Cesium is chemical element with the symbol Cs and an atomic weight of 55. It was discovered in 1860 by Robert Bunsen and Gustav Kirchhoff with the new flame spectroscopy method. It is a soft, silvery gold alkali metal with a melting point of 28° C or 82° F and is one of only five elemental metals that is liquid near room temperature. It is highly reactive and pyrophoric. In open air, it will burst into flames and it reacts explosively with water. Cesium can form compounds with many other metals. It readily forms phosphate, acetate, carbonate, halide, oxide, nitrate and sulfate salts.

          Cesium is a relatively rare element at 45^th in abundance. Because of its structure, it crystallizes last when magma cools and is found mostly in zone deposits of granite. The only commercial ore is pollucite which in a mineral of cesium, aluminum, silicon and oxygen. Two thirds of the worlds reserves are found in high grade ore in Manitoba, Canada. There are also deposits in Zimbabwe and Namibia in Africa.

          Cesium has 40 isotopes from atomic weight of 112 to 151 with only Cs-133 being stable. All the rest are radioactive with half-lives ranging from Cs-122m1 and Cs-126m1 at less than one millionths of a second to Cs-135 with a half-life of 2.3 million years. Almost all radioisotopes of cesium are produced in nuclear explosions or nuclear reactors by fission processes or by decay of fission products. Cs-137 with a half-life of 30 years accounts for most of the radioactivity in spent nuclear fuel for several hundred years. Because isotopes of cesium are created by decay of isotopes of radioactive xenon gas, if there is a release of radioactive materials from a nuclear accident, Cs-137 can be produced far from the site of the accident. Decay of Cs generates beta particles and gamma rays.

          Commercial uses of non-radioactive cesium include use in photoelectric and solar cells due the fact that light can free electrons from the cesium atom. Its high reactivity makes it useful for clearing out the remaining gases in the manufacture of light bulbs. It is also used as a catalyst for the hydrogenation of a few organic compounds. Ion propulsion systems for space craft have been created using cesium which is 140 times more efficient than burning any other know liquid or solid.

          Cesium-137 is recovered by reprocessing spent nuclear fuel. Atomic clocks are constructed by exciting Cs-137 with a beam of energy and measuring the radiation of the outer electrons in the electron shell. It can be used to calibrate radiation detection equipment. The gamma radiation emitted by Cs-137 is used in industry for density measurements of fluid flow and thickness of materials. It is sometimes used in cancer therapy. Because Cs-137 is entirely man-made and only entered the environment after the detonation of nuclear bombs, it can be used to determine if a sealed container was made before or after the start of the atomic age in the 1940s. Mishandling of Cs-137 has resulted in radioactive contamination of steel produced by recycling scrap metal. Cs-137 is dangerous and ingestion of less than one thousandth of a gram per kilogram is lethal within weeks.

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          Iodine is a chemical element with the symbol I and atomic number 53. It was discovered in 1811 by Frenchman Bernard Courtis in one of those luck accidents when he added too much sulfuric acid to ashes of seaweed that he was processing. The purple vapor that was given off crystallized out on nearby surfaces and was eventually given the name “iodine” derived from the Greek word for purple.

          Iodine is a non-metallic element of the halogen family in the periodic table which also includes fluorine, chlorine, bromine and astatine. It is a bluish black solid under normal conditions but it does sublimate into purple vapor. It melts at 113.7 °C but also gives off the purple gas as it melts. It dissolves easily in most organic solvents but does not dissolve very well in water unless it is in the presence of potassium. Iodine is a relatively rare element which is found in greater concentrations in free ions of iodine salts in ocean water than in rocks. It is rare in soils and is leached out by rainwater and carried to the ocean.

        Iodine is the heaviest of the essential mineral elements and was probably incorporated into biological functioning because of its presence in the oceans where life originated. Iodine assists in the synthesis of thyroid hormones and it is absorbed by the thyroid when it enters the body. Because of its rarity in soil, especially away from the ocean, about two billion people on earth have iodine deficiency which can lead to intellectual disabilities.

         Iodine has 37 isotopes from atomic weight of I-108 to I-144. Only one of the isotopes, I-127 is stable and the rest are radioactive. The half-lives vary from I-130m2 with a half-life of 133 billionths of a second to I-129 with a half-life of 15.7 million years. All the rest of the radioisotopes of iodine have half-lives of less than 60 days. All most all of the Iodine on earth occurs is in the form of the stable isotope. The tiny amount of I-129 on earth results mostly from nuclear explosions and nuclear accidents. Other isotopes rapidly vanish after their creation.

