Uranium adalah logam yang sangat berat yang dapat digunakan sebagai sumber berlimpah energi terkonsentrasi.
Uranium terjadi di sebagian besar batuan dalam konsentrasi 2 sampai 4 bagian per juta dan adalah sebagai umum di kerak bumi sebagai timah, tungsten dan molibdenum. Uranium terjadi pada air laut, dan dapat pulih dari lautan.
Uranium ditemukan pada tahun 1789 oleh Martin Klaproth, seorang kimiawan Jerman, dalam mineral yang disebut bijih-bijih uranium. Hal ini dinamakan planet Uranus, yang telah ditemukan delapan tahun sebelumnya.
Uranium tampaknya dibentuk pada supernova sekitar 6,6 miliar tahun yang lalu. Meskipun tidak umum di tata surya, hari ini peluruhan radioaktif lambat menyediakan sumber utama panas di dalam bumi, sehingga menyebabkan konveksi dan pergeseran benua.
Kepadatan tinggi uranium berarti bahwa ia juga menemukan penggunaan dalam keels dari yacht dan sebagai counterweights untuk permukaan kontrol pesawat, serta untuk radiasi perisai.
Uranium memiliki titik leleh 1.132 ° C. Simbol kimia untuk uranium adalah U.
Uranium terjadi di sebagian besar batuan dalam konsentrasi 2 sampai 4 bagian per juta dan adalah sebagai umum di kerak bumi sebagai timah, tungsten dan molibdenum. Uranium terjadi pada air laut, dan dapat pulih dari lautan.
Uranium ditemukan pada tahun 1789 oleh Martin Klaproth, seorang kimiawan Jerman, dalam mineral yang disebut bijih-bijih uranium. Hal ini dinamakan planet Uranus, yang telah ditemukan delapan tahun sebelumnya.
Uranium tampaknya dibentuk pada supernova sekitar 6,6 miliar tahun yang lalu. Meskipun tidak umum di tata surya, hari ini peluruhan radioaktif lambat menyediakan sumber utama panas di dalam bumi, sehingga menyebabkan konveksi dan pergeseran benua.
Kepadatan tinggi uranium berarti bahwa ia juga menemukan penggunaan dalam keels dari yacht dan sebagai counterweights untuk permukaan kontrol pesawat, serta untuk radiasi perisai.
Uranium memiliki titik leleh 1.132 ° C. Simbol kimia untuk uranium adalah U.
Uranium Atom
Pada skala diatur sesuai dengan massa meningkatnya inti mereka, uranium merupakan salah satu yang terberat dari semua unsur yang terjadi secara alamiah (Hidrogen adalah yang paling ringan). Uranium adalah 18,7 kali lebih padat seperti air.
Seperti unsur-unsur lain, uranium terjadi dalam beberapa bentuk yang sedikit berbeda dikenal sebagai 'isotop'. Isotop ini berbeda satu sama lain dalam jumlah partikel bermuatan (neutron) dalam nukleus. Uranium alam seperti yang ditemukan di kerak bumi adalah campuran sebagian dari dua isotop: uranium-238 (U-238), akuntansi untuk 99,3% dan uranium-235 (U-235) sekitar 0,7% diagram an Atom
Isotop U-235 adalah penting karena dalam kondisi tertentu dapat dengan mudah dibagi, menghasilkan banyak energi. Oleh karena itu dikatakan 'fisi' dan kita menggunakan ungkapan 'fisi nuklir'.
Sementara itu, seperti semua isotop radioaktif, mereka membusuk. U-238 meluruh sangat lambat, paruhnya menjadi hampir sama dengan usia Bumi (4500000000 tahun). Ini berarti bahwa hampir tidak radioaktif, kurang begitu daripada banyak isotop lain di bebatuan dan pasir. Namun demikian itu menghasilkan 0,1 watt / ton sebagai peluruhan panas dan ini cukup untuk menghangatkan inti bumi. U-235 meluruh sedikit lebih cepat.
Pada skala diatur sesuai dengan massa meningkatnya inti mereka, uranium merupakan salah satu yang terberat dari semua unsur yang terjadi secara alamiah (Hidrogen adalah yang paling ringan). Uranium adalah 18,7 kali lebih padat seperti air.
Seperti unsur-unsur lain, uranium terjadi dalam beberapa bentuk yang sedikit berbeda dikenal sebagai 'isotop'. Isotop ini berbeda satu sama lain dalam jumlah partikel bermuatan (neutron) dalam nukleus. Uranium alam seperti yang ditemukan di kerak bumi adalah campuran sebagian dari dua isotop: uranium-238 (U-238), akuntansi untuk 99,3% dan uranium-235 (U-235) sekitar 0,7% diagram an Atom
Isotop U-235 adalah penting karena dalam kondisi tertentu dapat dengan mudah dibagi, menghasilkan banyak energi. Oleh karena itu dikatakan 'fisi' dan kita menggunakan ungkapan 'fisi nuklir'.
Sementara itu, seperti semua isotop radioaktif, mereka membusuk. U-238 meluruh sangat lambat, paruhnya menjadi hampir sama dengan usia Bumi (4500000000 tahun). Ini berarti bahwa hampir tidak radioaktif, kurang begitu daripada banyak isotop lain di bebatuan dan pasir. Namun demikian itu menghasilkan 0,1 watt / ton sebagai peluruhan panas dan ini cukup untuk menghangatkan inti bumi. U-235 meluruh sedikit lebih cepat.
