1.
Hanford site
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The Hanford Site is a mostly decommissioned nuclear production complex operated by the United States federal government on the Columbia River in the U. S. state of Washington. The site has been known by names, including, Hanford Project, Hanford Works, Hanford Engineer Works. Established in 1943 as part of the Manhattan Project in Hanford, south-central Washington, the site was home to the B Reactor, the first full-scale plutonium production reactor in the world. Plutonium manufactured at the site was used in the first nuclear bomb, tested at the Trinity site, and in Fat Man, Nuclear technology developed rapidly during this period, and Hanford scientists produced major technological achievements. DOE later found water intruding into at least 14 single-shell tanks, in 2012, DOE discovered a leak also from a double-shell tank caused by construction flaws and corrosion in the bottom, and that 12 double-shell tanks have similar construction flaws. Since then, DOE changed to monitoring single-shell tanks monthly and double-shell tanks every 3 years, in March 2014, DOE announced further delays in the construction of the Waste Treatment Plant, which will affect the schedule for removing waste from the tanks. Intermittent discoveries of undocumented contamination have slowed the pace and raised the cost of cleanup, in 2007, the Hanford site represented two-thirds of the nations high-level radioactive waste by volume. Hanford is currently the most contaminated site in the United States and is the focus of the nations largest environmental cleanup. On November 10,2015, it was designated as part of the Manhattan Project National Historical Park alongside other sites in Oak Ridge, the Hanford Site occupies 586 square miles —roughly equivalent to half of the total area of Rhode Island—within Benton County, Washington. This land is closed to the general public and it is a desert environment receiving under 10 inches of annual precipitation, covered mostly by shrub-steppe vegetation. The Columbia River flows along the site for approximately 50 miles, the original site was 670 square miles and included buffer areas across the river in Grant and Franklin counties. Some of this land has returned to private use and is now covered with orchards. In 2000, large portions of the site were turned over to the Hanford Reach National Monument, the site is divided by function into three main areas. The site is bordered on the southeast by the Tri-Cities, an area composed of Richland, Kennewick, Pasco, and smaller communities. Hanford is an economic base for these cities. The confluence of the Yakima, Snake, and Columbia rivers has been a place for native peoples for centuries. The archaeological record of Native American habitation of this area back over ten thousand years. Tribes and nations including the Yakama, Nez Perce, and Umatilla used the area for hunting, fishing, Native American use of the area continued into the 20th century, even as the tribes were relocated to reservations
2.
High-level radioactive waste
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High-level waste is a type of nuclear waste created by the reprocessing of spent nuclear fuel. It exists in two forms, First and second cycle raffinate and other waste streams created by nuclear reprocessing. Waste formed by vitrification of liquid high-level waste, liquid high-level waste is typically held temporarily in underground tanks pending vitrification. Both spent nuclear fuel and vitrified waste are considered as forms for long term disposal. HLW contains many of the products and transuranic elements generated in the reactor core and is the type of nuclear waste with the highest activity. HLW accounts for over 95% of the total radioactivity produced in the power process. In the US, HLW from reprocessing of spent fuel from power stations amounts to less than 1% of the total volume of US HLW. Some other countries, particularly France, reprocess commercial spent fuel, high-level waste is very radioactive and, therefore, requires special shielding during handling and transport. Initially it also needs cooling, because it generates a great deal of heat, most of the heat, at least after short-lived nuclides have decayed, is from the medium-lived fission products cesium-137 and strontium-90, which have half-lives on the order of 30 years. A typical large 1000 MWe nuclear reactor produces 25–30 tons of spent fuel per year, if the fuel were reprocessed and vitrified, the waste volume would be only about three cubic meters per year, but the decay heat would be almost the same. Spent nuclear fuel is used reactor fuel that is no longer efficient in creating electricity, however, it is still thermally hot, highly radioactive, and potentially harmful. Materials for nuclear weapons are acquired by reprocessing spent nuclear fuel from breeder reactors, reprocessing is a method of chemically treating spent fuel to separate out uranium and plutonium. The byproduct of reprocessing is a highly radioactive sludge residue, high-level radioactive waste is stored for 10 or 20 years in spent fuel pools, and then can be put in dry cask storage facilities. In 1997, in the 20 countries which account for most of the nuclear power generation, spent fuel storage capacity at the reactors was 148,000 tonnes. Away-from-reactor storage capacity was 78,000 tonnes, with 44% utilized, with annual additions of about 12,000 tonnes, issues for final disposal are not urgent. Radioactive waste Low-level waste Transuranic waste mixed waste Into Eternity NRC Backgrounder on Radioactive Waste Fentiman, Audeen W. new York, Taylor & Francis,2002. Second ed. Large, John H. Risks and Hazards arising the Transportation of Irradiated Fuel and Nuclear Materials in the United Kingdom R3144-A1, March 2006
3.
Nuclear reactor
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This article is a subarticle of Nuclear power. A nuclear reactor, formerly known as a pile, is a device used to initiate. Nuclear reactors are used at power plants for electricity generation. Heat from nuclear fission is passed to a fluid, which runs through steam turbines. These either drive a ships propellers or turn electrical generators, Nuclear generated steam in principle can be used for industrial process heat or for district heating. Some reactors are used to produce isotopes for medical and industrial use, some are run only for research. As of April 2014, the IAEA reports there are 435 nuclear power reactors in operation, when a large fissile atomic nucleus such as uranium-235 or plutonium-239 absorbs a neutron, it may undergo nuclear fission. The heavy nucleus splits into two or more nuclei, releasing kinetic energy, gamma radiation, and free neutrons. A portion of neutrons may later be absorbed by other fissile atoms and trigger further fission events, which release more neutrons. This is known as a chain reaction. To control such a chain reaction, neutron poisons and neutron moderators can change the portion of neutrons that will go on to cause more fission. Nuclear reactors generally have automatic and manual systems to shut the fission reaction down if monitoring detects unsafe conditions, commonly-used moderators include regular water, solid graphite and heavy water. Some experimental types of reactor have used beryllium, and hydrocarbons have been suggested as another possibility, the reactor core generates heat in a number of ways, The kinetic energy of fission products is converted to thermal energy when these nuclei collide with nearby atoms. The reactor absorbs some of the rays produced during fission. Heat is produced by the decay of fission products and materials that have been activated by neutron absorption. This decay heat-source will remain for some even after the reactor is shut down. A kilogram of uranium-235 converted via nuclear processes releases approximately three times more energy than a kilogram of coal burned conventionally. A nuclear reactor coolant — usually water but sometimes a gas or a metal or molten salt — is circulated past the reactor core to absorb the heat that it generates
4.
Columbia River
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The Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, Canada and it flows northwest and then south into the US state of Washington, then turns west to form most of the border between Washington and the state of Oregon before emptying into the Pacific Ocean. The river is 1,243 miles long, and its largest tributary is the Snake River and its drainage basin is roughly the size of France and extends into seven US states and a Canadian province. By volume, the Columbia is the fourth-largest river in the United States, the rivers heavy flow and relatively steep gradient gives it tremendous potential for the generation of electricity. The Columbia and its tributaries have been central to the regions culture and they have been used for transportation since ancient times, linking the many cultural groups of the region. The river system hosts many species of fish, which migrate between freshwater habitats and the saline waters of the Pacific Ocean. In the following decades, fur trading companies used the Columbia as a key transportation route, steamships along the river linked communities and facilitated trade, the arrival of railroads in the late 19th century, many running along the river, supplemented these links. Since the late 19th century, public and private sectors have developed the river. The development, commonly referred to as taming or harnessing of the river, has been massive, to aid ship and barge navigation, locks have been built along the lower Columbia and its tributaries, and dredging has opened, maintained, and enlarged shipping channels. Since the early 20th century, dams have been built across the river for the purposes of power generation, navigation, irrigation, and flood control. Today, a reservoir lies along nearly every US mile of the once free-flowing river. Production of nuclear power has taken place at two sites along the river, plutonium for nuclear weapons was produced for decades at the Hanford Site, which is now the most contaminated nuclear site in the US. All these developments have had a impact on river environments, mainly through industrial pollution. The Columbia begins its 1, 243-mile journey in the southern Rocky Mountain Trench in British Columbia, Columbia Lake –2,690 feet above sea level – and the adjoining Columbia Wetlands form the rivers headwaters. The trench is a broad, deep, and long glacial valley between the Canadian Rockies and the Columbia Mountains in BC. Rounding the northern end of the Selkirk Mountains, the river turns south through a region known as the Big Bend Country, passing through Revelstoke Lake. Revelstoke, the Big Bend, and the Columbia Valley combined are referred to in BC parlance as the Columbia Country. Below the Arrow Lakes, the Columbia passes the cities of Castlegar, located at the Columbias confluence with the Kootenay River, the Pend Oreille River joins the Columbia about 2 miles north of the US–Canada border
5.
Fukushima nuclear disaster
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The Fukushima Daiichi nuclear disaster was an energy accident at the Fukushima I Nuclear Power Plant in Fukushima, initiated primarily by the tsunami following the Tōhoku earthquake on 11 March 2011. Immediately after the earthquake, the reactors automatically shut down their sustained fission reactions. However, the disabled the emergency generators that would have provided power to control. The insufficient cooling led to three nuclear meltdowns, hydrogen-air chemical explosions, and the release of material in Units 1,2 and 3 from 12 March to 15 March. Loss of cooling also caused the pool for storing spent fuel from Reactor 4 to overheat on 15 March due to the heat from the fuel rods. On 12 October 2012, TEPCO admitted for the first time that it had failed to take measures for fear of inviting lawsuits or protests against its nuclear plants. However, an estimated 1,600 deaths are believed to have occurred due to the resultant evacuation conditions, There are no clear plans for decommissioning the plant, but the plant management estimate is 30 or 40 years. Radiation levels of about 650 sieverts per hour have been detected in the containment vessel of reactor No.2, the Fukushima I Nuclear Power Plant comprised six separate boiling water reactors originally designed by General Electric and maintained by the Tokyo Electric Power Company. At the time of the Tōhoku earthquake on 11 March 2011, however, their spent fuel pools still required cooling. As the reactors were unable to power to run their own coolant pumps, emergency diesel generators came online, as designed, to power electronics. These operated nominally until the destroyed the generators for reactors 1–5. The largest tsunami wave was 13 meters high and hit 50 minutes after the earthquake, overwhelming the plants seawall. The moment of impact was recorded by a camera, water quickly flooded the low-lying rooms in which the emergency generators were housed. The flooded diesel generators failed soon afterwards, resulting in a loss of power to the coolant water pumps. The fuel rods would become hot enough to melt during the decay time period if an adequate heat sink was not available. After the secondary emergency pumps ran out, one day after the tsunami,12 March, the pumps stopped. The insufficient cooling led to meltdowns in reactors 1,2, and 3. It is estimated that the hot zirconium fuel cladding-water reaction in reactors 1–3 produced 800 to 1000 kilograms of hydrogen gas each
6.
