Glossary

Background Radiation
Nuclear (or ionizing) radiations arising from within the body and from the surroundings to which individuals are always exposed. The main sources of the natural background radiation are potassium-40 in the body, potassium-40 and thorium, uranium, and their decay products (including radium) present in rocks and soil, and cosmic rays.
Ballistic Missile
A missile that is lifted into space by a booster rocket and then descends toward its target in a free falling ballistic trajectory.
Ballistic missile defense (BMD)
Measures designed to detect, identify, track, and defeat attacking ballistic missiles, in both strategic and theater tactical roles, during any portion of their flight trajectory (boost, post-boost, mid-course, or terminal phase) or to nullify or reduce the effectiveness of such attack.
See; Boost Phase.
Base Surge
A cloud which rolls outward from the bottom of the column produced by a subsurface explosion. For underwater bursts the visible surge is, in effect, a cloud of liquid (water) droplets with the property of flowing almost as if it were a homogeneous fluid. After the water evaporates, an invisible base surge of small radioactive particles may persist. For subsurface land bursts the surge is made up of small solid particles but it still behaves like a fluid. A soft earth medium favors base surge formation in an underground burst.
Baruch Plan
The U.S. initiative to outlaw nuclear weapons and to internationalize global stocks of fissile material for use in peaceful nuclear programs.
Becquerel
A modern unit of radioactivity replacing the curie; the activity of an amount of a radioactive material in which one nucleus decays each second.
See; Curie, Radioactivity.
Beryllium
A highly toxic steel-grey metal, which can be used in nuclear reactors as a moderator, reflector or cladding material. In nuclear weapons, beryllium surrounds the fissile material and reflects neutrons back into the nuclear reaction.
Beta Decay
The radioactive decay process which occurs via the transmission of a beta particle (or high speed electron).
See; Beta Particle, Electron.
Beta Particle
A charged particle of very small mass emitted spontaneously from the nuclei of certain radioactive elements. Most (if not all) of direct fission products emit (negative) beta particles. Physically, the beta particle is identical with an electron moving at high velocity. They normally can be stopped by the skin or a very thin sheet of metal.
See; Beta Decay, Electron, Fission Products, Radioactivity.
Bikini Atoll
On March 1, 1954, a deliverable H-bomb using solid lithium deuteride was tested by the United States on Bikini Atoll in the Marshall Islands. Between 1946 and 1958, 23 nuclear devices were exploded at Bikini Atoll.
It left a crater more than 1/2 mile wide and several hundred feet deep and ejected several million tons of radioactive debris into the air. This fallout forced the evacuation of the surrounding islands. To this day, radiation levels on Bikini remain high enough to make the island uninhabitable.
See; Hydrogen Bomb.
Binding Energy
The total binding energy of a nucleus is the energy required to separate it into its constituent neutrons and protons. Conversely, when neutrons and protons are combined to form nuclei, energy equal in amount to the binding energy is released in the process. Because the nuclear force is so strong, nuclear binding energies are typically a million times greater than the electromagnetic energies binding electrons to the nucleus in an atom or binding atoms together in molecules.
See; Nucleus.
Blanket
A layer of nuclear material, such as uranium-238 or thorium-232, placed around the fuel core of a reactor. During operation of the reactor, material in the blanket absorbs neutrons and decays, with products forming new fissionable material.
Blast Scaling Laws
Formulas which permit the calculation of the properties, e.g., overpressure, dynamic pressure, time of arrival, duration, etc., of a blast wave at any distance from an explosion of specified energy from the known variation with distance of these properties for a reference explosion of known energy (e.g., of 1 kiloton).
See; Cube root law.
Blast Wave
A pulse of air in which the pressure increases sharply at the front, accompanied by winds, propagated from an explosion.
Boiling-Water Reactor
A reactor in which water is boiled directly in the reactor vessel.
See; Light-Water Reactor, Pressurized-Water Reactor, Reactor.
Boost-phase
That part of the ballistic missile flight path that begins at launch and lasts from 80 seconds up to five minutes. During boost phase, the booster and sustainer engines operate, and warheads have not yet been deployed.
