nuclearv reactor

8/3/2019 Nuclearv Reactor

1/19

The Physics behind the working of

Nuclear Reactors

Made By- Taniya GuptaB.Sc Phy (H) II yr.

Miranda House


2/19

A brief overview:

Nuclear Reactors convert the thermal energy released from nuclear fission.

Fission:When a large fissileatomic nucleus such as uranium-235 or plutonium-239 absorbsa neutron, it may undergo nuclear fission. The heavy nucleus splits into two or morelighter nuclei, releasing kinetic energy, gamma radiation and free neutrons; collectively

known as fission products. A portion of these neutrons may later be absorbed by otherfissile atoms and trigger further fission events, which release more neutrons, and soon. This is known as a nuclear chain reaction.Uranium constantly undergoes spontaneous fission very slowly.

Thus, that is why Uranium emits radiation, and is a natural choice for the inducedfission which is a foremost requirement of nuclear power plants.

Uranium is the principle element used in nuclear reactors
http://en.wikipedia.org/wiki/Nuclear_fissionhttp://en.wikipedia.org/wiki/Fissilehttp://en.wikipedia.org/wiki/Atomic_nucleushttp://en.wikipedia.org/wiki/Uranium-235http://en.wikipedia.org/wiki/Plutonium-239http://en.wikipedia.org/wiki/Neutronhttp://en.wikipedia.org/wiki/Kinetic_energyhttp://en.wikipedia.org/wiki/Gamma_rayshttp://en.wikipedia.org/wiki/Free_neutronhttp://en.wikipedia.org/wiki/Fission_productshttp://en.wikipedia.org/wiki/Fission_productshttp://en.wikipedia.org/wiki/Free_neutronhttp://en.wikipedia.org/wiki/Gamma_rayshttp://en.wikipedia.org/wiki/Gamma_rayshttp://en.wikipedia.org/wiki/Kinetic_energyhttp://en.wikipedia.org/wiki/Kinetic_energyhttp://en.wikipedia.org/wiki/Neutronhttp://en.wikipedia.org/wiki/Plutonium-239http://en.wikipedia.org/wiki/Plutonium-239http://en.wikipedia.org/wiki/Plutonium-239http://en.wikipedia.org/wiki/Uranium-235http://en.wikipedia.org/wiki/Uranium-235http://en.wikipedia.org/wiki/Uranium-235http://en.wikipedia.org/wiki/Atomic_nucleushttp://en.wikipedia.org/wiki/Fissilehttp://en.wikipedia.org/wiki/Nuclear_fission


3/19

The nuclear chain reaction can be controlled by using neutron poisons, whichabsorb excess neutrons, and neutron moderators which reduces the velocity of fastneutrons, thereby turning them into thermal neutrons, which are more likely to be

absorbed by other nuclei.

Increasing or decreasing the rate of fission has a corresponding effect on the energyoutput of the reactor. Commonly used moderators include regular water (75% of theworld's reactors), solid graphite (20% of reactors) and heavy water (5% ofreactors). Beryllium has also been used in some experimental types,and hydrocarbons have been suggested as another possibility.

Heat generation:The reactor core generates heat in a number of ways:

1. The kinetic energy of fission products is converted to thermal energy when these

nuclei collide with nearby atoms.

2.Some of the gamma rays produced during fission are absorbed by the reactor, theirenergy being converted to heat.
http://en.wikipedia.org/wiki/Neutron_poisonhttp://en.wikipedia.org/wiki/Neutron_moderatorhttp://en.wikipedia.org/wiki/Neutron_temperaturehttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Heavy_waterhttp://en.wikipedia.org/wiki/Berylliumhttp://en.wikipedia.org/wiki/Hydrocarbonshttp://en.wikipedia.org/wiki/Kinetic_energyhttp://en.wikipedia.org/wiki/Thermal_energyhttp://en.wikipedia.org/wiki/Gamma_rayshttp://en.wikipedia.org/wiki/Gamma_rayshttp://en.wikipedia.org/wiki/Thermal_energyhttp://en.wikipedia.org/wiki/Kinetic_energyhttp://en.wikipedia.org/wiki/Hydrocarbonshttp://en.wikipedia.org/wiki/Berylliumhttp://en.wikipedia.org/wiki/Heavy_waterhttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Neutron_temperaturehttp://en.wikipedia.org/wiki/Neutron_moderatorhttp://en.wikipedia.org/wiki/Neutron_poison


4/19

3.Heat produced by the radioactive decay of fission products and materials that have beenactivated by neutron absorption. This decay heat source will remain for some time even after thereactor is shut down.