            I-135 is produced in nuclear reactors and decays to xenon-135 which “poisons” nuclear fuel by reducing the neutron flux and slowing fission reactions. Large amounts of Xe-135 can temporarily interfere with restarting a shut-down reactor.

          I-131 is one of the primary by-products of nuclear fission and is produced in nuclear reactors. It emits highly energetic beta particles and is the most carcinogenic of all the isotopes of iodine. When it escapes into the natural environment by nuclear explosions or severe nuclear accidents, it poses a very serious but short term health danger. Nonradioactive iodine in the form of potassium iodine tablets is given to people who may be exposed to I-131 because it will saturate the thyroid gland and prevent the I-131 from being absorbed.

         Four of the isotopes of iodine are produced commercially for medical use. The beta radiation emitted by I-131 is used to kill thyroid tissue to prevent it from becoming cancerous. Isotopes I-123 and I-125 emit gamma rays which are useful as tracers which help image the structure and functioning of the thyroid gland. I-125 can also be implanted in a small capsule to irradiate cancerous tissue in the lungs. I-124 emits protons which is useful for positron emission tomography (PET) for direct imaging of the thyroid gland or tracer imaging. 

Iodine crystals:

Iodine.PNG

          Americium is alkaline metal element with the symbol Am and atomic number 95. It is above uranium in the periodic table and is referred to as a transuranic element. Silvery in color, Americium is a soft radioactive metal. It was first synthesized in 1944 by Glenn T. Seaborg at the University of California, Berkeley. The name was taken from America.

          Americium oxidizes easily and dissolves well in acids. It forms compounds with halogen gases, sulfur., selenium, phosphorus, arsenic, antimony, bismuth and silicon. The metallic form is malleable and has a relatively high melting point of 1173 C°

          Americium has 19 isotopes, all of them radioactive. The atomic weights vary from Am-231 to Am-249. The half-lives vary from Am-239m at 163 billionths of a second to Am-243 at 7,370 years. Americium is produced by the bombardment of uranium, plutonium or existing Americium with slow neutrons. A tiny amount is produced in nuclear reactors and in nuclear explosions.  Am-241 with a half-life of 432 years is the most plentiful isotope in radioactive waste. It decays by alpha emission with gamma ray production.

          Commercial production of americium consists of dissolving the uranium and plutonium out of spent mixed oxide nuclear fuel. This leaves a mixture of oxides of actinide and lanthanide isotopes. Using various solvents along with chromatography and centrifuges, the Am-241 is extracted. The Am-241 can then be used to create other isotopes of americium if desired.

         The most common use of americium is in home smoke detectors. It is a source of ionizing radiation in the form of alpha particles but it emits much less gamma radiation and is preferred over radium-228. About one quarter of a millionth of a gram of americium is used in a typical smoke detector. The americium ionizes the air between two electrodes allowing a small current to flow. When smoke enters the alarm, it reduces the ionization which lowers the current and triggers the alarm. These alarms are more sensitive but more prone to false alarms than optical smoke detectors.

         Americium combined with beryllium is used as a source of neutrons in devices that measure the water content of soil, neutron radiography, tomography, and other applications that require neutrons.

          Use of americium in radioisotope thermoelectric generators has been suggested. It has five times the half life of the plutonium which is currently used in such generators. Americium may also find use as part of a propulsion system for spacecraft. The fission products of americium could be used to directly drive the craft or it could be used to heat a thrusting gas or liquid. Efficient nuclear batteries based on the charge properties of americium have also been proposed. The main impediment to these new applications lies in the high cost and low availability of americium.

        As with other transuranics, americium has no biological function. It mainly emits alpha particles which can be easily blocked but are dangerous if inhaled or consumed. Inside the body, the americium finds it way to the bones, the liver and the testicles or ovaries and can cause cancer. Daughter products from americium decay produce dangerous gamma rays and neutrons. There are few regulations about disposure of smoke detectors which is the main way that americium enters the environment.

Inside a smoke detector:

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          Cobalt is a chemical element with the symbol Co and the atomic number 27. It readily forms compounds with other elements and compounds. When it is extracted from naturally occurring compounds via reductive smelting, it is a hard, shiny, sliver-gray metal.

