ASTM E170-2008a 459 Standard Terminology Relating to Radiation Measurements and Dosimetry.pdf

1、Designation: E 170 08aStandard Terminology Relating toRadiation Measurements and Dosimetry1This standard is issued under the fixed designation E 170; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A numb

2、er in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONThis terminology generally covers terms that apply to radiation measurements and dosimetryassociated with energy deposition and radiation

3、effects, or damage, in materials caused by interactionsby high-energy radiation fields. The common radiation fields considered are X-rays, gamma rays,electrons, alpha particles, neutrons, and mixtures of these fields. This treatment is not intended to beexhaustive but reflects special and common ter

4、ms used in technology and applications of interest toCommittee E10, as for example, in areas of radiation effects on components of nuclear power reactors,radiation hardness testing of electronics, and radiation processing of materials.This terminology uses recommended definitions and concepts of qua

5、ntities, with units, for radiationmeasurements as contained in the International Commission on Radiation Units and Measurements(ICRU) Report 33 on “Radiation Quantities and Units,” April 15, 1980.2Those terms that are definedessentially according to the terminology of ICRU Report 33 will be followed

6、 by ICRU in parentheses.It should also be noted that the units for quantities used are the latest adopted according to theInternational System of Units (SI).1. Referenced Documents1.1 ASTM Standards:3E 380 Practice for the Use of the International System ofUnits (SI) (The Modernized Metric System)4E

7、 456 Terminology Relating to Quality and StatisticsE 706 Master Matrix for Light-Water Reactor PressureVessel Surveillance Standards, E 706(0)E 722 Practice for Characterizing Neutron Energy FluenceSpectra in Terms of an Equivalent Monoenergetic NeutronFluence for Radiation-Hardness Testing of Elect

8、ronicsE 910 Test Method for Application and Analysis of HeliumAccumulation Fluence Monitors for Reactor Vessel Sur-veillance, E706 (IIIC)1.2 ISO Standards:5GUM Guide to the Expression of Uncertainty in Measure-ment, ISO 1995VIM International Vocabulary of Basic and General Termsin Metrology, ISO 199

9、32. Terminologyabsorbed dose (D)Quantity of ionizing radiation energyimparted per unit mass of a specified material. The SI unit ofabsorbed dose is the gray (Gy), where 1 gray is equivalent tothe absorption of 1 joule per kilogram of the specifiedmaterial (1 Gy = 1 J/kg). The mathematical relationsh

10、ip isthe quotient of de by dm, where de is the mean incrementalenergy imparted by ionizing radiation to matter of incremen-tal mass dm (see ICRU 33).D 5 de/dm (1)DISCUSSION The discontinued unit for absorbed dose is the rad (1rad = 100 erg/g = 0.01 Gy). Absorbed dose is sometimes referred tosimply a

11、s dose. For a photon source under conditions of chargedparticle equilibrium, the absorbed dose, D, may be expressed asfollows:D 5F E en/r, (2)where:F = particle fluence (particles/m2),E = energy of the ionizing radiation (J), anden/r = mass energy absorption coefficient (m2/kg).If bremsstrahlung pro

12、duction within the specified material is1This terminology is under the jurisdiction ofASTM Committee E10 on NuclearTechnology and Applications and is the direct responsibility of SubcommitteeE10.93 on Editorial.Current edition approved April 1, 2008. Published April 2008. Originallyapproved in 1963.

13、 Last previous edition approved in 2008 as E 170 08.2Available from International Commission on Radiation Units and Measure-ments (ICRU), 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service

14、astm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Withdrawn.5Available from International Organization for Standardization (ISO), 1, ch. dela Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.

15、1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.negligible, the mass energy absorption coefficient (en/r)isequal to the mass energy transfer coefficient (tr/r), andabsorbed dose is equal to kerma if, in addition, charged particleequi

16、librium exists.absorbed dose rate, Dthe absorbed dose in a material perincremental time interval, that is, the quotient of d D by d t(see ICRU Report 33).D5 dD/dt (3)SI unit: Gys1.DISCUSSIONThe absorbed-dose rate is often specified in terms of theaverage value of D over longer time intervals, for ex

17、ample, in units ofGymin1or Gyh1.accuracythe closeness of agreement between a measure-ment result and an accepted reference value (see Terminol-ogy E 456).activation cross sectionthe cross section for processes inwhich the product nucleus is radioactive (see cross section).activity, Aof an amount of

