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OCR for page 189
GLOSSARY
Accessible Those portions of the environment clirectly in
environment contact with or readily available for use by human
beings. Includes the earth's atmosphere, the land
surface, aquifers, surface waters, and the oceans.
In 40 CFR 191, the environment outside a surface
cleaned as enclosing a controlled area.
ALARA An acronym for "as low as reasonably achievable",
a concept meaning that the design ant! use of
sources, and the practices associated therewith,
should be such as to ensure the exposures are kept
as low as is reasonably practicable, economic ant}
social factors being taken into account.
Backfill
Becquerel
Biosphere
The material used to refill the excavated potions of
a repository or of a borehole after waste has been
emplaced.
International unit of radioactivity. Symbol Bq = 1
(lisintegration per second.
The region of the earth in which environmental
pathways for transfer of radionuclicles to living
organisms are locater} ant! by which radionuclicles
in air, ground water, and soil can reach humans to
be inhaled, ingested, or absorbed through skin.
Humans can also be exposed to direct irradiation
from radionuclides in the environment.
Borehole A cylindrical excavation in the earth, made by a
rotary drilling device.
189
OCR for page 190
I90 YUCCA MOUNTAIN STANDARDS
Canister A closed or sealer! container for nuclear fuel or
other radioactive material, which isolates ant!
contains the contents; it might rely on other
containers (e.g. a cask) for shielcling.
Collective dose The sum of the indiviclual closes received in a given
period of time by a specified population from
exposure to a specifier] source of radiation.
Critical group Originally clefined for close by the ICRP (ICRP,
1977, p.17; ICRP, 19SSb, pp.3-4) as a relatively
homogeneous aroun of neonie whose location and
-- of r -- r- -r
habits are such that they are representative of those
individuals expected to receive the highest doses as
a result of the discharges of radionuclides. The
definition is extencled to risk in Chapter 2 of this
report.
Critical
pathway
Disposal
Disposal
package
Dose
The dominant environmental pathway through
which a given radionuclide reaches the critical
group.
Permanent isolation of spent nuclear fuel or
radioactive waste from the accessible environment
with no intent of recovery, whether or not such
isolation permits the recovery of such fuel or waste.
The primary container that hoicis, ant! is in contact
with, solidifies! high-level radioactive waste, spent
nuclear fuel, or other radioactive materials, and any
overpacks that are emplaced at a repository.
A measure of the radiation received or absorbent by
a target.
OCR for page 191
GLOSSARY
191
Absorbed close per unit time.
Engineered The waste form, cladding, backfill, anti canister, all
barrier system of which are intended to retarc! disperson of
raclionuclides.
Irradiation of persons or materials. Exposure of
persons to ionizing radiation can be either:
I. external exposure, irradiation by sources
outside the body; or
2. internal exposure, irradiation by sources
inside the body.
Fault A surface or zone of rock fracture along which
there has been clisplacement.
Geologic A system that is intended to be used for, or might
repository be used for, the disposal of radioactive wastes in
excavated geologic media. A geologic repository
includes: (~) the geologic repository operations
area and (2) the portion of the geologic setting that
provides isolation of the radioactive waste.
Ground water Water that permeates the rock strata of the Earth,
filling their pores, fissures and cavities. (It
excludes water of hydration.)
Ground water The principal means by which radionuclides can be
transport mobilized from an underground repository ant}
moved into the biosphere. Avoiding or minimizing
such transport is the basis for selecting and
designing repository systems.
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192 YUCCA MOUNTAIN STANDARDS
Half-life In physics, the time required for the transformation
of one-half of the atoms in a given radioactive
decay process, following the exponential law
(physical half-life).
High-level The highly radioactive material resulting from the
radioactive reprocessing of spent nuclear fuel, including liquic]
waste waste procluced directly in reprocessing and any
solid material clerivec! from such liquid waste that
contains fission products in sufficient
concentrations. Other highly radioactive material
that the U.S. Nuclear Regulatory Commission,
consistent with existing law, determines by rule
requires permanent isolation. Also referred to as
high-level waste (HEW).
IAEA International Atomic Energy Agency is an
autonomous intergovernmental organization
establisher! by the Uniter! Nations. It is authorized
to foster research and development in the peaceful
uses of nuclear energy, to establish or administer
health and safety standards, and to apply safeguards
in accordance with the Treaty of the Non
Proliferation of Nuclear Weapons.
OCR for page 193
GLOSSARY 193
ICRP The International Commission on Radiological
Protection is an international organization that
clevelops guidance and standards for radiological
measurement ant! protection of public and
occupational health. The ICRP is composer! of a
Chairman and never more than 12 other members.
The selection of the members is made by the ICR*
from nominations submitted to it by the National
Delegations to the International Congress of
Radiology en c! the ICRP staff itself. Members of
the ICRP are chosen on the basis of their
recognized activity in the fields of medical
racliology, radiation protection, physics, biology,
genetics, biochemistry, ant! biophysics. The
ICRP's rules require that its members be elected
every four years.
