The United States secretly sought Japan's support in 1972 to enable it to dump decommissioned nuclear reactors into the world's oceans under the London Convention, an international treaty being drawn up at the time.
Countries working on the wording of the pact wanted to specifically prohibit the dumping of radioactive waste at sea.
But Washington wanted to incorporate an exceptional clause in the case of decommissioned nuclear reactors.
It was apparent that the United States constructed nuclear reactors without having decided on disposal methods, forcing it to consider dumping them at sea after they were decommissioned.