Radium in Engineering Practice

Considerable advances have recently been made in nondestructive testing, and a new transportable X-ray laboratory is illustrated in the paper to show that X-rays have achieved a definite, if limited, function in this field. The paper is mainly devoted to a discussion of the properties of radium as a radiographic agent to show how it compares in value with the older X-ray method. The disintegration theory of radioactive materials is outlined and the relative wavelengths of various components of the so-called electromagnetic spectrum, used roughly to indicate their penetrating power, are given. The method of preparing radon is described as it has the great advantage that its use would afford an approximation to a point source of radiation. When employing one of the radium salts, the radium must be removed an appreciable distance from the sensitized film to obtain good definition, thus increasing the exposure time. Careful directions are given for the safe handling and storage of the element. The exposure camera in use in the Research Department, Woolwich, is described and curves are given indicating safe working distances for operators. Many experimental refinements making for clear radiography are mentioned. In the case of X-rays the effect of scattered radiation militates seriously against good results, whereas in gamma-ray photography there is practically no such harmful effect. Hence heavy irregular specimens may be radiographed by radium in perhaps one exposure. Exposure curves for radium, based upon experimental data obtained in the author's laboratory, are given. Owing to the general employment of photographic intensifying screens to shorten exposures, it is not possible to rely on calculations based on the inverse square law. The uses of X-rays and radium are compared and the particular advantages of radium illustrated by a large number of radiographs. X-rays have overwhelming advantages in the examination of metallic structures up to a thickness of about 3 inches. Radium, on the other hand, may be employed in the investigation of metals up to 8 inches or more in thickness.