A nuclear reactor, formerly known as an atomic pile, is a device used to initiate and control a self-sustained nuclear chain reaction. Nuclear reactors are used at nuclear power Plants for electricity generation and in propulsion of ships. Heat from nuclear fission is passed to a working fluid (water or gas), which in turn runs through steam turbines. These either drive a ship’s propellers or turn electrical generators’ shafts. Nuclear generated steam in principle can be used for industrial process heat or for district heating. Some reactors are used to produce isotopes for medical and industrial use, or for production of weapons-grade plutonium. Some are run only for research. As of April 2014, the IAEA reports there are 435 nuclear power reactors in operation, in 31 countries around the world. By 2017, this increased to 447 operable reactors according to the World Nuclear Association.
Main components
The core of the reactor contains all of the nuclear fuel and generates all of the heat. It contains low-enriched uranium (<5% U-235), control systems, and structural materials. The core can contain hundreds of thousands of individual fuel pins.
The coolant is the material that passes through the core, transferring the heat from the fuel to a turbine. It could be water, heavy-water, liquid sodium, helium, or something else. In the US fleet of power reactors, water is the standard.
The turbine transfers the heat from the coolant to electricity, just like in a fossil-fuel plant.
The containment is the structure that separates the reactor from the Environment. These are usually dome-shaped, made of high-density, steel-reinforced concrete. Chernobyl did not have a containment to speak of.
Cooling towers are needed by some plants to dump the excess heat that cannot be converted to energy due to the laws of Thermodynamics. These are the hyperbolic icons of Nuclear Energy. They emit only clean water vapor.
Types of Reactors
There are many different kinds of nuclear fuel forms and cooling materials can be used in a nuclear reactor. As a result, there are thousands of different possible nuclear reactor designs.
Pressurized Water Reactor The most common type of reactor. The PWR uses regular old water as a coolant. The primary cooling water is kept at very high pressure so it does not boil. It goes through a heat exchanger, transferring heat to a secondary coolant loop, which then spins the turbine. These use oxide fuel pellets stacked in zirconium tubes. They could possibly burn thorium or plutonium fuel as well.
The Pros of having pressurized water reactor are as follows:
- Strong negative void coefficient — reactor cools down if water starts bubbling because the coolant is the moderator, which is required to sustain the chain reaction.
- Secondary loop keeps radioactive stuff away from turbines, making maintenance easy.
- Very much operating experience has been accumulated and the designs and procedures have been largely optimized.
Boiling Water Reactor Second most common, the BWR is similar to the PWR in many ways. However, they only have one coolant loop. The hot nuclear fuel boils water as it goes out the top of the reactor, where the steam heads over to the turbine to spin it.
The pros of boiling water reactor are as follows:
- Simpler plumbing reduces costs
- Power levels can be increased simply by speeding up the jet pumps, giving less boiled water and more moderation. Thus, load-following is simple and easy.
- Very much operating experience has been accumulated and the designs and procedures have been largely optimized.
Nuclear fuel cycle
Thermal reactors generally depend on refined and enriched uranium. Some nuclear reactors can operate with a mixture of plutonium and uranium. The process by which uranium Ore is mined, processed, enriched, used, possibly reprocessed and disposed of is known as the nuclear fuel cycle.
Under 1% of the uranium found in nature is the easily fissionable U-235 isotope and as a result most reactor designs require enriched fuel. Enrichment involves increasing the Percentage of U-235 and is usually done by means of gaseous diffusion or gas centrifuge. The enriched result is then converted into uranium dioxide powder, which is pressed and fired into pellet form. These pellets are stacked into tubes which are then sealed and called fuel rods. Many of these fuel rods are used in each nuclear reactor.
Most BWR and PWR commercial reactors use uranium enriched to about 4% U-235, and some commercial reactors with a high neutron economy do not require the fuel to be enriched at all (that is, they can use natural uranium). According to the International Atomic Energy Agency there are at least 100 research reactors in the world fueled by highly enriched (weapons-grade/90% enrichment uranium). Theft risk of this fuel (potentially used in the production of a nuclear weapon) has led to campaigns advocating conversion of this type of reactor to low-enrichment uranium (which poses less threat of proliferation).
Fissile U-235 and non-fissile but fissionable and fertile U-238 are both used in the fission process. U-235 is fissionable by thermal (i.e. slow-moving) neutrons. A thermal neutron is one which is moving about the same speed as the atoms around it. Since all atoms vibrate proportionally to their absolute temperature, a thermal neutron has the best opportunity to fission U-235 when it is moving at this same vibrational speed. On the other hand, U-238 is more likely to capture a neutron when the neutron is moving very fast. This U-239 atom will soon decay into plutonium-239, which is another fuel. Pu-239 is a viable fuel and must be accounted for even when a highly enriched uranium fuel is used. Plutonium fissions will dominate the U-235 fissions in some reactors, especially after the initial loading of U-235 is spent. Plutonium is fissionable with both fast and thermal neutrons, which make it ideal for either nuclear reactors or nuclear bombs.
