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TOPIC: Nuclear reactor, challenges,advancements and present status of

world nuclear power generation and

future prospective.

SUBJECT: ELECTRICITY AND MAGNETISMSUBJECT CODE: PHY 102

SUBMITTED TO:-

SUBMITTED BY:- Mr.Manroop Singh Mr. Jagraj Singh

(Dept. of Physics) Regn. No:

10807772

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Section:

211

Roll No:

R211A23

Course:

B.Tech-MBA ECE

ACKNOWLEDGEMENT

I Jagraj Singh of section 211, registration no. 10807772

and roll no. R211A23 hereby submit this term paper of

Electricity and Magnetism to Mr. Manroop Singh (dept. of

physics) on the topic of Nuclear Reactor. I have been

completed this term paper under the guidance of

Mr. Mandeep Ralan (dept. of physics). This topic was

done by me with the help of other faculty members also.

Submitted to:

Mr. Manroop Singh

(Dept. of Physics)

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Abstract:

The reactor is used to convert nuclear (inaccurately also known as

'atomic') energy into heat. While a reactor could be one in which heat is

produced by fusion or radioactive decay, this description focuses on the

basic principles of the fission reactor (or we can say)

A nuclear reactor is a device in which nuclear chain reactions are

initiated, controlled, and sustained at a steady rate, as opposed to a

nuclear bomb, in which the chain reaction occurs in a fraction of a

second and is uncontrolled causing an explosion.

How it works?

An induced nuclear fission event. A neutron is absorbed by the nucleus

of a uranium-235 atom, which in turn splits into fast-moving lighterelements (fission products) and free neutrons. The physics of operating a

nuclear reactor are explained in Nuclear reactor physics.

Just as many conventional thermal power stations generate electricity by

harnessing the thermal energy released from burning fossil fuels, nuclear

power plants convert the thermal energy released from nuclear fission.

Reactor

The reactor is used to convert nuclear (inaccurately also known as'atomic') energy into heat. While a reactor could be one in which heat is

produced by fusion or radioactive decay, this description focuses on the

basic principles of the fission reactor.

Electric power generation

The energy released in the fission process generates heat, some of

which can be converted into usable energy. A common method of

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harnessing this thermal energy is to use it to boil water to produce

pressurized steam which will then drive a steam turbine that generates

electricity.

Table of Contents

Introduction

History- Early Reactors

Classifications

Components

Heat generation Cooling

Reactivity control

Nuclear power generation

Future and developing techniques

Advanced reactors Generation IV reactors

Fueling of nuclear reactors

Challenges

Conclusion

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INTRODUCTION

A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and

sustained at a steady rate, as opposed to a nuclear bomb, in which the chain reaction occurs

in a fraction of a second and is uncontrolled causing an explosion.

The most significant use of nuclear reactors is as an energy source for the generation of

electrical powerand for the power in some ships . This is usually accomplished by methods

that involve using heat from the nuclear reaction to power steam turbines. There are also

other less common uses as discussed below.

History - Early reactors

The first artificial nuclear reactor, Chicago Pile-1, was constructed at the University of

Chicago by a team led by Enrico Fermi in 1942. It achieved criticality on

December 2, 1942 at 3:25 PM. The reactor support structure was made of

wood, which supported a pile of graphite blocks, embedded in which was

natural Uranium-oxide 'pseudospheres' or 'briquettes'. Inspiration for such areactor was provided by the discovery by Lise Meitner, Fritz Strassman and

Otto Hahn in 1938 that bombardment of Uranium with neutrons (provided by

an Alpha-on-Beryllium fusion reaction, a "neutron howitzer") produced a

Barium residue, which they reasoned was created by the fissioning of the

Uranium nuclei. Subsequent studies revealed that several neutrons were also

released during the fissioning, making available the opportunity for a chain

reaction. Shortly after the discovery of fission, Hitler's Germany invaded

Poland in 1939, starting World War II in Europe, and all such research

http://en.wikipedia.org/wiki/Nuclear_chain_reactionhttp://en.wikipedia.org/wiki/Nuclear_bombhttp://en.wikipedia.org/wiki/Electric_powerhttp://en.wikipedia.org/wiki/Heathttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Nuclear_chain_reactionhttp://en.wikipedia.org/wiki/Nuclear_bombhttp://en.wikipedia.org/wiki/Electric_powerhttp://en.wikipedia.org/wiki/Heathttp://en.wikipedia.org/wiki/Steam_turbine

