ASTM E666-97

Standard Practice for Calculating Absorbed Dose From Gamma or X Radiation

SCOPE
1.1 This practice presents a technique for calculating the absorbed dose in a material from knowledge of the radiation field, the composition of the material, (1)    and a related measurement. The procedure is applicable for X and gamma radiation provided the energy of the photons fall within the range from 0.01 to 20 MeV.  
1.2 A method is given for calculating the absorbed dose in a material from the knowledge of the absorbed dose in another material exposed to the same radiation field. The procedure is restricted to homogeneous materials composed of the elements for which absorption coefficients have been tabulated (2). It also requires some knowledge of the energy spectrum of the radiation field produced by the source under consideration. Generally, the accuracy of this method is limited by the accuracy to which the energy spectrum of the radiation field is known.
1.3 The results of this practice are only valid if charged particle equilibrium exists in the material and at the depth of interest. Thus, this practice is not applicable for determining absorbed dose in the immediate vicinity of boundaries between materials of widely differing atomic numbers. For more information on this topic, see Practice E1249.  
1.4 This practice does not consider dose "buildup" due to broad-beam geometry. Such "buildup" depends on the energy spectrum of the radiation field and the effective atomic number of the material. Correction can be made if buildup factors are included in the attenuation calculation. These factors have not been tabulated for a wide range of energies, geometries, and materials (3,4,5). However, this method has utility in providing a quick and relatively simple way of achieving useful approximate results.  
1.5 Energy transport computer codes  exist that are formulated to calculate absorbed dose in materials more precisely than this method. To use these codes, more effort, time, and expense are required. If the situation warrants, such calculations should be used rather than the method described here.  
1.6 This standard does not purport to address all of the safety problems, 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.

General Information

• Status: Historical
• Publication Date: 09-Jun-1997
• ICS: 17.240 - Radiation measurements
• Technical Committee: E10 - Nuclear Technology and Applications
• Drafting Committee: E10.07 - Radiation Dosimetry for Radiation Effects on Materials and Devices

Relations

• Replaced By: ASTM E666-03 - Standard Practice for Calculating Absorbed Dose From Gamma or X Radiation
• Effective Date: 10-Jul-2003
• Referred By: ASTM F1892-12(2018) - Standard Guide for Ionizing Radiation (Total Dose) Effects Testing of Semiconductor Devices
• Effective Date: 10-Jun-1997
• Referred By: ASTM F980-16 - Standard Guide for Measurement of Rapid Annealing of Neutron-Induced Displacement Damage in Silicon Semiconductor Devices
• Effective Date: 10-Jun-1997
• Referred By: ASTM ISO/ASTM51205-17 - Standard Practice for Use of a Ceric-Cerous Sulfate Dosimetry System
• Effective Date: 10-Jun-1997
• Referred By: ASTM D1879-06(2023) - Standard Practice for Exposure of Adhesive Specimens to Ionizing Radiation
• Effective Date: 10-Jun-1997
• Referred By: ASTM E2450-23 - Standard Practice for Application of CaF<inf>2</inf>(Mn) Thermoluminescence Dosimeters in Mixed Neutron-Photon Environments
• Effective Date: 10-Jun-1997
• Referred By: ASTM E1854-19 - Standard Practice for Ensuring Test Consistency in Neutron-Induced Displacement Damage of Electronic Parts
• Effective Date: 10-Jun-1997
• Referred By: ASTM E1161-21 - Standard Practice for Radiographic Examination of Semiconductors and Electronic Components
• Effective Date: 10-Jun-1997
• Referred By: ASTM F773M-16 - Standard Practice for Measuring Dose Rate Response of Linear Integrated Circuits (Metric) (Withdrawn 2023)
• Effective Date: 10-Jun-1997
• Referred By: ASTM E1819-15(2021) - Standard Guide for Environmental Monitoring Plans for Decommissioning of Nuclear Facilities
• Effective Date: 10-Jun-1997
• Referred By: ASTM F996-11(2018) - Standard Test Method for Separating an Ionizing Radiation-Induced MOSFET Threshold Voltage Shift Into Components Due to Oxide Trapped Holes and Interface States Using the Subthreshold Current&#x2013;Voltage Characteristics (Withdrawn 2023)
• Effective Date: 10-Jun-1997
• Referred By: ASTM F1467-18 - Standard Guide for Use of an X-Ray Tester (&#x2248;10 keV Photons) in Ionizing Radiation Effects Testing of Semiconductor Devices and Microcircuits
• Effective Date: 10-Jun-1997
• Referred By: ASTM F744M-16 - Standard Test Method for Measuring Dose Rate Threshold for Upset of Digital Integrated Circuits (Metric) (Withdrawn 2023)
• Effective Date: 10-Jun-1997
• Referred By: ASTM ISO/ASTM51538-17 - Standard Practice for Use of the Ethanol-Chlorobenzene Dosimetry System
• Effective Date: 10-Jun-1997
• Referred By: ASTM ISO/ASTM51401-13 - Standard Practice for Use of a Dichromate Dosimetry System
• Effective Date: 10-Jun-1997

