What’s Nuclear About A Football?Whose nuclear launch button is bigger? There has been a serious kerfuffle in the news about buttons and their relative size. Specifically, nuclear launch buttons. Kim Jong-un, the leader of North Korea, flatly stated that a nuclear button is on his desk at all times. “It’s not a mere threat but a reality that I have a nuclear button on the desk in my office.” …
metathesisFind new words to share every day with Dictionary.com's Word of the Day. Discover the definition, pronunciation, and origin of uncommon words plus more!
- nuclear physics,
- nuclear pore,
- nuclear power,
- nuclear radiation,
- nuclear reaction,
- nuclear regulatory commission,
- nuclear rna,
- nuclear spindle,
- nuclear stain,
- nuclear test ban treaty
Origin of nuclear reactor
First recorded in 1940–45
Also called nuclear pile.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for nuclear reactor
From nuclear-reactor makers to dictators, see who else BM has worked for.
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
A device used to generate power, in which nuclear fission takes place as a controlled chain reaction, producing heat energy that is generally used to drive turbines and provide electric power. Nuclear reactors are used as a source of power in large power grids and in submarines.
A Closer Look
A nuclear reactor uses a nuclear fission chain reaction to produce energy. The cylindrical core of a reactor consists of fuel rods containing pellets of fissionable material, usually uranium 235 or plutonium 239. These unstable isotopes readily split apart into smaller nuclei (in the fission reaction) when they absorb a neutron; they release large quantities of energy upon splitting, along with more neutrons that may be absorbed by the nuclei of other isotopes, causing a chain reaction. The neutrons are expelled from the fission reaction at very high speeds, and are not likely to be absorbed at such speeds. Moderators such as heavy water are therefore needed to slow the neutrons to a speed at which they are readily absorbed. The fuel rods contain enough fissionable material arranged in close enough proximity to start a self-sustaining chain reaction. To regulate the speed of the reaction, the fuel rods are interspersed with control rods made of a material (usually boron or cadmium) that absorbs some of the neutrons given off by the fuel. The deeper the control rods are inserted into the reactor core, the more the reaction is slowed down. If the control rods are fully inserted, the reaction stops. The chain reaction releases enormous amounts of heat, which is transferred through a closed loop of radioactive water to a separate, nonradioactive water system, creating pressurized steam. The steam drives turbines to turn electrical generators.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.