The nuclear fuel cycle consists of nine stages that are necessary in order to produce electricity from uranium in nuclear power reactors. The cycle starts with the mining of uranium and eventually ends with nuclear waste disposal. Today I’m going to summarize the first four steps in the nuclear fuel cycle.
Step 1: Uranium Mining. I already wrote about uranium in Know Your Business Part 1. It is actually a very common, mildly radioactive, metal found throughout the world and, in fact, it is just about as common as tin! Kazakhstan, Canada, and Australia are the top producers, in order, of uranium with the US ranking 8th in the world. Uranium is mined via open pit, underground and through insitu recovery.
Step 2: Uranium Milling. The milling is commonly done near or on location of the uranium mine. In conventional mining, the mined uranium ore is crushed and chemically treated to separate the uranium In solution mining, the uranium ions are separated through the ion exchange process. Uranium oxide U308, a yellow powder called yellow cake, is the result from both milling processes. The uranium concentration in yellow cake is raised to more than 80%. The yellow cake concentrate is shipped to a conversion facility after milling.
Step 3: Conversion. At the conversion facility, the yellow cake is converted to uranium hexifloride gas (UF6) in order to increase the concentration of the U-235 isotope. The U-235 isotope is what creates the heat energy released in a nuclear reactor (fission) and is only 0.7% of the total amount of isotopes found in natural mined uranium – the U-238 isotope makes up the remaining 99.3%! The UF6 gas is drained into large cylinders where it solidifies and then is shipped to an enrichment plant. The only conversion plant in the US is located in Metropolis, KY.
Step 4: Enrichment. At the enrichment plant, the uranium is enriched by introducing the UF6 into centrifuges where the heavier isotopes are pushed to the centrifuge walls. Enrichment increases the proportion of the U-235 isotopes or uranium atoms that can be split by fission to release energy that is used to produce electricity. There is currently only one enrichment plant operating in the US and is located in Eunice, NM.
Tomorrow, hopefully, I will cover the next five steps of the Nuclear Fuel Cycle.
References for this post:
IAEA – The Nuclear Fuel Cycle
USNRC – Stages of the Nuclear Fuel Cycle
USNRC – Uranium Conversion
USNRC – Urnaium Enrichment