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became militarily classified. On August 2, 1939 Albert Einstein wrote a letter to

President Franklin D. Roosevelt suggesting that the discovery of Uranium's

fission could lead to the development of "extremely powerful bombs of a new

type", giving impetus to the study of reactors and fission.

Soon after the Chicago Pile, the U.S. military developed nuclear reactors for the

Manhattan Project starting in 1943. The primary purpose for these reactorswas the mass production of plutonium (primarily at the Hanford Site) for

nuclear weapons. Fermi and Leo Szilard applied for a patent on reactors on 19

December, 1944. Its issuance was delayed for 10 years because of wartime

secrecy.

"World's first nuclear power plant" is the claim made by signs at the site of the EBR-

I, which is now a museum near Arco, Idaho. This experimental LMFBR

operated by the U.S. Atomic Energy Commission produced 0.8 kW in a test on

December 20, 1951 and 100 kW (electrical) the following day, having a design

output of 200 kW (electrical).

Besides the military uses of nuclear reactors, there were political reasons to pursue

civilian use of atomic energy. U.S. President Dwight Eisenhower made his

famous Atoms for Peace speech to the UN General Assembly on December 8,

1953. This diplomacy led to the dissemination of reactor technology to U.S.

institutions and worldwide.

The first nuclear power plant built for civil purposes was the AM-1 Obninsk Nuclear

Power Plant, launched on June 27, 1954 in the Soviet Union. It produced

around 5 MW (electrical).

After World War II, the U.S. military sought other uses for nuclear reactor

technology. Research by the Army and the Air Force never came to fruition;

however, the U.S. Navy succeeded when they steamed the USS Nautilus (SSN-

571) on nuclear power January 17, 1955.

The first commercial nuclear power station, Calder Hall in Sellafield, England was

opened in 1956 with an initial capacity of 50 MW (later 200 MW).

The first portable nuclear reactor "Alco PM-2A" used to generate electrical power (2

MW) for Camp Century from 1960.

Classification by type of nuclear reaction

Nuclear fission. Most reactors, and all commercial ones, are based on

nuclear fission. They generally use uranium as fuel, but research on

using thorium is ongoing (an example is the liquid fluoride reactor).

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This article assumes that the technology is nuclear fission unless

otherwise stated. Fission reactors can be divided roughly into two

classes, depending on the energy of the neutrons that are used to

sustain the fission chain reaction:

Thermal reactors use slow or thermal neutrons. Most power reactors are of

this type. These are characterized by neutron moderator materials

that slow neutrons until they approach the average kinetic energy of

the surrounding particles, that is, until they are thermalized.

Thermal neutrons have a far higher probability of fissioning

uranium-235, and a lower probability of capture by uranium-238

than the faster neutrons that result from fission. As well as the

moderator, thermal reactors have fuel (fissionable material),

containments, pressure vessels, shielding, and instrumentation to

monitor and control the reactor's systems.

Fast neutron reactors use fast neutrons to sustain the fission chain reaction.

They are characterized by an absence of moderating material.

Initiating the chain reaction requires enriched uranium (and/or

enrichment with plutonium 239), due to the lower probability of

fissioning U-235, and a higher probability of capture by U-238 (as

compared to a moderated, thermal neutron). Fast reactors have the

potential to produce less transuranic waste because all actinides arefissionable with fast neutrons,[6] but they are more difficult to build

and more expensive to operate. Overall, fast reactors are less

common than thermal reactors in most applications. Some early

power stations were fast reactors, as are some Russian naval

propulsion units. Construction of prototypes is continuing (see fast

breeder or generation IV reactors).

Nuclear fusion. Fusion power is an experimental technology, generally with

hydrogen as fuel. While not currently suitable for power production,Farnsworth-Hirsch fusors are used to produce neutron radiation.

