Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/28—Treating solids
  • G21F9/34—Disposal of solid waste
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/28—Treating solids
  • G21F9/34—Disposal of solid waste
  • G21F9/36—Disposal of solid waste by packaging; by baling

Definitions

• the present invention relates to the hot pressing of particulate materials and containers for use in such processes.
• the hot pressing may be in a uniaxial pressing process or in an isostatic process.
• Furthermore in the ceramics field parts of machines can be machined from blocks of ceramic material produced in a hot pressing process from particulate starting materials.
• the container mainly achieves reduction in volume by axial compression and portions of the wall fold and form a series of radially outwardly extending flange-like formations.
• the present invention is directed towards the provision of containers for hot pressing of particulate materials in which a more advantageous final shape is achieved.
• a generally cylindrical, metal thin-walled container having a first end closed by a first end wall and a second end adapted to be closed by a lid after filling with particulate material, a side wall providing a reduced diameter portion intermediate the first and second ends, the side wall having generally cylindrical portions and radially inwardly directed portions extending therefrom to the reduced diameter portion, the radially inwardly directed portions being adjacent to one another, the side wall being such that, when the container has been filled, closed and subjected to hot isostatic pressing, the container undergoes significant axial compression of the container occurs and the radially inwardly directed portions closely approach or contact one another whereby the volume of the compressed particulate material closely approaches the volume of an imaginary cylindrical envelope in which the compressed container can be accommodated.
• the container may have two or more axially spaced reduced diameter portions, an important embodiment of the invention is one in which a single reduced diameter portion is provided.
• the side wall of the container between an end thereof and the reduced diameter portion is generally barrel-shaped and a smoothly curved profile is provided at the axial ends thereof.
• This feature is especially beneficial when the invention is applied with hot isostatic pressing as radially inward compression takes place in this zone.
• embodiments of the invention can also utilise hot uniaxial pressing and for this purpose, preferably, a restraining ring is provided around the reduced diameter portion and extending between the adjacent radially inwardly extending portions of the side wall.
• the relative dimensions of the portions of the container may be varied according to the scale of the embodiment used and the materials adopted. Generally it has been found that especially beneficial embodiments of the invention are ones where the radially inwardly directed portions extend radially a relatively large distance compared with the spacing therebetween. Preferably the radially inwardly extending portions extend radially to an extent of about 10% to 25% of the diameter of the container. Also preferably the spacing between adjacent radially inwardly extending portions is of the order of 5% of the diameter of the container.
• the radial dimension of the radially inwardly directed portions is in the range of 10% to 20% of the diameter of the container and the spacings between the radially inwardly directed portions is about 5% of the diameter of the container.
• the spacing between adjacent radially inwardly directed portions of the side wall is about 10% of the axial dimension of the generally cylindrical portions of the side wall leading to the radially inwardly directed portions.
• the side wall of the container has a smooth change of shape with a transition portion extending substantially in a plane transverse to the axis of the container between the reduced diameter portion and the adjacent portion of the container.
• a further advantageous feature which preferably also is utilised is the provision at one or preferably both of the ends of a configuration to permit axial displacement of the transverse end wall during the process.
• this is achieved by the side wall curving smoothly inwardly at the end of the container to terminate in an axially directed skirt directed away from the body of the container, the skirt having a diameter similar to the reduced diameter portion of the container and a flanged end wall or lid being utilised within the skirt, its flange also being outwardly directed and welded to the free end of the skirt, whereby the annular region at the end of the container around the outside of the skirt is displaced axially during the hot compression.
• the end wall having the lid is provided with an evacuation tube which is sealed e.g. by crimping when a vacuum is established.
