646 



ADOLF F. VOIGT 



The provisional bulletin of the National Committee on Radiation 

 Protection (68) lists isotopes in three categories of danger, depending 

 largely upon half-life, but also on radiation type and energy and 

 biological behavior (Fig. 15). Thus if a laboratory is to be restricted 

 to the low level region of this table, no particularly different features 

 need be built in or provided other than good ventilation. At the 

 intermediate level more thought will have to be taken in the design 

 and for high level work special design is almost imperative. Since 

 this table is presented on the basis of internal radiation it does not 

 cover the danger from the external radiation of 7-ray emitters. The 

 dosage from the latter and the necessary shielding can be calculated 

 as shown earlier. 



Many operations in the usual tracer laboratory can be handled 

 with temporary shielding, preferably lead because of its density. 



Lead 



Fig. 16. A useful semiportable lead screen. 



Frequently size 2 X 4 X 8 in. lead bricks are used since these possess 

 a convenient weight (about 25 lb.) and shape. The main difficulty 

 with such bricks is that a 2 in. wall built with them is not very stable 

 and a 4 in. width is in many cases unnecessary. A semiportable lead 

 screen of L shape made of 1 in. lead bolted to an angle iron frame has 

 proved to be very useful for handting those isotopes whose 7 rays 

 have energies less than 0.7 m.e.v. (Fig. 16). 



The disposal of radioactive wastes is a serious problem. A large 

 number and several types of substances must be considered. One of 