Fukushima disaster cleanup
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Decontamination and decommissioning work is expected to continue for between ten and thirty years from the date of the disaster. The affected reactors were adjacent to one another and accident management was much more difficult because of the number of simultaneous hazards concentrated in a small area. Failure of emergency following the tsunami resulted in loss of coolant from each reactor, hydrogen explosions damaging the reactor buildings. Plant workers were put in the position of trying to cope simultaneously with core meltdowns at three reactors and exposed fuel pools at three units, automated cooling systems were installed within 3 months. A fabric cover was built to protect the buildings from storms, new detectors were installed at the plant to track emissions of xenon gas. Filters were installed to reduce contaminants from escaping the area of the plant into the area or atmosphere, cement has been laid near to the seabed to control contaminants from accidentally entering the ocean. Cleanup costs will not be known until the cleanup is completed. Decommissioning the plant is evaluated to cost tens of billions of dollars, at the time of the initial event,50 TEPCO employees remained onsite in the immediate aftermath to work to stabilize the plant and begin cleanup. Initially, TEPCO did not put forward a strategy to control of the situation in the reactors. Helmut Hirsch, a German physicist and nuclear expert, said they are improvising with tools that were not intended for this type of situation. Previously, TEPCO publicly committed to installing new emergency generators 20 m above sea level, Toshiba and Hitachi had both proposed plans for shuttering the facility. Cold shutdown was accomplished on December 11,2011, from that point cooling was no longer required, but maintenance was still required to control large water leaks. Long term plans for Units 5 and 6 have not been announced, on 5 May 2011, workers were able to enter reactor buildings for the first time since the accident. The workers began to install air filtration systems to clean air of radioactive materials to allow workers to install water cooling systems. Japanese reactor maker Toshiba said it could decommission the earthquake-damaged Fukushima nuclear power plant in about 10 years, as a comparison, at Three Mile Island the vessel of the partially melted core was first opened 11 years after the accident, with cleanup activities taking several more years. TEPCO announced it restored the automated cooling systems in the reactors in about three months, and had the reactors put into cold shutdown status in six months. First estimates included costs as high as ¥1 trillion, as cited by the Japanese Prime Minister at the time, however, this estimate was made before the scope of the problem was known. It seems that the contamination was less than feared, No strontium is detectable in the soil, and though the crops of the year of the disaster were contaminated, the crops produced by the area now are safe for human consumption
7.
Radioactive decay
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A material containing such unstable nuclei is considered radioactive. Certain highly excited short-lived nuclear states can decay through neutron emission, or more rarely, however, for a collection of atoms, the collections expected decay rate is characterized in terms of their measured decay constants or half-lives. This is the basis of radiometric dating, the half-lives of radioactive atoms have no known upper limit, spanning a time range of over 55 orders of magnitude, from nearly instantaneous to far longer than the age of the universe. A radioactive nucleus with spin can have no defined orientation. If there are multiple particles produced during a single decay, as in decay, their relative angular distribution. Such a parent process could be a previous decay, or a nuclear reaction, the decaying nucleus is called the parent radionuclide, and the process produces at least one daughter nuclide. Except for gamma decay or internal conversion from an excited state. When the number of changes, an atom of a different chemical element is created. The first decay processes to be discovered were alpha decay, beta decay, alpha decay occurs when the nucleus ejects an alpha particle. This is the most common process of emitting nucleons, but highly excited nuclei can eject single nucleons, or in the case of cluster decay, specific light nuclei of other elements. Beta decay occurs when the nucleus emits an electron or positron, the nucleus may capture an orbiting electron, causing a proton to convert into a neutron in a process called electron capture. All of these result in a well-defined nuclear transmutation. By contrast, there are radioactive decay processes that do not result in a nuclear transmutation, another type of radioactive decay results in products that vary, appearing as two or more fragments of the original nucleus with a range of possible masses. For a summary table showing the number of stable and radioactive nuclides in each category, there are 29 naturally occurring chemical elements on Earth that are radioactive. They are those that contain 34 radionuclides that date before the time of formation of the solar system, well-known examples are uranium and thorium, but also included are naturally occurring long-lived radioisotopes, such as potassium-40. Radioactivity was discovered in 1896 by the French scientist Henri Becquerel and these materials glow in the dark after exposure to light, and he suspected that the glow produced in cathode ray tubes by X-rays might be associated with phosphorescence. He wrapped a photographic plate in black paper and placed various phosphorescent salts on it, all results were negative until he used uranium salts. The uranium salts caused a blackening of the plate in spite of the plate being wrapped in black paper and these radiations were given the name Becquerel Rays
8.
International Atomic Energy Agency
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The IAEA was established as an autonomous organization on 29 July 1957. Though established independently of the United Nations through its own treaty, the IAEA Statute. The IAEA has its headquarters in Vienna, the IAEA has two Regional Safeguards Offices which are located in Toronto, Canada, and in Tokyo, Japan. The IAEA also has two liaison offices which are located in New York City, United States, and in Geneva, in addition, the IAEA has three laboratories located in Vienna and Seibersdorf, Austria, and in Monaco. The IAEA serves as a forum for scientific and technical cooperation in the peaceful use of nuclear technology. The IAEA and its former Director General, Mohamed ElBaradei, were awarded the Nobel Peace Prize on 7 October 2005. The IAEAs current Director General is Yukiya Amano and this agency would establish a kind of nuclear bank. The United States also called for a scientific conference on all of the peaceful aspects of nuclear power. By November 1954, it had become clear that the Soviet Union would reject any international custody of fissile material, from 8 to 20 August 1955, the United Nations held the International Conference on the Peaceful Uses of Atomic Energy in Geneva, Switzerland. The Statute of the IAEA was approved on 23 October 1956, congressman W. Sterling Cole served as the IAEAs first Director General from 1957 to 1961. Blix was succeeded as Director General by Mohamed ElBaradei of Egypt, beginning in 1986, in response to the nuclear reactor explosion and disaster near Chernobyl, Ukraine, the IAEA increased its efforts in the field of nuclear safety. The same happened after the 2011 Fukushima disaster in Fukushima, Japan, both the IAEA and its then Director General, ElBaradei, were awarded the Nobel Peace Prize in 2005. On 2 July 2009, Yukiya Amano of Japan was elected as the Director General for the IAEA, defeating Abdul Samad Minty of South Africa and Luis E. Echávarri of Spain. On 3 July 2009, the Board of Governors voted to appoint Yukiya Amano by acclamation and he took office on 1 December 2009. The IAEAs mission is guided by the interests and needs of Member States, strategic plans, unlike most other specialized international agencies, the IAEA does much of its work with the Security Council, and not with the United Nations Economic and Social Council. The structure and functions of the IAEA are defined by its founding document, the IAEA has three main bodies, the Board of Governors, the General Conference, and the Secretariat. The IAEA exists to pursue the safe, secure and peaceful uses of nuclear sciences, the IAEA recognizes knowledge as the nuclear energy industry’s most valuable asset and resource, without which the industry cannot operate safely and economically. Following the IAEA General Conference since 2002 resolutions the Nuclear Knowledge Management, in 2004, the IAEA developed a Programme of Action for Cancer Therapy
9.
Ionising radiation
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Ionizing radiation is radiation that carries enough energy to free electrons from atoms or molecules, thereby ionizing them. Ionizing radiation is made up of energetic particles, ions or atoms moving at high speeds. The boundary between ionizing and non-ionizing electromagnetic radiation that occurs in the ultraviolet is not sharply defined, since different molecules, conventional definition places the boundary at a photon energy between 10 eV and 33 eV in the ultraviolet. Typical ionizing subatomic particles from radioactivity include alpha particles, beta particles, almost all products of radioactive decay are ionizing because the energy of radioactive decay is typically far higher than that required to ionize. Cosmic rays are generated by stars and certain events such as supernova explosions. Cosmic rays may also produce radioisotopes on Earth, which in turn decay, cosmic rays and the decay of radioactive isotopes are the primary sources of natural ionizing radiation on Earth referred to as background radiation. Ionizing radiation can also be generated artificially using X-ray tubes, particle accelerators, ionizing radiation is invisible and not directly detectable by human senses, so radiation detection instruments such as Geiger counters are required to detect it. However, it can cause emission of light upon interaction with matter, such as in Cherenkov radiation. Exposure to ionizing radiation damage to living tissue, and can result in mutation, radiation sickness, cancer. Ionizing radiation is categorized by the nature of the particles or electromagnetic waves that create the ionizing effect and these have different ionization mechanisms, and may be grouped as directly or indirectly ionizing. Any charged massive particle can ionize atoms directly by fundamental interaction through the Coulomb force if it carries sufficient kinetic energy and this includes atomic nuclei, electrons, muons, charged pions, protons, and energetic charged nuclei stripped of their electrons. When moving at relativistic speeds these particles have enough energy to be ionizing. For example, an alpha particle is ionizing, but moves at about 5% c. Natural cosmic rays are made up primarily of protons but also include heavier atomic nuclei like helium ions. Pions can also be produced in large amounts in particle accelerators, alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus. Alpha particle emissions are produced in the process of alpha decay. Alpha particles are named after the first letter in the Greek alphabet, the symbol for the alpha particle is α or α2+. Because they are identical to helium nuclei, they are sometimes written as He2+ or 4 2He2+ indicating a Helium ion with a +2 charge
10.
Alpha particle
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Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus. They are generally produced in the process of decay. Alpha particles are named after the first letter in the Greek alphabet, the symbol for the alpha particle is α or α2+. Because they are identical to helium nuclei, they are sometimes written as He2+ or 4 2He2+ indicating a helium ion with a +2 charge. If the ion gains electrons from its environment, the particle can be written as a normal helium atom 4 2He. Some science authors may use doubly ionized helium nuclei and alpha particles as interchangeable terms, the nomenclature is not well defined, and thus not all high-velocity helium nuclei are considered by all authors to be alpha particles. As with beta and gamma rays/particles, the used for the particle carries some mild connotations about its production process and energy. Thus, alpha particles may be used as a term when referring to stellar helium nuclei reactions. A higher energy version of alphas than produced in alpha decay is a product of an uncommon nuclear fission result called ternary fission. However, helium nuclei produced by particle accelerators are less likely to be referred to as alpha particles, alpha particles, like helium nuclei, have a net spin of zero. Due to the mechanism of their production in standard alpha radioactive decay, alpha particles generally have an energy of about 5 MeV. They are a highly ionizing form of radiation, and have low penetration depth. They are able to be stopped by a few centimeters of air, however, so-called long range alpha particles from ternary fission are three times as energetic, and penetrate three times as far. To a lesser extent, this is true of very high-energy helium nuclei produced by particle accelerators. The best-known source of particles is alpha decay of heavier atoms. When an atom emits an alpha particle in alpha decay, the mass number decreases by four due to the loss of the four nucleons in the alpha particle. The atomic number of the atom goes down by two, as a result of the loss of two protons – the atom becomes a new element. Examples of this sort of nuclear transmutation are when uranium becomes thorium, or radium becomes radon gas, alpha particles are commonly emitted by all of the larger radioactive nuclei such as uranium, thorium, actinium, and radium, as well as the transuranic elements
11.
Beta particle
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Two forms of beta decay, β− and β+, respectively produce electrons and positrons. Beta particles are a type of ionizing radiation, the neutron turns into a proton through the emission of a virtual W− boson. At the quark level, W− emission turns a down quark into an up quark, the virtual W− boson then decays into an electron and an antineutrino. Beta decay commonly occurs among the neutron-rich fission byproducts produced in nuclear reactors, free neutrons also decay via this process. Both of these contribute to the copious numbers of beta rays. The daughter nucleus is a lower-energy state, of the three common types of radiation given off by radioactive materials, alpha, beta and gamma, beta has the medium penetrating power and the medium ionising power. Although the beta particles given off by different radioactive materials vary in energy, shielding composed of materials with lower atomic weight generates gammas with lower energy, making such shields somewhat more effective per unit mass than ones made of high-Z materials such as lead. Being composed of charged particles, beta radiation is more strongly ionizing than gamma radiation, when passing through matter, a beta particle is decelerated by electromagnetic interactions and may give off bremsstrahlung x-rays. In water, beta radiation from nuclear fission products typically exceeds the speed of light in that material. The intense beta radiation from the rods of pool-type reactors can thus be visualized through the transparent water that covers. The ionizing or excitation effects of particles on matter are the fundamental processes by which radiometric detection instruments detect. The ionization of gas is used in ion chambers and Geiger-Muller counters, beta particles can be used to treat health conditions such as eye and bone cancer and are also used as tracers. Strontium-90 is the material most commonly used to produce beta particles, beta particles are also used in quality control to test the thickness of an item, such as paper, coming through a system of rollers. Some of the radiation is absorbed while passing through the product. If the product is too thick or thin, a correspondingly different amount of radiation will be absorbed. A computer program monitoring the quality of the paper will then move the rollers to change the thickness of the final product. An illumination device called a betalight contains tritium and a phosphor, as tritium decays, it emits beta particles, these strike the phosphor, causing the phosphor to give off photons, much like the cathode ray tube in a television. Beta-plus decay of a radioactive isotope is the source of the positrons used in positron emission tomography
12.
