Definition of "actinide" []

• Any of a series of chemically similar, radioactive elements with atomic numbers ranging from 89 (actinium) through 103 (lawrencium). (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "They do, however, create actinide-free waste that is much less radioactive, with a half-life of a couple of hundred years (as opposed to tens of thousands of years for LWR waste)."
• "In other words, the fissile material produced by these reactors is recycled at least twice until the final waste results in an actinide-free byproduct that has a half life of about 200 years."
• "Depending upon which chemist you ask, rare earth elements consist of either: the so-called lanthanide series (elements having atomic numbers from 57 [corresponding to lanthanum] to 71 [corresponding to lutetium]) or the actinide (elements 89 to 103) and lanthanide series."