Most reactor designs in existence are thermal reactors and typically use water as a neutron moderator (moderator means that it slows down the neutron to a thermal speed) and as a coolant. But in a fast breeder reactor, some other kind of coolant is used which will not moderate or slow the neutrons down much. This enables fast neutrons to dominate, which can effectively be used to constantly replenish the fuel supply. By merely placing cheap unenriched uranium into such a core, the non-fissionable U-238 will be turned into Pu-239, “breeding” fuel.
In thorium fuel cycle thorium-232 absorbs a neutron in either a fast or thermal reactor. The thorium-233 beta decays to protactinium-233 and then to uranium-233, which in turn is used as fuel. Hence, like uranium-238, thorium-232 is a fertile material.
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Nuclear reactors are used to generate electricity by converting heat into steam. The steam then drives a turbine, which generates electricity. There are many different types of nuclear reactors, but they all work on the same basic principle.
The most common type of nuclear reactor is the pressurized water reactor (PWR). In a PWR, water is heated under high pressure to produce steam. The steam then drives a turbine, which generates electricity. The steam is then condensed back into water and returned to the reactor.
Another common type of nuclear reactor is the boiling water reactor (BWR). In a BWR, water is heated under high pressure to produce steam. The steam then drives a turbine, which generates electricity. The steam is then released into the Atmosphere.
Heavy water reactors (HWRs) use heavy water, or D2O, as a coolant. Heavy water is a form of water that contains deuterium, a heavier isotope of hydrogen. HWRs are used in Canada and India.
Pressurized heavy water reactors (PHWRs) are a type of HWR. In a PHWR, heavy water is heated under high pressure to produce steam. The steam then drives a turbine, which generates electricity. The steam is then condensed back into water and returned to the reactor.
Gas-cooled reactors (GCRs) use gas, such as carbon dioxide or helium, as a coolant. GCRs are used in the United Kingdom and France.
Fast neutron reactors (FNRs) use fast neutrons to generate electricity. Fast neutrons are neutrons that have not been slowed down by collisions with atoms. FNRs are still under development, but they have the potential to be more efficient than other types of nuclear reactors.
Molten salt reactors (MSRs) use molten salt as a coolant. Molten salt is a mixture of salts that are melted at high temperatures. MSRs are still under development, but they have the potential to be more efficient and safer than other types of nuclear reactors.
Liquid Metal fast reactors (LMFRs) use liquid metal, such as sodium or lead, as a coolant. LMFRs are still under development, but they have the potential to be more efficient and safer than other types of nuclear reactors.
Sodium-cooled fast reactors (SFRs) are a type of LMFR. In an SFR, sodium is heated under high pressure to produce steam. The steam then drives a turbine, which generates electricity. The steam is then condensed back into water and returned to the reactor.
Lead-cooled fast reactors (LFRs) are a type of LMFR. In an LFR, lead is heated under high pressure to produce steam. The steam then drives a turbine, which generates electricity. The steam is then condensed back into water and returned to the reactor.
Thorium-fueled reactors (LFRs) are a type of LFR. In a thorium-fueled reactor, thorium is used as the fuel. Thorium is a more abundant and less radioactive than uranium. Thorium-fueled reactors are still under development, but they have the potential to be more efficient and safer than other types of nuclear reactors.
Pebble bed reactors (PBRs) are a type of reactor that uses pebbles as fuel. The pebbles are made of a ceramic material that contains uranium or thorium. PBRs are still under development, but they have the potential to be more efficient and safer than other types of nuclear reactors.
Advanced gas-cooled reactors (AGRs) are a type of GCR. In an AGR, carbon dioxide is heated under high pressure to produce steam. The steam then drives a turbine, which generates electricity. The steam is then condensed back into water and returned to the reactor.
Supercritical water-cooled reactors (SCWRs) are a type of PWR. In an SCWR, water is heated under supercritical pressure to produce steam. Supercritical pressure is a pressure that is greater than the critical pressure of water. SCWRs are still under development, but they have the potential to be more efficient and safer than other types of nuclear reactors.
Very high temperature reactors (VHTRs) are a type of reactor that operates at very high temperatures. VHTRs are still under development, but they have the potential to be more efficient and safer than other types of nuclear reactors.
Nuclear fusion reactors are a type of reactor that produces energy by fusing atoms together. Nuclear fusion is a process that releases a large amount of energy. Nuclear fusion reactors are still under development, but they have the potential to be a clean and safe Source Of Energy.
Nuclear reactors are a controversial topic. Some people believe that nuclear reactors are a safe and efficient way to generate electricity. Others believe that nuclear reactors are a dangerous technology that should not be used.
What is a nuclear reactor?
A nuclear reactor is a device that uses nuclear fission to generate heat. This heat can be used to generate electricity, or to propel ships.