Gamma ray
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Gamma ray, denoted by the lower-case Greek letter gamma, is penetrating electromagnetic radiation of a kind arising from the radioactive decay of atomic nuclei. It consists of photons in the highest observed range of photon energy, paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation gamma rays, Rutherford had previously discovered two other types of radioactive decay, which he named alpha and beta rays. Gamma rays are able to ionize atoms, and are thus biologically hazardous. The decay of a nucleus from a high energy state to a lower energy state. Natural sources of gamma rays on Earth are observed in the decay of radionuclides. There are rare terrestrial natural sources, such as lightning strikes and terrestrial gamma-ray flashes, However, a large fraction of such astronomical gamma rays are screened by Earths atmosphere and can only be detected by spacecraft. Gamma rays typically have frequencies above 10 exahertz, and therefore have energies above 100 keV and wavelengths less than 10 picometers, However, this is not a strict definition, but rather only a rule-of-thumb description for natural processes. Electromagnetic radiation from radioactive decay of nuclei is referred to as gamma rays no matter its energy. This radiation commonly has energy of a few hundred keV, in astronomy, gamma rays are defined by their energy, and no production process needs to be specified. The energies of gamma rays from astronomical sources range to over 10 TeV, a notable example is the extremely powerful bursts of high-energy radiation referred to as long duration gamma-ray bursts, of energies higher than can be produced by radioactive decay. These bursts of gamma rays are thought to be due to the collapse of stars called hypernovae, the first gamma ray source to be discovered historically was the radioactive decay process called gamma decay. In this type of decay, a nucleus emits a gamma ray almost immediately upon formation. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, However, Villard did not consider naming them as a different fundamental type. Rutherford also noted that gamma rays were not deflected by a field, another property making them unlike alpha. Gamma rays were first thought to be particles with mass, like alpha, Rutherford initially believed that they might be extremely fast beta particles, but their failure to be deflected by a magnetic field indicated that they had no charge. In 1914, gamma rays were observed to be reflected from crystal surfaces, Rutherford and his coworker Edward Andrade measured the wavelengths of gamma rays from radium, and found that they were similar to X-rays, but with shorter wavelengths and higher frequency. This was eventually recognized as giving them more energy per photon
13.
Neutron
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The neutron is a subatomic particle, symbol n or n0, with no net electric charge and a mass slightly larger than that of a proton. Protons and neutrons, each with approximately one atomic mass unit, constitute the nucleus of an atom. Their properties and interactions are described by nuclear physics, the nucleus consists of Z protons, where Z is called the atomic number, and N neutrons, where N is the neutron number. The atomic number defines the properties of the atom. The terms isotope and nuclide are often used synonymously, but they are chemical and nuclear concepts, the atomic mass number, symbol A, equals Z+N. For example, carbon has atomic number 6, and its abundant carbon-12 isotope has 6 neutrons, some elements occur in nature with only one stable isotope, such as fluorine. Other elements occur with many stable isotopes, such as tin with ten stable isotopes, even though it is not a chemical element, the neutron is included in the table of nuclides. Within the nucleus, protons and neutrons are bound together through the nuclear force, neutrons are produced copiously in nuclear fission and fusion. They are a contributor to the nucleosynthesis of chemical elements within stars through fission, fusion. The neutron is essential to the production of nuclear power, in the decade after the neutron was discovered in 1932, neutrons were used to induce many different types of nuclear transmutations. These events and findings led to the first self-sustaining nuclear reactor, free neutrons, or individual neutrons free of the nucleus, are effectively a form of ionizing radiation, and as such, are a biological hazard, depending upon dose. A small natural background flux of free neutrons exists on Earth, caused by cosmic ray showers. Dedicated neutron sources like neutron generators, research reactors and spallation sources produce free neutrons for use in irradiation, neutrons and protons are both nucleons, which are attracted and bound together by the nuclear force to form atomic nuclei. The nucleus of the most common isotope of the atom is a lone proton. The nuclei of the hydrogen isotopes deuterium and tritium contain one proton bound to one. All other types of nuclei are composed of two or more protons and various numbers of neutrons. The most common nuclide of the chemical element lead, 208Pb has 82 protons and 126 neutrons. The free neutron has a mass of about 1. 675×10−27 kg, the neutron has a mean square radius of about 0. 8×10−15 m, or 0.8 fm, and it is a spin-½ fermion
14.
Containment building
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A containment building, in its most common usage, is a reinforced steel or lead structure enclosing a nuclear reactor. It is designed, in any emergency, to contain the escape of steam or gas to a maximum pressure in the range of 275 to 550 kPa. Each nuclear plant in the US is designed to certain conditions which are spelled out as Design Basis Accidents in the Final Safety Analysis Report. The FSAR is available for viewing, usually at a public library near the nuclear plant. The containment building itself is typically a steel structure enclosing the reactor normally sealed off from the outside atmosphere. The steel is either free-standing or attached to the missile shield. This, combined with further failures, caused the release of up to 13 million curies of radioactive gas to atmosphere during the accident and these systems were necessary to keep the fuel cool after the reactor had been shut down. Hydrogen leaking from the containment mixed with air into a mixture which resulted in explosions in Unit 1,3 and 4. Containment systems for power reactors are distinguished by size, shape, materials used. The kind of containment used is determined by the type of reactor, generation of the reactor, suppression systems are critical to safety analysis and greatly affect the size of containment. Suppression refers to condensing the steam after a break has released it from the cooling system. Because decay heat does not go quickly, there must be some long term method of suppression. There are several designs, but for safety-analysis purposes containments are categorized as either large-dry, sub-atmospheric. For a pressurized water reactor, the containment also encloses the steam generators and the pressurizer, the missile shield around it is typically a tall cylindrical or domed building. Early designs including Siemens, Westinghouse, and Combustion Engineering had a mostly can-like shape built with reinforced concrete, as reactor designs have evolved, many nearly spherical containment designs for PWRs have also been constructed. Depending on the used, this is the most apparently logical design because a sphere is the best structure for simply containing a large pressure. Most current PWR designs involve some combination of the two, with a lower part and a half-spherical top. The spent fuel pool is outside of the containment building in most PWR designs, modern designs have also shifted more towards using steel containment structures
15.
Nuclear fuel
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Nuclear fuel is a substance that is used in nuclear power stations to produce heat to power turbines. Heat is created when nuclear fuel undergoes nuclear fission, most nuclear fuels contain heavy fissile elements that are capable of nuclear fission, such as uranium-235 or plutonium-239. When the unstable nuclei of atoms are hit by a slow-moving neutron, they split. These neutrons then go on to split more nuclei and this creates a self-sustaining chain reaction that is controlled in a nuclear reactor, or uncontrolled in a nuclear weapon. The processes involved in mining, refining, purifying, using, Nuclear fuel has the highest energy density of all practical fuel sources. Uranium dioxide is a black semiconducting solid and it can be made by reacting uranyl nitrate with a base to form a solid. It is heated to form U3O8 that can then be converted by heating in an argon / hydrogen mixture to form UO2, the UO2 is then mixed with an organic binder and pressed into pellets, these pellets are then fired at a much higher temperature to sinter the solid. The aim is to form a solid which has few pores. The thermal conductivity of uranium dioxide is low compared with that of zirconium metal. It is important to note that the corrosion of uranium dioxide in an environment is controlled by similar electrochemical processes to the galvanic corrosion of a metal surface. Mixed oxide, or MOX fuel, is a blend of plutonium, MOX fuel is an alternative to low enriched uranium fuel used in the light water reactors which predominate nuclear power generation. Some concern has been expressed that used MOX cores will introduce new disposal challenges, reprocessing of commercial nuclear fuel to make MOX was done in the Sellafield MOX Plant. As of 2015, MOX fuel is made in France, and to an extent in Russia, India. China plans to develop fast breeder reactors and reprocessing, reprocessing of spent commercial-reactor nuclear fuel has not been permitted in the United States due to nonproliferation considerations. It behaves like U-235 and its fission releases a similar amount of energy, the higher the burn-up, the more plutonium in the spent fuel, but the lower the fraction of fissile plutonium. Typically about one percent of the used fuel discharged from a reactor is plutonium, worldwide, some 70 tonnes of plutonium contained in used fuel is removed when refueling reactors each year. Metal fuels have the advantage of a higher heat conductivity than oxide fuels. Metal fuels have a history of use, stretching from the Clementine reactor in 1946 to many test
16.
Fission product
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Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the release of heat energy. The two smaller nuclei are the fission products, about 0. 2% to 0. 4% of fissions are ternary fissions, producing a third light nucleus such as helium-4 or tritium. The fission products themselves are often unstable and radioactive, due to being relatively neutron-rich for their atomic number and this releases additional energy in the form of beta particles, antineutrinos, and gamma rays. Thus, fission events normally result in radiation and antineutrinos. Many of these nuclides have a very short half-life, and therefore are very radioactive, for instance, strontium-90, strontium-89 and strontium-94 are all fission products, they are produced in similar quantities, and each nucleus decays by shooting off one beta particle. But Sr-90 has a 30-year half-life, Sr-89 a 50. 5-day half-life, the same number of atoms of Sr-89 will decay 10,600 times faster than Sr-90, and Sr-94 will do so 915 million times faster. It is these short-half-life nuclides that make spent fuel so dangerous, in addition to generating much heat, immediately after the reactor itself has been shut down. The most radioactive also decay the fastest, after 50 days, Sr-94 has had 58,000 half-lives and is gone, Sr-89 is at half its original quantity. As there are hundreds of different nuclides created, the radioactivity level fades quickly. The sum of the mass of the two atoms produced by the fission of one fissile atom is always less than the atomic mass of the original atom. Since the nuclei that can undergo fission are particularly neutron-rich. The initial fission products therefore may be unstable and typically undergo beta decay to move towards a stable configuration, a few neutron-rich and short-lived initial fission products decay by ordinary beta decay, followed by immediate emission of a neutron by the excited daughter-product. This process is the source of so-called delayed neutrons, which play an important role in control of a nuclear reactor, the first beta decays are rapid and may release high energy beta particles or gamma radiation. However, as the fission products approach stable nuclear conditions, the last one or two decays may have a long half-life and release less energy. Fission products have half-lives of 90 years or less, except for seven long-lived fission products that have lives of 211,100 years. This behavior of pure fission products with actinides removed, contrasts with the decay of fuel that still contains actinides and this fuel is produced in the so-called open nuclear fuel cycle. A number of these actinides have half lives in the range of about 100 to 200,000 years
17.
Radioactive material
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A radionuclide is an atom that has excess nuclear energy, making it unstable. During those processes, the radionuclide is said to undergo radioactive decay, the unstable nucleus is more stable following the emission, but will sometimes undergo further decay. Radioactive decay is a process at the level of single atoms. However, for a collection of atoms of an element the decay rate. The range of the half-lives of radioactive atoms have no known limits, Radionuclides occur naturally and are artificially produced in nuclear reactors, cyclotrons, particle accelerators or radionuclide generators. There are about 730 radionuclides with half-lives longer than 60 minutes, with the longest half lives are the 32 primordial radionuclides that have survived from the creation of the Solar System. Over 60 further radionuclides are detectable in nature, either as daughters of these, more than 2400 radionuclides have half-lives less than 60 minutes. Most of those are produced artificially, and have very short half-lives. For comparison, there are about 254 stable nuclides, even the lightest element, hydrogen, has a well-known radionuclide, tritium. Elements heavier than lead, and the elements technetium and promethium, unplanned exposure to radionuclides generally has a harmful effect on living organisms including humans, although low levels of exposure occur naturally without harm. However, radionuclides with suitable properties are used in medicine for both diagnosis and treatment. An imaging tracer made with radionuclides is called a radioactive tracer, a pharmaceutical drug made with radionuclides is called a radiopharmaceutical. On Earth, naturally occurring radionuclides fall into three categories, primordial radionuclides, secondary radionuclides, and cosmogenic radionuclides, Radionuclides are produced in stellar nucleosynthesis and supernova explosions along with stable nuclides. Most decay quickly but can still be observed astronomically and can play a part in understanding astronomic processes, primordial radionuclides, such as uranium and thorium, exist in the present time because their half-lives are so long they have not yet completely decayed. It is possible decay may be observed in other nuclides adding to this list of primordial radionuclides, secondary radionuclides are radiogenic isotopes derived from the decay of primordial radionuclides. They have shorter half-lives than primordial radionuclides and they arise in the decay chain of the primordial isotopes thorium-232, uranium-238 and uranium-235. Examples include the natural isotopes of polonium and radium, cosmogenic isotopes, such as carbon-14, are present because they are continually being formed in the atmosphere due to cosmic rays. Many of these radionuclides exist only in trace amounts in nature, secondary radionuclides will occur in proportion to their half-lives, so short-lived ones will be very rare
18.
