1、Designation: E 521 96 (Reapproved 2003)Standard Practice forNeutron Radiation Damage Simulation by Charged-ParticleIrradiation1This standard is issued under the fixed designation E 521; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisio
2、n, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONThis practice is intended to provide the nuclear research community with recommended proceduresfor the
3、 simulation of neutron radiation damage by charged-particle irradiation. It recognizes thediversity of energetic-ion producing devices, the complexities in experimental procedures, and thedifficulties in correlating the experimental results with those produced by reactor neutron irradiation.Such res
4、ults may be used to estimate density changes and the changes in microstructure that wouldbe caused by neutron irradiation. The information can also be useful in elucidating fundamentalmechanisms of radiation damage in reactor materials.1. Scope1.1 This practice provides guidance on performing charge
5、d-particle irradiations of metals and alloys. It is generallyconfined to studies of microstructural and microchemicalchanges carried out with ions of low-penetrating power thatcome to rest in the specimen. Density changes can be measureddirectly and changes in other properties can be inferred. Thisi
6、nformation can be used to estimate similar changes that wouldresult from neutron irradiation. More generally, this informa-tion is of value in deducing the fundamental mechanisms ofradiation damage for a wide range of materials and irradiationconditions.1.2 The word simulation is used here in a broa
7、d sense toimply an approximation of the relevant neutron irradiationenvironment. The degree of conformity can range from poor tonearly exact. The intent is to produce a correspondencebetween one or more aspects of the neutron and chargedparticle irradiations such that fundamental relationships arees
8、tablished between irradiation or material parameters and thematerial response.1.3 The practice appears as follows:SectionApparatus 4Specimen Preparation 5-10Irradiation Techniques (including Helium Injection) 1112Damage Calculations 13Postirradiation Examination 14-16Reporting of Results 17Correlati
9、on and Interpretation 18-221.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations p
10、rior to use.2. Referenced Documents2.1 ASTM Standards:C 859 Terminology Relating to Nuclear Materials2E 798 Practice for Conducting Irradiations at Accelerator-Based Neutron Sources3E 821 Practice for Measurement of Mechanical PropertiesDuring Charged-Particle Irradiation2E 910 Test Method for Appli
11、cation and Analysis of HeliumAccumulation Fluence Monitors for Reactor Vessel Sur-veillance, E706 (IIIC)2E 942 Guide for Simulation of Helium Effects in IrradiatedMetals23. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 Descriptions of relevant terms are found in Terminol-ogy C
12、859 and Terminology E 170.3.2 Definitions:3.2.1 damage energy, nthat portion of the energy lost byan ion moving through a solid that is transferred as kineticenergy to atoms of the medium; strictly speaking, the energy1This practice is under the jurisdiction of ASTM Committee E10 on NuclearTechnolog
13、y and Applications and is the direct responsibility of SubcommitteeE10.08 on Procedures for Neutron Radiation Damage Simulation.Current edition approved Jan. 10, 1996. Published March 1996. Originallypublished as E 521 76. Last previous edition E 521 89.2Annual Book of ASTM Standards, Vol 12.01.3Ann
14、ual Book of ASTM Standards, Vol 12.02.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.transfer in a single encounter must exceed the energy requiredto displace an atom from its lattice cite.3.2.2 displacement, nthe process of dislodg
15、ing an atomfrom its normal site in the lattice.3.2.3 path length, nthe total length of path measuredalong the actual path of the particle.3.2.4 penetration depth, na projection of the range alongthe normal to the entry face of the target.3.2.5 projected range, nthe projection of the range alongthe d
16、irection of the incidence ion prior to entering the target.3.2.6 range, nthe distance from the point of entry at thesurface of the target to the point at which the particle comes torest.3.2.7 stopping power (or stopping cross section), ntheenergy lost per unit path length due to a particular process
17、;usually expressed in differential form as dE/dx.3.2.8 straggling, nthe statistical fluctuation due to atomicor electronic scattering of some quantity such as particle rangeor particle energy at a given depth.3.3 Symbols:Symbols:A1,Z1the atomic weight and the number of the bombard-ing ion.A2,Z2the a
18、tomic weight and number of the atoms of themedium undergoing irradiation.depadamage energy per atom; a unit of radiation expo-sure. It can be expressed as the product of sdeand the fluence.dpadisplacements per atom; a unit of radiation exposuregiving the mean number of times an atom is displaced fro
