Q. The immediate environment of a reactor contains a large flux of 10 MeV gamma rays. Resolve the thickness of lead required to reduce the intensity by a factor of 1012. Assume the mass absorption coefficient of Pb for 10 MeV photons is m/r = 0.06 cm2/g. The density of Pb is 11350 kg/m3 (or 11.35 g/cm3).