Download Basics of Nuclear Physics and Energy

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Nuclear Physics & Energy
The atom
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The basics of atomic nucleus - 1
•The atomic nucleus was discovered by Earnest
Rutherford in 1911.
•A nucleus of an element is represented as ZXA
•17Cl35
•The nucleus consists of the elementary particles,
protons and neutrons which are known as nucleons.
•A proton has positive charge of the same magnitude
as that of electron and its rest mass is about 1836
times the mass of an electron.
•The charge of a nucleus is due to the protons present
in it.
•Each proton has a positive charge equal to 1.6 × 10−19
Coulomb.
The basics of atomic nucleus - 2
•Atomic mass unit = one twelfth of the mass of carbon
atom 6C12
•1 amu = 1.66 × 10−27 kg
•The mass of a proton, mp = 1.007276 amu
•The mass of a electron, me = 0.000549 amu
•mass of the hydrogen atom = 1.007825 amu
•The mass of a neutron, mn = 1.008665 amu
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The energy equivalence of one amu
under e = mc2
m = 1 amu = 1.66 × 10−27 kg
c = 3 × 108 ms−1
∴ E = 1.66 × 10−27 × (3 × 108)2 J
Since, 1 eV = 1.6 × 10−19 joule
∴ E= 931 × 106 eV or 931 million electronvolt = 931 MeV
Thus, energy equivalent of 1 amu = 931 MeV
Nuclear mass defect and binding
energy
Mass defect: From the measurement of mass by mass
spectrometers, it is found that the mass of a stable nucleus (m) is
less than the total mass of the nucleons. This difference in mass is
denoted by ∆m and called the mass defect.
The binding energy : When the protons and neutrons combine to
form a nucleus, the mass that disappears (mass defect, ∆m) is
converted into an equivalent amount of energy (∆mc2). This energy
is called the binding energy (BE) of the nucleus.
Binding energy maximum of 8.8 MeV at A=56; 26Fe56
Hence, iron nucleus is the most stable.
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Nuclear Fission - 1
In 1939, German scientists Otto Hahn and F. Strassman discovered
that when uranium nucleus is bombarded with a neutron, it breaks up
into two fragments of comparable masses with the release of energy
Nuclear Fission - 2
235
92U
+ 0n1 → 56Ba141 + 36Kr92 + 3 0n1 + Energy
In this fission reaction:
As, 1 amu = 931 MeV, energy released in a fission = 0.225303
× 931 ≅ 200 MeV
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Nuclear Fission - 3
If we can fission all the nuclei in 1kg of U235 we
would release 4.9x1013J of energy.
Put in every day terms, this is sufficient meet the
power demands of a house with a 150 kW (150
unit) daily consumption continuously for more
than 300 years.
Chain reaction
1. Uncontrolled chain reaction: Explain
2. Controlled chain reaction: Explain
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Critical size and critical mass
Critical size of a system containing a fissile material is defined
as the minimum size in which at least one neutron is available
for further fission reaction.
The mass of the fissile material at the critical size is called
critical mass. (about 15 kg for pure U235)
Artificial transmutation
conversion of one element into another by artificial methods
7N
14
+ 2He4 → 8O17 + 1H1
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