Energi dari atom uranium
Inti atom U-235 terdiri dari 92 proton dan neutron 143 (92 + 143 = 235). Ketika inti atom U-235 menangkap neutron bergerak terbagi dalam dua (fisi) dan melepaskan beberapa energi dalam bentuk panas, juga dua atau tiga neutron tambahan terlempar. Jika cukup ini neutron dikeluarkan menyebabkan inti U-235 atom lain untuk membagi, melepaskan neutron lebih lanjut, sebuah fisi 'reaksi berantai' dapat dicapai. Ketika hal ini terjadi berulang-ulang, jutaan kali, jumlah yang sangat besar panas yang dihasilkan dari jumlah yang relatif kecil dari uranium.
Ini adalah proses ini, pada dasarnya "membakar" uranium, yang terjadi pada reaktor nuklir. Panas digunakan untuk membuat uap untuk menghasilkan listrik.
Di dalam reaktor
Pembangkit listrik tenaga nuklir dan pembangkit listrik berbahan bakar fosil dari kapasitas yang sama memiliki banyak fitur yang sama. Keduanya memerlukan panas untuk menghasilkan uap untuk menggerakkan turbin dan generator. Dalam sebuah stasiun tenaga nuklir, namun, reaksi fisi atom uranium menggantikan pembakaran batubara atau gas.In reaktor nuklir bahan bakar uranium dirakit sedemikian rupa sehingga reaksi berantai fisi terkendali dapat dicapai. Panas yang diciptakan dengan memisahkan U-235 atom kemudian digunakan untuk membuat uap yang berputar turbin untuk menggerakkan generator, menghasilkan listrik.
Reaksi berantai yang terjadi di inti reaktor nuklir dikontrol oleh batang yang menyerap neutron dan yang dapat dimasukkan atau ditarik untuk mengatur reaktor pada tingkat daya yang diperlukan.
Unsur-unsur bahan bakar dikelilingi oleh zat yang disebut moderator untuk memperlambat kecepatan neutron dipancarkan sehingga memungkinkan reaksi berantai untuk melanjutkan. Air, grafit dan air berat digunakan sebagai moderator dalam berbagai jenis reaktor.
Karena jenis bahan bakar yang digunakan (yaitu konsentrasi U-235, lihat di bawah), jika ada kerusakan dikoreksi utama dalam reaktor bahan bakar mungkin terlalu panas dan meleleh, tetapi tidak dapat meledak seperti bom.
Sebuah khas 1.000 megawatt (MWe) reaktor dapat memberikan listrik yang cukup untuk sebuah kota modern hingga satu juta orang.
Uranium dan Plutonium
Sedangkan inti U-235 adalah 'fisil', yaitu U-238 dikatakan 'subur'. Ini berarti bahwa hal itu dapat menangkap salah satu neutron yang terbang di sekitar inti reaktor dan menjadi (secara tidak langsung) plutonium-239, yang merupakan fisil. Pu-239 sangat banyak seperti U-235, dalam hal ini fisi bila terkena neutron dan ini juga menghasilkan banyak energi.
Karena ada begitu banyak U-238 dalam inti reaktor (sebagian besar bahan bakar), reaksi ini sering terjadi, dan pada kenyataannya sekitar sepertiga dari hasil energi bahan bakar berasal dari "pembakaran" Pu-239.
Tapi kadang-kadang atom Pu-239 hanya menangkap neutron tanpa membelah, dan itu menjadi Pu-240. Karena Pu-239 adalah baik semakin "terbakar" atau menjadi Pu-240, semakin lama tetap bahan bakar dalam reaktor semakin Pu-240 yang ada di dalamnya. (Signifikansi hal ini adalah bahwa ketika bahan bakar bekas dihapus setelah sekitar tiga tahun, plutonium di dalamnya tidak cocok untuk membuat senjata tetapi dapat didaur ulang sebagai bahan bakar.)
Dari bijih uranium untuk bahan bakar reaktor
Bijih uranium dapat ditambang dengan metode bawah tanah atau open-cut, tergantung pada kedalaman. Setelah pertambangan, bijih dihancurkan dan digiling. Maka diperlakukan dengan asam untuk melarutkan uranium, yang pulih dari solusi.
Uranium juga dapat ditambang oleh in situ pencucian (ISL), di mana ia terlarut dari tubuh bijih bawah tanah berpori in situ dan dipompa ke permukaan.
Produk akhir dari tahap pertambangan dan penggilingan, atau dari ISL, adalah oksida uranium konsentrat (U3O8). Ini adalah bentuk yang uranium dijual.
Sebelum dapat digunakan dalam reaktor untuk pembangkit listrik, bagaimanapun, harus menjalani serangkaian proses untuk menghasilkan bahan bakar yang bisa digunakan.
Untuk sebagian besar dari reaktor di dunia, langkah berikutnya dalam pembuatan bahan bakar adalah untuk mengubah uranium oksida menjadi gas, uranium heksafluorida (UF6), yang memungkinkan untuk diperkaya. Pengayaan meningkatkan proporsi isotop uranium-235 dari level alaminya dari 0,7% menjadi 4 - 5%. Hal ini memungkinkan efisiensi teknis yang lebih besar dalam desain dan operasi reaktor, terutama dalam reaktor yang lebih besar, dan memungkinkan penggunaan air biasa sebagai moderator.
