ASTM E170-2008d 516 Standard Terminology Relating to Radiation Measurements and Dosimetry.pdf

1、Designation: E 170 08dStandard 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 () 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 e

3、ffects, 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 term

4、s 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 quan

5、tities, with units, for radiationmeasurements as contained in the International Commission on Radiation Units and Measurements(ICRU) Report 60 on “Fundamental Quantities and Units for Ionizing Radiation,” December 30,1998.2Those terms that are defined essentially according to the terminology of ICRU

6、 Report 60 willbe followed by ICRU in parentheses. It should also be noted that the units for quantities used are thelatest adopted according to the International System of Units (SI) which are contained inAppendix X1as taken from a table in ICRU Report 33.2This terminology also uses recommended def

7、initions of twoISO documents3, namely “International Vocabulary of Basic and General Terms in Metrology.” (VIM,1993) and “Guide to the Expression of Uncertainty in Measurement” (GUM, 1995). Those terms thatare defined essentially according to the terminology of these documents will be followed by ei

8、therVIM or GUM in parentheses.1. Referenced Documents1.1 ASTM Standards:4E 380 Practice for the Use of the International System ofUnits (SI) (The Modernized Metric System)5E 456 Terminology Relating to Quality and StatisticsE 706 Master Matrix for Light-Water Reactor PressureVessel Surveillance Stan

9、dards, E 706(0)E 722 Practice for Characterizing Neutron Energy FluenceSpectra in Terms of an Equivalent Monoenergetic NeutronFluence for Radiation-Hardness Testing of ElectronicsE 910 Test Method for Application and Analysis of HeliumAccumulation Fluence Monitors for Reactor Vessel Sur-veillance, E

10、706 (IIIC)1.2 ISO Standards:3GUM Guide to the Expression of Uncertainty in Measure-ment, ISO 1995VIM International Vocabulary of Basic and General Termsin Metrology, ISO 19931.3 ICRU Documents:2ICRU 33 Radiation Quantities and UnitsICRU 60 Fundamental Quantities and Units for IonizingRadiation, Dece

11、mber 30, 19981This 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 Nov. 1, 2008. Published December 2008. Originallyapproved in 1963. Last previous edition ap

12、proved in 2008 as E 170 08b.2ICRU Report 33 has been superceded by ICRU Report 60 on “FundamentalQuantities and Units for Ionizing Radiation,” December 30, 1998. Both of thesedocuments are available from International Commission on Radiation Units andMeasurements (ICRU), 7910 Woodmont Ave., Suite 80

13、0, Bethesda, MD 20814.3Available from International Organization for Standardization (ISO), 1 Rue deVarembe, Case Postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.4For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. Fo

14、r Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.5Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1.4 NIST Document:6NIST Technical Note 1297 Guidelines for

15、Evaluating andExpressing the Uncertainty of NIST Measurement Re-sults, 19942. 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 kilo

16、gram of the specifiedmaterial (1 Gy = 1 J/kg). The mathematical relationship isthe quotient of d by dm, where d is the mean incrementalenergy imparted by ionizing radiation to matter of incremen-tal mass dm. (ICRU)D 5 d/dm (1)DISCUSSION The discontinued unit for absorbed dose is the rad(1 rad = 100

17、erg/g = 0.01 Gy). Absorbed dose is sometimes referred tosimply as 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 =

18、mass energy absorption coefficient (m2/kg).If bremsstrahlung production within the specified material isnegligible, 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 particleequilibrium exi

19、sts.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 example, in u

20、nits 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 radioactive

21、 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 becquerel(Bq).1

22、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 to the produ

23、ct 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 used in a

24、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 electron (

25、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 lowerenergy).

26、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 forreactor dosimet

27、ry has been made:7controlled 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 butaccepted as

28、 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 be verifie

29、d 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 uncollidedradiation reachin

30、g 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 spatiallocatio

31、n.6Available from National Institute of Standards and Technology (NIST), 100Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, USA, http:/www.nist.gov7Neutron Cross Sections for Reactor Dosimetry, International Atomic EnergyAgency, Laboratory Activities, Vienna, 1978, Vol 1, p. 62.E 170 08d2DISCUSS

32、IONIn 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 instrument, both havi

33、ng 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-ray standard field.ca

34、lorimeteran 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 been char-acterized

35、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 obtained byone of the foll

36、owing 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 knowledgeable with the mater

37、ials being tested. Thecertified reference materials provided by the United States NationalInstitute of Standards and Technology are called Standard ReferenceMaterials.charged particle equilibriuma condition that exists in anincremental volume within a material under irradiation if thekinetic energie

38、s and number of charged particles (of eachtype) entering that volume are equal to those leaving thatvolume.DISCUSSIONWhen electrons are the predominatnt charged particle,the term “electron equilibrium” is often used to describe chargedparticle equilibrium. See also the discussions attached to the de

39、finitionsof kerma and absorbed dose in E 170.coincidence sum peaka peak in the observed photon spec-trum produced at an energy corresponding 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 ti

40、me of the detector.Compton edge (Ec)the maximum energy value of electronsof the Compton scattering continuum. The energy value ofthe Compton 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.

41、Compton scatteringelastic scattering of a photon by anatomic electron, under the condition of conservation ofmomentum, that is, the vector 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 c

42、osu!0.511(8)where Egis the incident photon energy in MeV and u is theangle between the direction of the primary and scatteredphoton. The electron energy, Ee, is equal to Eg E8g.continuumthe smooth distribution of energy deposited in agamma detector arising from partial energy absorption fromCompton

43、scattering or other processes (for example,Bremsstrahlung). See Compton scattering.cross section, sthe quotient of P by F, where P is theprobability 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,

44、 b.1b5 10228m2(10)decay constant, lof a radioactive nuclide in a particularenergy state, the quotient of dP by dt, where dP is theprobability of a given nucleus undergoing a spontaneousnuclear transition from that energy state in the time intervaldt (ICRU).l5dP/d t (11)Unit: s1DISCUSSIONThe quantity

45、 (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 radioactive nuclide to become half its initial value.depth-dose distributionvariation of absorbed dose withdepth from the incident surface of a material exposed to agi

46、ven radiation.displacement dose (Dd)the quotient of d dby dm, where ddis that part of the mean energy imparted by radiation tomatter which produces atomic displacements (that is, ex-cluding the part that produces ionization and excitation ofelectrons) in a volume element of mass dm.Dd5 d d/dm (12)Un

47、it:Jkg1DISCUSSIONA more common unit is displacements per atom(dpa), (see definition).displacements per atom (dpa)the mean number of timeseach atom of a solid is displaced from its lattice site duringan exposure to displacing radiation, as calculated followingstandard procedures (see displacement dos

48、e).dosimetera device that, when irradiated, exhibits a quanti-fiable change that can be related to absorbed dose in a givenmaterial using appropriate measurement instrument(s) andprocedures.dosimetry systema system used for determining absorbeddose, consisting of dosimeters, measurement instrumentsE

49、 170 08d3and their associated reference standards, and procedures forthe systems use.effective cadmium cut-off energy (Ec)the energy at whicha specified 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 with cadmium thickness, geometry of thecontainer, angular di