There are many natural sources of radiation that we live with safely every day such as cosmic radiation from the sun. It is not possible for a nuclear energy plant to explode like a bomb, these plants are designed to produce electricity safely and reliably. If you stood at the site boundary for a whole year, you would receive less than a quarter of the radiation from a chest x-ray. Who Operates the Plant? What is nuclear energy? How does it work? Nuclear reactor creates heat that is used to make steam The steam turns a turbine connected to an electromagnet, called a generator The generator produces electricity In a Pressurized Water Reactor PWR — the type of reactor being built in the UAE — high pressure prevents water in the reactor vessel from boiling.
Uranium Enriched uranium is the fuel for nuclear reactors. Nuclear Fission Fission is the process of splitting a nucleus in two. Worldwide facts For more than 60 years, nuclear energy has provided the world with reliable electricity. Other Uses of Nuclear Technology. The moderator helps slow down the neutrons produced by fission to sustain the chain reaction. Control rods can then be inserted into the reactor core to reduce the reaction rate or withdrawn to increase it.
The heat created by fission turns the water into steam, which spins a turbine to produce carbon-free electricity. All commercial nuclear reactors in the United States are light-water reactors. This means they use normal water as both a coolant and neutron moderator. These reactors pump water into the reactor core under high pressure to prevent the water from boiling.
The water in the core is heated by nuclear fission and then pumped into tubes inside a heat exchanger. Those tubes heat a separate water source to create steam.
Nuclear reactors are, fundamentally, large kettles, which are used to heat water to produce enormous amounts of low-carbon electricity. They come in different sizes and shapes, and can be powered by a variety of different fuels. Some of the neutrons that are released then hit other atoms, causing them to fission too and release more neutrons. This is called a chain reaction.
The fissioning of atoms in the chain reaction also releases a large amount of energy as heat. The generated heat is removed from the reactor by a circulating fluid, typically water.
This heat can then be used to generate steam, which drives turbines for electricity production. In order to ensure the nuclear reaction takes place at the right speed, reactors have systems that accelerate, slow or shut down the nuclear reaction, and the heat it produces.
In both, about kg of zircaloy is involved. It is therefore subject to controls on trading. A significant industry initiative is to develop accident-tolerant fuels which are more resistant to melting under conditions such as those in the Fukushima accident, and with the cladding being more resistant to oxidation with hydrogen formation at very high temperatures under such conditions. Burnable poisons are often used in fuel or coolant to even out the performance of the reactor over time from fresh fuel being loaded to refuelling.
The best known is gadolinium, which is a vital ingredient of fuel in naval reactors where installing fresh fuel is very inconvenient, so reactors are designed to run more than a decade between refuellings full power equivalent — in practice they are not run continuously.
Gadolinium is incorporated in the ceramic fuel pellets. An alternative is zirconium diboride integral fuel burnable absorber IFBA as a thin coating on normal pellets. It is now used in most US reactors and a few in Asia. China has the technology for AP reactors. This is the most common type, with about operable reactors for power generation and several hundred more employed for naval propulsion. The design of PWRs originated as a submarine power plant.
PWRs use ordinary water as both coolant and moderator. The design is distinguished by having a primary cooling circuit which flows through the core of the reactor under very high pressure, and a secondary circuit in which steam is generated to drive the turbine.
A PWR has fuel assemblies of rods each, arranged vertically in the core, and a large reactor would have about fuel assemblies with tonnes of uranium. Pressure is maintained by steam in a pressuriser see diagram. In the primary cooling circuit the water is also the moderator, and if any of it turned to steam the fission reaction would slow down.
This negative feedback effect is one of the safety features of the type. The secondary shutdown system involves adding boron to the primary circuit. The secondary circuit is under less pressure and the water here boils in the heat exchangers which are thus steam generators. The steam drives the turbine to produce electricity, and is then condensed and returned to the heat exchangers in contact with the primary circuit.
The steam passes through drier plates steam separators above the core and then directly to the turbines, which are thus part of the reactor circuit. Since the water around the core of a reactor is always contaminated with traces of radionuclides, it means that the turbine must be shielded and radiological protection provided during maintenance. The cost of this tends to balance the savings due to the simpler design. A BWR fuel assembly comprises fuel rods, and there are up to assemblies in a reactor core, holding up to tonnes of uranium.
The secondary control system involves restricting water flow through the core so that more steam in the top part reduces moderation. PHWRs generally use natural uranium 0. As in the PWR, the primary coolant generates steam in a secondary circuit to drive the turbines.
The pressure tube design means that the reactor can be refuelled progressively without shutting down, by isolating individual pressure tubes from the cooling circuit. It is also less costly to build than designs with a large pressure vessel, but the tubes have not proved as durable.
A CANDU fuel assembly consists of a bundle of 37 half metre long fuel rods ceramic fuel pellets in zircaloy tubes plus a support structure, with 12 bundles lying end to end in a fuel channel.
Control rods penetrate the calandria vertically, and a secondary shutdown system involves adding gadolinium to the moderator. The heavy water moderator circulating through the body of the calandria vessel also yields some heat though this circuit is not shown on the diagram above.
CANDU reactors can accept a variety of fuels. They may be run on recycled uranium from reprocessing LWR used fuel, or a blend of this and depleted uranium left over from enrichment plants. Thorium may also be used in fuel. These are the second generation of British gas-cooled reactors, using graphite moderator and carbon dioxide as primary coolant.
The fuel is uranium oxide pellets, enriched to 2. Control rods penetrate the moderator and a secondary shutdown system involves injecting nitrogen to the coolant. Refuelling can be on-load. The AGR was developed from the Magnox reactor. Magnox reactors were also graphite moderated and CO 2 cooled, used natural uranium fuel in metal form, and water as secondary coolant. The UK's last Magnox reactor closed at the end of Fuel is low-enriched uranium oxide made up into fuel assemblies 3.
With moderation largely due to the fixed graphite, excess boiling simply reduces the cooling and neutron absorbtion without inhibiting the fission reaction, and a positive feedback problem can arise, which is why they have never been built outside the Soviet Union.
Some reactors do not have a moderator and utilise fast neutrons, generating power from plutonium while making more of it from the U isotope in or around the fuel.
While they get more than 60 times as much energy from the original uranium compared with normal reactors, they are expensive to build. Further development of them is likely in the next decade, and the main designs expected to be built in two decades are FNRs. If they are configured to produce more fissile material plutonium than they consume they are called fast breeder reactors FBR.
For reactors under construction, see information page on Plans for New Reactors Worldwide. Several generations of reactors are commonly distinguished. Generation I reactors were developed in the s and the last one Wylfa 1 in the UK shut down at the end of They mostly used natural uranium fuel and used graphite as moderator. Generation II reactors are typified by the present US fleet and most in operation elsewhere.
They typically use enriched uranium fuel and are mostly cooled and moderated by water. Others are under construction and ready to be ordered.
They are developments of the second generation with enhanced safety. Generation IV designs are still on the drawing board. They will tend to have closed fuel cycles and burn the long-lived actinides now forming part of spent fuel, so that fission products are the only high-level waste.
Of seven designs under development with international collaboration, four or five will be fast neutron reactors. Four will use fluoride or liquid metal coolants, hence operate at low pressure. Two will be gas-cooled.
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