U238 (depleted uranium) reactor

Depleted Uranium, its heavy, its hard to dispose of, it makes good armor piercing shells, and we have piles of it sitting around from nuclear reactors and mines waiting to be processed. Despite us having so much of the stuff, the fact that it is unsuitable for use as weapons grade fissile material resultes in research into its potential limited to it being incorperated into anti-tank rounds, and the fact that this stuff has the potential to power a reactor seems to have slipped the scientific community until now.
A reactor burning depleted uranium cannot produce any weapons grade material, we can just build one and shove it over to Iran and say "look, this stuff burns cheaper fuel, gives more power, has almost no risk of a catastropic meltdown no matter how incompetent your operators are, and is way better in every respect except that you cant make a bomb with it. If your nuclear intentions are peaceful, replace your reactors with this."
As for the reactor design itself, there is already one being looked into called a traveling wave reactor which will use enriched uranium to start a self sustaining reaction in a field of depleted uranium using neutrons released from the enriched reaction to enrich/destabalize the surrounding depleted uranium in order to keep the reaction going. Once fueled, such a reactor could run for decades before the entire field of depleted uranium is brunt, and its output will only increase unless checked for the "burning front" will increase in legnth as the reaction spreads. Despite the increased output, the fuel starts out unsutable for weapons and never actually gets close to a critical mass except when the reaction is first started, so although the risks of a meltdown are there if some idiot turned off the cooling system, the chances of the reactor turning into a bomb are slight.
Another design I was going to propose was slightly more complex and involves a series of faceleted and interconnected chamebers lined with depleted uranium, one central chanber will have a small neutron fuse like the ones used in bombs, but neutrons from the fuse will not be focused onto one point like in bombs but released to bounce along the chamber whose geometrical design allows the escape of neutrons into a similar neighboring chamber. The neutrons arnt actually "bouncing", rather, they are exciting and causing fissile reactions whenever they hit the sides of a chamber, causing more neutrons to be released.