ASTM E521-96(2009)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: E521 − 96(Reapproved 2009)
Standard Practice for
Neutron Radiation Damage Simulation by Charged-Particle
Irradiation
This standard is issued under the fixed designation E521; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Thispracticeisintendedtoprovidethenuclearresearchcommunitywithrecommendedprocedures
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
Section
Apparatus 4
1.1 Thispracticeprovidesguidanceonperformingcharged-
Specimen Preparation 5-10
particle irradiations of metals and alloys. It is generally Irradiation Techniques (including Helium Injection) 11–12
Damage Calculations 13
confined to studies of microstructural and microchemical
Postirradiation Examination 14-16
changes carried out with ions of low-penetrating power that
Reporting of Results 17
cometorestinthespecimen.Densitychangescanbemeasured Correlation and Interpretation 18-22
directly and changes in other properties can be inferred. This
1.4 The values stated in SI units are to be regarded as
informationcanbeusedtoestimatesimilarchangesthatwould
standard. No other units of measurement are included in this
result from neutron irradiation. More generally, this informa-
standard.
tion is of value in deducing the fundamental mechanisms of
1.5 This standard does not purport to address all of the
radiation damage for a wide range of materials and irradiation
safety concerns, if any, associated with its use. It is the
conditions.
responsibility of the user of this standard to establish appro-
1.2 The word simulation is used here in a broad sense to priate safety and health practices and determine the applica-
imply an approximation of the relevant neutron irradiation bility of regulatory limitations prior to use.
environment.Thedegreeofconformitycanrangefrompoorto
2. Referenced Documents
nearly exact. The intent is to produce a correspondence
2.1 ASTM Standards:
between one or more aspects of the neutron and charged
C859Terminology Relating to Nuclear Materials
particle irradiations such that fundamental relationships are
E170Terminology Relating to Radiation Measurements and
established between irradiation or material parameters and the
Dosimetry
material response.
E821Practice for Measurement of Mechanical Properties
1.3 The practice appears as follows:
During Charged-Particle Irradiation
E910Test Method for Application and Analysis of Helium
Accumulation Fluence Monitors for Reactor Vessel
This practice is under the jurisdiction of ASTM Committee E10 on Nuclear
Technology and Applicationsand is the direct responsibility of Subcommittee
E10.08 on Procedures for Neutron Radiation Damage Simulation. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Aug. 1, 2009. Published September 2009. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ε1
approved in 1976. Last previous edition approved in 2003 as E521–96(2003) . Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/E0521-96R09. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E521 − 96 (2009)
Surveillance, E706 (IIIC) important irradiation conditions such as dose, dose rate,
E942Guide for Simulation of Helium Effects in Irradiated temperature, and quantity of gases present. Additional attri-
Metals butesarethelackofinducedradioactivationofspecimensand,
in general, a substantial compression of irradiation time, from
3. Terminology years to hours, to achieve comparable damage as measured in
displacements per atom (dpa). An important application of
3.1 Definitions of Terms Specific to This Standard:
such experiments is the investigation of radiation effects in
3.1.1 Descriptions of relevant terms are found in Terminol-
not-yet-existing environments, such as fusion reactors.
ogy C859 and Terminology E170.
3.2 Definitions: 4.2 The primary shortcoming of ion bombardments stems
3.2.1 damage energy, n—that portion of the energy lost by
from the damage rate, or temperature dependences of the
an ion moving through a solid that is transferred as kinetic microstructural evolutionary processes in complex alloys, or
energy to atoms of the medium; strictly speaking, the energy
both. It cannot be assumed that the time scale for damage
transfer in a single encounter must exceed the energy required evolution can be comparably compressed for all processes by
to displace an atom from its lattice cite. increasing the displacement rate, even with a corresponding
shift in irradiation temperature. In addition, the confinement of
3.2.2 displacement, n—the process of dislodging an atom
damage production to a thin layer just (often ; 1 µm) below
from its normal site in the lattice.
the irradiated surface can present substantial complications. It
3.2.3 path length, n—the total length of path measured
must be emphasized, therefore, that these experiments and this
along the actual path of the particle.
practice are intended for research purposes and not for the
3.2.4 penetration depth, n—a projection of the range along
certification or the qualification of equipment.
the normal to the entry face of the target.
