[klyrs]

That's not quite what I'm picturing (and let's be honest, the idea is silly). That page describes capturing the heat of a nuclear reactor, converting it to electricity, and then using that electricity to force ions out of a thruster. I'm saying, the radiation itself has momentum; don't bother with the contraption.

[abecedarius]

Yes, just thought you might not know of the related more practical version, and you might be pleased to encounter it.