Ocean disposal of heat generating radioactive waste backfilling requirements

This report describes the backfilling requirements arising from the disposal of HGW in deep ocean sediments. The two disposal options considered are the drilled emplacement method and the free fall penetrator method. The materials best suited for filling the voids in the two options are reviewed. Candidate materials are selected following a study of the property requirements of each backfill. Placement methods for the candidate materials, as well as the means available for verifying the quality of the filling, are presented. Finally, an assessment of the overall feasibility of each placement method is given. The main conclusion is that, although the proposed methods are feasible, further work is necessary to test in inactive trials each of the proposed filling methods. Moreover, it is difficult to envisage how two of the backfilling operations in drilled emplacement option can be verified by non destructive methods. (author)