292 



Megawatt-day per ton— A unit that expresses the burnup of nuclear fuel in a 

 reactor; specifically the number of megawatt-days of heat output per 

 metric ton of fuel in the reactor. 



Metric ton — loot) kiln-nuns (2205 pounds). 



Moderator— A material, .such as water, heavy water, or graphite, used in a 

 nuclear reactor to slow down high-velocity neutrons emitted by fission- 

 ing atoms, thus increasing the likelihood of capture to cause further 



fissi 

 Natural uranium— Uranium as found in nature, containing 0.7% uranium-23o, 



99.39! of uranium-238 and a trace of uranium-234. It is also called 



normal uranium. 

 Normal uranium — See natural uranium. 

 Nuclear power plant — Any device, machine, or assembly that converts nuclear 



energy into some form of useful power, such as mechanical or electrical 



power. 



Nuclear reactor — A device in which a fission chain reaction can be initiated, 

 maintained, and controlled. Its essential component is a core with fission- 

 able fuel. It usually has a moderator, reflector, shielding coolant and 

 control mechanisms. It is the basic machine of nuclear power. 



Nuclide— A general term applicable to all atomic forms of the elements. It is 

 not a synonym for "isotope." which properly has a more limited defini- 

 tion. Whereas isotopes are the various forms of a single element, undid, s 

 comprise all the isotopic forms of all the elements. 



Plutonium — A heavy, radioactive, man-made element of atomic number t>4. Its 

 most important isotope is fissionable plutonium-239, produced by neu- 

 tron irradiation of uranium-238. It is used for reactor fuel and in 

 weapons. 



Pressurized water reactor — A power reactor in which heat is transferred from 

 the core to a heat exchanger by water kept under high pressure to pre- 

 vent it from boiling. Steam is generated in a secondary circuit. 



Pu-239 — The isotope of plutonium of weight 239. 



Radiation — The emission and propagation of energy through matter or space 

 by electromagnetic waves, or by particles. Nuclear radiation is that 

 emitted from atomic nuclei in various nuclear reactions. 



Radiation standards — Exposure standards, permissible concentrations, rules for 

 safe handling, regulations for transportation, regulations for industrial 

 control of radiation and control of radiation exposure by legislative 

 means. 



Radioactive contamination — Deposition of radioactive material in any place 

 where it may harm persons, spoil experiments, or make products or 

 equipment unsuitable or unsafe. The presence of unwanted radioactive 

 matter. 



Radioactivity — The spontaneous decay or disintegration of an unstable atomic 

 nucleus, usually accompanied by emission of ionizing radiation. 



Source material— As defined in the Atomic Energy Act of 1954, any material. 

 e\c pt special nuclear material, which contains 0.05% or more of ura- 

 nium, thorium, or any combination of the two. 



Special nuclear material — As defined in the Atomic Energy Act o r 1954, this 

 term refers to plutonium-239, uranium-238, enriched uranium, or any 

 material artificially enriched in any of these substances. 



Toll enrichment A business arrangement whereby privately owned uranium 

 is enriched in uranium-235 content in government facilities upon pay- 

 iin m of a service charge. 



Tritium A radioactive isotope of hydrogen. It is man-made and is heavier 

 than deuterium. 



U-235, U-238 — Uranium of atomic weights 235 and 238, respectively. 



Uranium— A radioactive element with atomic number 92 and, as found in 

 natural ore-;, an average atomic weight of approximately 238. The two 

 principle natural isotopes of uranium are uranium-235 (0.7% of natural 

 uranium), which is fissionable, and uranium-238 (99.3% of natural 

 ii'-;. uimn > . w liich is Perl ile. 



Uranium hexafluoride — A volatile compound of uranium and fluorine. In ira^i ous 

 form, this is the process material Cor the gaseous diffusion and gas 

 centrifuge methods of enrichment. 



Wastes, radioactive Equipment and materials, from nuclear operations, which 

 are radioactive and for which there is no further use. Wastes are gen- 

 erally classified as high-level (having radioactivity concentrations of 

 hundr< ds to thousands of curies per gallon or cubic foot), low level (in 

 the range of 1 microcurie per gallon or cubic foot), or intermediate. 



