Era Of Atomic Age Begin Part-1/2


Era Of Atomic Age Begin Part-1/2


download-18 Era Of Atomic Age Begin Part-1/2The atomic age dawned exactly at 25 minutes past 3 O’clock in the afternoon of 2nd December 1942. Even the birthplace can be stated without any ambiguity. It happened at the squash courts beneath the West Stands of Stagg field in Chicago. The midwives were Italian Nobel laureate Enrico Fermi and his associates. On that day man first initiated a self-sustaining nuclear chain reaction and controlled it. With that man ushered in a new era where the immense energy locked inside an atom was set free. Since then man has been exploiting it both for peaceful purposes as well as for building weapons of mass destruction.

The developments that led to this momentous event are themselves very interesting. Corbin Allardice and Edward R. Trapnell of the U.S. Atomic Energy Commission have provided us with an eyewitness account of the episode. The modern Italian explorer of the unknown was in Chicago that cold December day in 1942. An outsider looking into the squash court where Fermi was working would have been greeted by a strange sight. In the centre of the 10 m x 20 m room, shrouded on all but one side by a grey balloon-cloth envelope, was a pile of black bricks and wooden timbers, square at the bottom and a flattened sphere on top. Up to half of its height construction of this crude appearing but complex pile, the name which has since been applied to all such devices, the standing joke among the scientists working on it was: “If people could see what we’re doing with a million and a half of their dollar, they’d think we are crazy. If they knew why we were doing it, they’d be sure we are.” Three years before the December 2 experiment, it had been discovered that when an atom of uranium was bombarded by neutrons, it was sometimes split, or fissioned.




download-18 Era Of Atomic Age Begin Part-1/2Later still, it had been found that when an atom of uranium fissioned, additional neutrons were emitted and became available for further reaction with other uranium atoms. These facts implied the possibility of a chain reaction, similar in certain respects to the reaction which is the source of the sun’s energy. The facts further indicated that if a sufficient quantity of uranium could be brought together under the proper conditions, a self-sustaining chain reaction could be maintained. The amount of uranium which makes it possible to maintain such a chain reaction under given conditions is known as the ‘critical mass, or more commonly, the ‘critical size’ of the particular pile. Fermi and Walter Zinn and their associates were working to determine operationally possible designs of a uranium chain reactor. Among other things, they had to find a suitable moderating material to slow down the neutrons travelling at relatively fast velocities. Fermi who had mathematically demonstrated the feasibility of sustaining a chain reaction had realised that neutrons emerging out of a fission reaction would have to be slowed down in order to keep a chain reaction going without any hindrance. The energy of such slow neutrons would be close to thermal energy. Hence they were dubbed as thermal neutrons in contrast to those emitted by a uranium atom undergoing fission. The latter was described as fast neutrons. A uranium atom that is split gives rise to an average of 2.3 neutrons. That would trigger another 2.3 uranium atoms to undergo fission. Each of these events would emit 2.3 neutrons and so on. Thus the chain reaction would continue in geometric fashion and can lead to an explosive situation.


download-18 Era Of Atomic Age Begin Part-1/2Fermi who had mathematically demonstrated the feasibility of sustaining a chain reaction had realized that neutrons emerging out of a fission reaction would have to be slowed down in order to keep a chain reaction going without any hindrance. The energy of such slow neutrons would be close to thermal energy. Hence they were dubbed as thermal neutrons in contrast to those emitted by a uranium atom undergoing fission. The latter was described as fast neutrons. A uranium atom that is split gives rise to an average of 2.3 neutrons. That would trigger another 2.3 uranium atoms to undergo fission. Each of these events would emit 2.3 neutrons and so on. Thus the chain reaction would continue in geometric fashion and can lead to an explosive situation.

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By-Narendra Kr.Sharma

download-18 Era Of Atomic Age Begin Part-1/2
Narendra Kumar Sharma