Standards Content (Sample)

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.
Designation: E 666 – 97
Standard Practice for
Calculating Absorbed Dose From Gamma or X Radiation
This standard is issued under the fixed designation E 666; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
1.1 This practice presents a technique for calculating the
absorbed dose in a material from knowledge of the radiation
2. Referenced Documents
2,3
field, the composition of the material, (1-5) and a related
2.1 ASTM Standards:
measurement. The procedure is applicable for X and gamma
E 170 Terminology Relating to Radiation Measurements
radiation provided the energy of the photons fall within the
and Dosimetry
range from 0.01 to 20 MeV.
E 380 Practice for Use of the International System of Units
1.2 A method is given for calculating the absorbed dose in
(SI) (the Modernized Metric System)
a material from the knowledge of the absorbed dose in another
E 665 Practice for Determining Absorbed Dose Versus
material exposed to the same radiation field. The procedure is
Depth in Materials Exposed to the X-Ray Output of Flash
restricted to homogeneous materials composed of the elements
X-Ray Machines
for which absorption coefficients have been tabulated (2). It
E 668 Practice for Application of Thermoluminescence-
also requires some knowledge of the energy spectrum of the
Dosimetry (TLD) Systems for Determining Absorbed Dose
radiation field produced by the source under consideration.
in Radiation-Hardness Testing of Electronic Devices
Generally, the accuracy of this method is limited by the
E 1249 Practice for Minimizing Dosimetry Errors in Radia-
accuracy to which the energy spectrum of the radiation field is
tion Hardness Testing of Silicon Electronic Devices Using
known.
Co-60 Sources
1.3 The results of this practice are only valid if charged
2.2 International Commission on Radiation Units and
particle equilibrium exists in the material and at the depth of
Measurements (ICRU) Reports:
interest. Thus, this practice is not applicable for determining
ICRU Report 14—Radiation Dosimetry: X Rays and
absorbed dose in the immediate vicinity of boundaries between
Gamma Rays with Maximum Photon Energies Between
materials of widely differing atomic numbers. For more infor-
0.6 and 60 MeV
mation on this topic, see Practice E 1249.
4 ICRU Report 18—Specification of High Activity Gamma-
1.4 Energy transport computer codes exist that are formu-
Ray Sources
lated to calculate absorbed dose in materials more precisely
ICRU Report 21—Radiation Dosimetry: Electrons with Ini-
than this method. To use these codes, more effort, time, and
tial Energies Between 1 and 50 MeV
expense are required. If the situation warrants, such calcula-
ICRU Report 33—Radiation Quantities and Units
tions should be used rather than the method described here.
ICRU Report 34—The Dosimetry of Pulsed Radiation
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3. Significance and Use
responsibility of the user of this standard to establish appro-
3.1 The absorbed dose is a more meaningful parameter than
exposure for use in relating the effects of radiation on materi-
als. It expresses the energy absorbed by the irradiated material
This practice is under the jurisdiction of ASTM Committee E-10 on Nuclear
per unit mass, whereas exposure is related to the amount of
Technology and Applications and is the direct responsibility of Subcommittee
charge produced in air per unit mass. Absorbed dose, as
E 10.07 on Radiation Dosimetry for Radiation Effects on Materials and Devices.
Current edition approved June 10, 1997. Published May 1998.
referred to here, implies that the measurement is made under
The boldface numbers in parentheses refer to the list of references appended to
conditions of charged particle (electron) equilibrium (see
this practice.
Appendix X1). In practice, such conditions are not rigorously
For calculation of absorbed dose in biological materials such as tissue or bone,
etc., ICRU Report 14 provides more information and procedures for a more accurate
calculation than this practice.
Information on and packages of computer codes can be obtained from The
Radiation Safety Information Computational Center, Oak Ridge National Labora- Annual Book of ASTM Standards, Vol 12.02.
tory, P.O. Box 2008, Oak Ridge, TN 37831-6362. This information center collects, Annual Book of ASTM Standards, Vol 14.02.
organizes, evaluates, and disseminates shielding information related to radiation Available from International Commission on Radiation Units and Measure-
from reactors, weapons, and accelerators and to radiation occurring in space. ments (ICRU), 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814.
