A particular rock is thought to be 234 million years old. If it contains 4.84 mg of 238U, how much 206 Pb should it contain? Assume 238U decays directly to 206PB with a half-life of 4.47 × 109 y.

Calculate the energy released in the a decay of 238 U. The atomic masses of 238 U, 234Th and He are 238.050784 u, 234.043593 u and 4.002602 u respectively.

A radioactive material has a decay constant of λ = 0.0586 yr-1. If it starts out with N0 = 9.03 × 1018 particles, how many (N) will be left after t = 407 years have gone by? Express your answer in scientific notation. (Example: 1.23e4)

In a nuclear reactor accident, the 137Cs (?1/2 = 30.2 years) nuclide is among the most problematic fission products. The energy released by the B-decay of 137Cs into the stable 137Ba is 1.17 MeV. a) Why is 137Cs considered as one of the most problematic fission products in a reactor accident? Give two reasons. b)Give two possible ways that 137Cs is produced in a pressurized water reactor. Write down the corresponding equation in each process. c)What is the percentage of a sample of 137Cs that will decay in one year? [Hint: the lifetime r is related to the half-life ?1/2 by r = ?1/2 ln2 .] d)If the radiation dose limit is 20 mSv per annum, what is the maximum amount of 137Cs that a 60-kg person can swallow without affecting his health?