Uranyl nitrate
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Uranyl nitrate is a water soluble yellow uranium salt. The yellow-green crystals of dioxouranium nitrate hexahydrate are triboluminescent, Uranyl nitrate can be prepared by reaction of uranium salts with nitric acid. It is soluble in water, ethanol, acetone, and ether, during the first half of the 19th century, many photosensitive metal salts had been identified as candidates for photographic processes, among them uranyl nitrate. The prints thus produced were alternately referred to as uranium prints, urbanities, the first uranium printing processes were invented by a Scotsman, J. Charles Burnett, between 1855 and 1857, and used this compound as the sensitive salt. Uranotypes can vary from print to print from a neutral, brown russet to strong Bartolozzi red. Surviving prints are slightly radioactive, a property which serves as a means of identifying them. Uranium papers were manufactured commercially at least until the end of the 19th century, vanishing in the face of the superior sensitivity, nevertheless, between the 1930s through the 1950s Kodak Books still described a uranium toner using uranium nitrate hexahydrate. Some alternative process photographers including artists Blake Ferris and Robert Schramm continue to make uranotype prints today, along with uranyl acetate it is used as a negative stain for viruses in electron microscopy, in tissue samples it stabilizes nucleic acids and cell membranes. Uranyl nitrate was used to fuel Aqueous Homogeneous Reactors in the 1950s, however it proved too corrosive in this application, and the experiments were abandoned. Uranyl nitrate is an oxidizing and highly toxic compound, when ingested, it causes severe renal insufficiency and acute tubular necrosis and is a lymphocyte mitogen. Target organs include the kidneys, liver, lungs and brain and it also represents a severe fire and explosion risk when heated or subjected to shock in contact with oxidizable substances. URANIUM DAYS, Notes On Uranium Photography Chemical Database – Uranyl nitrate, solid
19.
Bikini Atoll
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Bikini Atoll is an atoll in the Marshall Islands which consists of 23 islands totaling 3.4 square miles surrounding a deep 229. 4-square-mile central lagoon. It is at the end of the Ralik Chain, approximately 87 kilometres northwest of Ailinginae Atoll and 850 kilometres northwest of Majuro. Within Bikini Atoll, Bikini, Eneu, Nam, and Enidrik islands comprise just over 70% of the land area, Bikini and Eneu are the only islands of the atoll that hosted a permanent population. Bikini Island is the northeastern most and largest islet, before World War II, the atoll was known by its German name, Eschscholtz Atoll. The islands English name is derived from the German colonial name Bikini given to the atoll when it was part of German New Guinea. The German name is transliterated from the Marshallese name for the island, Pikinni, Pik meaning surface and Ni meaning coconut, before the advent of Western influence, the Bikini islanders sustenance-based lifestyle was based on cultivating native plants and eating shellfish and fish. They were skilled builders and navigators, sailing the two-hulled proa to and from islets around the Bikini. The islanders were relatively isolated and had developed a society bound by close extended family association and tradition. Every lagoon was led by a king and queen and a following of chieftains, some of the leaders maintained Asian-style bungalows and maintained servants, including secretaries, maids, and valets. The islanders worked the plantations under the watchful eye of the Japanese. Chiefs could retain as much as $20,000 per year, the Marshall islanders were formerly aggressive, but the influence of the mission churches eliminated most conflict. They took pride in extending hospitality to one another, even distant relatives, the men wore a fringe skirt of native materials about 25 to 30 inches long. Women traditionally wore two mats about a square each, made by weaving pandanus and hibiscus leaves together. The Christian missionaries who began arriving in the late 19th century influenced the islanders notions of modesty, in 1919, a visitor reported that Marshall Islands women are perfect models of prudery. Not one would think of exposing her ankles, women in the Marshall Islands today are still very modest. They believe that a womans thighs and shoulders should be covered, women generally wear cotton muʻumuʻus or similar clothing that covers most of the body. Personal health is never discussed except within the family, and women are especially private about female-related health issues, Marshall island women swim in muʻumuʻus which are made of a fine polyester that quickly dries. In the capital of Majuro, revealing cocktail dresses are inappropriate for both islanders and guests, with the increasing influence of Western media, the younger generation may wear shorts, though the older generation equates shorts with loose morals
20.
Fukushima Daiichi nuclear disaster
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The Fukushima Daiichi nuclear disaster was an energy accident at the Fukushima I Nuclear Power Plant in Fukushima, initiated primarily by the tsunami following the Tōhoku earthquake on 11 March 2011. Immediately after the earthquake, the reactors automatically shut down their sustained fission reactions. However, the disabled the emergency generators that would have provided power to control. The insufficient cooling led to three nuclear meltdowns, hydrogen-air chemical explosions, and the release of material in Units 1,2 and 3 from 12 March to 15 March. Loss of cooling also caused the pool for storing spent fuel from Reactor 4 to overheat on 15 March due to the heat from the fuel rods. On 12 October 2012, TEPCO admitted for the first time that it had failed to take measures for fear of inviting lawsuits or protests against its nuclear plants. However, an estimated 1,600 deaths are believed to have occurred due to the resultant evacuation conditions, There are no clear plans for decommissioning the plant, but the plant management estimate is 30 or 40 years. Radiation levels of about 650 sieverts per hour have been detected in the containment vessel of reactor No.2, the Fukushima I Nuclear Power Plant comprised six separate boiling water reactors originally designed by General Electric and maintained by the Tokyo Electric Power Company. At the time of the Tōhoku earthquake on 11 March 2011, however, their spent fuel pools still required cooling. As the reactors were unable to power to run their own coolant pumps, emergency diesel generators came online, as designed, to power electronics. These operated nominally until the destroyed the generators for reactors 1–5. The largest tsunami wave was 13 meters high and hit 50 minutes after the earthquake, overwhelming the plants seawall. The moment of impact was recorded by a camera, water quickly flooded the low-lying rooms in which the emergency generators were housed. The flooded diesel generators failed soon afterwards, resulting in a loss of power to the coolant water pumps. The fuel rods would become hot enough to melt during the decay time period if an adequate heat sink was not available. After the secondary emergency pumps ran out, one day after the tsunami,12 March, the pumps stopped. The insufficient cooling led to meltdowns in reactors 1,2, and 3. It is estimated that the hot zirconium fuel cladding-water reaction in reactors 1–3 produced 800 to 1000 kilograms of hydrogen gas each
21.
Chernobyl disaster
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The Chernobyl disaster, also referred to as the Chernobyl accident, was a catastrophic nuclear accident. Practically all of this material would then go on to fall-out/precipitate onto much of the surface of the western USSR. The Chernobyl accident dominates the Energy accidents sub-category, of most disastrous nuclear power plant accident in history, both in terms of cost and casualties. It is one of two nuclear energy accidents classified as a level 7 event on the International Nuclear Event Scale. The remains of the No.3 continuing to produce electricity into 2000, the accident motivated safety upgrades on all remaining Soviet-designed reactors in the RBMK family, of which eleven continued to power electric grids as of 2013. These events exposed the graphite moderator of the reactor to air, the resulting fire sent week long plumes of highly radioactive fallout into the atmosphere over an extensive geographical area, including Pripyat. The plumes drifted over parts of the western Soviet Union. According to official data, about 60% of the fallout landed in Belarus. The surveying and detection of isolated fallout hotspots outside this zone over the year eventually resulted in 135,000 long-term evacuees in total. Many thousands of these evacuees would have been better off staying home, Russia, Ukraine, and Belarus have been burdened with the continuing and substantial decontamination and monthly compensation costs, of the Chernobyl accident.5 and 6, were eventually cancelled. There was a drop in the prior rate of new startups. The government coverup of the Chernobyl disaster was a catalyst for glasnost, a report by the International Atomic Energy Agency examines the environmental consequences of the accident. Thirty-one deaths are attributed to the accident, all among the reactor staff. An UNSCEAR report places the total confirmed deaths from radiation at 64 as of 2008. 01% of all incident cancers since the accident. Along similar lines, the 2006 TORCH report, commissioned by the European Greens political party, predicts an eventual 30,000 to 60,000 excess cancer deaths in total, greenpeace itself advocates a figure of at least 200,000 or more. Balonov published by the New York Academy of Sciences concludes that the report is of value because it has very little scientific merit while being highly misleading to the lay reader. It characterized the estimate of nearly a million deaths as more in the realm of fiction than science. On 26 April 1986, at 01,23, reactor four suffered a power increase
22.
Mayak
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The Mayak Production Association is one of the biggest nuclear facilities in the Russian Federation, housing plutonium production reactors and a reprocessing plant. The nuclear complex is located 150 km south-east of Ekaterinburg, between the towns of Kasli and Tatysh, and 72 km northwest of Chelyabinsk, the closest city, Ozyorsk, is the central administrative territorial district. As part of the Russian nuclear weapons program, Mayak was formerly known as Chelyabinsk-40 and later as Chelyabinsk-65, in 1957 Mayak was the site of the Kyshtym disaster, one of the worst nuclear accidents in history. During this catastrophe, a poorly maintained storage tank exploded, releasing 50-100 tons of radioactive waste. The resulting radioactive cloud contaminated an expansive territory of more than 750 km2 in the eastern Urals with the consequence of sickness, the Soviet regime kept this accident secret for about thirty years. The event was rated at 6 on the seven-level INES scale, third in severity only to the disasters at Chernobyl in Ukraine. Mayaks nuclear facility plant covers about 90 square kilometers, the site borders Ozyorsk, in which a majority of the staff of Mayak live. Mayak, itself, was not shown on Soviet public maps, the location of the site together with the plant city was chosen to minimize the effects that harmful emissions could potentially have on populated areas. Mayak is surrounded by a ~250 km2 exclusion zone, nearby is the site of the South Urals nuclear power plant. The Mayak plant was built between 1945–48, in a hurry and in total secrecy as part of the Soviet Unions atomic bomb project. Five nuclear reactors were built to make, refine, and machine plutonium for weapons, later the plant came to specialize in reprocessing spent nuclear fuel from nuclear reactors and plutonium from decommissioned weapons. Today the plant makes tritium and radioisotopes, not plutonium, in recent years, proposals that the plant reprocess waste from foreign nuclear reactors have given rise to controversy. Mayak continues to dump radioactive waste directly into the Techa River today. Medium level waste is discharged into the Karachay Lake, the tritium concentration, alone, in the Techa River near the village Muslyumovo exceeds the permissible limit by 30 times. Rosatom, a state-owned nuclear operations corporation, began to resettle residents of Muslyumovo in 2006, however, only half of the residents of the village were moved. People continue to live in the area of the plant, including Ozersk. Residents report no problems with their health and the health of Mayak plant workers, however, these claims lack hard verification, and many who worked at the plant in 1950s and 1960s subsequently died from the effects of radiation. Working conditions at Mayak resulted in severe health hazards and many accidents and this released 740 PBq of fission products, of which 74 PBq drifted off the site, creating a contaminated region of 15, 000-20,000 km2 called the East Urals Radioactive trace
23.
