So the way around the radioactive accident problem is fairly well solved now. A reactor would be assembled and activated on orbit after the parts were carefully shipped to that the components could not easily disintegrate on launch.

Others here have taught me that he urgency here comes out of the undefined acronym, which was "Solar Gravitational Lens." That is a point--the focus of the lens made by the sun--somewhere 3 times farther out than our current farthest spacecraft, the Voyagers. It's taken them almost 50 years to get that far so they'll want to reach that focus ten times faster than our current vehicles, then it has to slow and maneuver around that point.