The uranium that we use for all of our nuclear plants is about 65,000 tons per year. This is about 10% of world electricity. 40% of world electricity is from coal. The word uses 7.3 billion tons of coal per year. We use over 100,000 times more coal for 4 times as much power. The coal is burned and puts three times as much CO2 into the air. The burning adds two oxygens to the carbon. There are a hundred millions of tons of ash, soot and particulates. The small particulates get into the lungs and cause lung disease and heart disease. This contributes to the early death of 4 million people per year.
The uranium “waste” sits in cooling tanks for a few years and can be placed into metal boxes with walls that have neutron-absorbing boron.
The main disadvantage of fast-neutron reactors is that they are costly to build and operate, and are not likely to be cost-competitive with thermal-neutron reactors unless the price of uranium increases dramatically.