19、m itslattice site. It can be expressed as the product of sdand thefluence.heavy ionused here to denote an ion of mass 4.light ionan arbitrary designation used here for conve-nience to denote an ion of mass #4.Tdan effective value of the energy required to displace anatom from its lattice site.sd(E)a
20、n energy-dependent displacement cross section; sddenotes a spectrum-averaged value. Usual unit is barns.sde(E)an energy-dependent damage energy cross section;sdedenotes a spectrum-averaged value. Usual unit is barns-eVor barns-keV.4. Significance and Use4.1 A characteristic advantage of charged-part
21、icle irradia-tion experiments is precise, individual, control over most of theimportant irradiation conditions such as dose, dose rate,temperature, and quantity of gases present. Additional at-tributes are the lack of induced radioactivation of specimensand, in general, a substantial compression of
22、irradiation time,from years to hours, to achieve comparable damage as mea-sured in displacements per atom (dpa). An important applica-tion of such experiments is the investigation of radiation effectsin not-yet-existing environments, such as fusion reactors.4.2 The primary shortcoming of ion bombard
23、ments stemsfrom the damage rate, or temperature dependences of themicrostructural evolutionary processes in complex alloys, orboth. It cannot be assumed that the time scale for damageevolution can be comparably compressed for all processes byincreasing the displacement rate, even with a correspondin
24、gshift in irradiation temperature. In addition, the confinement ofdamage production to a thin layer just (often ; 1 m) belowthe irradiated surface can present substantial complications. Itmust be emphasized, therefore, that these experiments and thispractice are intended for research purposes and no
25、t for thecertification or the qualification of equipment.4.3 This practice relates to the generation of irradiation-induced changes in the microstructure of metals and alloysusing charged particles. The investigation of mechanical be-havior using charged particles is covered in Practice E 821.5. App
26、aratus5.1 AcceleratorThe major item is the accelerator, whichin size and complexity dwarfs any associated equipment.Therefore, it is most likely that irradiations will be performedat a limited number of sites where accelerators are available (a1-MeV electron microscope may also be considered an acce
27、l-erator).5.2 Fixtures for holding specimens during irradiation aregenerally custom-made as are devices to measure and controlparticle energy, particle flux, and specimen temperature. Deci-sions regarding apparatus are therefore left to individualworkers with the request that accurate data on the pe
28、rformanceof their equipment be reported with their results.6. Composition of Specimen6.1 An elemental analysis of stock from which specimensare fabricated should be known. The manufacturers heatnumber and analysis are usually sufficient in the case ofcommercally produced metals. Additional analysis
29、should beperformed after other steps in the experimental procedure ifthere is cause to believe that the composition of the specimenmay have been altered. It is desirable that uncertainties in theanalyses be stated and that an atomic basis be reported inaddition to a weight basis.7. Preirradiation He
30、at Treatment of Specimen7.1 Temperature and time of heat treatments should be wellcontrolled and reported. This applies to intermediate annealsduring fabrication, especially if a metal specimen is to beirradiated in the cold-worked condition, and it also applies tooperations where specimens are bond
31、ed to metal holders bydiffusion or by brazing. The cooling rate between annealingsteps and between the final annealing temperature and roomtemperature should also be controlled and reported.7.2 The environment of the specimen during heat treatmentshould be reported. This includes description of cont
32、ainer,measure of vacuum, presence of gases (flowing or steady), andthe presence of impurity absorbers such as metal sponge. Anydiscoloration of specimens following an anneal should bereported.7.3 High-temperature annealing of metals and alloys fromGroups IV, V, and VI frequently results in changes,
33、bothpositive and negative, in their interstitial impurity content.Since the impurity content may have a significant influence onvoid formation, an analysis of the specimen or of a companionpiece prior to irradiation should be performed. Other situations,such as selective vaporization of alloy consti
34、tuents duringannealing, would also require a final analysis.E 521 96 (2003)27.4 The need for care with regard to alterations in compo-sition is magnified by the nature of the specimens. They areusually very thin with a high exposed surface-to-volume ratio.Information is obtained from regions whose d
