate density changes and the changes in microstructure that would
be caused by neutron irradiation. The information can also be useful in elucidating fundamental
mechanisms of radiation damage in reactor materials.
1. Scope safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
1.1 This practice provides guidance on performing charged-
priate safety and health practices and determine the applica-
particle irradiations of metals and alloys. It is generally
bility of regulatory limitations prior to use.
confined to studies of microstructural and microchemical
changes carried out with ions of low-penetrating power that
2. Referenced Documents
come to rest in the specimen. Density changes can be measured
2.1 ASTM Standards:
directly and changes in other properties can be inferred. This
C 859 Terminology Relating to Nuclear Materials
information can be used to estimate similar changes that would
E 798 Practice for Conducting Irradiations at Accelerator-
result from neutron irradiation. More generally, this informa-
Based Neutron Sources
tion is of value in deducing the fundamental mechanisms of
E 821 Practice for Measurement of Mechanical Properties
radiation damage for a wide range of materials and irradiation
During Charged-Particle Irradiation
conditions.
E 910 Test Method for Application and Analysis of Helium
1.2 The word simulation is used here in a broad sense to
Accumulation Fluence Monitors for Reactor Vessel Sur-
imply an approximation of the relevant neutron irradiation
veillance, E706 (IIIC)
environment. The degree of conformity can range from poor to
E 942 Guide for Simulation of Helium Effects in Irradiated
nearly exact. The intent is to produce a correspondence
Metals
between one or more aspects of the neutron and charged
particle irradiations such that fundamental relationships are
3. Terminology
established between irradiation or material parameters and the
3.1 Definitions of Terms Specific to This Standard:
material response.
3.1.1 Descriptions of relevant terms are found in Terminol-
1.3 The practice appears as follows:
ogy C 859 and Terminology E 170.
Section
3.2 Definitions:
Apparatus 4
Specimen Preparation 5-10
3.2.1 damage energy, n—that portion of the energy lost by
Irradiation Techniques (including Helium Injection) 11–12
an ion moving through a solid that is transferred as kinetic
Damage Calculations 13
energy to atoms of the medium; strictly speaking, the energy
Postirradiation Examination 14-16
Reporting of Results 17
transfer in a single encounter must exceed the energy required
Correlation and Interpretation 18-22
to displace an atom from its lattice cite.
3.2.2 displacement, n—the process of dislodging an atom
1.4 This standard does not purport to address all of the
from its normal site in the lattice.
3.2.3 path length, n—the total length of path measured
This practice is under the jurisdiction of ASTM Committee E-10 on Nuclear
Technology and Applicationsand is the direct responsibility of Subcommittee
E10.08on Procedures for Neutron Radiation Damage Simulation.
Current edition approved Jan. 10, 1996. Published March 1996. Originally Annual Book of ASTM Standards, Vol 12.01.
published as E 521 – 76. Last previous edition E 521 – 89. Annual Book of ASTM Standards, Vol 12.02.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 521
along the actual path of the particle. 4.3 This practice relates to the generation of irradiation-
3.2.4 penetration depth, n—a projection of the range along induced changes in the microstructure of metals and alloys
the normal to the entry face of the target. using charged particles. The investigation of mechanical be-
3.2.5 projected range, n—the projection of the range along havior using charged particles is covered in Practice E 821.
the direction of the incidence ion prior to entering the target.
5. Apparatus
3.2.6 range, n—the distance from the point of entry at the
surface of the target to the point at which the particle comes to
5.1 Accelerator—The major item is the accelerator, which
rest.
in size and complexity dwarfs any associated equipment.
3.2.7 stopping power (or stopping cross section), n—the
Therefore, it is most likely that irradiations will be performed
energy lost per unit path length due to a particular process;
at a limited number of sites where accelerators are available (a
usually expressed in differential form as − dE/dx.
1-MeV electron microscope may also be considered an accel-
3.2.8 straggling, n—the statistical fluctuation due to atomic
erator).
or electronic scattering of some quantity such as particle range
5.2 Fixtures for holding specimens during irradiation are
or particle energy at a given depth.
generally custom-made as are devices to measure and control
3.3 Symbols:Symbols:
particle energy, particle flux, and specimen temperature. Deci-
A ,Z —the atomic weight and the number of the bombard-
1 1
sions regarding apparatus are therefore left to individual
ing ion.
workers with the request that accurate data on the performance
A ,Z —the atomic weight and number of the atoms of the
2 2
of their equipment be reported with their results.
medium undergoing irradiation.
depa—damage energy per atom; a unit of radiation expo-
6. Composition of Specimen
sure. It can be expressed as the product of s¯ and the fluence.
de
6.1 An elemental analysis of stock from which specimens
dpa—displacements per atom; a unit of radiation exposure
are fabricated should be known. The manufacturer’s heat
giving the mean number of times an atom is displaced from its
number and analysis are usually sufficient in the case of
lattice site. It can be expressed as the product of s¯ and the
d
commercally produced metals. Additional analysis should be
fluence.
performed after other steps in the experimental procedure if
heavy ion—used here to denote an ion of mass >4.
there is cause to believe that the composition of the specimen
light ion—an arbitrary designation used here for conve-
may have been altered. It is desirable that uncertainties in the
nience to denote an ion of mass #4.
analyses be stated and that an atomic basis be reported in
T —an effective value of the energy required to displace an
d
addition to a weight basis.
atom from its lattice site.
s (E)—an energy-dependent displacement cross section; s¯
d d
7. Preirradiation Heat Treatment of Specimen
denotes a spectrum-averaged value. Usual unit is barns.
