On Wed, 20 Dec 2006 09:56:40 -0600, "Gig 601XL Builder"
wrDOTgiaconaATcox.net wrote in :

Instead of a conventional fission
reactor, it is focusing on a type of power generator called a quantum
nucleonic reactor. This obtains energy by using X-rays to encourage
particles in the nuclei of radioactive hafnium-178 to jump down several
energy levels, liberating energy in the form of gamma rays. A nuclear UAV
would generate thrust by using the energy of these gamma rays to produce a
jet of heated air.

Interesting.

http://en.wikipedia.org/wiki/Hafnium

So, it seems hafnium-178m2 is radioactive with a half-life of 31
years, equivalent to cesium-137. Are the byproducts subsequent to
X-ray bombardment radioactive also?

It would appear that the whole DARPA hafnium fandango is bunkum:


Conflicting Results on a Long-Lived Nuclear Isomer of Hafnium Have
Wider Implications
http://www.physicstoday.org/vol-57/iss-5/p21.html



Scary Things Come in Small Packages
The Pentagon says what Carl Collins is cooking up in his lab could
power the most devastating bomb this side of a nuke. A long list
of heavyweight physicists calls that dangerous bunk.

http://www.washingtonpost.com/ac2/wp...&notFound=true



Ultimately, even the mavens’ attempts to repeat their earlier
favorable experiment were disappointing. In time – perhaps too
much time, it was only last year – annoyed scientists and aghast
politicians delivered a coup de grace. Bang! The lifeless body of
Pentagon-funded hafnium isomer research slumped to the laboratory
floor, its white coat sullied by Texas dust and latté spills. It
had breathed its last. Maybe.

http://agonist.org/20060709/a_journe...c_underw orld