nuclear ng ina mo

8/11/2019 Nuclear Ng Ina Mo

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Nuclear Power Plant

A nuclear power plant is a thermal power stationin which the heat source is a nuclear reactor. As istypical in all conventional thermal power stationsthe heat is used to generate steam which drives a

steam turbine connected to a generator whichproduces electricity. As of 16 January 2013, theIAEA report there are 439 nuclear power reactorsin operation operating in 31 countries. Nuclear

power plants are usually considered to be baseload stations, since fuel is a small part of the costof production.


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Nuclear fission

Nuclear fission is a process in nuclear physicsin which the nucleus of an atom splits intotwo or more smaller nuclei as fissionproducts, and usually some by-productparticles.

Hence, fission is a form of elementaltransmutation. The by-products include freeneutrons, photons usually in the form

gamma rays, and other nuclear fragmentssuch as beta particles and alpha particles.Fission of heavy elements is an exothermicreaction and can release substantial amountsof useful energy both as gamma rays and askinetic energy of the fragments (heating thebulk material where fission takes place).

Nuclear fission produces energy for nuclear

power and to drive explosion of nuclearweapons.


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Fusion Reactions

Nuclear fusion is a process where two ormore nuclei combine to form an elementwith a higher atomic number (more protonsin the nucleus). Fusion is the reverse processof nuclear fission. Fusion releases energy.The energy released is related to Einstein'sfamous equation, E=mc2.

For a fusion reaction to occur it is necessary

to bring the nuclei so close together thatnuclear forces become important and "glue"the nuclei together. The nuclear force onlyacts over incredibly small distances and hasto counteract the electrostatic force wherethe positively charged nuclei repel eachother. For these reasons fusion most easilyoccurs in a high density, high temperatureenvironment.


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History

Electricity was generated by a nuclearreactor for the first time ever on September3, 1948 at the X-10 Graphite Reactor in OakRidge, Tennessee in the United States, andwas the first nuclear power plant to power alight bulb. The second, larger experimentoccurred on December 20, 1951 at the EBR-Iexperimental station near Arco, Idaho in the

United States. On June 27, 1954, the world'sfirst nuclear power plant to generateelectricity for a power grid started operationsat Obninsk, USSR. The world's first full scalepower station, Calder Hall in England openedon October 17, 1956

1896 - Discovery of natural radioactivity byHenry Becquerel* (Paris)

1898- Discovery of Radium by Pierre etMarie Curie* (Paris) (they create the term"radioactivity")

1905- Theory of relativity by Albert Einstein(Germany): equivalence between mass andenergy is established (the basic phenomenainvolved in energy release by fission)

1911- Rutherford creates a model of theatoms (England)

1919- First observation of artificialtransmutation (particles on gold atom) byErnest Rutherford (England), and discoveryof the proton (same time)

1932 - Discovery of the neutron by JamesChadwick (England)

1934 Discovery of artificial radioactivity(particles on Aluminum atoms) by FredericJoliot and Irne Curie (Paris)


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Nuclear Reactor

All nuclear reactors are devices designed to maintain achain reaction producing a steady flow of neutronsgenerated by the fission of heavy nuclei. They are,however, differentiated either by their purpose or bytheir design features. In terms of purpose, they areeither research reactors or power reactors.

Research reactorsare operated at universities andresearch centres in many countries, including somewhere no nuclear power reactors are operated. These

reactors generate neutrons for multiple purposes,including producing radiopharmaceuticals for medicaldiagnosis and therapy, testing materials and conductingbasic research.

Power reactorsare usually found in nuclear powerplants. Dedicated to generating heat mainly forelectricity production, they are operated in more than30 countries (see Nuclear Power Reactors). Their lesseruses are drinking water or district water production. In

the form of smaller units, they also power ships.

There are many different types of power reactors. What iscommon to them all is that they produce thermal energy thatcan be used for its own sake or converted into mechanicalenergy and ultimately, in the vast majority of cases, intoelectrical energy.