Linear model Also, linear dose-effect relationship; expresses the
health effect, such as mutation or cancer as a direct
(linear) function of close.
Natural The amount of radiation to which a member of the
background population is exposed from natural sources, such as
radiation terrestrial radiation due to naturally occurring
radionuclides in the soil, cosmic radiation
originating in outer space, and naturally occurring
raclionuclides deposited in the human body.
NCRP National Council on Radiation Protection ant}
Measurements is an organization of nationally
recognized scientists who share the belief that
significant advances in radiation protection and
measurement can be achieved through cooperative
effort. It conducts research focusing on safe
occupational exposure levels and disseminates
information.
OCR for page 194
194 YUCCA MOUNTAINSTANDARDS
Performance Analysis to predict the performance of the system
assessment or subsystem, followed by comparison of the
results of such analysis with appropriate stanciarcis
or criteria.
Population dose The sum of the doses to all the individuals in a
specified group. In units of person-sievert or
person-rem. (Also called collective dose.)
Radioactive The spontaneous transformation of a nuclide into
clecay one or more different nuclides accompanied by
either the emission of energy or particles. Unstable
atoms decay into a more stable state, eventually
reaching a form that floes not decay further or is
very long-liveti.
Radioactive Any material that contains or is contaminated with
waste radionuclides at concentrations or radioactivity
levels greater than the exempt quantities
establisher] by the competent authorities ant! for
which no use is foreseen.
Radionuclide A radioactive species of an atom characterized by
the constitution of its nucleus.
Rem A unit of dose equivalent to one-hunciredth of a
sievert (1 cSv).
OCR for page 195
GLOSSARY 195
Repository Any system licensed by the U.S. Nuclear
Regulatory Commission that is intended to be used
for, or can be used for, the permanent deep
geologic disposal of high-level radioactive waste
and spent nuclear fuel, whether or not such system
is ciesigned to permit the recovery, for a limited
period during initial operation, of any material
placed in such system. Such term includes both
surface and subsurface areas at which high-level
radioactive waste and spent nuclear fuel handling
activities are conducted.
Risk In the context of this study, risk is the probability
of an individual receiving an adverse health effect
and includes the probability of getting a dose.
Saturated zone That part of the eari;h's crust beneath the regional
water table in which all voids, large ant} small, are
ideally filled with water under pressure greater than
atmospheric.
Seismic Pertaining to, characteristic of, or producer] by
earthquakes or earth vibrations.
Sievert International Unit (SI) of equivalent radiation dose.
The product of the absorbed close and the quality
factor of the radiation. Symbol Sv.
Spent fuel Fuel that has been withdrawn from a nuclear
reactor following irradiation, the constituent
elements of which have not been separates} by
reprocessing.
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196 YUCCA MOUNTAIN STANDARDS
Stochastic Random events leading to effects whose probability
health effects of occurrence in an exposeci population (rather than
severity in an affected individual) is a direct
function of dose; these effects are commonly
regarded as having no threshold; hereditary effects
are regarcled as being stochastic; some somatic
effects, especially carcinogenesis, are regarciec] as
being stochastic.
Storage
Turf
Retention of high-level radioactive waste, spent
nuclear fuel, or transurar~ic waste with the intent to
recover such waste or fuel for subsequent use,
processing, or (disposal.
Rock former! from consolidate~i volcanic ash.
Units Unitsa Symbol Conversion Factors
Becquerel Bq I disintegration/sec=2.7 x 10
(SI) ~ ~ Curies
Curie Ci 3.7 x 10~° disintegrations/sec=
3.7 x 10~° Becquerels
Gray (SI) Gy 1 Joule/kg= lOOrads
Rad red 100 ergs/gram = 0.01 Grays
Rem rem 0.01 Sievert
Sievert (SI) Sv 100 rems
a International Units are designated SI.
Unsaturated The zone between the land surface and the regional
zone water table. Generally, fluid pressure in this zone
is less than atmospheric pressure, anti some of the
voids might contain air or other gases at
atmospheric pressure. Beneath flooded areas or in
perched water bociies the fluid pressure locally may
be greater than atmospheric. Also referred to as
vadose zone.
OCR for page 197
GLOSSARY 197
Vadose zone See clefinition for unsaturated zone.
Volcanism The process by which magma and the associated
gases rise into the crust and are extruded onto the
earth's surface and into the atmosphere.
Waste form The radioactive waste materials and any
encapsulating or stabilizing matrix.
Waste package The waste form and any containers, shielding,
packing anti other absorbent materials immecliately
surrounding an individual waste container.
Water table The upper surface of the saturates} zone on which
the water pressure in the porous medium equals
atmospheric pressure.
OCR for page 198
Representative terms from entire chapter:
nuclear fuel
