Nuclear chain reactions Szilard

As the light changed to green and I crossed the street, Szilard recalls, it... suddenly occurred to me that if we could find an element which is split by neutrons and which would emit two neutrons when it absorbs one neutron, such an element, if assembled in sufficiently large mass, could sustain a nuclear chain reaction. 

Leo Szilard received no invitation to the Solvay Conference. By October 1933 he had not accomplished any nuclear physics of note except within the well-equipped laboratory of his braia In August he had written a friend that he was spending much money at present for travelhng about and earn of course nothing and cannot possibly go on with this for very long. The idea of a nuclear chain reaction became a sort of obsession with him. When he heard of the Joliot-Curies discovery, in January, his obsession bloomed I suddenly saw that the tools were on hand to explore the possibility of such a chain reaction. ... 

In those earliest days, I suppose Szilard was the more deeply absorbed in the fission problem - after all, he had worked out the theory of a nuclear chain reaction even before fission had been discovered and on March 20, 1939, he applied for a U.S. patent on what he called an Apparatus for Nuclear Transmutation - i.e. a neutron chain reactor based on the fission of uranium (6). Wigner was fully aware of Szilard s thinking and with his powerful grasp of the mathematical and physical principles underlying the chain reaction, Wigner was, even then, able to make independent estimates of the critical conditions. 

Under this arrangement, they received limited clearance which did extend, however, to the whole field of nuclear chain reactions. This situation is essentially in effect even now, except that Fermi is cleared both for fast and slow, Szilard only for slow chain reactions. 

The great surprise about nuclear chain reactions was the ease with which they could be established. Szilard s paper of January 1940 already describes a workable arrangement. Our own early work in this field was not based on Szilard s paper but on Fermi s work, the concepts of which are less intricate than Szilard s. Ideas similar to Fermi s were developed also by others, notably by v. Halban moreover, the whole work was duplicated, apparently without any major deviation, also by the German nuclear physicists. 

Nuclear chain reaction (Leo Szilard) Szilard conceives the idea of a nuclear chain reaction. He becomes a key figure in the Manhattan Project, which eventually builds the atomic bomb. 

In the course of the last four months It has heen made probahls through the work of Jollot In Prance as well at eml and Szilard In America that it may become possible to set up a nuclear chain reaction In a large mass of uranium by which vast amounts of power and large quantities of new radium-like elements would be generated ITow it appears almost certain that thia could be achieved In the Immediate future ... 

In 1934 the Hungarian physicist Leo Szilard filed a patent with the British Patent Office. It was based on an idea, nothing more - an idea about how to harness nuclear energy. The Joliot-Curies had shown that bombarding nuclei with particles can induce radioactive decay artificially. And the work of Bothe and Chadwick had demonstrated that some radioactive nuclei emit neutrons. So what would happen if neutrons induced nuclear decay that led to more neutrons The result might be a chain reaction a self-sustaining release of nuclear energy. 

Leo Szilard determined that the formation of neutrons occurs during the fission of uranium. This is crucial to sustaining a chain reaction necessary to build an atomic bomb, the first of which he helped to construct in 1942. Shortly thereafter, realizing the destructive power of the atom bomb, Szilard argued for an end to nuclear weapons research. 

I first heard the possibility of nuclear power seriously discussed in the spring of 1934 when I saw Szilard during a visit to London. The efficiency of collisions between neutrons and nuclei was realized by Szilard simultaneously with and independently from Fermi. He visualized the possibility of chain reactions involving neutrons even at this time. His interest was centered aroimd the reaction... 

I knew very little at that time about the work that was being carried in Chicago and what I can say about it is necessarily very sketchy. It was only a short time ago that I found out that V. Wilson wrote a memorandum to Mr. Compton during the summer of 1940, that is, only about six months after Szilard sent his article to the Physical Review. In this memorandum Wilson attempted to calculate the multiplication constant if one uses beryllium instead of hydrogen as a moderator. On the basis of nuclear constants which we now know to be rather far from their actual values, he arrived at the conclusion that a chain reaction with unseparated uranium and beryllium as a moderator may just barely be possible. V. Wilson apparently was not familiar with the idea of the lattice as developed in Columbia but assumed a homogeneous mixture of beryllium and uranium. 

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