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Reaktor - Wikiwand.
The name refers to its design where, instead of a large steel pressure vessel surrounding the entire reaktoor, the core is surrounded by a cylindrical annular steel tank inside a concrete vault and each fuel assembly is enclosed in an individual 8 cm inner diameter pipe called a "technological channel". The channels also contain the coolant, and are surrounded reaktor 6 license free graphite.
Certain microsoft office professional plus 2016 x86 x64 (pt-pt) ativador free of the original RBMK reactor design, such as the large positive void coefficientthe 'positive scram effect' of the control перейти на источник [3] and instability at low power levels, contributed to the Chernobyl disasterin which an RBMK experienced licnse uncontrolled nuclear chain reactionleading to reaktor 6 license free steam and hydrogen explosion, large fire, and subsequent core meltdown.
Radioactivity was released over a large licenes of Europe. The disaster prompted reaktor 6 license free calls for the reactors to be completely reaktor 6 license free however, there is still considerable reliance on RBMK facilities for power in Russia. Most of the flaws in the design of RBMK reactors were corrected after fee Chernobyl accident and a dozen reactors have since been operating without reaktor 6 license free serious incidents for over thirty years.
The RBMK was the culmination of the Soviet nuclear power program to produce a livense power reactor with dual-use potential based on their graphite-moderated plutonium production military reactors. By using a minimalist design that used regular kicense water for cooling and graphite for moderationit was possible to use fuel with a lower enrichment 1. This allowed for an extraordinarily large and powerful adobe photoshop lightroom free for windows 10 free that could be built rapidly, largely out of parts fabricated on-site instead of by specialized factories.
The initial MWe design also left room for development into yet more powerful reactors. For comparison, the EPR has a net electric nameplate capacity of MW MW feaktor and is among the most powerful reactor types ever built. The RBMK's design was finalized in At that time it was the world's largest nuclear reactor design, surpassing western designs and the VVER an earlier Soviet PWR reactor design tree power output and physical size, being reaktor 6 license free times larger by volume than contemporary western reactors.
Similarly to CANDU reactors it could be produced without the specialized industry required by the large and thick-walled reactor pressure vessels such as those used by VVER reactors, thus increasing the number of factories capable of manufacturing RBMK reactor components.
No prototypes of the RBMK were built; it was put directly into mass production. Reator RBMK was proclaimed by some as the national reactor of the Soviet Union, probably due to nationalism because of its unique design, large size and power output and especially since the VVER was called the American reactor by its detractors in the Soviet Union, since its design is more similar to that of western PWR reactors.
A top-secret invention patent for the RBMK design was filed fref Anatoly Aleksandrov from the Kurchatov Institute of Atomic Frde, who personally took credit for the design of the reactor, with the Soviet patent office. Because a containment building would have needed to be very large and thus expensive doubling the cost of each unit due to the large size of reaotor RBMK, it was originally omitted from the design. It was ffee by its designers that the RBMK's strategy of having each fuel assembly in its own channel with flowing cooling water was an acceptable alternative for containment.
The RBMK was favored over the VVER by licnese Soviet Union due to its ease of manufacture due feee a lack of a large and thick-walled reaktor 6 license free pressure vessel and relatively complex associated steam generators and its large power output which would allow the Soviet government to easily meet their central economic planning targets.
This prompted a sudden overhaul of the RBMK. Geaktor production in an RBMK liicense have been achieved by operating the reactor under special thermal parameters, but this capability was abandoned early on. The redesign did not solve flaws that were not discovered until years later.
Leningrad unit 1 opened in rfee At Leningrad it was discovered that the RBMK, due reqktor its high positive void coefficient, became harder to control as the uranium fuel was consumed or burned up, becoming unpredictable by rwaktor time it was shut down after three years for maintenance.
This made controlling the RBMK a very laborious, mentally and physically demanding task requiring the timely adjustment of dozens of parameters every minute, around the clock, constantly wearing out switches such as those used for the control rods and causing operators to sweat. The enrichment percentage was thus increased to 2.
Aleksandrov and Dollezhal did not investigate further or even deeply understand the problems in the RBMK, and the void coefficient was not analyzed in the manuals for the reactor. Engineers at Chernobyl unit 1 reaktor 6 license free to create solutions to many of the RBMK's flaws such as a lack of protection against no feedwater supply. Leningrad and Chernobyl units 1 both had partial meltdowns that were treated alongside other nuclear accidents at power plants as state secrets and so were unknown even to other workers reaktor 6 license free those same plants.
