NUCLEAR REACTIONS

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INDEX INTRODUCTION ENERGY FROM NUCLEUS NUCLEAR FISSION NUCLEAR REACTOR NUCLEAR FUSION CONTROLLED THERMONUCLEAR FUSION

INTRODUCTION In 1919 it occurred to Rutherford that it

ought to be possible to penetrate a nucleus with a massive high-speed particle such as alpha-particles and thereby producing a nucleus with greater mass number or induce an artificial disintegration.Rutherford was

successful in bombarding nitrogen with

alpha-particles and obtaining as a result an oxygen nucleus and a proton according to the following reaction :

N + He O + HWhere, N = Nitrogen He = Helium O = Oxygen H = HydrogenSuch a process is termed as a NUCLEAR REACTION.

Nuclear Reaction EnergyIn a nuclear reaction,the sum of the initial atomic numbers is equal to the sum of the final atomic numbers,by the conservation of charge.The sum of the initial mass numbers is also equal to the sum of the final mass numbers,but the initial rest masses not equal to the final rest mass. The difference between the rest masses is equal to the NUCLEAR REACTION ENERGY.

ENERGY FROM NUCLEUSWhen we get energy from coal by burning the fuel ,we are doing so by tinkering withatoms of carbon and oxygen,rearrangingtheir outer electrons into more stable combi-nations.When we get energy from uranium(a highly radioactive element)in the nuclear reactor ,we are again burning a fuel,but then we are tinkering with its nucleus,rearrangingIts nucleons into more stable configuration.

In both atomic and nuclear burning,the release of energy is accompanied by a decrease in mass according to the equation: Q = - mc^2Thus,for the same energy release,a muchlarger fraction of the available mass(by afactor of few millions)is consumed in achemical fuel than in a nuclear fuel.

NUCLEAR FISSIONAfter the discovery of neutron by Chadwick,Enrico Fermi found that when neutrons arebombarded on various elements,new radio-active elements are produced. He predicted that the neutron,being uncharged,would bea useful nuclear projectile;unlike the protonsor alpha-particle,it experiences no repulsiveCoulomb force when it nears a nuclear surface.

In late 1930’s ,the physicist Lise Meitner andChemists Otto Hann and Fritz Strassman,Bombarded solutions of uranium salts with The (slow moving neutronsIn thermal equilibrium with the surrounding Matter at room temperature,with a mean Kinetic energy of only about 0.04 eV,and areUseful projectiles in nuclear studies).They Found that after the bombardment a number Of new radionuclides were produced.

thermal neutrons

For Hann & Strassmann,it was rather a mystery as to how this middle-mass element(Z=56)could be produced by the bombardem-ent of uranium(Z=92)with neutrons.Meitner& her nephew Otto Frisch solved this puzzle.They suggested the mechanism by which auranium nucleus,having absorbed a thermalneutron,could split,with the release of energy,into roghly two equal parts,one of which mightwell be barium.Frisch named it as FISSION.

Fragment mass number A

YIELD

The distribution by mass number of the fragments that are found when many fission events of uranium 235 are examined.