Nuclear Fission and Nuclear Fission and Nuclear FusionNuclear Fusion

Main DifferenceMain Difference

Nuclear FissionNuclear Fission the splitting of an atom into two or the splitting of an atom into two or

more smaller onesmore smaller ones

Nuclear FusionNuclear Fusion the fusing of two or more smaller the fusing of two or more smaller

atoms into a larger one.atoms into a larger one.

Nuclear FusionNuclear Fusion

the reaction in which two or more nuclei the reaction in which two or more nuclei combine together to form a combine together to form a new element with higher atomic new element with higher atomic number (more protons in the nucleus). number (more protons in the nucleus).

The energy released in fusion is related to The energy released in fusion is related to E = mc 2 (Einstein’s famous energy-mass E = mc 2 (Einstein’s famous energy-mass equation). equation).

On earth, the most likely fusion reaction is On earth, the most likely fusion reaction is Deuterium–Tritium reaction. Deuterium–Tritium reaction.

  2 1Deuterium + 3 1Tritium = 42He + 102 1Deuterium + 3 1Tritium = 42He + 10nn +  + 17.6 MeV17.6 MeV

Fusion of deuterium with tritium creating helium-4, freeing a neutron,

and releasing 17.59 MeV of energy.

Nuclear FissionNuclear Fission

the splitting of a massive nucleus into the splitting of a massive nucleus into photons in the form of gamma rays, free photons in the form of gamma rays, free neutrons, and other subatomic particles. neutrons, and other subatomic particles.

In a typical nuclear reaction In a typical nuclear reaction involving 235U and a neutron:involving 235U and a neutron:

23592U + 23592U + nn = 23692U = 23692U

23692U = 14456Ba + 89 36Kr + 323692U = 14456Ba + 89 36Kr + 3nn + 177  + 177 MeVMeV

A fission reactionA fission reaction

Physics behind both fission and Physics behind both fission and fusion processesfusion processes

The more the binding energy held The more the binding energy held within the bonds of an atom, more within the bonds of an atom, more stable is an atom. stable is an atom.

Binding energy - the amount of energy held Binding energy - the amount of energy held within the bonds of the atoms within the bonds of the atoms

Conditions for fission reactionsConditions for fission reactions

Critical mass Critical mass of the substance (the of the substance (the minimum amount of mass is required minimum amount of mass is required for fission to be self-sustaining).for fission to be self-sustaining).

A relatively A relatively slow neutronslow neutron is required is required to initiate the process. to initiate the process.

Chain ReactionChain Reaction

Both fission and fusion nuclear Both fission and fusion nuclear reactions are reactions are chain reactionschain reactions..

Fission:Fission:• Fission chain reactions occur because of Fission chain reactions occur because of

interactions between neutrons and interactions between neutrons and fissile isotopes and a fusion chain fissile isotopes and a fusion chain reaction occurs under extreme pressure reaction occurs under extreme pressure and temperature conditions, which are and temperature conditions, which are maintained by the energy released in the maintained by the energy released in the fusion process.fusion process.

Energy ratiosEnergy ratios

The energy released by fusion is The energy released by fusion is three to four times greater than the three to four times greater than the energy released by fission. This is energy released by fission. This is because the amount of mass because the amount of mass transformed into energy is that much transformed into energy is that much greater in a fusion reaction than in a greater in a fusion reaction than in a fission reaction.fission reaction.

Natural occurrenceNatural occurrence

Fusion:Fusion:- stars - stars - first achieved in the explosion of the - first achieved in the explosion of the

Hydrogen bomb Hydrogen bomb

Fission:Fission:- does not normally occur in nature does not normally occur in nature - has occurred in natural reactors has occurred in natural reactors

EffectsEffects

Fission: Fission:

nuclear meltdown highly nuclear meltdown highly radioactive particles in the atmosphere radioactive particles in the atmosphere

Fusion:Fusion:

- reaction would stop automatically- reaction would stop automatically

- the vaporization of anything in the - the vaporization of anything in the immediate vicinity of the reaction immediate vicinity of the reaction

Energy RequirementEnergy Requirement

It takes less energy to split two It takes less energy to split two atoms with fission than it does to atoms with fission than it does to fuse two atoms, which is why fission fuse two atoms, which is why fission reactors were developed first, and reactors were developed first, and why fusion reactors have not been why fusion reactors have not been developed yet.developed yet.

CostCost

Fission: Fission: a. transformation from heat energy a. transformation from heat energy

to electrical energy to electrical energy b. clean-up and storage of nuclear b. clean-up and storage of nuclear

waste waste Fusion: Fusion: a. the atoms must be confined in a. the atoms must be confined in

the magnetic field and raised to a the magnetic field and raised to a temperature of 100 million Kelvin or temperature of 100 million Kelvin or more. This takes lot of electricity. more. This takes lot of electricity.

Advantages of fusion over fissionAdvantages of fusion over fission

In case of fusion reactions, fusion reactors In case of fusion reactions, fusion reactors cannot sustain a chain reaction so they cannot sustain a chain reaction so they can never melt down like fission reactors. can never melt down like fission reactors. Fusion reaction produces very less or, if Fusion reaction produces very less or, if the right atoms are chosen, no radioactive the right atoms are chosen, no radioactive waste. In case of nuclear fission large waste. In case of nuclear fission large radioactive waste is produced and disposal radioactive waste is produced and disposal of radioactive waste is a complicated of radioactive waste is a complicated problem. For nuclear power, fusion is the problem. For nuclear power, fusion is the better choice.better choice.

Nuclear Fission Nuclear Fusion

Definition: Fission is the splitting of a large atom into two or more smaller ones.

Fusion is the fusing of two or more lighter atoms into a larger one.

Natural occurrence of the process:

Fission reaction does not normally occur in nature.

Fusion occurs in stars, such as the sun.

Byproducts of the reaction:

Fission produces many highly radioactive particles.

Few radioactive particles are produced by fusion reaction, but if a fission "trigger" is used, radioactive particles will result from that.

Conditions: Critical mass of the substance and high-speed neutrons are required.

High density, high temperature environment are required.

Energy Requirement:

Takes little energy to split two atoms in a fission reaction.

Extremely high energy is required to bring two or more protons close enough that nuclear forces overcome their electrostatic repulsion.

Energy Released: The energy released by fission is a million times greater than that released in chemical reactions; but lower than the energy released by nuclear fusion.

The energy released by fusion is three to four times greater than the energy released by fission.

Nuclear weapon: One class of nuclear weapon is a fission bomb, also known as anatomic bomb or atom bomb.

One class of nuclear weapon is the hydrogen bomb, which uses a fission reaction to "trigger" a fusion reaction.