Despite being the main fuel for nuclear reactors, most people know close to nothing about uranium. This has led to a slew of misconceptions about this heavy metal. To help clear things up, we thought it would be useful to have a short discussion on what uranium is and how it’s used for nuclear fuel. If this is something that you’re interested in learning more about, read on as we break down everything you need to know about uranium and the vital role it plays in nuclear fuel.
What Is Uranium?
Uranium is a radioactive element that occurs naturally in low concentrations. When a particular element has 92 protons in its nucleus, it’s called uranium, the heaviest naturally occurring element. Uranium is very dense, nearly twice as dense as lead.
Uranium is naturally radioactive, which means that atoms of uranium decay by emitting particles and energetic radiation, a process known as radioactive decay. Uranium-238 decays by emitting an alpha particle, a subatomic particle consisting of two protons and two neutrons. The half-life of U-238 is about 4.5 billion years, which means it doesn’t undergo radioactive decay very often. Uranium is not very radioactive because it has such a long half-life. Three additional uranium isotopes are not naturally present but can be produced by nuclear reactions. These are U-232, U-233, and U-236. Uranium-233 is made by bombarding thorium with neutrons in a nuclear reactor. Like the natural uranium isotopes, uranium isotopes undergoing decay also release energy in the process.a
What Is Uranium Enrichment?
Most nuclear power reactors use the isotope uranium-235 as fuel, but it makes up only about 0.7% of the natural uranium mined, so it must be enriched to about 3%-5% concentration. The CANDU reactors from Canada use natural uranium instead, so they don’t have to enrich it at all.
The enrichment process begins by converting uranium oxide, a solid compound, into another compound with a different chemical structure. This new compound is called uranium hexafluoride, and it is a gas at relatively low temperatures. The gas is fed into centrifuges, with rapidly-spinning vertical tubes that separate uranium-235 from the slightly heavier uranium-238 isotope. The centrifuges separate the uranium into two streams: the enriched stream has a high concentration of uranium-235; and the depleted stream has a lower concentration of this isotope, but still enough to be considered nuclear waste. This waste is called depleted uranium
How Is Nuclear Fuel Made?
Enriched uranium is transported to a fuel fabrication plant, where it will be processed into uranium dioxide powder. This powder is pressed into small pellets and heated to make hard ceramic particles, or “briquettes.” The briquettes are then loaded into thin tubes known as fuel rods, which are then grouped together to form fuel assemblies. Around 18 million fuel pellets are required to produce one nuclear reactor’s worth of electricity. However, the amount of coal required to produce the same amount of electricity is more than two and a half times the amount needed for a nuclear power plant.
We hope this article proves to be useful when it comes to helping you gain a better understanding of the vital role that uranium plays in nuclear energy. While it may seem complicated, the information that we’ve laid out above should help give you good foundational knowledge on this subject. Feel free to reread this article if you ever need a quick refresher on this subject.
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