Glossary

Tactical Nuclear Weapons
Short-range nuclear weapons, such as artillery shells, bombs, and short-raoperations.
Terminal-phase
The final phase of a warhead's trajectory when it re-enters the earth's atmosphere and strikes the target.
Test
Defined in the Threshold Test Ban Treaty as either a single underground nuclear explosion conducted at a test site, or two or more underground nuclear explosions conducted within an area delineated by a circle having a diameter of 2 kilometers and conducted within a total period of time that did not exceed 0.1 second.
TNT Equivalent
A measure of the energy released in the detonation of a nuclear (or atomic) weapon, or in the explosion of a given quantity of fissionable material, expressed in terms of the mass of TNT which would release the same amount of energy when exploded. The TNT equivalent is usually stated in kilotons or megatons. The basis of the TNT equivalence is that the explosion of 1 ton of TNT is assumed to release 109 calories of energy.
Thermal Energy
The energy emitted from the fireball as thermal radiation. The total amount of thermal energy received per unit area at a specified distance from a nuclear explosion is generally expressed in terms of calories per square centimeter.
Thermal Radiation
Electromagnetic radiation emitted (in two pulses from an air burst) from the fireball as a consequence of its very high temperature; it consists essentially of ultraviolet, visible, and infrared radiations. In the early stages (first pulse of an air burst), when the temperature of the fireball is very high, the ultraviolet predominates; in the second pulse, the temperatures are lower and most of it is in the visible and infrared regions of the spectrum.
Thermonuclear
An adjective referring to the process in which very high temperatures are used to bring about the fusion of light nuclei (hydrogen), with the accompanying liberation of energy. A thermonuclear bomb is a weapon in which part of the explosion energy results from thermonuclear fusion reactions. The high temperatures required are obtained by means of a fission explosion.
See; Fusion.
Thermonuclear weapon
A nuclear weapon in which fusion of light nuclei, such as deuterium and tritium, contributes the main explosive energy. The high temperatures required for such fusion reactions are obtained by means of an initial fission explosion. It is also referred to as a hydrogen bomb.
See; Fusion.
Threshold Test Ban Treaty (TTBT)
This treaty between the United States and the former Soviet Union prohibits underground nuclear weapon tests having a yield exceeding 150 kilotons.
Ton
The energy of a nuclear explosion that is equivalent to the explosive power of 1 ton of TNT. (The yield of a nuclear device is a measure of the amount of energy released when it explodes. It is stated in terms of the quantity of TNT that would produce the same amount of explosive energy.) By definition, 1 ton is equivalent to 109 (E9) calories.
Tower
A type of atmospheric test in which a nuclear device was mounted near the top of a steel or wooden tower and exploded in the atmosphere 10 ft or more above the ground.
Transmutation
A process of converting one element to another by irradiating or bombarding it with radioactive particles.
Transuranic
Any element whose atomic number is higher than that of uranium. All transuranic elements are produced artificially and are radioactive.
Treaty of Bangkok (Treaty on the Southeast Asian Nuclear-Weapon-Free-Zone)
The treaty prohibits the development, manufacture, acquisition, or testing of nuclear weapons anywhere within the region. It also prohibits the transport of nuclear weapons through the region. Signatories also undertake to enact International Atomic Energy Agency safeguards and to refrain from dumping at sea, discharging into the atmosphere, or burying on land any radioactive material or waste.
Treaty of Pelindaba (Treaty on the African Nuclear-Weapon-Free-Zone)
This treaty prohibits the research, development, manufacturing, stockpiling, acquisition, testing, possession, control, and stationing of nuclear explosive devices in the members' territory. The treaty also prohibits the deposit of radioactive waste originating from outside the continent within the region. Under the treaty, signatories are required to put all their nuclear programs under International Atomic Energy Agency safeguards. The treaty also provides for the establishment of the African Commission on Nuclear Energy (AFCONE), which will supervise treaty implementation and ensure compliance.
Treaty of Rarotonga (Treaty on the South Pacific Nuclear-Weapon-Free Zone)
This treaty prohibits the testing, manufacturing, acquiring, and stationing of nuclear explosive devices in any member's territory. The treaty prohibits dumping radioactive wastes into the sea. In addition, the treaty requires all parties to apply International Atomic Energy Agency safeguards to all their peaceful nuclear activities.
Treaty of Tlatelolco
This treaty created a nuclear-weapon-free zone in Latin America and the Caribbean. The Treaty of Tlatelolco was the first international agreement that aimed at excluding nuclear weapons from an inhabited region of the globe. The member states accept the application of International Atomic Energy Agency safeguards for all their nuclear activities to assist in verifying compliance with the treaty. The treaty also establishes a regional organization, the Agency for the Prohibition of Nuclear Weapons in Latin America (OPANAL), to help ensure compliance with its provisions.
Triad
The traditional nomenclature for the three components of U.S. and Soviet strategic nuclear forces-land-based intercontinental ballistic missiles; submarines-launched ballistic missiles; and strategic bombers.
