Rules for Radiation Protection - Time, Distance and Shielding

Time - Because Total Exposure = Exposure Rate x Time

EXAMPLE: If the exposure rate = 225 milliroentgen (mR)/h, what
would be the total exposure after 36 minutes?

225 mR/h x 36/60 = 225 x 0.6 hours= 135 mR

Distance - Because The Photon Strength Decreases With Distance (Inverse Square Law Related)

EXAMPLE: If the intensity at 30 inches is 1.3 roentgen (R /min),
what will it be at 90 inches?

x = 302 ; x = 1.3 ( 1/9 ) ; x = 0.14 R/min
1.3 902

Shielding - Because The Unwanted Photons Are Absorbed By Protective Materials

Thickness Required

(1) at least .5 mm lead (Pb)
(2) 1.0 mm Pb recommended