Tritium All Around

Every drop of ordinary water contains about 2,000 atoms of tritium, a key ingredient of the hydrogen bomb. This seemingly startling discovery was announced last week by Drs. Willard F. Libby of the University of Chicago and A. V. Grosse of Temple University. But no one need swear off drinking water--at least for that reason. Only one quintillionth (1/1,000,000,000,000,000,000) of its hydrogen atoms are tritium. An explosion is not likely.

Tritium is the big brother of the hydrogen family. Ordinary hydrogen has one lone proton in its nucleus with an electron circling around it. Deuterium (heavy hydrogen) has one proton and one neutron in its nucleus. Tritium (heavy heavy hydrogen) has one proton and two neutrons. It is feebly radioactive, with a half-life of about twelve years. Drs. Libby and Grosse detected it through its radiation in samples of heavy (deuterium-containing) water. Its presence in heavy water had been suspected for some time, but not conclusively proved.

According to Drs. Libby and Grosse, the tritium now on earth was formed recently by cosmic rays from outer space hitting and smashing nitrogen atoms in the upper atmosphere. During the confusion, some protons knocked out of the nitrogen make off with two neutrons in attendance. The threesomes pick up electrons and become tritium atoms. Eventually they join with oxygen, form water molecules and fall to earth in the rain.

Natural tritium is much too scarce to help the makers of hydrogen bombs, who will have to synthesize their tritium, presumably in a chain-reacting pile. The only use for it in sight at present is to trace the vertical motions of ocean currents. Since short-lived tritium originates in the atmosphere, only water that has been on the surface recently should have a full complement of it. Water that has spent many years in the ocean depths should be tritium-free.

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