Last I recall there was already a craft with nuclear propulsion launched a while back, not to mention a good share of nuclear powered satellites are already up in orbit. Space is full of radioactive particles, so it's not a big deal.
I do agree with Rei. NASA needs to fund research a little better at this time, instead of trying to waste available resources on useless missions. If they would just push technology research just a few years, they could have a lot of options to choose from to accomplish their goals a lot more efficiently. I realize that by going to Moon, it could increase public interest and potentially gain additional funding for technology research related projects, yet it can also backfire in many ways which could set NASA back later on.