456 1S0T0PIC TRACERS AND NUCLEAR RADIATIONS [Chap. 19 



Essential items of laboratory equipment are remote manipulating devices 

 with which all pieces of apparatus, such as beakers, flasks, and serum bottles, 

 either containing or near active material can be handled. Such devices serve 

 two important functions. (1) They increase the distance of personnel from 

 active material and thereby reduce the risk of exposure by allowing shields 

 to be interposed, increasing the air absorption, and decreasing the inter- 

 cepted radiation intensity by the geometrical factor of roughly the reciprocal 

 of the distance squared. (2) Even the simplest of these instruments keep 

 the hands and head away from regions above open vessels where direct and 

 scattered radiation intensity is always the greatest. 



The simplest devices for this purpose are scissors-type tongs, as shown in 

 Fig. 119. With an assortment of lengths and clamp sizes they can be used 

 for many general purposes, from manipulating stirring rods to screwing caps 

 on bottles. Lengths up to 18 in. are the most useful ; beyond this they become 

 unwieldy. 



Another popular form of tong is that shown in Fig. 120. The clamp is 

 actuated by a drawrod or cable running through a long light metal tube to 

 which the clamp is hinged. With the clamp closed by locking the drawrod 

 under tension at the far end, both hands are freed to manipulate a piece of 

 apparatus without excessive strain or caution. Devices of this kind can be 

 made in almost any length and often can be manipulated with greater ease 

 and assurance than scissors-type tongs. Convenient forms can be made 

 for a wide variety of purposes such as turning stopcocks, handling glassware, 

 and performing simple operations. 



To these may be added many special devices as suggested by the mechanical 

 requirements of a process. If a procedure is to be carried out routinely, it 

 is often expedient to design special equipment to perform as much of the 

 process as possible automatically and by remote control behind fixed shields. 

 In such cases the efficiency of an operation is greatly increased, and the 

 danger of exposure and contamination is reduced to a minimum. Examples 

 of such processes and equipment are to be found in references 1 and 2. 



Complex mechanisms such as the pantograph manipulator will doubtless 

 be put to increasing general use as improvements in design make them more 

 efficient and versatile and less unwieldy. To be useful for more than a few 

 specialized operations they should permit several degrees of rotation and 

 translation of the working end to be controlled easily from the remote operat- 

 ing end. 



High-energy gamma-active materials in quantities greater than the 100- 

 millicurie level necessitate handling behind general shields of sufficient thick- 

 ness and area to stop all direct as well as scattered radiation. This requires 

 the use of remote manipulating devices operating over the top or through the 

 shield. These may take the simple form of strings actuating various pieces 



