In the nuclear fission power plant, the heat generates by a nuclear fission process is used to turns a steam turbine which produce electric power.
When neutron is absorbed by the atom of nuclear fuel uranium, the fission reaction takes place which cause the splitting of uranium into two smaller atoms waste. In the nuclear reactor, the energy produced by enriched uranium must be control and allows it to heat water into steam. The uranium pellets are arranged as long rods which are collected together to form bundles. If more energy is needed then the rods are lifted out from the bundle to absorb few electrons and for reducing heat, control rods are lowered into the uranium bundle. Some important factors should be take care during process like control the reaction, safety, addition of nuclear fuel (refueling), production of waste, efficiency of generating heat etc. This is one of the most common types of power generation reactor in which ordinary water is used as coolant and moderator.
The boiling water reactors are very similar to PWR but there is only one difference is that only single circuit is used in BWR. Due to its simple design and short lived water radioactivity, the turbine hall can be entered just after the reactor is shut down.
The reactor can be refueled easily by isolating individual pressure tubes from the cooling circuit without shutdown the reactor. Newly designed PHWR are like the Advanced Candu Reactor contains light water cooling and enriched fuel. CANDU reactors can be processes with recycled uranium from reprocessing fuel of Light Water Reactor and depleted uranium of enrichment plants.4.
The AGR was generated from the Magnox reactor in which graphite and CO2 are used as moderator and coolant respectively, natural uranium as fuel and water as secondary coolant. These types of reactors do not contain moderator and fast neutrons are used to generate power. Most nuclear electricity is generated using just two kinds of reactors which were developed in the 1950s and improved since. New designs are coming forward and some are in operation as the first generation reactors come to the end of their operating lives.
Over 11% of the world's electricity is produced from nuclear energy, more than from all sources worldwide in 1960. A nuclear reactor produces and controls the release of energy from splitting the atoms of certain elements.
The principles for using nuclear power to produce electricity are the same for most types of reactor.
The world's first nuclear reactors operated naturally in a uranium deposit about two billion years ago. Today, reactors derived from designs originally developed for propelling submarines and large naval ships generate about 85% of the world's nuclear electricity.
Most reactors need to be shut down for refuelling, so that the pressure vessel can be opened up. If graphite or heavy water is used as moderator, it is possible to run a power reactor on natural instead of enriched uranium. In most reactors the fuel is ceramic uranium oxide (UO2 with a melting point of 2800°C) and most is enriched. Burnable poisons are often used (especially in BWR) in fuel or coolant to even out the performance of the reactor over time from fresh fuel being loaded to refuelling. Thermal MWt, which depends on the design of the actual nuclear reactor itself, and relates to the quantity and quality of the steam it produces. Gross electrical MWe indicates the power produced by the attached steam turbine and generator, and also takes into account the ambient temperature for the condenser circuit (cooler means more electric power, warmer means less). This is the most common type, with over 230 in use for power generation and several hundred more employed for naval propulsion.
A PWR has fuel assemblies of 200-300 rods each, arranged vertically in the core, and a large reactor would have about 150-250 fuel assemblies with 80-100 tonnes of uranium. Water in the reactor core reaches about 325°C, hence it must be kept under about 150 times atmospheric pressure to prevent it boiling.
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.
A BWR fuel assembly comprises 90-100 fuel rods, and there are up to 750 assemblies in a reactor core, holding up to 140 tonnes of uranium. The PHWR reactor design has been developed since the 1950s in Canada as the CANDU, and from 1980s also in India. The moderator is in a large tank called a calandria, penetrated by several hundred horizontal pressure tubes which form channels for the fuel, cooled by a flow of heavy water under high pressure in the primary cooling circuit, reaching 290°C.
Newer PHWR designs such as the Advanced Candu Reactor (ACR) have light water cooling and slightly-enriched fuel.
These are the second generation of British gas-cooled reactors, using graphite moderator and carbon dioxide as primary coolant.
The AGR was developed from the Magnox reactor, also graphite moderated and CO2 cooled, and one of these is still operating in UK to late 2014. More than a dozen (Generation III) advanced reactor designs are in various stages of development. Considering the closed fuel cycle, Generation 1-3 reactors recycle plutonium (and possibly uranium), while Generation IV are expected to have full actinide recycle. Some reactors (only one in commercial service) do not have a moderator and utilise fast neutrons, generating power from plutonium while making more of it from the U-238 isotope in or around the fuel. Apart from over 200 nuclear reactors powering various kinds of ships, Rosatom in Russia has set up a subsidiary to supply floating nuclear power plants ranging in size from 70 to 600 MWe.
