How far down should nuclear waste be stored?

In the US it is stored on the power plant sites because no central repository has been authorised so far. In some countries like the UK and France, it is brought together on one site - Sellafield in the UK. But there is still no final long term store available.

There are different was to store the waste, at the plants where it was produced. Initial storage is usually in what is called a spent fuel pool, which is literally a large pool of water. This is done because the fuel is very hot and radioactive for a period while the isotopes with short half lives decay a bit. The period is usually more than five years.

After the time at the spent fuel pool, it may be removed to what are called dry casks. These are made of thick concrete and allow the materials to decay longer without a need for a constant supply of water.

Research is still being done in how to deal with nuclear waste.