Radioactive decay. Examples include radioisotope thermoelectric

generators and atomic batteries, which generate heat and power by

exploiting passive radioactive decay.

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Classification by moderator material

Used by thermal reactors:Graphite moderated reactors

Water moderated reactors

Heavy water reactors

Light water moderated reactors (LWRs). Light water reactors use ordinary

water to moderate and cool the reactors. When at operating

temperature, if the temperature of the water increases, its density

drops, and fewer neutrons passing through it are slowed enough to

trigger further reactions. That negative feedback stabilizes the

reaction rate. Graphite and heavy water reactors tend to be more

thoroughly thermalised than light water reactors. Due to the extra

thermalization, these types can use natural uranium/unenriched fuel.

Light element moderated reactors. These reactors are moderated by

lithium or beryllium.

Molten salt reactors (MSRs) are moderated by a light elements such as

lithium or beryllium, which are constituents of the coolant/fuel

matrix salts LiF and BeF2.

Liquid metal cooled reactors, such as one whose coolant is a mixture ofLead and Bismuth, may use BeO as a moderator.

Organically moderated reactors (OMR) use biphenyl and terphenyl as

moderator and coolant.

Classification by coolant

In thermal nuclear reactors (LWRs in specific), the coolant acts as a

moderator that must slow down the neutrons before they can beefficiently absorbed by the fuel.Water cooled reactor

Pressurized water reactor (PWR)

A primary characteristic of PWRs is a pressurizer, a specialized pressure

vessel. Most commercial PWRs and naval reactors use pressurizers.

During normal operation, a pressurizer is partially filled with water,

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and a steam bubble is maintained above it by heating the water with

submerged heaters. During normal operation, the pressurizer is

connected to the primary reactor pressure vessel (RPV) and the

pressurizer "bubble" provides an expansion space for changes in

water volume in the reactor. This arrangement also provides a means

of pressure control for the reactor by increasing or decreasing thesteam pressure in the pressurizer using the pressurizer heaters.

Pressurised channels. Channel-type reactors can be refueled under load.

Boiling water reactor (BWR)

BWRs are characterized by boiling water around the fuel rods in the lower

portion of primary reactor pressure vessel. During normal operation,

pressure control is accomplished by controlling the amount of steamflowing from the reactor pressure vessel to the turbine.

Pool-type reactor

Liquid metal cooled reactor. Since water is a moderator, it cannot be used

as a coolant in a fast reactor. Liquid metal coolants have included

sodium, NaK, lead, lead-bismuth eutectic, and in early reactors,

mercury.

Sodium-cooled fast reactor

Lead-cooled fast reactor

Gas cooled reactors are cooled by a circulating inert gas, usually helium.

Nitrogen and carbon dioxide have also been used. Utilization of the

heat varies, depending on the reactor. Some reactors run hot enough

that the gas can directly power a gas turbine. Older designs usually

run the gas through a heat exchanger to make steam for a steam

turbine.

Molten Salt Reactors (MSRs) are cooled by circulating a molten salt,

typically a eutectic mixture of fluoride salts, such as LiF and BeF2. In

a typical MSR, the coolant is also used a matrix in which the fissile

material is dissolved.

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Classification by generation

Generation I reactor

Generation II reactor

Generation III reactorGeneration IV reactor

The "Gen IV"-term was dubbed by the DOE for developing new plant

types in 2000.[7] In 2003 the French CEA was the first to refer to

Gen II types in Nucleonics Week; "Etienne Pochon, CEA director of

nuclear industry support, outlined EPR's improved performance and

enhanced safety features compared to the advanced Generation II

designs on which it was based.".[8] First mentioning of Gen III was

also in 2000 in conjunction with the launch of the GIF plans.

Classification by phase of fuelSolid fueled

Fluid fueled

Gas fueled

Classification by useElectricity

Nuclear power plants

Propulsion, see nuclear propulsion

Nuclear marine propulsion

Various proposed forms of rocket propulsion

Other uses of heat

Desalination

Heat for domestic and industrial heatingHydrogen production for use in a hydrogen economy

Production reactors for transmutation of elements

Breeder reactors. Fast breeder reactors are capable of enriching Uranium

during the fission chain reaction (by converting fertile U-238 to Pu-

239) which allows an operational fast reactor to generate more fissile

material than it consumes. Thus, a breeder reactor, once running,

can be re-fueled with natural or even depleted uranium.