Setelah pengayaan, gas UF6 dikonversi menjadi uranium dioksida (UO2) yang dibentuk menjadi pelet bahan bakar. Pelet bahan bakar ini ditempatkan di dalam tabung logam tipis yang dirakit di bundel menjadi elemen bahan bakar atau majelis untuk inti reaktor.
Untuk reaktor yang menggunakan uranium alam sebagai bahan bakar mereka (dan karenanya yang memerlukan grafit atau air berat sebagai moderator) konsentrat U3O8 hanya perlu disempurnakan dan dikonversi langsung ke uranium dioksida.
Ketika bahan bakar uranium telah reaktor selama sekitar tiga tahun, bahan bakar yang digunakan dihapus, disimpan, dan kemudian diolah atau dibuang bawah tanah (lihat Siklus Bahan Bakar Nuklir atau Pengelolaan Limbah Radioaktif di seri ini).
Siapa yang menggunakan tenaga nuklir?
Sekitar 12% dari listrik dunia dihasilkan dari uranium di reaktor nuklir. Jumlah ini lebih dari 2500 milyar kWh setiap tahun, sebanyak dari semua sumber listrik di seluruh dunia pada tahun 1960.
Ini berasal dari beberapa 430 reaktor nuklir dengan kapasitas produksi total sekitar 375 000 megawatt (MWe) yang beroperasi di 31 negara. Lebih dari 70 lebih reaktor sedang dibangun dan 170 lainnya direncanakan.
Belgia, Bulgaria, Republik Ceko, Finlandia, Perancis, Hungaria, Jepang, Korea Selatan, Slovakia, Slovenia, Swedia, Swiss dan Ukraina semua mendapatkan 30% atau lebih dari listrik mereka dari reaktor nuklir. Amerika Serikat memiliki 100 reaktor beroperasi, memasok 20% listriknya. Perancis mendapat tiga perempat dari listrik dari uranium.
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| Pembangkit Listrik Tenaga Nuklir Di Berbagai Negara |
Lihat juga Tabel Dunia Tenaga Nuklir Reaktor
Siapa yang memiliki dan siapa tambang uranium?
Uranium tersebar luas di banyak batu, dan bahkan dalam air laut. Namun, seperti logam lainnya, jarang cukup terkonsentrasi untuk secara ekonomis. Di mana itu, kita berbicara tentang sebuah badan bijih. Dalam mendefinisikan apa yang bijih, asumsi yang dibuat tentang biaya pertambangan dan harga pasar logam. Oleh karena itu, cadangan uranium dihitung sebagai dipulihkan ton hingga biaya tertentu.
Sumber Australia dikenal lebih 1,6 juta ton uranium sampai dengan US $ 130 / kg U (saat ini sedikit di atas pasar 'spot' harga), Kazakhstan adalah lebih dari 600.000 ton uranium dan Kanada dan Rusia adalah lebih dari 450.000 tU. Sumber Australia dalam kategori ini adalah hampir sepertiga dari total dunia, Kazakhstan adalah 12%, Kanada dan Rusia masing-masing 9%.
Beberapa negara memiliki sumber daya yang signifikan uranium. Selain empat besar, mereka berada di urutan: Niger, Afrika Selatan, Brasil, Namibia, Amerika Serikat, China, Ukraina, Uzbekistan, Mongolia, dan Yordania. Negara-negara lain memiliki deposito yang lebih kecil yang dapat ditambang jika diperlukan.
Kazakhstan adalah produsen top dunia uranium, diikuti oleh Kanada dan kemudian Australia sebagai pemasok utama uranium ke pasar dunia - sekarang lebih dari 68.000 tU per tahun.
Uranium dijual hanya untuk negara-negara yang penandatangan Traktat Non-Proliferasi Nuklir (NPT), dan yang memungkinkan inspeksi internasional untuk memverifikasi bahwa itu hanya digunakan untuk tujuan damai.
Kegunaan lain dari energi nuklir
Banyak orang, ketika berbicara tentang energi nuklir, memiliki reaktor nuklir hanya (atau senjata nuklir mungkin) dalam pikiran. Hanya sedikit orang yang menyadari sejauh mana penggunaan radioisotop telah mengubah kehidupan kita selama beberapa dekade terakhir.
Menggunakan reaktor nuklir tujuan khusus yang relatif kecil adalah mungkin untuk membuat berbagai bahan radioaktif (radioisotop) dengan biaya rendah. Untuk alasan ini penggunaan radioisotop artifisial diproduksi telah menyebar luas sejak awal 1950-an, dan sekarang ada lebih dari 200 "penelitian" reaktor di 56 negara memproduksi mereka. Ini pada dasarnya pabrik neutron daripada sumber panas.
radioisotop
Dalam kehidupan kita sehari-hari kita membutuhkan makanan, air dan kesehatan yang baik. Hari ini, isotop radioaktif memainkan peranan penting dalam teknologi yang menyediakan kita dengan ketiga. Mereka diproduksi oleh membombardir sejumlah kecil elemen tertentu dengan neutron.
Dalam pengobatan, radioisotop banyak digunakan untuk diagnosis dan penelitian. Pelacak kimia radioaktif memancarkan radiasi gamma yang menyediakan informasi diagnostik tentang anatomi seseorang dan fungsi organ-organ tertentu. Radioterapi juga menggunakan radioisotop dalam pengobatan beberapa penyakit, seperti kanker. Sekitar satu orang di dua di dunia barat kemungkinan akan mengalami manfaat dari kedokteran nuklir dalam hidup mereka. Lebih sumber gamma yang kuat digunakan untuk mensterilkan jarum suntik, perban dan peralatan medis lainnya - sterilisasi gamma peralatan hampir universal.