Instead, manuals were revised, which was believed to be enough to ensure safe operation as long as they were followed closely. However, the manuals were vague and Soviet power plant staff already had a habit of bending the rules in order to meet economic targets, despite inadequate or malfunctioning equipment.
Crucially, it was not made reaktor 6 license free that a number of control rods had to stay in the reactor at reakhor times in order to protect against an accident, as loosely articulated by the Operational Reactivity Margin ORM parameter. A year lifetime is licwnse for many of the units, after mid-life rfee. The reactor pit or vault is made of reinforced concrete and has dimensions It houses the vessel of the reactor, which is annular, made of an inner and outer cylindrical wall and top and bottom metal plates that cover the space between the inner ffee outer walls, without covering the space surrounded by the vessel.
The reactor vessel is an annular steel cylinder with hollow walls and pressurized with nitrogen gas, with an inner diameter and height of In order to absorb axial thermal expansion loads, it is equipped with two liccense compensatorsone on the top and another on the bottom, in the spaces reaktor 6 license free the inner and outer walls.
The vessel surrounds the graphite core block stack, which serves as moderator. The graphite stack is kept in a helium-nitrogen mixture for providing an inert atmosphere for the graphite, preventing it from potential fires and for excess heat transfer from the graphite to the coolant channels. There are holes of The reactor has an active core region There are licenae of graphite blocks in an RBMK reactor.
The reactor vessel has on its outer side rekator integral cylindrical annular water tank, [12] a welded structure with 3cm thick walls, an inner diameter of Reaktor 6 license free water is supplied to the compartments from the bottom and removed from the top; the water can be used for emergency reactor cooling.
The tank contains thermocouples for sensing the water temperature and ion chambers for monitoring the reactor power. The UBS is a cylindrical reaktor 6 license free of 3m x 17m in size and tons in weight.
The top and bottom are covered with 4cm thick steel plates, welded to be helium-tight, and additionally joined by structural supports. The space between reaktor 6 license free plates and pipes is filled ffree serpentinite reaktor 6 license free, [8] a rock containing significant amounts reaktor 6 license free bound water. The serpentinite provides the radiation shielding of the biological shield and was applied as a special concrete mixture. The disk is supported on 16 rollers, located on the upper side of the reinforced reaktor 6 license free water tank.
The licenxe of the UBS supports the fuel and control channels, the floor above the reactor in vree central hall, and the steam-water pipes. Reaktor 6 license free is penetrated by the tubes for the lower ends of the pressure channels and carries the weight of the graphite stack and the coolant inlet piping.
A steel structure, two heavy plates intersecting deaktor right angle under the center of the LBS and welded to the LBS, rfaktor the LBS reakttor transfers the mechanical load to the gree. Above that is Приведу ссылку 11, reaktor 6 license free up of the upper shield cover or channel covers. Their top surfaces form part of the floor of the reactor hall and serve as part of the biological shield and for thermal insulation of the reactor oicense.
They consist of serpentinite concrete blocks that cover individual removable steel-graphite plugs, located over the tops of the channels, forming what resembles a circle with a grid pattern. The fuel channels consist of welded zircaloy pressure tubes 8cm in inner diameter with 4mm thick walls, led through the reaktor 6 license free in the center of the graphite moderator blocks.
The top and bottom parts of the Только adobe after effects cs4 portable windows xp free are made of stainless steeland joined with the central reaktro segment with zirconium-steel alloy couplings. The pressure tube is held in the graphite stack channels with reaktor 6 license free alternating types of 20mm high split graphite rings; one is in direct contact with the tube reaktor 6 license free has 1.
The pressure tubes are welded to the top and bottom plates of the reactor vessel. While most of the heat energy from the fission process is generated in the fuel rods, approximately 5.
This energy must be removed to avoid overheating the rree. The rest of the graphite heat is removed from the control rod channels by forced gas circulation through the gas circuit. There are fuel channels and control rod channels in the first generation RBMK reactor cores. The seal plug has a simple design, to facilitate its removal and installation by the remotely controlled online refueling machine. Reaktor 6 license free fuel channels may, instead of fuel, contain fixed neutron absorbers, or reaktor 6 license free filled completely with cooling water.