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 666
achievable but, under some circumstances, can be approxi- into energy intervals or bins. The width of these bins is
mated closely. somewhat flexible but should be chosen small enough so as not
3.2 Different materials, when exposed to the same radiation to distort the shape of the spectrum. For the purpose of
field, absorb different amounts of energy. In order to relate selecting appropriate values of μ (E)/r, the energy value
en
absorbed dose in one material to absorbed dose in another selected for each energy interval can be taken either as that
material, the condition of charged particle equilibrium must energy at the beginning or midpoint of each energy interval
exist. On the other hand, if the radiation is attenuated by a over the entire spectrum.
significant thickness of an absorber, the energy spectrum of the 4.4 The spectrum, c(E), is commonly given in arbitrary
radiation will be changed, and it will be necessary to correct for units and may be normalized to some source parameter. If a
this. standard or calibrated dosimeter is used, then the integral in Eq
1 must be calculated for the material from which this dosimeter
NOTE 1—For comprehensive discussions of various dosimetry methods
is constructed. The value of I is then given by the observed
applicable to the radiation types and energies and absorbed dose rate
dose, D, measured by the dosimeter divided by the value of the
ranges discussed in this method, see ICRU Reports 14, 21, and 34.
integral.
4. Calculation of Absorbed Dose
5. Estimating the Absorbed Dose in One Material from
4.1 The absorbed dose, D, at a point may be expressed as:
That Measured in Another Material
‘
D 5 I c~E!@μ ~E!/r#dE (1)
* en
0 5.1 If the absorbed dose is known in one material, A, then
the absorbed dose can be estimated in another material, B,
where c(E) is the energy fluence per unit energy at the point
using the method described in this section.
of interest; μ (E)/r is the mass energy absorption coefficient
en
5.1.1 The absorbed dose observed in A occurs at some depth
(2); and I is a normalizing factor. If all of the variables in Eq
in the region of material A; similarly, it is desired to know the
1 are expressed in SI units,I=1.In this case the units for D
–1 –2 2 –1
absorbed dose in material B at some depth in the region of
are Gy (J kg ), of c(E), are m ,ofμ /r are m kg , and of
en
material B. If it is presumed that we know the surface energy
E are J. For an alternative use of the normalizing factor I, see
fluence spectrum c (E) (the energy fluence spectrum incident
o
Appendix X2. For further information on the use of energy
on the surface of materials A and B) then the energy fluence
absorption coefficients to calculate absorbed dose see the
spectrum c(E) to be used in Eq 1 must be related to the known
discussion in Attix (1). The energy fluence spectrum, c(E), is
surface energy fluence spectrum c (E). A good approximation
that which is incident at the point where the dose is to be o
to the integral attenuated energy fluence spectrum at mass-
determined. In practice, the limits of integration are the limits
depth t is given by
of energy over which c(E) is of a significant magnitude. If
‘ ‘
material intervenes between the source and the point of dose
–@μ ~E!/r#t
en
c ~E!dE 5 c ~E!e dE (3)
* t * o
0 0
determination, then the spectrum used in the calculation must
be the output spectrum of the source modified by the absorbing
where t is the mass-thickness (in kg·m ) of material between
effects of the intervening material. The values of μ (E)/r are
en the surface and the depth of interest, E is a particular energy
found in the tables of Ref 2.
represented in the spectrum, and c (E) is the energy fluence per
t
unit energy at mass-depth t. For a derivation of Eq 3 see
NOTE 2—For units and terminology in reports of data, E 170 and ICRU
Appendix X4. See also the qualifications of 5.1.3 and 5.1.4. For
Report 33 may be used as guides.
a demonstration of the experimental plausibility of Eq 3, see
4.2 If the material in which the absorbed dose is to be
Appendix X5.
calculated is a homogeneous combination of materials not
5.1.2 Using Eq 1 and 3, the relationship between the known
listed in the tables of Ref 2, μ (E)/r is determined as follows:
en
dose D and the desired dose D can be expressed as
i
A B
4.2.1 From Ref 2, obtain values of μ E /r for each
~ !
en
‘ A
–@μ ~E!/r #t A
en A A
component, i.
@c ~E!e #@μ ~E!/r #dE
* o en A
D
A
4.2.2 Determine the atomic fraction, f , for each component.
5 (4)
i
‘ B
D