18、radioactive nuclide in a particularenergy state at a given time, the quotient of dN by dt, wheredN is the expectation value of the number of spontaneousnuclear transitions from that energy state in the time intervaldt (ICRU).A 5 dN/dt (4)Unit: s1The special name for the unit of activity is the becqu

19、erel(Bq).1 Bq 5 1s21(5)DISCUSSIONThe former special unit of activity was the curie (Ci).1 Ci 5 3.7 3 1010s21exactly!. (6)The “particular energy state” is the ground state of the nuclide unlessotherwise specified. The activity of an amount of radioactive nuclide in aparticular energy state is equal t

20、o the product of the decay constant for thatstate and the number of nuclei in that state (that is, A=Nl). (See decayconstant.)analysis bandwidthspectral band used in a photometricinstrument, such as a densitometer, for the measurement ofoptical absorbance or reflectance.analysis wavelengthwavelength

21、 used in a spectrophotomet-ric instrument for the measurement of optical absorbance orreflectance.annihilation radiationgamma radiation produced by theannihilation of a positron and an electron. For particles atrest, two photons are produced, each having an energycorresponding to the rest mass of an

22、 electron (511 keV).backscatter peaka peak in the observed photon spectrum(normally below about 0.25 MeV) resulting from large-angle(110) Compton scattering of gamma rays from materialsnear the detector. This peak will not have the same shape asthe full-energy peaks (being wider and skewed toward lo

23、werenergy).benchmark neutron fielda well-characterized neutron fieldwhich will provide a fluence of neutrons for validation orcalibration of experimental techniques and methods and forvalidation of cross sections and other nuclear data. Thefollowing classification of benchmark neutron fields forreac

24、tor dosimetry has been made:6controlled neutron fielda neutron field physically well-defined, and with some spectrum definition, employed for arestricted set of validation experiments.reference neutron fielda permanent and reproducible neu-tron field less well characterized than a standard field but

25、accepted as a measurement reference by a community ofusers.standard neutron fielda permanent and reproducible neu-tron field with neutron fluence rate and energy spectra, andtheir associated spatial and angular distributions character-ized to state-of-the-art accuracy. Important field quantitiesmust

26、 be verified by interlaboratory measurements and cal-culations.buildup factorfor radiation passing through a medium, theratio of the total value of a specified radiation quantity (suchas absorbed dose) at any point in that medium to thecontribution to that quantity from the incident uncollidedradiat

27、ion reaching that point.cadmium ratiothe ratio of the neutron reaction rate mea-sured with a given bare neutron detector to the neutronreaction rate measured with an identical neutron detectorenclosed by a particular cadmium cover and exposed in thesame neutron field at the same or an equivalent spa

28、tiallocation.DISCUSSIONIn practice, meaningful experimental values can beobtained in an isotropic neutron field by using a cadmium filterapproximately 1 mm thick.calibrated instrumentan instrument for which the responsehas been documented upon being directly compared with theresponse of a standard i

29、nstrument, both having been exposedto the same radiation field under the same conditions; or onefor which the response has been documented upon beingexposed to a standard radiation field under well-definedconditions.calibration source or fieldsee electron standard field,g-ray standard field, and X-r

30、ay standard field.calorimeteran instrument capable of making absolute mea-surements of energy deposition (or absorbed dose) in amaterial through measurement of its change in temperatureand a knowledge of the characteristics of its materialconstruction.certified reference materiala material that has

31、been char-acterized by a recognized standard or testing laboratory, forsome of its chemical or physical properties, and that isgenerally used for calibration of a measurement system, orfor development or evaluation of a measurement method.DISCUSSIONCertification of a reference material can be obtain

32、ed byone of the following three established routes of measurement ofproperties: (1) using a previously validated reference method; (2) usingtwo or more independent, reliable measurement methods; and (3) usingan ad hoc network of cooperating laboratories, technically competent,and thoroughly knowledg

33、eable with the materials being tested. The6Neutron Cross Sections for Reactor Dosimetry, International Atomic EnergyAgency, Laboratory Activities, Vienna, 1978, Vol 1, p. 62.E 170 08a2certified reference materials provided by the United States NationalInstitute of Standards and Technology are called

34、 Standard ReferenceMaterials.charged particle equilibriuma condition that exists in anincremental volume within a material under irradiation if thekinetic energies and number of charged particles (of eachtype) entering that volume are equal to those leaving thatvolume.DISCUSSIONWhen electrons are th