Dalam pelestarian makanan, radioisotop digunakan untuk menghambat tunas tanaman akar setelah panen, untuk membunuh parasit dan hama, dan untuk mengontrol pematangan buah dan sayuran disimpan. Bahan makanan iradiasi diterima oleh otoritas dunia dan kesehatan nasional untuk konsumsi manusia dalam peningkatan jumlah negara. Mereka termasuk kentang, bawang, kering dan buah-buahan segar, biji-bijian dan biji-bijian produk, unggas dan ikan. Beberapa makanan prepacked juga dapat disinari.
Dalam tumbuhnya tanaman dan peternakan, radioisotop juga memainkan peran penting. Mereka digunakan untuk memproduksi unggul, varietas tahan penyakit dan tahan cuaca tinggi tanaman, untuk mempelajari bagaimana pupuk dan insektisida kerja, serta meningkatkan produktivitas dan kesehatan hewan domestik.
Secara industri, dan pertambangan, mereka digunakan untuk memeriksa lasan, untuk mendeteksi kebocoran, untuk mempelajari laju keausan logam, dan untuk analisis on-stream dari berbagai mineral dan bahan bakar.
Ada banyak kegunaan lain. Sebuah radioisotop berasal dari plutonium terbentuk dalam reaktor nuklir digunakan dalam kebanyakan detektor asap rumah tangga.
Radioisotop yang digunakan untuk mendeteksi dan menganalisa polutan di lingkungan, dan untuk mempelajari gerakan air permukaan di sungai dan juga dari tanah.
reaktor lainnya
Ada juga kegunaan lain untuk reaktor nuklir. Sekitar 200 reaktor nuklir kecil daya sekitar 150 kapal, sebagian besar kapal selam, tetapi mulai dari pembuka percakapan ke kapal induk. Ini bisa tinggal di laut untuk waktu yang lama tanpa harus melakukan pengisian bahan bakar berhenti. Di Kutub Utara Rusia di mana kondisi operasi berada di luar kemampuan pembuka percakapan konvensional, kapal bertenaga nuklir sangat kuat beroperasi sepanjang tahun, di mana sebelumnya hanya dua bulan diperbolehkan akses utara setiap tahun.
Panas yang dihasilkan oleh reaktor nuklir juga dapat digunakan secara langsung bukan untuk menghasilkan listrik. Di Swedia dan Rusia, misalnya, panas surplus digunakan untuk memanaskan bangunan. Panas nuklir juga dapat digunakan untuk berbagai proses industri seperti desalinasi air. Desalinasi nuklir kemungkinan menjadi area pertumbuhan utama dalam dekade berikutnya.
Suhu tinggi panas dari reaktor nuklir kemungkinan akan digunakan dalam beberapa proses industri di masa depan, terutama untuk membuat hidrogen.
Sumber-sumber militer bahan bakar
Kedua uranium dan plutonium yang digunakan untuk membuat bom sebelum mereka menjadi penting untuk membuat listrik dan radioisotop. Jenis uranium dan plutonium untuk bom berbeda dari yang di pembangkit listrik tenaga nuklir. Bom uranium sangat diperkaya (> 90% U-235, bukannya hingga 5%); bom plutonium cukup murni Pu-239 (> 90%, bukan 60% pada reaktor-grade) dan dibuat dalam reaktor khusus.
Sejak 1990-an, karena perlucutan senjata, banyak uranium militer telah menjadi tersedia untuk produksi listrik. Uranium militer diencerkan sekitar 25: 1 dengan depleted uranium (kebanyakan U-238) dari proses pengayaan sebelum digunakan dalam pembangkit listrik. Lebih dari dua dekade hingga 2013 sepersepuluh dari US listrik terbuat dari senjata Rusia uranium. Plutonium militer mulai digunakan sama, dicampur dengan uranium.
ENGLISH
Uranium is a heavy metal that can be used as an abundant source of concentrated energy.
Uranium occurs in most rocks in concentrations of 2 to 4 parts per million and is as common in the earth's crust as tin, tungsten and molybdenum. Uranium occurs in sea water, and can be recovered from the ocean.
Uranium was discovered in 1789 by Martin Klaproth, a German chemist, in the mineral called pitchblende. It was named after the planet Uranus, which had been discovered eight years earlier.
Uranium appears to be formed in a supernova about 6.6 billion years ago. Although not common in the solar system, today's slow radioactive decay provides the main source of heat in the earth, causing convection and continental drift.
The high density of uranium means that he also finds use in the keels of yachts and as counterweights for aircraft control surfaces, as well as for radiation shielding.
Uranium has a melting point of 1132 ° C. The chemical symbol for uranium is U.
uranium Atom
On a scale arranged according to increasing their core mass, uranium is one of the heaviest of all naturally occurring elements (Hydrogen is the lightest). Uranium is 18.7 times as dense as water.