Fact-A kilogram of uranium-235 (U-235) converted via nuclear processes contains approximatelythree million times the energy of 1 kg of coal burned conventionally.

Cooling:A nuclear reactor coolant usually waterbut sometimes a gas or a liquid metal is circulatedpast the reactor core to absorb the heat that it generates.

The heat is then carried away from the reactor and is then used to generate steam. Most reactorsystems employ a cooling system that is physically separated from the water that will be boiledto produce pressurized steam for the turbines, like the pressurized water reactor. But in some

reactors the water for the steam turbines is boiled directly by the reactor core.
http://en.wikipedia.org/wiki/Radioactive_decayhttp://en.wikipedia.org/wiki/Neutron_absorptionhttp://en.wikipedia.org/wiki/Uranium-235http://en.wikipedia.org/wiki/Nuclear_reactor_coolanthttp://en.wikipedia.org/wiki/Turbineshttp://en.wikipedia.org/wiki/Pressurized_water_reactorhttp://en.wikipedia.org/wiki/Reactor_corehttp://en.wikipedia.org/wiki/Reactor_corehttp://en.wikipedia.org/wiki/Pressurized_water_reactorhttp://en.wikipedia.org/wiki/Turbineshttp://en.wikipedia.org/wiki/Nuclear_reactor_coolanthttp://en.wikipedia.org/wiki/Uranium-235http://en.wikipedia.org/wiki/Uranium-235http://en.wikipedia.org/wiki/Uranium-235http://en.wikipedia.org/wiki/Neutron_absorptionhttp://en.wikipedia.org/wiki/Radioactive_decay


5/19


6/19

In other reactors the coolant acts as a poison by absorbing neutrons in the same waythat the control rods do. In these reactors power output can be increased by heatingthe coolant, which makes it a less dense poison. Nuclear reactors generally have

automatic and manual systems to insert large amounts of poison (often boron in theform of boric acid) into the reactor to shut the fission reaction down if unsafeconditions are detected or anticipated.

Electrical power generation:The energy released in the fission process generates heat, some of which can beconverted into usable energy. A common method of harnessing this thermalenergy is to use it to boil water to produce pressurized steam which will then drivea steam turbine that generates electricity.
http://en.wikipedia.org/wiki/Thermal_energyhttp://en.wikipedia.org/wiki/Thermal_energyhttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Thermal_energyhttp://en.wikipedia.org/wiki/Thermal_energy


7/19

Now in detail

How Fission occurs in Uranium ?

An induced nuclear fission event. A neutron isabsorbed by the nucleus of a uranium-235atom, which in turn splits into fast-movinglighter elements (fission products) and freeneutrons. Though both reactors and nuclearweapons rely on nuclear chain reactions, the

rate of reactions in a reactor is much slowerthan in a bomb.
http://en.wikipedia.org/wiki/Nuclear_weaponshttp://en.wikipedia.org/wiki/Nuclear_weaponshttp://en.wikipedia.org/wiki/Nuclear_weaponshttp://en.wikipedia.org/wiki/Nuclear_weapons


8/19

When a neutron approaches a uranium-235 nucleus , the probability of a U-235 atom capturing a neutron as it passes by is high. In fact, under reactor

conditions, one neutron ejected from each fission causes another fission tooccur.As soon as the nucleus captures the neutron, it splits into two lighter atomsand throws off two or three new neutrons (the number of ejected neutronsdepends on how the U-235 atom splits).

The process of capturing the neutron and splitting happens very quickly, onthe order of picoseconds (10-12sec).The decay of a single U-235 atom releases approximately 200 MeV (millionelectron volts).

The following equation is the example of the different products that can beproduced when235U fissions:

235U + 1 neutron 2 neutrons +92Kr +142Ba + ENERGY


9/19

Another detailed diagram of NuclearFission in Uranium


10/19

Now,Inside a Nuclear Power Plant
http://science.howstuffworks.com/nuclear-power3.htmhttp://science.howstuffworks.com/nuclear-power3.htmhttp://science.howstuffworks.com/nuclear-power3.htmhttp://science.howstuffworks.com/nuclear-power3.htmhttp://science.howstuffworks.com/nuclear-power3.htmhttp://science.howstuffworks.com/nuclear-power3.htm


11/19

To turn nuclear fission into electrical energy,Firstly, we require is that a nuclear power plant should be able to control the energy given off by the

enriched uranium and allow it to heat water into steam.