35、istance from thesurface may be small relative to atomic diffusion distances.8. Plastic Deformation of Specimen8.1 When plastic deformation is a variable in radiationdamage, care must be taken in the geometrical measurementsused to compute the degree of deformation. The variations indimensions of the
36、 larger piece from which specimens are cutshould be measured and reported to such a precision that astandard deviation in the degree of plastic deformation can beassigned to the specimens. A measuring device more accurateand precise than the common hand micrometer will probablybe necessary due to th
37、e thinness of specimens commonlyirradiated.8.2 The term cold-worked should not stand alone as adescription of state of deformation. Every effort should bemade to characterize completely the deformation. The param-eters which should be stated are: (1) deformation process (forexample, simple tension o
38、r compression, swaging, rolling,rolling with applied tension); (2) total extent of deformation,expressed in terms of the principal orthogonal natural straincomponents (e1, e2, e3) or the geometric shape changes thatwill allow the reader to compute the strains; (3) procedure usedto reach the total st
39、rain level (for example, number of rollingpasses and reductions in each); (4) strain rate; and (5) defor-mation temperature, including an estimate of temperaturechanges caused by adiabatic work.8.2.1 Many commonly used deformation processes (forexample, rolling and swaging) tend to be nonhomogeneous
40、. Insuch cases the strain for each pass can be best stated by thedimensions in the principal working directions before and aftereach pass. The strain rate can then be specified sufficiently bystating the deformation time of each pass.9. Preirradiation Metallography of Specimen9.1 A general examinati
41、on by light microscopy andtransmission-electron microscopy should be performed on thespecimen in the condition in which it will be irradiated. Insome cases, this means that the examination should be done onspecimens that were mounted for irradiation and then un-mounted without being irradiated. The
42、microstructure shouldbe described in terms of grain size, phases, precipitates,dislocations, and inclusions.9.2 A section of a representative specimen cut parallel to theparticle beam should be examined by light microscopy. Atten-tion should be devoted to the microstructure within a distancefrom the
43、 incident surface equal to the range of the particle, aswell as to the flatness of the surface.10. Surface Condition of Specimen10.1 The surface of the specimen should be clean and flat.Details of its preparation should be reported. Electropolishingof metallic specimens is a convenient way of achiev
44、ing theseobjectives in a single operation. The possibility that hydrogenis absorbed by the specimen during electropolishing should beinvestigated by analyses of polished and nonpolished speci-mens. Deviations in the surface form the perfect-planar condi-tion should not exceed, in dimension perpendic
45、ular to theplane, 10 % of the expected particle range in the specimen.10.2 The specimen may be irradiated in a mechanicallypolished condition provided damage produced by polishingdoes not extend into the region of postirradiation examination.11. Dimension of Specimen Parallel to Particle Beam11.1 Sp
46、ecimens without support should be thick enough toresist deformation during handling. If a disk having a diameterof 3 mm is used, its thickness should be greater than 0.1 mm.11.2 Supported specimens may be considerably thinner thanunsupported specimens. The minimum thickness should be atleast fourfol
47、d greater than the distance below any surface fromwhich significant amounts of radiation-produced defects couldescape. This distance can sometimes be observed as a void-freezone near the free surface of an irradiated specimen.12. Helium12.1 Injection:12.1.1 Alpha-particle irradiation is frequently u
48、sed to injecthelium into specimens to simulate the production of heliumduring neutron irradiations where helium is produced bytransmutation reactions. Helium injection may be completedbefore particle irradiation begins. It may also proceed incre-mentally during interruptions in the particle irradiat
49、ion or itmay proceed simultaneously with particle irradiation. The lastcase is the most desirable as it gives the closest simulation toneutron irradiation. Some techniques for introducing heliumare set forth in Guide E 942.12.1.2 The influence of implantation temperature on heliumdistribution (that is, dispersed atomistically, in small clusters,in bubbles, etc.) is known to be important. The consequences ofthe choice of injection temperature on the simulation should beevaluated and reported.12.2 Analysis and Distribution:12.2.1 Analysis of the concentration
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