The uranium isotope U-238 has a half-life of about 4.5 × 109 years. i) BOOKWORK Consider 1 mole (238 gm) of isotopically pure uranium U-238. Calculate its activity, and sketch a graph of the activity of the U-238 over the next ten billion years or so. Label the axes with appropriate numbers and units. Mark on the graph the half-life and the characteristic time of decay. ii) UNSEEN The uranium isotope U-238 decays through a chain of fourteen relatively short-lived radionuclides with half-lives of less than one million years before reaching a stable isotope of lead. Bricks, sand, tiles and other building materials typically have an activity of about 50 Bq per kg due to their primordial uranium content, the uranium made in stars and later present in the materials making up our rocks. Estimate the concentration of U-238 in building materials. First consider only the U-238, and then refine your estimate by taking the decay chain into account.

The uranium isotope U-238 has a half-life of about 4.5 × 109 years. i) BOOKWORK Consider 1 mole (238 gm) of isotopically pure uranium U-238. Calculate its activity, and sketch a graph of the activity of the U-238 over the next ten billion years or so. Label the axes with appropriate numbers and units. Mark on the graph the half-life and the characteristic time of decay. ii) UNSEEN The uranium isotope U-238 decays through a chain of fourteen relatively short-lived radionuclides with half-lives of less than one million years before reaching a stable isotope of lead. Bricks, sand, tiles and other building materials typically have an activity of about 50 Bq per kg due to their primordial uranium content, the uranium made in stars and later present in the materials making up our rocks. Estimate the concentration of U-238 in building materials. First consider only the U-238, and then refine your estimate by taking the decay chain into account.