For the convenience of the reader and for purposes of comparison with this report, we have provided some definitions of key terms from the 2010 CTBT National Intelligence Estimate (CTBT NIE, 2010). Drawing from the CTBT NIE and its own knowledge, the committee has also provided definitions of nuclear weapon classes.
Understanding Key Terms in This Estimate
Nuclear test monitoring refers to the persistent global surveillance of underwater underground, atmospheric, and space environments for nuclear explosions. The scientific and monitoring communities do not use the terminology describing technical monitoring tasks consistently, making it necessary to take extra care when comparing findings between different organizations. In this Estimate, we use the following definitions.
Detection is the determination that an event of interest has occurred at a given location. Detection alone does not indicate whether an event was an explosion or if so, whether it was nuclear.
Identification is the determination that an event was an explosion. During the identification process, data are screened to discriminate among natural events, explosive events, and indeterminate events. Identification alone does not determine whether an event is nuclear.
Characterization is the determination that an explosion was nuclear in nature as determined by the collection of nuclear explosion debris or detection of unique signatures by satellite.
Attribution is the determination of the state or actor responsible for a nuclear explosion.
The threshold is the minimum yield at which a statistically significant percentage of all events can be detected, identified, or characterized, with technical monitoring systems.
By high confidence we mean detecting, identifying, or characterizing at least 90 percent of the events with yields above a certain threshold.
In a fully coupled underground nuclear test, the explosive energy fully interacts with the surrounding medium (e.g., rock or water), maximizing the seismic waves detected by our networks.
Nuclear Weapon Classes
A nuclear warhead or bomb is a nuclear explosive device that has been weaponized for delivery.
A fission device is a supercritical assembly of fissile material that disassembles explosively. The fission reactions produce the nuclear explosive yield of the device.
A boosted-fission device uses a fission explosion to cause a small amount of deuterium and tritium gas to undergo nuclear fusion. This fusion produces energy and extra neutrons that cause more fissions in the fissile material, which results in a greater explosive yield and a more efficient use of the fissile material. The amount of fusion yield produced in a boosted-fission device is a small fraction of the weapon’s total yield, but the fusion “boosts” the fission yield.
A thermonuclear device uses a fission or boosted-fission device as a “primary stage” that produces the energy required to implode a separate “secondary stage.” The secondary stage uses both fusion and fission reactions to generate nuclear explosive yield.
A neutron bomb is a weapon designed to increase lethality to personnel and ballistic missile warheads by increasing the weapon’s output of higher energy neutrons.
An electromagnetic pulse (EMP) weapon is designed to create strong electromagnetic fields through the interaction of gamma rays with the ions in the atmosphere and any conducting materials with which the radiation comes in contact.