I've had a few questions regardng task 2 in the project. I here share the information I have given the groups that have asked:

Your task is to find out how much activity that is lost when producing 1 kg fuel (UO2 enriched to 4% U-235). Base your calculations on that.
Start your calculations from the last step; the enrichment. You start with natural uranium, i.e. 0.72% U-235 and the rest is U-238. Calculate how much U-238 you need to remove in order to have 4% U-235 (or,to use numbers, 40 gram 235UO2). Once you know the amount of U-238 you can calculate the activity of U-238 and the activity of U-235.

Since the uranium ore has been there for a very long time you can assume that secular equilibrium prevails. Take a look at the decay chains of U-238 and U-235. All radioactive daughters need be removed in the purification/mining process.

I hope those hints helps