         The name comes from the German word “kobold” which mean “goblin.” Miners were familiar with ores that were poor in metals that they called goblin ore partly because of the deadly arsenic fumes given off when heated.  The minerals in such ores were used since ancient times as a pigment for blue paint. Most of the cobalt ore mined in the world today is a byproduct of copper and nickel mining in the Democratic Republic of Congo and Zambia in Africa.

       Today cobalt is used to create high-strength alloys which are wear-resistant and magnetic. Silicate and aluminate compounds of cobalt are used to impart a deep blue color to glass, ceramics, inks, paints and varnishes.

       Cobalt is present in living cells. The cobalt atom forms the active center of certain coenzymes called cobalamins. The vitamin B₁₂ is an example of such cobalamins. Cobalt is a necessary trace dietary mineral for all living creatures.

       Naturally occurring cobalt contains the stable isotope with an atomic weight of 59 which is the only stable isotope. There are a total of 28 radioactive isotopes that range from atomic weight of 47 to 73. They vary Co-51 with a half-life of 200 billionth of a second to Co-60 with a half-life of 5.27 years.

      Cobalt-60 is created by bombarding the stable Co-59 with slow neutrons in CANDU reactors or from californium-252. It undergoes beta decay to Nickel-70 which then gives off gamma radiation to achieve a stable state. It is the emission of gamma rays that makes Co-60 a useful isotope. It is used as a tracer for chemical reactions, sterilization of medical equipment, a source of radiation for medical radiotherapy, a radiation source for industrial radiography, a radiation source for leveling devices and thickness gauges, a radiation source to sterilize food and blood and a radiation source for general laboratory use.

       One of the problems with the use of Co-60 is the fact that the solid form can disintegrate into a powder which can be inhaled and cause biological damage. This makes the handling of devices employing Co-60 more dangerous. Its use in many applications as a gamma ray source has been declining. Improper disposal of medical equipment containing Co-60 as scrap metal led to radioactivity appearing in iron produced by smelting the contaminated scrap.

       Cobalt-57 is made in cyclotrons by the irradiation of iron. It has a half-life of 271 days and it decays by electron capture to Iron-57 which emits gamma radiation to achieve a stable state. It is used in medicine as a tracer for the metabolization  of vitamin B_12.

Cobalt 60 cancer therapy machine:

Cobalt machine.JPG

          Plutonium is a silvery-grey radioactive actinide metal with the symbol Pu and the atomic number of 94. Plutonium was first synthesized in 1940 by Glenn Seaborg an Edwin McMillan at the University of California by bombarding U-238 with deuterons which are nuclei of deuterium containing a neutron and a proton. Following its synthesis, plutonium-244 was discovered in minute quantities in the natural environment.

          Plutonium is beyond uranium in the periodic table which makes it a “transuranic” element. It can react with carbon, halogen gases, nitrogen, silicon, oxygen and water. It expands when exposed to moisture and forms flakes into a powder which can spontaneously ignite. Under normal conditions, plutonium is hard and brittle like grey case iron. It has to be combined with other metals to make it soft and ductile. It is not a good conductor of heat or electricity and it has a low melting point but a high boiling point.

         Plutonium has twenty six isotopes which vary in atomic weight from Pu-228 to Pu-247 and include 7 modes with excited nucleons. Their half-lives vary from Pu-244 with a half-life of 80 million years to Pu-239m1 with a half-life of 193 nanoseconds or billionths of a second.

         Plutonium is the product of nuclear fission. Different isotopes are produced in the radioactive decay of different elements. Higher weight isotopes of plutonium can be created by bombarding plutonium isotopes with more neutrons. Plutonium is difficult to make and it is very difficult to separate the isotopes so particular isotopes are usually made individually with neutron capture.

         The most important isotope of plutonium is Pu-239 which is fissile meaning that it can be made to sustain a fission reaction. Bombarding Pu-239 with slow thermal neutrons causes its nuclei to break apart releasing energy including gamma radiation and more neutrons. Pu-239 is created by bombarding U-238 with neutrons and then recovering the plutonium by reprocessing. Plutonium 238 is utilized as a heat source in radioisotope thermoelectric generators which are used for power in some satellites. Plutonium 240 fissions spontaneously at a high rate and make the material containing it less useful for nuclear reactor fuel and nuclear weapons production. Because of this property, the ratio of Pu-240 found in a sample is used as a way to grade the sample. Supergrade plutonium containing less than 4% Pu-240 is used in naval weapons stored near ships and personnel because of its relatively low radioactivity. Less than 7% of weapons grade plutonium is Pu-240. From 7% to 19% of fuel grade plutonium is Pu-240. Fuel grade is used in as fuel in nuclear reactors. The spent fuel from light water and CANDU is considered reactor grade plutonium and it contains more than 19% Pu-240.

