Abstract: A method of evacuating a container to a vacuum for use in treating radioactive wastes by placing the waste into the container, evacuating, sealing off and thereafter compressing the container, the method being characterized by placing the waste into the container, forming over the waste a filter layer of particulate material fulfilling one of the following requirements: and sealing off and compressing the container.(1) A layer having a thickness of at least 5 mm and formed of a particulate material not smaller than 40 .mu.m to less than 105 .mu.m in mean particle size;(2) A layer having a thickness of D in mm and formed of a particulate material not smaller than 105 .mu.m to not greater than 210 .mu.m in mean particle size d in .mu.m, the thickness D and the mean particle size d having the relationship represented by:D.gtoreq.(20/105).times.d-15;and thereafter aspirating a gas through the filter layer from thereabove to evacuate the container and sealing off and compressing the container.

Abstract: A method of compacting radioactive metal wastes comprising enclosing the radioactive metal waste in vacuo in a capsule, placing the capsule into a pressure container, and subjecting the capsule to an increased pressure at a high temperature to compact the waste. The compacting treatment is conducted in a state in which the atmosphere within the pressure container contains water molecules in an amount, in terms of the total weight W (g) thereof, the amount being preferably in the range of:1.3.times.10.sup.-6 .times.V.ltoreq.Wwherein V (cm.sup.3) is the volume of the compacting space in the pressure container. Alternatively, an oxide coating is formed on the outer surface of the capsule before the capsule is placed into the pressure container, or the formation of the oxide coating is followed by the compacting treatment conducted in the above-mentioned state.