In these reactors, the fission of heavy atomic nuclei, the mostcommon of which is uranium-235, produces heat that istransferred to a fluid which acts as a coolant. During thefission process, bond energy is released and this firstbecomes noticeable as the kinetic energy of the fission

products generated and that of the neutrons being released.Since these particles undergo intense deceleration in the solidnuclear fuel, the kinetic energy turns into heat energy.

In the case of reactors designed to generate electricity, towhich the explanations below will now be restricted, theheated fluid can be gas, water or a liquid metal. The heatstored by the fluid is then used either directly (in the case ofgas) or indirectly (in the case of water and liquid metals) togenerate steam. The heated gas or the steam is then fed intoa turbine driving an alternator.

Since, according to the laws of nature, heat cannot fully beconverted into another form of energy, some of the heat isresidual and is released into the environment. Releasing iseither directe.g. into a riveror indirect, into theatmosphere via cooling towers. This practice is common to allthermal plants and is by no means limited to nuclear reactorswhich are only one type of thermal plant.


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Types of Nuclear Power Reactors

RBMK-reactors(pressure-tube boiling-waterreactors), which are cooled with light water andmoderated with graphite, are now less commonlyoperated in some former Soviet Union bloccountries. Following the Chernobyl accident (26April 1986) the construction of this reactor typeceased. The operating period of those units still inoperation will be shortened.

Plutonium-fuelled Reactors - Plutonium (Pu) is anartificial element produced in uranium-fuelledreactors as a by-product of the chain reaction. It isone hundred times more energetic than naturaluranium; one gram of Pu can generate as muchenergy as one tonne of oil. As it needs fast neutronsin order to fission, moderating materials must beavoided to sustain the chain reaction in the bestconditions. The current Plutonium-fuelled reactors,also called fast reactors, use liquid sodium which

displays excellent thermal properties withoutadversely affecting the chain reaction. These typesof reactors are in operation in France, Japan and theCommonwealth of Independent States (CIS).

Light Water Reactors -The Light Water Reactorscategory comprises pressurised water reactors(PWR, VVER) and boiling water reactors (BWR).Both of these use light water and hence enricheduranium. The light water they use combines thefunctions of moderator and coolant. This waterflows through the reactor core, a zone containing alarge array of fuel rods where it picks up the heatgenerated by the fission of the U235 present in thefuel rods. After the coolant has transferred the heatit has collected to a steam turbine, it is sent back tothe reactor core, thus flowing in a loop, also called aprimary circuit.


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Types of Nuclear Power Reactors

Pressurised Water Reactors

The fission zone (fuel elements) is containedin a reactor pressure vessel under a pressureof 150 to 160 bar (15 to 16 MPa). Theprimary circuit connects the reactor pressurevessel to heat exchangers. The secondaryside of these heat exchangers is at a pressureof about 60 bar (6 MPa) - low enough toallow the secondary water to boil. The heatexchangers are, therefore, actually steamgenerators. Via the secondary circuit, thesteam is routed to a turbine driving analternator. The steam coming out of theturbine is converted back into water by acondenser after having delivered a large

amount of its energy to the turbine. It thenreturns to the steam generator. As the waterdriving the turbine (secondary circuit) isphysically separated from the water used asreactor coolant (primary circuit), the turbine-alternator set can be housed in a turbine halloutside the reactor building


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Boiling Water Reactors

The fission zone is contained in a reactor pressure

vessel, at a pressure of about 70 bar (7 MPa). At the

temperature reached (290 C approximately), the

water starts boiling and the resulting steam is

produced directly in the reactor pressure vessel.

After the separation of steam and water in theupper part of the reactor pressure vessel, the steam

is routed directly to a turbine driving an alternator.

The steam coming out of the turbine is converted

back into water by a condenser after having

delivered a large amount of its energy to the

turbine. It is then fed back into the primary cooling

circuit where it absorbs new heat in the fissionzone.