          If a sufficient mass of weapons grade plutonium 329 is formed into a sphere, it can achieve a critical mass which is the smallest amount of a fissile material needed for a sustained nuclear reaction. A greater mass than the critical mass is referred to as super critical. With the right design and treatment, a super critical mass can lead to a run-away chain reaction resulting in an atomic explosion. In an atomic explosion a fraction of the binding energy of the plutonium nuclei is converted to light and heat. The fission of a single kilogram of plutonium can create an explosion equivalent to 21,000 tons or 21 kilotons of TNT.

Plutonium ring:

Plutonium_ring.jpg

          Plutonium is a silvery-grey radioactive actinide metal with the symbol Pu and the atomic number of 94. Plutonium was first synthesized in 1940 by Glenn Seaborg an Edwin McMillan at the University of California by bombarding U-238 with deuterons which are nuclei of deuterium containing a neutron and a proton. Following its synthesis, plutonium-244 was discovered in minute quantities in the natural environment.

          Plutonium is beyond uranium in the periodic table which makes it a “transuranic” element. It can react with carbon, halogen gases, nitrogen, silicon, oxygen and water. It expands when exposed to moisture and forms flakes into a powder which can spontaneously ignite. Under normal conditions, plutonium is hard and brittle like grey case iron. It has to be combined with other metals to make it soft and ductile. It is not a good conductor of heat or electricity and it has a low melting point but a high boiling point.

         Plutonium has twenty six isotopes which vary in atomic weight from Pu-228 to Pu-247 and include 7 modes with excited nucleons. Their half-lives vary from Pu-244 with a half-life of 80 million years to Pu-239m1 with a half-life of 193 nanoseconds or billionths of a second.

         Plutonium is the product of nuclear fission. Different isotopes are produced in the radioactive decay of different elements. Higher weight isotopes of plutonium can be created by bombarding plutonium isotopes with more neutrons. Plutonium is difficult to make and it is very difficult to separate the isotopes so particular isotopes are usually made individually with neutron capture.

         The most important isotope of plutonium is Pu-239 which is fissile meaning that it can be made to sustain a fission reaction. Bombarding Pu-239 with slow thermal neutrons causes its nuclei to break apart releasing energy including gamma radiation and more neutrons. Pu-239 is created by bombarding U-238 with neutrons and then recovering the plutonium by reprocessing. Plutonium 238 is utilized as a heat source in radioisotope thermoelectric generators which are used for power in some satellites. Plutonium 240 fissions spontaneously at a high rate and make the material containing it less useful for nuclear reactor fuel and nuclear weapons production. Because of this property, the ratio of Pu-240 found in a sample is used as a way to grade the sample. Supergrade plutonium containing less than 4% Pu-240 is used in naval weapons stored near ships and personnel because of its relatively low radioactivity. Less than 7% of weapons grade plutonium is Pu-240. From 7% to 19% of fuel grade plutonium is Pu-240. Fuel grade is used in as fuel in nuclear reactors. The spent fuel from light water and CANDU is considered reactor grade plutonium and it contains more than 19% Pu-240.

          If a sufficient mass of weapons grade plutonium 329 is formed into a sphere, it can achieve a critical mass which is the smallest amount of a fissile material needed for a sustained nuclear reaction. A greater mass than the critical mass is referred to as super critical. With the right design and treatment, a super critical mass can lead to a run-away chain reaction resulting in an atomic explosion. In an atomic explosion a fraction of the binding energy of the plutonium nuclei is converted to light and heat. The fission of a single kilogram of plutonium can create an explosion equivalent to 21,000 tons or 21 kilotons of TNT.

Plutonium ring:

Plutonium_ring.jpg

           Radium is a chemical element with the symbol Ra and an atomic number of 88. It was discovered in 1898 by Marie and Pierre Curie. They extracted it from uranium ore. Twelve years later, Marie Curie and Andre Debierne isolated the pure metallic form of radium by electrolysis from radium chloride. It was given the French name radium from Latin radius or ray. The curie unit of radioactivity was named for Marie Curie and is based on the radioactivity of Ra-226.

