Physical reactionInvolves a change in the nucleus of an atomTwo types –Fission and fusion.Source – Mass of the nucleusReleased mainly in the form of heat energyKnown as atomic energy
17Cl35 + 0n1 15P32 + 2He4 + High energy When Uranium 235 atoms are bombarded with slow moving neutrons,the heavy uranium nucleus breaks up to produce two medium-weight atoms ,neutrons and a tremendous amount of energy. 235 + 0n1 139 + 94 + 30n1 + High energy U92 56Ba 36Kr
Fission means ‘to split’ German scientist otto hann and strassmandiscovered that when a 92U235 nucleus is bombardedby thermal neutrons,it splits up into two smalllernuclei of barium and Krypton along with the releaseof three neutrons The process in which the heavy nucleus of a radioactiveatom (such as uranium,thorium and plutonium) splits upinto smaller nuclei when bombarded with low energyneutrons is known as nuclear fission.
The sum of masses of the smaller nuclei formed in afission reaction is a little less than that of the mass of theoriginal heavy nucleusSo,there is a small loss of mass in the nuclear fissionprocess. This energy is used for generating electricity.
Neutrons may: 1 - Cause another fission by colliding with a U235 nucleus • Creates two smaller nuclides and free neutrons • The free neutrons potentially collide with nearby U235 nuclei • May cause the nuclide to split as wellEach split (fission) isaccompanied by alarge quantity of E-N-E-R-G-Y
Chain reaction When the neutrons in the fission reaction continuouslybombard with heavy nuclei then , a continuous selfsustaining nuclear chain reaction happens. Sometimes,I t becomes uncontrolllable and that isthe atom bomb. To control it boron rods are used because boron hasthe property to absorb neutrons.
Review Nuclear fission: A large nucleus splits into several small nuclei when impacted by a neutron, and energy is released in this processNuclear fusion:Several small nuclei fusetogether and releaseenergy.
AdvantagesProduces tremendous energy from a small amountof nuclear fuel.Once the nuclear fuel is filled,the plant can go foryears together.Does not produce greenhouse gases like CO2
DisadvantagesDifficult to dispose the radioactive waste from thenuclear fission reaction.Risk of accidents in Nuclear reactorsHigh cost of installation of nuclear power plantsand limited availability of uranium.