Herndon's page regarding Helium-3:
"One thought to consider. Three of the four giant gaseous planets, Jupiter, Saturn, and Neptune, presently radiate nearly twice as much energy into space as they each receive from the Sun. Their internally generated energy, presumably from planetary-scale nuclear fission reactors, is responsible for their turbulent atmospheres. By contrast, Uranus radiates little or no internally generated energy and has a quiescent, featureless appearance. Has Uranus’ nuclear reactor already reached the end of its lifetime?"
http://www.nuclearplanet.com/helium3_evidence.htm