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Creating various radioactive isotopes, such as americium for use in smoke

detectors, and cobalt-60, molybdenum-99 and others, used for

imaging and medical treatment.

Production of materials for nuclear weapons such as weapons-gradeplutonium

Providing a source of neutron radiation (for example with the pulsed

Godiva device) and positron radiation[clarification needed]) (e.g.

neutron activation analysis and potassium-argon dating[clarification

needed])

Research reactor: Typically reactors used for research and training,

materials testing, or the production of radioisotopes for medicine andindustry. These are much smaller than power reactors or those

propelling ships, and many are on university campuses. There are

about 280 such reactors operating, in 56 countries. Some operate

with high-enriched uranium fuel, and international efforts are

underway to substitute low-enriched fuel.

Fission:

When a relatively large fissileatomic nucleus (usually uranium-235 orplutonium-239)

absorbs a neutron it is likely to undergo nuclear fission. The original heavy nucleus splits

into two or more lighter nuclei also releasing kinetic energy, gamma radiation and free

neutrons; collectively known as fission products.[1] A portion of these neutrons may later be

absorbed by other fissile atoms and trigger further fission events, which release more

neutrons, and so on.

The nuclear chain reaction can be controlled by using neutron poisons and neutron

moderators to change the portion of neutrons that will go on to cause more fission. In

nuclear engineering, a neutron moderator is a medium which reduces the velocity of fastneutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain

reaction involving uranium-235.

Commonly used moderators include regular (light) water (75% of the world's reactors),

solid graphite (20% of reactors) and heavy water (5% of reactors). Beryllium has also been

used in some experimental types, and hydrocarbons have been suggested as another

possibility. Increasing or decreasing the rate of fission will also increase or decrease the

energy output of the reactor.

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ComponentsThe control room of NC State's Pulstar Nuclear Reactor.The key components common

to most types of nuclear power plants are:

Nuclear fuel

Nuclear reactor core

Neutron moderator

Neutron poison

Coolant (often the Neutron Moderator and the Coolant are the same, usually both

purified water)

Control rods

Reactor vessel

Boiler feedwater pump

Steam generators (not in BWRs)Steam turbine

Electrical generator

Condenser

Cooling tower (not always required)

Radwaste System (a section of the plant handling radioactive waste)

Refueling Floor

Spent fuel pool

Reactor Protective System (RPS)

Emergency Core Cooling Systems (ECCS)Standby Liquid Control System (emergency boron injection, in BWRs only)

Containment building

Control room

Emergency Operations Facility

Heat Generation

The reactor core generates heat in a number of ways:

The kinetic energy of fission products is converted to thermalenergy when these nuclei collide with nearby atoms.

Some of the gamma rays produced during fission are absorbed bythe reactor in the form of heat.

Heat produced by the radioactive decay of fission products andmaterials that have been activated by neutron absorption. This

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decay heat source will remain for some time even after the reactoris shutdown.

The heat power generated by the nuclear reaction is 1,000,000times that of the equal amount of coal.

Cooling

A cooling source - often water but sometimes a liquid metal - is circulated past the reactor

core to absorb the heat that it generates. The heat is carried away from the reactor and is

then used to generate steam. Most reactor systems employ a cooling system that is

physically separate from the water that will be boiled to produce pressurized steam for the

turbines, but in some reactors the water for the steam turbines is boiled directly by the

reactor core.

Reactivity control

The power output of the reactor is controlled by controlling how many neutrons are able to

create more fission.

Control rods that are made of a nuclear poison are used to absorb neutrons. Absorbing more

neutrons in a control rod means that there are fewer neutrons available to cause fission, so

pushing the control rod deeper into the reactor will reduce its power output, and extracting

the control rod will increase it.