Boosted Fission Weapon
A weapon in which neutrons produced by thermonuclear reactions serve to enhance the fission process. The thermonuclear energy represents only a small fraction of the total explosion energy.
See; Fission, Thermonuclear.
The BRAVO test
On March 1, 1954, a deliverable H-bomb using solid lithium deuteride was tested by the United States on Bikini Atoll in the Marshall Islands. Operation BRAVO had a yield of 14.8 megatons of TNT - over double its expected yield. It was the largest American nuclear test. The fallout forced the evacuation of the surrounding islands. To this day, radiation levels on Bikini remain high enough to make the island uninhabitable. This test was a key factor in creating the Atmospheric Test Ban Treaty (1963).
See; Lucky Dragon.
British Mission
As part of the Quebec Agreement in August 1942, a team of British scientists led by Sir James Chadwick, and included Rudolph Peierls, M.L.E. Oliphant, Otto Frisch, James Tuck, Klaus Fuchs, and 13 others, assisted the Manhattan Project in many critical areas. These scientists served diligently at Los Alamos throughout the war, and some even remained after its conclusion.
Calutron
Ernest O. Lawrence built a 184-inch cyclotron to separate Uranium 235. The new machine was named Calutron after the University of California, where Lawrence worked.
CANDU
CANDU stands for CANada Deuterium Uranium. The CANDU reactor is a pressurized-heavy water,(PHWR) natural uranium (i.e. unenriched) power reactor; hence, it needs a more efficient moderator than most other power reactor designs - in this case heavy water (D2O, deuterium oxide). This means that they can be operated without expensive fuel enrichment facilities. Most less-developed countries find this attractive because they cannot afford the enrichment facilities, and cannot be assured of access to enriched uranium.
See; Light-Water Reactor, Pressurized-Water Reactor, Reactor.
Centrifuge
A rotating vessel for uranium enrichment. The heavier U238 isotopes in the UF6 gas tend to concentrate at the walls of the centrifuge as it spins. Scopes are placed inside the centrifuge to selectively separate the U238 and U235 isotopes.
Cesium-137 (Cs-137)
A strong gamma ray source and can contaminate property, entailing extensive clean-up. It is commonly used in industrial measurement gauges and for irradiation of material. Half-life is 30.2 years.
See; Gamma Radiation, Radioactivity.
Chain Reaction
A process taking place in an atomic bomb or nuclear reactor in which one fission event releases neutrons and energy. The neutrons in turn produce more fissions releasing more energy and forming a chain of nuclear fissions.
See; Fission, Neutron, Supercritical.
Chicago Pile Number One (CP-1)
Located at the University of Chicago, underneath an abandoned football stadium, Chicago Pile Number One or CP-1 went critical on December 2, 1942.
See; Met Lab.
Circular Error Probable (CEP)
A measure of missile accuracy. A missile's CEP is the radius of a circle around the target in which 50% of the warheads aimed at that target will land.
Clean Weapon
One in which measures have been taken to reduce the amount of residual radioactivity relative to a "normal" weapon of the same energy yield.
Cobalt-60 (Co-60)
A strong gamma ray source, and is extensively used as a radiotherapeutic for treating cancer, food and material irradiation, gamma radiography, and industrial measurement gauges. Half-life is 5.27 years.
See; Gamma Radiation, Radioactivity.
Comprehensive Nuclear Test-Ban Treaty (CTBT)
This international treaty prohibits all nuclear explosions. The treaty establishes the CTBT Organization (CTBTO) to verify compliance with the treaty through a global monitoring system once it enters into force.
Compton Effect
The scattering of photons (of gamma or X rays) by the orbital electrons of atoms. In a collision between a (primary) photon and an electron, some of the energy of the photon is transferred to the electron which is generally ejected from the atom. Another (secondary) photon, with less energy, then moves off in a new direction at an angle to the direction of motion of the primary photon.
Condensation Cloud
A mist or fog of minute water droplets which temporarily surrounds the fireball following a nuclear (or atomic) detonation in a comparatively humid atmosphere. The expansion of the air in the negative phase of the blast wave from the explosion results in a lowering of the temperature, so that condensation of water vapor present in the air occurs and a cloud forms. The cloud is soon dispelled when the pressure returns to normal and the air warms up again. The phenomenon is similar to that used by physicists in the Wilson cloud chamber and is sometimes called the cloud chamber effect.