How does a nuclear reactor work?
A nuclear reactor contains a fuel rod, which is made of a material that can be split by neutrons. When a neutron hits a uranium-235 atom, it splits the atom into two smaller atoms and releases two or three more neutrons. These neutrons then hit other uranium-235 atoms, causing them to split as well. This process is called a chain reaction.
The chain reaction is controlled by a moderator, which slows down the neutrons. This prevents the chain reaction from getting out of control. The heat produced by the chain reaction is used to boil water, which turns a turbine that generates electricity.
What are the different types of nuclear reactors?
There are four main types of nuclear reactors: Light water reactors, heavy water reactors, gas-cooled reactors, and molten salt reactors.
Light water reactors are the most common type of nuclear reactor. They use ordinary water as both a coolant and a moderator.
Heavy water reactors use heavy water, which is water that contains deuterium instead of hydrogen. Deuterium is a heavier isotope of hydrogen. Heavy water reactors are more efficient than light water reactors, but they are also more expensive to build.
Gas-cooled reactors use a gas, such as helium or carbon dioxide, as a coolant. Gas-cooled reactors are more efficient than light water reactors, but they are also more expensive to build.
Molten salt reactors use a molten salt as a coolant. Molten salt reactors are very efficient, but they are also very complex and expensive to build.
What are the advantages and disadvantages of nuclear power?
The advantages of nuclear power include:
- It is a reliable source of electricity.
- It does not produce greenhouse gases.
- It is a relatively safe form of energy.
The disadvantages of nuclear power include:
- The waste produced by nuclear power is radioactive and must be carefully disposed of.
- Nuclear power plants are expensive to build and operate.
- There is a risk of accidents at nuclear power plants.
What is the future of nuclear power?
The future of nuclear power is uncertain. Some people believe that nuclear power is a safe and reliable form of energy that should be used to reduce our reliance on fossil fuels. Others believe that nuclear power is too dangerous and that we should focus on developing RENEWABLE ENERGY sources.
The decision of whether or not to use nuclear power is a complex one that must be made on a case-by-case basis.
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Which of the following is not a type of nuclear reactor?
(A) Pressurized water reactor (PWR)
(B) Boiling water reactor (BWR)
(C) Gas-cooled reactor (GCR)
(D) Fast breeder reactor (FBR) -
Which of the following is the most common type of nuclear reactor in the world?
(A) PWR
(B) BWR
(C) GCR
(D) FBR -
In a PWR, the water that cools the reactor is:
(A) Under high pressure
(B) Under low pressure
(C) Not under pressure -
In a BWR, the water that cools the reactor is:
(A) Under high pressure
(B) Under low pressure
(C) Not under pressure -
In a GCR, the coolant is:
(A) Water
(B) Helium
(C) Carbon dioxide -
In a FBR, the fuel is:
(A) Uranium-235
(B) Plutonium-239
(C) Thorium-232 -
The main advantage of a PWR is that it:
(A) Is very efficient
(B) Is very safe
(C) Is very easy to operate -
The main advantage of a BWR is that it:
(A) Is very efficient
(B) Is very safe
(C) Is very easy to operate -
The main advantage of a GCR is that it:
(A) Is very efficient
(B) Is very safe
(C) Is very easy to operate -
The main advantage of a FBR is that it:
(A) Can produce more fuel than it consumes
(B) Is very efficient
(C) Is very safe -
The main disadvantage of a PWR is that it:
(A) Produces a lot of waste heat
(B) Is very expensive to build
(C) Is very complex to operate -
The main disadvantage of a BWR is that it:
(A) Produces a lot of waste heat
(B) Is very expensive to build
(C) Is very complex to operate -
The main disadvantage of a GCR is that:
(A) It is not very efficient
(B) It is not very safe
(C) It is not very easy to operate -
The main disadvantage of a FBR is that:
(A) It is not very efficient
(B) It is not very safe
(C) It is not very easy to operate -
Nuclear power is a controversial issue because:
(A) It produces radioactive waste
(B) It can be used to make nuclear weapons
(C) It is a very expensive form of energy -
The main reason why nuclear power is controversial is because:
(A) It produces radioactive waste
(B) It can be used to make nuclear weapons
(C) It is a very expensive form of energy -
The main argument in favor of nuclear power is that:
(A) It is a clean form of energy
(B) It is a reliable form of energy
(C) It is a safe form of energy -
The main argument against nuclear power is that:
(A) It produces radioactive waste
(B) It can be used to make nuclear weapons
(C) It is a very expensive form of energy -
The future of nuclear power is uncertain because:
(A) The public is concerned about the safety of nuclear power
(B) The cost of nuclear power is high
(C) There is a lack of public support for nuclear power -
The future of nuclear power will depend on:
(A) The development of new technologies
(B) The public’s perception of nuclear power
(C) The cost of nuclear power