New Jobs for Radioactivity

Radioactive tracers, which have revolutionized medical and biological research, are now going to work in industry. This week Arthur D. Little, Inc. of Cambridge, Mass, told how it used the tracer technique to solve a steel problem.

Steel manufacturers know that sulphur (an undesirable impurity) gets into steel from the coal used as fuel. But there are two types of sulphur in coal: organic and "pyritic" (iron sulphide). Republic Steel Corp. wanted to know whether either type is driven off when the coal is made into coke. There was no handy chemical way to find out, but the Little Co.'s scientists worked out a tracer technique that did the job quickly and easily.

They made a small amount of pyrites containing radioactive sulphur and mixed it with a coke-oven charge of coal. They roasted the coal and measured the radioactivity of the sulphur remaining in the coke. A very low level of radioactivity would indicate that most of the pyritic sulphur had been driven off, taking with it the radioactive tags. A higher level would show that the organic sulphur had been eliminated, leaving behind the pyritic sulphur. Actually, the radioactivity of the sulphur fell between the two extremes, showing that both forms of sulphur stay behind in the coke. The experiment proved to Republic Steel that there is no advantage in using coal that is low in one type of sulphur and high in the other.

The Little Co. sees a bright future for tracers in industry. They can be used to measure the infinitesimal amount of lubricant applied to textile fibers, or to estimate the ghost-thin film of metal rubbed off a shaft when it revolves in its bearings. No quantity of material is too small to carry telltale sparks of radioactivity.

It won't be long, the chemists think, before radioactive tracers are used to control industrial processes. Bessemer converters, for instance, burn impurities out of molten iron with a blast of air. Usually the phosphorus is the last impurity to go. The Little scientists propose that a small amount of radioactive phosphorus be added to the mix. When it (and the ordinary phosphorus with it) has been burned out of the steel, automatic instruments will note instantaneously the drop in radioactivity. Then the air blast can be shut off at exactly the right moment.

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