b'P ROVING THE P RINCIPLEChain reaction Cold War CriticalityA self-sustaining sequence of events A conflict over ideological differences The point at which a nuclear reactor is justoccurring when a neutron splits a fission- between the United States and the Soviet capable of sustaining a chain reaction.able atom (of uranium, for example) and Union and their respective allies lasting Critical massreleases sufficient neutrons to cause other from the late 1940s until early in theatoms to split in the same way. 1990s. It was carried on by means other The minimum amount of nuclear fuelChina Syndrome than sustained or direct military action. necessary to sustain a chain reaction.A figure of speech referring to a theoreti- Containment building Curiecal melting of nuclear reactor fuel which A safety feature of most commercial A measure of radioactivity, a curie is thatwould occur upon a loss of coolant to the nuclear reactor power plants. The airtight quantity of material that decays at a ratefuel. The fuel would melt, penetrate the building, typically engineered to contain of 3.7x10 10 disintegrations per second.reactor vessel, drop to the concrete floor gases and pressures that might be D&Dof the building, and reach the soil below. released in an accident, houses the reac-The phrase comes from the expression tor, pressurizer, coolant pumps, and other An abbreviation for decontaminationdig a hole all the way to China, a fanta- equipment. and decommissioning, particularly of asy of (American) children who believe Control rod building or structure that once housedChina to be on the opposite side of the active nuclear activities and may haveglobe from their own playground. A device within a nuclear reactor made of been contaminated in the process.Chicago Pile-1 materials which absorb neutrons. Control Historic uses of the term may also haverods help dampen or permit the reactors referred to dismantling or demolish-The name of the first nuclear reactor to chain reaction. ing.go critical, so called because graphite Contamination, radioactive Decontaminateblocks were piled upon each other to con-struct the reactor. Unintentional or undesirable contact of a A process removing radioactive materialsCladding person, object, or material with radioac- from a person, place, or object.tive substances. DecayThe outer layer of metal over the fission- Control roomable material in a nuclear fuel element, The spontaneous ejection of particles bytypically aluminum or zirconium. The operating center of a nuclear reactor radioactive materials. Synonym forCladding promotes the transfer of heat from which the reactor is operated and radioactive disintegration.from the fuel to the coolant and contains monitored. Depleted uraniumfission products and activation products Coolantwithin the fuel element. Uranium that, through the process ofCold run In a nuclear reactor, a gas or fluid (such enrichment, has been stripped of most ofas water or liquid metal) sent past the the uranium-235 it once contained. It hasA test of a chemical process and equip- fuel elements to collect and carry away more uranium-238 than natural uranium,ment using non-radioactive materials. the heat generated by the nuclear reac- but is referred to as depleted.Cold shutdown tion. DoseA reactor condition in which the coolant Core A specific amount of ionizing radiation or atemperature has been reduced to 200 F That part of the nuclear reactor consisting toxic substance absorbed by a living being. or below, the pressure has been reduced of the fuel and control elements, theto atmospheric pressure, and the chain coolant, and the vessel containing these.reaction has stopped.308'