35、e predominatnt charged particle,the term “electron equilibrium” is often used to describe chargedparticle equilibrium. See also the discussions attached to the definitionsof kerma and absorbed dose in E 170.coincidence sum peaka peak in the observed photon spec-trum produced at an energy correspondi

36、ng to the sum of theenergies of two or more gamma- or x-rays from a singlenuclear event when the emitted photons interact with thedetector within the resolving time of the detector.Compton edge (Ec)the maximum energy value of electronsof the Compton scattering continuum. The energy value ofthe Compt

37、on edge isEc5 Eg2Eg1 12Eg0.511(7)which corresponds to 180 scattering of the primary photonof energy Eg(MeV). For a 1 MeV photon, the Compton edgeis about 0.8 MeV.Compton scatteringelastic scattering of a photon by anatomic electron, under the condition of conservation ofmomentum, that is, the vector

38、 sum of the momenta of theoutgoing electron and photon is equal to the momentum ofthe incident photon. The scattered photon energy, E8g,isgiven byE8g5Eg1 1Eg1 2 cosu!0.511(8)where Egis the incident photon energy in MeV and u is theangle between the direction of the primary and scatteredphoton. The e

39、lectron energy, Ee, is equal to Eg E8g.continuumthe smooth distribution of energy deposited in agamma detector arising from partial energy absorption fromCompton scattering or other processes (for example,Bremsstrahlung). See Compton scattering.cross section, sthe quotient of P by F, where P is thep

40、robability of the interaction for one target entity whensubjected to the particle fluence F (ICRU).s5P/F (9)Unit: m2The special unit of cross section is the barn, b.1b5 10228m2(10)decay constant, lof a radioactive nuclide in a particularenergy state, the quotient of dP by dt, where dP is theprobabil

41、ity of a given nucleus undergoing a spontaneousnuclear transition from that energy state in the time intervaldt (ICRU).l5dP/d t (11)Unit: s1DISCUSSIONThe quantity (ln 2)/l is commonly called the half-life,T12 , of the radioactive nuclide, that is, the time taken for the activityof an amount of radio

42、active nuclide to become half its initial value.depth-dose distributionvariation of absorbed dose withdepth from the incident surface of a material exposed to agiven radiation.displacement dose (Dd)the quotient of d edby dm, where dedis that part of the mean energy imparted by radiation tomatter whi

43、ch produces atomic displacements (that is, ex-cluding the part that produces ionization and excitation ofelectrons) in a volume element of mass dm.Dd5 d ed/dm (12)Unit:Jkg1DISCUSSIONA more common unit is displacements per atom(dpa), (see definition).displacements per atom (dpa)the mean number of tim

44、eseach atom of a solid is displaced from its lattice site duringan exposure to displacing radiation, as calculated followingstandard procedures (see displacement dose).dosimetera device that, when irradiated, exhibits a quanti-fiable change that can be related to absorbed dose in a givenmaterial usi

45、ng appropriate measurement instruments andprocedures.dosimetry systema system used for determining absorbeddose, consisting of dosimeters, measurement instrumentsand their associated reference standards, and procedures forthe systems use.effective cadmium cut-off energy (Ec)the energy at whicha spec

46、ified cadmium container performs like a theoreticallyperfect filter and, therefore, has the following properties:(1) for all energies below Ec, no neutron reactions occur,and(2) for all energies above Ec, neutron reactions occur at thesame rate as if the cadmium were not present.DISCUSSIONEcvaries w

47、ith cadmium thickness, geometry of thecontainer, angular distribution of incident neutrons, and ambienttemperature.effciencysee total efficiency and full-energy peak effi-ciency.electron equilibriumcharged-particle equilibrium for elec-trons.electron standard fieldan electron field whose particleene

48、rgy and direction, spatial uniformity, and particle fluencerate uniformity are well established and reproducible.energy calibrationa process of establishing the relationshipbetween photon or particle energy and channel number in thespectrometer. The energy calibration may be as simple asbuilding a t

49、able of two or more energy-channel pairs or ascomplex as using a least squares algorithm to establish afunction describing the energy versus channel relationship.epithermal neutronsa general classification of neutronswith energies above those of thermal neutrons; or frequently,E 170 08a3neutrons with energies in the resonance range, between thethermal limit and some upper limit, such as 0.1 MeV (seethermal neutrons).DISCUSSIONThe term “epithermal neutrons” is generally used inthermal neutron systems wh