Jethalal S. Zaveri
Prof. Muni Mahendra Kumar
The requirement to start the fission process of U-235 and also the two man-made elements mentioned above (all these being known as nuclear fuels), is simple. All that is necessary for the spontaneous combustion, to use a familiar phrase, of any one of the three atomic fuels, is to assemble a lump of a certain weight known as critical-mass which is between ten and thirty kilograms. This would mean that a lump of any of the three atomic fuels weighing ten or thirty kilograms (exact mass is a secret) would explode automatically and release an explosive force of 20 million times greater than that of TNT, (on an equal weight basis). Such as, spontaneous combustion destroyed Hiroshima and Nagasaki on 6th & 7th August 1945. In a conventional A-bomb, a critical mass is assembled by a timing mechanism that brings together, let us say, one-tenth and nine-tenths of a critical-mass in the last split second.
Long before, it was discovered that vast amounts of energy could be liberated by the fission of the nuclei of U-235, scientists had known that fusion of four atoms of hydrogen into one atom of helium would release enormous amount of energy. In 1938, slightly before the discovery of uranium, fission was announced in Germany; Dr. Bethe had published his famous hypothesis about the fusion of four hydrogen atoms to form helium in the sun. This provided the first satisfactory explanation of the mechanism that enables the sun to radiate away staggering amounts of energy in space every second. While Dr. Bethe was the first to work out the fine details of the process of hydrogen fusion as the source of the sun's radiance, Prof. F.W. Aston, the British Nobel Prize-winner, and other scientists indicated the possibility more than 20 years ago. We shall examine the solar process in brief a little later.
Deuterium, popularly known as heavy hydrogen, is an isotope of hydrogen having double the weight of common hydrogen. It was found to exist in nature constituting one five-thousandth part of the earth's waters. Water containing two deuterium atoms in place of the two atoms of common hydrogen is called heavy water.
The most startling fact discovered about deuterium was that it would become explosive at a temperature of the order of 5.00.00.000 degrees centigrade. Explosive of an A-bomb would generate such high temperatures on earth and such an explosion would then act as a trigger for the hydrogen bombs.
Fission and fusion, however, are also common in everyday phenomenons that occur any time you burn anything. Both are essential whenever energy is released, whether it is the chemical energy from coal or the atomic energy from nuclei of uranium or deuterium. For example, when you light a cigarette, the first fission, and fusion occurs in the lighting of the match, the cellulose in the match being fission into its components carbon and hydrogen. These are then fusion with the oxygen of the air. The same thing happens when the tobacco catches fire. In each case, the fusion with oxygen makes possible the fission of the cellulose.
It is a scientific fact that man now has at his disposal means that not only can wipe out all life on earth, but also make the earth itself unfit for life for many generations to come. Here we have indeed what is probably the greatest example of irony in man's history! The very process in the sun, that made life possible on earth and is responsible for its being maintained here, can now be used by man to wipe out that very life and to ruin the earth for good. In both, fission and fusion, only a very small fraction of the mass of the protons and neutrons in the nuclei of the atoms used is liberated in the form of energy, while 99.3 to 99.6% of the substance remain in the form of matter.
Scientists are even now engaged in finding means of converting 100% of the matter into energy i.e. complete annihilation of matter by the conversion of the entire mass of protons and neutrons into energy instead of only 0.4 to 0.7% And while the total conversion of protons and neutrons still seems speculative, we already know that such a process actually does take place in the realm of the electron. This is the phenomenon of the mutual annihilation of a positive electron (positron) and a negative electron, achieved numerous times on a small scale in the laboratory, which we have already discussed. In this process the entire mass of the two particles is converted into energy. Luckily each positron must be individually produced, since there are hardly any positrons in our part of the universe. But suppose a new process that would release positrons in large numbers is found, just as the process of liberating large number of neutrons was found, then in such an eventuality, by no means beyond the realm of the possible, would open potentialities of horror alongside which those of the hydrogen bomb would be puny. For any process that would release a large number of positrons in the atmosphere, in a chain reaction similar to the one now liberating neutrons, may envelope the whole earth in one deadly flash of radioactive lightning that would instantly kill all life. And although this is admittedly purely speculative, no one dare say that such a discovery will not be made, not when one remembers how remote and unlikely a process such as fission seemed to be just before it was made.
