Nuclear weapon designs are physical, chemical, and engineering arrangements that cause the physics package[1] of a nuclear weapon to detonate. There are three existing basic design types: pure fission weapons are the simplest, least technically demanding, were the first nuclear weapons built, and so far the only type ever used in warfare, by the United States on Japan in World War II boosted fission weapons increase yield beyond that of the implosion design, by using small quantities of fusion fuel to enhance the fission chain reaction. Boosting can more than double the weapon's fission energy yield. staged thermonuclear weapons are arrangements of two or more "stages", most usually two. The first stage is normally a boosted fission weapon as above (except for the earliest thermonuclear weapons, which used a pure fission weapon instead). Its detonation causes it to shine intensely with x-radiation, which illuminates and implodes the second stage filled with a large quantity of fusion fuel. This sets in motion a sequence of events which results in a thermonuclear, or fusion, burn. This process affords potential yields up to hundreds of times those of fission weapons.[2] Pure fission weapons have been the first type to be built by new nuclear powers. Large industrial states with well-developed nuclear arsenals have two-stage thermonuclear weapons, which are the most compact, scalable, and cost effective option, once the necessary technical base and industrial infrastructure are built. Most known innovations in nuclear weapon design originated in the United States, though some were later developed independently by other states.[3] In early news accounts, pure fission weapons were called atomic bombs or A-bombs and weapons involving fusion were called hydrogen bombs or H-bombs. Practitioners of nuclear policy, however, favor the terms nuclear and thermonuclear, respectively. Nuclear weapons Photograph of a mock-up of the Little Boy nuclear weapon dropped on Hiroshima, Japan, in August 1945. Background Nuclear explosion History Warfare Design Testing Delivery Yield Effects Winter Workers Ethics Arsenals Arms race Espionage Proliferation Disarmament Terrorism Opposition Nuclear-armed states NPT recognized United States Russia United Kingdom France China Others India Israel (undeclared) Pakistan North Korea Former South Africa Belarus Kazakhstan Ukraine vte Nuclear reactions Nuclear fission separates or splits heavier atoms to form lighter atoms. Nuclear fusion combines lighter atoms to form heavier atoms. Both reactions generate roughly a million times more energy than comparable chemical reactions, making nuclear bombs a million times more powerful than non-nuclear bombs, which a French patent claimed in May 1939.[4] In some ways, fission and fusion are opposite and complementary reactions, but the particulars are unique for each. To understand how nuclear weapons are designed, it is useful to know the important similarities and differences between fission and fusion. The following explanation uses rounded numbers and approximations.[5] Fission Main article: Nuclear fission When a free neutron hits the nucleus of a fissile atom like uranium-235 (235U), the uranium nucleus splits into two smaller nuclei called fission fragments, plus more neutrons (for 235U three about as often as two; an average of just under 2.5 per fission). The fission chain reaction in a supercritical mass of fuel can be self-sustaining because it produces enough surplus neutrons to offset losses of neutrons escaping the supercritical assembly. Most of these have the speed (kinetic energy) required to cause new fissions in neighboring uranium nuclei.[6] The uranium-235 nucleus can split in many ways, provided the charge numbers add up to 92 and the mass numbers add up to 236 (uranium-235 plus the neutron that caused the split). The following equation shows one possible split, namely into strontium-95 (95Sr), xenon-139 (139Xe), and two neutrons (n), plus energy:[7] 235 U + n ⟶ 95 S r + 139 X e + 2 n + 180 M e V {\displaystyle \ {}^{235}\mathrm {U} +\mathrm {n} \longrightarrow {}^{95}\mathrm {Sr} +{}^{139}\mathrm {Xe} +2\ \mathrm {n} +180\ \mathrm {MeV} } The immediate energy release per atom is about 180 million electron volts (MeV); i.e., 74 TJ/kg. Only 7% of this is gamma radiation and kinetic energy of fission neutrons. The remaining 93% is kinetic energy (or energy of motion) of the charged fission fragments, flying away from each other mutually repelled by the positive charge of their protons (38 for strontium, 54 for xenon). This initial kinetic energy is 67 TJ/kg, imparting an initial speed of about 12,000 kilometers per second. The charged fragments' high electric charge causes many inelastic coulomb collisions with nearby nuclei, and these fragments remain trapped inside the bomb's fissile pit and tamper until their motion is converted into heat. Given the speed of the fragments and the mean free path between nuclei in the compressed fuel assembly (for the implosion design), this takes about a millionth of a second (a microsecond), by which time the core and tamper of the bomb have expanded to plasma several meters in diameter with a temperature of tens of millions of degrees Celsius. This is hot enough to emit black-body radiation in the X-ray spectrum. These X-rays are absorbed by the surrounding air, producing the fireball and blast of a nuclear explosion. Most fission products have too many neutrons to be stable so they are radioactive by beta decay, converting neutrons into protons by throwing off beta particles (electrons) and gamma rays. Their half lives range from milliseconds to about 200,000 years. Many decay into isotopes that are themselves radioactive, so from 1 to 6 (average 3) decays may be required to reach stability.