Nuclear fission brief

1. Prepared By
Irtasam
FA15-BME-014
Group Members
FA15-BME-014
FA15-BME-016
FA15-BME-034
FA15-BME-046
FA15-BME-054

2. A Brief History
• Otto Hahn:
Germany-Nobel Prize winner famous for his discovery of nuclear fission.
• Fritz Strassmann:
German chemist who, with Otto Hahn in 1938, identified barium
in the residue after bombarding uranium with neutrons.
• Enrico Fermi:
Italy-Nobel Prize winner and famous for creating the world's first
nuclear chain reaction.

3. What is Fission?
•Fission is another word for splitting.
•It means division or splitting into two or more parts.
•In general, If a heavy particle or object splits into two or
more parts or fragments it is called fission.

4. Analogy
• Nuclear Fission is similar to a liquid drop when excess
energy is added to it .
•When a liquid drop is given vibratory motion it
undergoes elongation and compression.
•When vibrations become very fast the drop splits into
two.
•Similar is the case of Uranium-235

5. Liquid Drop Model Fission

6. Nuclear Fission
• When a nucleus(usually Uranium-235 fissions, it splits into several smaller
fragments.
• These fragments, or fission products, are about equal to half the original
mass.
• Two or three neutrons are also emitted.
• The sum of the masses of these fragments is less than the original mass.
• This 'missing' mass has been converted into energy according to Einstein's
equation.
• Fission can occur when a nucleus of a heavy atom captures a neutron, or it
can happen spontaneously.

7. Diagram
+Energy

8. Neutrons may
1 - Cause another fission by colliding with a U235 nucleus
2 - Be absorbed in other material
3 - Lost in the system
If sufficient neutrons are present, we may achieve a chain reaction
Each split (fission) is
accompanied by a large
quantity of E-N-E-R-G-Y
• Creates two smaller nuclides and free neutrons.
• The free neutrons potentially collide with nearby U235 nuclei

9. Steps In Nuclear Fission
• The 235U nucleus captures a thermal (slow-moving) neutron.
• The capture results in the formation of 236U*, and the excess
energy of this nucleus causes it to undergo violent oscillations.
• The 236U* nucleus becomes highly elongated, and the force of
repulsion between protons in the two halves of the dumbbell-
shaped nucleus tends to increase the distortion.
• The nucleus splits into two fragments, emitting several neutrons
in the process.

10. FISSION CAN BE USED
• GOOD
• A controlled chain reaction in a reactor used in nuclear power
plants to produce electricity.
• EVIL
• An uncontrolled chain reaction is used to create incredibly
powerful weapons – the atomic bombs dropped on Japan.

11. U
235
92n
1
0
A neutron travels at slow speed towards a uranium-
235 nucleus
The Fission Process

12. U
235
92n
1
0
A neutron travels at slow speed towards a uranium-
235 nucleus
The Fission Process

13. U
235
92n
1
0
A neutron travels at slow speed towards a uranium-
235 nucleus
The Fission Process

14. U
235
92n
1
0
The neutron strikes the nucleus which then captures
the neutron
The Fission Process

15. U
236
92
The nucleus changes from being uranium-235 to
uranium-236 as it has captured a neutron
The Fission Process

16. The uranium-236 nucleus formed is very unstable
 It transforms into an elongated shape for a short
time
The Fission Process

17. The Fission Process
 It transforms into an elongated shape for a short
time
The uranium-236 nucleus formed is very unstable

18. The Fission Process
 It transforms into an elongated shape for a short
time
The uranium-236 nucleus formed is very unstable

19. It then splits into 2 fission fragments and releases
neutrons
141
56Ba
92
36Kr
n
1
0
n
1
0
n
1
0
The Fission Process

20. It then splits into 2 fission fragments and releases
neutrons
141
56Ba
92
36Kr
n
1
0
n
1
0
n
1
0
The Fission Process

21. It then splits into 2 fission fragments and releases
neutrons
141
56Ba
92
36Kr
n
1
0
n
1
0
n
1
0
The Fission Process

22. 141
56Ba
92
36Kr n
1
0
n
1
0
n
1
0
The Fission Process
The mass that was “lost” became energy