Condenser
The equipment that cools steam and turns it back into water.
See; Light-Water Reactor, Pressurized-Water Reactor, Reactor.
Containment Building
A structure made of steel-reinforced concrete that houses the nuclear reactor. It is designed to prevent the escape of radioactive material into the environment.
See; Light-Water Reactor, Pressurized-Water Reactor, Reactor.
Contamination
The deposit of radioactive material on the surface of structures, areas, objects, or personnel, following a nuclear explosion. This material generally consists of weapon debris becoming incorporated with particles of dirt, etc. Contamination can also arise from radioactivity induced in certain substances by the action of neutrons from a nuclear explosion.
See; Radioactivity.
Control Rods
Devices that can be raised and lowered in the reactor core to absorb neutrons and regulate the chain reaction. The speed of the chain reaction is controlled by control rods.
See; Light-Water Reactor, Pressurized-Water Reactor, Reactor.
Convention on the Physical Protection of Nuclear Material
Provisions of this convention oblige parties to ensure that during international transport across their territory or on ships or aircraft under their jurisdiction, nuclear materials for peaceful purposes are protected at the agreed levels. The convention also provides a framework for international cooperation on the protection, recovery, and return of stolen nuclear material and on the application of criminal sanctions against persons who commit crimes involving nuclear material.
Coolant
A substance used to cool the reactor and to slow neutrons. In most nuclear power plants, water is used for cooling to keep the reactor from getting too hot and to slow neutrons down so they are more likely to cause uranium-235 to fission. The most common coolants are water and heavy water.
See; Light-Water Reactor, Pressurized-Water Reactor, Reactor.
Cooling Pool
Large tanks of water at all nuclear power plants into which spent fuel rods are stored before reprocessing or disposal.
Cooling Tower
A structure in a nuclear power plant used to remove heat from cooling water from the condenser. The cooling tower prevents thermal pollution of lakes and rivers.
See; Light-Water Reactor, Pressurized-Water Reactor, Reactor.
Cooperative Threat Reduction (CTR)
This U.S. program addressing threats from the former Soviet weapons of mass destruction. The program has focused primarily on (1) destroying vehicles for delivering nuclear weapons, their launchers (such as silos and submarines), and their related facilities; (2) securing former Soviet nuclear weapons and their components; and (3) destroying Russian chemical weapons. The term is sometimes used generically to refer to all U.S. nonproliferation programs in the former Soviet Union, including those implemented by the U.S. Departments of Energy, Commerce, and State.
Core
The central portion of a nuclear reactor containing the fuel elements, moderator, and support structures.
See; Light-Water Reactor, Pressurized-Water Reactor, Reactor.
Counterforce
Military strategies, attacks, or weapons directed against an opponent's military forces, command posts, and war-fighting targets.
Countervailing
Nuclear strategy, adopted under the Carter administration, which stressed counterforce targeting, greater flexibility in a protracted nuclear war, and survivable command and control centers to conduct such a war.
Countervalue
Military strategies, attacks, or weapons directed against an opponent's population, society and economy.
Critical Mass
The minimum mass of a fissionable material that will just maintain a fission chain reaction under precisely specified conditions, such as the nature of the material and its purity, the nature and thickness of the tamper (or neutron reflector), the density, and the physical shape. For an explosion to occur, the system must be supercritical (i.e., the mass of the material must exceed the critical mass under the existing conditions).
See; Fission, Supercritical.
Criticality
The state of a nuclear reactor when it reaches the stage of a self-sustaining chain reaction.
Cruise Missile
A pilotless, jet propelled guided missile. Cruise missiles may be armed with conventional or nuclear warheads and launched from either aircraft, submarines, or land-based platforms.
Cube Root Law
A scaling law applicable to many blast phenomena. It relates the time and distance at which a given blast effect is observed to the cube root of the energy yield of the explosion.
Curie (Ci)
An older unit of radioactive decay rate defined as 3.7 x 1010 disintegrations per second. The gamma curie is sometimes defined correspondingly as the activity of material in which this number of gamma-ray photons are emitted per second.

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