Since the steam produced in the fission zone is

slightly radioactive, mainly due to short-lived

activation products, the turbine is housed in the

same reinforced building as the reactor.


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Systems

The conversion to electrical energy takesplace indirectly, as in conventional thermalpower plants. The heat is produced by fissionin a nuclear reactor (a light water reactor).Directly or indirectly, water vapor (steam) isproduced. The pressurized steam is thenusually fed to a multi-stage steam turbine.Steam turbines in Western nuclear powerplants are among the largest steam turbinesever. After the steam turbine has expandedand partially condensed the steam, theremaining vapor is condensed in acondenser. The condenser is a heatexchanger which is connected to a secondaryside such as a river or a cooling tower. Thewater is then pumped back into the nuclearreactor and the cycle begins again. Thewater-steam cycle corresponds to theRankine cycle.

Steam turbine

The purpose of the steam turbine is toconvert the heat contained in steam intomechanical energy. The engine house withthe steam turbine is usually structurallyseparated from the main reactor building. Itis so aligned to prevent debris from thedestruction of a turbine in operation fromflying towards the reactor.

In the case of a pressurized water reactor,the steam turbine is separated from thenuclear system. To detect a leak in the steamgenerator and thus the passage ofradioactive water at an early stage is the

outlet steam of the steam generatormounted an activity meter. In contrast,boiling water reactors and the steam turbinewith radioactive water applied and thereforepart of the control area of the nuclear powerplant.


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Nuclear reactors

A nuclear reactor is a device toinitiate and control a sustainednuclear chain reaction. The mostcommon use of nuclear reactors is forthe generation of electric energy andfor the propulsion of ships.

The nuclear reactor is the heart ofthe plant. In its central part, thereactor core's heat is generated bycontrolled nuclear fission. With thisheat, a coolant is heated as it ispumped through the reactor andthereby removes the energy from thereactor. Heat from nuclear fission is

used to raise steam, which runsthrough turbines, which in turnpowers either ship's propellers orelectrical generators.


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Since nuclear fission createsradioactivity, the reactor core issurrounded by a protectiveshield. This containment absorbsradiation and preventsradioactive material from being

released into the environment. Inaddition, many reactors areequipped with a dome ofconcrete to protect the reactoragainst both internal casualtiesand external impacts.

In nuclear power plants, different

types of reactors, nuclear fuels,and cooling circuits andmoderators are used.


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Cooling system

A cooling system removes heat from the reactor

core and transports it to another area of the plant,where the thermal energy can be harnessed toproduce electricity or to do other useful work.Typically the hot coolant is used as a heat source fora boiler, and the pressurized steam from that boilerpowers one or more steam turbine driven electricalgenerators.

Safety valves

In the event of an emergency, two independentsafety valves can be used to prevent pipes frombursting or the reactor from exploding. The valvesare designed so that they can derive all of thesupplied flow rates with little increase in pressure.In the case of the BWR, the steam is directed intothe condensate chamber and condenses there. Thechambers on a heat exchanger are connected to theintermediate cooling circuit.

Feedwater pump

The water level in the steam generator and nuclear

reactor is controlled using the feedwater system.The feedwater pump has the task of taking thewater from the condensate system, increasing thepressure and forcing it into either the SteamGenerators (Pressurized Water Reactor) or directlyinto the reactor vessel (Boiling Water Reactor)

Emergency power supply

The emergency power supplies of a nuclear powerplant are built up by several layers of redundancy,such as diesel generators, gas turbine generatorsand battery buffers. The battery backup providesuninterrupted coupling of the diesel/gas turbineunits to the power supply network. If necessary, theemergency power supply allows the safe shut downof the nuclear reactor. Less important auxiliarysystems such as, for example, heat tracing ofpipelines are not supplied by these back ups. Themajority of the required power is used to supply thefeed pumps in order to cool the reactor and removethe decay heatafter a shut down.


