There are several important reasons why an H-bomb made of tritium alone is not feasible. The most important by far, which alone excludes it from any serious consideration, is the staggering cost we would have to pay in terms of priceless A-bomb material, as each kilogram of tritium produced would exact the sacrifice of eighty times that amount in plutonium. The reason for this is simple. Both plutonium and tritium have to be created with the neutrons released in the splitting of U-235, each atom of plutonium and each atom of tritium made requiring one neutron. Since an atom of plutonium has a weight of 239 atomic mass units, whereas an atom of tritium has an atomic weight of only three, it can be seen that a kilogram, or any given weight, of tritium would contain eighty times as many atoms as a corresponding weight of plutonium, and hence would require eighty times as many neutrons to produce. In other words, we would be buying each kilogram of tritium at a sacrifice of eighty kilograms of plutonium, which, of course, would mean a considerable reduction in our potential stockpile of plutonium bombs. We would cut this loss by more than half because a kilogram of tritium would yield about two and a half times the explosive power of plutonium. But even this advantage would soon be lost, since tritium decays at the rate of fifty per cent every twelve years, so that a kilogram produced in 1951 would decay to only half a kilogram by 1963. Plutonium, on the other hand, can be stored indefinitely without any significant loss, since it changes slowly (at the rate of fifty per cent every twenty-five thousand years) into the other fissionable element, U-235, which in turn decays to one half in no less than nine hundred million years. What is more, plutonium, if the day comes when we can beat our swords into plowshares, will become one of the most valuable fuels for industrial power, the propulsion of ships, globe-circling airplanes, and even, someday, interplanetary rockets. It holds enormous potentialities as one of the major power sources of the twenty-first century. Tritium, on the other hand, can be used only as an agent of terrible destruction. It will yield its energy in a fraction of a millionth of a second or not at all. The only other possible uses it may have would be as a research tool for probing the structure of the atom, and as a potential new agent in medicine, in which it may be used for its radiations.