Uranium used in nuclear power is typically mined and enriched to concentrate U-235. A by-product of the enrichment process is a large quantity of more pure U-238. The amount of U-238 tails is estimated to be over 1 million tonnes worldwide. The gamma ray emitting daughters products of U-238 pose a radiological hazard.

1. Draw out the decay chain and identify daughters that will build up in sufficient quantities to reach secular equilibrium with U-238 within 5 years. Consult your text and class notes on the path of this decay chain.
2. Write the decay reaction equation for each decay step.
3. Calculate the Q value for each decay step.
4. How many half lives and time are necessary for these daughters to build up to 99% of U-238 to reach secular equilibrium?
5. What is the total activity (in units of Curies) of a 1 million tonne pile of U-238 that has been sitting for 5 years? (Recall that the total is the sum of all activities of parent and daughters in equilibrium).