Article:
The U.S. Is Saving Nukes So It Can Blow Up Asteroids
By Tim Fernholz - The Atlantic - October 1, 2014
http://www.govexec.com/defense/2014/10/us-saving-nukes-so-it-can-blow-asteroids/95621/

Official Government PDF:
NUCLEAR WEAPONS - Actions Needed by NNSA to Clarify Dismantlement Performance Goal
http://www.gao.gov/assets/670/662840.pdf

Excerpt from the government PDF (Page 46 of PDF, page 41 of document numbering):
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For potential use in planetary defense against earthbound asteroids. NNSA officials told us that CSAs associated with a certain warhead indicated as excess in the 2012 Production and Planning Directive are being retained in an indeterminate state pending a senior-level government evaluation of their use in planetary defense against earthbound asteroids. While NNSA has declared these CSAs to be excess and, until March 2013, had scheduled them for disassembly beginning in fiscal year 2015, the national labs’ retention letter has also characterized the CSA associated with this warhead as an “irreplaceable national asset.” The WDD program is coordinating NNSA’s evaluation of their use in planetary defense with the support of LLNL, LANL, and Y-12.

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