NUCLEAR FUSION REACTOR

1101289403TRIDENT ACADEMY OF TECHNOLOGY

WHAT IS NUCLEAR FUSION?

Fusion is the process of uniting light atoms to form a heavier atom

This releases energy as during fusion some uniting mass

is converted into energy Nuclei are positively charged so they repel each

other Energy has to be input to overcome this repulsive

force

+ +FF

WHY ARE WE INTERESTED?

There are great challenges that are associated with fusion, but there are also very large possible benefits

A coal power plant uses 9000 tons of coal a day to produce 1000 MW and emits many pollutants including carbon dioxide.

A fusion power plant would use 2.5 pounds of deuterium and tritium for the same amount of power and would emit only 2 pounds of helium

The amount of lithium contained in a single computer battery along with about half of a bathtub full of water can produce as much energy as 40 tons of coal

HOW IT WORKS? Proton-Proton chain reaction Deuterium-Deuterium chain reaction Deuterium-Tritium chain reaction

Currently only deuterium-Tritium Chain reaction is done. Because it needs comparatively low temperature and pressure to fuse.

H11 + H1

2 He4 + n1 + Q Q = 13.5 Mev/fusion

CONDITION FOR NEUCLEAR FUSION

High temperature - The high temperature gives the hydrogen atoms enough energy to overcome the electrical repulsion between the protons.

Fusion requires temperatures about 70 million Kelvin 

High pressure - Pressure squeezes the hydrogen atoms together. They must be within 1x10-15 meters of each other to fuse.

FUSION REACTOR

Fusion reactor obtains power from fusion reaction. The fusion process is done in two stages.

Internal confinement Magnetic confinement

INTERNAL CONFINEMENTInternal confinement is a process which is used to initiate nuclear fusion reactions by heating and compressing a fuel.High powered Lasers are used to force nuclear fusion of tiny pellets of a deuterium-tritium mixture by zapping them with such a high energy density that they will fuse before they have time to move away from each other.

MAGNETIC CONFINEMENT

Magnetic Confinement is the process of holding the superheated plasma without letting it touched with the wall of the fusion chamber.

At initiation of fusion reaction the temperature reaches at millions of degree of Celsius. There is no material container to withstand this amount of temperature.

To overcome this problem a strong magnetic field is required to hold and move the plasma by keeping distance to the container.

Magnetic confinement fusion attempts to create the conditions needed for fusion energy pro-duction by using the electrical conductivity of the plasma to contain it with magnetic fields. It is done by balancing plasma pressure with the magnetic field.

PE= N1.N2.v.б(T).E= q.V.B

PE - Total energy liberated from fusion reaction.N1 and N2-Number density of fused atomsv - Average velocity of plasma particlesб(T)-Nuclear cross section at temperature Tq - charge densityV - velocity of rotating magnetic fieldB - Magnetic field strength

COMPONENTS OF FUSION CHAMBER

Vacuum vessel Breeder blanket Shielding Magnet system Cryostat Cooling system

Vacuum Vessel: It is a spherical vessel made of tungsten alloy vacuum vessel is to provide a hermetically

sealed plasma container.   vessel is a double walled structure with poloidal

and toroidal stiffening ribs between 60 millimeters (2.4 in) thick shells to reinforce the vessel structure.

Ribs also form the flow passages for the cooling water.

The space between the double walls will be filled with shield structures made of stainless steel.

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The inner surfaces of the vessel will act as the interface with breeder modules containing the breeder blanket component.

These modules will provide shielding from the high-energy neutrons produced by the fusion reactions and some will also be used for tritium breeding

Breeder Blanket: This component, located adjacent to the

vacuum vessel, serves to produce tritium through reaction of 6Li isotopes with high energy neutrons from the plasma.

Breeder blanket includes helium cooled pebble bed (HCPB) methods.

36Li + 0

1n 24He + 1

3H +4.3Mev

SHIELDING The fast moving neutrons are stopped by the

heavy element sheet as lead. The total vessel is kept inside a concrete

chamber to stop any leakage of gamma rays.

Magnet System: The poloidal coil will

use superconducting niobium-tin to carry 46 kA and produce a field of up to 13.5 tesla.

 The toroidal field coils will also use niobium-tin. At their maximum field strength of 11.8 tesla, they will be able to store 41 gigajoules of energy.

Lower field magnets use niobium-titanium for their superconducting element All coils can be operated at 80KA of

maximum value.

The cryostat is a large, stainless steel structure surrounding the vacuum vessel and superconducting magnets, providing a super-cool, vacuum environment. It is made up of a single wall cylindrical construction, reinforced by horizontal and vertical ribs.

The cryostat has many openings, which provide access to the vacuum vessel for cooling systems, magnet feeders, auxiliary heating, diagnostics, and the removal of blanket and diverter parts.

Cryostat

The heat will be removed by a primary water cooling loop

The 10 loop is cooled by water cooled heat exchanger and cooling tower.

Further cooling is done by a liquid nitrogen  system which provides a further 1,300 kW of cooling .

Cooling system

PLANT OPERATION

ADVANTAGES The deuterium and lithium can last for more than

million years. No chain reaction. Easy to control the process. There is no chemical combustion products in a

fusion reaction, and therefore no contribution to atmospheric or water pollution.

No long lived radioactive materials are produced. Radioactivity is produced by neutrons interacting with the reactor structure, but decays rapidly with the proper selection of low-activation materials.

LIMITATION Large amount of energy is required to start the

fusion process. Difficulties in sustaining the fusion reaction. Unproven at anything resembling commercial

scale. Commercial power plants would be extremely

expensive to build.

FUTURE RESEARCH Deuterium-Deuterium reaction and proton-proton is

to be done in near future to obtain more energy. Research is going on to sustain the superheated

plasma for a long period of time. The emphasis is given on the cold fusion in which

the fusion can be done at room temperature.In cold fusion palladium cathode and

platinum anode is placed in heavy water which contain which contain 99% deuterium and small current is passed. The deuterium is absorbed and pressed by the crystal lattice of the palladium and significant amount of heat is generated.

CONCLUSIONThe fusion reactor is not commercially

operated till now. It is only in experimental stage. There are some factors like plasma sustaining problem, initiation problem, temperature handling problem etc which are yet to be overcome. But fusion reactor is an huge step toward s the limitless energy which can satisfied the power requirement in the future and the existing reactors opens a lot of paths for further research.

REFERENCES E. MOSES, T. DIAZ DE LA RUBIA, J. F.LATKOWSKI, et

al., “A Sustainable Nuclear Fuel Cycle Based On Laser Inertial Fusion Energy(LIFE),” Fusion Science and Technology, 56, 2, 566-572 (2009).

K. J. KRAMER, M. FRATONI, J. F. LATKOWSKI, et al., "Fusion-Fission Blanket Options for the Laser Inertial Fusion Energy (LIFE) Engine," this issue (2011).

R. MILES, M. SPAETH, K. MANES, "Challenge Surrounding the Injection and Arrival of Targets at IFE Target Chamber Center," this issue (2011).

Initiation of ITER Fusion project France(2010-2020)

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