Because of my interests in war and history, I track military intelligence sites like GlobalSecurity.org where I found this:

"A leaked Pentagon document has confirmed that the US is considering the introduction of a new breed of smaller nuclear weapons designed for use in conventional warfare. Such a move would mean abandoning global arms treaties." [GlobalSecurity.org]

According to the article, US military officials and nuclear scientists met last August to discuss new breed of nukes.  Among them: sub 5 kiloton nukes for bunkers and enhanced radiation nukes (aka neutron bomb).  In short, Bush and Rumsfeld wants practical nukes, nukes we can use.  While at it, why not build Clean Bombs that can remove unwanted people and rust at the same time?  Sure would be handy around pipelines.