In some reactors, the coolant also acts as a neutron moderator. A moderator increases the

power of the reactor by causing the fast neutrons that are released from fission to lose

energy and become thermal neutrons. Thermal neutrons are more likely than fast neutrons

to cause fission, so more neutron moderation means more power output from the reactors. If

the coolant is a moderator, then temperature changes can affect the density of the

coolant/moderator and therefore change power output. A higher temperature coolant would

be less dense, and therefore a less effective moderator.

In other reactors the coolant acts as a poison by absorbing neutrons in the same way that the

control rods do. In these reactors power output can be increased by heating the coolant,which makes it a less dense poison.

Nuclear reactors generally have automatic and manual systems to insert large amounts of

poison (boron) into the reactor to shut the fission reaction down if unsafe conditions are

detected.

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NUCLEAR POWER GENERATION:

Most reactors, and all commercial ones, are based on nuclearfission. They generally use uranium as fuel, but research on usingthorium is ongoing (an example is the liquid fluoride reactor). Thisarticle assumes that the technology is nuclear fission unless

otherwise stated. Fission reactors can be divided roughly into twoclasses, depending on the energy of the neutrons that are used tosustain the fission chain reaction:

o Thermal reactors use slow or thermal neutrons. Most powerreactors are of this type. These are characterized by neutronmoderator materials that slow neutrons until they approachthe average kinetic energy of the surrounding particles, thatis, until they are thermalized. Thermal neutrons have a farhigher probability of fissioning uranium-235, and a lower

probability of capture by uranium-238 than the faster neutronsthat result from fission. As well as the moderator, thermalreactors have fuel (fissionable material), containments,pressure vessels, shielding, and instrumentation to monitorand control the reactor's systems.

o Fast neutron reactors use fast neutrons to sustain the fissionchain reaction. They are characterized by an absence ofmoderating material. Initiating the chain reaction requiresenriched uranium (and/or enrichment with plutonium 239),

due to the lower probability of fissioning U-235, and a higherprobability of capture by U-238 (as compared to a moderated,thermal neutron). Fast reactors have the potential to produceless transuranic waste because all actinoids are fissionablewith fast neutrons, but they are more difficult to build andmore expensive to operate. Overall, fast reactors are lesscommon than thermal reactors in most applications. Someearly power stations were fast reactors, as are some Russiannaval propulsion units. Construction of prototypes is continuing(see fast breeder or generation IV reactors).

Nuclear fusion. Fusion power is an experimental technology,generally with hydrogen as fuel. While not currently suitable forpower production, Farnsworth-Hirsch fusors are used to produceneutron radiation.

Radioactive decay. Examples include radioisotope thermoelectricgenerators and atomic batteries, which generate heat and power byexploiting passive radioactive decay.