          Radium is one of the alkaline earth metals along with beryllium, magnesium, calcium, strontium and barium. Earth metals are soft with a silver color and they have low densities, melting points and boiling points. They form compounds with the halogens such as chlorine and react vigorously with water to form hydroxides.

          All the isotopes of radium are highly radioactive. They have atomic weights from Ra-202 to Ra-234 and half lives from .85 microseconds for a excited state of Ra212m2 to 1600 years for Ra-226. There are a total of 35 radium isotopes with 11 of them being metastable states with excited nucleons.

          Ra-226 is the most common radium isotope and is part of the chain of daughter products resulting from the breakdown of U-238. The next most common isotope is Ra-226 with a half life of 5.75 years. It is part of the radioactive decay chain of thorium.  Radium is over a million times as radioactive as the same amount of uranium. It decays into radon which is a radioactive gas that is a health hazard. Other products of radium decay include polonium, bismuth and inert non-radioactive lead. All radium is created by the radioactive decay of other elements which have long half lives. With its short half life, radium is only found in minute quantities in association with naturally occurring uranium and thorium. Radium glows in the dark as a result of

        . Radium was first produced commercially by Biraco in its Belgium plant at Olen in the early 20^th Century. Radium ionizes air which give up its excitation in the form of blue light making radium glow in the dark. It can also energize substances that are referred to as radioluminescent and cause them to glow in the dark in a variety of colors. Luminescent paint made with Ra-226 was invented in 1908. Such paint was widely used in the 1920s and 1930s for such applications as watch dials and aircraft instruments.. Stored radium must be well ventilated to prevent buildup of radon gas.

        The radioactivity of radium and its daughter products such as radon gas pose a serious health risk to anyone who is exposed. Radium emits alpha particles which can mutate cells and cause cancer. Because radium is very similar to calcium, it can be taken up by the processes that create and maintain bones. As women working with radium containing paints became ill, the deleterious health effects of radium became apparent. Ironically, health tonics containing radium had been sold before its dangers were clearly understood. Such used of radium were eventually outlawed.

         Radium is currently used for medical purposes such as treatment of tumors with the gamma radiation that it emits. There are also industrial uses such as production of radon gas, manufacture of medical equipment and lightning rods and neutron generators,.

Picture of a radium tonic bottle from Oak Ridge Associated Universities:

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          Radon is a tasteless, colorless, odorless elemental noble gas in the family with helium, neon, argon, krypton and xenon. Its chemical symbol is Rn and it has an atomic number of 86. It is the densest noble gas and one of the densest gases that exist. As with the other noble gases, radon is chemically inert and rarely forms compounds with other substances. It was discovered in 1900 by Friedrich Ernst Dorn as a gas given off by radium. Other gases generated by radioactive decay were subsequently discovered and eventually recognized as being radon. Some of its properties were discovered and reported in 1910.

          Radon is highly radioactive and has no stable isotopes. The 39 isotopes of radon vary in atomic weight from 193 to 228. 6 of the isotopes have the same atomic weight of other isotopes but they what are called metastable nuclear isomers which means that one or more of the neutrons and/or protons in their nuclei are in an excited state. They have much longer half lives than most of the excited states of a particular isotope.

         Radon gas is formed by the radioactive decay of uranium or thorium. When these naturally occurring elements decay, they generate whole chains of decay products with the ultimate end of the chain being non-radioactive and stable lead. Different isotopes of radon are generated by different decay chains. Radioactive radium and actinium which are also part of decay chains spawn radon isotopes. Radon isotopes spawn radioactive daughter products of other elements in turn as part of the decay chains including other isotopes of radon. Radon half lives vary from Rn-222, a decay products of uranium, which has a half life of 3.8 days to Rn-214 .27 microseconds (millionths of a second).

        Because uranium is so ubiquitous in the natural environment, radon gas is also ubiquitous. All natural soil constantly emits tiny amounts of Radon. Being dense radon tends to accumulate where there is poor air circulation like in basements and attics. There is great variation in the amount of radon in homes because of differences in underlying geology, water, naturally occurring proportion of uranium, ventilation, etc. Radon concentration in the USA is measured in picocuries per liter of air.

