A few issues with the paper.
1) you should probably mention that the chances of the stored waste reaching the critical mass and starting a spontanious fission reaction are very low, but one single occurance will cause an incident of equal destruction to Chernobyl.
2) The First paragraph transition feels a bit too redundant. Try altering that transition a bit so it reads better.
3) You state that radioavtive elements have a half life of 10000 years. This is flat out wrong. Radioactive elements have wildly fluxuating half lives from under a second for very unstable atoms, or from the typical hours to millions of years depending on the specific element and decay method.

Otherwise it is pretty good and fits the rubric as far as I can see.