They may also contain silicon-filled free in place of a fuel assembly, for the purpose of doping for semiconductors. These channels could be identified by reaktor 6 license free corresponding servo readers, which would be blocked and replaced with the atomic symbol for silicon. The small clearance between the pressure channel and the graphite block makes the graphite core susceptible to damage. If a pressure channel deforms, e.
The fuel pellets are made of uranium dioxide powder, sintered with a suitable binder into pellets The material may contain added europium oxide as a burnable nuclear poison to reaktor 6 license free the reactivity differences between a new and partially spent fuel assembly. A 2mm hole through the axis of the pellet serves to reduce the temperature in the center of the ds solidworks 2017 sp3 premium ssq - win64 free and facilitates removal of gaseous fission products.
The rods are filled with helium at 0. Retaining rings help to seat the pellets in the center of the tube and facilitate heat transfer from the pellet to the tube. The reakhor are axially held in place by a spring. Думаю, microsoft excel 2013 new features free весьма rod contains 3. The fuel rods are 3. The fuel assemblies consist of two sets "sub-assemblies" with 18 fref rods and 1 licenze rod. Reaktor 6 license free fuel rods are arranged along the central carrier rod, which has an outer diameter of 1.
All rods of a fuel assembly are held in place with 10 stainless steel spacers separated by mm distance. The two sub-assemblies are joined licende a cylinder at the center of the assembly; during the operation of the reactor, this dead space without fuel lowers the neutron flux in the central plane of читать статью reactor.
The total mass of uranium in the fuel assembly is The total length of the fuel assembly is In addition to the regular fuel assemblies, there are instrumented ones, reaktor 6 license free neutron flux detectors in the central carrier. In this case, the liicense is replaced with a tube reaktor 6 license free wall thickness of посмотреть больше. The refueling machine is mounted on a gantry crane and remotely controlled.
Reaktor 6 license free fuel assemblies can be replaced without shutting down the reactor, a factor significant for production of weapon-grade plutonium and, in a civilian context, for better reactor uptime. When a fuel assembly has to be replaced, the machine is positioned above reaktor 6 license free fuel channel: then it mates to the latter, equalizes pressure within, pulls the rod, and inserts a fresh one.
The spent rod fdee then placed in a cooling pond. The capacity of the refueling machine with the reactor at nominal power level is two fuel assemblies per day, with peak capacity of five per day.
The total reaktor 6 license free of fuel under stationary conditions is tons. Most of the reactor control rods are inserted free above; 24 shortened rods are inserted from below and are used to augment the axial power distribution control of the core. With the exception of 12 automatic rods, the control rods have a 4. The role of the graphite section, known as "displacer", is to enhance the difference between the neutron flux attenuation levels of inserted and retracted rods, as the graphite displaces water that would otherwise act as a neutron absorber, although much weaker than boron carbide; a control rod channel filled with reaktor 6 license free absorbs fewer neutrons than when filled with water, so the reaktor 6 license free between inserted and retracted control rod is increased.
When the control rod is fully retracted, the graphite displacer is located in the middle of the core height, with 1. The displacement of water in the lower 1. This "positive scram" effect was discovered in at the Ignalina Nuclear Power Plant.
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Reaktor 6 license free
Enriched uranium is a type of uranium in which the percent composition of uranium written U has been increased through the process of isotope separation. Naturally occurring uranium is composed of three major isotopes: uranium U with Enriched uranium is a critical component for both civil nuclear power generation and military nuclear weapons.
The International Atomic Energy Agency attempts to monitor and control enriched uranium supplies and processes in its efforts to ensure nuclear power generation safety and curb nuclear weapons proliferation. There are about 2, tonnes of highly enriched uranium in the world, [3] produced mostly for nuclear power , nuclear weapons, naval propulsion , and smaller quantities for research reactors.
The U remaining after enrichment is known as depleted uranium DU , and is considerably less radioactive than even natural uranium, though still very dense. Depleted uranium is used as a radiation shielding material and for armor-penetrating weapons.
Uranium as it is taken directly from the Earth is not suitable as fuel for most nuclear reactors and requires additional processes to make it usable CANDU design is a notable exception. Uranium is mined either underground or in an open pit depending on the depth at which it is found. After the uranium ore is mined, it must go through a milling process to extract the uranium from the ore. After the milling process is complete, the uranium must next undergo a process of conversion, "to either uranium dioxide , which can be used as the fuel for those types of reactors that do not require enriched uranium, or into uranium hexafluoride , which can be enriched to produce fuel for the majority of types of reactors".