The Russian KLT-40S is a reactor well proven in icebreakers and now proposed for wider use in desalination and, on barges, for remote area power supply. Most of today's nuclear plants which were originally designed for 30 or 40-year operating lives.
Another important issue is knowledge management (KM) over the full lifecycle from design, through construction and operation to decommissioning for reactors and other facilities. The advent of some of the designs mentioned above provides opportunity to review the various primary heat transfer fluids used in nuclear reactors. Water or heavy water must be maintained at very high pressure (1000-2200 psi, 7-15 MPa, 150 atmospheres) to enable it to function well above 100°C, up to 345°C, as in present reactors. Helium must be used at similar pressure (1000-2000 psi, 7-14 MPa) to maintain sufficient density for efficient operation.
Carbon dioxide was used in early British reactors, and their current AGRs which operate at much higher temperatures than light water reactors. Lead or lead-bismuth eutectic in fast neutron reactors are capable of higher temperature operation. There is some radioactivity in the cooling water flowing through the core of a water-cooled reactor, due mainly to the activation product nitrogen-16, formed by neutron capture from oxygen.


Producing steam to drive a turbine and generator is relatively easy, and a light water reactor running at 350°C does this readily. The world's oldest known nuclear reactors operated at what is now Oklo in Gabon, West Africa.
During this long reaction period about 5.4 tonnes of fission products as well as up to two tonnes of plutonium together with other transuranic elements were generated in the orebody. The energy used to sustain the nuclear fission to generate heat which further used to generate electricity. The nuclear power reactor involves the use of released energy as heat to make steam for generating electricity. The physical process is common for all power plant but they differ only the way by which the nuclear reaction is controlled. In the case of fast reactor, these high energy neutrons are directly absorbed by the other uranium atom. In these reactors, the speed of produced neutrons is in control so that neutrons are absorbed by the correct isotope of uranium-235.
In the case of a large reactor, approximately 150 to 250 fuel assemblies are used which contain 80 to 100 tons of uranium as reactor fuel.
Plutonium or Uranium-238 is used as fuel which produces 60 times more energy than as the original uranium in the normal reactors but they are commercially not viable as they are expensive reactors.
For more advanced types, see Advanced Reactors and Small Reactors papers, and also Generation IV reactors. In a nuclear power reactor, the energy released is used as heat to make steam to generate electricity.
The energy released from continuous fission of the atoms of the fuel is harnessed as heat in either a gas or water, and is used to produce steam. Each structure weighs up to 800 tonnes and contains from 300 to 16,000 tubes about 2 cm diameter for the primary coolant, which is radioactive due to nitrogen-16 (N-16, formed by neutron bombardment of oxygen, with half-life of 7 seconds). The structure around the reactor and associated steam generators which is designed to protect it from outside intrusion and to protect those outside from the effects of radiation in case of any serious malfunction inside. These are neutron absorbers which decay under neutron exposure, compensating for the progressive build up of neutron absorbers in the fuel as it is burned.
This relates to the difference in temperature between the steam from the reactor and the cooling water. The reactor is designed to operate with 12-15% of the water in the top part of the core as steam, and hence with less moderating effect and thus efficiency there.
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. 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. 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. While they get more than 60 times as much energy from the original uranium compared with the normal reactors, they are expensive to build.
Here a 150 MWt unit produces 35 MWe (gross) as well as up to 35 MW of heat for desalination or district heating.
Load following is not as readily achieved in a PWR, but especially in France since 1981, so-called 'grey' control rods are used. Water is a lot more effective than air for removing heat, though its thermal conductivity is less than liquid alternatives. Again, there are engineering implications, but it can be used in the Brayton cycle to drive a turbine directly.
They are transparent to neutrons, aiding efficiency due to greater spacing between fuel pins which then allows coolant flow by convection for decay heat removal, and since they do not react with water the heat exchanger interface is safer.
