Definition of "atomic pile" []

• An early type of nuclear reactor whose core consisted of layers of graphite block interspersed with uranium, designed to create a sustained fission reaction. (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.

• "I'd looked into the heart of the uranium atomic pile through a heavily leaded glass-inspection port and seen the indescribable unearthly radiance of it, a nightmarish coalescence of green and violet and blue, the new "dreadful light" of mankind."