Patent Number: 050733052
Section: claims

1. A method of evacuating a container to a vacuum for use in treating radioactive wastes by placing the waste into the container, and evacuating, sealing off and thereafter compressing the container, the method comprising the steps of: placing the waste into the container,  forming over the waste a filter layer formed substantially entirely of particulate material fulfilling one of the following requirements:  (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: EQU D.gtoreq.(20/105).times.d-15;  thereafter aspirating a gas through the filter layer from thereabove to evacuate the container and sealing off and compressing the container. 2. A method as defined in claim 1 wherein a closure provided with an evacuating pipe is welded to the container after the filter layer has been formed, and the gas is aspirated through the evacuating pipe. 3. A method as defined in claim 2 wherein the container is sealed off by collapsing the evacuating pipe. 4. A method as defined in any one of claims 1 to 3 wherein the radioactive waste comprises a hull. 5. A method as defined in any one of claims 1 to 3 wherein the radioactive waste comprises a hull and a block of waste to be treated. 6. A method as defined in any one of claims 1 to 3 wherein the container is a stretchable or contractable container of the bellows type. 7. A method as defined in any one of claims 1 to 3 wherein the particulate material is a metal powder. 8. A method as defined in any one of claims 1 to 3 wherein the particulate material is a stainless steel powder. 9. A method as defined in any one of claims 1 to 3 wherein the particulate material is a ceramic powder.