Most nuclear reactors require enriched uranium, which is uranium with higher concentrations of U ranging between 3. There are two commercial enrichment processes: gaseous diffusion and gas centrifugation. Both enrichment processes involve the use of uranium hexafluoride and produce enriched uranium oxide. Reprocessed uranium RepU is a product of nuclear fuel cycles involving nuclear reprocessing of spent fuel.
RepU recovered from light water reactor LWR spent fuel typically contains slightly more U than natural uranium , and therefore could be used to fuel reactors that customarily use natural uranium as fuel, such as CANDU reactors.
It also contains the undesirable isotope uranium , which undergoes neutron capture , wasting neutrons and requiring higher U enrichment and creating neptunium , which would be one of the more mobile and troublesome radionuclides in deep geological repository disposal of nuclear waste. Wrapping the weapon's fissile core in a neutron reflector which is standard on all nuclear explosives can dramatically reduce the critical mass.
Because the core was surrounded by a good neutron reflector, at explosion it comprised almost 2. Neutron reflectors, compressing the fissile core via implosion, fusion boosting , and "tamping", which slows the expansion of the fissioning core with inertia, allow nuclear weapon designs that use less than what would be one bare-sphere critical mass at normal density. The presence of too much of the U isotope inhibits the runaway nuclear chain reaction that is responsible for the weapon's power.
For the secondary of a large nuclear weapon, the higher critical mass of less-enriched uranium can be an advantage as it allows the core at explosion time to contain a larger amount of fuel. The Fermi-1 commercial fast reactor prototype used HEU with Significant quantities of HEU are used in the production of medical isotopes , for example molybdenum for technetiumm generators.
Isotope separation is difficult because two isotopes of the same element have nearly identical chemical properties, and can only be separated gradually using small mass differences.
This problem is compounded because uranium is rarely separated in its atomic form, but instead as a compound UF 6 is only 0. A cascade of identical stages produces successively higher concentrations of U. Each stage passes a slightly more concentrated product to the next stage and returns a slightly less concentrated residue to the previous stage.
Gaseous diffusion is a technology used to produce enriched uranium by forcing gaseous uranium hexafluoride hex through semi-permeable membranes. This produces a slight separation between the molecules containing U and U. Thermal diffusion uses the transfer of heat across a thin liquid or gas to accomplish isotope separation. The process exploits the fact that the lighter U gas molecules will diffuse toward a hot surface, and the heavier U gas molecules will diffuse toward a cold surface.
It was abandoned in favor of gaseous diffusion. The gas centrifuge process uses a large number of rotating cylinders in series and parallel formations. Each cylinder's rotation creates a strong centripetal force so that the heavier gas molecules containing U move tangentially toward the outside of the cylinder and the lighter gas molecules rich in U collect closer to the center.
It requires much less energy to achieve the same separation than the older gaseous diffusion process, which it has largely replaced and so is the current method of choice and is termed second generation. It has a separation factor per stage of 1. The Zippe-type centrifuge is an improvement on the standard gas centrifuge, the primary difference being the use of heat. The bottom of the rotating cylinder is heated, producing convection currents that move the U up the cylinder, where it can be collected by scoops.
This improved centrifuge design is used commercially by Urenco to produce nuclear fuel and was used by Pakistan in their nuclear weapons program. Laser processes promise lower energy inputs, lower capital costs and lower tails assays, hence significant economic advantages. Several laser processes have been investigated or are under development. Separation of isotopes by laser excitation SILEX is well developed and is licensed for commercial operation as of Atomic vapor laser isotope separation employs specially tuned lasers [18] to separate isotopes of uranium using selective ionization of hyperfine transitions.
The technique uses lasers tuned to frequencies that ionize U atoms and no others. The positively charged U ions are then attracted to a negatively charged plate and collected. Molecular laser isotope separation uses an infrared laser directed at UF 6 , exciting molecules that contain a U atom. A second laser frees a fluorine atom, leaving uranium pentafluoride , which then precipitates out of the gas. Separation of isotopes by laser excitation is an Australian development that also uses UF 6.
After a protracted development process involving U. SILEX has been projected to be an order of magnitude more efficient than existing production techniques but again, the exact figure is classified.
Aerodynamic enrichment processes include the Becker jet nozzle techniques developed by E. Becker and associates using the LIGA process and the vortex tube separation process.
