Actually, unless you are really bent out of shape about radiation in ANY amounts, there is no reason an Orion could not be built that could be flown with little permanent environmental impact. The world detonated hundreds of open-air nukes during the early years of bomb testing, and whaddaya know, we're all still here. Properly designed, a bomb can be made to minimize radioactive particles, and detonated in mid-air, the fallout generated by ground bursts would be minimized as well.

Obviously, a very remote area would have to be chosen for launch, not only to bring exposure to an absolute minimum, but to reduce possible electromagnetic pulse side effects which I think could be more of a problem than the radioactivity. Personally, I'd design the thing for ocean launch.

Orion is not the system one would choose for routine access to space over many years. But for a few launches to place a huge infrastructure in orbit or beyond, I see it as a possibility.

There are also designs for very large chemical rockets, like Bob Truax's 40 million lb. Seadragon, which have potential for large payloads as well. Maybe to place an Orion into space before the nuclear propulsion system is fired...