Nuclear weapons

Nuclear weapons are a type of weapon that uses nuclear fission (atomic bombs) or nuclear fusion (hydrogen bombs). The first atomic bombs were tested by the USA in 1945 and dropped over the Japanese cities of Horishima and Nagasiki. Hydrogen bombs have been around since 1953. Nuclear weapons are one of the most dangerous types of weapons. Everyone should work to ensure that they are never used again.

Nuclear weapons

Nuclear weapons

Nuclear weapons are a type of weapon that uses nuclear fission (atomic bombs, fission bombs) or nuclear fusion (hydrogen bombs). Their development is closely related to the Second World War.

On the development of nuclear weapons

Shortly after the discovery of nuclear fission by OTTO HAHN (1879-1968), LISE MEITNER (1878-1968) and FRITZ STRASSMANN (1902-1980), many physicists were already aware of the fact that nuclear fission releases a lot of energy which could possibly be used for technical purposes.
In 1939/40, Germany, France, Great Britain, the USA and the Soviet Union had about the same level of knowledge about nuclear energy, since all basic papers had been published in generally accessible journals.

Development in the USA

With the beginning of the Second World War, however, the situation changed fundamentally. A number of researches were declared important for war and therefore secret. The exchange to results of scientific research was no longer possible. Scientists who emigrated from Europe to the USA, including ALBERT EINSTEIN (1879-1955), drew attention to the basic possibility and danger of developing nuclear weapons in fascist Germany.
This finally gave rise to the " Manhattan Project ", the development of an American atomic bomb.

From 1942 onwards, work on an atomic bomb was pushed ahead at enormous expense, which only the USA was capable of at that time. Many scientists who had emigrated from Europe to the USA were also involved in the work, u. a. the Italian ENRICO FERMI, the Hungarian physicists EDWARD TELLER, LEO SZILARD and EUGEN WIGNER, the Danish physicist NIELS BOHR or the German physicists HANS A. BETHE, KLAUS FUCHS and JAMES FRANCK. Included also many British core researchers, u.a. the discoverer of the neutron, JAMES CHADWICK, and the creator of the first cyclotron, ERNEST O. LAWRENCE.
Numerous American scientists were also involved, such as HAROLD E. UREY (discoverer of heavy hydrogen), GLENN TH. SEABORG (co-discoverer of numerous new elements) or RICHARD P. FEYNMAN.

The scientific leader of the American atomic bomb project was the American nuclear physicist ROBERT OPPENHEIMER (1904-1967). It was possible to build an atomic bomb within 3 years.

The first atomic bomb, a plutonium bomb, exploded on 16. July 1945 at an experimental site in New Mexico (USA). The first atomic bombs were dropped on 6. August 1945 over the Japanese city of Horishima, and on 9. August dropped over the Japanese city of Nagasaki. The bomb of Hiroshima used uranium-235 as nuclear explosive, the one of Nagasaki
Plutonium-239. The immediate result was hundreds of thousands of deaths, and in the decades that followed, thousands more deaths, as well as numerous other damages.

Development in Germany

In Germany, the Army Weapons Office became interested in the military use of nuclear energy and set up a corresponding research center at the Kaiser Wilhelm Institute for Chemistry in Berlin-Dahlem in 1939. The director was Dr. DIEBNER. In parallel, research was carried out at various universities. In 1941 an experimental reactor was built in the Physical Institute of the University of Leipzig. In 1942 this reactor delivered more neutrons than a neutron source in its interior emitted. This was proof that a chain reaction was technically feasible.
The Berlin experiments had to be abandoned in 1945 because of the air raids. The Berlin experimental reactor was rebuilt in a former wine cellar in Haigerloch near Hechingen, Germany. The area was occupied by the Americans in April 1945, the reactor was removed and the scientists involved were imprisoned in England. Later calculations showed: If the reactor had been slightly enlarged, it could have been successfully set in motion. However, Germany was far away from the development of an atomic bomb.

Development in the Soviet Union

The development in the Soviet Union was different . Here, too, as in the USA, various scientists had alerted military authorities and the government to the possibility of building nuclear weapons. Certainly also in knowledge of the developments in the USA one began in 1943 in the Soviet Union under the direction of IGOR WASILJEVITSCH KURTSCHATOW (1903-1960) to work on the development of an atomic bomb. In August 1949, the first Soviet atomic bomb was detonated at a test site.

Immediately afterwards – it was the time of the Cold War between the Soviet Union and the USA – a new round of the arms race began with the development of hydrogen bombs. In 1952 the first hydrogen bombs were detonated by the USA and in 1953 by the Soviet Union. The explosive power of these bombs was many times greater than that of the first atomic bombs.
In the forties to seventies of the 20. In the 20th century there were numerous experiments with atomic bombs and hydrogen bombs, connected with a considerable radioactive load of the atmosphere. In the meantime these experiments have been stopped. A broad arsenal of nuclear weapons continues to exist, with a number of countries besides the U.S. and Russia now possessing nuclear weapons, z. B. France, Great Britain, China, India, Pakistan or Israel.

Structure and mode of action of nuclear weapons

The partial masses are chosen so small that no chain reaction takes place in them. But if you shoot them at each other by detonating conventional explosives, the critical mass is exceeded. This is the mass at which a chain reaction takes place by itself. In the case of an uncontrolled chain reaction, it proceeds explosively. A huge amount of energy is released in a fraction of a second.

Critical mass depends on the design of the bomb and the nuclear explosive used.
If uranium-235 is used, the critical mass is ca. 50 kg. This corresponds to a ball with a diameter of about 17 cm. For plutonium-239 the critical mass is about 10 kg. This corresponds to a sphere of about 10 cm in diameter.
This critical mass can be significantly reduced if the fissile material is surrounded by a reflector (heavy water, graphite, beryllium), which deflects the escaping neutrons back into the uranium or plutonium.
With heavy water as a reflector, the critical mass drops at
Uranium-235 on ca. 23 kg, in the case of plutonium-239 to 5.4 kg.

Effects of nuclear weapons

The effects of a nuclear blast are many and varied, some short-lived and some longer-lasting:

  • The energy released produces a fireball of great brightness and high temperature. The temperature at the center of the exploding bomb is estimated at several million degrees. With a diameter of the resulting fireball of 100 m, the temperature is still over 7,000 °C, more than the temperature at the surface of the sun. The consequences are severe burns and fires. Near the explosion center even metal vaporizes.
  • A powerful blast wave of great destructive effect is created.
  • There is a short-term high radiation exposure of the affected area with the result that living beings die within days and weeks.
  • The area will be radioactively contaminated for a longer period of time. This leads to deformities, cancer and other diseases even many years later.

In the meantime, there are also nuclear weapons, which are only lethal for living beings, but hardly damage buildings and plants. Such Neutron weapons emit intense neutron radiation.

Hydrogen bombs

In hydrogen bombs, uncontrolled nuclear fusion is used. To create the temperature and pressure necessary for nuclear fusion, one uses a "normal" atomic bomb as the "detonator" for a hydrogen bomb. The explosive power of these bombs exceeds that of nuclear fission bombs many times over. Its use would be a catastrophe for mankind.

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