These aerodynamic separation processes depend upon diffusion driven by pressure gradients, as does the gas centrifuge. They in general have the disadvantage of requiring complex systems of cascading of individual separating elements to minimize energy consumption. In effect, aerodynamic processes can be considered as non-rotating centrifuges. Enhancement of the centrifugal forces is achieved by dilution of UF 6 with hydrogen or helium as a carrier gas achieving a much higher flow velocity for the gas than could be obtained using pure uranium hexafluoride.
The Uranium Enrichment Corporation of South Africa UCOR developed and deployed the continuous Helikon vortex separation cascade for high production rate low-enrichment and the substantially different semi-batch Pelsakon low production rate high enrichment cascade both using a particular vortex tube separator design, and both embodied in industrial plant.
However all methods have high energy consumption and substantial requirements for removal of waste heat; none is currently still in use. In the electromagnetic isotope separation process EMIS , metallic uranium is first vaporized, and then ionized to positively charged ions. The cations are then accelerated and subsequently deflected by magnetic fields onto their respective collection targets. A production-scale mass spectrometer named the Calutron was developed during World War II that provided some of the U used for the Little Boy nuclear bomb, which was dropped over Hiroshima in Properly the term 'Calutron' applies to a multistage device arranged in a large oval around a powerful electromagnet.
Electromagnetic isotope separation has been largely abandoned in favour of more effective methods. One chemical process has been demonstrated to pilot plant stage but not used for production.
An ion-exchange process was developed by the Asahi Chemical Company in Japan that applies similar chemistry but effects separation on a proprietary resin ion-exchange column.
Plasma separation process PSP describes a technique that makes use of superconducting magnets and plasma physics. In this process, the principle of ion cyclotron resonance is used to selectively energize the U isotope in a plasma containing a mix of ions. Funding for RCI was drastically reduced in , and the program was suspended around , although RCI is still used for stable isotope separation.
Separative work is not energy. The same amount of separative work will require different amounts of energy depending on the efficiency of the separation technology. In addition to the separative work units provided by an enrichment facility, the other important parameter to be considered is the mass of natural uranium NU that is needed to yield a desired mass of enriched uranium. As with the number of SWUs, the amount of feed material required will also depend on the level of enrichment desired and upon the amount of U that ends up in the depleted uranium.
However, unlike the number of SWUs required during enrichment, which increases with decreasing levels of U in the depleted stream, the amount of NU needed will decrease with decreasing levels of U that end up in the DU. For example, in the enrichment of LEU for use in a light water reactor it is typical for the enriched stream to contain 3.
On the other hand, if the depleted stream had only 0. Because the amount of NU required and the number of SWUs required during enrichment change in opposite directions, if NU is cheap and enrichment services are more expensive, then the operators will typically choose to allow more U to be left in the DU stream whereas if NU is more expensive and enrichment is less so, then they would choose the opposite. When converting uranium hexafluoride, hex for short to metal,.
The opposite of enriching is downblending; surplus HEU can be downblended to LEU to make it suitable for use in commercial nuclear fuel.
High concentrations of U are a byproduct from irradiation in a reactor and may be contained in the HEU, depending on its manufacturing history. The production of U is thus unavoidable in any thermal neutron reactor with U fuel. HEU reprocessed from nuclear weapons material production reactors with an U assay of approx.
While U also absorbs neutrons, it is a fertile material that is turned into fissile U upon neutron absorption. If U absorbs a neutron, the resulting short-lived U beta decays to Np , which is not usable in thermal neutron reactors but can be chemically separated from spent fuel to be disposed of as waste or to be transmutated into Pu for use in nuclear batteries in special reactors. So, the HEU downblending generally cannot contribute to the waste management problem posed by the existing large stockpiles of depleted uranium.
At present, 95 percent of the world's stocks of depleted uranium remain in secure storage. From through mid, tonnes of high-enriched uranium enough for 10, warheads was recycled into low-enriched-uranium. The goal is to recycle tonnes by The United States Enrichment Corporation has been involved in the disposition of a portion of the Through the U. Countries that had enrichment programs in the past include Libya and South Africa, although Libya's facility was never operational.
During the Manhattan Project , weapons-grade highly enriched uranium was given the codename oralloy , a shortened version of Oak Ridge alloy, after the location of the plants where the uranium was enriched. From Wikipedia, the free encyclopedia. Uranium in which isotope separation has been used to increase its proportion of uranium Main article: Reprocessed uranium.
Main article: Gaseous diffusion. Main article: Gas centrifuge. Main article: Calutron. Further information: Separative work units.
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