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Appendix
Radiation Quantities and Units
Definitions
Acronyms
The quantities and units of radiation dose are inherently more complex
than those used in toxicology or pharmacology, and additional complexity has
resulted from several changes required by evolving concepts in radiation
dosimetry. The first widely used physical quantity of radiation was "exposure,"
related to the ability of x or gamma radiation to ionize air; its unit was the
roentgen (R). Exposure was limited to photon radiation with energy less than
2.5 MeV. The quantity "absorbed dose" (D) was introduced because it was
applicable to all forms of ionizing radiation and absorbing materials. Absorbed
dose is energy deposited per unit mass, and its original unit was the rep
(roentgen equivalent-physical); 1 rep equaled 93 ergs per g (0.0093 J per kg) of
absorbing material. The rep was replaced with the red (radiation absorbed dose);
1 red equaled 100 ergs per g (0.01 J per kg). The "dose equivalent" (H) and its
unit, the rem (roentgen equivalent-man), were introduced to account for the
different biologic effects of the same absorbed dose from different types of
radiation; H is the product of D, Q. and N at a point of interest in tissue, where
D is absorbed dose, Q is the quality factor, and N is the product of any other
modifying factors. The "effective dose equivalent" was introduced to include
the different sensitivities of individual tissues and organs, which are important
for internal dosimetry: its unit is the same as the unit of"dose equivalent."
In the 1990 recommendations of the International Commission on
Radiological Protection (ICRT 1991), the use of N was dropped and the
radiation weighting factor (WR) was substituted for Q. In addition, Systeme
International (SI) units have been adopted by ICRP (1977~. The unit of dose is
270
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APPENDIX
271
now the gray (Gy), and the unit of equivalent dose, effective dose, and
associated quantities is the sievert (Sv). Each of those units equals 1 J per kg. In
terms of conventional units, 1 Gy = 100 red and 1 Sv = 100 rem.
SI units have been almost universally adopted internationally and in the
US scientific community, but they have not been embraced enthusiastically by
the US regulatory and engineering communities. The principal international
authority on radiologic quantities and units is the International Commission on
Radiation Units and Measurements (ICRU), which maintains administrative
offices in the National Council on Radiation Protection and Measurements
(NCRP) headquarters in Bethesda, Maryland.
Definitions of various terms, quantities, and units used to describe
radioactivity, radiation, and their control are given below. Most have been
adapted from "Standards for Protection Against Radiation," Title 10, Part 20, of
the Code of Federal Regulations (10 CFR 20~. Definitions of effective dose and
equivalent dose were adapted from ICRP (1991~.
DEFINITIONS
absorbed dose The energy imparted by ionizing radiation per unit mass of
irradiated material. The units of absorbed dose are the red and the gray
(Gy).
activity The rate of disintegration (transformation) or decay of radioactive
material. The units of activity are the curie (Ci) and the becquerel (Bq).
As Low As Reasonably Achievable (ALARA) - Making every reasonable
effort to maintain exposures as far below Me dose limits as is practical,
taking into account economic considerations and other societal concerns.
becquerel (Bq) The SI unit of activity. 1 Bq equals 1 disintegration per second.
byproduct material As used in the Atomic Energy Act:
(1) Any radioactive material (except special nuclear material) yielded in, or
made radioactive by, exposure to the radiation incident to the process of
producing or using special nuclear material; and
(2) The tailings or wastes produced by the extraction or concentration of
uranium or thorium from ore processed primarily for its source-material
content, including discrete surface wastes resulting from uranium-solution
extraction processes. Underground ore bodies depleted by solution
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GUIDELINES FOR EXPOSURE TO TENORM
extraction operations do not constitute byproduct material according to this
definition.
collective dose The sum of the individual doses received in a given period by a
specified population from exposure to a specified source of radiation.
committed dose equivalent (HT,50) The dose equivalent to organs or tissues of
reference (T) that will be received from an intake of radioactive material by
a person during the 50-y period after the intake.
committed effective dose equivalent (HE,50) The sum of the products, for each
body organ or tissue that is irradiated, of the applicable weighting factor
and the committed dose equivalent to the organ or tissue (HE 50 = ZWTHT 501.
curie (Ci) The conventional unit of activity. 1 Ci equals 3.7 x 10'°
disintegrations per second, which equals 3.7 x 10~° Bq.
dose or radiation dose A generic term that means absorbed dose, dose
equivalent, effective dose equivalent, committed dose equivalent,
committed effective dose equivalent, or total effective dose equivalent.
dose equivalent (HT) The product of the absorbed dose in tissue, the quality
factor, and all other necessary modifying factors at the location of interest.