Now for that an enriched Uranium is typically formed into 2.5-cm-long pellets, each with approximately thesame diameter.Next the pellets are arranged into long rods, and the rods are collected together into bundles, then thesebundles are submerged in water inside a pressure vessel.The water acts as a coolant.For the reactor to work, the submerged bundles must be slightly supercritical. Left to its own devices, the

uranium would eventually get overheated and will melt. To prevent overheating, control rods made of amaterial that absorbs neutrons are inserted into the uranium bundle using a mechanism that can raise orlower the control rods.Raising and lowering the control rods allow operators to control the rate of the nuclear rxn.When an operator wants the uranium core to produce more heat, the control rods are raised out of theuranium bundle (thus absorbing fewer neutrons) and to create less heat, they are lowered into theuranium bundle.The rods can also be lowered completely into the uranium bundle to shut the reactor down in the case of

an accident or to change the fuel. The Uranium bundle acts as an extremely high-energy source of heat. Itheats the water and turns it into steam. The steam drives a turbine, which spins a generator to producepower.In some nuclear power plants, the steam from the reactor goes through a secondary intermediate heatexchanger to convert another loop of water to steam, which drives the turbine. The advantage to thisdesign is that the radioactive water/steam never contacts the turbine.

Working
http://science.howstuffworks.com/electricity.htmhttp://science.howstuffworks.com/h2o.htmhttp://science.howstuffworks.com/h2o.htmhttp://science.howstuffworks.com/electricity.htm


12/19

How to stop the chain rxn if needed?

In classical Nuclear plants they use Uranium bars put very closetogether inside water, in this way the neutrons from one bar hit theother generating more neutrons and so on.

So, for stopping the chain reaction what we need to do is to stop theneutrons from hitting the other uranium bars. And this is done byinserting the uranium bars inside carbon cases, the carbon absorbs theneutrons and don't let them hit the other uranium bars.

New reactors like the French and Japanese fast reactors, work in a

different way, but the principle remains the same, controlling theamount of neutrons flying free in the process, allow you to control theamount of energy and heat you get.

And thus the chain rxn in the uranium atom goes on


13/19

Now as we know that there is a real chance of posing life threatening risks if incase a radioactive material gets leaked out in the atmosphere

So, to overcome such a menace situation,A concrete liner typically houses the reactor's pressure vessel and actsas a radiation shield. That liner, in turn, is housed within a much largersteel containment vessel. This vessel contains the reactor core, as wellas the equipment plant workers use to refuel and maintain the reactor.The steel containment vessel serves as a barrier to prevent leakage ofany radioactive gases or fluids from the plant.An outer concrete building serves as the final outer layer, protecting thesteel containment vessel. This concrete structure is strong enough tosurvive the kind of massive damage that might result from earthquakesor a crashing jet airliner. These secondary containment structures arenecessary to prevent the escape of radiation or radioactive steam in theevent of an accident. The absence of secondary containment structuresin Russian nuclear power plants allowed radioactive material to escapein the environment, in recent past in 1986.


14/19

As you can see in the picture below that a concrete liner houses this power plantwhich acts as a radiation shield.


15/19

A few more images of the nuclear reactors across the world housed in a concrete liner

Nuclear power provides electricity for a significantpercentage of the population. This nuclear powerplant is located near Dukovany, Czech Republic.

This containment building houses the nuclearreactor

This nuclear containment helps prevent catastrophicevents like the accident at Chernobyl


16/19

The nuclear reactor is the heart of a nuclearpower plant. The concrete keeps the radiationfrom escaping

These pipes carry the steam from the reactor thatis used to produce electricity.


