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Science Basics

Included here are more in depth explanations of some of the terms and processes in the Nuclear Fuel Cycle.

The Elements

Nuclear Fuel is produced utilizing various elements and compounds in reactions that yied the product desired at the various stages.  Initially uranium is the prime constituent looked for in its natural setting during the exploration phase.  The ore body, the rock, that holds the uranium also contains many other elements and compounds.  While these remain undisturbed, very little of these components enter the surrounding environment.  But once mining is initiated, all of the components are moved throughout the environment and left, in many cases, to contaminate the ground and water systems.  While most of the uranium is taken from the mine location, almost all of the other components are left in piles of waste rock and tailings either at the mine or at the mill.  Below are the various components found in uranium ore bodies.  Full descriptions can be found on Wikepedia.

Uranium - (pronounced /jʊˈreɪniəm/) is a silvery-gray metallic chemical element in the actinide series of the periodic table that has the symbol U and atomic number 92. It has 92 protons and 92 electrons, 6 of them valence electrons. It can have between 141 and 146 neutrons, with 146 (U-238) and 143 in its most common isotopes. Uranium has the highest atomic weight of the naturally occurring elements. Uranium is approximately 70% denser than lead, but not as dense as gold or tungsten. It is weakly radioactive. It occurs naturally in low concentrations (a few parts per million) in soil, rock and water, and is commercially extracted from uranium-bearing minerals such as uraninite (see uranium mining).

A person can be exposed to uranium (or its radioactive daughters such as radon) by inhaling dust in air ,or by ingesting contaminated water and food.  Absorbed uranium tends to bioaccumulate and stay for many years in bone tissue because of uranium's affinity for phosphates.  Normal functioning of the kidney, brain, liver, heart, and numerous other systems can be affected by uranium exposure, because in addition to being weakly radioactive, uranium is a toxic metal.  Uranium is also a reproductive toxicant.

In nature, uranium atoms exist as uranium-238 (99.284%), uranium-235 (0.711%), and a very small amount of uranium-234 (0.0058%). Uranium decays slowly by emitting an alpha particle. The half-life of uranium-238 is about 4.47 billion years and that of uranium-235 is 704 million years, making them useful in dating the age of the Earth (see uranium-thorium dating, uranium-lead dating and uranium-uranium dating).

Many contemporary uses of uranium exploit its unique nuclear properties. Uranium-235 has the distinction of being the only naturally occurring fissile isotope. Uranium-238 is both fissionable by fast neutrons, and fertile (capable of being transmuted to fissile plutonium-239 in a nuclear reactor). An artificial fissile isotope, uranium-233, can be produced from natural thorium and is also important in nuclear technology. While uranium-238 has a small probability to fission spontaneously or when bombarded with fast neutrons, the much higher probability of uranium-235 and to a lesser degree uranium-233 to fission when bombarded with slow neutrons generates the heat in nuclear reactors used as a source of power, and provides the fissile material for nuclear weapons. Both uses rely on the ability of uranium to produce a sustained nuclear chain reaction. Depleted uranium (uranium-238) is used in kinetic energy penetrators and armor plating.  To read a more in depth description please visit the Wikipedia link: URANIUM

Thorium - (pronounced /ˈθɔəriəm/) is a chemical element with the symbol Th and atomic number 90. As a naturally occurring, slightly radioactive metal, it has been considered as an alternative nuclear fuel to uranium.  When pure, thorium is a silvery-white metal that retains its luster for several months. However, when it is exposed to oxygen, thorium slowly tarnishes in air, becoming grey and eventually black. Thorium dioxide (ThO2), also called thoria, has the highest melting point of any oxide (3300°C).  Exposure to an aerosol of thorium can lead to increased risk of cancers of the lung, pancreas and blood. Exposure to thorium internally leads to increased risk of liver diseases.  To read a more in depth description please visit the Wikipedia link: THORIUM

Protactinium - (pronounced /ˌproʊtækˈtɪniəm/) is a chemical element with the symbol Pa and atomic number 91. Its longest-lived isotope has a half-life of 32,760 years.  Due to its scarcity, high radioactivity, and toxicity, there are currently no uses for protactinium outside of basic scientific research.  Protactinium occurs in pitchblende to the extent of about 1 part 231Pa per 10 million parts of ore (i.e., 0.1 ppm).  Protactinium is both toxic and highly radioactive. It requires precautions similar to those used when handling plutonium.  To read a more in depth description please visit the Wikipedia link: PROTACTINIUM