The units of dose equivalent are the rem and the sievert (Sv).
effective dose (E) The sum of weighted equivalent doses to all tissues and
organs of the body (ICRP 1991~. E = IwTHT where HT is the equivalent
dose and WT iS the tissue weighting factor.
effective dose equivalent (HE) The sum of the products, for each body organ or
tissue that is irradiated, of the dose equivalent to the organ or tissue and the
applicable weighting factor (HE = IWTHT)
equivalent dose (HT) In radiation protection, the absorbed dose averaged over a
tissue or organ (rather than a point, as is the case for dose equivalent) and
weighted for the radiation quality that is of interest. For this quantity, the
weighting factor is called the radiation weighting factor instead of the
quality factor, as used in earlier dosimetric quantities.
external dose The dose received from radiation sources outside the body.
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APPENDIX
273
exposure A quantity used to express external ionizing radiation, or to indicate
presence of radionuclides or radiation affecting individuals or populations
(for example, "exposure" to radionuclides in the environment).
gray (Gy) The SI unit of absorbed dose. 1 Gy equals an absorbed dose of 1 J/kg
(100 red).
internal dose The dose received from radioactive material taken into the body.
limits (dose limits) The permissible upper bounds of radiation doses.
member of the public Any person except when that person is receiving an
occupational dose.
quality factor (Q) The modifying factor that is used to derive dose equivalent
from absorbed dose for purposes of radiation protection.
red The special unit of absorbed dose. 1 red equals an absorbed dose of 100
ergs per gram or 0.01 J per kg (0.01 Gy).
radiation (ionizing radiation) Alpha particles, beta particles, gamma rays, x
rays, neutrons, high-energy electrons, high-energy protons, and other
particles capable of producing ionization in matter. (As used in this report,
radiation does not include nonionizing radiation, such as radiowaves,
microwaves, visible, infrared, or ultraviolet light.)
reference man A hypothetical aggregation of human physical and physiologic
characteristics arrived at by international consensus. These characteristics
can be used by researchers and public-health workers to standardize results
of experiments and to relate biologic insult to a common base.
relative biological effectiveness (RBE) The ratio of the absorbed dose of a
reference radiation (usually 200 keV x rays) to the absorbed dose of the test
radiation required to produce the same degree of biologic effect. The RBE
of the test radiation depends on the exact biologic effect in a given species
of organism under a given set of exposure conditions.
rem The special unit of any of the quantities expressed as dose equivalent. The
dose equivalent equals the product of the absorbed dose in reds and the
quality factor (1 rem= 0.01 Sv).
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GUIDELINES FOR EXPOSURE TO TENORM
roentgen (R) The unit of exposure. One roentgen equals the amount of x or
gamma radiation required to produce ions carrying a charge of 1
electrostatic unit (esu) per cubic centimeter (2.58 x 104 coulomb per kg) of
dry air under standard conditions.
sievert (Sv) The SI unit of any of the quantities expressed as dose equivalent.
The dose equivalent in sieverts is equal to the product of the absorbed dose
in grays and the quality factor (1 Sv = 100 rem).
source material As defined under the Atomic Energy Act:
(1) Uranium, thorium, or any combination of uranium and thorium in any
physical or chemical form; or
(2) Ores that contain, by weight, 0.05% or more of uranium, thorium, or
any combination thereof. Source material does not include special nuclear
material.
special nuclear material As defied under the Atomic Energy Act:
(1) Plutonium, uranium-233, uranium enriched in uranium-233 or In
uranium-235, and any other material that the Nuclear Regulatory
Commission, pursuant to the provisions of Section 51 of the act, determines
to be special nuclear material, but not including source material; or
(2) Any material artificially enriched by any of the foregoing, but not
including source material.