New Zealand
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New Zealand /njuːˈziːlənd/ is an island nation in the southwestern Pacific Ocean. The country geographically comprises two main landmasses—the North Island, or Te Ika-a-Māui, and the South Island, or Te Waipounamu—and around 600 smaller islands. New Zealand is situated some 1,500 kilometres east of Australia across the Tasman Sea and roughly 1,000 kilometres south of the Pacific island areas of New Caledonia, Fiji, because of its remoteness, it was one of the last lands to be settled by humans. During its long period of isolation, New Zealand developed a distinct biodiversity of animal, fungal, the countrys varied topography and its sharp mountain peaks, such as the Southern Alps, owe much to the tectonic uplift of land and volcanic eruptions. New Zealands capital city is Wellington, while its most populous city is Auckland, sometime between 1250 and 1300 CE, Polynesians settled in the islands that later were named New Zealand and developed a distinctive Māori culture. In 1642, Dutch explorer Abel Tasman became the first European to sight New Zealand, in 1840, representatives of Britain and Māori chiefs signed the Treaty of Waitangi, which declared British sovereignty over the islands. In 1841, New Zealand became a colony within the British Empire, today, the majority of New Zealands population of 4.7 million is of European descent, the indigenous Māori are the largest minority, followed by Asians and Pacific Islanders. Reflecting this, New Zealands culture is derived from Māori and early British settlers. The official languages are English, Māori and New Zealand Sign Language, New Zealand is a developed country and ranks highly in international comparisons of national performance, such as health, education, economic freedom and quality of life. Since the 1980s, New Zealand has transformed from an agrarian, Queen Elizabeth II is the countrys head of state and is represented by a governor-general. In addition, New Zealand is organised into 11 regional councils and 67 territorial authorities for local government purposes, the Realm of New Zealand also includes Tokelau, the Cook Islands and Niue, and the Ross Dependency, which is New Zealands territorial claim in Antarctica. New Zealand is a member of the United Nations, Commonwealth of Nations, ANZUS, Organisation for Economic Co-operation and Development, Pacific Islands Forum, and Asia-Pacific Economic Cooperation. Dutch explorer Abel Tasman sighted New Zealand in 1642 and called it Staten Landt, in 1645, Dutch cartographers renamed the land Nova Zeelandia after the Dutch province of Zeeland. British explorer James Cook subsequently anglicised the name to New Zealand, Aotearoa is the current Māori name for New Zealand. It is unknown whether Māori had a name for the country before the arrival of Europeans. Māori had several names for the two main islands, including Te Ika-a-Māui for the North Island and Te Waipounamu or Te Waka o Aoraki for the South Island. Early European maps labelled the islands North, Middle and South, in 1830, maps began to use North and South to distinguish the two largest islands and by 1907, this was the accepted norm. The New Zealand Geographic Board discovered in 2009 that the names of the North Island and South Island had never been formalised and this set the names as North Island or Te Ika-a-Māui, and South Island or Te Waipounamu
24.
Austria
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Austria, officially the Republic of Austria, is a federal republic and a landlocked country of over 8.7 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Hungary and Slovakia to the east, Slovenia and Italy to the south, the territory of Austria covers 83,879 km2. The terrain is mountainous, lying within the Alps, only 32% of the country is below 500 m. The majority of the population speaks local Bavarian dialects of German as their native language, other local official languages are Hungarian, Burgenland Croatian, and Slovene. The origins of modern-day Austria date back to the time of the Habsburg dynasty, from the time of the Reformation, many northern German princes, resenting the authority of the Emperor, used Protestantism as a flag of rebellion. Following Napoleons defeat, Prussia emerged as Austrias chief competitor for rule of a greater Germany, Austrias defeat by Prussia at the Battle of Königgrätz, during the Austro-Prussian War of 1866, cleared the way for Prussia to assert control over the rest of Germany. In 1867, the empire was reformed into Austria-Hungary, Austria was thus the first to go to war in the July Crisis, which would ultimately escalate into World War I. The First Austrian Republic was established in 1919, in 1938 Nazi Germany annexed Austria in the Anschluss. This lasted until the end of World War II in 1945, after which Germany was occupied by the Allies, in 1955, the Austrian State Treaty re-established Austria as a sovereign state, ending the occupation. In the same year, the Austrian Parliament created the Declaration of Neutrality which declared that the Second Austrian Republic would become permanently neutral, today, Austria is a parliamentary representative democracy comprising nine federal states. The capital and largest city, with a population exceeding 1.7 million, is Vienna, other major urban areas of Austria include Graz, Linz, Salzburg and Innsbruck. Austria is one of the richest countries in the world, with a nominal per capita GDP of $43,724, the country has developed a high standard of living and in 2014 was ranked 21st in the world for its Human Development Index. Austria has been a member of the United Nations since 1955, joined the European Union in 1995, Austria also signed the Schengen Agreement in 1995, and adopted the euro currency in 1999. The German name for Austria, Österreich, meant eastern realm in Old High German, and is cognate with the word Ostarrîchi and this word is probably a translation of Medieval Latin Marchia orientalis into a local dialect. Austria was a prefecture of Bavaria created in 976, the word Austria is a Latinisation of the German name and was first recorded in the 12th century. Accordingly, Norig would essentially mean the same as Ostarrîchi and Österreich, the Celtic name was eventually Latinised to Noricum after the Romans conquered the area that encloses most of modern-day Austria, around 15 BC. Noricum later became a Roman province in the mid-first century AD, heers hypothesis is not accepted by linguists. Settled in ancient times, the Central European land that is now Austria was occupied in pre-Roman times by various Celtic tribes, the Celtic kingdom of Noricum was later claimed by the Roman Empire and made a province
25.
Radionuclide
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A radionuclide is an atom that has excess nuclear energy, making it unstable. During those processes, the radionuclide is said to undergo radioactive decay, the unstable nucleus is more stable following the emission, but will sometimes undergo further decay. Radioactive decay is a process at the level of single atoms. However, for a collection of atoms of an element the decay rate. The range of the half-lives of radioactive atoms have no known limits, Radionuclides occur naturally and are artificially produced in nuclear reactors, cyclotrons, particle accelerators or radionuclide generators. There are about 730 radionuclides with half-lives longer than 60 minutes, with the longest half lives are the 32 primordial radionuclides that have survived from the creation of the Solar System. Over 60 further radionuclides are detectable in nature, either as daughters of these, more than 2400 radionuclides have half-lives less than 60 minutes. Most of those are produced artificially, and have very short half-lives. For comparison, there are about 254 stable nuclides, even the lightest element, hydrogen, has a well-known radionuclide, tritium. Elements heavier than lead, and the elements technetium and promethium, unplanned exposure to radionuclides generally has a harmful effect on living organisms including humans, although low levels of exposure occur naturally without harm. However, radionuclides with suitable properties are used in medicine for both diagnosis and treatment. An imaging tracer made with radionuclides is called a radioactive tracer, a pharmaceutical drug made with radionuclides is called a radiopharmaceutical. On Earth, naturally occurring radionuclides fall into three categories, primordial radionuclides, secondary radionuclides, and cosmogenic radionuclides, Radionuclides are produced in stellar nucleosynthesis and supernova explosions along with stable nuclides. Most decay quickly but can still be observed astronomically and can play a part in understanding astronomic processes, primordial radionuclides, such as uranium and thorium, exist in the present time because their half-lives are so long they have not yet completely decayed. It is possible decay may be observed in other nuclides adding to this list of primordial radionuclides, secondary radionuclides are radiogenic isotopes derived from the decay of primordial radionuclides. They have shorter half-lives than primordial radionuclides and they arise in the decay chain of the primordial isotopes thorium-232, uranium-238 and uranium-235. Examples include the natural isotopes of polonium and radium, cosmogenic isotopes, such as carbon-14, are present because they are continually being formed in the atmosphere due to cosmic rays. Many of these radionuclides exist only in trace amounts in nature, secondary radionuclides will occur in proportion to their half-lives, so short-lived ones will be very rare
26.
Nuclear fallout
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It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes, but such dust can also originate from a damaged nuclear plant. Fallout may get entrained with the products of a pyrocumulus cloud and this radioactive dust, usually consisting of fission products mixed with bystanding atoms that are neutron activated by exposure, is a highly dangerous kind of radioactive contamination. An air burst can eventually produce worldwide fallout, a ground burst can produce possibly much more severe, local fallout. These particles may be drawn up into the stratosphere, particularly if the explosive yield exceeds 10 kt. Initially little was known about the dispersion of nuclear fallout on a global scale, the AEC assumed that fallout would be dispersed evenly across the globe by atmospheric winds and gradually settle to the Earths surface after weeks, months, and even years as worldwide fallout. This hazard is less pertinent than local fallout, which is of much greater immediate operational concern, in a land or water surface burst, heat vaporizes large amounts of earth or water, which is drawn up into the radioactive cloud. This material becomes radioactive when it condenses with fission products and other radiocontaminants that have become neutron-activated, the table below summarizes the abilities of common isotopes to form fallout. Some radiation taints large amounts of land and drinking water causing formal mutations throughout animal and human life. The larger particles spill out of the stem and cascade down the outside of the fireball in a downdraft even as the cloud rises, more than half the total bomb debris lands on the ground within about 24 hours as local fallout. Chemical properties of the elements in the control the rate at which they are deposited on the ground. Severe local fallout contamination can extend far beyond the blast and thermal effects, the ground track of fallout from an explosion depends on the weather from the time of detonation onwards. In stronger winds, fallout travels faster but takes the time to descend, so although it covers a larger path. Thus, the width of the pattern for any given dose rate is reduced where the downwind distance is increased by higher winds. The total amount of activity deposited up to any time is the same irrespective of the wind pattern. But thunderstorms can bring down activity as rain more rapidly than dry fallout, particularly if the cloud is low enough to be below, or mixed with. There are two considerations for the location of an explosion, height and surface composition. A nuclear weapon detonated in the air, called an air burst, in case of water surface bursts, the particles tend to be rather lighter and smaller, producing less local fallout but extending over a greater area. The particles contain mostly sea salts with some water, these can have a cloud seeding effect causing local rainout and areas of high local fallout
27.
Nuclear explosion
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A nuclear explosion is an explosion that occurs as a result of the rapid release of energy from a high-speed nuclear reaction. Atmospheric nuclear explosions are associated with clouds, although mushroom clouds can occur with large chemical explosions. It is possible to have an air-burst nuclear explosion without these clouds, nuclear explosions produce radiation and radioactive debris. Any nuclear explosion would have wide-ranging, long-term, catastrophic effects, radioactive contamination would cause genetic mutations and cancer across many generations. The first nuclear explosion occurred on July 16,1945 at 5,50 am on the Trinity Test Site near Alamogordo, New Mexico in the United States, the event involved the full-scale testing of an implosion-type fission atomic bomb. In a memorandum to the U. S. Secretary of War, in the years following World War II, eight countries have conducted nuclear tests with 2475 devices fired in 2120 tests. In 1963, the United States, Soviet Union, and United Kingdom signed the Limited Test Ban Treaty, pledging to refrain from testing nuclear weapons in the atmosphere, underwater, or in outer space. Many other non-nuclear nations acceded to the Treaty following its entry into force, however, power generation, see PACER Peaceful nuclear explosions Only two nuclear weapons have been deployed in combat—both by the United States against Japan in World War II. The second event occurred three days later when the United States Army Air Forces dropped a plutonium device, code-named Fat Man. It killed 39,000 people, including 27,778 Japanese munitions employees,2,000 Korean slave laborers, in total, around 119,000 people were killed in these bombings. Since the Trinity test and excluding the use of nuclear weapons, mankind has detonated roughly 1,700 nuclear explosions. Of these, six were peaceful nuclear explosions, nuclear tests are experiments carried out to determine the effectiveness, yield and explosive capability of nuclear weapons. Throughout the 20th century, most nations that have developed nuclear weapons had a staged test of them, testing nuclear weapons can yield information about how the weapons work, as well as how the weapons behave under various conditions and how structures behave when subjected to a nuclear explosion. The devastating impact of the explosion does not stop after the initial blast, a cloud of nuclear radiation travels from the epicenter of the explosion, causing an impact to life forms even after the heat waves have ceased. Any nuclear explosion would have wide-ranging, long-term, catastrophic effects, radioactive contamination would cause genetic mutations and cancer across many generations. Lists of nuclear disasters and radioactive incidents Soviet nuclear well collapses Visual depictions of explosions in fiction
28.