Actinium - (pronounced /ækˈtɪniəm/) is a radioactive chemical element with the symbol Ac and atomic number 89, which was discovered in 1899.  Actinium is a silvery, radioactive, metallic element. Due to its intense radioactivity, actinium glows in the dark with a pale blue light. The chemical behavior of actinium is similar to that of the rare earth element lanthanum227Ac is extremely radioactive, and in terms of its potential for radiation induced health effects[15] 227Ac is even more dangerous than plutonium. Ingesting even small amounts of 227Ac would be fatal.  To read a more in depth description please visit the Wikipedia link: ACTINIUM

Radium - (pronounced /ˈreɪdiəm/) is a radioactive chemical element which has the symbol Ra and atomic number 88. Its appearance is almost pure white, but it readily oxidizes on exposure to air, turning black.   Radium is an alkaline earth metal that is found in trace amounts in uranium ores. It is extremely radioactive.  Radium is a decay product of uranium and is therefore found in all uranium-bearing ores.  Radium is highly radioactive and its decay product, radon gas, is also radioactive. Since radium is chemically similar to calcium, it has the potential to cause great harm by replacing it in bones. Inhalation, injection, ingestion or body exposure to radium can cause cancer and other disorders.  To read a more in depth description please visit the Wikipedia link: RADIUM

Radon - (pronounced /ˈreɪdɒn/) is a chemical element with symbol Rn and atomic number 86. Radon is a colorless, odorless, naturally occurring, radioactive noble gas that is formed from the decay of radium. It is one of the heaviest substances that remains a gas under normal conditions and is considered to be a health hazard.  Radon is a significant contaminant that affects indoor air quality worldwide. Radon gas from natural sources can accumulate in buildings, especially in confined areas such as the basement. Radon can be found in some spring waters and hot springs.  According to the United States Environmental Protection Agency, radon is reportedly the second most frequent cause of lung cancer, after cigarette smoking; and radon-induced lung cancer the 6th leading cause of cancer death overall. According to the same sources, radon reportedly causes 21,000 lung cancer deaths per year in the United StatesTo read a more in depth description please visit the Wikipedia link: RADON

Polonium - pronounced /pəˈloʊniəm/) is a chemical element with the symbol Po and atomic number 84, discovered in 1898 by Marie and Pierre Curie. A rare and highly radioactive metalloid,[1] polonium is chemically similar to bismuth[2] and tellurium, and it occurs in uranium ores.  By mass, polonium-210 is around 250,000 times more toxic than hydrogen cyanide (the actual LD50 for 210Po is about 1 microgram for an 80 kg person (see below) compared with about 250 milligrams for hydrogen cyanide).  It has been estimated that a median lethal dose of 210Po is 0.015 GBq (0.4 millicuries), or 0.089 micrograms, still an extremely small amount.  To read a more in depth description please visit the Wikipedia link: POLONIUM

Lead - (pronounced /ˈlɛd/) is a main-group element with symbol Pb (Latin: plumbum) and atomic number 82. Lead is a soft, malleable poor metal, also considered to be one of the heavy metals. Lead has a bluish-white color when freshly cut, but tarnishes to a dull grayish color when exposed to air. It has a shiny chrome-silver luster when melted into a liquid.  Lead has the highest atomic number of all stable elements, although the next element, bismuth, has a half-life so long (longer than the estimated age of the universe) it can be considered stable. Like mercury, another heavy metal, lead is a potent neurotoxin that accumulates in soft tissues and bone over time.  Lead is a poisonous metal that can damage nervous connections (especially in young children) and cause blood and brain disorders.  To read a more in depth description please visit the Wikipedia link: LEAD

