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Powered by solar energy, Juno is planned to orbit Jupiter for a prime mission of one year on a trajectory to avoid much of the harsh radiation that surrounds the Jovian system. This issue often plagued NASA's Galileo probe, which orbited Jupiter from 1995 until 2003.

http://spaceflightnow.com/news/n0506/05juno/

Though the details of the technology required to make a solar powered probe at Jupiter's distance feasible are missing (does that mean they HOPE to have such technology ready by the time Juno launches? Is this kind of like hoping we'll know how to have controllable fusion in 20+ years?), it does seem that is the way they want to go.

As for the anti-nuke groups' likely response to this, I remember quite well the Cassini brouhaha of 1997. I recall how many of them knew so little about astronomy and nuclear technology - one guy didn't know that Venus had an atmosphere and feared that Cassini would somehow zip out of Saturn's gravitational pull and come hurtling back to Earth! - and likely cared about the subjects that I for one am not going to give them any more concern than such ill-informed and paranoid reactions require.

A friend who went to an anti-Cassini/Nuke rally in Cambridge recalled how he was told they didn't want the facts he was presenting on Cassini's RTGs, they just knew it was nuclear-powered and therefore dangerous and that was that! I doubt any of them even knows or cares about all the wonderful things Cassini has sent back to humanity about Saturn and its realm - and from the safety of 800 million miles from Earth, no less.