http://en.wikipedia.org/wiki/Uraniumhttp://en.wikipedia.org/wiki/Thoriumhttp://en.wikipedia.org/wiki/Liquid_fluoride_reactorhttp://en.wikipedia.org/wiki/Thermal_reactorhttp://en.wikipedia.org/wiki/Thermal_neutronhttp://en.wikipedia.org/wiki/Neutron_moderatorhttp://en.wikipedia.org/wiki/Neutron_moderatorhttp://en.wikipedia.org/wiki/Fast_neutron_reactorhttp://en.wikipedia.org/wiki/Fast_neutronhttp://en.wikipedia.org/wiki/Neutron_moderatorhttp://en.wikipedia.org/wiki/Enriched_uraniumhttp://en.wikipedia.org/wiki/Plutonium_239http://en.wikipedia.org/wiki/U-235http://en.wikipedia.org/wiki/U-238http://en.wikipedia.org/wiki/Thermal_neutronhttp://en.wikipedia.org/wiki/Transuranichttp://en.wikipedia.org/wiki/Actinoidshttp://en.wikipedia.org/wiki/Fast_breederhttp://en.wikipedia.org/wiki/Generation_IV_reactor#Fast_reactorshttp://en.wikipedia.org/wiki/Nuclear_fusionhttp://en.wikipedia.org/wiki/Fusion_powerhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Farnsworth-Hirsch_fusorhttp://en.wikipedia.org/wiki/Neutron_radiationhttp://en.wikipedia.org/wiki/Radioactive_decayhttp://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generatorhttp://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generatorhttp://en.wikipedia.org/wiki/Atomic_batteryhttp://en.wikipedia.org/wiki/Uraniumhttp://en.wikipedia.org/wiki/Thoriumhttp://en.wikipedia.org/wiki/Liquid_fluoride_reactorhttp://en.wikipedia.org/wiki/Thermal_reactorhttp://en.wikipedia.org/wiki/Thermal_neutronhttp://en.wikipedia.org/wiki/Neutron_moderatorhttp://en.wikipedia.org/wiki/Neutron_moderatorhttp://en.wikipedia.org/wiki/Fast_neutron_reactorhttp://en.wikipedia.org/wiki/Fast_neutronhttp://en.wikipedia.org/wiki/Neutron_moderatorhttp://en.wikipedia.org/wiki/Enriched_uraniumhttp://en.wikipedia.org/wiki/Plutonium_239http://en.wikipedia.org/wiki/U-235http://en.wikipedia.org/wiki/U-238http://en.wikipedia.org/wiki/Thermal_neutronhttp://en.wikipedia.org/wiki/Transuranichttp://en.wikipedia.org/wiki/Actinoidshttp://en.wikipedia.org/wiki/Fast_breederhttp://en.wikipedia.org/wiki/Generation_IV_reactor#Fast_reactorshttp://en.wikipedia.org/wiki/Nuclear_fusionhttp://en.wikipedia.org/wiki/Fusion_powerhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Farnsworth-Hirsch_fusorhttp://en.wikipedia.org/wiki/Neutron_radiationhttp://en.wikipedia.org/wiki/Radioactive_decayhttp://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generatorhttp://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generatorhttp://en.wikipedia.org/wiki/Atomic_battery

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Future and developing technologies

Advanced reactors

More than a dozen advanced reactor designs are in various stages of development. Some are

evolutionary from the PWR, BWRand PHWRdesigns above, some are more radical

departures. The former include the Advanced Boiling Water Reactor(ABWR), two ofwhich are now operating with others under construction, and the plannedpassively safe

ESBWRand AP1000 units (seeNuclear Power 2010 Program).

The Integral Fast Reactor was built, tested and evaluated during the1980s and then retired under the Clinton administration in the1990s due to nuclear non-proliferation policies of theadministration. Recycling spent fuel is the core of its design and ittherefore produces only a fraction of the waste of current reactors.

The Pebble Bed Reactor, a High Temperature Gas Cooled Reactor

(HTGCR), is designed so high temperatures reduce power output bydoppler broadening of the fuel's neutron cross-section. It usesceramic fuels so its safe operating temperatures exceed the power-reduction temperature range. Most designs are cooled by inerthelium. Helium is not subject to steam explosions, resists neutronabsorption leading to radioactivity, and does not dissolvecontaminants that can become radioactive. Typical designs havemore layers (up to 7) of passive containment than light waterreactors (usually 3). A unique feature that may aid safety is that the

fuel-balls actually form the core's mechanism, and are replacedone-by-one as they age. The design of the fuel makes fuelreprocessing expensive.

SSTAR, Small, Sealed, Transportable, Autonomous Reactor is beingprimarily researched and developed in the US, intended as a fastbreeder reactor that is passively safe and could be remotely shutdown in case the suspicion arises that it is being tampered with.

The Clean And Environmentally Safe Advanced Reactor (CAESAR) isa nuclear reactor concept that uses steam as a moderator - thisdesign is still in development.

Subcritical reactors are designed to be safer and more stable, butpose a number of engineering and economic difficulties. Oneexample is the Energy amplifier.

