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).

Please see the sticky at the top of this forum. We will not do your work for you. However, if you want to show us what you did we can critique it.