Uranium fuels were never deployed because of cost or safety, they were deployed because various militaries funded the technology for use a) producing plutonium

Uranium fuels were never deployed because of cost or safety, they were deployed because various militaries funded the technology for use a) producing plutonium for weapons, and b) producing energy for large Navy customers. Civilian nuclear energy based on the uranium fuel cycle is a spin off from a warfighter's R&D project. Compare that with the thorium fuel cycle which does not produce weaponizable byproducts.