As with other elements, uranium occurs in several slightly different forms known as 'isotopes'. These isotopes differ from each other in the number of charged particles (neutrons) in the nucleus. Natural uranium as found in the earth's crust is a mixture of two isotopes in part: uranium-238 (U-238), accounting for 99.3% and uranium-235 (U-235) of about 0.7% diagram of an Atom
Isotope U-235 is important because under certain conditions can be easily shared, generate a lot of energy. Therefore it is said 'fission' and we use the expression 'nuclear fission'.
Meanwhile, like all radioactive isotopes, they decay. U-238 decays very slowly, beak becomes almost equal to the age of the Earth (4.5 billion years). This means that virtually no radioactive, less so than many other isotopes in rocks and sand. Nevertheless it generates 0.1 watts / tonne as decay heat and this was enough to warm the earth's core. U-235 decays slightly faster.
Energy from uranium atoms
U-235 atom nucleus consists of protons and neutrons 92 143 (92 + 143 = 235). When the nuclei of U-235 captures a neutron moving divided into two (fission) and release some energy in the form of heat, also two or three additional neutrons thrown. If enough of these expelled neutrons cause the nuclei of other U-235 atoms to split, releasing further neutrons, a fission 'chain reaction' can be achieved. When this happens repeatedly, millions of times, a very large amount of heat generated from a relatively small amount of uranium.
It is this process, essentially "burning" uranium, which occurs in a nuclear reactor. The heat is used to make steam to generate electricity.
In the reactor
Nuclear power plants and fossil-fueled power plants of the same capacity has many of the same features. Both require heat to produce steam to drive a turbine and generator. In a nuclear power station, however, the fission of uranium atoms replaces the burning coal or nuclear reactor fuel gas.In uranium assembled such that a controlled fission chain reaction can be achieved. The heat created by separating U-235 atoms is then used to create steam that spins a turbine to drive a generator, producing electricity.
The chain reaction that occurs in the core of a nuclear reactor is controlled by rods that absorb neutrons and which can be inserted or withdrawn to set the reactor at the required power level.
Fuel elements surrounded by a substance called a moderator to slow down the speed of neutrons emitted allowing a chain reaction to proceed. Water, graphite and heavy water is used as a moderator in various types of reactors.
Because of the type of fuel used (ie the concentration of U-235, see below), if there is damage to a major correction in the fuel reactor may overheat and melt, but it can not explode like a bomb.
A typical 1,000-megawatt (MWe) reactor can provide enough electricity for a modern city up to one million people.
Uranium and Plutonium
While the U-235 nucleus is 'fissile', namely U-238 is said to be "fertile". This means that it can capture one of the neutrons flying around the core of the reactor and become (indirectly) plutonium-239, which is fissile. Pu-239 is very much like the U-235, in this case when exposed to neutrons and fission is also generate a lot of energy.
Because there are so many U-238 in the reactor core (mostly fuel), these reactions are common, and in fact about one-third of the fuel energy yield comes from "burning" Pu-239.
But sometimes the Pu-239 atom simply captures a neutron without splitting, and it becomes Pu-240. Because of Pu-239 is good getting "burned" or becomes Pu-240, the longer it remains in the reactor fuel more Pu-240 in it. (The significance of this is that when the spent fuel is removed after about three years, the plutonium in it is not suitable for making weapons but can be recycled as fuel.)
From uranium ore to fuel reactors
Uranium ore can be mined by underground methods or open-cut, depending on the depth. After mining, the ore crushed and milled. Then treated with acid to dissolve the uranium, which is recovered from the solution.
Uranium can also be mined by in situ leaching (ISL), in which he dissolved from a porous underground ore body in situ and pumped to the surface.
The end product of mining and milling stages, or of ISL, is uranium oxide concentrate (U3O8). It is a form of uranium sold.
Before it can be used in reactors for power generation, however, have to undergo a series of processes to produce a fuel that can be used.
For most of the reactors in the world, the next step in the manufacture of fuel is to convert the uranium oxide into a gas, uranium hexafluoride (UF6), which allows for enriched. Enrichment increases the proportion of uranium-235 isotope from its natural level of 0.7% to 4-5%. This enables greater technical efficiency in the design and operation of the reactor, particularly in larger reactors, and allows the use of ordinary water as a moderator.
After enrichment, UF6 gas is converted into uranium dioxide (UO2) which is formed into fuel pellets. The fuel pellets are placed inside a thin metal tube, assembled in bundles into fuel elements or assemblies for the reactor core.
For reactors use natural uranium as fuel them (and hence which require graphite or heavy water as a moderator) U3O8 concentrate only needs to be refined and converted directly to uranium dioxide.
When uranium reactor fuel for about three years, the fuel used is removed, stored, and then processed or disposed of underground (see Nuclear Fuel Cycle or Radioactive Waste Management in this series).
Who uses nuclear power?
Approximately 12% of the world's electricity is generated from uranium in nuclear reactors. This amount is more than 2500 billion kWh per year, a total of all sources of electricity worldwide in 1960.
It comes from some 430 nuclear reactors with a total production capacity of approximately 375 000 megawatts (MWe) operating in 31 countries. More than 70 more reactors are under construction and another 170 planned.
Belgium, Bulgaria, Czech Republic, Finland, France, Hungary, Japan, South Korea, Slovakia, Slovenia, Sweden, Switzerland and Ukraine all get 30% or more of their electricity from nuclear reactors. The United States has 100 reactors in operation, supplying 20% of its electricity. France gets three-quarters of its electricity from uranium.
Nuclear Power Plant in Various Countries
See also Table World Nuclear Power Reactors
Who has and who uranium mine?