4.3 This practice relates to the generation of irradiation-
3.2.5 projected range, n—the projection of the range along
induced changes in the microstructure of metals and alloys
the direction of the incidence ion prior to entering the target.
using charged particles. The investigation of mechanical be-
3.2.6 range, n—the distance from the point of entry at the havior using charged particles is covered in Practice E821.
surface of the target to the point at which the particle comes to
rest. 5. Apparatus
3.2.7 stopping power (or stopping cross section), n—the
5.1 Accelerator—The major item is the accelerator, which
energy lost per unit path length due to a particular process;
in size and complexity dwarfs any associated equipment.
usually expressed in differential form as−dE/dx.
Therefore, it is most likely that irradiations will be performed
at a limited number of sites where accelerators are available (a
3.2.8 straggling, n—the statistical fluctuation due to atomic
1-MeV electron microscope may also be considered an accel-
or electronic scattering of some quantity such as particle range
erator).
or particle energy at a given depth.
5.2 Fixtures for holding specimens during irradiation are
3.3 Symbols:
generally custom-made as are devices to measure and control
3.3.1 A,Z —the atomic weight and the number of the
1 1
particle energy, particle flux, and specimen temperature. Deci-
bombarding ion.
sions regarding apparatus are therefore left to individual
A,Z —the atomic weight and number of the atoms of the
2 2
workerswiththerequestthataccuratedataontheperformance
medium undergoing irradiation.
of their equipment be reported with their results.
depa—damage energy per atom; a unit of radiation expo-
sure. It can be expressed as the product of σ¯ and the fluence.
de
6. Composition of Specimen
dpa—displacements per atom; a unit of radiation exposure
giving the mean number of times an atom is displaced from its 6.1 An elemental analysis of stock from which specimens
lattice site. It can be expressed as the product of σ¯ and the
are fabricated should be known. The manufacturer’s heat
d
fluence. number and analysis are usually sufficient in the case of
heavy ion—used here to denote an ion of mass >4.
commercally produced metals. Additional analysis should be
light ion—an arbitrary designation used here for conve-
performed after other steps in the experimental procedure if
nience to denote an ion of mass ≤4.
there is cause to believe that the composition of the specimen
T —an effective value of the energy required to displace an
may have been altered. It is desirable that uncertainties in the
d
atom from its lattice site.
analyses be stated and that an atomic basis be reported in
σ (E)—an energy-dependent displacement cross section; σ¯
addition to a weight basis.
d d
denotes a spectrum-averaged value. Usual unit is barns.
σ (E)—an energy-dependent damage energy cross section; 7. Preirradiation Heat Treatment of Specimen
de
σ¯ denotes a spectrum-averaged value. Usual unit is barns-eV
de
7.1 Temperature and time of heat treatments should be well
or barns-keV.
controlled and reported. This applies to intermediate anneals
during fabrication, especially if a metal specimen is to be
4. Significance and Use
irradiated in the cold-worked condition, and it also applies to
4.1 A characteristic advantage of charged-particle irradia- operations where specimens are bonded to metal holders by
tionexperimentsisprecise,individual,controlovermostofthe diffusion or by brazing. The cooling rate between annealing
E521 − 96 (2009)
steps and between the final annealing temperature and room somecases,thismeansthattheexaminationshouldbedoneon
temperature should also be controlled and reported. specimens that were mounted for irradiation and then un-
mounted without being irradiated. The microstructure should
7.2 The environment of the specimen during heat treatment
be described in terms of grain size, phases, precipitates,
should be reported. This includes description of container,
dislocations, and inclusions.
measureofvacuum,presenceofgases(flowingorsteady),and
the presence of impurity absorbers such as metal sponge.Any 9.2 Asectionofarepresentativespecimencutparalleltothe
discoloration of specimens following an anneal should be particle beam should be examined by light microscopy.Atten-
reported. tion should be devoted to the microstructure within a distance
from the incident surface equal to the range of the particle, as
7.3 High-temperature annealing of metals and alloys from
well as to the flatness of the surface.
