Nuclear fission
You can split the nucleus of an atom into
two smaller fragments with a neutron. This
method usually involves isotopes of
uranium (uranium-235, uranium-233) or
plutonium-239.
Nuclear fusion
You can bring two smaller atoms, usually
hydrogen or hydrogen isotopes
(deuterium, tritium), together to form a
larger one (helium or helium isotopes); at
high temperatures (millions of degrees)
e.g thermonuclear energy from Sun.
Nuclear Energy
E = MC2
Energy from fission of 1 kg of U-235 equal to 20 kilo tons of TNT
Energy from fusion is 1000 times
more than this.
Energy from fission
1 gram of uranium-235 element is equivalent to 2500 Kg of coal
To build an atomic bomb, you need
A source of fissionable or fusionable material
of required critical mass
A triggering device
A way to allow the majority of fuel to fission
or fuse before the explosion occur
Neutron source
Critical Mass
The minimum mass of fissionable material
required to sustain a nuclear fission reaction
In a fission bomb, the fuel must be kept in
separate subcritical masses, which will not
support fission, to prevent premature
detonation
Fission Bombs
To bring the sub critical masses together into a supercritical mass, two techniques are used
Gun-triggered
Implosion
Gun-triggered Fission Bomb
A sphere of U-235 is made around the neutron generator and a small bullet of U-235 is removed
The bullet is placed at the one end of a
long tube with explosives behind it
The sphere is placed at the other end
Gun-triggered Fission Bomb
A barometric-pressure sensor determines the appropriate altitude for detonation and triggers the following sequence of events
Gun-triggered Fission Bomb
The explosives fire and propel the bullet down the barrel.
The bullet strikes the sphere and generator, initiating the fission reaction
The fission reaction begins
The bomb explodes.
TAMPER U-238
SUB-CRITICAL HEMISPHERE U-235
NEUTRON INTIATOR
NEUTRON
REFLECTOR
HE CHARGE
DETONATOR
FUZE
AS SUB-CRITICAL HEMISPHERES FUSE CRITICAL MASS IS ATTAINED
AND WPN DETONATES
GUN TYPE
USED AT HIROSHIMA 6 AUG 45. HAS TWO HEMISPHERES OF SUB
CRITICAL U235 AT OPP ENDS OF A TUBE. ONE IS FIXED THE OTHER IS MOVABLE.
MOVABLE HEMISPHERE IS BACKED BY HE. HE DETONATED. MOVABLE PIECE
PROPELS FWD AT HIGH SPEED. HEMISPHERES FUSE ON IMPACT AND
ATTAIN CRITICAL MASS.
Comments by a Scientist
"If the radiance of a thousand suns were to burst forth at once in the sky, that would be like the splendor of the Mighty One...I am become Death, the shatterer of worlds."
Bhagavad Gita, the sacred Hindu epic recalled by J. Robert Oppenheimer while viewing the first nuclear explosion in Alamagordo, New Mexico, July 16, 1945
Implosion type nuclear fission bomb
The implosion device consists of a sphere
of uranium-235 (tamper) and a plutonium-
239 core surrounded by high explosives.
When the bomb is detonated, this is what
happens
The explosives fires, creating a shock
wave.
The shock wave compresses the core.
The fission reaction begins.
The bomb explodes.
SUB- CRITICAL PLUTONIUM CORE
U-238 TAMPERDETONATOR
INITIATOR
HE LENSES KRYTON
SWITCHES
FIRING
UNIT
KRYTON
SWITCHES
ENERGY WAVES
DIRECTED
INWARD
PU CORE
COMPRESSED
CORE COMPRESSED
TO CRITICAL
MASS
Size of Pu bomb (Nagasaki)
FAT MAN
Stages of fusion Bomb
Fission
Fusion
Fission
Stage 1
Fission:
A small fission bomb is exploded to
provide high temperature (100 million
degrees) for fusion to take place.
Stage 2
Fusion of deuterium and tritium in the
central column leading to release of
enormous amount of energy.
Stage 3
The extremely powerful neutrons from
fusion reaction fissions the fertile isotope
U- 238, leading to further release of
energy.
DETONATOR
HE LENSES
TAMPER
(U-238)
FUSION
MTRL
FISSION TRIGGER
DETONATOR
HE LENSES
TAMPER
(U-238)
FUSION
MTRL
FISSION TRIGGER
HE INITIATED
DETONATOR
HE LENSES
TAMPER
(U-238)
FUSION
MTRL
FISSION TRIGGER
FISSION INITIATED
DETONATOR
HE LENSES
TAMPER
(U-238)
FUSION
MTRL
FISSION TRIGGER
HIGH TEMP INITIATES
FUSION
Fission and fusion bombs
Fission bomb – power up to a few
thousand kilo tons of TNT.
Fusion bomb- 1000 times more powerful
than fission bomb (Practically there is no
upper limit)
Cost of making a bomb
Each bomb costs $5 billion.
20000 crores in Indian rupees
Country Suspected Total Nuclear Weapons
China 400
Israel 200+?
Pakistan 24-48
Country Suspected Total Nuclear Weapons
France 350
Russia ~ 10,000
United Kingdom 185
United States 10,656
Cost of dropping a bomb
Hope
for a
peaceful tomorrow
THANK YOU ALL
HAVE A NICE
WEEKEND
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