238 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1953 



on one side of the material whose thickness is to be measured and a 

 radiation instrument on the other side. The amount of radiation 

 which penetrates through the material decreases with the thickness 

 of the material, that is, the thicker the material the less radiation 

 gets through and vice versa. The radiation meters used in these gages 

 are designed to read in thickness values. 



Radioactive thickness gages are now being sold by three commercial 

 manufacturers, and approximately 100 industrial firms have obtained 

 permission from the Commission to buy and install them. They are 

 very sensitive to small differences in thickness and give very repro- 

 ducible results. Another big advantage is that the gage makes no 

 mechanical contact with the material being measured. This means 

 that the gage can be used without stopping or cutting the rolling sheet 

 and without danger of tearing or marking the sheet. Still another 

 advantage is that the gage can be made to control automatically the 

 settings of the rollers rolling out the sheet. 



Radioactive thickness gages have been used to measure the thick- 

 ness of paper, rubber, plastic, glass, and steel sheets. Firms using 

 them have been able to meet more exacting specifications and as a 

 result have been able to cut down on the amount of reject material. 

 This has meant a savings of thousands of dollars a year to some firms. 



An example of an application that uses the radioactive material as 

 a movable rather than stationary source of radiation is following the 

 flow of oils through pipe lines. It is common practice to use the same 

 pipeline to transport a wide variety of crude or refined oils. The 

 location of the boundary between the two oils must be known in order 

 to route different oils to different takeoff points and terminals along 

 the line. The radioisotope method is based on injecting into the line 

 a small amount of radioactive material just at the boundary as a 

 product is changed. Geiger counters detect and record the passage of 

 radioactivity in this boundary at various points along the line. Clean 

 separation of the different oils means a large saving in money. One 

 company is routinely using this method of boundary marking in a 

 pipeline running from Salt Lake City, Utah, to Pasco, Wash. — a dis- 

 tance of more than 550 miles. The same company has said that the 

 new method means a saving of hundreds of barrels per day of oils that 

 would have an average retail value of about $10 a barrel. 



An example of an industrial tracer application is the radioisotope 

 method of measuring wear or friction. Several companies are using 

 this method for studying wear in engines. A piston ring or some other 

 motor part is sent to Oak Ridge, made radioactive in the nuclear re- 

 actor, and then returned for replacement in the engine. The motor 

 with its radioactive piston rings is then run. As the rings wear, some 



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