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People in a nuclear power plant

Nuclear engineers

Reactor operators

Health physicists

Emergency response team personnel

Nuclear Regulatory Commission ResidentInspectors

In the United States and Canada, workersexcept for management, professional (suchas engineers) and security personnel arelikely to be members of either theInternational Brotherhood of ElectricalWorkers (IBEW) or the Utility Workers Unionof America (UWUA), or one of the varioustrades and labor unions representing

Machinist, laborers, boilermakers,millwrights, iron workers etc.

Safety

There are trades to be made between safety,economic and technical properties ofdifferent reactor designs for particularapplications. Historically these decisionswere often made in private by scientists,regulators and engineers, but this may beconsidered problematic, and since Chernobyl

and Three Mile Island, many involved nowconsider informed consent and morality tobe primary considerations.


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Failure modes of nuclear power plants

There are concerns that a combination of human and mechanical error at a nuclear facility couldresult in significant harm to people and the environment.

Operating nuclear reactors contain large amounts of radioactive fission products which, ifdispersed, can pose a direct radiation hazard, contaminate soil and vegetation, and be ingested byhumans and animals. Human exposure at high enough levels can cause both short-term illness anddeath and longer-term death by cancer and other diseases.

It is impossible for a commercial nuclear reactor to explode like a nuclear bomb since the fuel isnever sufficiently enriched for this to occur. Nuclear reactors can fail in a variety of ways. Should

the instability of the nuclear material generate unexpected behavior, it may result in anuncontrolled power excursion. Normally, the cooling system in a reactor is designed to be able tohandle the excess heat this causes; however, should the reactor also experience a loss-of-coolantaccident, then the fuel may melt or cause the vessel in which it is contained to overheat and melt.This event is called a nuclear meltdown.

After shutting down, for some time the reactor still needs external energy to power its coolingsystems. Normally this energy is provided by the power grid to which that plant is connected, or byemergency diesel generators. Failure to provide power for the cooling systems, as happened inFukushima I, can cause serious accidents.

Nuclear safety rules in the United States "do not adequately weigh the risk of a single event thatwould knock out electricity from the grid and from emergency generators, as a quake and tsunamirecently did in Japan", Nuclear Regulatory Commission officials said in June 2011.


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Multiple reactors

The Fukushima nuclear disaster illustrated the dangersof building multiple nuclear reactor units close to oneanother. This proximity triggered the parallel, chain-

reaction accidents that led to hydrogen explosionsdamaging reactor buildings and water draining fromopen-air spent fuel pools -- a situation that waspotentially more dangerous than the loss of reactorcooling itself. Because of the closeness of the reactors,Plant Director Masao Yoshida "was put in the positionof trying to cope simultaneously with core meltdownsat three reactors and exposed fuel pools at three units"


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Nuclear safety systems

The three primary objectives of nuclear safetysystems as defined by the Nuclear RegulatoryCommission are to shut down the reactor,

maintain it in a shutdown condition, andprevent the release of radioactive materialduring events and accidents. These objectivesare accomplished using a variety of

equipment, which is part of different systems,of which each performs specific functions.


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Advantages of Nuclear Power Plant

Advantages of nuclear power stations include a vast amount of energy is

produced from little amount of fuel. Nuclear power does not contribute toglobal warming since it does not generate carbon dioxide which pollutes the

environment.

Nuclear power- Nuclear power is clean, safe, reliable, compact, competitive

and practically inexhaustible. Today over 400 nuclear reactors provide base-

load electric power in 30 countries. Fifty years old, it is a relatively mature

technology with the assurance of great improvement in the next generation.

(Hundreds of nuclear reactors furnish reliable and flexible shipboard power:

military ships of course. But the technology is adaptable to civilian maritime

transport.)