         Radon gas is very toxic and is the primary way in which ionizing radiation threatens human beings. Isotopes of radon emit alpha or beta particles. The most common isotope of radon is Rn-222 which is an alpha emitter. Most of the daughter products of radon decay are solids so when radon decays, the decay products can wind up sticking to dust particles. When these are inhaled, they accumulate in the lungs and can lead to lung cancer. A clear correlation has been shown between radon concentration and lung cancer. Radon is thought to cause 21,000 cases of lung cancer per year in the United States, second only to cigarette smoking. Radon gas exposure is a major problem in uranium mining and processing.

         Radon is commercially produced in small amounts for use in radiation therapy for cancer treatment. Artificially produced radon and radon in old mines is a common treatment for arthritis in many European countries. Radon produced by decay of radium paint was once used to create objects that would glow in the dark but this use has been discontinued.

From the U.S. EPA:

          Radon is a tasteless, colorless, odorless elemental noble gas in the family with helium, neon, argon, krypton and xenon. Its chemical symbol is Rn and it has an atomic number of 86. It is the densest noble gas and one of the densest gases that exist. As with the other noble gases, radon is chemically inert and rarely forms compounds with other substances. It was discovered in 1900 by Friedrich Ernst Dorn as a gas given off by radium. Other gases generated by radioactive decay were subsequently discovered and eventually recognized as being radon. Some of its properties were discovered and reported in 1910.

          Radon is highly radioactive and has no stable isotopes. The 39 isotopes of radon vary in atomic weight from 193 to 228. 6 of the isotopes have the same atomic weight of other isotopes but they what are called metastable nuclear isomers which means that one or more of the neutrons and/or protons in their nuclei are in an excited state. They have much longer half lives than most of the excited states of a particular isotope.

         Radon gas is formed by the radioactive decay of uranium or thorium. When these naturally occurring elements decay, they generate whole chains of decay products with the ultimate end of the chain being non-radioactive and stable lead. Different isotopes of radon are generated by different decay chains. Radioactive radium and actinium which are also part of decay chains spawn radon isotopes. Radon isotopes spawn radioactive daughter products of other elements in turn as part of the decay chains including other isotopes of radon. Radon half lives vary from Rn-222, a decay products of uranium, which has a half life of 3.8 days to Rn-214 .27 microseconds (millionths of a second).

        Because uranium is so ubiquitous in the natural environment, radon gas is also ubiquitous. All natural soil constantly emits tiny amounts of Radon. Being dense radon tends to accumulate where there is poor air circulation like in basements and attics. There is great variation in the amount of radon in homes because of differences in underlying geology, water, naturally occurring proportion of uranium, ventilation, etc. Radon concentration in the USA is measured in picocuries per liter of air.

         Radon gas is very toxic and is the primary way in which ionizing radiation threatens human beings. Isotopes of radon emit alpha or beta particles. The most common isotope of radon is Rn-222 which is an alpha emitter. Most of the daughter products of radon decay are solids so when radon decays, the decay products can wind up sticking to dust particles. When these are inhaled, they accumulate in the lungs and can lead to lung cancer. A clear correlation has been shown between radon concentration and lung cancer. Radon is thought to cause 21,000 cases of lung cancer per year in the United States, second only to cigarette smoking. Radon gas exposure is a major problem in uranium mining and processing.

         Radon is commercially produced in small amounts for use in radiation therapy for cancer treatment. Artificially produced radon and radon in old mines is a common treatment for arthritis in many European countries. Radon produced by decay of radium paint was once used to create objects that would glow in the dark but this use has been discontinued.

From the U.S. EPA:

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          When enriched uranium is used in nuclear reactors, the exhausted fuel consists mainly of U-238 with small amounts of U-235, plutonium and minor actinides such as neptunium, americium, curium, berkelium, californium, einsteinium, and fermium. There are commercial facilities in France, the United Kingdom and Japan for reprocessing spent fuel. Reprocessing is also carried out at nuclear weapons facilities. Reprocessing is currently carried out in eleven countries.

          Originally, spent fuel was reprocessed primarily for the purpose of extracting plutonium for use in nuclear weapons. With the spread of commercial reactors, plutonium began to be used in Mixed Oxide (MOX) reactors.

          CANDU reactors are designed to use natural uranium as a fuel so spent fuel can be used in these reactors because the U-235 remaining is still present in a higher ratio than naturally occurring uranium. It only needs to be processed physically in order to be utilized with no chemical processing required.

          Reprocessed uranium and depleted uranium can be used in fast breeder reactor blankets but there is currently no commercial market for this use. Currently the price of uranium is too low to justify re-enrichment of spent fuel to supply commercial reactors but that could change if the price of uranium continues to rise.