Xenon
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Xenon is a chemical element with symbol Xe and atomic number 54. It is a colorless, dense, odorless gas found in the Earths atmosphere in trace amounts. Although generally unreactive, xenon can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, Xenon is used in flash lamps and arc lamps, and as a general anesthetic. The first excimer laser used a xenon dimer molecule as the lasing medium. Xenon is used to search for hypothetical weakly interacting massive particles, naturally occurring xenon consists of eight stable isotopes. More than 40 unstable xenon isotopes undergo radioactive decay, and the ratios of xenon are an important tool for studying the early history of the Solar System. Radioactive xenon-135 is produced by beta decay from iodine-135, and is the most significant neutron absorber in nuclear reactors, Xenon was discovered in England by the Scottish chemist William Ramsay and English chemist Morris Travers in September 1898, shortly after their discovery of the elements krypton and neon. They found xenon in the left over from evaporating components of liquid air. Ramsay suggested the name xenon for this gas from the Greek word ξένον, neuter singular form of ξένος, meaning foreign, strange, in 1902, Ramsay estimated the proportion of xenon in the Earths atmosphere to be one part in 20 million. During the 1930s, American engineer Harold Edgerton began exploring strobe light technology for high speed photography and this led him to the invention of the xenon flash lamp in which light is generated by passing brief electric current through a tube filled with xenon gas. In 1934, Edgerton was able to generate flashes as brief as one microsecond with this method, in 1939, American physician Albert R. Behnke Jr. began exploring the causes of drunkenness in deep-sea divers. He tested the effects of varying the breathing mixtures on his subjects, from his results, he deduced that xenon gas could serve as an anesthetic. Xenon was first used as an anesthetic in 1951 by American anesthesiologist Stuart C. Cullen, who used it with two patients. Xenon and the noble gases were for a long time considered to be completely chemically inert. Since O2 and xenon have almost the same first ionization potential, on March 23,1962, he mixed the two gases and produced the first known compound of a noble gas, xenon hexafluoroplatinate. Bartlett thought its composition to be Xe+−, but later revealed that it was probably a mixture of various xenon-containing salts. By 1971, more than 80 xenon compounds were known, in November 1989, IBM scientists demonstrated a technology capable of manipulating individual atoms
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Nuclear reprocessing
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Nuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel. Reprocessing serves multiple purposes, whose importance has changed over time. Originally, reprocessing was used solely to extract plutonium for producing nuclear weapons, with the commercialization of nuclear power, the reprocessed plutonium was recycled back into MOX nuclear fuel for thermal reactors. The reprocessed uranium, which constitutes the bulk of the spent fuel material, can in principle also be re-used as fuel, finally, a breeder reactor is not restricted to using recycled plutonium and uranium. It can employ all the actinides, closing the fuel cycle. In the United States, the Obama administration stepped back from President Bushs plans for commercial-scale reprocessing, Nuclear fuel reprocessing is performed routinely in Europe, Russia and Japan. The potentially useful components dealt with in nuclear reprocessing comprise specific actinides, the lighter elements components include fission products, activation products, and cladding. The first large-scale nuclear reactors were built during World War II and these reactors were designed for the production of plutonium for use in nuclear weapons. The only reprocessing required, therefore, was the extraction of the plutonium from the spent natural uranium fuel, in 1943, several methods were proposed for separating the relatively small quantity of plutonium from the uranium and fission products. ORNL produced the first macroscopic quantities of separated plutonium with these processes, the bismuth phosphate process was first operated on a large scale at the Hanford Site, in the later part of 1944. It was successful for plutonium separation in the situation existing then, but it had a significant weakness. The first successful solvent extraction process for the recovery of uranium and plutonium was developed at ORNL in 1949. The PUREX process is the current method of extraction, on 7 April 1977, President Jimmy Carter banned the reprocessing of commercial reactor spent nuclear fuel. After that, only countries that already had large investments in reprocessing infrastructure continued to reprocess spent nuclear fuel, President Reagan lifted the ban in 1981, but did not provide the substantial subsidy that would have been necessary to start up commercial reprocessing. Site preparation at the Savannah River Site began in October 2005, in 2011 the New York Times reported.11 years after the government awarded a construction contract, the cost of the project has soared to nearly $5 billion. The vast concrete and steel structure is a hulk. TVA said in April 2011 that it would delay a decision until it could see how MOX fuel performed in the accident at Fukushima Daiichi. PUREX, the current standard method, is an acronym standing for Plutonium and Uranium Recovery by EXtraction, the PUREX process is a liquid-liquid extraction method used to reprocess spent nuclear fuel, to extract uranium and plutonium, independent of each other, from the fission products
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Actinides in the environment
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Actinides in the environment refer to the sources, environmental behaviour and effects of actinides in Earths environment. Environmental radioactivity is not limited solely to actinides, non-actinides such as radon, inhaled actinide compounds, however, will be more damaging as they remain in the lungs and irradiate the lung tissue. Ingested Low-fired oxides and soluble salts such as nitrate can be absorbed into the blood stream, if they are inhaled then it is possible for the solid to dissolve and leave the lungs. Hence, the dose to the lungs will be lower for the soluble form, in India, a large amount of thorium ore can be found in the form of monazite in placer deposits of the Western and Eastern coastal dune sands, particularly in the Tamil Nadu coastal areas. The residents of area are exposed to a naturally occurring radiation dose ten times higher than the worldwide average. Thorium is found at low levels in most rocks and soils, soil commonly contains an average of around 6 parts per million of thorium. Thorium occurs in minerals, the most common being the rare earth-thorium-phosphate mineral, monazite. There are substantial deposits in several countries, other isotopes of thorium occur in the thorium and uranium decay chains. Most of these are short-lived and hence much more radioactive than 232Th, thorium has been linked to liver cancer. In the past thoria was used as a contrast agent for medical X-ray radiography and it was sold under the name Thorotrast. Uranium is a metal which is widely found. It is present in almost all soils and it is more plentiful than antimony, beryllium, cadmium, gold, mercury, silver, or tungsten, and is about as abundant as arsenic or molybdenum. Significant concentrations of uranium occur in some such as phosphate rock deposits, and minerals such as lignite. Seawater contains about 3.3 parts per billion of uranium by weight as uranium forms soluble carbonate complexes, the extraction of uranium from seawater has been considered as a means of obtaining the element. Because of the low specific activity of uranium the chemical effects of it upon living things can often outweigh the effects of its radioactivity. Additional uranium has been added to the environment in some locations as a result of the fuel cycle. Like plutonium, neptunium has an affinity for soil. 237Np has a halflife of 2, plutonium in the environment has several sources
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Nuclear decommissioning
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Nuclear decommissioning is the process whereby a nuclear facility is dismantled to the point that it no longer requires measures for radiation protection. Decommissioning is an administrative and technical process and it includes clean-up of radioactive materials and progressive demolition of the facility. Once a facility is decommissioned, no radiological danger should persist. The costs of decommissioning are spread over the lifetime of a facility, after a facility has been completely decommissioned, it is released from regulatory control and the plant licensee is no longer responsible for its nuclear safety. Decommissioning may proceed all the way to greenfield status, Decommissioning may proceed all the way to greenfield status. Once a facility is decommissioned no radioactive danger persists and it can be released from regulatory control, final dismantling or decontamination activities begin within a few months or years, and depending on the facility, it could take five years or more. Following removal from regulatory control, the site available for re-use. Safe Enclosure, This option postpones the final removal of controls for a longer period, the facility is placed into a safe storage configuration until the eventual dismantling and decontamination activities occur. Entombment/ENTOMB, This option entails placing the facility into a condition that will allow the radioactive material to remain on-site indefinitely. In the US, the NRC recommends that the costs of decommissioning should be spread over the lifetime of a facility, repository delay seems to be effective in reducing NPP decommissioning costs. The total cost to decommission the nuclear industry in the World was estimated around 1 US$ Trillion. A wide range of facilities have been decommissioned so far. The number of decommissioned nuclear reactors out of the List of nuclear reactors is small, as of 2016,150 nuclear reactors were shut-off, in several early and intermediate stages, but only 17 have been taken to fully greenfield status. Some of these sites still host spent nuclear fuel in the form of dry casks embedded in concrete filled steel drums, several nuclear engineering and building demolition companies specialize in nuclear decommissioning, which has become a profitable business. More recently, construction and demolition companies in the UK have also begun to develop nuclear decommissioning services, due to the radioactivity in the reactor structure, decommissioning takes place in stages. Plans for decommissioning reactors have a frame of decades. The long time frame makes reliable cost estimates difficult and cost overruns are common even for quick projects. Most nuclear plants currently perating in 2017, in the United States were designed for a life of about 30–40 years and are licensed to operate for 40 years by the US Nuclear Regulatory Commission, the average age of these reactors is 32 years
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Glovebox
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A glovebox is a sealed container that is designed to allow one to manipulate objects where a separate atmosphere is desired. Built into the sides of the glovebox are gloves arranged in such a way that the user can place their hands into the gloves, part or all of the box is usually transparent to allow the user to see what is being manipulated. It is also possible to use a glovebox for manipulation of items in a vacuum chamber, the gas in a glovebox is pumped through a series of treatment devices which remove solvents, water and oxygen from the gas. It is common to use molecular sieves to remove water by adsorbing it in the molecular sieves pores, such a box is often used by organometallic chemists to transfer dry solids from one container to another. An alternative to using a glovebox for air sensitive work is to employ Schlenk methods using a Schlenk line, one disadvantage of working in a glovebox is that organic solvents will attack the plastic seals. As a result, the box will start to leak and water, another disadvantage of a glovebox is that oxygen and water can diffuse through the plastic gloves. Inert atmosphere gloveboxes are typically kept at a higher pressure than the surrounding air, other materials used in the gloveboxes included acrylic viewing windows and Benelex shielding composed of wood fiber and plastic which shielded against neutron radiation. Manipulation of the gloves was onerous work. Some gloveboxes for radioactive work are under inert conditions, for instance, the argon box is fitted with a gas treatment system to keep the gas very pure to enable electrochemical experiments in molten salts. Gloveboxes are also used in the biological sciences when dealing with anaerobes or high-biosafety level pathogens, gloveboxes used for hazardous materials are generally maintained at a lower pressure than the surrounding atmosphere, so that microscopic leaks result in air intake rather than hazard outflow. Gloveboxes used for hazardous materials generally incorporate HEPA filters into the exhaust, desiccators are used for storing chemicals which are moisture-sensitive, but do not react quickly or violently with water. Fume hoods are used for material handling where less operator protection. Hot cells often use remote manipulators to provide radiological containment where more operator protection is required, Schlenk lines are used for manipulating oxygen- and moisture-sensitive chemicals. American Glovebox Society Hans-Jürgen Bässler und Frank Lehmann, Containment Technology, Progress in the Pharmaceutical and Food Processing Industry
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Environmental radioactivity
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Environmental radioactivity is produced by radioactive materials in the human environment. g. Tritium, result from natural processes and human activities. The concentration and location of natural isotopes, particularly uranium-238. Radioactivity is present everywhere, and has been since the formation of the earth, according to the IAEA, soil typically contains the following four natural radioisotopes, 40K, 226Ra, 238U, and 232Th. In one kilogram of soil, the amounts to an average 370 Bq of radiation, with a typical range of 100–700 Bq. Some soils may vary greatly from these norms, a recent report on the Sava river in Serbia suggests that many of the river silts contain about 100 Bq kg−1 of natural radioisotopes. According to the United Nations the normal concentration of uranium in soil ranges between 300 μg kg−1 and 11.7 mg kg−1, synthetic radioisotopes also can be detected in silt. Some relationship between distance and activity can be seen in their data, when fitted to an exponential curve, normal licensed releases which occur during the regular operation of a plant or process handling man-made radioactive materials. For instance the release of 99Tc from a nuclear medicine department of a hospital which occurs when a given a Tc imaging agent expels the agent. Releases of man-made radioactive materials which occur during an industrial or research accident, releases which occur as a result of military activity. For example, a weapons test. Releases which occur as a result of a crime, for example, the Goiânia accident where thieves, unaware of its radioactive content, stole some medical equipment and as a result a number of people were exposed to radiation. Releases of naturally occurring radioactive materials as a result of mining etc, for example, the release of the trace quantities of uranium and thorium in coal, when it is burned in power stations. Just because a radioisotope lands on the surface of the soil, after release into the environment, radioactive materials can reach humans in a range of different routes, and the chemistry of the element usually dictates the most likely route. Using milk as an example, if the cow has an intake of 1000 Bq of the preceding isotopes then the milk will have the following activities. 90Sr,2 Bq dm−3 137Cs,5 Bq dm−3 239Pu,0.001 Bq dm−3 241Am,0, the distribution coefficient Kd is the ratio of the soils radioactivity to that of the soil water. If the radioactivity is tightly bonded to by the minerals in the then less radioactivity can be absorbed by crops. Cs-137 Kd =1000 Pu-239 Kd =10000 to 100000 Sr-90 Kd =80 to 150 I-131 Kd =0.007 to 50 One dramatic source of radioactivity is a nuclear weapons test
