Document mvzyvL3nEVzp6yMjND1paLrk

IONIZING RADIATION Rfl 42-6 Radiation level near beta ray gouge used to measure thickness of steel strip is checked with a Geiger counter Courtesy Armco Steel Corp mabon One example is the employment of radioacbve sources to effect quantitative or dimensional control of industrial materials (for example, to measure fluid-flow rates, and thicknesses of semifinished or finished products) Sealed sources Sealed sources are avail able that have widely varying amounts of radioactivity A high intensity source may require so much shielding that it will not be portable Shielding, control devices, and procedures should be designed by someone experienced in such work Keeping external exposures to personnel under control should be easily accomplished with the aid of alarms, strict control of access, and thor ough monitoring (Fig. 42-6). (See NBS Handbook 73, Protection Against Radiation from Sealed Gamma Sources (1960), and also Handbook 68, Safe Design and Use of Industrial Beta-Ray Sources (1958) ) At the other extreme, if the source is of trivial size, it should present no more diffi cult problem than that of keeping track of its presence Sources of intermediate size are more troublesome. They are portable and in some cases may require so little shielding that they can easily be moved by hand The person operating a portable source must be depended upon to follow the necessary pre cautions, including the use of film badges and dosimeters to measure his own expo sure, and to operate the source so that other persons are not accidentally irradi ated (see NBS Handbook No 66 Safe De sign and Use of Industrial Beta-Ray Sources, and NSC Industrial Data Sheet 461 Beta-Ray Sealed Sources) Some sealed sources are subject to break- 42-17