In theory, sure. In practice, complex technological and political issues remain - apparent by the fact that no country has solved the issue yet. You apparently

In theory, sure. In practice, complex technological and political issues remain - apparent by the fact that no country has solved the issue yet. You apparently stable salt mines start leaking. Locals don't like having toxic stuff buried below them. Other countries dislike that you dump nuclear waste in the middle of the Atlantic. Digging deep becomes too expensive.