Historically, it was planned to dump whole decommissioned nuclear
submarines at sea but this was subsequently prohibited by the London
Dumping Convention. Afloat storage has been demonstrated as a
cost-effective method of interim storage, but this had taken place under
the assumption that a permanent disposal facility would be available
early in the 21st century. As this is now highly unlikely, the MoD are
investigating alternative storage options for the medium term. These
submarines have had their weapons and nuclear fuel removed, and sites
for the land storage of the reactor compartment have to be found.
Nuclear waste, and perhaps more particularly nuclear waste from military
sources, is highly contentious. Proposed storage at Devonport resulted
in significant public outcry. Therefore, the MoD have undertaken public
consultation to reach an acceptable decision regarding the future
storage of nuclear submarines. See http://www.lancs.ac.uk/users/csec/isolus2/isolus-homepage.htm