U- 235 is a fissile isotope, meaning that it can split into smaller molecules when a lower-energy neutron is fired at it. U- 238 has an even mass, and odd nuclei are more fissile because the extra neutron adds energy - more than what is required to fission the resulting nucleus.
When refined, uranium is a silvery white, weakly radioactive metal. When finely divided, it can react with cold water; in air, uranium metal becomes coated with a dark layer of uranium oxide. Uranium in ores is extracted chemically and converted into uranium dioxide or other chemical forms usable in industry.
According to the Union of Concerned Scientists, a nuclear bomb needs about 33 pounds (15 kilograms) of enriched uranium to be operational.
The primary difference is the atomic number: uranium has 92 protons, plutonium has 94 protons. Plutonium-239 is easier to fission than uranium-235, produces more neutrons per fission, and has a smaller delayed neutron fraction. So plutonium-239 makes a better reactor fuel and nuclear weapon.
Yet, the truth is, you can buy uranium ore from places like Amazon or Ebay, and you won't have to produce any special authorization to get it. The isotope that is used in bombs and reactors is Uranium-235, which is only about 0.72% of the natural uranium ore.
Enriching uranium from 1% to 20% is very difficult and requires a lot of infrastructure to produce quantities needed for weapons construction. The kicker is, that enriching from 20% to 90% is easier than getting to 20% in the first place.
It can be found almost everywhere in rock, soil, rivers, and oceans. The challenge for commercial uranium extraction is to find those areas where the concentrations are adequate to form an economically viable deposit. The primary use for uranium obtained from mining is in fuel for nuclear reactors.
Uranium milling
After mining, uranium ore is transported to a nearby mill for processing. The first step is to crush the ore and mix it with water so that it can move through a series of mill circuits. After crushing, the ore is treated with acid in large tanks, to separate the uranium from other minerals in the rock.U-235 is the main fissile isotope of uranium. The nucleus of the U-235 atom contains 92 protons and 143 neutrons, giving an atomic mass of 235 units. The U-238 nucleus also has 92 protons but has 146 neutrons – three more than U-235 – and therefore has a mass of 238 units.
Inhaling large concentrations of uranium can cause lung cancer from the exposure to alpha particles. Uranium is also a toxic chemical, meaning that ingestion of uranium can cause kidney damage from its chemical properties much sooner than its radioactive properties would cause cancers of the bone or liver.
As elements get very large the proton electrical repulsion effect becomes stronger and to be stable a nucleus needs extra neutrons to overcome this repulsion. Uranium 235 has 92 Protons and 143 Neutrons and as a member of the 'Actinide Series' of elements heavier than 88 Protons it is naturally radioactive.
Uranium-238, the most prevalent isotope in uranium ore, has a half-life of about 4.5 billion years; that is, half the atoms in any sample will decay in that amount of time. If inhaled or ingested, however, its radioactivity poses increased risks of lung cancer and bone cancer.
From a chemical point of view, uranium is a heavy metal and about as toxic as lead. Touching it won't really do anything to you. Ingesting or inhaling it would be bad, but as long as you don't have any cuts on your hands and wash them when you're done you're unlikely to have any problems.
The reason why Uranium 238 is not fissile is because upon absorption of a thermal neutron, the binding energy released by U-238 is not greater as compared to the critical energy required to carry out the fission.
Here is the complete decay series of this isotope: Uranium-235 →Thorium-231 → Protactinium-231 →Actinium-227 →Thorium-227 →Radium-223 →Radon-219 →Polonium-215 →Lead-211 →Bismuth-211 →Thallium-207→ Lead-207 (stable)
Anyway, it works out to about $1000 (give or take, and it varies considerably - SWU prices are about half what they were a few years ago, for example) per kg of 5% enriched Uranium. By extension, you could buy 20kg of that for about $20,000, and have 1kg of U-235 (unhelpfully mixed with 19kg of U-238, but still).