–@μ ~E!/r #t B
B en B B
@c ~E!e #@μ ~E!/r #dE
4.2.3 Calculate μ (E)/r from the following equation:
* o en B
en
A
i
where μ , r , and t are the mass energy absorption
en A A
μ ~E!/r5 f @μ ~E!/r# (2)
(
en i en
i
coefficient, the density and the relevant mass-thickness for
4.2.4 Values of μ (E)/r must be determined for each value material A, and where similar notation is used for material B.
en
of E for which c(E) is significant, where E is the photon For further details on the derivation of Eq 4, see Appendix X6.
energy. All the variables in Eq 4 are presumed to be known except the
4.3 The integral contained in Eq 1 is evaluated numerically. desired value for D . The integrals in Eq 4 must be performed
B
The values of μ (E)/r in Ref 2 are tabulated for specific numerically.
en
energies. In evaluation of the integral referred to in actual 5.1.3 The use of Eq 3 is based on the existence of charged
practice, it is often desirable to choose energy intervals that particle equilibrium (for further discussion see 1.3). This
would not correspond to the tabulated values in Ref 2. In such condition may be reasonably well met when the region of
cases, the appropriate value of μ (E)/r for the chosen energies interest is at a sufficient distance from boundaries representing
en
should be determined by an acceptable interpolation procedure. changes in atomic number or material density (see Appendix
The range of energy over the total photon spectrum is divided X1).
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 666
5.1.4 Wide Beam vs. Narrow Beam Approximation. 6. Accuracy
5.1.4.1 The use of the mass energy absorption coefficient,
6.1 The accuracy of this practice depends primarily on the
μ , in Eq 3 is based on the assumption that the irradiation
en
accuracy to which the incident energy spectrum is known. In
approaches the “wide beam” as opposed to “narrow beam”
general, even a poor estimate of a spectrum will give a better
condition. The wide beam and narrow beam conditions repre-
estimate of the absorbed dose at a given location than one
sent limiting cases which are only approximately realized for
would get by assuming some sort of single“ effective photon
real experiments. In the narrow beam case, photons which are
60 137
energy.” Although Co and Cs have well-defined primary
scattered out of the narrow beam are assumed to be lost from
gamma-ray energies, the radiation energy spectrum from most
the beam, and are assumed to have no further importance to the
practical sources contains a significant Compton scattered
experiment. In the broad beam case, photons which are
component that could lead to significant errors if neglected (see
scattered out of a given small region of the broad beam are
ICRU Report 18).
presumed to be replaced by photons scattering in from adjacent
regions of the beam. For the narrow beam limiting case, Eq 3
6.2 As stated in 1.3, the results of this practice are not valid
should be replaced by
unless charged particle equilibrium conditions exist in the
–@μ~E!/r#t
material at the depth of application. For depths less than that
c ~D!5c ~E!e (5)
t o
required for equilibrium, the absorbed dose could be higher or
where μ is the photon attenuation coefficient. Values of
lower than this method would predict. At depths greater than
μ(E)/r are found in the tables of Ref 2. For most practical
required for equilibrium, the accuracy of the results depends
problems the results of photon attenuation lie between the
primarily upon the accuracy of the attenuation correction
results of Eq 3 and Eq 5.
applied in Eq 3 and the knowledge of the incident energy
5.1.4.2 It is possible to determine the magnitude of the
spectrum.
change which would have resulted had Eq 1 and Eq 5 been
6.3 The procedures used in this method neglect the possible
used rather than using Eq 1 and Eq 3 in order to develop Eq 4.
nonlocality of energy deposition by secondary electrons but do
The resulting change in the ratio D /D calculated by Eq 4 is
A B
correct for production of bremsstrahlung by secondary elec-
related to the factor
B A trons. For the energy range specified in this practice, these
–@μ ~E!/r #t –@μ ~E!/r #t
en B A
e e
considerations contribute about 5 % or less to the overall
F~E! 5 (6)
B A
–@μ ~E!/r #t –@μ ~E!/r #t
B en A
e e
uncertainty.
If, over the energy range of interest, F(E) differs from unity
by a percentage which is greater than the acceptable dosimetry
7. Keywords
error, then the application of this practice may be inappropri-
7.1 calculation of absorbed dose; charged particle equilib-
ate. In that case an appropriate transport calculation is recom-
rium; radiation dosimetr
...