exposure. A measure expressed in roentgens of the ionization produced by gamma rays (ar =rays) ta air.
he exposure rate is the exposure per unit time fe.g., roentgens per hour). See dosh, dose rate,
roentgen.
exposure rate contours.
Lines jaining points which have the same radiation intensity tha
out pattern, represented in terms of roentgens per four.
Fall.
define a falt-
A single-engine Navy fighter developed by Vought-Sikorsky and Chance Vought. ‘Six F45N models were
used in CASTLE as a fighter element. An additional four earlier models scheduled forfisaivage were
used for unmanned fallout experiments in CASTLE Project 6.4.
F-84G.
Singte-engine jet fighter developed by Republic Aircraft and used from [VY (1952)
FB-36.
Featherweight 8-36 bomber; i.e., a B-36 bomber stripped of equipment {such as armament) to in-
(1956) as cloud sampler aircraft.
Jnrough REDWING
Crease its performance in a noncombat mode.
fallout. The process or phenomenon of the descent to the Earth's surface of particles con minated with
radigactive material from the radioactive cloud. The term is alsa applied in a collechive sense to
the cantaminated particulate matter itself.
The early for local) fallout is defined, Jomewhat arbitrarily, as particles reaching the Earth within 24 hours after a nuclear explosion. Tie delayed for
worldwide} fallout consists of the smaller particles, which ascend into the upper trap@sphere and
stratosphere and are carried by winds to 211 parts of the Earth. The delayed fallout fs brought to
Earth, mainly by rain and snow, over extended periads ranging from months to years.
i
fathometer. A depth-sounding instrument. The depth of water is measured by noting the timal the echo of a
sound takes to return from the bottom.
film badges.
Used for the indirect measurement of ionizing radiation.
Panagrn
absorbed dase is calculated.
rg ‘gia apy tats“ * 1
Generally contain twh
or three
pieces of film of different radiation sensitivities. They are wrapped in paper (or oth r thin material} that blocks light but is readily penetrated by gamma rays. The films are developg@d and the
degree of fogging (or blackening) observed is a measure of the gamma-ray exposure, frommpwhich the
Film badges can also measure beta and neutron radiation.
fireball. The luminous sphere of hot gases that forms a few millionths of a second after a miclear exploSion as the result of the absorption by the surrounding medium of the thermal X-rays emifted by the
extremely hot (several tens of millions of degrees) device residues. The exterior of th Fireball in
air is initially sharply defined by the luminous shock front and later by the limits of
themselves.
Fhe hot gases
€
fission. The process of the nucleus of a particular heavy element splitting into two nuclei f lighter
elements, with the release of substantia! amounts of energy. The most important fission
le materials
are uranium-235 and plutontum-239; fission is caused by the absorption of neutrons.
fission detectors. Radiation pulse detector of the proportional counter type in which a foil
fissionable materials is incorporated to make it respond to neutrans.
fission products.
A general term for the complex mixture of substances produced as a result of
Br film of
nuciear
fission. A distinction should be made between these and the direct fission products or fission fragments that are formed by the actual splitting of the heavy-element nuclei into nuclei of gedium atomic
weight.
Approximately 80 different Fission fragments result from roughly 40 different moges of fis-
sion of a given nuclear species (e.g., uranium-235 or plutonium-239).
The fissfon fragmemts, being
radtoactive, immediately begin to decay, farming addittonal (daughter) products, with the
the complex mixture of fissian products so formed contains aver 300 different radionuclid
elements.
fixed alpha.
Alpha rag oactivity that cannot be easily removed as evidenced by na measured chafige in a
swipe af a 100-cm
fluorescence.
area.
The emission of light (electromagnetic radiation) by a material as a result of t le absorp-
tion of energy from radiation.
sion process.
FOPU.
The term may refer to the radiation emitted, as wel! as to the emis-
Fallout Prediction Unit.
forward area.
The PPG and adjoining areas (e.g., Kwajalein).
fusion. The combination of two Tight nuclei to form a heavier nucleus, with the release of the ifference
af the nuclear binding energy of the fusion products and the sum of the binding energies offthe twa
light nuclei.
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