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