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OCR for page 123
Appendix G
Glossary
annealing
barn
criticality
criticality accident
curie
eutectic
favorable geometry
Missile material
fission cross section
a procedure to encourage the diffusion of a
substance into a solid matrix by heating below
the melting point
a unit of area, equal to 1 0-24 cm2, used to
measure nuclear cross sections
the presence of a self-sustaining fission chain
reaction
an unplanned criticality
a measure of the quantity of radioactive material
in a sample, equal to 3.7 x 10~° disintegrations
per second
a mixture of two substances in the proportion
that establishes a compound with the lowest
possible melting point. The liquid is a single
phase; the constituent solids separate upon
equilibrium cooling.
a shape of a container holding fissile material in
which the geometric dimensions prevent a
criticality excursion regardless of enrichment,
concentration, or water-equivalent external
reflection
any mixture of Missile nuclides (uranium-233,
uranium-235, and plutonium-239) capable of
criticality
a measure (in units of area) of the probability
that a fission event occurs upon collision of a
neutron and a Missile nucleus
Gal
OCR for page 124
G.2 AN EVALUATION OF DOE ALTERNATIVE FOR MSRE
fluorination a process using any of a number of chemical
agents to introduce fluorine into a substrate
(producing fluoride compounds, as by halogen
exchange or oxidation)
getter a chemically active material that reacts to trap an
evolved gas
hycirofluorination a process using hydrogen fluoride (HF). In this
application, ~ reoxidizes reduced centers that
have been formed in the former melt. It does not
take uranium to an oxidation state higher than
IV.
isobars nuclei of two different elements (i.e., differing
atomic number Z) with the same mass number
(A)
kilogram a metric unit of mass
liquidus line the boundary in a phase diagram of a binary
system that separates a two-phase region from a
single-phase liquid region
mole a unit of measure equal to Avogadro's number of
particles
oxidation state a measure of the number of electrons needed to
share in bonds to establish the electronic
neutrality of the pure species
psia literally, pounds per square inch absolute, a
measure of pressure (a vacuum = 0 psia;
atmosphere [atml = 14.7 psia)
psig literally, pounds per square inch gauge, a
measure of pressure from a gauge that compares
to an ambient atmospheric reading (psi" = psia-
1 atm; 1 atm = 0 psi")
radiolysis any chemical reaction induced by the effects of
ionizing radiation
reductant a substance participating in a chemical reaction
by reducing, or adding an electron to, a species
of interest, thereby lowering its oxidation state
OCR for page 125
APPENDIX G GLOSSARY
roentgen
torr
G.3
a unit of radiation exposure; currently defined as
2.58 x 10-4 coulombs per kilogram and derived
historically as the amount of gamma radiation
that produces 1 electrostatic unit of charge (via
production of ions) in ~ cm3 of air at 1 atm and
O°C
millimeters of mercury, a measure of pressure
(latm=760torr)
OCR for page 126
Representative terms from entire chapter:
radiation exposure