Thorium based reactors. It is possible to convert Thorium-232 intoU-233 in reactors specially designed for the purpose. In this way,

Thorium, which is more plentiful than uranium, can be used to

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breed U-233 nuclear fuel. U-233 is also believed to have favourablenuclear properties as compared to traditionally used U-235,including better neutron economy and lower production of longlived transuranic waste.

o Advanced Heavy Water Reactor A proposed heavy watermoderated nuclear power reactor that will be the nextgeneration design of the PHWR type. Under development inthe Bhabha Atomic Research Centre (BARC).

o KAMINI A unique reactor using Uranium-233 isotope for fuel.Built by BARC and IGCAR Uses thorium.

o India is also building a bigger scale FBTR or fast breederthorium reactor to harness the power with the use of thorium.

Generation IV reactors

Generation IV reactors are a set of theoretical nuclear reactor designs currently being

researched. These designs are generally not expected to be available for commercial

construction before 2030. Current reactors in operation around the world are generally

considered second- or third-generation systems, with the first-generation systems having

been retired some time ago. Research into these reactor types was officially started by the

Generation IV International Forum (GIF) based on eight technology goals. The primary

goals being to improve nuclear safety, improve proliferation resistance, minimize waste and

natural resource utilization, and to decrease the cost to build and run such plants.

Fueling of nuclear reactors:

The amount of energy in the reservoir ofnuclear fuel is frequently expressed in terms of

"full-power days," which is the number of 24-hour periods (days) a reactor is scheduled for

operation at full power output for the generation of heat energy. The number of full-power

days in a reactor's operating cycle (between refueling outage times) is related to the amount

offissileuranium-235 (U-235) contained in the fuel assemblies at the beginning of the

cycle. A higher percentage of U-235 in the core at the beginning of a cycle will permit the

reactor to be run for a greater number of full-power days.

At the end of the operating cycle, the fuel in some of the assemblies is "spent" and is

discharged and replaced with new (fresh) fuel assemblies, although in practice it is the

buildup ofreaction poisons in nuclear fuel that determines the lifetime of nuclear fuel in a

reactor. Long before all possible fission has taken place, the buildup of long-lived neutron

absorbing fission byproducts impedes the chain reaction. The fraction of the reactor's fuel

core replaced during refueling is typically one-fourth for a boiling-water reactor and one-

third for a pressurized-water reactor.

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Not all reactors need to be shut down for refueling; for example,pebble bed reactors,

RBMK reactors, molten salt reactors, Magnox, AGRand CANDU reactors allow fuel to be

shifted through the reactor while it is running. In a CANDU reactor, this also allows

individual fuel elements to be situated within the reactor core that are best suited to the

amount of U-235 in the fuel element.

The amount of energy extracted from nuclear fuel is called its "burn up," which is expressedin terms of the heat energy produced per initial unit of fuel weight. Burn up is commonly

expressed as megawatt days thermal per metric ton of initial heavy metal.

CHALLANGESPort Gibson, Miss. The Claiborne County NAACP is leading a coalition of

environmental, consumer, and human rights organizations that filed a

legal challenge Feb. 12 to plans by Entergy Corp. to build one or morelarge nuclear reactors next to Entergys Grand Gulf nuclear reactor in

Port Gibson.

A.C. Garner, spokesman for the Claiborne County NAACP, said there is a

lack of financial resources to fund adequate emergency services.

"Speaking as a person who served for 14 years as emergency manager

of Claiborne County, I feel people would suffer if there was an accident oract of terrorism at the plant because our emergency planning is not up

to par," Garner said. "It is the responsibility of the fire department, law

enforcement and emergency management to make sure these people

are evacuated if necessary. It is questionable that this could be done

with the present lack of resources."

For the first few years that Grand Gulf operated, Claiborne County

received all the property tax revenues from the nuclear power plantlocated between Vicksburg and Natchez on the Mississippi River. But

Garner said the Mississippi Legislature then passed a bill initiated and

encouraged by Entergy to take away most of the tax funds. Claiborne

County now must share the tax revenues with 47 other counties in

Mississippi.

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"This is a predominantly African American county with about an 84

percent minority population, and 32 percent of the people living below

the poverty line," Garner said. "The legislature is predominantly white.

Removing these tax revenues from Claiborne County is a clear case of

racism. Without adequate funding, it causes a devastating hardship for

the county to fund emergency planning necessary because of thenuclear plant."