Groups IV, V, and VI frequently results in changes, both
positive and negative, in their interstitial impurity content.
10. Surface Condition of Specimen
Since the impurity content may have a significant influence on
10.1 The surface of the specimen should be clean and flat.
void formation, an analysis of the specimen or of a companion
Details of its preparation should be reported. Electropolishing
piecepriortoirradiationshouldbeperformed.Othersituations,
of metallic specimens is a convenient way of achieving these
such as selective vaporization of alloy constituents during
objectives in a single operation. The possibility that hydrogen
annealing, would also require a final analysis.
is absorbed by the specimen during electropolishing should be
7.4 The need for care with regard to alterations in compo-
investigated by analyses of polished and nonpolished speci-
sition is magnified by the nature of the specimens. They are
mens. Deviations in the surface form the perfect-planar condi-
usually very thin with a high exposed surface-to-volume ratio.
tion should not exceed, in dimension perpendicular to the
Information is obtained from regions whose distance from the
plane, 10% of the expected particle range in the specimen.
surface may be small relative to atomic diffusion distances.
10.2 The specimen may be irradiated in a mechanically
polished condition provided damage produced by polishing
8. Plastic Deformation of Specimen
does not extend into the region of postirradiation examination.
8.1 When plastic deformation is a variable in radiation
damage, care must be taken in the geometrical measurements
11. Dimension of Specimen Parallel to Particle Beam
used to compute the degree of deformation. The variations in
11.1 Specimens without support should be thick enough to
dimensions of the larger piece from which specimens are cut
resist deformation during handling. If a disk having a diameter
should be measured and reported to such a precision that a
of 3 mm is used, its thickness should be greater than 0.1 mm.
standard deviation in the degree of plastic deformation can be
assigned to the specimens. A measuring device more accurate 11.2 Supportedspecimensmaybeconsiderablythinnerthan
and precise than the common hand micrometer will probably
unsupported specimens. The minimum thickness should be at
be necessary due to the thinness of specimens commonly least fourfold greater than the distance below any surface from
irradiated.
which significant amounts of radiation-produced defects could
escape.Thisdistancecansometimesbeobservedasavoid-free
8.2 The term cold-worked should not stand alone as a
zone near the free surface of an irradiated specimen.
description of state of deformation. Every effort should be
made to characterize completely the deformation. The param-
12. Helium
eters which should be stated are: (1) deformation process (for
12.1 Injection:
example, simple tension or compression, swaging, rolling,
12.1.1 Alpha-particle irradiation is frequently used to inject
rolling with applied tension); (2) total extent of deformation,
helium into specimens to simulate the production of helium
expressed in terms of the principal orthogonal natural strain
during neutron irradiations where helium is produced by
components(ε , ε , ε )orthegeometricshapechangesthatwill
1 2 3
transmutation reactions. Helium injection may be completed
allow the reader to compute the strains; (3) procedure used to
before particle irradiation begins. It may also proceed incre-
reach the total strain level (for example, number of rolling
mentally during interruptions in the particle irradiation or it
passes and reductions in each); (4) strain rate; and (5) defor-
may proceed simultaneously with particle irradiation. The last
mation temperature, including an estimate of temperature
case is the most desirable as it gives the closest simulation to
changes caused by adiabatic work.
neutron irradiation. Some techniques for introducing helium
8.2.1 Many commonly used deformation processes (for
are set forth in Guide E942.
example, rolling and swaging) tend to be nonhomogeneous. In
12.1.2 The influence of implantation temperature on helium
suc
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