Uranium is widespread in many rocks, and even in seawater. However, like other metals, rare enough to be economically concentrated. Where it is, we are talking about an orebody. In defining what is ore, assumptions are made about the cost of mining and metal market prices. Therefore, uranium reserves calculated as restored ton until a certain fee.
Sources Australia is known to be 1.6 million tons of uranium up to US $ 130 / kg U (currently slightly above the market 'spot' price), Kazakhstan is more than 600,000 tons of uranium and Canada and Russia are more than 450,000 tU. Australian sources in this category is almost one third of the total world, Kazakhstan is 12%, Canada and Russia respectively 9%.
Some countries have significant resources of uranium. In addition to the big four, they are in order: Niger, South Africa, Brazil, Namibia, the United States, China, Ukraine, Uzbekistan, Mongolia, and Jordan. Other countries have smaller deposits that can be mined if necessary.
Kazakhstan is the world's top producer of uranium, followed by Canada and then Australia as a major supplier of uranium to the world market - now more than 68,000 tU per year.
Uranium is sold only to countries that are signatories to the Nuclear Non-Proliferation Treaty (NPT), and which allow international inspections to verify that it is used only for peaceful purposes.
Other uses of nuclear energy
Many people, when talking about nuclear energy, have only nuclear reactors (or perhaps nuclear weapons) in mind. Few people realize the extent to which the use of radioisotopes has changed our lives over the last few decades.
Using nuclear reactors are relatively small special purpose it is possible to make a variety of radioactive materials (radioisotopes) at low cost. For this reason the use of artificially produced radioisotopes has become widespread since the early 1950s, and now there are more than 200 "research" reactors in 56 countries producing them. It's basically a neutron factory rather than a source of heat.
radioisotopes
In our daily life we need food, water and good health. Today, radioactive isotopes play an important role in technology that provides us with all three. They are produced by bombarding a small number of specific elements with neutrons.
In medicine, radioisotopes are widely used for the diagnosis and research. Radioactive chemical tracers emit gamma radiation which provides diagnostic information about a person's anatomy and function of certain organs. Radiotherapy also use radioisotopes in the treatment of several diseases, such as cancer. About one person in two in the western world is likely to experience the benefits of nuclear medicine in their lives. More powerful gamma sources are used to sterilize syringes, bandages and other medical equipment - gamma sterilization of equipment is almost universal.
In the preservation of food, radioisotopes are used to inhibit plant shoots roots after harvest, to kill parasites and pests, and to control the ripening of fruits and vegetables are stored. Irradiated food ingredients accepted by the world and national health authorities for human consumption in an increasing number of countries. They include potatoes, onions, dried and fresh fruits, grains and grain products, poultry and fish. Some prepacked foods can also be illuminated.
In the growth of plants and livestock, radioisotopes also play an important role. They are used to produce superior, disease-resistant varieties and high weather resistant plants, to learn how fertilizers and insecticides work, as well as improving the productivity and health of domestic animals.
In industry, and mining, they are used to inspect welds, to detect leaks, to study the wear rate of metal, and for on-stream analysis of various minerals and fuels.
There are many other uses. A radioisotope derived from the plutonium formed in nuclear reactors used in most household smoke detectors.
Radioisotopes are used to detect and analyze pollutants in the environment, and to study the movement of surface water in the river and also from the ground.
other reactor
There are also other uses for nuclear reactors. Approximately 200 small nuclear reactors power about 150 ships, mostly submarines, but ranging from icebreakers to aircraft carriers. It can stay at sea for long periods without having to make refueling stops. In the Russian Arctic where operating conditions are beyond the capability of conventional icebreakers, nuclear-powered ships are very robust in operation throughout the year, where previously only two months are allowed access to the north every year.
The heat generated by nuclear reactors can also be used directly instead to generate electricity. In Sweden and Russia, for example, surplus heat is used to heat the building. Nuclear heat can also be used for a variety of industrial processes such as water desalination. Nuclear desalination is likely to be a major growth area in the next decade.
High-temperature heat from nuclear reactors are likely to be used in some industrial processes in the future, especially to make hydrogen.
Military sources of fuel
Both uranium and plutonium used to make bombs before they became important for making electricity and radioisotopes. Type of uranium and plutonium for bombs is different from that in nuclear power plants. Highly enriched uranium bomb (> 90% U-235, instead of up to 5%); pure enough plutonium bomb Pu-239 (> 90%, not 60% of the reactor-grade) and is made in a special reactor.
Since the 1990s, because of disarmament, a lot of military uranium has become available for the production of electricity. Military uranium is diluted about 25: 1 with depleted uranium (mostly U-238) from the enrichment process before being used in power plants. More than two decades until 2013, a tenth of US electricity made from Russian weapons uranium. Began to use the same military plutonium mixed with uranium.
Uranium occurs in most rocks in concentrations of 2 to 4 parts per million and is as common in the earth's crust as tin, tungsten and molybdenum. Uranium occurs in sea water, and can be recovered from the ocean.
Uranium was discovered in 1789 by Martin Klaproth, a German chemist, in the mineral called pitchblende. It was named after the planet Uranus, which had been discovered eight years earlier.
Uranium appears to be formed in a supernova about 6.6 billion years ago. Although not common in the solar system, today's slow radioactive decay provides the main source of heat in the earth, causing convection and continental drift.