17/19

Name Location

Tarapur Atomic Power Station Tarapur,Maharashtra

Rajasthan Atomic Power Station Rawatbhata, Rajasthan

Madras Atomic Power Station Kalpakkam, Tamilnadu

Narora Atomic Power Station Narora, Uttar Pradesh

Kakrapar Atomic Power Station Kakrapar, Gujarat

Kaiga Atomic Power Station Kaiga, Karnataka

Koodankulam Nuclear Power

PlantKudankulam, Tamilnadu

Prototype Fast Breeder Reactor Kalpakkam, Tamilnadu

Power station reactors in INDIA
http://en.wikipedia.org/wiki/Tarapur_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Tarapur,_Maharashtrahttp://en.wikipedia.org/wiki/Maharashtrahttp://en.wikipedia.org/wiki/Rajasthan_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Rawatbhatahttp://en.wikipedia.org/wiki/Rajasthanhttp://en.wikipedia.org/wiki/Madras_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Kalpakkamhttp://en.wikipedia.org/wiki/Tamilnaduhttp://en.wikipedia.org/wiki/Narora_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Narorahttp://en.wikipedia.org/wiki/Uttar_Pradeshhttp://en.wikipedia.org/wiki/Kakrapar_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Gujarathttp://en.wikipedia.org/wiki/Kaiga_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Kaigahttp://en.wikipedia.org/wiki/Karnatakahttp://en.wikipedia.org/wiki/Koodankulam_Nuclear_Power_Planthttp://en.wikipedia.org/wiki/Koodankulam_Nuclear_Power_Planthttp://en.wikipedia.org/wiki/Kudankulamhttp://en.wikipedia.org/wiki/Tamilnaduhttp://en.wikipedia.org/wiki/Prototype_Fast_Breeder_Reactorhttp://en.wikipedia.org/wiki/Kalpakkamhttp://en.wikipedia.org/wiki/Tamilnaduhttp://en.wikipedia.org/wiki/Tamilnaduhttp://en.wikipedia.org/wiki/Kalpakkamhttp://en.wikipedia.org/wiki/Prototype_Fast_Breeder_Reactorhttp://en.wikipedia.org/wiki/Tamilnaduhttp://en.wikipedia.org/wiki/Kudankulamhttp://en.wikipedia.org/wiki/Koodankulam_Nuclear_Power_Planthttp://en.wikipedia.org/wiki/Koodankulam_Nuclear_Power_Planthttp://en.wikipedia.org/wiki/Koodankulam_Nuclear_Power_Planthttp://en.wikipedia.org/wiki/Karnatakahttp://en.wikipedia.org/wiki/Kaigahttp://en.wikipedia.org/wiki/Kaiga_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Kaiga_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Kaiga_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Kaiga_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Gujarathttp://en.wikipedia.org/wiki/Kakrapar_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Kakrapar_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Kakrapar_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Kakrapar_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Uttar_Pradeshhttp://en.wikipedia.org/wiki/Narorahttp://en.wikipedia.org/wiki/Narora_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Narora_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Narora_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Narora_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Tamilnaduhttp://en.wikipedia.org/wiki/Kalpakkamhttp://en.wikipedia.org/wiki/Madras_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Madras_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Rajasthanhttp://en.wikipedia.org/wiki/Rawatbhatahttp://en.wikipedia.org/wiki/Rajasthan_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Rajasthan_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Rajasthan_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Rajasthan_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Maharashtrahttp://en.wikipedia.org/wiki/Tarapur,_Maharashtrahttp://en.wikipedia.org/wiki/Tarapur_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Tarapur_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Tarapur_Atomic_Power_Stationhttp://en.wikipedia.org/wiki/Tarapur_Atomic_Power_Station


18/19

Pros and Cons of Nuclear Power Plants

Whether one views nuclear power as the promise for a better tomorrow or a whoppingdown payment on a mutant-filled apocalypse, there's a good chance that one won't be

easily converted to the other side. After all, nuclear power boasts a number of advantages,as well as its share of downright depressing negatives.

As far as positivesgo, nuclear power's biggest advantages are tied to the simple factthat it doesn't depend on fossil fuels. Coal and natural gas power plants emit carbondioxide into the atmosphere, contributing to climate change. With nuclear power plants,CO

2emissions are minimal.

According to the Nuclear Energy Institute, the power produced by the world's nuclearplants would normally produce 2 billon metric tons of CO2 per year if they depended onfossil fuels. In fact, a properly functioning nuclear power plant actually releases lessradioactivity into the atmosphere than a coal-fired power plant. By not depending on fossilfuels, the cost of nuclear power also isn't affected by fluctuations in oil and gas prices.

As for negatives, nuclear fuel may not produce CO2, but it does provide its share ofproblems. Historically, mining and purifying uranium hasn't been a very clean process.Even transporting nuclear fuel to and from plants poses a contamination risk. And once thefuel is spent, you can't just throw it in the city dump. It's still radioactive and potentiallydeadly
http://science.howstuffworks.com/nuclear-power5.htmhttp://science.howstuffworks.com/nuclear-power5.htm


19/19

Continuation..

On average, a nuclear power plant annually generates 20 metric tons of used nuclearfuel, classified as high-level radioactive waste. When you take into account every

nuclear plant on Earth, the combined total climbs to roughly 2,000 metric tons yearly.All of this waste emits radiation and heat, meaning that it will eventually corrode anycontainer and can prove lethal to nearby life forms. As if this weren't bad enough,nuclear power plants produce a great deal of low-level radioactive waste in the form ofradiated parts and equipment.

Nuclear waste can pose a problem, and it's the result of properly functioning nuclear

power plants. When something goes wrong, the situation can turn catastrophic.

So, Some people think of nuclear power as a threatening menace,while others see it as a long-term source of greener electricity.

Thank You
http://science.howstuffworks.com/earth.htmhttp://science.howstuffworks.com/earth.htm

nuclearv reactor

Documents