Fluoride salts have a very high boiling temperature, very low vapour pressure even at red heat, very high volumetric heat capacity (carry more heat than the same volume of water), good heat transfer properties, low neutron absorbtion, good neutron moderation capability, are not damaged by radiation, are chemically very stable so absorb all fission products well and do not react violently with air or water, are compatible with graphite, and some are also inert to some common structural metals. Some gamma-active F-20 is formed by neutron capture, but has very short half-life (11 seconds). Also, with a good margin between operating and boiling temperatures, passive cooling for decay heat is readily achieved. Since heat exchangers do leak to some small extent, having incompatible primary and secondary coolants can be a problem. As the above section and Figure show, other types of reactor are required for higher temperatures. About 2 billion years ago, at least 17 natural nuclear reactors achieved criticality in a rich deposit of uranium ore.
The initial radioactive products have long since decayed into stable elements but close study of the amount and location of these has shown that there was little movement of radioactive wastes during and after the nuclear reactions. With the growth of uses of radioactive isotopes, there is parallel growth observed in the use of X-ray in the form of X-rays machines. As natural uranium oxide is used as fuel which contains 0.7% U-235, so it requires a more efficient moderator.
The steam is used to drive the turbines which produce electricity (as in most fossil fuel plants). The less numerous boiling water reactor (BWR) makes steam in the primary circuit above the reactor core, at similar temperatures and pressure.
The rods are arranged into fuel assemblies in the reactor core.** In a new reactor with new fuel a neutron source is needed to get the reaction going. These are crucial in enabling a chain reacting system (or reactor) to be controllable and to be able to be held precisely critical. Reactors have up to six 'loops', each with a steam generator. Since 1980 over 110 PWR reactors have had their steam generators replaced after 20-30 years service, 57 of these in USA. The CANDU and RBMK types have pressure tubes (rather than a pressure vessel enclosing the reactor core) and can be refuelled under load by disconnecting individual pressure tubes.
In this case the moderator can be ordinary water, and such reactors are collectively called light water reactors. 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. 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. 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.
The former include the Advanced Boiling Water Reactor, a few of which are now operating with others under construction.
The first has two 40 MWe reactors based on those in icebreakers and will operate at a remote site in Siberia.
These are designed to run 3-4 years between refuelling and it is envisaged that they will be operated in pairs to allow for outages, with on-board refuelling capability and used fuel storage. In the USA most of the more than one hundred reactors are expected to be granted licence extensions from 40 to 60 years.
Steam generators are the most prominent and expensive of these, and many have been replaced after about 30 years where the reactor otherwise has the prospect of running for 60 years. The ability of a PWR to run at less than full power for much of the time depends on whether it is in the early part of its 18 to 24-month refuelling cycle or late in it, and whether it is designed with special control rods which diminish power levels throughout the core without shutting it down.


Each operated intermittently at about 20 kW thermal, the reaction ceasing whenever the water turned to steam so that it ceased to function as moderator. The radioactive elements widely used different industries like medical, power plants, in quality control of materials, measuring the level of containers and in monitoring the thickness or consistency of paper. Some design options, such as powering the main large feed-water pumps with electric motors (as in EPR) rather than steam turbines (taking steam before it gets to the main turbine-generator), explains some gross to net differences between different reactor types.
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. Most of the radioactivity in the water is very short-lived*, so the turbine hall can be entered soon after the reactor is shut down.
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.
Generation II reactors are typified by the present US fleet and most in operation elsewhere.
If they are configured to produce more fissile material (plutonium) than they consume they are called Fast Breeder Reactors (FBR). At the end of a 12-year operating cycle the whole plant is taken to a central facility for 2-year overhaul and removal of used fuel, before being returned to service.
Thus, though the ability on any individual PWR reactor to run on a sustained basis at low power decreases markedly as it progresses through the refueling cycle, there is considerable scope for running a fleet of reactors in load-following mode. Lower-temperature reactors can be used with supplemental gas heating to reach higher temperatures, though employing an LWR would not be practical or economic. Compare to other energy production techniques, nuclear power is good enough but in security mode only. Knowledge management is often a shared responsibility and is essential for effective decision-making and the achievement of plant safety and economics.
European Utility Requirements (EUR) since 2001 specify that new reactor designs must be capable of load-following between 50 and 100% of capacity.
Sodium does not corrode the metals used in the fuel cladding or primary circuit, nor the fuel itself if there is cladding damage, but it is very reactive generally. In particular it reacts exothermically with water or steam to liberate hydrogen.