[8] In reactors, the radioactive products are the nuclear waste in spent fuel. In bombs, they become radioactive fallout, both local and global.[9] Meanwhile, inside the exploding bomb, the free neutrons released by fission carry away about 3% of the initial fission energy. Neutron kinetic energy adds to the blast energy of a bomb, but not as effectively as the energy from charged fragments, since neutrons do not give up their kinetic energy as quickly in collisions with charged nuclei or electrons. The dominant contribution of fission neutrons to the bomb's power is the initiation of subsequent fissions. Over half of the neutrons escape the bomb core, but the rest strike 235U nuclei causing them to fission in an exponentially growing chain reaction (1, 2, 4, 8, 16, etc.). Starting from one atom, the number of fissions can theoretically double a hundred times in a microsecond, which could consume all uranium or plutonium up to hundreds of tons by the hundredth link in the chain. Typically in a modern weapon, the weapon's pit contains 3.5 to 4.5 kilograms (7.7 to 9.9 lb) of plutonium and at detonation produces approximately 5 to 10 kilotonnes of TNT (21 to 42 TJ) yield, representing the fissioning of approximately 0.5 kilograms (1.1 lb) of plutonium.[10][11] Materials which can sustain a chain reaction are called fissile. The two fissile materials used in nuclear weapons are: 235U, also known as highly enriched uranium (HEU), "oralloy" meaning "Oak Ridge alloy",[12] or "25" (a combination of the last digit of the atomic number of uranium-235, which is 92, and the last digit of its mass number, which is 235); and 239Pu, also known as plutonium-239, or "49" (from "94" and "239").[13] Uranium's most common isotope, 238U, is fissionable but not fissile, meaning that it cannot sustain a chain reaction because its daughter fission neutrons are not (on average) energetic enough to cause follow-on 238U fissions. However, the neutrons released by fusion of the heavy hydrogen isotopes deuterium and tritium will fission 238U. This 238U fission reaction in the outer jacket of the secondary assembly of a two-stage thermonuclear bomb produces by far the greatest fraction of the bomb's energy yield, as well as most of its radioactive debris. For national powers engaged in a nuclear arms race, this fact of 238U's ability to fast-fission from thermonuclear neutron bombardment is of central importance. The plenitude and cheapness of both bulk dry fusion fuel (lithium deuteride) and 238U (a byproduct of uranium enrichment) permit the economical production of very large nuclear arsenals, in comparison to pure fission weapons requiring the expensive 235U or 239Pu fuels.
@piggyprohackerroman635
4 ай бұрын
cool ima use this to cheat if my nuke essay
@vpnmaster5000
4 ай бұрын
Grass is a type of plant with narrow leaves growing from the base. Their appearance as a common plant was in the mid-Cretaceous period. There are 12,000 species now.[3] A common kind of grass is used to cover the ground in places such as lawns and parks. Grass is usually the color green. That is because they are wind-pollinated rather than insect-pollinated, so they do not have to attract insects. Green is the best colour for photosynthesis. Grasslands such as savannah and prairie where grasses are dominant cover 40.5% of the land area of the Earth, except Greenland and Antarctica.[4] Grasses are monocotyledon herbaceous plants. They include the "grass" of the family Poaceae, which are called grass by ordinary people. This family is also called the Gramineae, and includes some of the sedges (Cyperaceae) and the rushes (Juncaceae).[5] These three families are not very closely related, though all of them belong to clades in the order Poales. They are similar adaptations to a similar life-style. With about 780 genera and about 12,000 species,[3] the Poaceae is the fifth-largest plant family. Only the Asteraceae, Orchidaceae, Fabaceae and Rubiaceae have more species.[6] The true grasses include cereals, bamboo and the grasses of lawns (turf) and grassland. Uses for graminoids include food (as grain, shoots or rhizomes), drink (beer, whisky), pasture for livestock, thatch, paper, fuel, clothing, insulation, construction, sports turf[broken anchor], basket weaving and many others. Many grasses are short, but some grasses can grow tall, such as bamboo. Plants from the grass family can grow in many places and make grasslands, including areas which are very dry or cold. There are several other plants that look similar to grass and are referred to as such, but are not members of the grass family. These plants include rushes, reeds, papyrus and water chestnut. Seagrass is a monocot in the order Alismatales. Grasses are an important food for many animals, such as deer, buffalo, cattle, mice, grasshoppers, caterpillars and many other grazers. Unlike other plants, grasses grow from the bottom, so when animals eat grass they usually do not destroy the part that grows.[7] This is part of the reason why the plants are so successful. Without grass, more soil might wash away into rivers (erosion).
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