The high density of uranium means that he also finds use in the keels of yachts and as counterweights for aircraft control surfaces, as well as for radiation shielding.
Uranium has a melting point of 1132 ° C. The chemical symbol for uranium is U.
uranium Atom
On a scale arranged according to increasing their core mass, uranium is one of the heaviest of all naturally occurring elements (Hydrogen is the lightest). Uranium is 18.7 times as dense as water.
As with other elements, uranium occurs in several slightly different forms known as 'isotopes'. These isotopes differ from each other in the number of charged particles (neutrons) in the nucleus. Natural uranium as found in the earth's crust is a mixture of two isotopes in part: uranium-238 (U-238), accounting for 99.3% and uranium-235 (U-235) of about 0.7% diagram of an Atom
Isotope U-235 is important because under certain conditions can be easily shared, generate a lot of energy. Therefore it is said 'fission' and we use the expression 'nuclear fission'.
Meanwhile, like all radioactive isotopes, they decay. U-238 decays very slowly, beak becomes almost equal to the age of the Earth (4.5 billion years). This means that virtually no radioactive, less so than many other isotopes in rocks and sand. Nevertheless it generates 0.1 watts / tonne as decay heat and this was enough to warm the earth's core. U-235 decays slightly faster.
Energy from uranium atoms
U-235 atom nucleus consists of protons and neutrons 92 143 (92 + 143 = 235). When the nuclei of U-235 captures a neutron moving divided into two (fission) and release some energy in the form of heat, also two or three additional neutrons thrown. If enough of these expelled neutrons cause the nuclei of other U-235 atoms to split, releasing further neutrons, a fission 'chain reaction' can be achieved. When this happens repeatedly, millions of times, a very large amount of heat generated from a relatively small amount of uranium.
It is this process, essentially "burning" uranium, which occurs in a nuclear reactor. The heat is used to make steam to generate electricity.
In the reactor
Nuclear power plants and fossil-fueled power plants of the same capacity has many of the same features. Both require heat to produce steam to drive a turbine and generator. In a nuclear power station, however, the fission of uranium atoms replaces the burning coal or nuclear reactor fuel gas.In uranium assembled such that a controlled fission chain reaction can be achieved. The heat created by separating U-235 atoms is then used to create steam that spins a turbine to drive a generator, producing electricity.
The chain reaction that occurs in the core of a nuclear reactor is controlled by rods that absorb neutrons and which can be inserted or withdrawn to set the reactor at the required power level.
Fuel elements surrounded by a substance called a moderator to slow down the speed of neutrons emitted allowing a chain reaction to proceed. Water, graphite and heavy water is used as a moderator in various types of reactors.
Because of the type of fuel used (ie the concentration of U-235, see below), if there is damage to a major correction in the fuel reactor may overheat and melt, but it can not explode like a bomb.
A typical 1,000-megawatt (MWe) reactor can provide enough electricity for a modern city up to one million people.
Uranium and Plutonium
While the U-235 nucleus is 'fissile', namely U-238 is said to be "fertile". This means that it can capture one of the neutrons flying around the core of the reactor and become (indirectly) plutonium-239, which is fissile. Pu-239 is very much like the U-235, in this case when exposed to neutrons and fission is also generate a lot of energy.
Because there are so many U-238 in the reactor core (mostly fuel), these reactions are common, and in fact about one-third of the fuel energy yield comes from "burning" Pu-239.
But sometimes the Pu-239 atom simply captures a neutron without splitting, and it becomes Pu-240. Because of Pu-239 is good getting "burned" or becomes Pu-240, the longer it remains in the reactor fuel more Pu-240 in it. (The significance of this is that when the spent fuel is removed after about three years, the plutonium in it is not suitable for making weapons but can be recycled as fuel.)
From uranium ore to fuel reactors
Uranium ore can be mined by underground methods or open-cut, depending on the depth. After mining, the ore crushed and milled. Then treated with acid to dissolve the uranium, which is recovered from the solution.
Uranium can also be mined by in situ leaching (ISL), in which he dissolved from a porous underground ore body in situ and pumped to the surface.
The end product of mining and milling stages, or of ISL, is uranium oxide concentrate (U3O8). It is a form of uranium sold.
Before it can be used in reactors for power generation, however, have to undergo a series of processes to produce a fuel that can be used.
For most of the reactors in the world, the next step in the manufacture of fuel is to convert the uranium oxide into a gas, uranium hexafluoride (UF6), which allows for enriched. Enrichment increases the proportion of uranium-235 isotope from its natural level of 0.7% to 4-5%. This enables greater technical efficiency in the design and operation of the reactor, particularly in larger reactors, and allows the use of ordinary water as a moderator.
After enrichment, UF6 gas is converted into uranium dioxide (UO2) which is formed into fuel pellets. The fuel pellets are placed inside a thin metal tube, assembled in bundles into fuel elements or assemblies for the reactor core.
For reactors use natural uranium as fuel them (and hence which require graphite or heavy water as a moderator) U3O8 concentrate only needs to be refined and converted directly to uranium dioxide.
When uranium reactor fuel for about three years, the fuel used is removed, stored, and then processed or disposed of underground (see Nuclear Fuel Cycle or Radioactive Waste Management in this series).
Who uses nuclear power?
Approximately 12% of the world's electricity is generated from uranium in nuclear reactors. This amount is more than 2500 billion kWh per year, a total of all sources of electricity worldwide in 1960.
