|4/5/2017 by mdc|
|Reuben Brewer opines that uranium you might think is a rare element. It is 500 times more common than gold. There are traces of uranium in granite (ave. 4 parts per million), which makes up 60% of the Earth crust. In other words, uranium is pretty much all around us and there is little risk of radiation poisoning. That is because uranium is only slightly radioactive. |
Only about 0.7% of uranium (the ore and produced yellowcake) is what is known as fissile, or capable of undergoing fission (that is the process that produces heat that boils the water that is flashed to steam into generators that produce electricity. So only a small amount of uranium is actually capable of fission. That is because uranium comes in two isotopes, uranium-235 (U-235) and uranium-238 (U-238). The type of uranium used in nuclear reactors is uranium-235, but it needs to be concentrated to at least 3.5% to 5%. To get it up from its 0.7% concentration, uranium (the produced yellowcake) has to be enriched to produce small pellets that are placed in assemblies that are 1nserted into nuclear reactors.
That requires uranium to be turned into a gas so that U-235 can be concentrated relative to U-238. That process involves centrifuges that spin the gas and take advantage of the 1% mass difference between the two isotopes of uranium to separate them.
Weapons-grade uranium has to be concentrated starting at 20% U-235. The bomb dropped on Hiroshima was 80% enriched uranium. The U-238 isotope remaining is known as depleted uranium. This used to harden the tips of bullets and larger shells used in tanks, etc., all because the greater mass, the greater penetrating power.
Cameco Corp., the world largest publicly traded uranium miner, sold 31.5 million pounds of yellowcake in 2016. Typically, some 44 million kilowatt-hours of electricity are produced from 2,000 pounds of yellowcake, or from 20,000 tonnes of black coal or 8.5 million cubic meters of natural gas.