Nuclear Reactor
In it's most simplest form, a nuclear reactor uses UraniumUraniumNatural Uranium VS \#stub and other radioactive materials and the fission from uranium to create heat, and transfer that heat into steam to create power. Nuclear reactors are one of the biggest sources of energy, although not renewable, uranium has a very high energy density resulting in massive power transmissions.
There are many different types of nuclear reactors, and this term serves as a broad hub/introduction for each type.
After uranium is used in reactors, it is termed Spent Nuclear FuelSpent Nuclear FuelSpent nuclear fuel is literally just fuel that has been burnt or irradiated at a plant. According to Wikipedia, "a fresh rod of low enriched Uranium pellets will become a highly lethal gamma emitter after 1-2 years of core irradiation, unsafe to approach unless under many feet of water shielding." Properties of Spent Fuel During the operation of a nuclear core, temperature gradients cause fission products to move around the fuel rod. The zirconium moves toward the center where temperature is h. In many Thermal ReactorThermal Reactors, this spent fuel is stored in Spent Fuel PoolAir Traffic Control\#emptys, and it can later go under reprocessing.
Thermal Reactors
Thermal reactors are reactors specifically designed to be energy producing - neutrons are given from uranium rods of varying enrichment, and Light WaterLight WaterLight water, although appearing to have a fancy name, is literally just ordinary water....except it does contain a small amount of Heavy Water. The point of light water is that it can be used as a moderator --however it can only be used in certain situations, as it absorbs too many neutrons to be used with unenriched uranium (which is why light water is presumably used in Spent Fuel Pools) Light water is mainly used in BWR reactors & PWR reactors Uranium Enrichment is necessary for the usage of is generally used as a coolant and moderator which allows fission to occur, generating heat and therefore power.
Pressurized Water Reactor
A PWR reactorPWR reactorThis reactor is a PWR reactor - a pressurized water reactor. This is a specific type of Nuclear Reactor--in that it is pressurized water. This is also the most common type of reactor used and produced. The fuel rods are pressurized with helium, and the fission gas products result in more stability; as fuel "burns" in the reactor, the density increases resulting in small voids developing. Helium pressurization is necessary as these voids can cause potential rupture of fuel rods. Furthermore, the is the most common type of reactor. The water in this type of reactor is pressurized, so that water can be used as coolant; the boiling point of water increases as it's pressure increases. In this type, there are two loops of water: hot water flowing through the RPVRPVReactor Pressure Vessel - contains all of the reactor heat. In BWR reactors, the RPV contains the reactor core - basically the entirety of the main reactor assembly. The RPV is designed to withstand a very large amount of force considering that in a BWR it must withstand the pressure that both it operates at and at emergency designs -- this is due to the fact that in most designs, the RPV isn't considered to be at major risk: even during a major LOCA the RPV is considered to be at healthy condi and the water that turns into steam and spins the turbine; this water meets the RPV water through a heat exchanger. Since water remains a liquid throughout operation, control rods can be placed at the top, allowing for maximum safety during plant transients.
European Pressurized Reactor
The EPR ReactorEPR ReactorA PWR reactor design, it is designed by Framatone, and the name is the European Pressurized reactor. The design service lifetime is 60 years. (This is mostly paraphrased from wikipedia :3) The main objectives is to be more economically competitive and still deliver power. It was designed to use uranium more efficiently then gen2 reactors, as it is a gen3 - and it uses "approximately 17% less uranium per kWh generated". The EPR design has several active and passive protection measures against is a PWR-type reactor designed by FramatoneFramatoneFramatone is a French nuclear reactor business, majority owned by France electric. It first formed to license PWR reactor designs, and then went on to produce more nuclear reactor based products. Originally licensing and construction, it supplies the entire reactor life cycle, including the design of the EPR Reactor & other tasks. (See Also: Hydrogen Recombiners - Framatone built the leading hydrogen recombiner), designed to be more economically competitive.
VVER Reactor
The VVER Reactor (WWER)VVER Reactor (WWER)Water-Water energetic reactor (WWER) or the Russian VVER from (from Russian: водо-водяной энергетический реактор, romanized: vodo-vodyanoi enyergeticheskiy reaktor, lit. 'water-water power reactor') is a series of PWR reactor designs developed originally by the Soviet Union, and now Russia, by OKB Gidropress. One of the initial reactor designs other then the RBMK Reactor, this design is a Thermal Reactor design using control rods and Light Water coolant. Their power varies, with electric power is a Soviet Union designed reactor, of the PWR type. The distinguishing factor for this reactor is that it has horizontal steam generation and hexagonal fuel assemblies.
Boiling Water Reactor
A BWR reactorBWR reactorA boiling water reactor uses Light Water as both coolant and neutron moderator. The second most used reactor, next to the PWR reactors, there are approximately 75 plants in current operation. The efficiency of these reactors is about 46%, with 33-34% in practice. Enriched uranium is used as nuclear fuel, as light water absorbs too many neutrons to use Uranium that is natural. Light water is not as good of a moderator compared to Heavy Water or graphite, but it is good as in the event of a LOCA o is the second most common type of reactor. In this reactor, water directly goes throughout the plant as it heats into steam, that is used to spin turbines for electricity. Since water stays throughout the plant in one coolant loop, control rods are placed at the bottom - as steam goes into the top of the RPV. Control rods placement at the top requires a specialized Control Rod DriveControl Rod DriveThe CRD system in a Nuclear Reactor is crucial for its operation. The CRD is necessary for the percise control of Control Rods in a reactor. In BWR reactors, this is especially necessary, as control rods are inserted via the bottom penetration points in the RPV, and if there is a SCRAM, gravity cannot be relied on to insert the rods, differing from other reactor designs. Therefore, a method to SCRAM the plant and percisely control the rods in a BWR is necessary. BWR Control Rod Drive Mechanisms system to be used. This is because gravity cannot help in a scram: some type of power is necessary to move the reactors rods in both positioning and emergency events.