Total Effective Dose Equivalent (TEDE) The sum of the deep-dose equivalent
(for external exposures) and the committed effective dose equivalent (for
internal exposures). It is a term used by some organizations to emphasize
that the sum of the contributions from external and internal sources is
meant. This term is not a part of the recommendations of the ICRP or
NCRP. The term effective dose equivalent, without the modifier "total," is
sufficient to imply contributions from external and internal sources.
uranium fuel cycle The operations of milling of uranium ore, chemical
conversion of uranium, isotopic enrichment of uranium, fabrication of
uranium fuel, generation of electricity by a light-water-cooled nuclear
power plant using uranium fuel, and reprocessing of spent uranium fuel to
the extent that these activities directly support the production of electric
power for public use. Does not include mining operations, operations at
waste-disposal sites, transportation of radioactive material in support of
these operations, and the reuse of recovered nonuranium special nuclear
and byproduct materials from the cycle.
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APPENDIX
275
weighting factor (WT) For an organ or tissue (T), the proportion of the risk of
stochastic effects resulting from irradiation of that organ or tissue to the
total risk of stochastic effects when the whole body is irradiated uniformly.
whole body For purposes of external exposure, He head, Funk (including male
gonads), arms above the elbow, and legs above the knee.
working level (WL) Any combination of short-lived radon decay products in 1 L
of air that will result in the ultimate emission of alpha-particle energy equal
to 1.3 x 105 MeV (2.08 x 10-5 J per my. Also equals the total energy emitted
by alpha particles from short-lived radon decay products in equilibrium win
radon gas in air at a concentration of 100 pCi/L (3.7 kBq per my.
LIST OF ACRONYMS
AEC Atomic Energy Commission
ALARA As low as reasonably achievable
AK Alaska
ARAR Applicable or relevant and appropriate requirement
BEIR Biological Effects of Ionizing Radiations
BSEE Bachelor of Science in Electrical Engineering
CEC Commission of the European Communities
CERCLA Comprehensive Environmental Response, Compensation, and
Liability Act
CFR Code of Federal Regulations
CRCPD Conference of Radiation Control Program Directors
DHHS Department of Health and Human Services
DOE Department of Energy
EC European Communities
EDTA Ethylenediamine tetraacetic acid
EPA Environmental Protection Agency
ERR Excess relative risk
FR Federal Register
FRC Federal Radiation Council
FUSRAP Formerly Utilized Sites Remedial Action Program
GAO Government Accounting Office
HI Hawaii
HPS Health Physics Society
IAEA International Atomic Energy Agency
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276
ICRP
ICRU
MCL
MCLG
MTHM
NARM
NCP
NCRP
NESHAP
NJ
NORM
NPDES
NRC
NYU
OSTP
PG
PIC
RCRA
Rn
ROD
RR Relative risk
SAB Science Advisory Board of the Environmental Protection
GUIDELINES FOR EXPOSURE TO TENORM
International Commission on Radiological Protection
International Commission on Radiation Units and
Measurements
Maximum contaminant level
Maximum contaminant level goal
Metric tons of heavy metal
Naturally occurring and accelerator-produced radioactive
materials
National contingency plan
National Council on Radiation Protection and Measurements
National Emission Standards for Hazardous Air Pollutants
New Jersey
Naturally occurring radioactive materials
National pollutant discharge elimination system
Nuclear Regulatory Commission
New York University
Office of Science and Technology Policy
Phosphogypsum
Pressurized ionization chamber
Resource Conservation and Recovery Act
Radon
Record of Decision
Agency
SFMP Surplus Facilities Management Program
SI Systeme International (units)
SSRCR Suggested state regulations for the control of radiation
TBC To be considered
TEDE Total effective dose equivalent
TENORM Technologically enhanced naturally occurring radioactive
materials
TLD Thermoluminescent dosimeter
TSCA Toxic Substances Control Act
UIC Underground injection control
UK United Kingdom
UNSCEAR United Nations Scientific Committee on the Effects of
Atomic Radiation
UMT Uranium mill tailings
UMTRCA Uranium Mill Tailings Radiation Control Act
US United States
USDW Underground source of drinking water
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APPENDIX
US EPA
WL
WLM
277
Environmental Protection Agency
Working level
Working level monk
Representative terms from entire chapter:
absorbed dose