It has a higher neutron cross-section than FLiBe or LiF but can be used intermediate cooling loops. This heat could melt the core of a light water reactor unless it is reliably dissipated, as shown in 2011 at Fukushima, where about 1.5% of the heat was being generated when the tsunami disabled the cooling. Elements with high atomic number like uranium, polonium etc are unstable due to electrostatic repulsion between protons located in a small region of nucleus, hence disintegrated in small element for getting stability.Radioactive decay releases some amount of energy in the form of radiation like alpha rays, beta rays or gamma rays. Uses of nuclear energy - Nuclear reactions like nuclear fusion and nuclear fission release enormous amount of energy which can be used for different purpose like in the production of electricity which is much more efficient compare to thermal power plants.New fundamental particles - During nuclear fusion and nuclear fission, many fundamental particles like neutrons, positrons, deuteron, alpha particles produced due to fission and non-fission reactions. The nuclear power plants are much more efficient than thermal power plant for the generation of electricity. Restarting a reactor with some used fuel may not require this, as there may be enough neutrons to achieve criticality when control rods are removed.
Generation III are the Advanced Reactors evolved from these, the first few of which are in operation in Japan and others are under construction and ready to be ordered. A larger Russian factory-built and barge-mounted reactor is the VBER-150, of 350 MW thermal, 110 MWe. In Candu reactors, pressure tube replacement has been undertaken on some plants after about 30 years operation. See further information in the Nuclear Power in France paper and the 2011 Nuclear Energy Agency report, Technical and Economic Aspects of Load Following with Nuclear Power Plants.
The nuclear power represented by given sign.Nuclear power generated in nuclear power plant where nuclear reaction generates a large amount of energy.
The larger VBER-300 PWR is a 325 MWe unit, originally envisaged in pairs as a floating nuclear power plant, displacing 49,000 tonnes. Sodium has a low neutron capture cross section, but it is enough for some Na-23 to become Na-24, which is a beta-emitter and very gamma-active with 15-hour half-life, so some shielding is required. Many radioactive elements discovered during different nuclear reactions of radioactive elements.Used as Radioactive tracer - A number of radioactive isotopes are used in tracing various process in biology and agriculture industries. The fuel used for nuclear reaction is generally some radioactive elements or their compounds in small quantity.
The Odyssey spacecraft used Gamma rays spectrometer which mainly consists of four main components. If a reactor needs to be shut down frequently, NaK eutectic which is liquid at room temperature (about 13°C) may be used as coolant, but the potassium is pyrophoric, which increases the hazard. Control RodsThey work as a controller to control the rate of nuclear reaction to avoid the nuclear explosion.
The development of nuclear power based on Pb-Bi cooled fast neutron reactors is likely to be limited to a total of 50-100 GWe, basically for small reactors in remote places. No doubt the initial setup for nuclear reactor is very expensive but further maintenance and security is cost effective compare to convectional thermal power plants. In 1998 Russia declassified a lot of research information derived from its experience with submarine reactors, and US interest in using Pb or Pb-Bi for small reactors has increased subsequently. For example, for detecting the circulation of blood during surgery a radioactive isotope is injected into body and after suitable time the flow of blood detected by using Geiger-Muller counter. They can be inserted or withdrawn from the core according to the requirement for control or speed up the rate of reaction respectively.
The Gen4 Module (Hyperion) reactor will use lead-bismuth eutectic which is 45% Pb, 55% Bi. A secondary circuit generating steam is likely.
Radioactive isotopes of carbon and hydrogen are used to detect the path of nutrients into plants.
Compare to all other fuels for the production of electricity like oil, gas and coal, nuclear power is much more cost effective as a very small amount of fuel produce a large amount of energy. That is the reason why nuclear power is the second largest sources of electric power after coal.Nuclear power is a pollutant free fuel and helps to reduce the level of carbon dioxide gas in atmosphere which indirectly helps to reduced the green house effect. The castings are inspected afterwards for radioactivity to find out if penetration of the salts into the cracks has taken place or not.Rock dating - The natural radioactive series of Uranium-235 forms lead-206 as a stable product.
Hence, nuclear power is a safe and large energy source which helps to reduce pollution in atmosphere as well as green house effect. Pressure Vessel or Tubes This is a robust steel vessel that contains the reactor core and moderator or coolant.
In this technique the radioactive isotope of carbon(C-14) is used to estimate the age of earth and for the estimation of age of fossils. In the steam generator, the heat from the reactor comes from the primary coolant and this heat is used to make steam for theturbine. This C-14 has been consumed by plants as well as by other living organism and remains constant for a long time, hence can be detected easily.



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