[logfromblammo]

The risk is that in a catastrophic launch failure (read: exploded rocket), the radioactive materials could be dispersed downrange.

The solution--if that's really a problem--is to use the same escape systems used for crewed launches to eject the nuclear fuel with a parachute and emergency beacon, and keep it all inside a durable shielded container until the craft needs to start up the nuclear engine.

[GlenTheMachine]

Effectively, they already do that. Although the United States doesn't launch reactors, we do on occasion launch radioisotope thermoelectric generators (RTGs). These use a core of sub-critical plutonium surrounded by thermocouples, which turn the heat into electricity. These are used for probes going to the outer solar system, where solar panels aren't effective enough.

Anyway - there is certainly a concern with the plutonium in RTGs being dispersed by a launch failure. The engineering that goes into designing the protective system for RTGs is extensive; they each have their own miniature heat shield, and are surrounded by iridium and carbon blocks. Tests show that they can indeed survive the explosion of the launch vehicle.

[m4rtink]

IIRC long ago a US RTG ended up in the ocean due to launch failure, only to be recovered and sussessfully re-launched on a new satellite.

These things are tough! And also expensive, so you might as well reuse them once they shrug off the rocket exploding under them.

[mlindner]

Except that's not a big problem. A non-activated reactor just contains enriched uranium. Uranium is dug out of the ground and you can buy it on amazon and chemically concentrate it yourself. It's safe to hold and handle (wash your hands afterwards so you don't eat particles) and store in your house even. (In the US this is all legal.)

Reactors only become dangerous after you activate them and short lived isotopes are created that also happen to be types that are bioavailable, like cesium-137 and strontium-90 which the body will take up and store inside the body.

[yellowapple]

> Uranium is dug out of the ground and you can buy it on amazon and chemically concentrate it yourself.

Well now I know what I'm putting in all my nieces' and nephews' stockings this year: https://www.amazon.com/Images-SI-Uranium-Ore/dp/B000796XXM/

[logfromblammo]

Reactor fuels or RTG cores are a bit more dangerous than ore.

A properly designed reactor requires the fuel to be in the core to sustain a chain reaction, and neutron activation of other elements in the reactor does not occur until the reaction has started. Thus, a rocket explosion would not cause a criticality event. The worst that would happen would be dispersion of nuclear fuel to a place where someone might handle it without its transport-safety shielding. Which still wouldn't be that bad.