96 



RADIOISOTOPES IN BIOLOGY AND AGRICULTURE 



beta emitters, since plastic shields can be constructed for beakers, flasks, 

 and other apparatus. Figure 3-2 shows some typical shielded glassware. 

 The use of plastic sheets for barrier shielding with beta emitters offers 

 considerable advantage in that the operations are easily visible at all 

 times (Fig. 3-3). Lead or iron shielding is usually required for more than 

 1 mc of the energetic gamma emitters. Figure 3-4 shows a simple barrier 



Fig. 3-4. Simple barrior-and-niirror arraiigemont for haiulliug low-level gamma 

 emitters. Note simple pipette filler constructed from syringe and rubber tubing. 

 {Courtesy of Atomic Energy Commission.) 



for low levels, and Fig. 3-5 a more elaborate barrier for higher levels. 

 The bricks and remote-control pipetters are available commercially. 

 Measurements and provisions must be made to ensure that hazardous 

 levels of radiation do not pass between cracks in the shield or in any direc- 

 tion to the room above, through the desk top to the feet of the worker and 

 the room below, or to the room on the other side of a wall. 



Internal Hazards. Maximum Permissible Levels. A detailed review 

 of internal radioisotope hazards is available in National Bureau of Stand- 

 ards Handbook 52 (8). The problem of internal hazards is tremendously 

 complex, with very little guidance available of any sort. At least in the 

 external radiation problem there are records of numerous individuals who 

 have been exposed at low levels as part of their daily work and who have 



