The front of a 6-cm aluminum slab is located 2 m from a 2.96×1011 Bq 137Cs point source, as shown in Fig. 15.13. The back of a parallel thick shield, which completely absorbs direct radiation, is 1.7 m from the source. The shield has a cylindrical aperture of area 1 cm2 with the source on its axis.
(a) Calculate the exposure rate at a point P 2.8 m from the source on the cylindrical axis. Answer 85 mR/hr
(b) What is the exposure rate at P with the thick shield removed? 220 mR/hr