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
  • G21F9/30—Processing
  • G21F9/301—Processing by fixation in stable solid media
  • G21F9/302—Processing by fixation in stable solid media in an inorganic matrix
• • 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
  • G21F9/04—Treating liquids
  • G21F9/06—Processing
  • G21F9/16—Processing by fixation in stable solid media
  • G21F9/162—Processing by fixation in stable solid media in an inorganic matrix, e.g. clays, zeolites
• • 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
  • G21F9/30—Processing
  • G21F9/301—Processing by fixation in stable solid media
  • G21F9/302—Processing by fixation in stable solid media in an inorganic matrix
  • G21F9/305—Glass or glass like matrix

Definitions

• the invention relates to a method for producing moldings containing highly radioactive waste materials, in which the waste materials and the glass, glass ceramic or ceramic matrix surrounding them are sintered by means of pressure and temperature.
• the glass state is an imbalance state, crystallization can be expected with long-term storage. According to previous knowledge, this begins with the macroscopically inhomogeneously distributed, heterogeneous inclusions, which act as nuclei. Crystallized areas with chemically different composition and fine structure are formed, which are arranged macroscopically inhomogeneous in the remaining glass phase. The highly active fission products are - in varying amounts - mainly concentrated in the crystallized areas. Because of their different composition and structure, these have different coefficients of thermal expansion, which leads to mechanical stresses in a glass block during final storage. In particular, the macroscopically inhomogeneous distribution of the different crystal areas, ultimately based on the macroscopically inhomogeneous distribution of the heterogeneous inclusions, increases the risk of cracking and brittle fracture in the glass block.
• the isostatic hot pressing of the capsule with the particle mixture is carried out at a pressure of at least 10 MPa and at a temperature of at least 973 K.
• glass such as borosilicate glass and phosphate glass, could also be used as the durable material.
• implementation examples with the latter materials have not been disclosed.
• the invention is based, in their properties to provide improved solidification products from highly radioactive waste and a glass, glass ceramic or ceramic matrix, in which a homogeneous distribution of the incorporated waste is ensured both during production and during long-term storage. It is also an object of the invention to provide a method with which intermediate and final storage moldings of such improved solidification products can be produced. In particular, mechanical stresses which involve the risk of crack formation and brittle fracture in the molded body should be avoided. The method should be technically simple and can be carried out with relatively little effort.
• the object is also achieved in a different way, namely in that the waste materials are first melted in a known manner in a glass, glass ceramic or ceramic matrix, then the solidified melt is mechanically comminuted or ground, the comminuted material or the The ground material is mixed and, without first enclosing it in a capsule, is either cold pressed directly at a pressure in the range from 50 MPa to 500 MPa and then sintered below the melting range of the matrix in the devitrification range at a temperature between 500 K and 800 K or at a pressure in the range from 10 to 50 MPa and a temperature in the range from 500 K to 800 K (except hot isostatic pressing).
• the sludge containing the waste materials thickened with glass, glass ceramic or ceramic powder, is compacted before drying in slip casting.
• the first solution also has the advantage that the glass, glass ceramic or ceramic waste mixture does not have to be melted, the processing temperatures can therefore be reduced to about two thirds of the temperatures required by melting technology, viscosity-related flow problems are avoided and crucible reactions and signs of segregation of the heterogeneous inclusions (segregation, inhomogeneous distribution) are reduced. In addition, the evaporation of highly active components, which was previously unavoidable when melting, is greatly reduced.
• radioactive powder can be introduced into the end products solidified by the process according to the invention.
• a simulated, denitrified waste solution of the following composition was prepared with inactive components:
• this solution was evaporated to dryness and the residue was ground to an average particle size of 10 to 50 ⁇ m (waste powder).
• powder fractions can also be used, but powder fractions that are too finely ground will not be used in order to rule out dust formation as far as possible.
• Example 1 To produce blocks with a diameter of 200 mm and a height of 150 mm by means of cold isostatic pressing in a flexible vessel, which is a condition for isostatic shaping, the procedure described in Example 1 was initially followed. The powder mixture was pressed at a pressure of approximately 500 MPa. The compacts were then sintered at 600 K to 800 K for 10 to 15 hours and then tempered. The desired macroscopic homogeneity was also achieved with these samples. The density was about 95% of the melt density.
• Example 1 The waste and glass powder mixture described in Example 1 was poured into a graphite mold with a graphite stamp and hot-pressed or pressure-sintered without prior cold pressing while simultaneously applying a pressure of 10 to 40 MPa at about 600 K (indirect heating). A treatment time of 10 minutes was sufficient for the blocks with a diameter of 20 mm and a height of 25 mm. A density of 97% of the solid density on the blocks was found, as well as the desired macroscopic homogeneity.

Landscapes

• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Processing Of Solid Wastes (AREA)
• Compositions Of Oxide Ceramics (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=6085400

Family Applications (1)

Country Status (4)

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Family Cites Families (5)

• 1979
  • 1979-11-08 DE DE19792945006 patent/DE2945006A1/de active Granted
• 1980
  • 1980-05-28 EP EP19800102963 patent/EP0028670B1/de not_active Expired
  • 1980-10-30 BR BR8007001A patent/BR8007001A/pt unknown
  • 1980-11-07 JP JP15673880A patent/JPS5682499A/ja active Pending

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