The transport of radioactive samples must follow strict guidelines to ensure that the exposure is very low. A 100 mCi sample of 212Pb is placed at the centre of a cubical lead lined box, each side of which has a length of 30cm. Calculate the thickness of lead required to reduce the dose level at the surface of the box to 10mR per day at most. The half-life of 212Pb is 11 hours, and each gamma disintegration yields 0.24 MeV; the mass energy absorption coefficient for lead at this energy is 0.48 cm2g-1, and its density is 11.4 g.cm-3. (Make the simplest reasonable assumption you can, and provide a full explanation).