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Uranium
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Uranium is a chemical element with symbol U and atomic number 92. It is a metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons, Uranium is weakly radioactive because all its isotopes are unstable. The most common isotopes in natural uranium are uranium-238 and uranium-235, Uranium has the highest atomic weight of the primordially occurring elements. Its density is about 70% higher than that of lead, and it occurs naturally in low concentrations of a few parts per million in soil, rock and water, and is commercially extracted from uranium-bearing minerals such as uraninite. In nature, uranium is found as uranium-238, uranium-235, Uranium decays slowly by emitting an alpha particle. The half-life of uranium-238 is about 4.47 billion years, many contemporary uses of uranium exploit its unique nuclear properties. Uranium-235 is the naturally occurring fissile isotope, which makes it widely used in nuclear power plants. However, because of the amounts found in nature, uranium needs to undergo enrichment so that enough uranium-235 is present. Uranium-238 is fissionable by fast neutrons, and is fertile, meaning it can be transmuted to fissile plutonium-239 in a nuclear reactor, another fissile isotope, uranium-233, can be produced from natural thorium and is also important in nuclear technology. In sufficient concentration, these maintain a sustained nuclear chain reaction. This generates the heat in nuclear reactors, and produces the fissile material for nuclear weapons. Depleted uranium is used in kinetic energy penetrators and armor plating, Uranium is used as a colorant in uranium glass, producing lemon yellow to green colors. Uranium glass fluoresces green in ultraviolet light and it was also used for tinting and shading in early photography. The 1789 discovery of uranium in the mineral pitchblende is credited to Martin Heinrich Klaproth, eugène-Melchior Péligot was the first person to isolate the metal and its radioactive properties were discovered in 1896 by Henri Becquerel. An ensuing arms race during the Cold War between the United States and the Soviet Union produced tens of thousands of weapons that used uranium metal. The security of those weapons and their fissile material following the breakup of the Soviet Union in 1991 is a concern for public health. When refined, uranium is a white, weakly radioactive metal
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Thorium
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Thorium is a chemical element with symbol Th and atomic number 90. A radioactive actinide metal, thorium is one of only two significantly radioactive elements that occur naturally in large quantities as a primordial element. It was discovered in 1829 by the Norwegian amateur mineralogist Morten Thrane Esmark and identified by the Swedish chemist Jöns Jacob Berzelius, who named it after Thor, a thorium atom has 90 protons and therefore 90 electrons, of which four are valence electrons. Thorium metal is silvery and tarnishes black when exposed to air, Thorium is weakly radioactive, all of its known isotopes are unstable. Thorium-232, which has 142 neutrons, is the most stable isotope of thorium and accounts for all natural thorium. Thorium is estimated to be three to four times more abundant than uranium in the Earths crust, and is chiefly refined from monazite sands as a by-product of extracting rare earth metals. Thorium was once used as the light source in gas mantles and as an alloying material. Thorium is still used as an alloying element in TIG welding electrodes. Thorium is predicted to be able to replace uranium as fuel in nuclear reactors. Thorium is a soft, paramagnetic, bright silvery radioactive actinide metal, in the periodic table, it is located to the right of the actinide actinium, to the left of the actinide protactinium, and below the lanthanide cerium. Pure thorium is very ductile and, as normal for metals, can be cold-rolled, swaged, at room temperature, thorium metal has a face-centred cubic crystal structure, additionally, it has two other forms at exotic conditions, one at high temperature and one at high pressure. The properties of thorium vary widely depending on the amount of impurities in the sample, the purest thorium specimens usually contain about a tenth of a percent of the dioxide. These values lie intermediate between those of its neighbours actinium and protactinium, showing the continuity of trends across the early actinides, thoriums melting point of 1750 °C is above both that of actinium and that of protactinium. After thorium, there is a new smooth trend downward in the points of the early actinides from thorium to plutonium where the number of f electrons increases from about 0. Thorium has a modulus of 54 GPa, comparable to those of tin. The hardness of thorium is similar to that of steel, so heated pure thorium can be rolled in sheets. Nevertheless, while thorium is nearly half as dense as uranium and plutonium, Thorium becomes superconductive below 1.4 K. Thorium can also form alloys with many other metals. With chromium and uranium, it forms eutectic mixtures, and thorium is completely miscible in both solid and liquid states with its lighter congener cerium, as such, 232Th still occurs naturally today, four-fifths of the thorium present at Earths formation has survived to the present
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Decay product
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In nuclear physics, a decay product is the remaining nuclide left over from radioactive decay. Radioactive decay often proceeds via a sequence of steps, 234Th is the daughter of the parent 238U. 234mPa is the granddaughter of 238U and these might also be referred to as the daughter products of 238U. Decay products are important in understanding radioactive decay and the management of radioactive waste, for elements above lead in atomic number, the decay chain typically ends with an isotope of thallium or lead. In many cases members of the chain are far more radioactive than the original nuclide. Thus, although uranium is not dangerously radioactive when pure, some pieces of naturally occurring pitchblende are quite dangerous owing to their radium content, similarly, thorium gas mantles are very slightly radioactive when new, but become far more radioactive after only a few months of storage. Although it cannot be predicted whether any given atom of a substance will decay at any given time. Because of this, decay products are important to scientists in many fields who need to know the quantity or type of the parent product, such studies are done to measure pollution levels and for other matters
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Potassium-40
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Potassium-40 is a radioactive isotope of potassium which has a very long half-life of 1. 251×109 years. It makes up 0. 012% of the amount of potassium found in nature. Potassium-40 is an example of an isotope that undergoes all three types of beta decay. About 89. 28% of the time, it decays to calcium-40 with emission of a particle with a maximum energy of 1.33 MeV. About 10. 72% of the time it decays to argon-40 by electron capture, with the emission of a 1.460 MeV gamma ray, the radioactive decay of this particular isotope explains the large abundance of argon in the earths atmosphere. Very rarely it will decay to 40Ar by emitting a positron, potassium-40 is especially important in potassium–argon dating. Argon is a gas that does not ordinarily combine with other elements, so, when a mineral forms – whether from molten rock, or from substances dissolved in water – it will be initially argon-free, even if there is some argon in the liquid. However, if the mineral contains any potassium, then decay of the 40K isotope present will create fresh argon-40 that will remain locked up in the mineral. Since the rate at which this occurs is known, it is possible to determine the elapsed time since the mineral formed by measuring the ratio of 40K. It follows that most of the terrestrial argon derives from potassium-40 that decayed into argon-40, the radioactive decay of 40K in the Earths mantle ranks third, after 232Th and 238U, as the source of radiogenic heat. The core also likely contains radiogenic sources, although how much is uncertain and it has been proposed that significant core radioactivity may be caused by high levels of U, Th, and K. 40K is the largest source of natural radioactivity in animals including humans
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Primordial nuclide
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In geochemistry and geonuclear physics, primordial nuclides, also known as primordial isotopes, are nuclides found on Earth that have existed in their current form since before Earth was formed. They are the stable nuclides plus the long-lived fraction of radionuclides surviving in the solar nebula through planet accretion until the present. Only 286 such nuclides are known, all of the known 254 stable nuclides occur as primordial nuclides, plus another 32 nuclides that have half-lives long enough to have survived from the formation of the Earth. These 32 primordial radionuclides represent isotopes of 27 separate elements, cadmium, tellurium, neodymium, samarium and uranium each have two primordial radioisotopes. Because the age of the Earth is 4. 58×109 years and these are the 4 nuclides with half-lives comparable to, or less than, the estimated age of the universe. For a complete list of the 32 known primordial radionuclides, including the next 28 with half-lives much longer than the age of the universe, the next longest-living nuclide after the end of the list given in the table is 244Pu, with a half-life of 8. 08×107 years. It has been reported to exist in nature as a primordial nuclide, likewise, the second-longest-lived non-primordial 146Sm, was once reported as primordial, but this could not be replicated. Taking into account that all these nuclides must exist since at least 4. 6×109 years, meaning survive 57 half-lives, there exist many extremely long-lived nuclides whose half-lives are still unknown. Nevertheless, the number of nuclides with half-lives so long that they cannot be measured with present instruments—and are considered from this viewpoint to be stable nuclides—is limited, because primordial chemical elements often consist of more than one primordial isotope, there are only 84 distinct primordial chemical elements. Of these,80 have at least one stable isotope. Some unstable isotopes which occur naturally are not primordial, as they must be constantly regenerated and this occurs by cosmic radiation, or by such processes as geonuclear transmutation. Other examples of naturally occurring but non-primordial nuclides are radon, polonium, and radium. A similar radiogenic series is derived from the radioactive primordial nuclide thorium-232. All of such nuclides have shorter half-lives than their parent radioactive primordial nuclides, there are about 51 nuclides which are radioactive and exist naturally on Earth but are not primordial. There are 254 stable primordial nuclides and 32 radioactive primordial nuclides, bismuths half-life is so long that it is often classed with the 80 primordial stable elements instead, since its radioactivity is not a cause for serious concern. The numbers of elements are smaller, because many primordial elements are represented by more than one primordial nuclide, see chemical element for more information. As noted, these number about 254, for a list, see the article list of stable isotopes. For a complete list noting which of the stable 254 nuclides may be in some respect unstable, see list of nuclides and stable isotope
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Carbon-14
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Carbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby, Carbon-14 was discovered on 27 February 1940, by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley, California. Its existence had been suggested by Franz Kurie in 1934, carbon-12 and carbon-13 are both stable, while the half-life of carbon-14 is 5, 730±40 years. Carbon-14 decays into nitrogen-14 through beta decay, a gram of carbon containing 1 atom of carbon-14 per 1012 atoms will emit 0.40 beta particles per second. The primary natural source of carbon-14 on Earth is cosmic ray action on nitrogen in the atmosphere, however, open-air nuclear testing between 1955–1980 contributed to this pool. The different isotopes of carbon do not differ appreciably in their chemical properties, the emitted beta particles have a maximum energy of 156 keV, while their weighted mean energy is 49 keV. These are relatively low energies, the distance traveled is estimated to be 22 cm in air and 0.27 mm in body tissue. The fraction of the radiation transmitted through the dead layer is estimated to be 0.11. Liquid scintillation counting is the preferred method, the G-M counting efficiency is estimated to be 3%. The half-distance layer in water is 0.05 mm. Radiocarbon dating is a dating method that uses to determine the age of carbonaceous materials up to about 60,000 years old. The technique was developed by Willard Libby and his colleagues in 1949 during his tenure as a professor at the University of Chicago, in 1960, Libby was awarded the Nobel Prize in chemistry for this work. One of the frequent uses of the technique is to date organic remains from archaeological sites, plants fix atmospheric carbon during photosynthesis, so the level of 14C in plants and animals when they die approximately equals the level of 14C in the atmosphere at that time. However, it decreases thereafter from radioactive decay, allowing the date of death or fixation to be estimated. A calculation or a comparison of carbon-14 levels in a sample, with tree ring or cave-deposit carbon-14 levels of a known age. Carbon-14 is produced in the layers of the troposphere and the stratosphere by thermal neutrons absorbed by nitrogen atoms. When cosmic rays enter the atmosphere, they undergo various transformations, the resulting neutrons participate in the following reaction, n +14 7N →14 6C + p The highest rate of carbon-14 production takes place at altitudes of 9 to 15 km and at high geomagnetic latitudes. Production rates vary because of changes to the cosmic ray flux caused by the heliospheric modulation, the latter can create significant variations in 14C production rates, although the changes of the carbon cycle can make these effects difficult to tease out. Another extraordinarily large 14C increase has been associated with the 5480 BC event
40.