It comes from some 430 nuclear reactors with a total production capacity of approximately 375 000 megawatts (MWe) operating in 31 countries. More than 70 more reactors are under construction and another 170 planned.
Belgium, Bulgaria, Czech Republic, Finland, France, Hungary, Japan, South Korea, Slovakia, Slovenia, Sweden, Switzerland and Ukraine all get 30% or more of their electricity from nuclear reactors. The United States has 100 reactors in operation, supplying 20% of its electricity. France gets three-quarters of its electricity from uranium.
Nuclear Power Plant in Various Countries
See also Table World Nuclear Power Reactors
Who has and who uranium mine?
Uranium is widespread in many rocks, and even in seawater. However, like other metals, rare enough to be economically concentrated. Where it is, we are talking about an orebody. In defining what is ore, assumptions are made about the cost of mining and metal market prices. Therefore, uranium reserves calculated as restored ton until a certain fee.
Sources Australia is known to be 1.6 million tons of uranium up to US $ 130 / kg U (currently slightly above the market 'spot' price), Kazakhstan is more than 600,000 tons of uranium and Canada and Russia are more than 450,000 tU. Australian sources in this category is almost one third of the total world, Kazakhstan is 12%, Canada and Russia respectively 9%.
Some countries have significant resources of uranium. In addition to the big four, they are in order: Niger, South Africa, Brazil, Namibia, the United States, China, Ukraine, Uzbekistan, Mongolia, and Jordan. Other countries have smaller deposits that can be mined if necessary.
Kazakhstan is the world's top producer of uranium, followed by Canada and then Australia as a major supplier of uranium to the world market - now more than 68,000 tU per year.
Uranium is sold only to countries that are signatories to the Nuclear Non-Proliferation Treaty (NPT), and which allow international inspections to verify that it is used only for peaceful purposes.
Other uses of nuclear energy
Many people, when talking about nuclear energy, have only nuclear reactors (or perhaps nuclear weapons) in mind. Few people realize the extent to which the use of radioisotopes has changed our lives over the last few decades.
Using nuclear reactors are relatively small special purpose it is possible to make a variety of radioactive materials (radioisotopes) at low cost. For this reason the use of artificially produced radioisotopes has become widespread since the early 1950s, and now there are more than 200 "research" reactors in 56 countries producing them. It's basically a neutron factory rather than a source of heat.
radioisotopes
In our daily life we need food, water and good health. Today, radioactive isotopes play an important role in technology that provides us with all three. They are produced by bombarding a small number of specific elements with neutrons.
In medicine, radioisotopes are widely used for the diagnosis and research. Radioactive chemical tracers emit gamma radiation which provides diagnostic information about a person's anatomy and function of certain organs. Radiotherapy also use radioisotopes in the treatment of several diseases, such as cancer. About one person in two in the western world is likely to experience the benefits of nuclear medicine in their lives. More powerful gamma sources are used to sterilize syringes, bandages and other medical equipment - gamma sterilization of equipment is almost universal.
In the preservation of food, radioisotopes are used to inhibit plant shoots roots after harvest, to kill parasites and pests, and to control the ripening of fruits and vegetables are stored. Irradiated food ingredients accepted by the world and national health authorities for human consumption in an increasing number of countries. They include potatoes, onions, dried and fresh fruits, grains and grain products, poultry and fish. Some prepacked foods can also be illuminated.
In the growth of plants and livestock, radioisotopes also play an important role. They are used to produce superior, disease-resistant varieties and high weather resistant plants, to learn how fertilizers and insecticides work, as well as improving the productivity and health of domestic animals.
In industry, and mining, they are used to inspect welds, to detect leaks, to study the wear rate of metal, and for on-stream analysis of various minerals and fuels.
There are many other uses. A radioisotope derived from the plutonium formed in nuclear reactors used in most household smoke detectors.
Radioisotopes are used to detect and analyze pollutants in the environment, and to study the movement of surface water in the river and also from the ground.
other reactor
There are also other uses for nuclear reactors. Approximately 200 small nuclear reactors power about 150 ships, mostly submarines, but ranging from icebreakers to aircraft carriers. It can stay at sea for long periods without having to make refueling stops. In the Russian Arctic where operating conditions are beyond the capability of conventional icebreakers, nuclear-powered ships are very robust in operation throughout the year, where previously only two months are allowed access to the north every year.
The heat generated by nuclear reactors can also be used directly instead to generate electricity. In Sweden and Russia, for example, surplus heat is used to heat the building. Nuclear heat can also be used for a variety of industrial processes such as water desalination. Nuclear desalination is likely to be a major growth area in the next decade.
High-temperature heat from nuclear reactors are likely to be used in some industrial processes in the future, especially to make hydrogen.
Military sources of fuel
Both uranium and plutonium used to make bombs before they became important for making electricity and radioisotopes. Type of uranium and plutonium for bombs is different from that in nuclear power plants. Highly enriched uranium bomb (> 90% U-235, instead of up to 5%); pure enough plutonium bomb Pu-239 (> 90%, not 60% of the reactor-grade) and is made in a special reactor.
Since the 1990s, because of disarmament, a lot of military uranium has become available for the production of electricity. Military uranium is diluted about 25: 1 with depleted uranium (mostly U-238) from the enrichment process before being used in power plants. More than two decades until 2013, a tenth of US electricity made from Russian weapons uranium. Began to use the same military plutonium mixed with uranium.
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