The Claiborne County NAACP, the Mississippi Chapter of Sierra Club, the

Nuclear Information and Resource Service (NIRS), and Public Citizen filed

a motion in Washington, D.C. to intervene in what is called the Early Site

Permit for the new nuclear power reactor(s) at Grand Gulf. Through a

company called System Energy Resources, Inc., Entergy is seeking a

permit which would allow the company to "bank" the site for 20 years,

during which time it can choose a reactor type and apply for a combined

construction and operating license.

"Grand Gulf is the only nuclear plant in the country where tax revenues

have been taken from the county that accepts the risk of the facility,"

said Rose Johnson, chair of the Mississippi Chapter of Sierra Club. "The

county doesnt even have a hospital that is open 24 hours. And there is

only one fire station in the entire county. The current situation should

send chills down the spines of anyone who lives within a hundred miles

of Port Gibson. This is the worst example of environmental racism I have

ever seen."

Johnson said an accident or act of sabotage at this facility with its

growing inventory of nuclear waste could contaminate the Mississippi

River and the Gulf of Mexico. "It could wreak havoc on everyonedownstream and downwind, including seafood industries that produce

economic benefits each year totaling many millions of dollars," she said.

Paul Gunter, director of the Reactor Watchdog Program for Washington,

D.C.-based NIRS, said that inadequate planning and infrastructure for

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critical emergency planning services is particularly worrisome because of

the terrorist threat.

"After 9-11, the FBI and Office of Homeland Security clearly warned that

nuclear facilities are prime targets for international terrorism," Gunter

said. "It is critical to educate the public about the ever-increasingdangers and vulnerabilities of nuclear power. Clearly, expanding the

number of nuclear power stations at Grand Gulf also increases the risks

and consequences to public health and safety even beyond Claiborne

County."

Currently 2.4 million pounds of extremely hazardous nuclear waste is

being stored on site because of the lack of a permanent repository for

nuclear waste, with more being added every refueling cycle. The federal

governments proposal for a permanent repository at Yucca Mountain,

Nev., has been strongly opposed by the State of Nevada as scientifically

flawed. Despite concerns about the lack of a permanent disposal site for

nuclear waste, the NRC has taken action to make it easier to license the

siting, construction and operation of new nuclear reactors.

"The Nuclear Regulatory Commission, which must approve licenses for

new nuclear reactors, has streamlined the site permitting process to

make it easier for corporations to get licenses for new nuclear reactors

and harder for the public to challenge them," said Michele Boyd,

legislative representative at Public Citizen in Washington, D.C. "Entergys

plans for new nuclear reactors will create more dangerous radioactive

waste, and further threaten the health and lives of people who live, work,

and attend school in Port Gibson."

CONCLUSION:

Most nuclear reactors use a chain reaction to induce a controlled rate ofnuclear fission in

fissile material, releasing both energy and free neutrons. A reactor consists of an assembly

of nuclear fuel (a reactor core), usually surrounded by a neutron moderatorsuch as water,

graphite, orzirconium hydride, and fitted with mechanisms such as control rods that control

the rate of the reaction.

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The physics ofnuclear fission has several quirks that affect the design and behavior of

nuclear reactors; this article presents a general overview of the physics of nuclear reactors

and their behavior.Uranium enrichment is extremely difficult, because the chemical

properties of235U and 238U are identical, so physical processes such as

gas diffusion or mass spectrometry must be used to separate the

isotopes based on their slightly different mass. Because enrichment is

the main technical hurdle to production of nuclear fuel and simple

nuclear weapons, enrichment technology is politically sensitive.

http://en.wikipedia.org/wiki/Nuclear_fissionhttp://en.wikipedia.org/wiki/Uranium_enrichmenthttp://en.wikipedia.org/w/index.php?title=Gas_diffusion&action=edit&redlink=1http://en.wikipedia.org/wiki/Mass_spectrometerhttp://en.wikipedia.org/wiki/Nuclear_fissionhttp://en.wikipedia.org/wiki/Uranium_enrichmenthttp://en.wikipedia.org/w/index.php?title=Gas_diffusion&action=edit&redlink=1http://en.wikipedia.org/wiki/Mass_spectrometer