Cosmic ray
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Cosmic rays are high-energy radiation, mainly originating outside the Solar System. Upon impact with the Earths atmosphere, cosmic rays can produce showers of particles that sometimes reach the surface. Composed primarily of protons and atomic nuclei, they are of mysterious origin. Data from the Fermi space telescope have been interpreted as evidence that a significant fraction of cosmic rays originate from the supernovae explosions of stars. Active galactic nuclei probably also produce cosmic rays, the term ray is a historical accident, as cosmic rays were at first, and wrongly, thought to be mostly electromagnetic radiation. In current usage, the cosmic ray almost exclusively refers to massive particles. Massive particles – those that have rest mass – can gain additional, kinetic, mass-energy when they are moving, through this process, some particles acquire tremendously high mass-energies. These are significantly higher than the energy of even the highest-energy photons detected to date. The energy of the massless photon depends solely on frequency, not speed, at the higher end of the energy spectrum, relativistic kinetic energy is the main source of the mass-energy of cosmic rays. Hence, the highest-energy detected fermionic cosmic ray was around 3×106 times more energetic than the highest-energy detected cosmic photons, of primary cosmic rays, which originate outside of Earths atmosphere, about 99% are the nuclei of well-known atoms, and about 1% are solitary electrons. Of the nuclei, about 90% are simple protons, i. e. hydrogen nuclei, 9% are alpha particles, identical to helium nuclei, a very small fraction are stable particles of antimatter, such as positrons or antiprotons. The precise nature of this fraction is an area of active research. An active search from Earth orbit for anti-alpha particles has failed to detect them, one can show that such enormous energies might be achieved by means of the Centrifugal mechanism of acceleration in Active galactic nuclei. At 50 J, the highest-energy ultra-high-energy cosmic rays have energies comparable to the energy of a 90-kilometre-per-hour baseball. As a result of discoveries, there has been interest in investigating cosmic rays of even greater energies. Most cosmic rays, however, do not have such extreme energies, however, his paper published in Physikalische Zeitschrift was not widely accepted. In 1911 Domenico Pacini observed simultaneous variations of the rate of ionization over a lake, over the sea, Pacini concluded from the decrease of radioactivity underwater that a certain part of the ionization must be due to sources other than the radioactivity of the Earth. In 1912, Victor Hess carried three enhanced-accuracy Wulf electrometers to an altitude of 5300 meters in a balloon flight
41.
Radon
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Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas and it occurs naturally as an intermediate step in the normal radioactive decay chains through which thorium and uranium slowly decay into lead, radon, itself, is a decay product of radium. Its most stable isotope, 222Rn, has a half-life of 3.8 days, unlike all the other intermediate elements in the aforementioned decay chains, radon is, under normal conditions, gaseous and easily inhaled. Radon gas is a health hazard and it is often the single largest contributor to an individuals background radiation dose, but due to local differences in geology, the level of the radon-gas hazard differs from location to location. Despite its short lifetime, radon gas from natural sources can accumulate in buildings, especially, due to its density, in low areas such as basements. Radon can also occur in ground water - for example, in spring waters. Epidemiological studies have shown a link between breathing high concentrations of radon and incidence of lung cancer. Radon is a contaminant that affects indoor air quality worldwide, about 2,900 of these deaths occur among people who have never smoked. While radon is the second most frequent cause of cancer, it is the number one cause among non-smokers. As radon itself decays, it produces other radioactive elements called radon progeny or decay products, unlike the gaseous radon itself, radon daughters are solids and stick to surfaces, such as dust particles in the air. If such contaminated dust is inhaled, these particles can cause lung cancer. Radon is a colorless, odorless, and tasteless gas and therefore not detectable by human senses alone. At standard temperature and pressure, radon forms a gas with a density of 9.73 kg/m3. Radon is one of the densest gases at room temperature and is the densest of the noble gases, upon condensation, radon glows because of the intense radiation it produces. Radon is sparingly soluble in water, but more soluble than lighter noble gases, Radon is appreciably more soluble in organic liquids than in water. Being a noble gas, radon is chemically not very reactive, however, the 3. 8-day half-life of radon-222 makes it useful in physical sciences as a natural tracer. Because radon is a gas at standard conditions, unlike its parents, Radon is a member of the zero-valence elements that are called noble gases. It is inert to most common chemical reactions, such as combustion and this produces a stable, minimum energy configuration in which the outer electrons are tightly bound
42.
Background radiation
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Background radiation is the ionizing radiation present in the environment. Background radiation originates from a variety of sources, both natural and artificial, sources include cosmic radiation, naturally occurring radioactive materials such as radon, and fallout from nuclear weapons testing and nuclear accidents. For example, in considering radiation safety, background radiation is defined by the International Atomic Energy Agency as Dose or dose rate attributable to all other than the one specified. So a distinction is made between sources of dose which are incidentally in a location, which are defined here as being background, and this is important where radiation measurements are taken of a specified radiation source, and the incidental background may affect this measurement. An example would be detection of radioactive contamination in a gamma ray background, background radiation varies with location and time, and the following table gives examples, Radioactive material is found throughout nature. Detectable amounts occur naturally in soil, rocks, water, air, in addition to this internal exposure, humans also receive external exposure from radioactive materials that remain outside the body and from cosmic radiation from space. The worldwide average natural dose to humans is about 2.4 millisievert per year and this is four times the worldwide average artificial radiation exposure, which in 2008 amounted to about 0.6 mSv per year. In some rich countries, like the US and Japan, artificial exposure is, on average, greater than the natural exposure, due to greater access to medical imaging. In Europe, average natural background exposure by country ranges from under 2 mSv annually in the United Kingdom to more than 7 mSv annually for some groups of people in Finland. The International Atomic Energy Agency states, Exposure to radiation from natural sources is a feature of everyday life in both working and public environments. These situations have become the focus of attention by the Agency in recent years. The biggest source of background radiation is airborne radon, a radioactive gas that emanates from the ground. Radon and its isotopes, parent radionuclides, and decay products all contribute to an average inhaled dose of 1.26 mSv/a. Radon is unevenly distributed and varies with weather, such that higher doses apply to many areas of the world. Concentrations over 500 times the average have been found inside buildings in Scandinavia, the United States, Iran. Radon is a product of uranium, which is relatively common in the Earths crust. Radon seeps out of these ores into the atmosphere or into water or infiltrates into buildings. It can be inhaled into the lungs, along with its decay products, although radon is naturally occurring, exposure can be enhanced or diminished by human activity, notably house construction
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Survey meter
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The hand-held survey meter is probably the most familiar radiation measuring device to society owing to its wide and highly visible use. The instruments are designed to be hand-held, are battery powered, other features include an easily readable display, in counts or radiation dose, and an audible indication of the count rate. This is usually the “click” associated with the Geiger type instrument, for dual channel detectors such as the scintillation detector it is normal to generate different sounds for alpha and beta. This gives the operator rapid feedback on both the level of radiation and the type of particle being detected and these features allow the user to concentrate on manipulation of the meter whilst having auditory feedback of the rate of radiation detected. Meters can be integrated with probe and processing electronics in one housing to allow single-handed use, or have separate detector probe and electronics housings. This latter is preferred for checking of convoluted surfaces for radioactive contamination due to the ease of manipulating the probe, the readout for alpha and beta radiation is normally in counts, whilst that for gamma and X-ray is normally in a reading of radiation dose. The SI unit for this latter is the sievert, there is no simple universal conversion from count rate to dose rate, as it depends on the particle type, its energy, and the characteristic of the sensor. Count rate therefore tends to be used as a value which has been calculated for an application for use as a comparator or against an absolute alarm threshold. A dose instrument may be used if a dose reading is required. To help with some instruments have both dose and count rate displays. Battery operated meters usually have a battery level check and this provided a real-time dynamic indication of the radiation rate, and the principle has found widespread use in Health Physics and as radiation Survey meter. An instrument which totalises the events detected over a period is known as a scaler. This colloquial name stems from the days of automatic counting. This technique was developed by C E Wynn-Williams at The Cavendish Laboratory, the original counters used the Eccles-Jordan divider circuit, today known as a flip flop. This was before the era of electronic indicators, which started with the introduction of the Dekatron tube in the 1950s, the UK Health and Safety Executive has issued a guidance note on the correct portable instrument for the application concerned. This covers all radiation instrument technologies, the user must have an awareness of the types of radiation to be encountered so that the correct instrument is used. A further complication is the presence of mixed radiation fields where more than one form of radiation is present. Many instruments are sensitive to more than one type of radiation, alpha and beta, or beta and gamma, for instance, the operator can now deduce that both alpha and beta is present
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Airborne particulate radioactivity monitoring
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Continuous particulate air monitors have been used for years in nuclear facilities to assess airborne particulate radioactivity. In more recent times they may also be used to people in their homes for the presence of manmade radioactivity. These monitors can be used to trigger alarms, indicating to personnel that they should evacuate an area and this article will focus on CPAM use in nuclear power plants, as opposed to other nuclear fuel-cycle facilities, or laboratories, or public-safety applications. CPAMs use a pump to draw air through a medium to collect airborne particulate matter that carries very small particles of radioactive material. The particulate radioactive material might be natural, e. g. radon decay products, or manmade, usually fission or activation products, there are also gas monitors which pass the air through a sample chamber volume which is viewed continuously by a radiation detector. These gas monitors are often placed downstream of a CPAM so that any matter in the sampled air is collected by the CPAM. In monitoring, the region of deposition of material onto the filter medium is continuously viewed by a radiation detector. On the other hand, monitoring with CPAMs provides nearly real-time airborne radioactivity level indication and it is common practice to refer to sampled air even when discussing a CPAM, i. e. as opposed to monitored air, which would, strictly, be more correct. There are two types of CPAMs, fixed-filter and moving-filter. In the former, the medium does not move while the airborne material is collected. The latter type has two variants, the rectangular deposition area and the circular window. In both types of CPAM the sampled air is pulled by a pump through the piping of the monitor up to the structure holds the filter medium. It is important to note that CPAM pumps are designed to maintain a constant volumetric flowrate. The entire deposition area, regardless of its shape, is assumed to be viewed by a radiation detector of a type appropriate for the nuclide in question. Moving-filter monitors are used in applications where loading of the filter medium with dust is an issue. The moving-filter collection medium is assumed to move across the area at a constant. This rate is established in such a way that a roll of the filter tape will last about one month. The rectangular-window moving filter monitor will be denoted as RW, CPAMs are used to monitor the air effluents from nuclear facilities, notably power reactors
