Fair enough. Now, which level of government are you going to use to do it? If you're going to have your state do it, then all you need is for the legislature to enact that prohibition and make the necessary provisions to enforce it. If you want the national government to do it, then you need to enumerate a power for that, because there is currently no "dangerous substances" power granted to Congress by the States, and enumerated in the Constitution.
And under what Constitutional power do we have a right to ban fissile material? You tell me.