An interesting side note is that since there is only one coolant loop, radioactive water is present everywhere in the plant, meaning that if the turbines or any other place experience a leak, it is almost certainly the release of radioactive water. (Excluding some subsystems present in every plant)
Fast Neutron Reactors
Fast Neutron ReactorFast Neutron ReactorA Fast Neutron Reactor is a specific type of reactor that different from a Thermal Reactor-- it is not very common because unlike a thermal reactor that uses neutron to sustain the chain reaction, a FNR has no neutron moderation and less primary coolant due to an excess of fast neutrons * the capture to fission ratio is lower is fast reactors * high number of neutron produced per one fission * Neutron Flux has differences too The following image shows the neutron flux differences 400 Neutron Fs have an excess of neutrons, requiring an higher enrichment of uranium. In this type, water is not used as a moderator and different types of coolants can be used. This type is not very common, however.
Fuel
Reactors use fuel1. Specifically, UraniumUraniumNatural Uranium VS \#stub is used. (in most cases). After multiple rounds of fission has occurred, uranium reaches its end of life. This is either by it being unable to sustain a proficient enough nuclear reaction to generate heat, or that it is simply too depleted or other reasons. In this case, it is now referred to as Spent Nuclear FuelSpent Nuclear FuelSpent nuclear fuel is literally just fuel that has been burnt or irradiated at a plant. According to Wikipedia, "a fresh rod of low enriched Uranium pellets will become a highly lethal gamma emitter after 1-2 years of core irradiation, unsafe to approach unless under many feet of water shielding." Properties of Spent Fuel During the operation of a nuclear core, temperature gradients cause fission products to move around the fuel rod. The zirconium moves toward the center where temperature is h, and is often stored in a Spent Fuel PoolAir Traffic Control\#empty before eventually being stored in dry casks or other Nuclear Waste Disposal Methods.
Fuel is contained inside of Fuel RodsFuel RodsThis is a breakdown of how Fuel Rods work, for information on nuclear fuel itself, you want Nuclear Fuel. Fuel rods are made out of the fissile material that is wanted for the reactor, then experience different things. Uranium Dioxide fuel is pelleted and filled into metallic tubes, which have cladding of Zirconium or stainless steel, and then these tubes are sealed. In a PWR reactor, fuel is cylindrical rods into bundles, where fuel is bundled and the cladding gap filled with helium to help w, which contain ZirconiumZirconiumZirconium is a metal used in reactor cladding Zirconium has excellent heat transfer properties and allows for efficient heat transfer. However, it has a negative reaction called Zircaloy hydriding, where zirconium and hydrogen combine for form zirconium hydride, embrittling reactor cladding and resulting in perforations. claddingCladdingCladding is the thin walled metal tube that composes the outside of a fuel rod. It's purpose is to prevent corrosion of the fuel by the coolant & release of fission contents into the coolant. Although Zirconium alloy is common, aluminum and stainless steel is also used. Cladding Types Zirconium alloy has been used for so long due to it's properties being very good for nuclear reactors. * New research suggests that there is an alternative - SiGA cladding. This cladding is made from silicon car, which provides a major benefit to the thermal efficency of these rods.
For a sustained reaction, control methods are needed. In this case, Control RodsControl RodsControl Rods are rods that are used to control the rate of reaction inside and within a Nuclear Reactor. They have a specific design that allows for this control. BWR reactor parameters In the GE Marathon control rod, it contains stainless steel tubes filled with boron carbide poison. This isotope contains a high cross-section for the absorption of neutrons, acting as a control rod neutron poison. These control rods are uniformly placed into a reactor core according to its design parameters. are used, using a Control Rod DriveControl Rod DriveThe CRD system in a Nuclear Reactor is crucial for its operation. The CRD is necessary for the percise control of Control Rods in a reactor. In BWR reactors, this is especially necessary, as control rods are inserted via the bottom penetration points in the RPV, and if there is a SCRAM, gravity cannot be relied on to insert the rods, differing from other reactor designs. Therefore, a method to SCRAM the plant and percisely control the rods in a BWR is necessary. BWR Control Rod Drive Mechanisms subsystem. In BWR reactors, control rods are fed through bottom penetrations in the Reactor Pressure VesselRPVReactor Pressure Vessel - contains all of the reactor heat. In BWR reactors, the RPV contains the reactor core - basically the entirety of the main reactor assembly. The RPV is designed to withstand a very large amount of force considering that in a BWR it must withstand the pressure that both it operates at and at emergency designs -- this is due to the fact that in most designs, the RPV isn't considered to be at major risk: even during a major LOCA the RPV is considered to be at healthy condi, and as such, require other equipment, unlike PWRs and other such reactors where gravity can be used as an assist mechanism.
Cooling
Reactors need cooling2. Primary cooling is usually the same way that we extract power, cycling water through the reactor core, then heat exchangers to extract the heat in the case of a PWR or directly use steam from the core in a BWR, and then a condenser to return the steam into water that can be heated again. These cooling methods are generally enough to manage the cooling the reactor needs. If the reactor experiences an emergency, Emergency Core Cooling SystemsECCSEmergency Core Cooling Systems encompass all of the emergency systems used in Nuclear Reactors. Inside of the RPV of a reactor is the reactor core, which gets hot due to fission during operation. In the event that primary cooling systems go offline due to a powerloss, LOCA, or other reason, ECCS systems are automatically enabled. ECCS broadly describes all of the emergency systems used, however specific emergency systems can be used in isolation. Some ECCS systems are specified for a specific d can be utilized to ensure safety.