TABLE 768.— THE MINIMUM THICKNESS OF LEAD RECOMMENDED 

 PROTECTION FOR VARIOUS INTENSITIES OF X-RAYS 



695 



FOR 



The National Bureau of Standards Handbook 41 on X-ray protection gives as the per- 

 missible dosage rate 0.3 r per week. On the basis of a 48-hour week of uniform exposure 

 the permissible dosage rate is 0.00625 r per hr (6.25 mr per hr). 



This booklet also gives safety rules for operating X-ray equipment and the thickness of 

 lead or concrete necessary for protection against X-ray tubes operated at various intensities. 



TABLE 769.— DISTANCE PROTECTION* 



* For reference, see footnote 237, p. 693. 



t These distances were computed by taking into account distance and air absorption. The air absorp- 

 tion was determined by assuming the radiation was monochromatic and of double the minimum wavelength 

 of the polychromatic radiation given off by the tube at the indicated potential. 



TABLE 770.— PRIMARY PROTECTIVE-BARRIER REQUIREMENTS FOR 10 



MILLIAMPERES AT THE PULSATING POTENTIALS* 



AND DISTANCES INDICATED t 



* Direct-current potentials require the order of 10 percent greater thickness than those given here for 

 pulsating potential. 



t For reference, see footnote 237, p. 693. 



TABLE 771.— PRIMARY PROTECTIVE-BARRIER REQUIREMENTS 

 400-KILOVOLTS PEAK PULSATING POTENTIAL 

 WITH REFLECTION TARGET* 



FOR 



Target 



distance 



ft 



5( 1.52 m) 

 10 ( 3.05 m) 



Lead thickness with target 

 current of — 



16.5 

 12.5 



3 ma 

 mm 



20 

 15.5 



5 ma 



22 

 17.0 



* For reference, see footnote 237, p. 693. 

 SMITHSONIAN PHYSICAL TABLES 



Target 



distance 



ft 



20 ( 6.1 m) 

 50(15.2 m) 



Lead thickness with target 

 current of — 



9.5 



5.5 



3 ma 

 mm 



11.5 

 8.0 



13.0 

 9.0 