Clean- Nuclear energy produces almost no carbon dioxide, and no sulfur

dioxide or nitrogen oxides whatsoever. These gases are produced in vast

quantities when fossil fuels are burned.


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Nuclear waste- One gram of uranium yields about as much energy as a ton ofcoal or oil - it is the famous factor of a million. Nuclear waste is correspondinglyabout a million times smaller than fossil fuel waste, and it is totally confined.

Safe- Nuclear power is safe, as proven by the record of half a century ofcommercial operation, with the accumulated experience of more than 12,000reactor-years.

Reliable - Nuclear reactors provide base-load power and are available over 90% ofthe time; intervals between refuelings have been extended and down time forrefueling has been reduced. In the USA, these improvements over the years have

been the equivalent of adding one reactor a year to the existing fleet. Mostreactors are designed for a life of 40 years; many are reaching that age in goodcondition and extensions of 20 years have usually been granted

Competitive- The cost of nuclear power is competitive and stable. The cost ofnuclear fuel is a small part of the price of a nuclear kiloWatt-hour, whereas fossilfueled power, especially oil and gas, is at the mercy of the market.

Inexhaustible - Uranium is found everywhere in the crust of the Earth it is moreabundant than tin, for example. Major deposits are found in Canada and Australia.It is estimated that increasing the market price by a factor ten would result in 100times more uranium coming to market. Eventually we will be able to recoveruranium from sea water where 4 billion tons are dissolved


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Compact- A nuclear power station is very compact, occupying typically the area ofa football stadium and its surrounding parking lots. Solar cells, wind turbine farms

and growing biomass, all require large areas of land.

Radiation - Fear of the unknown is the merchandise of anti-nuclear greens. Theypreach fear of radiation in general, fear of radioactive waste in particular, fear ofanother major accident such as Three Mile Island or Chernobyl, and fear of nuclearweapons proliferation. Their campaign has been successful only because radiationis a mystery to most people, and very few are aware of the fact that radiation is

present everywhere in the environment. The anti-nuclear organizations alsoexploit the widespread but mistaken interpretation of the studies of the health ofthe survivors of the Hiroshima and Nagasaki bombing: that even a small amount ofradiation is deleterious to health (the LNT hypothesis), and the related concept ofcollective dose.

Old Fashioned Attitudes- Ecological organizations such as Greenpeace have

consistently had an anti-nuclear bias which is more ideological than factual. Anincreasing number of environmentalists are now changing their minds aboutnuclear energy because there are very good, solid, scientific and, above all,environmental reasons to be in favor of nuclear energy


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11 Facts About Nuclear Energy

Nuclear power plants use nuclear fission (theprocess of splitting an atom in two). Nuclear fusion(the process of combining atoms into one) has thepotential to be safer energy because it is producedat a much lower temperature. However, nuclearfusion technology has not yet been developed tooperate within a large power plant.

Nuclear energy comes from uranium, anonrenewable resource that must be mined.

Every 18 to 24 months, a power plant must shutdown to remove its spent uranium fuel, which hasbecome radioactive waste.

13 percent of the worlds electricity comes fromnuclear power plants that emit little to nogreenhouse gases.

Nuclear energy is being used in more than 30

countries around the world, and even powers Marsrovers.

Nuclear power facilities can produce energy at a 91percent efficiency rate 24/7, while maintaining themethod with the lowest emissions.

More than 70 percent of Americas emission-freepower comes from nuclear energy sources.

1 in 5 households and business in the U.S. areelectrically powered by nuclear energy.

United States power plants produce 2,000 metrictons of radioactive waste every year.

The building of new nuclear facilities createsbetween 1,400 and 3,500 jobs for constructionworkers, and after the facility is built maintains 400to 700 permanent positions paying roughly 36 to 44percent more than the average salary of thesurrounding area.

American nuclear energy facilities are the highestregulated plants in the world, subject to more

scrutinous observations and regulations.


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Thats all!

Thank you for listening!

nuclear ng ina mo

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