Radioactivity and Nuclear Energy

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Radioactivity and Nuclear Energy

This article deals with ‘Radioactivity and Nuclear Energy.’ This is part of our series on ‘Science and Technology’ which is important pillar of GS-3 syllabus . For more articles , you can click here

Radioactivity and Nuclear Energy

  • The property by virtue of which a heavy nucleus of element disintegrate itself into smaller nuclei along with alpha, beta & gamma rays without being forced by any external agent to do so, is termed as radioactivity
  • The phenomenon of radioactivity is natural and cant be stopped
  • Found that – all atoms having more than 83 protons + neutron to proton ratio  more than 1 are unstable & in order to achieve greater stability , these unstable nuclei disintegrate spontaneously with emission of Alpha, Beta & Gamma Rays .
  • It was discovered by Henry Becquerel

Reason = Nuclear Forces

  • Inside Nucleus , positively charged Protons & Neutral Neutrons are present . Hence, if only Electrostatic Force is there then Nucleus must have split apart due to repulsive forces but this is not the case & Nucleus is stable
  • Other Force called Nuclear Force is working here . THIS IS ATTRACTIVE FORCE EXISTING BETWEEN PROTON & PROTON and PROTON & NEUTRON.  BUT THIS FORCE ACTS AT VERY SMALL DISTANCE
  • Inside Nucleus, Nuclear Forces overpowers Electrostatic Forces

Alpha, Beta & Gamma Radiations

  Alpha  Beta Gamma
  Similar to Helium Neuclei (He (2,4)) and generally emitted by large nucleus These are fast energy electrons   Gamma Radiations are electromagnetic radiations of high frequency Generally emitted by unstable atoms to become stable by releasing energy
Pentration Can penetrate  5 cm air only Can penetrate air and paper Can penetrate most things except thick sheet of lead or very thick concrete wall  
Mass Heaviest (4 amu) Lighter (9.1 X 10^-31 kg) Massless    
Speed Around 1/100 of speed of light 33% to 99% speed of light Equal to speed of light
Ionising power Maximum due to maximum charge (+2) and maximum mass Intermediate between beta & gamma Minimum due to zero charge
Effect on Photographic plate Produce smaller effect More effect Maximum effect
Effect of Electric and magnetic field Show deflection Show deflection Don’t show any deflection
Effect on human body Cause burning effect Can cause a shock on longer exposure Can cause cancer

Transmutation

  • Altering one element to another
  • Reason = Natural Radioactivity , Artificial Transmutation etc
  • Artificial Transmutation is used to obtain elements with Atomic number greater than 92

Half Age

It measures the time it takes for a given amount of the radioactive substance to become reduced to half as a consequence of decay and therefore , the emission of  radiation .

  • Carbon Dating
    • Technique of estimating age of the remains of a once living organism such as a plant or animal
    • By measuring the radioactivity of its C-14 Content (half life of C-14 is 5730 years)
    • Ratio of C-14 / C-12 in nature is  1/106
  • Uranium Dating
    • Used for Dating of older but non living things eg Rocks
    • Age of Rocks from moon has been estimated to be 4.6 X 10^9 years which is nearly time of earths origin

Isotope, Isobars & Isoneutrons

  • Atomic Number(Z) = Number of Protons
  • Mass Number (A) = Number of Neutrons & Protons
  • Isotope
    • Nuclides having same Atomic Number but different Mass Number
    • Eg U (92,235) & U (92,238 ) + C-12 & C-14
    • Generally isotopes don’t have different names except isotopes of Hydrogen named Protium (H(1,1) , Dueterium (H (1,2)) & Tritium (H(1,3))
  • Isobars
    • Nuclides having same Mass Number but different Atomic Numbers
    • Eg : K (19,40) & Ca (20,40)  + C (6,14) & N (7,14)
    • They have different names
  • Isoneutronic
    • Nuclides having same number of neutrons
    • Eg : C (6,14) & O(8,16) : Both having 8 neutrons
    • Eg : H (1,3) & He (2,4) : both have 2 neutrons