7.1 Temperature and time of heat treatments should be well
s (E)—an energy-dependent damage energy cross section;
de
controlled and reported. This applies to intermediate anneals
s¯ denotes a spectrum-averaged value. Usual unit is barns-eV
de
during fabrication, especially if a metal specimen is to be
or barns-keV.
irradiated in the cold-worked condition, and it also applies to
4. Significance and Use
operations where specimens are bonded to metal holders by
diffusion or by brazing. The cooling rate between annealing
4.1 A characteristic advantage of charged-particle irradia-
steps and between the final annealing temperature and room
tion experiments is precise, individual, control over most of the
temperature should also be controlled and reported.
important irradiation conditions such as dose, dose rate,
7.2 The environment of the specimen during heat treatment
temperature, and quantity of gases present. Additional at-
should be reported. This includes description of container,
tributes are the lack of induced radioactivation of specimens
measure of vacuum, presence of gases (flowing or steady), and
and, in general, a substantial compression of irradiation time,
the presence of impurity absorbers such as metal sponge. Any
from years to hours, to achieve comparable damage as mea-
discoloration of specimens following an anneal should be
sured in displacements per atom (dpa). An important applica-
reported.
tion of such experiments is the investigation of radiation effects
7.3 High-temperature annealing of metals and alloys from
in not-yet-existing environments, such as fusion reactors.
4.2 The primary shortcoming of ion bombardments stems Groups IV, V, and VI frequently results in changes, both
positive and negative, in their interstitial impurity content.
from the damage rate, or temperature dependences of the
microstructural evolutionary processes in complex alloys, or Since the impurity content may have a significant influence on
void formation, an analysis of the specimen or of a companion
both. It cannot be assumed that the time scale for damage
evolution can be comparably compressed for all processes by piece prior to irradiation should be performed. Other situations,
increasing the displacement rate, even with a corresponding such as selective vaporization of alloy constituents during
annealing, would also require a final analysis.
shift in irradiation temperature. In addition, the confinement of
damage production to a thin layer just (often ; 1 μm) below 7.4 The need for care with regard to alterations in compo-
the irradiated surface can present substantial complications. It sition is magnified by the nature of the specimens. They are
must be emphasized, therefore, that these experiments and this usually very thin with a high exposed surface-to-volume ratio.
practice are intended for research purposes and not for the Information is obtained from regions whose distance from the
certification or the qualification of equipment. surface may be small relative to atomic diffusion distances.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 521
8. Plastic Deformation of Specimen 11. Dimension of Specimen Parallel to Particle Beam
8.1 When plastic deformation is a variable in radiation
11.1 Specimens without support should be thick enough to
damage, care must be taken in the geometrical measurements
resist deformation during handling. If a disk having a diameter
used to compute the degree of deformation. The variations in
of 3 mm is used, its thickness should be greater than 0.1 mm.
dimensions of the larger piece from which specimens are cut
11.2 Supported specimens may be considerably thinner than
should be measured and reported to such a precision that a
unsupported specimens. The minimum thickness should be at
standard deviation in the degree of plastic deformation can be
least fourfold greater than the distance below any surface from
assigned to the specimens. A measuring device more accurate
which significant amounts of radiation-produced defects could
and precise than the common hand micrometer will probably
escape. This distance can sometimes be observed as a void-free
be necessary due to the thinness of specimens commonly
zone near the free surface of an irradiated specimen.
irradiated.
8.2 The term cold-worked should not stand alone as a
12. Helium
description of state of deformation. Every effort should be
12.1 Injection:
made to characterize completely the deformation. The param-
12.1.1 Alpha-particle irradiation is frequently used to inject
eters which should be stated are: (1) deformation process (for
helium into specimens to simulate the production of helium
example, simple tension or compression, swaging, rolling,
during neutron irradiations where helium is produced by
rolling with applied tension); (2) total extent of deformation,
transmutation reactions. Helium injection may be completed
expressed in terms of the principal orthogonal natural strain
before particle irradiation begins. It may also proceed incre-
components (e , e , e ) or the geometric shape changes that
1 2 3
mentally during interruptions in the particle irradiation or it
will allow the reader to compute the strains; (3) procedure used
may proceed simultaneously with particle irradiation. The last
to reach the total strain level (for example, number of rolling
case is the most desirable as it gives the closest simulation to
passes and reductions in each); (4) strain rate; and (5) defor-
neutron irradiation. Some techniques for introducing helium
mation temperature, including an estimate of temperature
are set forth in Guide E 942.
changes caused by adiabatic work.
8.2.1 Many commonly used deformation processes (for 12.1.2 The influence of implantation temperature on helium
example, rolling and swaging) tend to be nonhomogeneous. In distribution (that is, dispersed atomistically, in small clusters,
such cases the strain for each pass can be best stated by the in bubbles, etc.) is known to be important. The consequences of
dimensions in the principal working directions before and after the choice of injection temperature on the simulation should be
each pass. The strain rate can then be specified sufficiently by evaluated and reported.
stating the deformation time of each pass.
12.2 Analysis and Distribution:
12.2.1 Analysis of the concentration of helium injected into
9. Preirradiation Metallography of Specimen
the specimens should be performed by mass spectrometry.
9.1 A general examination by light microscopy and
Using this technique, the helium content is determined by
transmission-electron microscopy should be performed on the
vaporizing a helium-containing specimen under vacuum, add-
specimen in the condition in which it will be irradiated. In
3 4 3
ing a known quantity of He, and measuring the He/ He ratio.
some cases, this means that the examination should be done on
This information, along with the specimen weight, will give the
specimens that were mounted for irradiation and then un-
aver
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