PURPOSE: To prevent a container for radioactive waste products from breakage due to a hydraulic pressure applied upon dumping even if the container is deformed by a method wherein a drum filled with the radioactive waste products is carried to an area of the ocean to dump it in a condition that it is hang within a hold and is dumped into the ocean after concrete is poured into the drum can.

CONSTITUTION: A plurality of holds 2 capable of releasably hanging drum filled with radioactive waste products are provided longitudinally in a hull 10. The hold 2 is not provided with a bottom plate and is constituted so that the drum is dumped into the sea immediately when the hanging of the drum is released. A ready mixed concrete plant 7 capable of pouring ready mixed concrete into the drum is equipped on the hull so that the immediate dumping may be effected at an area of the ocean to dump the drum after the ready mixed concrete is poured into it. Accordingly, even if the dumped drum is deformed by a hydraulic pressure, it will not be broken and a sure dumping may be effected because the concrete in the drum is still a fluid body.