Nuclear fission

In physics, fission is a nuclear process, meaning it occurs in the nucleus of an atom. Fission is when the nucleus splits into two or more smaller nuclei plus some by-products. These by-products include free neutrons and photons (usually gamma rays). Fission releases substantial amounts of energy (the strong nuclear force binding energy).

Production and purification of materials

It has been stated above that the cross section for capture of neutrons varies greatly among different materials. In some it is very high compared to the maximum fission cross section of uranium. If, then, we are to hope to achieve a chain reaction, we must reduce effect (3) - non-fission capture by impurities -to the point where it is not serious. This means very careful purification of the uranium metal and very careful purification of the moderator. Calculations show that the maximum permissible concentrations of many impurity elements are a few parts per million- in either the uranium or the moderator. When it is mentioned that up to 1940 the total amount of uranium metal produced in the USA was not more than a few grams and even this was of doubtful purity, that the total amount of metallic beryllium produced in the USA was not more than a few kilograms, that the total amount of concentrated deuterium produced was not more than a few kilograms, and that carbon had never been produced in quantity with anything like the purity required of a moderator, it is clear that the problem of producing and purifying materials was a major one.

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The problem of producing large amounts of high purity uranium was solved by Frank Spedding using the thermite process. Ames Laboratory was established in 1942 to produce the large amounts of uranium that would be necessary for the research to come.

Related Topics:
Frank Spedding - Thermite - Ames Laboratory

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