Molybdenum - (pronounced /məˈlɪbdənəm/, from the Greek word for the metal "lead"), is a Group 6 chemical element with the symbol Mo and atomic number 42.  It has the eighth-highest melting point of any element. It readily forms hard, stable carbides, and for this reason it is often used in high-strength steel alloys.  Molybdenum is found in trace amounts in plants and animals, although excess molybdenum can be toxic in some animals.The ability of molybdenum to withstand extreme temperatures without significantly expanding or softening makes it useful in applications that involve intense heat, including the manufacture of aircraft parts, electrical contacts, industrial motors, and filaments.  Molybdenum dusts and fumes, as can be generated by mining or metalworking, can be toxic, especially if ingested (including dust trapped in the sinuses and later swallowed).[21] Low levels of prolonged exposure can cause irritation to the eyes and skin. The direct inhalation or ingestion of molybdenum and its oxides should also be avoided.  Chronic exposure to 60 to 600 mg Mo/m³ can cause symptoms including fatigue, headaches, and joint pains.  To read a more in depth description please visit the Wikipedia link: MOLYBDENUM

Vanadium - (IPA: /vəˈneɪdiəm/) is the chemical element with the symbol V and atomic number 23.  It is a soft, ductile, silver-grey metal.  Most vanadium is used as ferrovanadium as an additive to improve steels.  All vanadium compounds should be considered to be toxic.  The Occupational Safety and Health Administration (OSHA) has set an exposure limit of 0.05 mg/m3 for vanadium pentoxide dust and 0.1 mg/m3 for vanadium pentoxide fumes in workplace air for an 8-hour workday, 40-hour work week.  The National Institute for Occupational Safety and Health (NIOSH) has recommended that 35 mg/m3 of vanadium be considered immediately dangerous to life and health. This is the exposure level of a chemical that is likely to cause permanent health problems or death.  To read a more in depth description please visit the Wikipedia link: VANADIUM

Decay Chains

In nuclear science, the decay chain refers to the radioactive decay of different discrete radioactive decay products as a chained series of transformations. Most radioactive elements do not decay directly to a stable state, but rather undergo a series of decays until eventually a stable isotope is reached.

Decay stages are referred to by their relationship to previous or subsequent stages. A parent isotope is one that undergoes decay to form a daughter isotope. The daughter isotope may be stable or it may decay to form a daughter isotope of its own. The daughter of a daughter isotope is sometimes called a granddaughter isotope

The four most common modes of radioactive decay are: alpha decay, beta minus decay, beta plus decay (considered as both positron emission and electron capture), and isomeric transition. Of these decay processes, alpha decay changes the atomic mass number (A) of the nucleus, and always decreases it by four. Because of this, almost any decay will result in a nucleus whose atomic mass number has the same residue mod 4, dividing all nuclides into four classes. The members of any possible decay chain must be drawn entirely from one of these classes. All four chains also produce helium, from alpha particles.

Three main decay chains (or families) are observed in nature, commonly called the thorium series, the radium series (not uranium series), and the actinium series, representing three of these four classes, and ending in three different, stable isotopes of lead. The mass number of every isotope in these chains can be represented as A=4n, A=4n+2, and A=4n+3, respectively. The long-lived starting isotopes 232Th, 238U, and 235U, respectively, of these three have existed since the formation of the earth. The plutonium isotopes Pu-244 and Pu-239 have also been found in trace amounts on earth[1].

 To read more about decay chains please visit the Wikipedia link: DECAY CHAIN 


Radium Series - The Uranium238 Decay Chain

RADIUM SERIES DECAY TABLEBeginning with naturally occurring uranium-238, this series includes the following elements: astatine, bismuth, lead, polonium, protactinium, radium, radon, thallium, and thorium. All are present, at least transiently, in any uranium-containing sample, whether metal, compound, or mineral. 



Actinium Series - The Uranium235 Decay Chain

ACTINIUM SERIES DECAY TABLEBeginning with naturally occurring uranium-235, this series includes the following elements: Actinium, astatine, bismuth, francium, lead, polonium, protactinium, radium, radon, thallium, and thorium. All are present, at least transiently, in any uranium-containing sample, whether metal, compound, ore, or mineral.  ACTINIUM SERIES DECAY CHAIN


Thorium Series - The Thorium232 Decay Chain

THORIUM SERIES DECAY TABLEBegining with naturally occurring thorium-232, this series includes the following elements: Actinium, bismuth, lead, polonium, radium, and radon. All are present, at least transiently, in any natural thorium-containing sample, whether metal, compound, or mineral.  THORIUM SERIES DECAY CHAIN

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