          The current main method of reprocessing is Plutonium and Uranium Recovery by Extraction (PUREX). The spent fuel is dissolved in nitric acid and the resulting liquid is filtered. Organic solvents are used to created compounds of plutonium and uranium which are then chemically separated and extracted. A modified version of PUREX known as UREX just extracts the uranium which constitutes most of the spent fuel. TRUEX is another extraction technique which removes the americium and californium and lowers the alpha radioactivity of the spent fuel making disposal easier.

          A number of obsolete chemical processing methods have been abandoned in favor of the processes listed above. Possible new industrial processes have been developed in the laboratory and additional theoretical methods have been proposed including an electrochemical/ion exchange method , a high temperature pyrprocessing method that utilizes molten salts and molten metals, electrolysis and other new techniques.

          Reprocessing is a dirty dangerous process. The spent fuel must be pulverized behind heavy shielding with protection against dust. When boiled in nitric acid, radioactive gases are generated. After the plutonium and uranium have been extracted, toxic radioactive liquids are left behind which must eventually be solidified for disposal.

          Reprocessing can reduce the volume of waste but does not reduce radioactivity. Studies of the cost of a fuel cycle with reprocessing versus single use with waste disposal have been conducted but are not definitive because it is not possible to exactly define what the costs of disposal will  be. There has been controversy surrounding reprocessing because of possible contributions to nuclear weapon proliferation, vulnerability to terrorism, political problems that arise when attempting to site a reprocessing plant.

Closing the nuclear fuel cycle – from Argonne National Laboratory:

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          When uranium metal is processed to increase the proportion of U-235, a byproduct of the process is a great deal of uranium metal containing smaller amounts of U-235 than the natural proportion of 0.72 %. This byproduct is known as “depleted” uranium(DU). The U-238 in DU emits alpha particles which contain 2 protons and 2 neutrons. These alpha particles only travel a few centimeters in open air and can be blocked by a sheet of paper or plastic, a layer of clothing.

          DU can enter the human body through in breathing, drinking, eating or skin contact and penetration by fragments of uranium munitions. The exact chemical properties of the uranium, the amount of the contamination, the way it enters the body and other factors determine its effect on health. The uranium is absorbed by tissue and distributed by diffusion, blood circulation, air passages and digestive tract and eventually excreted out of the body. All of these processes have their own impact on how the depleted uranium may damage the exposed individual.

          In addition to being mildly radioactive, DU is a toxic heavy metal although not as toxic as mercury. The danger from toxicity is about a million times greater than the danger from radioactivity. DU causes damage to the kidneys as it is eliminated from the body. It can pass the blood-brain barrier and accumulate in the different parts of the brain to cause neurological problems. DU causes problems with bone formation and can inhibit wound healing. The lungs are especially vulnerable to damage by the toxicity of DU with lesions, fibrosis, edema, swelling and hemorrhaging. There can be conjunctivitis, inflammation and ulceration of the eyes from DU. Red blood cell count and hemoglobin can be reduced in the blood.. If pregnant women are exposed, there can be birth defects in the child. The radioactivity of DU can cause lung, lymph and brain cancer.

          The use of DU in munitions has resulted in serious contamination in theaters of war such as Iraq and Afghanistan. When the munitions explode or impact, huge amounts of DU dust are spread over wide areas and then inhaled by soldiers and civilians. There is no effective way to clean up such wide spread contamination. The zone of contamination will spread as wind storms pick up the dust and distribute it more widely. Rain will wash it down streams and rivers into lakes and the sea.

          Since the first Gulf War in 1991, millions of Iraqis have been exposed to higher levels of radiation that normal background radiation in the natural environment from the hundreds of tons of DU munitions used. Since 1995, there has been a documented increase in the number of cases low level radiation exposure related diseases such as leukemia, birth defects, breast cancer and other illnesses in Iraq. The age of leukemia victims has been declining and the higher incidence levels can be correlated with the area with higher concentrations of DU. Gulf War Syndrome may be related to exposure of soldiers to DU.

          There have been charges that the Pentagon has deliberately concealed the amount of DU munitions used in Iraq and Afghanistan, downplayed the extent of the contaminated areas, and dismissed health concerns of the Iraqi people and returning veterans. Various countries and NGOs have made repeated calls for a ban on the use of DU in munitions due to these serious concerns about the health effects of DU dust in theaters of war.

DU in Iraq.PNG