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Nuclear Fission, Fusion, and The Atomic Bomb

A chemistry lesson on fission and fusion

David Armor

on 16 April 2015

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Transcript of Nuclear Fission, Fusion, and The Atomic Bomb

Nuclear fission (the splitting of the nucleus of an atom) was first accomplished in 1934 by Italian physicist
Enrico Fermi
. He did this by bombarding uranium atoms with neutrons. At first, he did not realize exactly what he had done.
The nucleus of an atom and radioactive decay became better understood
due to significant contributions from Marie Curie, Pierre Curie,
Ernest Rutherford, and Henri Becquerel (to name a few)
The Beginnings of Fission
The Beginning of Fission
By 1939, a team of scientists repeated Fermi's experiment - this time they came up the correct interpretation of the results

A Hungarian physicist named
Leo Szilard
developed the idea of a nuclear chain reaction that was capable of releasing a tremendous amount of energy at once
The Beginnings of the Atomic Bomb
Leo Szilard drafted this famous letter to President Roosevelt (which was signed by Albert Einstein) suggesting the possibility of an atomic weapon
The Manhattan Project
This enormous top-secret project was started in 1942 with the goal of creating three atomic bombs
(one for a test and two to be used for military purposes)

The project involved dozens of large facilities across the United States but the hub of scientific research was in Los Alamos, New Mexico

General Leslie Groves was in charge of the project while
Robert Oppenheimer
was the lead scientist
Gaseous diffusion facility in Oak Ridge, TN
Nuclear Fission is the process of
using a neutron to split an unstable
heavy nucleus producing nuclei
with smaller mass numbers and
a large amount of energy
The minimum mass of fissionable
material needed to sustain a chain
reaction is called the
critical mass
Uranium-235 is a highly fissionable material

Uranium ore contains about 0.7% U-235 and must be further refined for nuclear power and weapons
The "Fat Man"
21 kiloton detonation
over Nagasaki, Japan
on August 9, 1945

Same design as Trinity

Used a 14 lb Pu-239 core

Caused 40,000 - 70,000
immediate deaths

Japan surrendered shortly
The "Little Boy"
13 kiloton detonation over
Hiroshima, Japan on August 6, 1945

Dropped by the B-29 bomber
named the "Enola Gay"

Caused 80,000 immediate deaths
and 10,000 - 60,000 deaths due to
radiation induced illness
The Trinity Test
Nuclear fusion involves
the combination of
lighter nuclei to form
heavier, more stable
nuclei and a large
amount of energy
Fusion produces more energy per mole than fission

The light and heat produced by the sun and other
stars is the product of nuclear fusion reactions

The amount of activation energy needed to start
the fusion process is tremendous
(temperatures of over 40 million degrees Celsius are typically required)
A modern thermonuclear
warhead uses fisson and fusion
to yield
detonations of up to
By controlling a fission chain reaction, fissionable material can
be used to turn water into steam

The steam is used to drive the turbines of a generator and
electrical energy is produced

Roughly 20% of the electricity in the US is generated from
nuclear fuel (France is near 80%)

Well publicized accidents and the public's lack of knowledge
of nuclear reactors has virtually stopped the growth of
nuclear energy generators in the US
Albert Einstein
determined the relationship between mass and energy in his world famous equation: E = mc^2

Because the value of c is so large (300,000,000 m/s), the amount of energy in just a gram of matter is enormous (90,000,000,000,000 Joules)

Scientists saw nuclear fission (and fusion) as a way to convert a small amount of mass into a large amount of energy - even if only a small fraction of the mass is converted

The Bomb Design
Full transcript