Nuclear Fission

Fission

  • Splitting up of nucleus of a heavy atom to two roughly equal fragments accompanied by release of energy

U(235,92) + n (1,0) —> Ba(141,56) + Kr(96,36) + 3n (1,0)

Uranium (92,235) + neutron —> Barium + Krypton + 3 neutron + Energy

Total mass of Reactants is More than Total mass of Products & EXCESS mass has converted to energy

  • Using Einsteins Mass – Energy Relation

                                                       E = mc^2

  • Energy released from 1 nucleus U235 is nearly 93 Mega Electron Volt (1eV = 1.6 X 10^ -19 ) ( fairly large energy)
  • Note : 1 gram uranium can produce energy equivalent to 3 ton coal.
  • If neutrons produced in fission reaction are slowed , they may produce futher fission & start chain reaction
  • Enriched Uranium
    • For an atomic Bomb , fissile U-235 is needed
    • But in Natural Uranium , U-235 is just 0.7% & rest is U-238 (fertile but not fissile)
    • Process of increasing amount of U-235 is called Enrichment . For this, Centrifugation Technique is used .
    • For Nuclear Reactors ,  3-10% enriched U-235 required & for Atom Bombs,  highly enriched Uranium-235 as high as 90% is required

We will read more about Nuclear Fission, Nuclear Reactors for fission reactions and other aspects in the next articles.

Nuclear Fusion

Nuclear Fusion Reactor

  • In Nuclear Fusion reaction, two small atoms combine to form bigger atom and release large amount of energy in the process.
  • Nuclear Fusion needs very high energy and can be carried at 10^7 K temperature (which is difficult to achieve and even more difficult to maintain)

H(1,2) + H (1,2)  —- @ 10^7 k —->  He (2,4) + Energy

  • Reactor is based on Tokomak Technology . Tokomak is Russian word for chamber enclosed by powerful magnets
  • These magnets exert strong  repulsive force thus concentrating the mass at the centre leading  to rise of temperature
  • Difficulties in the nuclear fusion reactions :
    • Difficult to reach the critical temperature
    • If the critical temperature is raised even then it is  difficult to maintain the critical temperature  in a controlled reaction

Advantages of the Nuclear fusion  over Nuclear fission

  • Fusion can provide more energy with same amount of mass
  • Radioactive pollution generated from fission is not there in fusion
  • Fusion reactors are more safe than fission reactors because in case of the accident temperature automatically falls than the temperature required for continuation of fusion
  • Waste generated on fusion can be easily handled as compared to the waste generated in fission
  • Fuel for the nuclear fusion is easily available than  fission
  • possibilities of  unlimited  clean  energy,  and  will  avert  the major  environmental  impacts  of  global warming.

Nuclear Fusion Research in India

  • Indian Plasma Research Institute , Gandhi Nagar (Gujarat) has designed and fabricated a Nuclear Fusion based reactor called Aditya
  • India is already a member in ITER program of EU.  Institute of Plasma Research & SAHA Institute of Nuclear Physics represent India at  ITER
  • India should work actively for fusion based nuclear reactor as it would be the energy of future.

ITER (International Thermonuclear Experimental Research Project )

  • Aka Artificial Sun
  • At Cadarache , France
  • Aims to harness the nuclear fusion energy for peaceful purposes
  • 50 MW energy will be provided and 500 MW energy can be obtained ir efficiency of 10 times.
  • It is an International program with participants 
EU Russia India South Korea
USA China Japan  
  • 45% of the total cost being borne by EU rest divided among other participants
  • Research reactor is expected to be operational by 2015 (what happened , don’t know)
  • Full scale commercial exploitation of fusion energy is expected by 2050
  • It successful , it will provide source of unlimited power in future

2019 : Experimental Advanced Superconducting Tokamak (EAST) reactor => China close to making it’s artificial sun

This concludes our article on Radioactivity and Nuclear Energy. For more articles on Science and Technology, click below

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