History of Nuclear Weapons

1
History of Nuclear Weapons

• Lupei Zhu

2
Topics

• Important discoveries before WWII that led to
  nuclear weapons.
• The Manhattan Project.
• Nuclear weapon attacks on Japan in WWII.
• Current states with nuclear weapons.

3
Important discoveries pre-WWII

• By the end of 19th century, people knew the all
  matter is made of basic substances called
  elements. Each element consists of a particular
  type of particle atom. But they believed that
  atom is the smallest particle that can not be
  divided further.
• In 1896 French physicist Antoine Henri
  Becquerel's experiments led to the discovery of
  radioactivity atomic nucleus of certain elements
  emit energetic particles (rays). He shared the
  1903 Nobel Prize with Pierre and Marie Curie.

4
Important discoveries pre-WWII

• In 1899  Ernest Rutherford discovered two kinds
  of rays emitting from radium. The first is
  positively charged and he called alpha rays
  (turned out late to be the helium nucleus, which
  consists of two protons and two neutrons) the
  more penetrating negative charged rays he called
  beta rays (electrons).
• The third one, the gamma ray, has no charge and
  late found to be photon (light).

5
Important discoveries pre-WWII

• In June, 1919, Rutherford bombarded nitrogen gas
  with alpha particles and obtained atoms of an
  oxygen isotope and protons. This transmutation of
  nitrogen into oxygen is the first artificially
  induced nuclear reaction 7N a 8O
  p

6
Important discoveries pre-WWII

• 1932 February - James Chadwick discovered the
  neutron. It has the same mass as proton but
  without charge.
• 1934 Frédéric and Irène Joliot-Curie discovered
  artificial radioactivity. Enrico Fermi irradiated
  uranium with neutrons, unknowingly achieved the
  world's first nuclear fission.
• 1938-1939 - Otto Hahn sent a paper to Lise
  Meitner containing experimental results that were
  interpreted by Meitner and nephew Otto Frisch as
  nuclear fission.

7
Manhattan Project

• As World War II broke out it became clear that
  the Germans understood fission as well and were
  interested in making a bomb.
• At the urging of prominent scientists, including
  Albert Einstein, the US government was persuaded
  to start a program to develop weapons.
• American scientists were skeptic of fission
  however and didnt start a concentrated effort
  until Dec. 6, 1941.
• By August 1942 things had gotten serious and the
  Manhattan Project was officially born.

8
Manhattan Project Movie (6m)
9
4 Components in the Project

• Achieve a chain reaction/ produce plutonium. This
  was carried out at the University of Chicago,
  called the Met Lab, and led by Compton and Fermi.
• Mass production of U235, the fissionable isotope
  of uranium, carried out at the Oak Ridge
  Laboratories in Tennessee.
• Mass production of plutonium, a better
  fissionable material than U235, carried out at
  Hanford, Washington.
• Design and testing of actual nuclear bombs. This
  was carried out at Los Alamos, New Mexico under
  the direction of Oppenheimer.

10
Testing in Manhattan Project

• By the July of 1945 enough fissionable material
  had been developed (and the bomb design had
  advanced enough) that a test was planned.
• Everyone was confident the U235 bomb would work,
  but the plutonium bomb was a different story - so
  it needed a test.
• On July 4th a test shot of 100 tons of high
  explosive was done. The explosive was purposely
  contaminated with radioactive elements so that
  scientists could track the contamination.
• On July 16, the real test was performed and was
  actually bigger than expected (21 kt). It was
  code-named Trinity.

11
Use of atomic bombs in WII

• The first atomic bomb, Little Boy, was dropped in
  Hiroshima on Aug. 6, 1945. The yield is 15 kt.
  70,000 people killed.
• Three days later, the 2nd bomb, the Fat Man, was
  dropped in Nakasaki with a yield of 20 kt. 52,000
  people died.

12
Use of atomic bombs in WII
13
States with nuclear weapons

• NPT-Recognized
• US (1945)
• Russia (1949)
• UK (1952)
• France (1960)
• China (1964)

De facto India (1974) Pakistan (1998) N.
Korea (2006). Unacknowledged Israel. Abandoned
S. Africa Belarus Kazakhstan Ukraine. In
Progress Iran