• the invention also extends, in another aspect, to a method • of hot isostatic pressing of a particulate material in utilising a container in any one of the forms described above.
• a further requirement is that the compressed container reliably achieves a predictable shape in the process so as to facilitate subsequent handling and storage.
• FIG. 1 schematically illustrates a filled container embodying the present invention and before compression
• Fig. 2 is a schematic representation of the container of Fig. 1 after compression, but neither Fig. 1 nor 2 are drawn to scale or exactly to scale with one another
• Fig. 3 is a schematic cross-section through a second embodiment of container.
• the container 10 has a generally cylindrical side wall 11, a base wall 12 and a top cap or lid 13 from which an evacuation tube 14 extends.
• the side wall 11 has two barrel-shaped portions 15 and 16 which have a shallow convex structure in sectional view and a reduced diameter intermediate portion 17 connected to the major barrel-shaped portions by transition wall portions 18 which extend approximately at right angles to the axis of the container.
• the side wall 11 has a radially inwardly directed shoulder 19 leading to an axially extending skirt 20 which is outwardly directed and which is secured by a weld 21 to a corresponding skirt 22 of the base wall 12 and lid 13 as the case may be.
• the container Before the cap 13 is installed, the container is filled with particulate material 23 such as ceramic powder or a mixture of radioactive waste and synthetic rock precursor. As shown in Fig. 1 the evacuation tube 14 leads to a ceramic fibre filter 24 retained within the cap 13 by a perforated screen 25. This feature is very important where egress of solid powder material with the gas upon evacuation is to be avoided at all costs such as in the case of treating radioactive material.
• particulate material 23 such as ceramic powder or a mixture of radioactive waste and synthetic rock precursor.
• the tube 14 is crimped or sealed at 26 as shown in Fig. 2.
• Fig. 2 after hot isostatic pressing a substantial reduction in axial length occurs and there is also reduction in diameter.
• the transitional wall portions 18 closely approach or even touch one another and the base wall 12 and end cap 13 are axially displaced inwardly as deformation of the shoulder 19 occurs.
• Fig. 2 When the invention is applied to the formation of ceramic materials it will be apparent from Fig. 2 that two ceramic discs can be produced without complicated and expensive machining operations and with little loss of ceramic material.
• the container can be made o ' f mild steel although for other applications more expensive and higher performing alloys may be needed such as selected grades of stainless steel.
• FIG. 3 an alternative embodiment is described which is especially suitable for hot uniaxial pressing.
• the same reference numerals have been used in Fig. 3 to refer to elements corresponding to those of Figs. 1 and 2.
• Container 10 has a generally cylindrical side wall 11, a base wall 12 and a top 27 which includes a reinforced opening 28.
• Side wall 11 has four barrell-shaped portions 29, 30, 31 and 32 separated by reduced diameter intermediate portions 17.
• Portions 17 are connected to the barrell-shaped portions by transitional wall portions 18 which extend approximately at right angles to the axis of the container.
• Metal rings 33 are located around the container in the recesses defined by reduced diameter portions 17 and radially extending portions 18. These rings are useful when the container is to undergo hot uniaxial pressing, during which the restraining rings 33 prevent deflections occurring in the bellows and the resulting convolutions which are a cause of wasted space.

Landscapes

• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Physics & Mathematics (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Pressure Vessels And Lids Thereof (AREA)
• Powder Metallurgy (AREA)
• Lining Or Joining Of Plastics Or The Like (AREA)
• Press-Shaping Or Shaping Using Conveyers (AREA)
• Casting Or Compression Moulding Of Plastics Or The Like (AREA)

Applications Claiming Priority (3)

Publications (3)

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Country Status (5)

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• 1989
  • 1989-09-27 JP JP1510271A patent/JPH0742483B2/ja not_active Expired - Fee Related
  • 1989-09-27 AT AT89911001T patent/ATE127954T1/de not_active IP Right Cessation
  • 1989-09-27 WO PCT/AU1989/000417 patent/WO1990003648A1/fr active IP Right Grant
  • 1989-09-27 EP EP89911001A patent/EP0483139B1/fr not_active Expired - Lifetime
  • 1989-09-27 DE DE68924278T patent/DE68924278T2/de not_active Expired - Fee Related

Non-Patent Citations (1)

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