The Trinity Test
In July of 1945, a test was needed of the implosion design. The test was located in an area known as the Jornada del Muerto (Journey of Death) in southern New Mexico. At 5:29:45 am mountain war time, a light described as "brighter than a thousand suns" filled the valley.
See; Gadget, Manhattan Project.
Tritium
A radioactive isotope of hydrogen having a mass of 3 units; it is produced in nuclear reactors by the action of neutrons on lithium nuclei.
See; Fusion, Isotope, Thermonuclear.
Tunnel
A type of underground test in which a nuclear device exploded within a horizontal drift mined into a mountain or mesa in a way that placed the burst point deep within the earth.
Underground
A test in which a nuclear device exploded in a tunnel, or near the bottom of a drilled or mined hole or shaft. Some underground nuclear tests were not designed to contain all radioactivity (e.g., cratering tests or safety experiments).
Underwater
A test in which a nuclear device was detonated underwater.
Uranium
A naturally occurring radioactive element with the atomic number 92, and an atomic weight of approximately 238. Two principle isotopes are uranium-235 (0.7 percent of natural uranium), which is fissile, and uranium-238 (99.3 percent of natural uranium), which is fissile only by fast neutrons. The half-life is 7.04 x 108years.
Uranium 235 (U-235)
Uranium 235 is used as an reactor fuel or for nuclear weapons; however, nuclear weapons typically use uranium that has been enriched to contain over 90% U-235.
Uranium enrichment
The process of increasing the percentage of Uranium 235 isotopes so that the uranium can be used as reactor fuel or in nuclear weapons.
Uranium Hexafluoride (UF-6)
Uranium Hexafluoride gas is made from yellowcake and is then used as a feed material in the uranium enrichment process.
Vela Uniform
A U.S. Department of Defense program designed to improve the capability to detect, identify, and locate underground nuclear explosions.
Vela Satellites
Vela was a series of 12 satellites developed for the U.S. Defense Advanced Projects Agency to detect nuclear detonations in the Earth's atmosphere. The satellites were launched (1963-70) in pairs from a single vehicle and placed 180 degrees apart, in circular orbits of about 111,000 km (69,000 mi) altitude.
Verification
The process of using mechanisms such as satellites, seismic monitoring, or on-site inspections, to collect data that demonstrates a party's compliance with an agreement or treaty.
Verification Experiment
A test on which the former Soviet Union exercised its right to verify under the terms of the Threshold Test Ban Treaty.
Warhead
The explosive part of a nuclear weapons system. Warheads consist of nuclear materials, conventional high explosives and related firing mechanisms.
Washout
The removal of radioactive particles from a nuclear cloud by precipitation when this cloud is below a rain (or snow) cloud.
Weaponization
The process of constructing a nuclear device, or testing its component parts separately or in a weapon model, to validate its design.
Weapon Debris
The highly radioactive material, consisting of fission products, various products of neutron capture, and uranium and plutonium that have escaped fission, remaining after the explosion.
Weapons Effects
A type of atmospheric test conducted to evaluate the civil or military effects of a nuclear detonation on various targets, such as military hardware.
Weapons Related
A type of atmospheric test conducted for the purpose of testing a nuclear device intended for a specific type of weapon system.
Weapons-grade
Refers to nuclear material that is most suitable for the manufacture of nuclear weapons- e.g., uranium (U) enriched to 93 percent U-235 or plutonium (Pu) that is over 90 percent Pu-239. Crude weapons can be fabricated from lower-grade material.
Weapons-usable Material
Refers to nuclear material that is most suitable for the manufacture of nuclear weapons- e.g., uranium (U) enriched to 93 percent U-235 or plutonium (Pu) that is over 90 percent Pu-239. Crude weapons can be fabricated from lower-grade material.
WMD (weapons of mass destruction)
Nuclear, biological, or chemical weapons.
Weapons retirement
The process by which nuclear weapons are determined to be obsolete or unnecessary for national defense. A retired weapon or weapon system is no longer in an active status or deliverable, but may still be a fully functioning nuclear device.
X Rays
Electromagnetic radiations of high energy having wavelengths shorter than those in the ultraviolet region, i.e., less than 10-6 cm or 100 Angstroms. Materials at very high temperatures (millions of degrees) emit such radiations; they are then called thermal X-rays. As generally produced by X-ray machines, they are bremsstrahlung resulting from the interaction of electrons of 1 kilo-electron volt or more energy with a metallic target.
Yellowcake
A yellow powder that is mostly uranium. Yellowcake is produced by pouring crushed uranium ore into an acid which dissolves the uranium. The acid is drained from the crushed ore and dried, leaving a yellow powder called yellowcake.
Yield
The total effective energy released in a nuclear (or atomic) explosion. It is usually expressed in terms of the equivalent tonnage of TNT required to produce the same energy release in an explosion. The total energy yield is manifested as nuclear radiation, thermal radiation, and shock (and blast) energy, the actual distribution being dependent upon the medium in which the explosion occurs (primarily) and also upon the type of weapon and the time after detonation.
See; Equivalent Megatons, Kiloton, Megaton, Nuclear Weapon.