Why a uranium release can be harmful
That contact--and therefore that exposure--can occur when you breathe, eat, or drink the contaminant, or when it touches your skin. However, since uranium is radioactive, you can also be exposed to its radiation if you are near it.Inhaling large concentrations of uranium can cause lung cancer from the exposure to alpha particles. Uranium is also a toxic chemical, meaning that ingestion of uranium can cause kidney damage from its chemical properties much sooner than its radioactive properties would cause cancers of the bone or liver.
Both the zone and the former power plant are administered by the State Agency of Ukraine on Exclusion Zone Management. The three other reactors remained operational after the accident but were eventually shut down by 2000, although the plant remains in the process of decommissioning as of 2020.
That daily uranium consumption isn't nearly enough to be harmful, especially since your body has a hard time absorbing uranium as it is [source: Keith et al]. A small amount of uranium will stay in your bones anywhere from months to years after ingestion, but eating uranium is much less toxic than inhaling it.
During 2019, 22% of the uranium delivered was purchased under spot contracts at a weighted-average price of $27.89 per pound.
No, in fact, until about the last 10 or 15 years, it was very cheap but even now it's not outrageously expensive. U238 (the most common isotope) costs about $5 a pound, or $12 per kilogram. It is essentially a waste product from weapons manufacture.
Plutonium is a radioactive metallic element with the atomic number 94. It was discovered in 1940 by scientists studying how to split atoms to make atomic bombs. Plutonium is created in a reactor when uranium atoms absorb neutrons. Nearly all plutonium is man-made.
In May 2010, a deal with Brazil and Turkey was announced and submitted to the IAEA whereby Iran would ship 1200 kg of 3.5% enriched uranium to Turkey, and then receive 120 kg of 19.75% enriched uranium fuel elements for the TRR in return from the so-called Vienna Group, comprising the IAEA, USA, Russia and France.
While 238U is minimally radioactive, its decay products, thorium-234 and protactinium-234, are beta particle emitters with half-lives of about 20 days and one minute respectively.
Anyway, it works out to about $1000 (give or take, and it varies considerably - SWU prices are about half what they were a few years ago, for example) per kg of 5% enriched Uranium. By extension, you could buy 20kg of that for about $20,000, and have 1kg of U-235 (unhelpfully mixed with 19kg of U-238, but still).
And just like any fuel, it gets used up eventually. Your 12-foot-long fuel rod full of those uranium pellet, lasts about six years in a reactor, until the fission process uses that uranium fuel up.
According to the NEA, identified uranium resources total 5.5 million metric tons, and an additional 10.5 million metric tons remain undiscovered—a roughly 230-year supply at today's consumption rate in total.
Nuclear weapons
The material must be 85% or more of 235U and is known as weapons grade uranium, though for a crude, inefficient weapon, 20% is sufficient (called weapon(s)-usable). Even lower enrichment can be used, but then the required critical mass rapidly increases.It emits only alpha radiation, which can easily be shielded. Unlike plutonium, the radiological hazards of handling highly enriched uranium wrapped in paper are relatively low. But HEU has another property: It can be used as a nuclear explosive material, making it one of the most dangerous substances on earth.
Plutonium generally isn't found in nature. Trace elements of plutonium are found in naturally occurring uranium ores. Here, it is formed in a way similar to neptunium: by irradiation of natural uranium with neutrons followed by beta decay. Primarily, however, plutonium is a byproduct of the nuclear power industry.
The uranium used in nuclear reactors is enriched to about 4% U-235. But for nuclear bombs it must be enriched to about 90%. Under the nuclear deal, Iran is permitted to enrich uranium to 3.67% but now intends to exceed that limit.
The United States Enrichment Corporation, a subsidiary of Centrus Energy Corp. (formerly USEC Inc.), is a corporation that contracts with the United States Department of Energy to produce enriched uranium for use in nuclear power plants.
In 2003, the International Atomic Energy Agency (IAEA) first reported that Iran had not declared sensitive enrichment and reprocessing activities. Iran says its nuclear program is peaceful, and has enriched uranium to less than 5 per cent, consistent with fuel for a civilian nuclear power plant.
