chemistry

Kristen Nix Mr. Lewandowski 6th hr. 1/16/09

Out of Control

The study of muclear chemistry was started after the discovery of radioactive substances. The chemists who started this field were Pierre and Marie Curie(Pauling). The first to study uncontrolled fission for the purposes of a bomb were the Germans. By 1939 they had already figured out how to split the uranium-235 atom and knew they needed to form a chain reaction. Two german scientists, who disagreed with the nazis, came to America to tell somebody with enough political power to warn the President. These scientists were Leo Szilard and Eugene Wigner, and the somebody they told was Albert Einstein. Albert Einstein didn't really want to get involved, but he did anyways to help the American government. Leo Szilard wrote a letter to President Roosevelt explaining their current situation and Albert Einstein signed it. President Roosevelt then assigned the Briggs Committee to immediatly start building an atomic bomb. The only other role Einstein played was giving the Briggs Committee some advice on a theoretical problem and he was the first to realize that a very small amount of uranium-235 could release a lot of energy(Doug Long). My paper will explain what the Briggs Committee and other scientists have learned about making atomic and hydrogen bombs. I will start with explaining how an atomic bomb works. The substances needed to make an atomic bomb are uranium-235 or plutonium-239. In any atomic bomb using uranium-235, slow-moving neutrons are released into a sphere of uranium-235. Uranium-235 is a very stable atom until it is bombarded by a neutron. This would make it uranium-236, which is very unstable. This atom then splits into two different stable atoms(Atomic Archive). These atomes are called the daughter nuclei. These elements contain the neutrons which started the reaction. Since the ratio of neutrons to protons is greater in the heavier nuclei, a few neutrons are liberated. These liberated neutrons are absorbed by other uranium-235 atoms adn start a chain reaction also known as an autocatalytic reaction(Pauling). When the autocatalytic reaction is almost complete, this is called the critical mass, nuclear energy is released in the form of heat and gamma radiation(Worsley). There are a couple of different kinds of bombs that have been made. One of them is called "The Little Boy Design". In the little boy design, a small gun inside the bomb shoots a small mass of uranium-235 into a larger mass of uranium. Once together an initiator introduces a burst of neutrons into the sphere of uranium. This starts off the autocatalytic reaction and creates a supercritical mass. The bomb then blows itself up, releasing heat and gamma radiation(Atomic Archive). Another design is "The Fat Man" or implosion type bomb. This bomb uses plutonium-239(Atomic Archive). (Usually this design isn't made because plutonium has a high rate of spontaneous fission and it isn't a naturally occuring element(Worsley)). This design uses explosive charges to compress a sphere of plutonium-239 so rapidly that it forms a density sufficient to force a critical mass and produce a nuclear explosion. TNT are placed around a sphere of plutonium and detonated. A shock wave is sent inward, increasing the pressure on the plutonium. At the same time the shock wave hits the core of the bomb, which increases the density. Immediatly afterwards an initiator releases a large amount of neutrons. Since the density is already so high, early generations of the autocatalytic reaction are completely bypassed. The reaction continues until the internal pressure is greater than the implosion pressure from the shock wave. The bomb then disassembles and the energy from the fission is transferred to the surroundings(Atomic Archive). The intense and massive power behind any atomic reaction is the strong nuclear force, which binds protons and neutrons together to form quarks. For example, uranium atoms are very large, which means they have a weaker nuclear force. This makes it very hard to firmly hold together. So when bombarded with a neutron it is easily split into two daughter nuclei. The evergy givin off by fission is called the mass defect. To find the energy being produced the formula E=mc squared is used. Professor Albert Einstein created this formula when approached by Szilard and Wigner(Doug Long). This equation means the energy produced will be equal to the mass defect times the square of the speed of light(Moore).