Atomic+Bombs

The Atomic Bomb By: Stephanie Steffes

Introduction: The atomic bomb is a type of nuclear weapon used to create a large scale relaease of nuclear energy. The atomic bomb was first publicly introduced in 1945 with the hope that it would be the solution to end of the war. However, the planning and creating of this device began in the summer of 1939. The project began directly after Albert Einstein warned Franklin D. Roosevelt about Nazi German'y intentions with uranium-235. If they were able to purify the uranium-235, they could succeed in building a succesful atomic bomb. The United States began their own competing project known as the Manhattan Project. A large scale laboratory was constructed in Oak Ridge, Tennessee, which brought together some of the most well known scientists and physicists of that time. Some of these key contributors of the project include Robert Oppenheimer, David Bohm, Ernest Lawrence, Leo Szilard, Harold Urey, Neils Bohr, and Edward Teller.

This was a difficult project to undertake due to the complexity of extracting uranium-235. Normal chemical etractions could not work in this process, but rather mechanical methods. This was necessary because of the 500:1 ratio of uranium ore to uranium metal. This would be mean that out of the uranium extracted from the ore, 99% of it would be unusable uranium-238. Professor Harold Urey of Columbia University devised a system that would aid in the extraction process through gaseous diffusion. After the extraction was succesfully completed, all that was needed was to test the atomic fission, or splitting of the atom. When the uranium fissions, initiated by the fission of the uranium nucleus, it breaks down into nuclear fragments and release energy. During this same time, the nuclues releases fast neutrons. This process is known as a chain reaction and continues to release energy.

The first atomic bomb, called Little Boy, was used for military purposes was dropped by the United States on August 6, 1945. It produced an explosion that devastated the city of Hiroshima, Japan. It killed tens of thousands of people in less than one minute. A mass of uranium, roughly the size of a baseball, produced amn explosion as powerful as 20 kilotons of TNT. Little Boy was a gun-type fission bomb. A small wedge of uranium was fired at a larger target piece of uranium. Opun impact, the two pieces briefly fused together creating a supercritical mass.

Chemical Principles: Nuclear Fission and Fusion: Both nuclear fission and fusion reactions can be used to generate large amounts of energy for destructive purposes. When an atom of uranium-235 is attacked by a neutron, it splits into atoms of cesium and rubidium, releasing a large amount of energy and additional neutrons. These neutrons, if not controlled, can cause more uranium-235 atoms to split. This leads to a rapid nuclear explosion or an atomic bomb. Fusion reactions release energy when teo nuclei combine to make a heavier atom.

Critical Mass: A small sphere of uranium-235 the size of a gol ball would not sustain a chain reaction. Too many neutrons escape through the surface area, which is relatively larged compared with its volume. Therefore, they are lost to the chain reaction. In a mass of uranium-235 the size of a baseball, the number of neutrons lost through the surface is compensated for by the neutrons generated in additional fissions. The minimum amount required to maintain the chain reaction is known as the critical mass. In an atomic bomb a mass or fissile material greater than the critical size must be put together instantaneously and held together roughly for one millionth of a second.



The physicists had to answer two fundamental questions: how much fissile material would be required for the weapons, and how much time would be needed for an effective detonation. The initial calculations for the mass of U-235 required for a bomb looked like this: They wanted a 20-kiloton explosion (equivalent to 20,000 tons of TNT), so

If each fission produces 3.2 x 10-11 joules, then the number of fissions (N) required is Thus, the mass of U-235 required would be  The physicists calculated a 10% efficiency for the weapon so

The time required for an effective detonation can be calculated from the basic exponential equation for neutron production.



Societal Impacts: The societal impacts of nuclear weapons and the atomic bomb include physical, health, environmental, social, and psychological.

Physical Impacts: The force of the explosion alone destroys any and all objects around it as well as killing those in its path. Depending on the size of the atomic bomb, it can also create a crater within the earth. The heat and radiation also causes detrimental physical damage within a certain radius of the explosion depending on its size. The explosion also creates a wind that can travel several hundred kilometers per hour. The wind would create fast flying debris and greater attribute to the damages and deaths.

Health Impacts: Those that were not immediately killed by the explosion, may be in serious health trouble depending on their proximity of the initail explosion. The closer to the explosion, the greater the effects of radiation or thermal damage. Some will be killied within minutes of the explosion due to radiation and other could survive for hours or even days. However, there is no sure for radiation poisening and those greatly affected will not survive. Those receiving small enough doses can survive, but with other physical illnesses or harms. There are also health impacts with those that work with nuclear weapons. It is estimated that 13 million people have died due to the production, testing, use, and waste of these weapons.

Environmental Impacts: These weapons have damaged and destroyed the water and soils of areas not only that have been directly hit by them, but also those around the testing facilities. The substance released, which include plutonium, uranium, cesium, benzene, mercury, cyanide, could be present in the environment for thousands of years. This includes the waste that is emitted in producing and testing these weapons. In the United States, it is estimated that there are 4500 contaminated Department of Energy sites. The air is also significantly polluted by these emissions. The mining, processing, and transporting of uranium contributes to environmental pollution.

Social Impacts: The massive and simultaneous destruction of economic and human resources would result in an inability to provide immediate and sufficient human and material aid to damaged areas. There will be no time to adapt and to innovate as nations did in World War II. More importantly, the lack of outside aid would create a sense of individual and common isolation. Economic destruction, loss of political leadership (especially at the local level), and the need to mobilize resources for relief and recovery would present extraordinary demands on weakened political institutions.The character of political institutions and authority would almost certainly change, especially if hostilities or the threat of hostilities persisted. Both old and new political structures would be likely to suffer from greatly reduced credibility.

Psychological Impacts: From a psychological point of view, limited nuclear war probably is the worst of all worlds. The imagery of nuclear war, the widespread casualties, and the intense fear of radioactivity would lead to the "nuclear war survivor syndrome". This powerful sense of personal vulnerability, helplessness, guilt, isolation and fear, was seen to varying degrees in the Hiroshima and Nagasaki survivors. The result of this experience was a deep fear of returning to the cities to rebuild the any form of normal life that may be possible after a nuclear attack. Families would be broken up by death, severe injury, disease, evacuation, or military and labour conscription. The young, elderly, and handicapped would suffer disproportionately since they depend most on society's material and institutional resources.

__References:__ [|http://inventors.about.com/od/astartinventions/a/atomic_bomb.htm][]